Biogenic Structures in Upper Devonian Storm Deposits in Catskill Deltaic Complex, New York
Molly F. Miller
Trace fossils and biogenic structures are moderately abundant in sandstones of the Genesee Group. These rocks are well exposed in a quarry at Gilbert Lake State Park, east-central New York, where they are interpreted as storm deposits. The biogenic structures give important information about the behavior of Devonian animals colonizing the freshly deposited sediment. Within the sandstones, trace-fossil diversity is low. The most abundant trace fossil is a small (1 mm diameter) branching burrow system (?Chondrites). Other common forms are vertical to horizontal meniscate burrows, horizontally oriented spreite-bearing forms (?Rhizocorallium-?Zoophycos), and vertical burrows (Skolithos). Except for Skolithos, the trace fossils are highly variable morphologically ( e.g., the m nsicate burrows apparently pass laterally into ?Rhizocorallium-?Zoophycos). Commonly, the top 8-10 cm of inferred storm deposits are highly bioturbated, whereas the lower 20-25 cm typically are undisturbed. ?Chondrites extends to depths more than 20 cm below the top of the burrowed zone, implying that its producer burrowed to equivalent depths. Two generalizations about the behavior of Devonian animals colonizing storm deposits can be made. (1) Their behavior was changeable, as indicated by diverse orientations and morphologic variability of the trace fossils. (2) They had a moderately deep infaunal habit, indicated by the abundance of burrowing in the top 8-10 cm of storm deposits.
AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.