| Abstrakt: |
This paper reports the fauna and distribution of large-sized benthic foraminifers ( LsBFs; defined as benthic foraminifers >0.5 mm in size) from surface sediments collected around Tahiti, French Polynesia, as well as from the Pleistocene deposits drilled off the Tiarei area, Tahiti, during Integrated Ocean Drilling Program ( IODP) Expedition 310. At least 6 and 22 genera of living and dead tests of LsBFs, respectively, were identified from modern surface sediments. Foraminiferal abundance in surface sediments depends mainly on the water depth and substratum type. The taxonomic composition of dead LsBF assemblages varies with depositional environments and water depths. Back-reef lagoon assemblages are dominated by Schlumbergerina alveoliniformis, whereas fore-reef slope and shelf assemblages are dominated by Amphistegina spp. The relative abundance of Amphistegina lessonii decreases with increasing water depth. On the shelf, A. lessonii is replaced by Amphistegina bicirculata and Planostegina sp. Pleistocene samples consisting mainly of volcaniclastic sandstone/siltstone and skeletal grainstone contained very small numbers and low species diversity of fossil LsBFs. Amphistegina lobifera, Heterostegina depressa, and Eponides repandus were commonly found in the Pleistocene samples. The taxonomic compositions showed little variation within holes. The Pleistocene assemblages were compositionally similar to those found in modern fore-reef slope environments of <30 m depth. Combined results of coral U/ Th ages and paleoenvironmental interpretations from in situ corals and LsBFs indicate that the Pleistocene sequence in the Tiarei area was deposited in a fore-reef slope environment during Marine Isotope Stage 3. [ABSTRACT FROM AUTHOR] |
Plný text