Degree Year

2000

Document Type

Thesis

Degree Name

Bachelor of Arts

Department

Geology

Advisor(s)

Karla Parsons-Hubbard

Keywords

Biological oceanography, Biology, Animal physiology, Geology, Marine geology

Abstract

The fields of Paleontology and Paleoecology would not be complete without taphonomy, the study of the processes affecting organisms between death and fossilization. Taphonomy is important because it allows us to make more complete conjectures about prehistoric organisms and environments, and makes us aware of possible holes and biases in the fossil record due to highly destructive processes or the loss of delicate, non-resistant organisms. Studies on the processes affecting modern organisms have contributed greatly to the understanding of ancient processes; however, most of these studies are nearshore and short-term. What is lacking is information on the effects of these factors over long periods of time, and to depths below 50 meters. To gain more information about long-term effects, the Shelf and Slope Experimental Taphonomy Initiative (SSETI) has deployed sets of crabs, molluscs, urchins, and wood on a variety of substrates at depths from 15 to 300 meters in the Bahamas. Sample groups have been collected every few years for the last six years, and are compared to control sets.

My research focuses specifically on the crabs, species Callinectes sapidus, from experimental sites in the Bahamas. The crab remains display a wide range of breakage, dissolution and disarticulation, varying by depth. To determine the effects of depth and environment on the crab remains, changes in size, mass, and surface condition of each of the specimens was documented and the results were analyzed for trends across a depth gradient. Scanning electron microscope analysis of carapace surface conditions was conducted to determine the degree of dissolution of each specimen.

The crabs were reduced to disarticulated chelipeds, mandibles, and carapace fragments within one year in most environments, and the outer surfaces of the remains show near-complete loss of pigmentation, and microscopic pitting. Although the sample sizes in this experiment are fairly small, a trend of better preservation in the middle depths and worse preservation at shallow and deep sites was found. Since this taphonomic trend exists, the information gleaned from this study may prove to be useful in accurately identifying the depth ranges in which fossil assemblages were created.

Included in

Geology Commons

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