Macroborings in Otodus megalodon and Otodus chubutensis shark teeth from the submerged shelf of Onslow Bay, North Carolina, USA: implications for processes of lag deposit formation

Abstract

The shallow continental shelf in the Cape Fear Region of southwestern Onslow Bay, North Carolina, contains lag deposits with an abundance of megatoothed shark teeth belonging to Otodus megalodon (Agassiz 1835) and Otodus chubutensis (Ameghino 1906) that derive from the Pliocene Yorktown and Miocene Pungo River formations, respectively. These teeth exhibit different frequencies and orientations of macroborings identified as Gastrochaenolites torpedo Kelly and Bromley (1984), Gastrochaenolites lapidicus Kelly and Bromley (1984), Maeandropolydora sulcans Voigt (1965) and ?Entobia isp. attributed to endolithic bivalves, serpulid worms and clionaid sponges. Different frequencies and orientations of macroborings seen in lag deposits containing O. megalodon and O. chubutensis teeth are the result of repeated exhumation and reworking in response to bathymetrically controlled wave-based erosion during storm events and glacioeustatically driven sea-level cyclicity across Onslow Bay. Chronological ranges of O. megalodon and O. chubutensis teeth that contain macroborings indicate that these lag deposits may have been forming since the late early Miocene.

Keywords:

• Macroborings
• fossil shark teeth
• Otodus megalodon
• Otodus chubutensis
• Onslow Bay
• North Carolina

Acknowledgements

This manuscript is dedicated to B. Major (1965–2018) for introducing us to the submerged Onslow Bay lag deposits and assisting with fossil collection over the last decade. We also thank S. M. Major, S. A. Major, J. Crain and B. Karasik for assistance with field work and for allowing us to review their fossil collections from the submerged shelf lag deposit localities. In addition, we gratefully thank R. Scimeca for assistance with graphic designs, and Captains J. Christopher and D. Hatcher (JetLag Charters), Z. Dewitt (CDA 1; Megateeth Fossils), R.S. Jenkins (Poseidon Adventures), D. Smithey and K. Blackmon (Carolina Beach SCUBA) and R. Young for diving assistance and marine transportation. T. Daeschler and E. Gilmore are thanked for creating a repository for specimens at ANSP. Lastly, we appreciate the review and comments of M. Wisshak, M. Gingras, C. Kline, L. Buatois and an anonymous reviewer which improved an earlier version of this manuscript. This research was supported in part by a CUNY Doctoral Student Research Grant awarded to HMM, PSC-CUNY research awards to JAC, and an NSF Sedimentology and Paleobiology Award 1830581 to MAB.

Disclosure statement

No potential conflict of interest was reported by the authors.