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dc.contributor.authorCarroll, Monicaen
dc.date.accessioned2014-03-14T20:42:16Zen
dc.date.available2014-03-14T20:42:16Zen
dc.date.issued2001-07-12en
dc.identifier.otheretd-07312001-115131en
dc.identifier.urihttp://hdl.handle.net/10919/34270en
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
dc.publisherVirginia Techen
dc.relation.haspartfig3,2.pdfen
dc.relation.haspartfig4,1.pdfen
dc.relation.haspartThesis.pdfen
dc.relation.haspartfig3,1.pdfen
dc.relation.haspartfig2,1.pdfen
dc.relation.haspartfig5,2.pdfen
dc.relation.haspartfig4,4.pdfen
dc.relation.haspartfig4,3.pdfen
dc.relation.haspartfig4,2.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectBouchardia roseaen
dc.subjectTerebratulid Brachiopodsen
dc.subjectFossil recorden
dc.subjectAmino Acid Racemization Datingen
dc.subjectTaphonomyen
dc.titleQuantitative Estimates of Time-Averaging in Brachiopod Shell Accumulations from a Holocene Tropical Shelf (SW Brazil)en
dc.typeThesisen
dc.contributor.departmentGeological Sciencesen
dc.description.degreeMaster of Scienceen
thesis.degree.nameMaster of Scienceen
thesis.degree.levelmastersen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.disciplineGeological Sciencesen
dc.contributor.committeechairKowalewski, Michalen
dc.contributor.committeememberBambach, Richard K.en
dc.contributor.committeememberSchreiber, Madeline E.en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-07312001-115131/en
dc.date.sdate2001-07-31en
dc.date.rdate2002-08-06en
dc.date.adate2001-08-06en


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