Latest Cretaceous to Cenozoic Climate and Oceanographic Developments in the Weddell Sea, Antarctica: an Ocean-Drilling Perspective

Abstract

This is a summary of principal findings made by ODP Leg 113 investigators concerning the latest Cretaceous-Cenozoic climatic, cryospheric, and oceanographic history, and biogeographic developments of the Weddell Sea region, Ant arctica. During Leg 113, 22 holes were drilled at 9 sites that sampled 4 contrasting environments: open-ocean pelagic sedimentation on Maud Rise (Sites 689 and 690

Multiproxy reconstruction of the palaeoclimate and palaeoenvironment of the Middle Miocene Somosaguas site (Madrid, Spain) using herbivore dental enamel

“…Therefore, it seems that the isotopic record of the mammalian fauna from the Somosaguas sites might reflect a deep change from a warm phase to a temperate phase within the Milankovitch cyclicity typical of the Earth climatic variability. The intensity of this oscillation could be related to the enhancement of the Middle Miocene global cooling trend 14 Ma ago (Flower, 1999;Shevenell et al, 2004 These findings support the general pattern of global cooling and increased aridity observed by different authors in marine and continental sections from this period (Samthein et al, 1982;Kennett and Barker, 1990;van der Meulen and Daams, 1992;Zachos et al, 2001 ;Hemandez Femandez et al, 2003;Cuevas-Gonzalez, 2005;Fesharaki, 2005). As previously said, Lower and Middle Units in the Madrid Basin show very low sedimentation rates, so that a time span of � 105-125 ka can be estimated from T1 to T3-3.…”

“…The Miocene Climatic Optimum (�20 to 14-13.5 Ma), a warm and humid subtropical period, was followed by a quick cooling episode and an increase in the aridity patterns linked to the reestablishment of the Antarctica ice cap during the Middle Miocene. This event has been recorded in marine and continental sections throughout the world highlighting its global magnitude (Kennett and Barker, 1990;Frakes et al, 1994;B6hme, 2003;Shevenell et al, 2004;Lewis et al, 2008;Costeur and Legendre, 2008). Even though uncertainty concerning the ultimate cause that brought about these profound changes in the global climate still remains, several hypotheses have been invoked as trigger mechan isms.…”

Chapter 5 Cenozoic Climate History from Seismic Reflection and Drilling Studies on the Antarctic Continental Margin

“…In the central Weddell Sea Basin, the pre-Oligocene section of inferred turbidites is more than 1 km thick, and thins by basal onlap towards the margins to less than 0.5 km (Rogenhagen et al, 2004). High seasonal variations in sea-surface temperatures and a well-developed seasonal thermocline characterized the early Paleogene Weddell Sea (Kennett and Barker, 1990). On Maud Rise, siliceous biogenic facies began to replace carbonate facies during the latest Eocene-earliest Oligocene (Kennett and Barker, 1990).…”

“…High seasonal variations in sea-surface temperatures and a well-developed seasonal thermocline characterized the early Paleogene Weddell Sea (Kennett and Barker, 1990). On Maud Rise, siliceous biogenic facies began to replace carbonate facies during the latest Eocene-earliest Oligocene (Kennett and Barker, 1990). A possible early Cenozoic seaway between East and West Antarctica could have been up to 700 m deep, and may have persisted into the Oligocene if no WAIS was present (Lawver and Gahagan, 2003).…”

“…Reflector W4). The unconformity may represent non-deposition and/or mild erosion (Kennett and Barker, 1990).…”