Techniques for Studying Biogenic Structures
Published:January 01, 1984
Biogenic structures are manifestations of the activities of benthic organisms and, as such, can be viewed not only as biologic entities but also as sedimentary structures. Consequently, special methods may be necessary in order to study them properly. Farrow (1975) provided an excellent summary of the techniques presently used in studying fossil and recent traces; these are summarized in Tables IV-1 and IV-2.
(1) Field observations. Perhaps the most fundamental technique used in studying trace fossils is simple detailed observation. Trace fossils in some cases are very difficult to collect, because they require the recovery of large rock slabs or, when dealing with cores, sampling may be prohibited. Therefore, it becomes imperative to describe the fossils in the field with as much accuracy and precision as possible. Various field forms or checklists have been devised by some workers to ensure that important details are not overlooked.
Accurate sketches and/or good photographs are virtually mandatory. Simple field sketches have the advantage of being easy, inexpensive and not dependent upon good lighting; moreover, a sketch always contains the pertinent features that may not show up in a photograph because of low contrast, small size or poor photography. Disadvantages, of course, are that sketching is a time-consuming, practiced skill that varies considerably from one person to another. Photographs, on the other hand, are very quick to produce (a fraction of second!) and are objective in the final result. However, important details often cannot be captured effectively on film if the lighting is imperfect
Figures & Tables
Ichnology: The Use of Trace Fossils in Sedimentology and Stratigraphy
Ichnology is a fascinating field of endeavor. As with science in general, it is a process of solving mysteries–in this case, mysteries of fossil behavior. In a very real sense the ichnologist is Sam Spade or Sherlock Holmes–following footprints, searching for traces of dastardly deeds, studying artifacts, attempting to reconstruct a sequence of events from subtle clues, pursuing the identity of someone (or something) long dead. Who was the culprit? What was he/she doing? Where was he/she living, working or going? Not only intellectually intriguing, ichnology also has practical application and economic importance. In today’s frenzied quest for energy and mineral resources, exploration geologists value every tool that aids their search. Ichnologic observations and analyses can help the sedimentologist reconstruct ancient depositional environments, help the stratigrapher correlate sedimentary strata, help the paleontologist determine the nature of fossil communities, and help the geochemist determine the effect of organisms on sediment composition. This publication was written to serve as a comprehensive and intelligible introduction to ichnology for anyone with even rudimentary geologic training, whether or not that person enrolls in a formal course on the subject. The book emphasizes sedimentologic, stratigraphic and paleoecologic al aspects of ichnology.