Date of Degree

9-2018

Document Type

Dissertation

Degree Name

Ph.D.

Program

Earth & Environmental Sciences

Advisor

John Chamberlain, Jr.

Committee Members

Martin Becker

Joshua Cheng

Jennifer Cherrier

Subject Categories

Geology | Paleontology | Stratigraphy

Keywords

Miocene, Pliocene, Fossil Sharks, Onslow Bay, North Carolina, Taxonomy, Taphonomy, Bioerosion, K-Pg, Teredolites-bored driftwood, Malvern, Arkansas

Abstract

This dissertation is divided into four sections that feature assemblages of self-collected fossils recovered while SCUBA diving in Onslow Bay, North Carolina, and the Ouachita River near Malvern, Arkansas. Sections one through three focus on Cenozoic lamniform and carcharhiniform shark teeth, including those of large Otodus megalodon, collected from submerged, actively forming lag deposits adjacent to outcrops of the Miocene Pungo River and Pliocene Yorktown formations in Onslow Bay. Section one documents the submerged collecting localities and the taxonomy and biostratigraphic properties of the fossil shark teeth they contain. Section two documents bathymetric controls on the degree of taphonomic reworking and bioerosion of these shark teeth from shallower, intermediate, and deeper shelf localities in Onslow Bay. Section three identifies and utilizes bioerosion in megatoothed shark teeth in addition to radiocarbon dating of endolithic bivalves and corals to time the process of lag deposit formation. Section four consists of a research extension into the Gulf Coastal Plain of the USA and focuses on an assemblage of Teredolites-bored driftwood recovered from a fossiliferous lag deposit at the contact between the Arkadelphia Formation and Midway Group submerged in the Ouachita River near Malvern, Arkansas. This driftwood derives from a known Cretaceous-Paleogene (K-Pg) boundary section and features trace fossils similar to those occurring in megatoothed shark teeth from Onslow Bay. Although the Malvern lag deposit is geologically older than those actively forming in Onslow Bay, the processes of lag deposit formation are extremely similar. Lag deposits in both study areas contain diverse, time-averaged vertebrate fossil assemblages with a notable abundance of biostratigraphically significant and taphonomically distinct shark teeth, infrequent terrestrial elements, and accumulated in response to numerous storm events and sea level cyclicity. Moreover, the processes of lag deposit formation observed in the actively forming Onslow Bay lags provide a means to interpret and model the formation of similar deposits, including the Malvern K-Pg lag, preserved in the stratigraphic record. Results from this dissertation indicate that the process of vertebrate lag deposit formation: 1) occurs globally, 2) is independent of geologic age, and 3) is the product of numerous storm events, including impact generated tsunamis, and sea level cyclicity within shallow shelf stratigraphic sections.

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