Rich Text Editor FileDetailed correlation and astronomical forcing across the Upper Maastrichtian...

7/27/2019 Rich Text Editor FileDetailed correlation and astronomical forcing across the Upper Maastrichtian succession from t

1/24

Detailed correlation and astronomical forcing across the Upper Maastrichtian successionfrom the Basque Basin.

Jaume Dinars-Turell(1), Victoriano Pujalte(2), Kristalina Stoykova(3), Javier Elorza(4)

(1) Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, I-00143 Rome, Italy.

(2) Department of Stratigraphy and Paleontology, Fac. Science and Technology, University of theBasque Country UPV/EHU, PO Box 644, E-48080 Bilbao, Spain

(3) Department of Paleontology and Stratigraphy, Geological Institute, Bulgarian Academy ofScience, BG-1113 Sofia, Bulgaria.

(4) Department of Mineralogy and Petrology, Fac. Science and Technology, University of theBasque Country UPV/EHU, PO Box 644, E-48080 Bilbao, Spain.

Abstract

A comprehensive integrated cyclo-magnetostratigraphic analysis and calcareous nannofossilstudy for the Upper Maastrichtian hemipelagic sucession from three sections of the BasqueBasin (Zumaia, Sopelana and Hendaia) is presented. Correlation between sections is achievedat bed-by-bed scale through careful analysis of the lithologic stacking pattern and significantsedimentary features. An available high-resolution carbonate proxy record spanning 64 m ofsection below the K/Pg (Cretaceous/Paleogene) boundary at Zumaia, containing 72 precession-related limestone-marl couplets, is used for spectral analysis. The continuous wavelet spectrumhelps to determine and visualize the orbital forcing at both the short (~100-ky) and long (405-ky)eccentricity band. Bandpass Gaussian filters on the carbonate record are used to extract therelevant periodicities and a cycle numbering scheme starting at the K/Pg boundary is provided.The full hierarchy of precession cycles and eccentricity-related bundles is then extended toward

the base of the studied section that contains a total of 33 short eccentricity-related bundles,therefore spanning more than 3 My time. Unambiguous determination of chron C31r/C31nboundary (estimated to occur at ~3.08 Ma below the K/Pg boundary) in the lower part of thesuccession is achieved in the three studied sections, while the C30n/C29r reversal could not bedetermined due to a pervasive reverse magnetization acting on the purplish lithologies from theupper part of the succession. Relevant calcareous plankton bioevents can be accurately placedon the cyclo-magnetostratigraphic template. The cyclostratigraphic framework further allows

estimating the duration of previously defined sea-level related 3rd-order depositional sequencesin the basin, that appear strongly paced by the long term 1.2 My obliquity amplitude modulatingcycle. This is an outstanding feature in the Maastrichtian greenhouse period in which continentalice sheets are expected to be either ephemeral or non-existent and is an aspect that deserves

further attention.

Keywords

Milankovitch, magnetostratigraphy, calcareous nannofossils, cyclostratigraphy, depositionalsequences

Correlacin detallada y control orbital de la sucesin del Maastrichtiense Superior de la CuencaVasca

Resumen

Se presenta un estudio exhaustivo ciclo-magnetostratigrfico y de nanofsiles calcreos de tressecciones de la sucesin hemipelgica del Maastrichtiense Superior de la Cuenca Vasca(Zumaia, Sopelana y Hendaia). La correlacin entre secciones se realiza capa a capa medianteun anlisis minucioso del patrn del apilamiento litolgico y detalles sedimentarios. Para el


2/24

anlisis espectral se utiliza un registro de carbonato de alta resolucin de un intervalo de 64 mdebajo del lmite K/Pg (Cretcico/Palegeno), disponible en Zumaia, que contine 72 paresmarga-caliza relacionados con el ciclo de precesin. El espectro continuo de ondas pequeasayuda a determinar y visualizar el control orbital en las bandas de la excentricidad corta (~100-ky) y larga (405-ky). Se han usado filtros gausianos pasabanda sobre el registro de carbonatopara extraer las periodicidades relevantes y se aporta un esquema de numeracin de ciclos quese inicia en el lmite K/Pg. A continuacin, la jerarqua completa de ciclos de precesin ypaquetes de la excentricidad se ha extendido hacia la base de la sucesin estudiada, que

contiene un total de 33 paquetes relacionados con la excentricidad corta y en consecuencia unaduracin superior a los 3 My. El lmite de cron C31r/C31n (posicin estimada a ~3.08 My debajodel K/Pg) se ha determinado de forma inequvoca en la parte inferior de la sucesin en las tressecciones estudiadas, pero no ha sido posible determinar el lmite de cron C30n/C29r debido auna remagnetizacin inversa generalizada en las litologas rojizas de la parte superior de lasucesin. Los bioeventos relevantes del plankton calcreo pueden posicionarse con precisinen el modelo ciclo-magnetostratigrfico. Adems, la plantilla ciclostratigrfica permite estimar la

duracin de las secuencias deposicionales de 3er-orden relacionadas con variaciones del niveldel mar que han sido definidas con anterioridad en la cuenca, y que parecen gobernadas por elciclo de 1.2 My de la oblicuidad de modulacin de la amplitud. Esto representa un hechodestacado para el periodo invernadero del Maastrichtiense en el que se cree que los casquetes

glaciares continentales fueron efmeros o no existentes, y es un aspecto que necesita serestudiado con ms profundidad.

Palabras clave

Milankovitch, magnetostratigrafa, nanofsiles calcareos, ciclostratigrafa, secuenciasdeposicionales

Versin abreviada en castellano.

Introduccin y metodologa

La correlacin astronmica o tuning de secuencias que presentan ciclos litolgicos consoluciones orbitales proporcionadas por los astrnomos ha conducido a una resolucin yprecisin sin precedentes en el registro geolgico a lo largo de gran parte del Cenozoico. Parael Palegeno, la correlacin astronmica resulta complicada a pesar de la existencia desoluciones numricas modernas para el Sistema Solar (Varadi et al., 2003; Laskar et al., 2004),debido a imprecisiones y limitaciones inherentes al comportamiento catico del Sistema Solar ya un pobre control con edades radiomtricas. Las sucesiones hemipelgicas paleocenas de laCuenca Vasca han contribuido a un vivo debate sobre la extensin de la calibracinastronmica para esta poca que an no ha sido resuelta satisfactoriamente (Dinars-Turell etal., 2003, 2007, 2010, 2012; Westerhold et al., 2008, 2011; Kuiper et al., 2008; Hilgen et al.,

2010). Los primeros intentos de correlacin astronmica para el Cretcico considerando el lmiteK/Pg y algunos crones magnticos se basaron en duraciones relativas (e.g. Herbert et al. 1995,Herbert, 1999). Solo recientemente el Maastrichtiense ha sido calibrado astronmicamenteusando soluciones modernas (Husson et al., 2011; Thibault et al., 2012). En este trabajopresentamos el primer estudio detallado integrado ciclo- magnetostratigrfico y de nanofsilescalcreos para la sucesin del Maastrichtiense Superior de la Cuenca Vasca.

El Maastrichtiense de la Cuenca Vasca est expuesto en diferentes afloramientos a lo largo dela costa que han sido clsicamente estudiados principalmente por su contenido biostratigrfico(Fig. 1). El origen orbital de las alternancias marga-caliza tambin ha sido estudiado conanterioridad (Mount and Ward, 1986; Ten Kate and Sprenger, 1993). Recientemente un estudiointegrado de plankton calcreo y magnetostratigrafa ha sido publicado para la seccin deZumaia aunque no presenta un log litolgico detallado ni se ha abordado la ciclicidad (Prez-Rodrguez et al., 2012). La mayor parte del Maastrichtiense de la Cuenca Vasca consiste en unaalternancia de margas y carbonatos hemipelgicos, y en algunas secciones, turbiditasfinas/medias (cm a dm de espesor). Atendiendo la proporcin variable de esas litologas, se hizo


3/24

una subdivisin litoestratigrfica formal en miembros (Miembros I a V de Ward, 1988; Ward yKennedy, 1993) y una informal ms detallada en unidades (unidades 2 a 12 de Wiedmann,1988) (Fig. 2). Las variaciones litolgicas de escala mayor a lo largo de la sucesin tambin hansido interpretadas por autores ms recientes en trminos de estratigrafa secuencial (Pujalte etal., 1995; Baceta et al., 2004), que han reconocido 3 secuencias deposicionales de 3er orden.En este trabajo las tres secuencias deposicionales se han renombrado de ms antigua a msmoderna como Ma-1, Ma-2 and Ma-Da respectivamente (Fig. 2).

Este trabajo se centra en el intervalo que comprende las unidades 612, que engloba elMaastrichtiense Superior, a lo largo de tres secciones (Zumaia, Sopelana I y Hendaia) (Fig. 1,Fig. 3). Un anlisis cuidadoso en las secciones ha permitido una correlacin capa a capa que hapermitido establecer una cronologa astronmica para el intervalo estudiado. Un registro decarbonato de alta resolucin para las unidades 10-12 en Zumaia (Ten Kate and Sprenger, 1993)se ha utilizado para nuevos anlisis espectrales y determinar las periodicidades, las fases y lacorrelacin astronmica correspondientes. La arquitectura deposicional y el contaje de los paresmarga-caliza atribuidos a la precesin astronmica (~21 ky) y los ciclos de excentricidad (~100ky) (grupos de 46 pares marga-caliza) se han establecido para todo el interval estudiado. Elanclaje con la solucin astronmica se ha basado en la presencia de los ciclos de excentricidadde 405 ky y la edad del lmite K/Pg. Asimismo se ha realizado un estudio magnetostratigrfico

para intervalos seleccionados en Zumaia y Sopelana I y hemos realizado un estudio de altaresolucin de nanofsiles calcreos en Sopelana I que no dispona de estos datos.

Para el estudio magnetostratigrfico se han seleccionado las partes relevantes en las diversassecciones estudiadas (Fig. 2). El muestreo se ha realizado a una resolucin mnima de unamuestra por par litolgico e incluye la inversin del cron C30n/29r alrededor del lmite de lasunidades 11/12 en las secciones de Zumaia (16 capas), Sopelana I (43 capas) y Hendaia (9capas), y la inversin C31r/C31n en la unidad 6 en Zumaia (33 capas), Sopelana I (13 capas) yHendaia (10 capas). Para el estudio de los nanofsiles de la seccin de Sopelana I se hananalizado 76 muestras desde el lmite K/Pg hasta la parte inferior de la Unidad 6 (~67 m deespesor) y se ha adoptado el esquema de biozonas UC de Burnett (1998) (Fig. 4).

Resultados y discusin

A continuacin se describen los resultados integrados para las secciones principales de Zumaiay Sopelana I en orden estratigrfico inverso siguiendo las unidades de Wiedmann (1988) yseparadamente al final los resultados de la seccin de Hendaia.

Las unidades 1210 afloran en condiciones excepcionales en los acantilados de Punta Aitzgorrien Zumaia (Fig. 5). Se reconocen un total de 72 ciclos con un espesor aproximado de 0.9 m enel intervalo considerado. Un estudio previo de alta resolucin sobre el registro de carbonatoclcico demostr que efectivamente los pares litolgicos en el Maastrichtiense representan

ciclos astronmicos de precisin de ~21-ky de duracin. El registro de carbonato de Ten Kateand Sprenger ( 1993) se ha usado para extraer las periodicidades de los ciclos de excentricidadcorta (~100-ky) y larga (~405-ky) a travs del anlisis espectral. En el diagrama de Fourierstandard se reconocen tres periodicicades (Fig. 6). Una banda con periodos de 0.7-0.95 m estasociada al par litlogico relacionado con la precesin. Un periodo a 4.1 m se relaciona con laexcentricidad corta de 100-ky mientras que el periodo a 17 m se puede asociar a laexcentricidad larga de 405-ky. La Figura 7a muestra los ciclos de precesin (ciclos Pk1 to Pk72)

y la distribucin de los ciclos de excentricidad corta y larga extrados a partir de filtrosgaussianos correspondientes. Los ciclos de 405-ky se han nombrado Ma4051, Ma4052 and

Ma4053 mientras que los 17 ciclos de excentricidad de 100-ky deducidos a lo largo de las

unidades1012 se han nombrado E1-E17. El estudio magnetostratigrfico (Fig. 8) realizado enla Unidad 11 demuestra que las litologias rojizas de este intervalo presentan unaremagnetizacin compleja por lo que no es posible establecer la posicin de la inversin decrones C20n/C29r.


4/24

Los ciclos PK1 a PK72 tambin pueden distinguirse en la seccin de Sopelna I tras resolver

algunas fallas (Fig. 9). Los resultados magnetostratigrficos en la parte superior de la seccin alo largo de las unidades 1210 indican que tambin existe una remagnetizacin generalizada(Fig. 10) por lo que no ha sido posible reproducir los resultados de estudios anteriores (Mary etal.,1991; Moreau et al. 1994). El estudio de nanofsiles de la seccin de Sopelana indica queestos son abundantes y representados por asociaciones muy diversificadas con unapreservacin de buena a muy buena (Plate I). Los bioeventos ms importantes se representanen la Fig. 10 y la totalidad de los datos en la Tabla 1.

El contaje de ciclos para las unidades 98 es relativamente fcil. La Fig. 11 ilustra este intervaloen las secciones de Zumaia y Sopelana I. Se observan 32 pares litolgicos (ciclos de precesinPK73 to PK104) que comprenden 6 ciclos relacionados con la excentriciadad nombrados E18 a

E23.La Unidad 7 es relativamente margosa y est mejor expuesta en Zumaia (Fig. 12). Laobservacin de los ciclos de excentricidad se realiza sin problemas aunque el ciclo E26 esmenos claro. La Unidad 6 se caracteriza por un tramo carbonatado de unos 15 m de espesor conun intervalo margoso pronunciado de 1.2 m hacia la mitad que se ha denominado con el moteEscaln (Fig. 13). Aunque las capas margosas del par litolgico no estn muy desarrollados sehan podido contar 24 ciclos de precesin y 4-5 ciclos de excentricidad en la Unidad 6. El estudiomagnetostratigrfico de esta unidad (Fig. 14) ha permitido localizar la inversin C31r/C30n en elciclo de precisin PE201. En Sopelana I, tambin es posible observar los 24 pares litlogicos y

localizar la inversin C31r/C30n aunque existe una falla que separa dos bloques (Fig. 15).

En Hendaia la sucesin del Cretcico Superior aflora a lo largo de la Pointe Sainte-Anne endiversos bloques separados por fallas (Fig. 16) y se han podido distinguir todas las unidadeslitolgicas 612. El estudio magnetostratigrfico en las unidades 1112 indica unamagnetizacin secundarias que no permite establecer la magnetostratigrafia al igual que enZumaia y Sopelana (Fig. 17). En cambio, la Unidad 6 que se ha estudiado en las seccionesdenominadas Hendaia E y Hendaia W (Fig. 18 and 19) permite observar y contar sinambigedades los ciclos de precesin de esta unidad y confirmar la localizacin de la inversin

C31r/C31n.

El lmite de cron C31r/C31n (posicin estimada a ~3.08 My debajo del K/Pg) se ha determinadode forma inequvoca en la parte inferior de la sucesin en las tres secciones estudiadas, pero noha sido posible determinar el lmite de cron C30n/C29r debido a una remagnetizacin inversageneralizada en las litologas rojizas de la parte superior de la sucesin. Los bioeventosrelevantes del plankton calcreo pueden posicionarse con precisin en el modelo ciclo-magnetostratigrfico. Adems, la plantilla ciclostratigrfica (Fig. 20) permite estimar la duracin

de las secuencias deposicionales de 3er-orden relacionadas con variaciones del nivel del marque han sido definidas con anterioridad en la cuenca, y que parecen gobernadas por el ciclo de1.2 My de la oblicuidad de modulacin de la amplitud.

Introduction

The study of rhythmic sedimentary successions from deep sea records and on land outcrops,where a full hierarchy of cyclic stacking patterns have been demonstrated to originate from theastronomical climate forcing on the sedimentary depositional environment, has been central inthe development of the modern Geological Time Scale. Astronomical tuning of these sequences

to accurate orbital solutions provided by the astronomers has led to an unprecedented accuracy,resolution and stability in the geological record along the earliest part of the Cenozoic that hasbenefitted from methodological enhancements and improved astronomical models in the recentyears. Milankovitch climate cyclicity tied to magnetic polarity stratigraphy is the backbone of therecent geological past (Kent, 1999). Achievement on this integrated effort was the completion ofan astronomical time scale for the Neogene (Astronomically Tuned Neogene Time Scale,


5/24

ATNTS2004; Lourens et al., 2004) which was incorporated in the GTS2004 Geological TimeScale (Gradstein et al., 2004). Tuning the Palaeogene has become more challenging despitenew full numerical solutions for the Solar System (Varadi et al., 2003; Laskar et al., 2004), due touncertainties and limitations inherent to the chaotic behaviour of the Solar System and poorradiometric age control. The Paleocene hemipelagic successions from the Basque Basin, and inparticular Zumaia, has contributed to a warm debate on the extension of the astronomical timescale for this epoch (Dinars-Turell, et al., 2003, 2007, 2010, 2012; Westerhold et al., 2008;Kuiper et al., 2008; Hilgen et al., 2010) which is still not fully resolved. This is mainly due to the

existence of the so called Eocene gap in the astronomical time scale, implying that differentoptions had to be proposed for the Paleocene, the inconsistencies in cycle recognition along thestudied records (Hilgen et al., 2010) and the limitation of the orbital solutions. Recent efforts oncyclic deep sea records (Westerhold et al., 2012) have shed some controversial light toward thecalibration of the early Paleogene. In any case, it has become clear that very long geologicalrecords are necessary to overcome some of the inherent limitations on the astronomical solutionsfor the geological time intervals older than ~54 Ma that could potentially provide crucialinformation for the astronomers. Earlier attempts to orbital correlations on Cretaceoussuccessions linked to a temporal framework including the K/Pg boundary and some magneticchrons have focussed mostly on elapsed time (e.g. Herbert et al. 1995; Herbert, 1999). Onlyrecently the entire Maastrichtian from deep sea records has been tuned to modern astronomical

solutions (Husson et al., 2011, Thibault et al., 2012). Here, we present a first comprehensiveintegrated cyclo- and magnetostratigraphic analysis and calcareous nannofossil study for theUpper Maastrichtian succession in the Basque Basin.

Material and methods

Studied sections and previous works

The Basque Basin was a deep-water interplate trough (Flysch trough) flanked to the north(Aquitania), south (Iberia) and east sides by shallow shelf areas, and openened to the west intothe Bay of Biscay (Fig. 1). Throughout the Late Maastrichtian and Paleocene, the seatransgressed the flanking shallow areas, leading to the development of extensive ramps orcarbonate platforms (Plaziat, 1981; Pujalte et al., 1994; Baceta, et al., 2004). That overalltransgression also made it difficult for coarse-grained siliciclastics to reach the deep trough,which became the site of a hemipelagic limestone/marl type of sedimentation, with turbiditesbeing mostly restricted to the base of slope area (Fig. 1).

The Maastrichtian succession from the Basque Basin crops out best along different coastalexposures (i.e., Zumaia and Sopelana separated about 60 km ) that have been classicallystudied mainly for their biostratigraphic content (ammonites, inoceramids and calcareousplankton; Herm, 1963; Lamolda, 1985; Ward et al., 1986, 1991; Wiedmann, 1988; MacLeod andOrr, 1993; Ward and Kennedy, 1993; Burnett et al., 1992; MacLeod, 1994; Lamolda andGorostidi, 1994; von Hillebrandt, 1965; Arz and Molina, 2002). Other studies include carbon andoxygen stable isotopes (Mount and Ward, 1986; Gmez-Alday et al., 2004, 2008; Paul andLamolda, 2007). The orbital origin of the limestone/marl alternations have been also explored(Mount and Ward, 1986; Ten Kate and Sprenger, 1993). Magnetostratigraphy for the UpperMaastrichtian had only been published for the Sopelana section (Mary et al., 1991). Morerecently, a multidisciplinary calcareous plankton and magnetostratigraphic study has beenperformed for the Maastrichtian in the Zumaia section (Prez-Rodrguez et al., 2012) but nodetailed lithological log or cycle counting was provided.

The bulk of the Maastrichtian strata corresponds to the Zumaia-Algorri Formation (Mathey, 1982)and consist of alternations of hemipelagic limestones and marls and subordinated clay-shalesand, in some sections, thin- to medium-bedded (cm to dm thick) turbidites. Based on the variableproportion of these lithologies, a lithostratigraphic subdivision in formal members (Member I to Vof Ward, 1988; Ward and Kenned , 1993 and more detailed informal litholo ical units units 2 to


6/24

12 of Wiedmann, 1988) have been commonly used (Fig. 2). These lithological units cangenerally be recognized in widely separated sections, from Sopelana in the West, to Bidart in theEast (Fig. 1), although individual unit thickness, rock color and number and thickness of turbiditebeds are variable. The Maastrichtian succession at Zumaia is the thickest (about 240 m, Fig. 2)and can be taken as representative. The oldest member corresponds to limestone-marlalternations of pale grey color (Member I) that has been subdivided into 4 units (units 2 to 5)based on their relative carbonate content, thickness and frequency of turbidite beds and overallerosion expression in the field. Member II (Unit 6) is dominated by pale limestones that contains

a conspicuous darker meter-scale marl bed in i ts middle part that has been colloquially termedEscaln (= step or indentation). According to the most recent integrated calcareousnannoplankton and magnetostratigraphic study for the Zumaia section (Prez-Rodrguez et al.,2012) the Lower/Upper Maastrichtian boundary interval is located in Unit 6. Member II is overlainby a marlstone unit (Member III) distinctive because of its reddish to chocolate-brown color. Theoverlying unit (Member IV) is formed by limestone-marlstone rhytmites and is subdivided into 4subunits: a relatively carbonatic-rich pale gray units 8-9, followed by reddish marly-rich unit 10and relatively carbonate-rich Unit 11. The last Maastrichtian Member (V) is a deep purplish marlyunit (Unit 12). Later authors interpreted these large-scale alternations in terms of sequence

stratigraphy, recognizing 3 successive 3rd-order depositional sequences in the upperMaastrichtian-lowest Danian interval (Fig. 2). Thus, Pujalte et al. (1995), based on the classic

model of Posamentier and Vail (1988), attributed the marl-dominated units to the low-stand fansystem tract (LSF) and the limestone-marl rhythmic units to the low-stand wedge and high-stand

system tracts (LSW + HST) within the 3rd-order despositional sequence (DS-1, DS-2.1 and DS-2.2, from older to younger). Baceta et al. (2004), although agreeing in their characterization,renamed these sequences as Ma-1, Ma-2 and Ma-Da and, following a more conservativeapproach, did not subdivide them into system tracts. We have renamed these sequencesinverting the numbering (UMa-2, UMa-1 and UMa-Da, from older to younger), thus allowing forpotential extension into older ages and try to reconcile previous interpretations by simply usinglow- and high-stand system tracts (Fig. 2). Despite the different terminology, the rationale for bothinterpretations is similar. In short, marl-dominated units were assigned to periods of relative low

sea-level arguing that during these intervals the shoreline would be nearer, making it easier forthe fine-grained clastics to reach the deep basin (see Units 7, 10 and 12 in Fig. 2). Conversely, ahigh sea-level would hinder the incoming of clastics and facilitate the accumulation ofhemipelagic limestones that characterize units 9-8, and 11, and also the lower part of the Daniansuccession (Fig. 2).

In this study we have focused on the interval comprising units 6 to 12 that encompass the UpperMaastrichtian along 3 sections (Zumaia, Sopelana I, and Hendaia) (Fig. 1). The Upper

Maastrichtian Zumaia (base of section 43o1756.31N/2o1609.03W) and the Sopelana I (base

43o2319.06N/2o5939.29W) coastal-cliff sections constitute the primary studied sections (Fig.3). The Upper Maastrichtian in Zumaia (units 612, ~150 m) is formed by limestone-marl

alternations including hundreds of thin bedded turbidites. The Upper Maastrichtian succession atSopelana I (~70 m) has the advantage that lacks interbedded turbidites. As an inconvenience, itis relatively tectonized and not straightforward to follow in detail at first glance, despite the mainlithological units can be identified (Fig. 3b). Nevertheless, careful observations and resolution ofsome complex faults allow a proper recognition and a bed-by-bed correlation to the precessioncycles identified at Zumaia (see below). Zumaia, besides been the thickest section, represents akey area in the stratigraphic analysis of the Upper Cretaceous and Paleocene. Extensiveintegrated high-resolution chronostratigraphic studies including astronomical tuning have beenperformed for the Paleocene part (Dinars-Turell et al., 2002, 2003, 2007, 2010, 2012; Kuiper etal., 2008) and the section hosts the two internal Paleocene Global Standards Section and Points(GSSPs) for the base of the Thanetian and Selandian stages (Schmitz et al., 2011) and anauxiliary K/Pg boundary (Molina et al., 2009). Moreover, a high-resolution carbonate record forthe Upper Maastrichtian units 1012 had been previously published and analyzed forastronomical purposes (Ten Kate and Sprenger, 1993) and therefore it was rational to extent theastronomical observations to older ages and potentially achieve a long and full astronomicaltuning from land-based sections comprising the Maastrichtian that, on the other hand, has


7/24

recently been astronomically tuned from deep-sea records (Husson et al., 2011, Thibault et al.,2012). The Zumaia bulk carbonate record from units 10 to 12 from Ten Kate and Sprenger (1993)has been used for new spectral analysis herein. Magnetostratigraphic data from Zumaia had notbeen available until recently, but with limited success due to a pervasive remagnetization in thereddish lithologies (Prez-Rodrguez et al., 2012) whereas an apparent reasonablemagnetostratigraphy down to chron C31r was established in the Sopelana I section (Mary et al.,1991) although complex magnetization mechanisms were invoked for the section (Moreau et al.,1994). Consequently, we have undertaken a paleomagnetic study at Sopelana I and Zumaia to

reproduce the earlier magnetostratigraphy on an adequate cyclostratigraphic framework.Furthermore, an extensive high-resolution calcareous nannofossil biostratigraphy has beenproduced for the first time along the Sopelana I section.

Additionally, we have explored other Upper Maastrichtian sections at Hendaia that presentcertain lithologic particularities. The Maastrichtian outcrops along the coastal-cliffs of PointeSainte-Anne near Hendaia have been targeted along relevant intervals for magnetostratigraphicpurposes after recognition of the standard lithologic units and cycle identification. Three nearby

outcrops have been considered: the Hendaia E section (3o2256.36N/0o4516.97W) for the

C31r/C31n reversal in unit 6 and the Hendaia N section (43o2303.00N/1o4509.64) for theC30n/C29r chron reversal close to the contact of units 11 and 12. Some additional observationsin unit 6 have been achieved in the Hendaia W outcrop.

Magnetostratigraphy

Samples for paleomagnetic analysis where taken as hand-samples and oriented in situ with amagnetic compass and subsequently standard cubic specimens were cut in the laboratory foranalysis. We aim at a high-resolution chronostratigraphic framework so sampling has beenperformed at a lithological couplet level (~21 ky resolution). Only relevant intervals have beensampled for magnetostratigraphic purposes along the studied sections. These include the chronC30n/29r reversal around the boundary of units 11/12 at Zumaia (16 beds), Sopelana I (43 beds)

and Hendaia (9 beds) sections, and the C31r/C31n reversal in unit 6 at Zumaia (33 beds),Sopelana I (13 beds) and Hendaia (10 beds). Natural remanent magnetization (NRM) andremanence through demagnetization were measured on a 2G Enterprises DC SQUID high-

resolution pass-through cryogenic magnetometer (manufacturer noise level of 10-12 Am2)operated in a shielded room at the Istituto Nazionale di Geofisica e Vulcanologia in Rome, Italy.

A Pyrox oven in the shielded room was used for thermal demagnetizations and alternating field(AF) demagnetization was performed with three orthogonal coils installed inline with thecryogenic magnetometer. Progressive stepwise AF demagnetization was routinely used andapplied after a single heating step to 150C. AF demagnetization included 14 steps (4, 8, 13, 17,21, 25, 30, 35, 40, 45, 50, 60, 80, 100 mT). Samples that did not fully demagnetize after this

protocol where further demagnetized thermally and a number of samples where demagnetizedusing only thermal treatment. Characteristic remanent magnetizations (ChRM) were computed byleast-squares fitting (Kirschvink, 1980) on the orthogonal demagnetization plots (Zijderveld,1967).

Calcareous nannofossils

Nannofossil content was analyzed in 76 samples along the Upper Maastrichtian of the SopelanaI section from the K/Pg boundary down to the lower part of Unit 6 (~67 m in total thickness). Nosamples were collected in unit 7 as it is tectonized and most likely incomplete. The samplingresolution strategy is aimed at obtaining full nannofossil data for every marls-limestone couplet in

order to pinpoint precisely the main Upper Maastrichtian nannofossil biohorizons. A small chip ofthe rock sample was processed and fixed on a smear slide, following the standard preparationtechnique (Bown and Young, 1998) in order to preserve the original species composition. Thenannofossil analysis was performed using a Zeiss Axioscop 40 microscope at magnification1250 X. Photographs were taken with a ProgRes GT3 camera and its corresponding software.Three lon traverses were lo ed on each slide and nannofossil relative abundance was


8/24

recorded semi-quantitatively, using standard categories: Common (C), 110 specimens per fieldof view (fov), Frequent/Few, 1 specimen 20 fov.

The calcareous nannofossil biozonation for the Upper Maastrichtian used here is primarily basedon the UC scheme of Burnett (1998), but the previous CC biozonation of Sissingh (1977) andRoth (1978) as emended by Perch-Nielsen (1985) is also considered (Fig. 4). The taxonomicconcepts are generally following those of Perch-Nielsen (1985) and Burnett (1998), but somerecent emendations are applied too (Lees and Bown, 2005; Lees, 2007; Thibault, 2010). The

taxonomic characterization of all species can be found at www.nannotax.org.

Spectral analysis and orbital solutions

The Zumaia bulk carbonate record from units 10, 11 and 12 from Ten Kate and Sprenger (1993)has been used for spectral analysis. The original dataset was collected at intervals of 10 cmalong the 63.7 m succession were many thin bedded turbidites ranging from 0.1 to 12 cminterbedded within the rhythmic hemipelagic marl-limestone couplets can be recognized. Thepublished record was digitized and resampled at 10 cm intervals prior to spectral analysis. TenKate and Sprenger (1993) followed a strategy to tune the record to the theoretical eccentricity

curve available at the time (Berger, 1978) extrapolated to 65 Ma. The procedure started with astrong smoothing of the carbonate record using a weighted three-point moving average a numberof times on a 2.5 cm interpolated spline curve fitted though the original data points. It proceededmaking first a visual correlation of minima in the record and the target curve. Correlation wassubsequently refined by assessment of other smaller scale features. Then, spectral analysis wasperformed on the time domain to conclude that indeed the carbonate rhytmicity is orbitallycontrolled as power on the precession and eccentricity bands was observed. The authorsrecognized that extrapolating the Bergers equation to 65 Ma was unacceptable because ofinaccuracies in the solution that could amount 0.4 Ma and therefore any absolute chronologicalconstraints had to be flawed. We also note that correlating the eccentricity minima to lowcarbonate minima clashes with the observed details of cycle pattern recognition that suggests an

opposite phase. Indeed, as it has been observed for the Paleocene interval, precession-relatedcycles are less well developed in the limestone-dominated intervals of eccentricity-relatedcycles, indicating that these beds indeed correspond to eccentricity minima because eccentricitymodulates the precession signals amplitude (Dinars-Turell et al., 2003, 2010, 2012; Kuiper etal., 2008). Consequently, the approach we have followed to analyze the carbonate record fromZumaia is different. We have first performed spectral analysis in the depth domain and haveinferred the astronomical frequencies and periods. Subsequently, the orbital cycles are extractedfrom the record by using bandpass Gaussian filters centered on the significant periodicities. Thestandard (Fourier) spectra was calculated using the software package "AnalySeries" (Paillard etal., 1996) that has also been employed for filtering purposes. The Continuous Wavelet Transform(hereafter CWT) (Torrence and Compo, 1998) that has been divided by its scales to account for a

bias in the power spectrum (Liu et al., 2007), has also been applied to analyze the time evolutionof the spectral power and to better visualize the eccentricity amplitude modulations on theprecession.

Modern astronomical solutions that include a direct numerical integration of the planet orbits andthe precession of the Earth spin axis include the Varadi et al. (2003) Va03_R7 and Laskar et al.,(2004) La2004 orbital solutions. The Va03_R7 solution was first used to tune the Danian portionof the Zumaia section (Dinars-Turell, et al., 2003) whereas later the La2004 solution has beenpredominating in the literature and used to tune the Neogene (Lourens et al., 2004) in theGTS2004 geological time scale (Gradstein et al., 2004). Due to the chaotic behavior of the solarsystem the orbital solution cannot be accurately calculated beyond 40 Ma (Laskar et al., 2004),and therefore, only the stable 405-ky eccentricity cycles can be used for tuning purposes. In aneffort to improve the accuracy of the astronomical solution beyond 40 Ma, a new solution(La2010) has recently been put forward (Laskar et al., 2011a) that makes use of a new highprecision planetary ephemeris called INPOP. In fact, four solutions are proposed, La2010a, b, c,d that are ad usted in a different manner with the sco e to evaluate the lon -term recision of the
http://www.nannotax.org/


9/24

solutions which was still retained of limited accuracy beyond ~60 Ma (Laskar et al., 2011a).Further developments on the ephemeris precision and methodological computations have led toyet another solution La2011 (Laskar et al., 2011b) which slightly refines the previous solutions.However, Laskar et al. (2011b) demonstrate that the motion of Ceres and Vesta is highly chaotic.

As a consequence, a precise calculation of Earths eccentricity beyond 60 Ma is not possible,and probably will never be (see Westerhold et al., 2012 for additional details). A stability test onthe La2010 and La2011 orbital solutions performed by Westerhold et al. (2012) suggests thatonly the La2010d and La2011 solutions should be used beyond ~47 Ma. As a conclusion it

remains clear that for the Maastrichtian an accurate tuning for the short eccentricity is notpossible and only the 405-ky beat can be used for that purpose. Only continuous very longgeological astronomically forced records could shed light on the orbital configuration at thoseolder time scales. Our scope in this paper is not to look in detail the tuning options, but just topresent a cyclostratigraphic template among the different Upper Maastrichtian sections from theBasque Basin for further future developments.

Results

The integrated cyclostratigraphic, magnetostratigraphic and biostratigraphic results arepresented for both the Zumaia and Sopelana I main sections in inverse stratigraphic orderfollowing the lithological units of Wiedmann (1988) from younger units 1210 to older units 97.Results from the accessory section Hendaia are presented separately at the end.

Units 1210

Units 1210 are magnificently exposed at the coastal-cliff of Punta Aitzgorri in Zumaia (Figs. 5a-c) which is reachable by foot at low-tides. The succession is also exposed on the wave-cutplatform during very low-tides (Figs. 5d, e) and the marl-limestone couplets are relatively easy torecognize with the exception of the couplets within Unit 12 below the K/Pg boundary due to theirgenerally more marly character and the presence of very thin interbedded turbidites. However, ingood lighting conditions and low tide level, couplets can clearly be distinguished. The lithologicalcouplets have been numbered from the K/Pg downward and consist of a marly layer at thebottom and a carbonate-rich bed at the top. A total of 72 basic couplets with average thicknessaround 0.9 m have been recognized along the interval under consideration. The first threecouplets (13) just below the K/Pg are relatively thick and carbonate rich. Couplets 6 and 910also are carbonate-rich. Couplets 1113 are somewhat more difficult to recognize because theyare thin and relatively homogeneous. Then, a very characteristic prominent marl bed is found incouplet 14. Below this level the couplets are easily to recognize down to the base of Unit 10 andopen bundles of about 5 couplets can eventually be observed. Furthermore, some intervals with

relative low amplitude of the limestone-marl couplets can seemingly be observed (intervals ofcycles 3539 and 5560) (Figs. 5b, c).

A high-resolution carbonate record had previously been produced and analyzed to evaluateastronomical forcing in units 1012 (Ten Kate and Sprenger, 1993), demonstrating that indeedthe lithological couplets in the Maastrichtian also represent precession cycles of ~21-ky duration.Here, we take the same record and perform the spectral analysis in the depth domain in order toextract the precession and the short (~100-ky) and long (~405-ky) eccentricity-relatedperiodicities. Three distinct periodicities can be distinguished on the standard Fourierperidogram (Fig. 6a) and Blackman-Tukey spectrum (Fig. 6b). A band of significant frequencieswith periods at 0.7-0.95 m is associated to the couplet and related to precession. A period at 4.1

m is related to the short eccentricity while a narrow period at 17 m that appears blurred on theBlackman-Tukey spectrum, can be associated to the 405-ky long eccentricity. Figure 7a showsthe distribution of the precession cycles (i.e the 72 marl-limestone couplets named Pk1 to Pk72),

and the short and long eccentricity cycles along units 1210 at Zumaia. The CWT spectrum (Fig.7b) allows visualizing the space evolution of these periodicities that also emerge on the global


10/24

spectrum. It appears clear that the precession band along the lower stratigraphic interval (5264m) is shifted to slightly higher periods due to the presence of relatively thicker couplets along thisinterval (Fig. 5d). Another advantage of the CWT spectra is the ability to display variations in theoverall amplitude within a certain band. As it is known that eccentricity acts modulatingprecession the CWT spectra becomes a useful tool to unravel such scenario since the overallsignificance of the eccentricity power in the standard spectra may be depleted under a strongprecession forcing on the sedimentary record (e.g. Dinars-Turell et al., 2012). The precessionband on the CWT spectrum (Fig. 7b) shows three zones of relatively lower amplitude. They are

clearly associated to the 405-ky long eccentricity minima that we have named Ma4051, Ma4052and Ma4053 from the K/Pg boundary downward following the terminology used by Westerhold et

al. (2008) and Husson et al. (2011) although these authors numbered the eccentricity maximainstead. Gaussian bandpass filters centered at the retrieved periods have been used to extractthe orbital cycles from the carbonate record (Fig. 7a). The ~100 ky eccentricity minima have alsobeen numbered from the K/Pg downward. A total of 17 short eccentricity cycles have beenrecognized along the interval comprising units 1012 (named E1 to E17). However, it is notedthat cycles E3 and E4 are less well defined while cycles E16 and E17 appear to have less thanthe usual 46 precession cycles that could be an artifact of the higher sedimentation rate alongthis interval and consequently the number of eccentricity cycles could be overestimated.

No magnetostratigraphic results from Zumaia have ever been published for the Maastrichtianunits 1210 despite several attempts by different researchers (Ten Kate and Sprenger, 1993;Verosub, personal communication 2000). In fact, Ten Kate and Sprenger (1993) quote a non-substantiated layer by layer correlation of the Zumaia and Sopelana successions, for which theavailable magnetostratigraphic study at Sopelana (Mary et al., 1991), was used to infer theposition of chron reversal C30R/C31N (as it is quoted originally) at 12.3 m below the sampledinterval at Zumaia (and one should understand in Unit 9). This depth figure seems to have beenused to place the C30n/C29r position at Zumaia by Westerhold et al. (2008) (and probablyHerbert et al., 1995), while it is clear that Ten Kate and Sprenger where referring to a reversaltranslated at 74.75 m below the K/Pg boundary at Zumaia (see their Table 1). Overall, this is

quite confusing because Herbert et al. (1995) depict the Zumaia carbonate record of Ten Kateand Sprenger (1993) along with the inferred/translated magnetostratigraphy from Sopelana andclaim to count 18 precession cycles for the Maastrichtian part of chron C29r which is close oftheir inferences on South Atlantic deep sea records of 18.5 cycles. In any case, Herbert et al.(1995) and Herbert (1999) indicate that the C30n/C29r reversal appears to be located close to anode of low amplitude precession cycles related to the 405-ky eccentricity minima. This was alsodeduced by Westerhold et al. (2008), who infer it close to the minimum between their Ma100-4

and Ma100-3 short eccentricity cycles, although the inferences from Zumaia-Sopelana by these

authors may be flawed in detail. Mary et al. (1991) at Sopelana did not report any reference tocyclicity counting and they only report the C30n/C29r chron boundary at 8 m below the K/Pgboundary. While reporting herein a comprehensive bed-by-bed correlation and cycle countingbetween Zumaia and Sopelana, we have revisited and report new magnetostratigraphic data thataimed at reproducing the original data from Sopelana. Recent paleomagnetic data by Prez-Rodrguez et al. (2012) from the lower part of Unit 10 at Zumaia has confirmed the earlier notionon the difficulty of retrieving a primary useful magnetic signal there. Here, we presentdemagnetization data from Unit 11 along the stratigraphic interval where the C30n/C29rboundary should be placed (Fig. 8). In essence, our combined thermal and AF demagnetizationprotocol allows inferring a somewhat complex scenario of a reversed remagnetization carried byboth magnetite and hematite fractions. In particular, the hematite unblocks at relatively low-temperature (from 300C to about 640C) suggesting a secondary chemical origin. Samples fromprecession cycles PK14 (Fig. 8b) and PK16 (Fig. 8e) display a normal component blocked on

hematite and magnetite respectively but the majority of samples only present a pervasive reversecomponent retained a secondary remagnetization, as was inferred for Unit 10 by Prez-Rodrguez et al. (2012).

Careful observations have been made at Sopelana I section along units 1210 below the K/Pg


11/24

boundary that has been facilitated by the dismantling of some buildings that partly obstructed thecliff outcrops. Some complex faults make at first glance difficult to follow the cyclic pattern there,but we have been able to reconstruct a continuous section that expands units 1210 along twopartly overlapping faulted blocks (Fig. 9) and to recognize the 72 marl-limestone couplets (i.e.precession cycles PK1 to PK72) first seen at Zumaia including all the lithologic particularities and

cyclostratigraphic stacking pattern (e.g. relatively carbonate-rich cycles PK6, and PK910, and

the prominent marl at cycle PK14 among others). It is noteworthy that the Maastrichtian

succession at Sopelana I lacks the presence of turbidites.

A thorough magnetostratigraphic study has been conducted along units 1210 particularlyfocusing on Unit 11 with the aim to precisely relocate the C30n/C29r chron boundary. We havealso performed a high-resolution calcareous nannofossil survey for the first time in this section(Fig. 10). Paleomagnetic results very much resemble the findings from Zumaia. A pervasivereverse overprint seems to be present throughout the studied interval blocked either in magnetiteand/or hematite as deduced from the combine thermal/AF demagnetization protocol (samplesSM5A, SJ69-1A, Fig. 10b). It is noted that thermal demagnetization only on a sister sample(sample SJ69-1B, Fig. 10b), does retrieves what it seems a spurious component most likely dueto overlap of unblocking temperatures of the two components clearly seen on the combined

protocol (sample SJ69-1A, Fig. 10b). This alerts on the intricate nature of the magnetization ofthese reddish rocks and could explain some of the results reported in Mary et al. (1991) andMoreau et al. (1994). Strikingly, a narrow zone of normal polarity (e.g. sister samples SO-2A andSO-2B, Fig. 10) is found along cycles PK4PK6 that seem to coincide with some awkward

directions reported by Mary et al. (1991) at 25 m below the K/Pg boundary that they related toplasticity and deformation on these marly lithologies. Although isolated samples with normalpolarity have been measured along Unit 11 (see the declination and inclination log, Fig. 10a), noclear picture regarding an unambiguous definition of chron C30n and hence of the C30n/C29rchron boundary could be established. Collectively, the dataset from Zumaia and Sopelana castssome doubts on the earlier interpretations and we regard the magnetization of the reddishlithologies from the Maastrichtian succession complex and unsuitable for magnetostratigraphic

purposes.

Calcareous nannofossils are abundant throughout the studied Upper Maastrichtian successionand represented by highly diverse associations showing good to very good preservation. Thefirst occurrence (FO) ofMicula murus (Plate I, 12) is found in Sopelana at precession cycle Pk41

below the K/Pg boundary (~861 ky below; Fig. 10) (see Table 1 for a full account of bioevents). Itis interesting to point out that this primary biotic datum is recorded just 5 m (11 precession cycles= ~231 ky) below the FO ofM. prinsii. The acme ofM. murus is observed up section, within the M.prinsii zone. Calibration of these two biohorizons to the magnetic polarity scale and constrainingthe accurate age through integrated cyclostatigraphy is very important to evaluate theirbiostratigraphic potential considering the previous studies have clearly shown a latitudinaldiachroneity of this datum between the low- and mid-latitude records (Thibault et al., 2010).

The occurrence ofCeratolithoides kamptneriis not recorded in the Upper Maastrichtian ofSopelana, so making impossible to distinguish the UC 20c subzone (see Fig. 4). However, it hasrare and spotty occurrence in many other low-latitude sections (Gardin et al., 2012).

The FO ofCribrosphaerella daniae (cycle PK39, Plate I, 20) is a clearly expressed bioevent

following the FO ofM. murus (cycle PK41, sample S12-6; Fig. 10). This datum is used for

subzonal marker in the Upper Maastrichtian "tethyan-intermediate" province -North Germany andthe Indian Ocean by Burnet (1998). In Sopelana it falls in a position that should correspond to the

upper part of C30n. However, it has been reported close to the C31r/C31n boundary in Hole1258A (Equatorial Atlantic) by Husson et al. (2011). This sheds some concerns about theisochrony of the datum and, therefore, its biostratigraphic potential needs to be better assessed.

The FO ofMicula prinsiiin Sopelana (sample SOP-29 in cycle PK29, Plate I, 14-16; Fig. 10) is


12/24

recorded relatively low in the succession as this biovent has usually been placed close to theC30n/C29r boundary (e.g. Herbert et al., 1995; Westerhold et al., 2008). It is a primary

biostratigraphic marker for the uppermost part of the Maastrichtian, identifying subzone UC 20dTP

and CC 26b in low-latitude sites (see Fig. 4), where it is usually reported near the base of C29r.However, some recent studies have recorded it at the top of C30n (Self-Trail, 2001; J. Lees,unpublished data). At Sopelana, the FO ofMicula prinsiiis an unambiguous distinct biohorizonthe record of which may have been favored by the predominantly marly lithologies deposited in asetting devoted of turbidites. In this study, the calibration of this datum at about 609 ky below the

K/Pg boundary, expectedly within chron C30n, may imply either diachrony or erroneouscalibration of the existing biostratigraphic data. For example, at Zumaia, situated just some 70 kmfrom Sopelana, it has been documented close to the K/Pg boundary in C29r (Lees in Prez-Rodrguez et al., 2012) (see Fig. 2), although the reported poor preservation there may have arole. Furthermore, Thibault et al. (2012) in his integrated study on ODP Hole 762C from theIndian Ocean, have calibrated the bioevent at 39070 ky below the K/Pg boundary.Nevertheless, we note that this bioevent has already been shifted to an older age in theGTS2012 time scale (Gradstein et al., 2012) (see Fig. 4) although no explanation is provided.

The First Rare Occurrence (FRO) ofNephrolithus frequens (sample C-SO-14 in cycle PK26,

Plate I, 20) is observed in the uppermost part of the succession (Fig. 10). It has been used todefine the base of CC 26a (see Fig. 4), but then it has been proved to be time-transgressivetoward the equator in southern high latitudes (Pospichal et al., 1992). In Sopelana its occurrence

is rare but consistent along the uppermost part of the Maastrichtian UC20dTP zone.

Units 97

Determining the cyclic stacking pattern for units 98 and counting precession cycle (i.e. marl-limestone couplets) and eccentricity-related bundles is relatively straightforward. The fieldphotographs from Fig. 11 illustrate this interval both at Zumaia and Sopelana I. A total of 32precession-related couplets are recognized (cycles P

K73 to P

K104) which comprise 6

eccentricity-related cycles that we have coded E18 to E23 (following the 17 eccentricity cyclesfrom units 1210). These 100-ky eccentricity cycles are made evident by a series of two or threeconsecutive basic couplets with relatively well developed marly layers that have to correlate toeccentricity maxima, while the eccentricity minima is marked by one or two low-amplitudecouplets with less developed marly interlayers, which are more clear in the images fromSopelana (Figs. 11a-c).

The relatively marly reddish Unit 7 is better exposed at Zumaia (Fig. 12) while i t appearstectonized and possibly truncated/reduced at Sopelana (Fig. 3). Watchful look at Unit 7 atZumaia under good lighting conditions makes evident the same stacking pattern observed in the

overlying units and particularly the eccentricity-related bundles can be recognized (Fig. 12). Aslithological couplets are difficult to distinguish along some intervals we have not counted themalong this unit and proceed only with the eccentricity-related bundles. The E26 cycle is not clearbecause within this lower part of Unit 7 several relatively thicker conspicuous turbiditic layers areinterbedded.

Unit 6

Unit 6 is characterized at Zumaia as a ~15 m thick carbonate-rich package with a characteristic1.2 m thick marly interval (including a couple of thin turbidites) in the middle that has been nick-

named Escaln (Fig. 13). The marly beds of the precession-related couplets along this intervalare not well developed and several partitions and thin to very thin turbidites make distinguishingcyclicity a demanding task. A combination of observations on the sea-cliff wall and the tidal flatunder different lighting conditions allow figuring out a total of 24 precession-related couplets and4-5 eccentricity-related bundles of 46 couplets from the top of this unit down to four very


13/24

characteristic relatively thin and marly small cycles (cycles 2528 in Fig. 13). Becauseprecession cycles are somewhat blurred in Unit 7, counting the precession-related couplets forUnit 6 has re-started at the top of Unit 7 and named PE1 to PE24). Unit 6 has been targeted to

precisely locate chron C31r/C30n reversal (Fig. 14). Magnetic intensity in those light greylimestones is relatively low (usually below 0.1 mA/m) but demagnetization data is of good qualityfor most of the studied samples and a clear magnetostratigraphy could be established, asinferred in Prez-Rodrguez et al. (2012), that we can now place in a good cyclostratigraphicframework. The C31r/C31n is placed at precession cycle PE201 from top of Unit 6 at Zumaia

(further discussion below).

The succession at Sopelana I section is devoid of turbidites, but some structural complicationsand outcrop conditions make somewhat difficult the recognition of all cycles and details at firstglance. However, taking the four characteristic small precession cycles that are clearly visible upin the cliff (Fig. 15a and c), one can visualize cycles PE13PE24 in the top outcrop of the cliff

despite some small faults and intrastratal sliding and folding disrupt a little the succession.Cycles PE13PE21 outcrop again at the beach, on another block separated by a fault, below a

poorly exposed Escaln (Fig. 15d). Cycles PE1PE11 above the Escaln outcrop on the same

block at the beach although some of the cycles appear difficult to recognize due to the

predominantly carbonatic nature of the interval and to some minor disruptions and partitions.Paleomagnetic sampling along this interval (Fig. 15b) indicates that chron C31r/C31n boundarymust be located between the marly layer of cycle PE20 and the marly layer of cycle PE18

(sample from cycle PE19 did not provide interpretable results).

The calcareous nannofossil survey along this interval indicates the FO of several taxa (see Table1 for full details). The FO ofLithraphidites quadratus (Plate I, 14), an important low-latitudebiohorizon, is recorded at cycle PE6 from the top of the unit and PE12PE13 cycles (252273 ky)

above the base of chron C31n. Its position at Sopelana is consistent with the previously reportedposition in the Umbria-Marche pelagic sections (Gardin et al., 2012) and at Zumaia (Lees in

Prez-Rodrguez et al., 2012). Some previous researchers considered this biohorizon aspotential marker for the placement of the lower-upper Maastrichtian boundary (Paul andLamolda, 2007). The species is reported to have wide geographic distribution in low-latitudesections and thus can be used as reliable correlation biohorizon there.

The Hendaia section

It has seen above, that despite some lithological differences between the Zumaia and Sopelana Isections (i.e. lack of turbidites in the second), the previously defined li thologic units 6 to 12 andmarl and limestones beds can be correlated by-by-bed between these two (70 km apart)

sections. The nature of these main differences is probably related to the particular depositionalsetting of each section within the deep-water trough. In order to further explore and substantiatethe findings at Zumaia-Sopelana I, additional research has been undertaken in other Basquesections. Here, we only present results from the less known Hendaia locality along the PointeSainte-Anne because it provides some better clues for the cyclic details of Unit 6 and the positionof chron C31r/C31n reversal. Also, an attempt to document the location of chron C30n/C29rreversal has been undertaken.

The Upper Maastrichtian succession outcrops in a series of spectacular coastal-cliffs around thePointe Sainte-Anne near Hendaia, which are difficult to access and only reachable partly at lowtides (Fig. 16). Although bedding is subhorizontal or gently dipping, the area is cross-cut with

several small-scale, but also some more important faults and peculiar contacts. Nevertheless, thegeneral lithostratigraphic units can be recognized (see sketch in Fig. 16). The upper part of theMaastrichtian along the contact between units 1112 has been studied at the North end of thecape (Hendaia N section) (Fig. 17). The paleomagnetic measurements on 13 samples from 10consecutive cycles spanning cycles PK8PK19 along the expected interval for the C30n/C29r


14/24

boundary only indicate reverse polarities (Figs. 17bd) ascribed to a secondary pervasiveoverprint in those lithologies, much in the line with the observations made at Zumaia andSopelana. Consequently, we have not been able to locate this chron boundary in any of theinvestigated sections from the Basque Basin.

Unit 6 has been studied in the central part of the Pointe Sainte Anne outcrop, along a section wehave named Hendaia E. Along this outcrop Unit 6 is less carbonatic than in Zumaia-Sopelana Iand outstanding precession cycles are obvious (Fig. 18) with the conspicuous Escaln showing

clear, especially when a weathering profile is seen (Fig. 18b and Fig. 19a). Here, amagnetostratigraphy along cycles PE14PE23 below the top of the unit confirms and

substantiates that the C31r/C31n boundary occurs at cycle PE20 (8 cycles below the Escaln,

Fig. 18c). Figure 19 displays views of Unit 6 at Hendaia E and Hendaia W which is located notfar on the other side of the bay (see Fig. 16 for location), and also at Zumaia. Despite the shortdistance the two Hendaia outcrops display slightly different characteristics, Hendaia E havingsome reddish colouring along the lower interval, but otherwise all the precession cycles andparticularities match bed-by-bed among the three sections. In particular the four small cyclesbelow cycle PE24, the prominent marl below cycle PE33 and the two relative well developed

marls of cycles PE29 and PE30 are clearly seen (see also this interval at Sopelana I in Fig. 15c).

Discussion

Much controversy has been generated about the absolute age of the K/Pg boundary whichseems to jump as much as 1 My even in the most recent Geological Time Scales. An age of 65Ma was used in Berggren et al. (1995) whereas 65.5 Ma was adopted in the GTS2004 (Gradsteinet al. 2004) without incorporating cyclostratigraphic constraints. Using the first modernastronomical solution Va03_R7 of Varadi et al. (2003) we tuned the K/Pg boundary at Zumaia toan age of 65.83 Ma (Dinars-Turell et al., 2003) by using as first anchoring the expression of anode in the very long eccentricity cycle in the upper part of the Danian, and then following andtuning consecutive short eccentricity-related bundles and precession cycles down to the K/Pgboundary, which is less accurate than tuning the 405-ky eccentricity cycle for those older agesbut still a good metronome. The Paleocene tuning at Zumaia was revisited by Westerhold et al.(2008), Kuiper et al. (2008) and Hilgen et al. (2010) on the light of newly available solutions (theLa2004 solution, Laskar et al., 2004) and basing the tuning on the more stable 405-yr eccentricitycycle and some reinterpretation of cycle identification. Due to uncertainties in the radioisotopemonitor standards these authors presented several options by offsetting tuning to consecutive405-ky cycles, thus attaining different ages for the K/Pg boundary. The favored tuning option toLa2004 in Kuiper et al. (2008) and Hilgen et al. (2010), following the 405-ky tuning strategy,placed the K/Pg boundary at 65.95 Ma, which is basically the same as in Dinars-Turell et al.

(2003) (difference arising by the interpretation of an additional 100-ky eccentricity cycle in theZumaia record), an age that was in support of the authors new re-evaluation of the Fish CanyonSanidine (FCS) monitor standard at 28.20 Ma. The three tuning options for the K/Pg boundaryprovided in Westerhold et al. (2008), 65.28 Ma, 65.68 Ma and 66.08 Ma respectively have beenfavored and disfavored, while the most recent calibration along the earliest Paleogene, which isindependent of the radioisotope ages and uses the La2011 orbital solution (Westerhold et al.,2012), indirectly recalibrates controversially the FCS at 27.89 Ma and puts the K/Pg at 65.250 Maclose to their earlier option 1. Other inferences on tuned Maastrichtian deep-sea records byHusson et al. (2011) that seem to have been incorporated to the last Geological Time Scale(Gradstein et al., 2012) favor the estimate of the K/Pg boundary at about 66 Ma close to a 405-kyminimum around that age. It is out of the scope in this paper to further scrutinize the Paleocene

orbital tuning and absolute age of the K/Pg boundary, and for practical reasons we have adoptedthe age of ~66 Ma for the K/Pg and used the La2010d orbital solution as a template for our UpperMaastrichtian framework, acknowledging that this solution can only be taken as tentative andonly valid for the 405-ky eccentricity cycle.


15/24

A direct cycle counting and bandpass filtering output is the basis of our cyclostratigraphicframework for the Upper Maastrichtian from the Basque Basin. Figure 20 displays the salientfeatures of this framework taking Zumaia as the master section. Considering the position of theK/Pg boundary as outlined above, the Zumaia record can be tuned to the La2010d orbitalsolution (Laskar et al., 2011b) following the 405-ky cycle. Therefore, the three consecutiveeccentricity-related cycles named Ma4051 to Ma4053 can be tuned to successive eccentricity

minima of that cycle in the orbital solution. Note that we code eccentricity minima and not themaxima as has been the praxis of other authors (e.g. Westerhold et al, 2008, Husson et al., 2011,

Thibault et al., 2012) because we feel it more useful and practical in those land-based sectionswhere carbonate-rich or low-amplitude intervals usually appear prominent and stand out in thefield. For lithological units 8-9 individual precession-related couplets or Pk cycles and 100-ky

eccentricity cycles direct counting is provided (Fig. 20b). For marly Unit 7, for which individualprecession cycles are somewhat blurred, only eccentricity counting is provided. Consequently,counting the precession-related couplets for the underlying Unit 6 has started at the top of thisunit denoted as top Escaln (PE cycles). The exact genetic nature and significance of the two

conspicuous marly couplets constituting the Escaln is not clear. We assign them to anaccentricity maxima but the possibility that may represent a local/regional tectonically driven sea-level or a climatic event deserve further attention. Under this cyclostratigraphic scheme, chron

C31r/C31n occurs slightly below the eccentricity maxima between cycles E32-E33 (20precession cycles below the top of the unit at PE20), (Fig. 20 and discussion above). In the

Maastrichtian astronomical calibration of Husson et al. (2011), ODP Site 525A from the SouthernAtlantic is chosen to calibrate this reversal boundary. In their option 2, which considers the K/Pgboundary at about 66 Ma, the C31r/C30n boundary is calibrated at 69.220.07 Ma (i.e. 3.22 Myolder than the K/Pg boundary), and close to their eccentricity maxima labeled 32 (wouldcorrespond exactly to the maxima between our E32-E33 cycles). This is fairly consistent with ourdetermination but it is not clear how Husson et al. (2011) reach the figure of 3.22 My reported intheir Table 3 for the position of C31r/C31n relative to the K/Pg boundary. It looks that they haveadded the duration of the Maastrichtian part of chron C29r (0.3 My), C30n (1.9 My), C30r (~0.12My) and C31n (~0.9 My) which combine data from sites 1267B and 525A as they report in Table

1, although it still remains unclear which orbital cycles they base their counting and durationestimates. Anyhow, we could take the absolute age of eccentricity maxima between cycles E32and E33 in the La2010d solution (69.027 Ma) and add two precession cycles to account for theinferred position at cycle PE20 just below the eccentricity maxima and wil l reach a figure of

~69.08 Ma or ~3.08 My from the K/Pg boundary (Fig. 20).

Furthermore, the cyclostratigraphic framework allows estimating the duration of the 3rd-orderdepositional sequences which have been interpreted as controlled by sea-level variations (seeIntroduction). It is obvious that a pacing close to 1.2 My seems to act for the two late Maastrichtiandepositional sequences UMa-1 and UMa-2 (Fig. 20). The 1.28 Ma duration estimate for UMa-1

comes directly from counting precession-related couplets for units 10-11 (61 cycles, PK12PK72)and taking and average duration of ~21 ky (Fig. 20). The estimate of 1.1641.205 Ma for UMa-2is derived by the use of two slightly different calculations. One (1.205 Ma) considers the additionof 32 precession cycles plus 5.5 short eccentricity cycles with an estimate duration of 97 ky(Maastrichtian mean duration calculated from the La2010d solution). The second (1.164 Ma) isbased on the estimate of 12 short eccentricity cycles for the interval comprising units 79 (Fig.20). We also note that the Ma-Da depositional sequence also fits the same pattern and durationas it comprises 8 (may be 9) eccentricity cycles in the Danian (see Dinars-Turell et al., 2003)and 2-3 in the Maastrichtian part. The sea-level drop at the base of UMa-2 close to theLower/Upper Maastrichtian boundary may be a causal factor in the mid-Maastrichtian extinctionwhich affected the Inoceramidae, rudistid bivalves and other mollusks, as well as a sharp decline

of the ammonites (e.g. Ward et al., 1991; Ward and Kennedy, 1993). Stable isotope data frominoceramid shells along the latest Lower Maastrichtian from the Basque Basin that haveundergone diagenetic effects of burial processes still preserve the trends of paleoenvironmentalsignals (Gmez-Alday et al., 2004). These authors have inferred a cooling trend following adecline in abundance and diversity before the final inoceramid extinction. The record of the


16/24

boreal inoceramid Spyridoceramus tegulatus, which is coincident with the positive d18Oexcursion in their defined stage E2 along the upper part of lithological Unit 5 and Unit 6 ,suggests the entry of deep, cold, oxygenated waters arriving from the North Atlantic. Theseobservations confirm the modification of the thermocline and the onset of climatic cooling close tothe Early/Late Maastrichtian boundary.

The clear imprint of sea level fluctuation as evidenced by the Upper Maastrichtian 3rd-orderdepositional sequences paced at about 1.2 My rhythm is, thus, consistent with a long-period

obliquity influence on sea level. Such type of scenario during the Oligocene time has beenshown to be related to carbon cycle events, and glacial periodicity. Possible drivers for this long-period linkage between orbital cycles, sea level, and the carbon cycle during the Cretaceousgreenhouse, a time during which continental ice sheets are expected to be either ephemeral ornon-existent have been considered (Wendler et al., 2011). Studying Cenomanian-Turoniancarbonate platforms in Jordan, these authors postulate that systematic changes in weatheringpatterns that are consistent with variable freshwater transport between the ocean and land,support the hypothesis that freshwater storage in aquifers played an important role in modulatingeustacy. We believe that the Campanian-Maastrichtian succession from the Basque Basin canin the near future, not only contribute toward the improvement the general chronostratigraphy andthe new generation of the Geological Time Scale, but also to shed light to many intriguingpaleoclimatic trends and features in response to orbital forcing.

Conclusions

1. A bed-by-bed comprehensive correlation has been established for the Upper Maastrichtianhemipelagic succession from the Basque Basin at Zumaia, Sopelana I and Hendaialocalities comprising the classical lithological Units 612 of Wiedmann (1988) that spanabout 150 m of stratigraphic thickness at Zumaia that equal to ~3.1 My time.

2. An available carbonate proxy record for the uppermost units 1012 along 64 m of section

containing 72 marl-limestone couplets at Zumaia is used for spectral analysis to retrieve thefull hierarchy of orbital cycles that include, besides the precession-related couplets of 21 kymean duration, the short (~100 ky) and long (405 ky) eccentricity cycles. Cycle countingand the stacking of eccentricity-related bundles is followed downsection and correlatedamong the studied sections.

3. Strategic paleomagnetic sampling has been conducted to delineate the two main reversalswithin the Upper Maastrichtian, the chrons C31r/C31n and C30n/C29r boundaries. Thedataset along the upper reddish units 11-12 at Sopelana I, Zumaia and Hendaia thatshould contain C30n/C29r, indicates that those lithologies have been remagnetizedthrough a relatively complex mechanism and appear useless for magnetostratigraphicpurposes, casting some doubt to earlier results from Sopelana that we have not been able

to reproduce. Instead, the gray lithologies from Unit 6 host a weak but primarymagnetization allowing the unambiguous identification of chron C31r/C30n reversalboundary at the three studied sections which can be placed in a solid cyclostratigraphictemplate, superseding previous studies.

4. An integrated high-resolution calcareous nannofossil biostratigraphy is stablished for theentire Upper Maastrichtian that can be placed in the cyclo-magnetostratigraphic framework.The succession of the main documented nannofossil bioevents /biohorizons includes: (1)First occurrence (FO) ofLithraphidites quadratus; (2) FO ofMicula murus; (3) FO ofMiculaprinsii. Furthermore, there are two additional bioevents, considered of secondaryimportance, which complement the nannofossil biostratigraphic record. These are the FO ofCribrosphaerella daniae and the FRO ofNephrolithus frequens in the uppermost part of thesection.

5. The solid orbital chronostratigraphic framework indicates that previously established 3rd-order depositional sequences in the Upper Maastrictian reflect sea-level variations thatseem paced by a strong 1.2 My periodicity reflecting the long obliquity amplitudemodulation cycle.


17/24

6. The cycle duration estimates relative to the K/Pg boundary for the position of the base ofchon C31n, which we propose as an alternative to define the Early/Late Maastrichtianboundary, is 3.08 My (69.08 Ma with the option of the K/Pg at about 66 Ma). This is in l inewith current calibrations of this chron from deep sea records (Husson et al., 2011; Thibaultet al., 2012).

7. Together with earlier work in the Paleocene, the extension of the cyclostratigraphicframework into the Maastrichtian as presented herein, positions the hemipelagicsuccession from the Basque Basin on a potential primary role as a geological aid for critical

developments of the astronomical solutions that are inaccurate in these older times andalso to answer key questions regarding the paleoclimatic evolution of the Mesozoicgreenhouse period in response to orbital forcing.

Acknowledgements

Funding for this research was provided by project CGL2011-23770 of the Spanish Ministerio deEconomia y Competividad. JDT acknowledges a sabbatical grant from the Spanish Ministerio deEducacin, by means of el Programa Nacional de Movilidad de Recursos Humanos del PlanNacional de I-D+i 2008-2011. Beatriz Bdenas and an anonymous reviewer are thanked fornumerous suggestions that have improved the clarity of the paper. Asier Hilario (Scientific

coordinator of the Deba-Zumaia biotope/Basque Coast Geopark) is thanked for his always warmwelcome at the Zumaia outcrops.

References

Arz, J.A. and Molina, E. 2002. Bioestratigrafa y Cronoestratigrafa con foraminferos planctnicosdel Campaniense superior y Maastrichtiense de latitudes templadas y subtropicales (Espaa,Francia y Tunicia). Neues Jahrbuch fr Geologie und Palntologie. Monatshefte, 224, 161195.

Baceta, J.I., Pujalte, V., Serra-Kiel, J., Robador, A. and Orue-Etxebarria, X. 2004. ElMaastrichtiense final, Paleoceno e Ilerdiense inferior de la Cordillera Pirenaica. In: Vera, J.A.,

(ed.), Geologa de Espaa. Sociedad Geolgica de Espaa, Instituto Geolgico y Minero deEspaa, Madrid, 308313.

Berger, A. 1978. A simple algorithm to compute long term variations of daily or monthlyinsolation. Contribution de l'institut d'astronomie et gophysique G. Lemaitre, 18, Universitcatholique, Louvain-la-Neuve.

Berggren, W.A., Kent, D.V., Swisher C.C. and Aubry M.-P. 1995. A revised Cenozoicgeochronology and chronostratigraphy. In: W.A. Berggren, D.V. Kent, M.-P. Aubry, J. Hardenbol(eds.), Geochronology Time Scales and Global Stratigraphic Correlation Special. Publication.,54, SEPM, Tulsa, OK, 129212.

Bown P.R and Young J.R. 1998. Techniques. In: Bown P.R. (ed.) Calcareous NannofossilBiostratigraphy. British Micropalaeontology Society Series. Chapman and Hall/Kluwer AcademicPublishers, London, 1628.

Burnett, J.A., (with contributions from Gallagher, L.T., and Hampton, M.J.), 1998. UpperCretaceous. In: Bown, P.R. (ed.), Calcareous Nannofossil Biostratigraphy. BritishMicropalaeontological Society Publications Series. Chapman and Hall/Kluwer AcademicPublishers, London, 132199.

Burnett, J.A., Kennedy, W.J. and Ward, P.D. 1992. Maastrichtian nannofossil biostratigraphy in

the Biscay region (southwestern France, northern Spain). Newsletters on Stratigraphy, 26, 145155.

Dinars-Turell, J., Baceta, J.I., Pujalte, V., Orue-Etxebarria, X. and Bernaola, G. 2002.Magnetostratigraphic and cyclostratigraphic calibration of a prospective Paleocene/Eocenestratotype at Zumaia (Basque basin, Northern Spain). Terra Nova, 14, 371378.


18/24

Dinars-Turell, J., Baceta, J.I., Pujalte, V., Orue-Etxebarria, X., Bernaola, G. and Lorito, S. 2003.Untangling the Paleocene climatic rhythm; an astronomically calibrated early Paleocenemagnetostratigraphy and biostratigraphy at Zumaia (Basque Basin, northern Spain). Earth andPlanetary Science Letters, 216, 483500.

Dinars-Turell, J., Baceta, J.I., Bernaola, G., Orue-Etxebarria, X. and Pujalte, V. 2007. Closingthe Mid-Paleocene gap: toward a complete astronomically tuned Paleocene Epoch and

Selandian and Thanetian GSSPs at Zumaia (Basque Basin, W Pyrenees). Earth and PlanetaryScience Letters, 262, 450467.

Dinars-Turell, J., Stoykova, K., Baceta, J.I., Ivanov M. and Pujalte, V. 2010. High-resolutionintra- and interbasinal correlation of the Danian-Selandian transition (Early Paleocene): the Bjalasection (Bulgaria) and the Selandian GSSP at Zumaia (Spain). Palaeogeography,Palaeoclimatology, Palaeocology, 297, 511533.

Dinars-Turell, J., V. Pujalte, Stoykova, K., Baceta, J.I., and Ivanov M. 2012. The Paleocene topchron C27n transient greenhouse episode: evidences from marine pelagic Atlantic and peri-Tethyan sections. Terra Nova. doi: 10.1111/j.1365-3121.2012.01086.x

Gardin, S., Galbrun, B., Thibault, N., Coccioni, R., Premoli Silva, I. 2012. Biomagnetochronologyfor the upper Campanian - Maastrichtian from the Gubbio area, Italy: new results from theContessa Highway and Bottaccione sections. Newsletters on Stratigraphy45. doi:10.1127/0078-0421/2012/0014.

Gmez-Alday, J.J., Lpez, G. and Elorza, J. 2004. Evidence of climatic cooling at the Early/LateMaastrichtian boundary from inoceramid distribution and isotopes: Sopelana sections, BasqueCountry, Spain. Cretaceous Research, 25, 649668.

Gmez-Alday, J.J., Zuluaga, M.C., and Elorza, J. 2008. 87Sr/86Sr ratios in inoceramids (Bivalvia)

and carbonate matrix as indicators of differential diagenesis during burial. Early MaastrichtianBay of Biscay sections (Spain and France). Potential use for chemostratigraphy?. CretaceousResearch, 29, 114.

Gradstein, F., Ogg, J. and Smith, A.2004. A Geological Timescale 2004, Cambridge Univ. Press,Cambridge, U. K., doi:10.4095/215638.

Gradstein, F.M., Ogg, J.G., Schmitz, M.D. and Ogg, G.M. 2012. The Geological Time Scale 2012.Elsevier, 1176 pp.

Herbert, T.D. 1999. Towards a composite orbital chronology for the Late Cretaceous and Early

Paleogene GPTS. In: Shackleton, N.J., McCave, I.N., Weedon, G.P. (eds.), PhilosophicalTransactions of the Royal Society of London. A, 18911905.

Herbert, T.D., Premoli-Silva, I., Erba, E., Fischer, A.G. 1995. Orbital Chronology of CretaceousPaleocene Marine Sediments. In: Berggren, W.A., Kent, D.V., Aubry, M.P., Hardenbol, J. (eds.),Geochronology, Time Scales and Global Stratigraphic Correlation. Spec. Publ., SEPM, 8193.

Herm, D. 1963. Mikropalontologisch-stratigraphische untersuchungen im Kreideflisch zwischenDeva und Zumaya (prov. Guipzcoa, Nordspanien). Zeitschrift der Deutschen GeologischenGesellschaft, 15, 277348.

Husson, D., Galbrun, B., Laskar, J., Hinnov, L., Thibault, N., Gardin, S. and Locklair, R.E. 2011.Astronomical calibration of the Maastrichtian (late Cretaceous). Earth and Planetary ScienceLetters 305, 328340.

Hilgen, F. J., Kuiper, K. F. and Lourens L. J. 2010. Evaluation of the astronomical time scale forthe Paleocene and earliest Eocene. Earth and Planetary Science Letters, 300, 139151,


19/24

doi:10.1016/j.epsl.2010.09.044.

Kent, D.V. 1999. Orbital tuning of geomagnetic polarity time-scales. Phil. Transactions RoyalSociety London, 357, 1995-2007.

Kirschvink J.L. 1980. The least-squares line and plane and the analysis of palaeomagnetic data.Geophys.Geophysical Journal of the Royal Astronomical Society, 62, 699718.

Kuiper, K.F., Deino, A., Hilgen, F.J., Krijgsman, W., Renne, P.R. and Wijbrans, J.R. 2008.Synchronizing rock clocks of Earth history. Science, 320, 500504.

Lamolda, M.A. 1985. Biostratigraphie du Maastrichtien basco-cantabrique: ses foraminifresplanctoniques. Gologie Mditerranenne 10 (for 1983), 121126.

Lamolda, M.A. and Gorostidi, A. 1994. Nanoflora y acontecimientos del trnsito CretcicoTerciario. Una visin desde la regin Vascocantbrica. Revista de la Sociedad Mexicana dePaleontologa, 7, 5458.

Laskar, J., Robutel, P., Joutel, F., Gastineau, M., Correia, A.C.M. and Levrard, B. 2004. A long-term numerical solution for the insolation quantities of the Earth.Astron. Astrophys., 428, 261285.

Laskar, J., Gastineau, M., Delisle, J.B., Farrs, A. and Fienga, A. 2011a. Strong chaos inducedby close encounters with Ceres and Vesta.A&A, 532, L4.

Laskar, J., Fienga, A., Gastineau, M. and Manche, H. 2011b. La2010: A new orbital solution forthe long term motion of the Earth.A&A, 532, A89.

Lees, J. A. 2007. New and rarely reported calcareous nannofossils from the Late Cretaceous ofcoastal Tanzania: outcrop samples and Tanzania Drilling Project Sites 5, 9 and 15. Journal ofNannoplankton Research, 29, 39-65.

Lees, J.A., Bown, P.R. 2005. Upper Cretaceous calcareous nannofossil biostratigraphy, ODPLeg 198 (Shatsky Rise, northwest Pacific Ocean). Proceedings of the Ocean Drilling Program,Scientific Results 198, 160. doi:10.2973/odp.proc.sr.198.114.2005.

Liu, Y., Liang, X.S. and Weisberg, R.H. 2007. Rectification of the bias in the wavelet powerspectrum. Journal of Atmospheric and Oceanic Technology, 24, 20932102.

Lourens, L. J., Hilgen, F. J., Laskar, J., Shackleton, N. J. and Wilson, D. 2004. The NeogenePeriod. In: F. Gradstein, J. Ogg, and A. Smith (eds.),A Geological Timescale 2004, CambridgeUniv. Press, Cambridge, U. K., 409440.

MacLeod, K.G. 1994. Extinction of inoceramid bivalves in Maastrichtian strata of the Bay ofBiscay region of France and Spain. Journal of Paleontology, 68, 1048-1066.

MacLeod, K.G. and Orr, W.N. 1993. The taphonomy of Maastrichtian inoceramids in the BasqueRegion of France and Spain and the pattern of their decline and disappearance. Paleobiology,19, 235250.

Mary, C., Moreau, M.G., Orue-Etxebarria, X., Apellaniz, E. and Courtillot, V. 1991. Biostratigraphyand magnetostratigraphy of the Cretaceous/Tertiary Sopelana section (Basque Country). Earthand Planetary Science Letters, 106, 133150.

Mathey, B., 1982. El Cretcico del Arco Vasco. In: Garca, E. (ed.), El Cretcico de Espaa.Universidad Complutense de Madrid, 111135.

Molina, E., Alegret, L., Arenillas, I., Arz, J.A., Gallala, N., Grajalese Nishimura, M., Murilloe


20/24

Muetn, G., Zaghbibe Turki, D. 2009. The Global Boundary Stratotype Section and Point for thebase of the Danian Stage (Paleocene, Paleogene, Tertiary, Cenozoic): auxiliary sections andcorrelation. Episodes, 32, 8495.

Moreau, M.G., Cojan, I., Ory, J. 1994. Mechanisms of remanent magnetization in marl andlimestone alternations. Case study: Upper Cretaceous (Chron 3130), Sopelana, BasqueCountry. Earth and Planetary Science Letters 123, 1537

Mount, J.J., Ward, P.D. 1986. Origin of l imestone/marl alternations in the Upper Maastrichtian ofZumaya, Spain. Journal of Sedimentary Petrology, 56, 228236.

Paillard, D., Labeyrie, L. and Yiou, P. 1996. Macintosh program performs time-series analysis,EOS Trans. AGU, 77, 339.

Paul, C.R.C. and Lamolda, M.A. 2007. Carbon and oxygen stable isotopes in the Maastrichtian ofthe Basque Country, N. Spain. Cretaceous Research, 28, 812820.

Perch-Nielsen, K. 1985. Mesozoic calcareous nannofossils. In: Bolli, H.M., Saunders, J.B., andPerch-Nielsen, K. (eds.), Plankton Stratigraphy. Cambridge Univ. Press, Cambridge, 329426.

Plaziat, J.C. 1981. Late Cretaceous to Late Eocene palaeogeographic evolution of southwestEurope. Palaeogeography, Palaeoclimatology, Palaeoecology, 36, 263293.

Posamentier, H. W. and Vail, P. R. 1988. Eustatic control on clastic deposition II- Sequence andSystem Tract models. In: Wilgus C.K. et al., (eds.), Sea-Level Changes: an integrated approach.SEPM (Society of Economic Paleontologists and Mineralogists) Special Publication, 42, 125154.

Pujalte, V., Baceta, J.I., Payros, A., Orue-Etxebarria, X. and Serra-Kiel, J. 1994. Late Cretaceous-Middle Eocene Sequence Stratigraphy and Biostratigraphy of the SW. and W. Pyrenees(Pamplona and Basque Basins, Spain), 118 pp., GEP /IGCP 286 Field Seminar Guide-Book,Basque Country Univ., Bilbao.

Pujalte, V., Baceta, J.I., Dinars-Turell, J., Orue-Etxebarria, X. Pars, J.M. and Payros, A.1995.Biostratigraphic and magnetostratigraphic intercalibration of late Maastrichtian and Paleocenedepositional sequences from the deep-water Basque basin, W Pyrenees, Spain. Earth andPlanetary Science Letters, 136, 1730.

Roth, P. H. 1978. Cretaceous nannoplankton biostratigraphy and oceanography of northwesternAtlantic Ocean. Initial Reports of the DSDP, 44, 731-760.

Schmitz, B., Pujalte, V., Molina, E., Monechi, S., Orue-Etxebarria, X., Speijer, R.P., Alegret, L.,Apellaniz, E., Arenillas, I., Aubry, M-P, Baceta J.I., Berggren, W.A., Bernaola, G., Caballero, F.,Clemmensen, A., Dinars-Turell, J., Dupuis, C., Heilmann-Clausen, C., Hilario Ors, A., Knox,R., Martn-Rubio, M., Ortiz, S., Payros, A., Petrizzo, M.R., Sprong, J., Steurbaut, E. and Thomsen,E. 2011. The global stratotype sections and points for the bases of the Selandian (MiddlePaleocene) and Thanetian (Upper Paleocene) stages at Zumaia, Spain. Episodes, 34, 220243.

Sissingh, W. 1977. Biostratigraphy of Cretaceous calcareous nannoplankton. Geologie enMijnbouw, 56, 37-65.

Ten Kate, W.G. and Sprenger, A. 1993. Orbital cyclicities above and below theCretaceous/Paleogene boundary at Zumaya (N Spain), Agost and Relleu (SE Spain).Sedimentary Geology, 87, 69101.

Thibault, N. 2010. Calcareous nannofossils from the boreal Upper Campanian-Maastrichtianchalk of Denmark. Journal of Nannoplankton Research, 31, 1, 39-56.


21/24

Thibault, N., Gardin, S., Galbrun, B. 2010. Latitudinal migration of calcareous nannofossil Miculamurus in the Maastrichtian: Implications for global climate change. Geology, 38, 203206.

Thibault, N., Husson, D., Harlou, R., Gardin, S., Galbrun, B., Huret, E. and Minoletti, F. 2012.Astronomical calibration of upper Campanian-Maastrichtian carbon isotope events andcalcareous plankton biostratigraphy in the Indian Ocean (ODP Hole 762C): implication for theage of the Campanian-Maastrichtian boundary. Palaeogeography, Palaeoclimatology,Palaeoecology, 337-338, 52-71.

Torrence, C. and Compo, G.P. 1998. A practical guide to wavelet analysis. Bulletin AmericanMeteorological Society, 79, 6178.

von Hillebrandt, A. 1965. Foraminiferen-Stratigraphie im Alttertir von Zumaia (prov. Guipuzcoa,NW Spanien) und ein Vergleich mit anderen Tethys-Gebieten. Abh. Kn. Bay, Akad. Wiss.Mnchen, 123, 163.

Varadi, F., Runnegar, B. and Ghil, M. 2003. Successive refinements in long-term integrations ofplanetary orbits.Astrophysical Journal, 592, 620630.

Ward, P.D., Wiedmann, J. and Mount, J.J. 1986. Maastrichtian molluscan biostratigraphy andextinction patterns in a Cretaceous/Tertiary boundary section exposed at Zumaya, Spain.Geology, 14, 899903.

Ward, P. D. 1988. Maastrichtian ammonite and Inoceramid ranges from the bay of BiscayCretaceous-Tertiary boundary sections. Revista Espaola de Paleontologa, n Extraordinario,Paleontology and Evolution: Extinction Events, 119126.

Ward, P.D., Kennedy,W.J., MacLeod, K.G. and Mount, J.F.1991. Ammonite and inoceramidbivalve extinction patterns in Cretaceous/Tertiary boundary sections of the Biscay region(southwestern France, northern Spain). Geology19, 11811184

Ward, P.D. and Kennedy, W.J. 1993. Maastrichtian ammonites from the Biscay Region (F

Rich Text Editor FileDetailed correlation and astronomical forcing across the Upper Maastrichtian...

Documents

Transcript of Rich Text Editor FileDetailed correlation and astronomical forcing across the Upper Maastrichtian...