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dc.contributor.authorCarroll, Monicaen_US
dc.date.accessioned2014-03-14T20:42:16Z
dc.date.available2014-03-14T20:42:16Z
dc.date.issued2001-07-12en_US
dc.identifier.otheretd-07312001-115131en_US
dc.identifier.urihttp://hdl.handle.net/10919/34270
dc.description.abstractTime-averaging, the mixing of fossils of different ages within a single bed, defines the limit of temporal resolution of the fossil record. Quantitative estimates of this resolution threshold have not been acquired for any group other than mollusks. This study provides the first quantitative estimates of time-averaging for brachiopods, extending our understanding of intrinsic, or group specific controls on this process. Estimates were obtained by direct dating of individual terebratulid brachiopod shells Bouchardia rosea (Mawe) collected from modern surficial shelly accumulations in the Southeast Brazilian Bight (SW Atlantic).

Using amino acid racemization dating calibrated with radiocarbon, 82 individual brachiopod shells, collected from four nearshore localities, were dated. The shells vary in age from modern to 3000 years, standard deviation = 680 years. The age distribution is significantly right-skewed (K3=2.48). At 50-year resolution, the temporal completeness is 75% for the last 1000 years and declines to 20% completeness for 1000-2000 yr. BP. Preservational quality (taphonomy) of modern (<50 yr.) shells is statistically indistinguishable from that of older shells, demonstrating that shell taphonomy is not a good predictor of within-assemblage relative age. These results conform to previously published results for mollusks.

Therefore, brachiopods can show considerable time-averaging and this time-averaging can be on a scale similar to aragonitic mollusks despite the apparent lack of robustness of calcitic brachiopod shells. This suggests that the brachiopod fossil record can be notably time-averaged, but estimates of this mixing cannot be reliably deciphered from the taphonomic condition of shells.

en_US
dc.publisherVirginia Techen_US
dc.relation.haspartfig3,2.pdfen_US
dc.relation.haspartfig4,1.pdfen_US
dc.relation.haspartThesis.pdfen_US
dc.relation.haspartfig3,1.pdfen_US
dc.relation.haspartfig2,1.pdfen_US
dc.relation.haspartfig5,2.pdfen_US
dc.relation.haspartfig4,4.pdfen_US
dc.relation.haspartfig4,3.pdfen_US
dc.relation.haspartfig4,2.pdfen_US
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectBouchardia roseaen_US
dc.subjectTerebratulid Brachiopodsen_US
dc.subjectFossil recorden_US
dc.subjectAmino Acid Racemization Datingen_US
dc.subjectTaphonomyen_US
dc.titleQuantitative Estimates of Time-Averaging in Brachiopod Shell Accumulations from a Holocene Tropical Shelf (SW Brazil)en_US
dc.typeThesisen_US
dc.contributor.departmentGeological Sciencesen_US
dc.description.degreeMaster of Scienceen_US
thesis.degree.nameMaster of Scienceen_US
thesis.degree.levelmastersen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineGeological Sciencesen_US
dc.contributor.committeechairKowalewski, Michalen_US
dc.contributor.committeememberBambach, Richard K.en_US
dc.contributor.committeememberSchreiber, Madeline E.en_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-07312001-115131/en_US
dc.date.sdate2001-07-31en_US
dc.date.rdate2002-08-06
dc.date.adate2001-08-06en_US


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