Taphonomy and provenance
| Exploring for Oil and Gas Traps | |
| |
| Series | Treatise in Petroleum Geology |
|---|---|
| Part | Predicting the occurrence of oil and gas traps |
| Chapter | Applied paleontology |
| Author | Robert L. Fleisher, H. Richard Lane |
| Link | Web page |
| Store | AAPG Store |
Because the hard parts of dead organisms may act as sedimentary particles, fossils provide evidence of sedimentary processes, tectonic events, sediment source areas, burial processes, and diagenesis. Reworked fossils, however, may be difficult to recognize in cuttings or even in cores and outcrops.
Definition
Taphonomy is the study of the effect of sedimentary processes and diagenesis on the postmortem redistribution and preservation of the hard parts of organisms. A taphonomic study can help identify variations in provenance, or source area, of fossil-bearing sediments.[1]
Clues to reworking
Several characteristics of fossil deposits are clues to erosion, transport, and reworking of older fossils into younger basin fill:[2]
- Presence of species whose stratigraphic ranges do not overlap
- Presence of fossils from significantly different environments
- Significant differences in the quality and mode of fossil preservation
- Presence of organic matter with more than one level of maturation
- Presence of fossils in “transported” lithologies (e.g., turbidites)
- Significant differences in the mineralogy and alteration of hard parts
- Orientation of shells, particularly of megafossils (as opposed to microfossils), reflecting displacement from the original habitat
Applications of taphonomy
The recognition of reworked fossils helps to (1) assess reservoir continuity and (2) interpret depositional models of the source area and of the depositional environment of the source rock. Applications include the following:
- Recognizing unconformities
- Recognizing condensed sections
- Identifying facies and depositional environments
- Determining ages of sediment source terranes
- Determining timing of uplift and erosion
- Interpreting contemporaneous geology of source areas
- Recognizing contamination by drilling mud or cavings
- Generating paleocurrent models for sand transport
See also
- Stratigraphic and geographic distribution of fossils
- Temporal and environmental distribution of microfossils
- Biogeography
- Paleoclimatology
References
- ↑ Lawrence, D. R., 1979, Taphonomy, in Fairbridge, R., W., Jablonski, D., eds., The Encyclopedia of Paleontology: Stroudsburg, Pennsylvania, Dowden, Hutchinson and Ross, p. 793–799.
- ↑ Brett, C., E., 1990, Destructive taphonomic processes and skeletal durability, in Briggs, D., E., G., Crowther, P., R., eds., Palaeobiology: A Synthesis: Oxford, Blackwell Scientific Publications, p. 223–226.
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