Reworked Benthic Foraminifers from Site 802, East Mariana Basin, Western Equatorial Pacific

Abstract

Reworked shallow-water larger and deep-water calcareous benthic foraminifers were recovered from foraminiferal packstones and nannofossil chalks in Hole 802A. The autochthonous zeolitic pelagic claystone is characterized by late Campanian abyssal agglutinated foraminifers that allow correlation with the North Atlantic and the adjacent Pigafetta Basin. Assemblages of DendrophryalRhizammina in graded beds within the zeolitic claystone indicate reworking through entrainment in the flocculent E layer of turbidites, rather than recolonization following a biosiliceous event. Background sedimentation of the claystone took place below the carbonate compensation depth.The nannofossil chalk contains reworked lower bathyal to abyssal calcareous foraminifers of late Paleocene to early Miocene age. The topmost bed of the nannofossil chalk unit commences with an algal foraminiferal packstone containing Lepidocyclina sumatrensis, Heterostegina borneensis, Amphistegina hauerina, Asterigerina marshallana, and A. tentoria, which indicate that the source area was a shallow-water reef and allow the bed to be dated as early Miocene. The absence of obviously younger planktonic microfossils in the graded bed indicates that the resedimentation event was generally contemporaneous with original deposition and took place during an early Miocene global sea-level highstand.An early Miocene shallow-water assemblage is also seen in the graded beds at the base of a volcaniclastic turbidite sequence overlying the nannofossil chalks. Resedimentation of this unit was associated with volcanic activity some distance away.

Late Chattian Larger Foraminifera From the Prebetic Domain (Se Spain): New Data on Shallow Benthic Zone 23

“…Its presence in the late Chattian in the Middle East and the western Tethys would change the interpretation of its region of origin and reverse its migration route. However, the report of late Oligocene?-early Miocene A. hauerina from the Mariana Basin, in the western equatorial Pacific (ODP site 802, Wightman 1992) should be taken into account in biogeographic interpretations. ACKNOWLEDGMENTS This is a contribution to the Grup de Investigació Consolidat Geologia Sedimentària (2014 SGR 251), and the I+D+i Project CGL2015-69805-P (MINECO, FEDER, EU), and is part of an academic initiative to support research at the Faculty of Geology of the University of Barcelona financed by Repsol Exploración S.A. Logistic and financial support is greatly acknowledged.…”