Taphonomic signature as a function of environmental process : sedimentation and Taphofacies of shell concentration layers and "event beds", Holocene of Texas /
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| Other Authors: | , , , , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1988.
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| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | Standardized criteria for taphonomic processes, including dissolution, breakage, abrasion, size sorting, and shell orientation, were statistically correlated against environmental parameters representing shell source, depositional environment, and time since buried, for samples from a Texas microtidal inlet. Results from this taphofacies were then compared with accumulations from Texas bays and continental shelf. A model was developed for the 'event' deposition of shell beds for a clastic passive margin; it was evaluated in several modem and ancient deposits. Inlet sediments were differentiated by cluster analysis into eight classes based on their percent carbonate and percent shell gravel content. Boundaries between classes represent thresholds in physical processes. This classification scheme may be useful for field descriptions in many depositional and tectonic settings. Death assemblages were predominately whole and fragmental molluscan shells. Most shells shew the effects of physical taphonomic processes (shell breakage, rounding, surface abrasion, and size sorting). Major environments (estuary, bay, inlet, and continental shelf) are distinguished on the basis of shell taphonomic signature. A mixed fauna from the inlet showed patterns of dissolution, breakage, and abrasion differing significantly on shells derived from different habitats. Thus, a shell's habitat, rather than its final depositional environment, controlled most aspects of its taphonomic signature, except for shell orientation and size-frequency distribution. Statistical tests refuted that a high energy "event" (hurricane) imprints a unique taphonomic signature; it merely winnows and concentrates shell material. Whole shells more accurately reflect the proximate depositional environment; conversely, fragments portray more thoroughly the range of taphonomic processes producing a taphofacies. Most shell dissolution occurs at the sediment surface. Rates of shell production vs. dissolution indicate that shell material usually is preserved by rapid "event" burial; shell beds normally cannot form on the sediment surface. Such a quantified taphonomic approach is useful in paleoecological analysis, showing that "taphofacies" reflect not only the final depositional process, but also the taphonomic processes in the habitat of origin. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Geology." |
| Physical Description: | xvi, 243 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |