%0 Journal Article
%@ 0884-5891
%A Baumgartner, P.O.
%A Bown, P.
%A Marcoux, J.
%A Mutterlose, J.
%A Kaminski, M.A.
%A Haig, D.
%A McMinn, A.
%D 1992
%F discovery:18318
%J Proceedings of the Ocean Drilling Program: Scientific Results
%P 739-758
%T Early Cretaceous biogeographic and oceanographic synthesis of Leg 123 (off Northwestern Australia)
%U https://discovery-pp.ucl.ac.uk/id/eprint/18318/
%V 123
%X Biogeographic observations made by Leg 123 shipboard paleontologists for Lower Cretaceous nannofossils, foraminifers,  radiolarians, belemnites, and inoceramids are combined in this chapter to evaluate the paleoceanographic history  of the northwestern Australian margin and adjacent basins. Each fossil group is characterized at specific intervals of  Cretaceous time and compared with data from Tethyan and Southern Hemisphere high-latitude localities. Special attention  is given to the biogeographic observations made for the Falkland Plateau (DSDP Legs 36 and 71) and the Weddell Sea  (ODP Leg 113). Both areas have yielded valuable Lower Cretaceous fossil records of the circumantarctic high latitudes.  In general, the Neocomian fossil record from DSDP and ODP sites off northwestern Australia has important southern  high-latitude affinities and weak Tethyan influence. The same is true for the pelagic lithofacies: radiolarian chert and/or  nannofossil limestone, dominant in the Tethyan Lower Cretaceous, are minor lithologies in the Exmouth-Argo sites.  These observations, together with the young age of the Argo crust and plate tectonic considerations, suggest that the Argo  Basin was not part of the Tethys Realm.  The biogeography of the Neocomian radiolarian and nannofossil assemblages suggests opening of a seaway during  the Berriasian that connected the circumantarctic area with the Argo Basin, which resulted in the influx of southern  high-latitude waters.  This conclusion constrains the initial fit and break-up history of Gondwana. Our results favor the loose fit of the  western Australian margin with southeast India by Ricou et al. (1990), which accounts for a deeper water connection with  the Weddell-Mozambique basins via drowned marginal plateaus as early as the Berriasian. In fits of the du Toit-type  (1937), India would remain attached to Antarctica, at least until the late Valanginian, making such a connection  impossible.  After the Barremian, increasing Tethyan influence is evident in all fossil groups, although southern high-latitude taxa  are still present. Biogeographic domains, such as the southern extension of Nannoconus and Ticinella suggest paleolatitudes  of about 50°S for the Exmouth-Argo area. Alternatively, if paleolatitudes of about 35° are accepted, these  biogeographic limits were displaced northward at least 15° along Australia in comparison to the southern Atlantic. In this  case, the proto-circumantarctic current was deflected northward into an eastern boundary current off Australia and carried  circumantarctic cold water into the middle latitudes.  Late Aptian/early Albian time is characterized by mixing of Tethyan and southern faunal elements and a significant  gradient in Albian surface-water temperatures over 10° latitude along the Australian margin, as indicated by planktonic  foraminifers. Both phenomena may be indicative of convergence of temperate and antarctic waters near the Australian  margin. High fertility conditions, reflected by radiolarian cherts, are suggestive of coastal upwelling during that time.
%Z Issue entitled: Argo Abyssal Plain/ Exmouth Plateau covering Leg 123 of the cruises of the Drilling Vessel JOIDES Resolution, Singapore, Republic of Singapore, to Singapore, Republic of Singapore, Sites 765-766, 28 August 1988 - 1 November 1988