Burial Preservation of Trace Fossils as Indicator of Storm Deposition

Anthony J. Martin

Positive semirelief epichnia (ridgelike trace fossils on the top surface of a bed) commonly represent burrow structures, perhaps originally supported by a mucoidal matrix, that have been infilled by sediment. The preservation of these structures, in addition to other trace fossils on a bed superface, suggests an instantaneous burial event and a minimum of concomitant erosion. This supposition can be verified by an absence or paucity of biogenic sedimentary structures accompanied by certain physical sedimentary structures (laminated shell hashes, graded bedding, fissile shales) in strata directly overlying bioturbated surfaces.

The main processes involved in this burial preservation (the rapid burial of biogenic sedimentary structures with minimum erosion) are probably storm-generated in most instances. Sediments would be deposited primarily in the suspension mode, and mean storm wave base would be slightly above the sediment-water interface. This burial preservation model is most applicable to relatively small stratigraphic intervals (several centimeters or decimeters) representing deposition on an open-marine shelf.

Positive semirelief epichnia, interpreted as burrow system infillings, from the Cincinnatian Series (Upper Ordovician) of Ohio and Indiana are used to illustrate these concepts.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.