GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 38-27
Presentation Time: 9:00 AM-5:30 PM


BUNTIN, Rogers C.C., Department of Geology, University of Kansas, 1475 Jayhawk Blvd., Lawrence, KS 66045 and HASIOTIS, Stephen T., Department of Geology, University of Kansas, Lawrence, KS 66045

Teredolites provide ichnological evidence of marine incursion and flooding surfaces in Mesozoic and younger stratigraphic successions when wood supply was adequate for colonization by pholadoidean bivalves (Teredinidae and Pholadidae: Xylophagaidae, Martesiinae, Pholadinae). Teredolites are frequently misinterpreted in the reconstruction of marine-influenced paleoenvironments with respect to: (1) lateral changes of salinity concentrations and media supply in estuaries which impact boring size; and (2) residence times within undesirable salinity ranges. Modern wood-boring clams inhabit oligohaline to euhaline environments forming diverse metacommunities with specialized reproductive styles to compensate for: (1) sympatric competition, (2) ephemeral media supply, (3) dispersal capability of sessile adults. Oviparous, short-term larviparous, and long-term larviparous species specialize within separate paralic and open marine environments, with highest sympatric competition occurring within ecotones. Broadcast spawning and brooding have a direct correlation to overall body size in benthic sessile invertebrates, free-spawning species grow significantly larger than brooding species to facilitate much larger clutch sizes. Oviparous species dominate in proximal coastal plain and open marine environments by utilizing current transport and a long planktonic larval period. Brooding species dominate estuarine and nearshore systems by exploiting consistent media supply and short larval periods, relying on rafting of adults for regional dispersal. We have investigated the environmental factors which control the size, distribution, and abundance of modern wood-boring bivalves in paralic to open marine environments and have reflected these trends onto fossilized Teredolites using a robust spatio-temporal data set. Our objectives are to: (1) utilize the ichnological signature of reproductive styles to quantify salinity-size relationships in the rock record, (2) better understand palichnological community dynamics and subsequent correlation to species diversity, (3) develop predictability of paleoenvironments based on group mean metrics, and (4) identify evolutionary trends in the Mesozoic based on the ichnogeny of larval and adult boring sizes and densities.