FORAMINIFERA AND PALEOENVIRONMENT OF THE PLIO-PLEISTOCENE KALLITHEA BAY SECTION, RHODES, GREECE: EVIDENCE FOR CYCLIC SEDIMENTATION AND SHALLOW-WATER SAPROPELS
Published:July 13, 2005
Tine L. Rasmussen, Erik Thomsen, 2005. "FORAMINIFERA AND PALEOENVIRONMENT OF THE PLIO-PLEISTOCENE KALLITHEA BAY SECTION, RHODES, GREECE: EVIDENCE FOR CYCLIC SEDIMENTATION AND SHALLOW-WATER SAPROPELS", Lagoon to Deep-Water Formaminifera and Ostracods from the Plio-Pleistocene Kallithea Bay Section, Rhodes, Greece, Tine L. Rasmussen, Annette Hastrup, Erik Thomsen
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Nearly 250 species of benthic foraminifera have been identified from the Plio-Pleistocene strata of the Kallithea Bay section on the eastern coast of Rhodes. The section comprises an overall transgressive succession ranging from fluviatile and brackish-water gravel at the base to fine-grained deep-water marl at the top. The marine deposits are referred to the early Pleistocene, while the brackish-water deposits probably are of late Pliocene age. Variations in the abundance and distribution of the benthic foraminiferal species were examined in 61 samples. The brackish water strata contain a low diversity fauna dominated by Ammonia parkinsoniana and A. p. tepida. The marine deposits, in contrast, contain a rich fauna with an average number of species per sample close to eighty. Cluster analyses grouped the marine samples into four biofacies. The distribution of the individual biofacies is closely linked to lithofacies and to changes in the depositional environment. The most distinct environmental change is connected to an increase in water depth caused by a general subsidence of the island. Over a period of less than 500 kyr during the early Pleistocene, the water depth increased from a few meters to more than 400 m. Superimposed on this large-scale subsidence was a series of rapid environmental fluctuations. The fluctuations are shown by repeated shifts between fine-grained, laminated marls and coarse-grained calcarenites, and by parallel shifts in the benthic and planktonic assemblages. The fluctuations were apparently cyclic and they involved shifts between well-oxygenated and low-oxic to anoxic bottom-water conditions. The faunistic and environmental shifts show many similarities to the astronomically driven sapropel cycles from the deeper parts of the eastern Mediterranean, and the laminated beds in the Kallithea Bay section are interpreted as shallow water extensions of sapropels. The shallowest of the laminated beds were deposited at water depth around 75 m.