Environmental significance of abundant and diverse hornwort spores in a potential submerged Paleoindian site in the Gulf of Mexico

Abstract

A palynological analysis of sediments sampled from core HI-178, offshore High Island, Texas, provided a diverse and well-preserved palynoflora. The main objective was to analyze the environmental conditions at time of deposition. A secondary objective was to evaluate whether or not this site might have been occupied by Native Americans by looking for signs of human-driven changes in vegetation. Here we focus on the abundance of hornwort spores recovered from these samples, review their diversity, compare the fossil spores to modern analogues and discuss the paleoenvironmental implications of hornwort abundance. Although no direct evidence of human occupation was found, the pollen and spore assemblage recovered, marked by high abundance and diversity in spores of hornworts belonging to the families Anthocerotaceae and Notothyladaceae, indicate that this site was most likely not submerged at the time of deposition; human occupation was therefore possible. This site represents a coastal low-lying area with ponds or slow-moving waters that provided the humid environment needed for hornworts to reproduce and thrive under warm climatic conditions.

Keywords:

• palynology
• Gulf of Mexico
• Holocene
• Anthoceros
• Phaeoceros
• hornwort

Acknowledgements

The authors would like to thank the Bureau of Ocean Energy Management, Regulation, and Enforcement (BOEMRE) (formerly Minerals Management Service) for funding this project (Cooperative Agreement/Award No. MO7AC13373 to P. Hesp). We are indebted to Dr Robert Ireland (currently with the Smithsonian Institution, Washington, DC) for guiding DMJ through the collection of modern Anthocerotophyta from vouchered herbarium material at CANM (Ottawa, Canada). Appreciation is expressed to the Collection staff at the Canadian Museum of Nature (Ottawa) and especially to Richard Day and Margaret Currie for the loan of Anthocerotophyta prepared spore slides and residues. Further, we extend our thanks to Dr Dana Griffin III and Kurt M. Neubig (Florida Museum of Natural History, Gainesville, Florida) for their assistance in obtaining photographs of living Anthoceros. Brooks Ellwood, Graziela Miot da Silva and Barun Sen Gupta (Department of Geology and Geophysics at LSU) were instrumental in assisting and advising this study. Susan Jarzen assisted in manuscript and slide preparation. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the opinions or policies of the US Government. Mention of trade names or commercial products does not constitute their Endorsement by the US Government.