BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, researchlibraries, and research funders in the common goal of maximizing access to critical research.

New Species of Angiosperm Pollen from the Dakota Formation (Cenomanian,Upper Cretaceous) of Minnesota, U.S.AAuthor(s): Shusheng Hu, David M. Jarzen, and David L. DilcherSource: Palynology, 32(1):17-26. 2008.Published By: AASP: The Palynological SocietyURL: http://www.bioone.org/doi/full/10.2113/gspalynol.32.1.17

BioOne (www.bioone.org) is an electronic aggregator of bioscience research content, and the online home to over160 journals and books published by not-for-profit societies, associations, museums, institutions, and presses.

Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance ofBioOne’s Terms of Use, available at www.bioone.org/page/terms_of_use.

Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiriesor rights and permissions requests should be directed to the individual publisher as copyright holder.

S. Hu, D.M. Jarzen, and D.L. Dilcher: New species of Cenomanian angiosperm pollen, Cenomanian of Minnesota, U.S.A. 17NEW SPECIES OF ANGIOSPERM POLLEN FROM THEDAKOTA FORMATION (CENOMANIAN, UPPERCRETACEOUS) OF MINNESOTA, U.S.A.

SHUSHENG HUPaleobotany and Palynology LaboratoryFlorida Museum of Natural HistoryUniversity of FloridaGainesville, Florida 32611-7800, U.S.A.current address: Department of BiologyIndiana University SoutheastNew Albany, Indiana 47150, U.S.A.e-mail: hus@ius.edu

DAVID M. JARZENDAVID L. DILCHERPaleobotany and Palynology LaboratoryFlorida Museum of Natural HistoryUniversity of FloridaGainesville, Florida 32611-7800, U.S.A.e-mail: dmj@flmnh.ufl.edu; dilcher@flmnh.ufl.edu

Abstract

Five new species of angiosperm pollen described from three localities in south-central Minnesota support a Cenomanian age for the DakotaFormation in this area. The new taxa, Cupliferoidaepollenites microscabratus, Dryadopollis minnesotensis, Nyssapollenites microfoveolata,Phimopollenites striolata, and Tricolpites labeonis, are described using both light and scanning electron microscopy, are easilyrecognizable, and are useful age indicator species. Because of the extent and transgressive nature of the Dakota Formation, agedetermination has been difficult. The new angiosperm pollen species described here may help to support age determination for the DakotaFormation over a broader geographic area.

Key words: Late Cretaceous, Cenomanian, Dakota Formation, angiosperm pollen, taxonomy, biostratigraphy, paleoecology.

Palynology, 32 (2008): 17–26© 2008 by AASP Foundation ISSN 0191-6122

INTRODUCTION

The Dakota Formation is a lithostratigraphic unit acrossa vast area of central and west-central North America (Ravnand Witzke, 1995). The name has often been used withoutconsideration of the type Dakota Formation, eitherlithostratigraphically or chronostratigraphically (Witzke etal., 1983). Therefore the age and lithology of the DakotaFormation are probably not the same from the west marginto the east margin of the Western Interior Seaway. Cur-rently, the age of the Dakota Formation in southwestMinnesota is thought to be Cenomanian (Setterholm, 1994).However, because of the absence of marine fossils, thissuggestion of a Cenomanian age has mainly been basedupon interpretations from the paleobotanical work of

Lesquereux (1895), and the palynological studies of Pierce(1961). The paleofloras of Lesquereux (1895) and thepalynofloras of Pierce (1961) require reexamination andreinterpretation (Upchurch and Dilcher, 1990; Wang, 2002;Hu et al., 2004). Austin (1972) proposed that the nonmarineCretaceous sediments in the Minnesota River Valley areapproximately middle Cenomanian based upon clay min-eralogy. Setterholm (1994) further proposed that the uppermudstone unit of the Dakota Formation in east-centralMinnesota may be coeval with the Graneros Shale inwestern Minnesota, and that both units are late Cenoma-nian.

Hu (2006) examined the palynofloras from the DakotaFormation of three clay pits in southern Minnesota. TheCretaceous sediments from these clay pits provide a rich

18 PALYNOLOGY, VOLUME 32 — 2008

and diverse assemblage of palynomorphs, allowing refine-ment of the age (Hu, 2006). This paper is based on Hu(2006), and describes five new angiosperm pollen speciesidentified from the Dakota Formation, and discusses theirimplications for age determination.

GEOLOGIC SETTING

During the Early Cretaceous, two epicontinental seas,the Boreal in the north and the Gulf in the south, werepresent on continental North America. The Boreal Seaadvanced southward, meeting the northward-advancingGulf Sea (Obradovich and Cobban, 1975) to form theWestern Interior Seaway. This was a continuous sea ex-tending from the Arctic to the Gulf of Mexico across NorthAmerica during the late Albian (Witzke and Ludvigson,1996). The Western Interior Seaway was transgressiveduring the late Albian to the Cenomanian; it was borderedto the west by the Cordilleran thrust belt, and on the east bythe cratonic platform (Dyman et al., 1994).

The type area of the Dakota Formation is located alongthe Missouri River in northeastern Nebraska and north-western Iowa (Ravn and Witzke, 1995). The Dakota For-mation is a sequence of nonmarine to marginal marinefacies that are the oldest Cretaceous sediments in south-western Minnesota (Witzke and Ludvigson, 1994). It in-cludes two lithostratigraphic units, the lower sandstoneunit and the upper mudstone unit; these are respectivelysimilar to the Nishnabotna and Woodbury members of theDakota Formation in age and lithology (Setterholm, 1994).The age of the Dakota Formation in southwest Minnesotais currently thought to be Cenomanian (Setterholm, 1994).

Courtland Clay Pit (localities UF 19006, UF 19007)

The sediments at Courtland Clay Pit (Nicollet County,MN, 44°16'29" N, 94°23'13" W) are dominated by lami-nated mudstone. Hajek et al. (2002) interpreted the sedi-mentary environment as a large lake based upon the milli-meter to centimeter scale laminae, scattered, well-pre-served leaves, and siderite (FeCO3) concretions. LakeDrummond (36°36'12'' N, 076°28'06'' W) in Virginia is atypical coastal lake, and may represent a similar environ-ment to sediments of this Cretaceous lake exposed atCourtland Clay Pit.

Highway 4 Clay Pit (locality UF 19000)

The sediments at Highway 4 Clay Pit (Brown County,MN, 44°26'05" N, 94°43'37" W) consist predominantly oftabular cross-bedded sandstone and carbonaceous siltstone.Hajek et al. (2002) interpreted the sedimentary environ-

ment as a tidally influenced meandering river system basedon inclined heterolithic stratification and tabular cross-bedded fine-grained sandstone. Oxbow lakes, ridge andswale, and levee are important environments associatedwith meandering river systems.

Ochs Clay Pit (locality UF 15750)

The sediments at Ochs Clay Pit (Brown County, MN,44°13'26" N, 95°00'42" W) are dominated by silty mud-stone and siltstone. Sloan (1964) indicated that the sedi-ments below a prominent lignite layer probably represent alacustrine environment, based on the varved mudstone andabundant leaf fossils. By contrast, the sediments above thelignite layer probably represent an estuarine environment,based upon silty and sandy mudstone, and several sharkvertebrae. The lignite may represent the distal side of thecoastal swamp, which is not close to active beach barriersystems. The lowermost lacustrine sediments at Ochs ClayPit appear to represent a low-energy lake paleoenviron-ment (Twenhofel, 1932; Visher, 1965).

The sediments at these three clay pits in southwesternMinnesota are isolated from each other. It is difficult tomake correlations between these three pits based uponlithology. Leaf megafossils are not satisfactory for com-parative dating between these localities because a DakotaFormation leaf biostratigraphy has not been formulated.However, plant microfossils including pollen and sporesare abundant in these sediments, and pollen has beensuccessfully used for stratigraphic zonations of the Da-kota Formation in other areas (Brenner et al., 2000).Based on the frequent occurrences of Fraxinoipollenitesconstrictus, Liliacidites reticulatus, Phimopollenitesstriolata, and Tricolpites cf. vulgaris, in sample UF 19007-036710 at Courtland Clay Pit, sample UF 19000-046517at Highway 4 Clay Pit, and sample UF 15750-046522 atOchs Clay pit, these sediments are coeval. It is thereforepossible to make stratigraphic comparisons between thethree clay pits.

MATERIALS AND METHODS

Samples were collected from the Courtland Clay Pit, theHighway 4 Clay Pit, and the Ochs Clay Pit in southwesternMinnesota by Shusheng Hu in 2003 and 2004 (Text-Figure1). Five stratigraphic sections were measured (Text-Figure2). Pollen samples were collected at about 30 cm intervalsfrom each of these sections. Standard processing tech-niques were used for all samples (Traverse, 2007). At theCourtland Clay Pit, 23 samples were collected; nine sampleswere processed of which eight samples contained abundantpalynomorphs. At Highway 4 Clay Pit, 12 samples were

S. Hu, D.M. Jarzen, and D.L. Dilcher: New species of Cenomanian angiosperm pollen, Cenomanian of Minnesota, U.S.A. 19

collected; eight samples were processed, with three samplesproviding abundant palynomorphs. At the Ochs Clay Pit,27 samples were collected, from which eight samples wereprocessed, with seven samples having abundant palyno-morphs. All the samples were processed at the Paleobotanyand Palynology Laboratory at the Florida Museum ofNatural History (FLMNH), Gainesville, Florida, U.S.A. Atleast two slides of each sample were scanned in order tobuild a catalogue of pollen and spore morphotypes. Pollencounts were of at least 300 palynomorphs, and were madeusing a ZEISS Axiophot™ microscope. An AxioCam™digital camera and imaging capturing software were usedfor the palynomorph identification and photography. Scan-ning electron microscopy was carried out using a HitachiS4000™ field emission scanning electron microscope(SEM) at the Department of Botany, University of Florida.Pollen and spore identifications were made by comparisonwith images and descriptions in the literature (e.g. Agasie,1969; Brenner, 1963; Doyle and Robbins, 1977; May andTraverse, 1973; Pierce, 1961; Ravn, 1981; Ravn and Witzke,1995; Romans, 1975), and the holotypes of Hedlund (1966),in the Sam Noble Oklahoma Museum of Natural History,Norman, Oklahoma, U.S.A.

Slides, residues, SEM stubs, and unprocessed samplesare deposited at the Paleobotany and Palynology Labora-tory, Florida Museum of Natural History, Gainesville,Florida, U.S.A., as localities UF 15750, UF 19000, UF19006, and UF 19007. The locations of the specimensillustrated in Plates 1 and 2 are given by reference to the

Paleobotany and Palynology Locality, the FLMNH (UFnumber), followed by a specimen number, with a slidenumber (PY01….PY…n). The microscope stage coordi-nates are listed as the England Finder Slide (EFS) locations.

SYSTEMATIC PALEONTOLOGY

Anteturma POLLENITES Potonié 1931Turma PLICATES Naumova 1939 emend. Potonié 1960

Subturma TRIPTYCHA Naumova 1939emend. Potonié 1960

Genus CupuliferoidaepollenitesPotonié et al. 1950 ex Potonié 1960

Text-Figure 1. Map of Minnesota illustrating the locationof the three sites studied.

Text-Figure 2. Stratigraphic sections of the five measuredsections from the three clay pits studied in Minnesota.The sections are arranged in relative stratigraphic posi-tion to each other. Note the vertical centimeter scale tothe right. The horizontal distances between the sectionsare not to scale.

20 PALYNOLOGY, VOLUME 32 — 2008

Type species Cupuliferoidaepollenites liblarensis(Thomson in Potonié et al., 1960) Potonié 1960

Cupuliferoidaepollenites microscabratus sp. nov.Plate 1, figs. 1–4

Diagnosis. Pollen grains free, isopolar; subprolate, pro-late to perprolate (P/E=1.25–2.38), amb circular tosubcircular; tricolpate, colpi nearly extending to the poles,somewhat thickened colpi margins, apocolpia small; exinethin, ca. 0.6–1.0 µm, two-layered, nexine thin, sexinebaculate, forming a microreticulate sculpture, lumina en-circling 3–5 capita, sexine supratectally scabrate.

Dimensions. Equatorial view 7(11)17 x 10(16)25 µm(10 grains); polar view 12(16)22 µm (5 grains).

Holotype. UF 15750-046522-PY01A, EFS X45.Remarks. Psilatricolpites psilatus Pierce (1961) is larger,

measuring 21 x 29 µm.Occurrence. Courtland Clay Pit and Ochs Clay Pit.Name derivation. The specific epithet, microscabratus,

is derived from the supratectal scabrate sexine.

Genus Tricolpites Cookson 1947 ex Couper 1953emend. Jarzen & Dettmann 1989

Type species Tricolpites reticulatus Cookson 1947 bysubsequent designation of Couper 1953

Tricolpites labeonis sp. nov.Plate 1, figs. 5–9

Diagnosis. Pollen grains free, isopolar; subprolate, pro-late (P/E=1.21–2.00), amb circular to subcircular; tricolpate,colpi nearly extending to the poles, apocolpia small; exinethin, ca. 0.5 µm, ?two-layered, sexine columellate, pilashort; microreticulate, lumina less than 0.5 µm. SEMstudies have shown that there is about a 0.7 µm wide marginalong the colpi on which the lumina are small (less than 0.1µm in diameter), and rare or absent. As this feature is not

observed under transmitted light microscopy, the surface isconsidered evenly reticulate over its entire surface, andtherefore is included in Tricolpites.

Dimensions. Equatorial view 6(10)14 x 9(14)19 µm (14grains); polar view 18 µm (1 grain).

Holotype. UF 15750-046526-PY03A, EFS Y37.Remarks. Jarzen and Dettmann (1989), following Ward

(1986), emended the diagnosis of Tricolpites to includetricolpate grains with a regular (homobrochate) reticulumof uniform size measuring <1 µm in diameter over theentire surface of the grain. Gunnerites and Retitricolpitesare considered junior synonyms of Tricolpites. Tricolpiteslabeonis is similar to Tricolpites minutus (Brenner 1963)Dettmann 1973 (see Dettmann, 1973) in size and orna-mentation, but it is differentiated from Tricolpites minutusby its narrow margin along the colpi on which the luminaare reduced or absent. Tricolpites labeonis sp. nov. issimilar in shape, size, and ornamentation to in situ pollenof early to middle Albian flowers described as Aquiabrookensis from the ‘Bank near Brooke’ locality, Virginia(Crane et al., 1993), but differs in lacking the verrucosesurface of colpi membranes in the pollen of Aquiabrookensis.

Occurrence. Courtland Clay Pit and Ochs Clay Pit.Name derivation. The specific epithet, labeonis, means

one with large lips, based on the appearance of the marginsof the colpi as seen using the SEM (Plate 1, fig. 8).

Subturma PTYCHOTRIPORINES Naumova 1939

Genus Dryadopollis Srivastava 1975

Type species Dryadopollis argus Srivastava 1975

Dryadopollis minnesotensis sp. nov.Plate 1, figs. 10–15

Diagnosis. Pollen grains free, isopolar; prolate spheroi-dal, subprolate to prolate (P/E=1.11–1.88), tricolporate,

1–4 Cupuliferoidaepollenites microscabratus sp. nov. 1:holotype, single grain, mid-focus. UF 15750-046522-PY01A, X45. 2: UF 15750-046522-PY01A, Q18/4,pollen clump. 3: SEM, UF 19007-036708 stub 12,pollen clump. 4: as 3, detail of surface of single grain.

5–9 Tricolpites labeonis sp. nov. 5, 6: holotype, singlegrain at high and mid-focus levels respectively, UF15750-046526-PY03A, Y37. 7: SEM UF 15750-46533, stub 3, scale bar = 2 µm. 8: UF 15740-46533

PLATE 1

The scale bar represents 10 µm unless otherwise noted.

stub 3, scale bar = 2 µm. 9: UF 15750-46533-PY03A,R35/1 pollen clump.

10–15 Dryadopollis minnesotensis sp. nov. 10: UF 19007-036708 >10 µ, N36, mid-focus, pollen clump. 11: UF19007-036708 >10 µ, M35/1, mid-focus, pollen clump.12: holotype, UF 19006-036694-PY01A, S31/1, highfocus. 13: as 12 mid-focus. 14: SEM, UF 19007-036708, stub 12, pollen clump. Scale bar = 6 µm. 15: as14, close-up of the pore. Scale bar = 1 µm.

S. Hu, D.M. Jarzen, and D.L. Dilcher: New species of Cenomanian angiosperm pollen, Cenomanian of Minnesota, U.S.A. 21Plate 1

22 PALYNOLOGY, VOLUME 32 — 2008

apocolpia small; exine 1 µm, ?two-layered, sexine col-umellate, pila short; microreticulate, lumina 0.1–1.0 µm,muri ca. 0.5 µm wide, lumina decreasing toward colpi andpoles (heterobrochate of Ward, 1986, p. 25), ora small,about 0.8 µm in diameter.

Dimensions. Equatorial view 8(15)19 x 15(19)23 µm (5grains); polar view 16(17)19 µm (13 grains).

Holotype. UF19006-036694-PY01A, EFS S31/1.Remarks. Srivastava (1975) erected Dryadopollis to

accommodate tricolporate pollen with a reticulum that isfiner at the apocolpia and colpi margins than in themesocolpal regions. This species is distinct fromDryadopollis argus, and Dryadopollis vestalis Ward 1986,in its smaller lumina and ora, and thinner exine.

Occurrence. Courtland Clay Pit.Name derivation. The specific epithet, minnesotensis,

is derived from Minnesota, where the fossil pollen wasrecovered.

Genus Phimopollenites Dettmann 1973

Type species Phimopollenites pannosus (Dettmann &Playford 1968) Dettmann 1973

Phimopollenites striolata sp. nov.Plate 2, figs. 1–8

Diagnosis. Pollen grains free, isopolar; prolate spheroi-dal, subprolate to prolate (P/E=1.06–1.62), amb circular tosubcircular; tricolporoidate, colpi slightly ragged and thick-ened, apocolpia small; exine 1–2 µm, two-layered, nexinethinner than sexine, sexine columellate, pila dense; sexinemicroreticulate, lumina less than 0.5 µm. SEM studiesshow the muri to be composed of closely spaced capitawhose apical ends protrude supratectally, and give theappearance of a striate muri surface (Plate 2, fig. 8).

Dimensions. Equatorial view 12(14)19 x 16(19)21 µm(10 grains); polar view 15(18)24 µm (7 grains).

Holotype. UF 19006-046517-A1, >10 µm, EFS N29/3.

Remarks. This species has a striate structure (muri withweak, transverse striations), that is different from otherspecies of Phimopollenites when seen under the SEM.

Occurrence. Courtland Clay Pit, Highway 4 Clay Pit,and Ochs Clay Pit.

Name derivation. The specific epithet, striolata, isdiminutive for furrow, as the muri appear to be furrowed(Plate 2, fig. 8).

Genus Nyssapollenites Thiergart 1937

Type species Nyssapollenites pseudocruciatus (Potonié1931) Thiergart 1937

Nyssapollenites microfoveolata sp. nov.Plate 2, figs. 9–15

Diagnosis. Pollen grains free, isopolar; prolate spheroi-dal, subprolate to prolate (P/E=1.00–1.56), amb roundedtriangular; tricolporate, colpi nearly extending to the poles,colpi with thickened margins, pore ca. 1 µm, apocolpiasmall; exine ca. 0.8–1.0 µm, ?two-layered; sexine scabrateto microfoveolate, foveolae small, <1 µm.

Dimensions. Equatorial view 9(11)14 x 11(14)17 µm (7grains); polar view 11(14)15 µm (3 grains).

Holotype. UF 15750-046533-PY03A, EFS W30/3.Occurrence. Courtland Clay Pit and Ochs Clay Pit.Remarks. This species is distinct from Nyssapollenites

albertensis Singh 1971, which has a larger and thickenedpore (ca. 2.5 µm in diameter), thickened colpi margins, anda scabrate (not microfoveolate) exine. Tricolporopollenitestriangularis Groot et al. 1961 is psilate.

Name derivation. The specific epithet, microfoveolata,is derived from the fine foveolate surface.

DISCUSSION

The five new pollen species described herein provideadditional information on the age of the Dakota Formation

PLATE 2

The scale bar represents 10 µm unless otherwise noted.

1–8 Phimopollenites striolata sp. nov. 1–3: holotype, singlegrain, near polar view, high, mid and low focus respec-tively, UF 19006-046517-A1 >10 µ, N29/3. 4, 5: singlegrain, equatorial view, high and low focus respectively,UF 19006-046517-A1, >10 µ, R22/1. 6: pollen clump,UF 19006-046517-A1, >10 µ, F14. 7: SEM, UF 19007-046517 stub 1, polar view. Scale bar = 2 µm. 8: as 7,detail of pollen surface, showing the closely spacedcapita giving the striate appearance to the muri. Scalebar = 1 µm.

9–15 Nyssapollenites microfoveolata sp. nov. 9–11: holo-type, UF 15750-046533-PY03A, W30/3, high, mid andlow focus respectively. 12, 13: UF 15750-046533-PY03A, X42, equatorial view, mid and low focusrespectively. 14: SEM UF 15750-046533 stub 3. Scalebar = 2 µm. 15: as 14, detail of aperture region andsurface ornamentation, showing the microreticulate tofoveolate surface pattern. Scale bar = 1 µm.

S. Hu, D.M. Jarzen, and D.L. Dilcher: New species of Cenomanian angiosperm pollen, Cenomanian of Minnesota, U.S.A. 23Plate 2

24 PALYNOLOGY, VOLUME 32 — 2008

in south central Minnesota. Several pollen taxa have tradi-tionally been used to determine the age of non-marinesediments within the Dakota Formation (Nichols, 1994).Nyssapollenites microfoveolata sp. nov. is a key taxon forage dating. Nichols (1994) revised the palynostratigraphiczonation for the Upper Cretaceous non-marine sedimentsin the Rocky Mountain region of the United States, andproposed a scheme based upon a comparison with marineammonite zones. Nichols (1994) noted that the first occur-rence of psilate tricolporate pollen, such as Nyssapollenitesmicrofoveolata sp. nov. and obligate tetrads (e.g. Artiopollisindivisus Agasie 1969), are indicative of a middle Cenoma-nian to Coniacian age (Nichols and Sweet, 1993; Nichols,1994). Both Artiopollis indivisus and Nyssapollenitesmicrofoveolata sp. nov. occur in Ochs Clay Pit, andNyssapollenites microfoveolata sp. nov. occurs in CourtlandClay Pit (Hu, 2006). Based on these occurrences, thesediments in Courtland Clay Pit, Highway 4 Clay Pit andOchs Clay Pit are considered no older than late Cenoma-nian in age.

The megaspore Balmeisporites glenelgensis Cookson& Dettmann 1958 was found only in the lignite of OchsClay pit (Hu, 2006). This species also occurs in theCenomanian sediments in the Peace River area of north-western Alberta, Canada (Singh, 1971; 1983). Balmei-sporites glenelgensis also occurs in the Sergeant Blufflignite and the Stone Park lignite in northwestern Iowaand northeastern Nebraska. The age of these lignites wasdetermined to be middle to late Cenomanian (Ravn andWitzke, 1995). Based upon common Balmeisporitesglenelgensis, the lignite at the Ochs Clay Pit can becorrelated with the Sergeant Bluff lignite and Stone Parklignite. This suggests that the age of the lignite, and thesediments above the lignite, at Ochs Clay Pit are probablymiddle Cenomanian. By comparison with Singh (1983),Nichols (1994), and Ravn and Witzke (1995), the age ofthe sediments in Courtland Clay Pit, Highway 4 Clay Pit,and Ochs Clay Pit is middle Cenomanian.

The new species described in this paper provide newinformation on the diversity of angiosperms during theCenomanian. Although angiosperm diversification wasapparently rapid (Lidgard and Crane, 1988; Upchurchand Dilcher, 1990), triporate pollen had not evolved bythe middle Cenomanian at the three clay pits studiedherein.

ACKNOWLEDGMENTS

Appreciation is expressed to Karen Kelley and LyndaSchneider for SEM technical assistance. Scott Gooler andTerry Lott are recognized for their help during the 2003 and2004 field seasons. Financial support was provided by:

Dilcher-Becker Funds, 2003; Evolving Earth Foundation,2004 grant; Sigma Xi Grant In Aid of Research, 2004;Graduate Student Council of the University of Florida forTravel Grants, 2003 and 2004; Danker Fund, 2004, fromthe Department of Geological Sciences, University ofFlorida; and the Deep Time Project, NSF DEB-0090283.Hongshan Wang helped in finding locality data. We thankthe Minnesota land owners for allowing collection ofsamples from their properties. Susan A. Jarzen assisted inmanuscript preparation. We are very grateful for the com-ments and suggestions made by Douglas J. Nichols andSatish K. Srivastava as reviewers, and to James B. Ridingfor his editorial skills.

References Cited

AGASIE, J.M.1969 Late Cretaceous palynomorphs from northeastern

Arizona. Micropaleontology, 15: 13–30.AUSTIN, G.S.

1972 Precambrian Sioux Quartzite and Cretaceous rocksof southern Minnesota. Field trip guidebook forPaleozoic and Mesozoic rocks of southeastern Min-nesota, p. 55–63.

BRENNER, G.J.1963 The spores and pollen of the Potomac Group of

Maryland. Maryland Department of Geology, Minesand Water Resources Bulletin, No. 27, 215 p.

BRENNER, R.L., LUDVIGSON, G.A., WITZKE, B.J.,ZAWISTOSKI, A.N., KVALE, E.P., RAVN, R.L., andJOECKEL, R.M.

2000 Late Albian Kiowa–Skull Creek marine transgres-sion, lower Dakota Formation, eastern margin ofWestern Interior Seaway, U.S.A. Journal of Sedi-mentary Research, 70(4): 868–878.

CRANE, P.R., PEDERSEN, K.R., FRIIS, E.M., and DRINNAN,A.N.

1993 Early Cretaceous (Early to Middle Albian) Platanoidinflorescences associated with Sapindopsis leavesfrom the Potomac Group of eastern North America.Systematic Botany, 18(2): 328–334.

DETTMANN, M.E.1973 Angiospermous pollen from Albian to Turonian sedi-

ments of eastern Australia. Geological Society ofAustralia Special Publication, 4: 3–34.

DOYLE, J.A., and ROBBINS, E.I.1977 Angiosperm pollen zonation of the continental Cre-

taceous of the Atlantic Coastal Plain and its applica-tion to deep wells in the Salisbury Embayment.Palynology, 1: 43–78.

DYMAN, T.S., COBBAN, W.A., FOX, J.E., HAMMOND, R.H.,NICHOLS, D.J., PERRY, W.J., PORTER, K.W., RICE, D.D.,

S. Hu, D.M. Jarzen, and D.L. Dilcher: New species of Cenomanian angiosperm pollen, Cenomanian of Minnesota, U.S.A. 25

SETTERHOLM, D.R., SHURR, G.W., TYSDAL, R.G., HALEY,J.C., and CAMPEN, E.B.

1994 Cretaceous rocks from southwestern Montana tosouthwestern Minnesota, northern Rocky Mountains,and Great Plains region. In: Shurr, G.W., Ludvigson,G.A., and Hammond, R.H. (eds.). Perspectives onthe eastern margin of the Cretaceous Western Inte-rior Basin. The Geological Society of America In-corporated, p. 5–26.

GROOT, J.J., PENNY, C.R., and GROOT, C.R.1961 Plant microfossils and age of the Raritan, Tuscaloosa

and Magothy formations of the eastern United States.Palaeontographica Abteilung B, 108: 121–140.

HAJEK, E., ROGERS, R.R., SETTERHOLM, D.R., andGOOLER, S.

2002 Large lakes and tidally influenced rivers in the lateCretaceous of southwestern Minnesota. GeologicalSociety of America Annual Meeting 2002, Denver,Abstracts with programs, 279 (abstract).

HEDLUND, R.W.1966 Palynology of the Red Branch Member of the Wood-

bine Formation (Cenomanian), Bryan County, Okla-homa. Oklahoma Geological Survey, The Univer-sity of Oklahoma, Norman, 69 p.

HU, S.2006 Palynomorphs and selected mesofossils from the

Cretaceous Dakota Formation, Minnesota, U.S.A.Unpublished PhD Dissertation, University of Florida,Gainesville, U.S.A., 217 p.

HU, S., DILCHER, D.L., and JARZEN, D.M.2004 The palynological assemblages from Courtland Clay

Pit, Minnesota. Geological Society of America An-nual Meeting 2004, Abstracts with Programs, 527(abstract).

JARZEN, D.M., and DETTMANN, M.E.1989 Taxonomic revision of Tricolpites reticulatus

Cookson ex Couper, 1953 with notes on the biogeog-raphy of Gunnera L. Pollen et Spores, 31: 97–112.

LESQUEREUX, L.1895 Cretaceous fossil plants from Minnesota. Geological

and Natural History Survey of Minnesota, 3: 1–22.LIDGARD, S., and CRANE, P.R.

1988 Quantitative analyses of the early angiosperm radia-tion. Nature, 331: 344–346.

MAY, F.E., and TRAVERSE, A.1973 Palynology of the Dakota Sandstone (Cenomanian)

near Bryce Canyon National Park, southern Utah.Geoscience and Man, 7: 57–64.

NICHOLS, D.J.1994 A revised palynostratigraphic zonation of the non-

marine Upper Cretaceous, Rocky Mountain region,United States. In: Caputo, M.V., Peterson, J.A., and

Franczyk, K.J. (eds.). Mesozoic Systems of the RockyMountain Region, U.S.A. The Rocky Mountain Sec-tion, Society for Sedimentary Geology, Denver, p.503–522.

NICHOLS, D.J., and SWEET, A.R.1993 Biostratigraphy of Upper Cretaceous nonmarine pa-

lynofloras in a north–south transect of the WesternInterior Basin, In: Caldwell, W.G.E., and Kauffman,E.G., (eds.). Evolution of the Western Interior Basin.Geological Association of Canada Special Paper,39: 539–584.

OBRADOVICH, J.D., and COBBAN, W.A.1975 A time-scale for the late Cretaceous of the Western

Interior of North America. In: Caldwell, W.G.E.(ed.). The Cretaceous System in the Western Interiorof North America, The Geological Association ofCanada Special Paper No. 13: 31–54.

PIERCE, R.L.1961 Lower Upper Cretaceous Plant Microfossils from

Minnesota. The University of Minnesota, MinnesotaGeological Survey Bulletin, No. 42, 86 p.

RAVN, R.L.1981 Preliminary observations on the palynology of upper

Dakota Formation lignites in northwest Iowa andnortheast Nebraska. In: Brenner, R.L., Bretz, R.F.,Bunker, B.J., Ludvigson, G.A., McKay, R.M., Whit-ley, D.L., Witzke, B.J., Cobban, W.A., Merewether,E.A., Ravn, R.L., and Shurr, G.W. (eds.). Cretaceousstratigraphy and sedimentation in northwest Iowa,northeast Nebraska, and southeast South Dakota.North-Central Section, Geological Society ofAmerica, Iowa Geological Survey Guidebook Se-ries, 4: 123–127.

RAVN, R.L., and WITZKE, B.J.1995 The palynostratigraphy of the Dakota Formation

(?Late Albian–Cenomanian) in its type area, north-western Iowa and northeastern Nebraska, U.S.A.Palaeontographica Abteilung B, 234: 93–171.

ROMANS, R.C.1975 Palynology of some Upper Cretaceous coals of Black

Mesa, Arizona. Pollen et Spores, 17: 273–329.SETTERHOLM, D.R.

1994 The Cretaceous rocks of southwestern Minnesota:Reconstructions of a marine to nonmarine transitionalong the eastern margin of the Western InteriorSeaway. In: Shurr, G.W., Ludvigson, G.A., andHammond, R.H. (eds.). Perspectives on the easternmargin of the Cretaceous Western Interior basin. TheGeological Society of America Incorporated, Boul-der, p. 97–110.

SINGH, C.1971 Lower Cretaceous microfloras of the Peace River

26 PALYNOLOGY, VOLUME 32 — 2008

area, northwestern Alberta. Bulletin of the ResearchCouncil of Alberta, 28(1): 1–299.

1983 Cenomanian microfloras of the Peace River area,northwestern Alberta. Bulletin of the Research Coun-cil of Alberta, 44: 1–322.

SLOAN, R.E.1964 The Cretaceous System in Minnesota. University of

Minnesota, Minneapolis, 64 p.SRIVASTAVA, S.K.

1975 Microspores from the Fredericksburg Group (Al-bian) of the southern United States. PaléobiologieContinentale, 6(2): 1–119.

TRAVERSE, A.2007 Paleopalynology. Second Edition. Springer, The

Netherlands, xviii + 813 p.TWENHOFEL, W.H.

1932 Treatise on sedimentation. Williams and WilkensCompany, Baltimore, 926 p.

UPCHURCH, G.R., and DILCHER, D.L.1990 Cenomanian angiosperm leaf megafossils, Dakota

Formation, Rose Creek locality, Jefferson County,Southeastern Nebraska, U.S. Geological Survey Bul-letin, No. 1915, 55 p..

VISHER, G.S.1965 Use of vertical profile in environmental reconstruc-

tion. American Association of Petroleum GeologistsBulletin, 49: 41–61.

WANG, H.2002 Diversity of angiosperm leaf megafossils from the

Dakota Formation (Cenomanian, Cretaceous), NorthWestern Interior, U.S.A. Unpublished PhD Disserta-tion, University of Florida, Gainesville, U.S.A., 395 p.

WARD, J.V.1986 Early Cretaceous angiosperm pollen from the Chey-

enne and Kiowa Formations (Albian) of Kansas,U.S.A. Palaeontographica Abteilung B, 202: 1–81.

WITZKE, B.J., and LUDVIGSON, G.A.1994 The Dakota Formation in Iowa and the type area. In:

Shurr, G.W., Ludvigson, G.A., and Hammond, R.H.(eds.). Perspectives on the eastern margin of theCretaceous Western Interior Basin. The GeologicalSociety of America Incorporated, 43–78.

1996 Coarse-grained eastern facies. In: Witzke, B.J., andLudvigson, G.A. (eds.). Mid-Cretaceous fluvial de-posits of the eastern margin, Western Interior Basin:Nishnabotna Member, Dakota Formation. A fieldguide to the Cretaceous of Guthrie County. IowaDepartment of Natural Resources, 19–30.

WITZKE, B.J., LUDVIGSON, G.A., POPPE, J.R., and RAVN,R.L.

1983 Cretaceous palaeogeography along the eastern mar-gin of the western Interior Seaway, Iowa, southern

Minnesota, and eastern Nebraska and South Dakota.In: Reynolds, M.W., and Dolly, E.D. (eds.). Meso-zoic paleogeography of the west-central United States.Society of Economic Paleontologists and Mineralo-gists, Denver, 225–252.