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The AAPG/Datapages Combined Publications Database

GCAGS Transactions


Gulf Coast Association of Geological Societies Transactions
Vol. 44 (1994), Pages 764-764

Abstract: Comprehensive, Quantitative Micropaleontological Previous HitAnalysisNext Hit as a Tool for Previous HitPaleoenvironmentalNext Hit Interpretation and Sequence Stratigraphy, with an Example from the Yegua Formation, Southeast Texas

Martin B. Lagoe (1), Thomas B. Layman (2)


Traditional industrial approaches to biostratigraphy and Previous HitpaleoenvironmentalNext Hit Previous HitanalysisNext Hit largely use only a small portion of the available microfossil assemblage, concentrating on various marker taxa ("tops" of index fossils and Previous HitpaleoenvironmentalNext Hit guide fossils). Sequence stratigraphic approaches may place more emphasis on the entire assemblage, but efficient analytical strategies still need to be developed to extract maximum information from micropaleontological data. Microfossil assemblages are produced by three types of processes: (1) in situ accumulation of taxa living at the sample site; (2) postmortem transport of specimens into and out of the sample site ("downslope transport"), and (3) taphonomic/diagenetic processes such as dissolution, which can alter taxon proportions. Recognizing and evaluating the effects of these processes on the microfossil assemblage can lead to a better geological interpretation. We propose an analytical strategy to address these issues, consisting of (1) bulk faunal descriptors (faunal abundance, preservation, diversity, planktic microfossil abundance) combined with lithologic information (e.g., abundance of glauconite) to identify broad Previous HitpaleoenvironmentalNext Hit patterns; (2) biofacies definition based on cluster Previous HitanalysisNext Hit and factor Previous HitanalysisNext Hit of the entire microfossil data set to refine these patterns; (3) interpretation and modeling of biofacies trends using detrended reciprocal averaging, and (4) Previous HitanalysisNext Hit of faunal mixing patterns using polytopic vector Previous HitanalysisNext Hit. We apply this analytical strategy to foraminiferal data from the middle Eocene Yegua Formation of southeast Texas. Seven biofacies are recognized along a short, three-well dip transect, representing paleoenvironments ranging from marginal marine delta plain to outer neritic muddy shelf. The detailed "Previous HitpaleoenvironmentalNext Hit fabric" defined by these biofacies helps to delineate genetic sequence boundaries, higher frequency cyclicity, and aspects of depositional systems and paleoenvironments that are not apparent from Previous HitanalysisTop of well logs and marker fossils alone.

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(1) Department of Geological Sciences, The University of Texas at Austin, Austin, TX 78712

(2) Exxon Co. USA, 802 Stanolind Ave., Midland, TX 79705

Copyright © 1999 by The Gulf Coast Association of Geological Societies