Palaeobiogeography of Early Cretaceous (Berriasian–Barremian) calcareous nannoplankton
In order to assess Early Cretaceous nannoplankton biogeography, we studied a series of sites which provide a north-south transect across the Atlantic Ocean, supplemented by sections from the North Sea Basin, Barents Sea, Falkland Plateau, Weddell Sea (Antarctica), Argo Abyssal Plain (NW of Australia...
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Published in | Marine micropaleontology Vol. 39; no. 1-4; pp. 265 - 291 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
01.06.2000
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Subjects | |
Online Access | Get full text |
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Summary: | In order to assess Early Cretaceous nannoplankton biogeography, we studied a series of sites which provide a north-south transect across the Atlantic Ocean, supplemented by sections from the North Sea Basin, Barents Sea, Falkland Plateau, Weddell Sea (Antarctica), Argo Abyssal Plain (NW of Australia) and Neuqu e n Basin (Argentina). Quantitative assemblage data were gathered from each site for seven time-slices within the Berriasian to Barremian interval, each horizon being determined by a nannofossil datum. Trends in species relative abundance and measures of diversity, evenness and richness provide revealing biogeographic information. A broad, low- to mid-palaeolatitude zone (50 degree N-50 degree S) is flanked in both Northern and Southern Hemispheres by distinct high-palaeolatitude zones. Major changes in assemblage abundance and composition occur across a sharp biogeographic 'front' at around 50 degree N and S palaeolatitude. High-palaeolatitude assemblages are lower in species richness and diversity and characterised by the presence of abundant, typically bipolar, taxa (e.g. Crucibiscutum salebrosum). A less distinct biogeographic boundary at similar to 40 degree N is distinguished by the presence/absence of rarer, but biogeographically significant, taxa, many of which have previously been assigned to Boreal or Tethyan provinces. Continental shelf sites are characterised by lower-diversity assemblages with common to dominant diagnostic taxa, which vary with palaeolatitude: Nannoconus and Micrantholithus at low palaeolatitudes, and Biscutum constans and Zeugrhabdotus spp. at higher palaeolatitudes. The latter two taxa are considered to be indicative of elevated surface-water fertility and the former two may have been similarly adapted. The genus Watznoueria is ubiquitously dominant, giving the populations an unevenness, which appears to be a common feature throughout coccolithophore history. |
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Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
ISSN: | 0377-8398 |
DOI: | 10.1016/S0377-8398(00)00024-4 |