Stephen T. Hasiotis¹

(1) Indiana State University, Terre Haute, IN

ABSTRACT: The Continental Ichnology Swiss Army Knife-a New and Innovative Tool in Reservoir Analysis for Delineating Stratigraphic Sequences, Interpreting Environments, and Understanding Paleoclimates

Research demonstrates that in terrestrial and freshwater ichnofossils can be very abundant contrary to "popular" belief. Continental environments, represented by alluvial, lacustrine, aeolian, and transitional-marine depositional systems, contain biota in varying degrees of diversity and abundance. The burrowing behavior of these organisms discriminate sub-environments within terrestrial and freshwater settings, varying from barren to intensely bioturbated intervals depending on the interaction of climate, tectonics, and sediment supply. Trace fossils--the tracks, trails, burrows, nests, and rooting structures-reflect the environmental factors that control the behavior and distribution of terrestrial and freshwater organisms. Many of these traces exhibit morphologies distinct from marine traces. The occurrence and distribution of continental trace fossils also reflects the pedogenic history of the units in which they occur, as well as the hydrologic setting of ancient landscape. The paleoclimatic setting, in turn, controls the ichnobiodiversity, pedogenesis, and the groundwater hydrologic profile. Ichnofossils can be used to interpret the interaction between sedimentation rates, short-term climatic fluctuations, and variations in local base level (i.e., accomodation space) through the history of a basin.

Understanding the morphology, distribution, and lateral and vertical tiering of continental trace fossils can assist geoscientists involved in field- and core-based studies that focus on facies identification, paleoenvironmental and paleoclimatic reconstructions, and sequence stratigraphic interpretations. Trace fossil identifications can make a difference when trying to delineate between floodplain, lacustrine, and marine deposits. Continental traces also identify paleosols and discontinuity surfaces that range from short- to long-term soil horizons that typically change laterally in character. Knowing the spatial and temporal relation between continental trace fossils and these significant surfaces and their conformable strata can make a difference in understanding and predicting reservoir connectivity and conductivity.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado