Holocene Paleohydrology of Little Salt Spring, Florida, Based on Ostracod Assemblages and Stable Isotopes

Authors

Carlos A. Alvarez Zarikian, University of Miami
Peter Koenraad Swart, University of Miami
John A. Gifford, University of Miami
Patricia Blackwelder, University of Miami; Nova Southeastern UniversityFollow

Document Type

Article

Publication Date

8-5-2005

Publication Title

Palaeogeography, Palaeoclimatology, Palaeoecology

Keywords

Ostracods, Stable isotopes, Little salt spring, Florida, Holocene, Sinkhole, Paleohydrology

ISSN

0031-0182

Volume

225

Issue/No.

1-4

First Page

134

Last Page

156

Abstract

Ostracod assemblages and the δ¹⁸O and δ¹³C records of Cytheridella ilosvayi provide a ∼12,000 yr paleohydrological reconstruction of Little Salt Spring, a sinkhole lake and underwater archaeological preserve in west central Florida. The ostracod record documents relative changes in water temperature and hydrologic characteristics of the lacustrine system that are the result of warming air temperatures, changes in the relative contributions of input waters (shallow vs. deep groundwater), rainfall patterns and relative sea level rise during the Holocene. The data indicate that LSS was initially supplied by relatively low amounts of direct rainfall and surface runoff as the spring's location was closer to the recharge area and far from the freshwater/saltwater interface. At about 11,000 yr BP, LSS became groundwater supported, initially by a shallow freshwater aquifer with low δ¹⁸O composition until ∼5700 yr BP, and after that time by ¹⁸O-enriched and increasingly mineralized groundwater originating from a deeper, carbonate aquifer as the regional water table rose bringing the saltwater interface closer to the location of LSS which at this time was becoming a groundwater discharge area. The data also shows that the most abrupt and pronounced hydrologic changes occurred during the Late Holocene with an interval of low δ¹⁸O values (∼− 2.86‰) between 2700 and 2000 yr BP, followed by a stepped increase in δ¹⁸O composition with maximum values (∼− 1.46‰) between 1100 and 900 yr BP. Over these periods to the present time the ostracod assemblage is characterized by brackish species (Cyprideis spp. and Limnocythere floridensis). It is inferred that the interval of decreased isotopic values indicates mixing with saline water during dry climatic conditions, while the interval of more enriched isotopic values suggest saltwater intrusion during a period of, presumably, a sea level highstand. Although some discrepancies exist between other records from the northern Caribbean region and the one from LSS with regards to the exact timing for the Late Holocene drying and subsequent increase in rainfall conditions, the differences between the records may be explained by greater continental influences on ocean–atmosphere interactions on the Florida peninsula, a highly complex groundwater mixing balance in LSS, and by a better constrained age-model in the other records.

Comments

©2005 Elsevier B.V. All rights reserved.

Additional Comments

National Geographic Society grant #: 4217-89

NSUWorks Citation

Carlos A. Alvarez Zarikian, Peter Koenraad Swart, John A. Gifford, and Patricia Blackwelder. 2005. Holocene Paleohydrology of Little Salt Spring, Florida, Based on Ostracod Assemblages and Stable Isotopes .Palaeogeography, Palaeoclimatology, Palaeoecology , (1-4) : 134 -156. https://nsuworks.nova.edu/occ_facarticles/440.

DOI

10.1016/j.palaeo.2004.01.023