CARBONATE SEQUENCE STRATIGRAPHY ACROSS A

MIDDLE JURASSIC PLATFORM TO BASIN TRANSECT, SOUTHERN

ENGLAND.

THOMAS BUTT

WHY STUDY THE SEQUENCE STRATIGRAPHY IN THE COTSWOLDS

AIM: TO ASSESS THE CARBONATE SEQUENCE STRATIGRAPHY OF THE MID-JURASSIC ACROSS A COTSWOLD NE-SW PLATFORM TO BASIN TRANSECT

WHY: TO DETERMINE IF THE PATTERN OF SEDIMENTATION IN THIS INTERVAL IS DRIVEN BY REGIONAL PRODUCTION VARIATION IN THE CARBONATE SYSTEM OR BY GLOBAL BASE LEVEL CHANGES.

JURASSIC ENVIRONMENTS

Barron et Al. 2012

BASIN - PLATFORM TRANSECT

Barron et Al. 2012

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DATA COLLECTION

• COLLECTED LOGS AND SAMPLES FROM HORNSLEASOW QUARRY• LOGGED FOUR OTHER BGS BOREHOLE SITES:

• WINTERBORNE KINGSTON 1 • BIDDESTONE• CHIPPING NORTON 5 • UPWOOD

DATA ANALYSIS

• QUARTZ GRAIN ABUNDANCE ANALYSIS • OOID ANALYSIS• MICROFACIES ANALYSIS• MICROPALAEONTOLOGICAL AND PALAEONTOLOGICAL ANALYSIS

SEA LEVEL COMPARISON

• SEA LEVEL WAS COMPARED TO THE HAQ ET AL. (1987), HALLAM (1988) AND HASSELBO (2008) CURVES.

• THE BEST MATCH WAS WITH THE HASSELBO (2008) CURVE• PROBLEMS OCCUR WITH AMOUNT OF SEA LEVEL RISE.

CONCLUSIONS

• A MIXED SILICICLASTIC AND CARBONATE SHELF ENVIRONMENT• THE SEQUENCE STRATIGRAPHY, AND THUS SEA LEVEL, RECORDED

ACROSS THE TRANSECT SHOWS THIRD AND FOURTH ORDER CYCLICITY. • THIRD ORDER CYCLICITY IS CONTROLLED BY REGIONAL TECTONIC EVENTS,

POSSIBLY FROM AN UPWELLING MAGMA PROVINCE IN THE ATLANTIC. • FOURTH ORDER CYCLICITY HAS ITS MAIN INFLUENCES WITH THE OBLIQUITY

AND PROCESSION MILANKOVITCH CYCLES. • THERE WAS NO REGIONAL PRODUCTION VARIATION OF NOTE THAT

WOULD HAVE AFFECTED THE SEA LEVEL CHANGE IN THE SEDIMENTARY DEPOSITS. THEREFORE THE REGIONAL PRODUCTION VARIATION IS DRIVEN BY SEA LEVEL CHANGES.

ANY QUESTIONS?

REFERENCES• BARRON, A. J. M., LOTT, G. K., RIDING, J. B., 2012. STRATIGRAPHICAL FRAMEWORK

FOR THE MIDDLE JURASSIC STRATA OF GREAT BRITAIN AND THE ADJOINING CONTINENTAL SHELF. BRITISH GEOLOGICAL SURVEY RESEARCH REPORT, RR/11/06. 187PP.

• COX, B. M., 1990. A REVIEW OF JURASSIC CHRONOSTRATIGRAPHY AND AGE INDICATORS FOR THE UK. GEOLOGICAL SOCIETY, LONDON, SPECIAL PUBLICATIONS, V.55; P169-190.

• HALLAM, A., 1988. A RE-EVALUATION OF JURASSIC EUSTASY IN THE LIGHT OF NEW DATA AND THE REVISED EXXON CURVE. IN: WILGUS, C.K., HASTINGS, B.S., KENDALL, C.G.ST.C., POSAMATIR, H.W., RON, C.A., VAN WAGNER, J.C. (EDS.), SEA-LEVEL CHANGES Ð AN INTEGRATED APPROACH. SEPM SPECIAL PUBLICATION, 42, PP. 261-273.

• HAQ, B.U., HARDENBOL, J., VAIL, P.R., 1987. CHRONOLOGY OF FLUCTUATING SEA LEVELS SINCE THE TRIASSIC (250 MILLION YEARS AGO TO PRESENT). SCIENCE 235, 1156-1167.

• HESSELBO, S., P. 2008. SEQUENCE STRATIGRAPHY AND INFERRED RELATIVE SEA-LEVEL CHANGE FROM THE ONSHORE BRITISH JURASSIC. PROCEEDINGS OF THE GEOLOGISTS' ASSOCIATION, 119, 19-34.

• METCALF, S. J., VAUGHAN, R. F., BENTON, M. J., COLE, J., SIMMS, M. J. & DAARTNALL, D. L. 1992. A NEW BATHONIAN (MIDDLE JURASSIC) MICROVERTEBRATE SITE WITHIN THE CHIPPING NORTON LIMESTONE FORMATION AT HORNSLEASOW QUARRY, GLOUCESTERSHIRE. PROCEEDINGS OF THE GEOLOGISTS' ASSOCIATION, 103, 321-342.