Paleogene Benthic Foraminifer Biostratigraphy and Paleoecology at Site 647, Southern Labrador Sea

Abstract

Benthic foraminifers were examined from the Paleogene of Ocean Drilling Program (ODP) Site 647 and Deep Sea Drilling Program (DSDP) Site 112 in the southern Labrador Sea. The Paleogene sequence of the deep Labrador Sea can be subdivided into seven assemblages, based on the ranges and relative abundance of characteristic taxa. The first oc currences (FOs) and last occurrences (LOs) of important benthic taxa are calibrated to a standard biochronology, by in terpolating from our age model for Site 647. The biostratigraphy of Site 647 is used to improve the age estimates of Site 112 cores. Fifteen microfossil events in Site 647 also are found in the sedimentary wedge along the Labrador Margin. A comparison of the probabilistic microfossil sequence from the Labrador Margin with that at Site 647 yields four isoch ronous benthic foraminifer LOs. Two new species are described from Sites 647 and 112: Hyperammina kenmilleri, Kaminski n.sp., and Ammodiscus nagyi Kaminski n.sp.Significant faunal turnovers are observed at the Ypresian/Lutetian and Eocene/Oligocene boundaries. The Ypresian/Lutetian boundary is characterized by a Glomospira-facies and is attributed to a rise in the CCD (carbonate com pensation depth) associated with the NP14 lowstand in sea level. The Eocene/Oligocene boundary is delimited by the LO of Spiroplectammina spectabilis and Reticulophragmium amplectens. The change from an Eocene agglutinated as semblage to a predominantly calcareous assemblage in the early Oligocene took place gradually, over a period of about 4 Ma, but the rate of change accelerated near the boundary. This faunal turnover is attributed to changes in the preser vation of agglutinated foraminifers, as delicate species disappeared first. Increasingly poorer preservation of aggluti nated foraminifers in the late Eocene to earliest Oligocene reflects the first appearance of cool, nutrient-poor deep wa ter in the southern Labrador Sea. The approximately coeval disappearance of agglutinated assemblages along the Lab rador Margin was caused by a regional trend from slope to shelf environments, accentuated by the "mid"-Oligocene lowstand in sea level.

The mid/late Eocene transition in the Eastern Carpathians (Romania) based on foraminifera and calcareous nannofossil assemblages

“…This taxon was men tioned to form acmes just above the Cre taceous/Paleogene bound ary in Gubbio, south ern Spain, and in the equa to rial At lan tic Kaminski, 1996, Kuhnt et al, 1998) in the Paleocene de pos its from the Cen tral North Sea basin and Lab ra dor Shelf (Gradstein et al, 1994). This al most monospecific as sem blage has been re ported from Late Eocene de pos its from At lan tic and west ern Tethyan re gions (Kaminski et al, 1989;Kaminski, 2005).…”

“…The biozones were de fined us ing the biozonation schemes of Mar tini (1971) and Varol (1998) for cal car e ous nannofossils, and of Bratu (1975), Geroch and Nowak (1984), Berggren et al (1995), Kaminski (2005) and Kaminski et al (1989) for foraminifera. The ag glu ti nated foraminifera taxa iden ti fied are listed in Ap pen dix 1*, while the cal car e ous nannofossils are The biostratigraphy used the biozonation schemes of Martini (1971) and Varol (1998) for calcareous nannofossils (N) and of Kaminski et al (1989), Kaminski (2005) and Bratu (1975) for foraminifera (F) listed in Ap pen dix 2.…”

“…The ag glu ti nated foraminifera taxa iden ti fied are listed in Ap pen dix 1*, while the cal car e ous nannofossils are The biostratigraphy used the biozonation schemes of Martini (1971) and Varol (1998) for calcareous nannofossils (N) and of Kaminski et al (1989), Kaminski (2005) and Bratu (1975) for foraminifera (F) listed in Ap pen dix 2. The dis tri bu tion of foraminifera within the stud ied sam ples can be ob served in the Ap pen dix 3.…”

“…The ag glu ti nated foraminifera biozonation used fol lows the Eocene to Oligocene scheme of Kaminski (2005) and Kaminski et al (1989) for the North At lan tic and West ern Tethys, and the Maastrichtian to early Oligocene scheme of Bratu (1975) for the East ern Carpathians. The foraminiferal biozones were es tablished by acmes or lo cal strati graphic ranges (Fig.…”

“…in sam ple 20 suggests an in crease in the or ganic mat ter flux (Kaminski, 2005). The Spiroplectammina spectabilis taxa is known to be an oppor tu nis tic "di sas ter spe cies" re lated to the trophic con tin uum (Kaminski and Gradstein, 2005); in the At lan tic and west ern Tethyan re gions (Kaminski et al, 1989;Kaminski, 2005) and an acme of Spiroplectammina spectabilis was re lated to eutrophic con di tions (Kaminski and Gradstein, 2005).…”