Author : Nicole N. (Nicole Naomi) Januszczak
Release : 2004
Genre :
Kind : eBook
Book Rating : 453/5 ( reviews)
Book Synopsis Depositional Successions on Glaciated Continental Margins [microform] : the Cenozoic of Antarctica and the Neoproterozoic of Rodinia by : Nicole N. (Nicole Naomi) Januszczak
Download or read book Depositional Successions on Glaciated Continental Margins [microform] : the Cenozoic of Antarctica and the Neoproterozoic of Rodinia written by Nicole N. (Nicole Naomi) Januszczak. This book was released on 2004. Available in PDF, EPUB and Kindle. Book excerpt: Part II of this thesis focuses on the sedimentological and stratigraphic evidence for glaciation in the Neoproterozoic. Integrating this analysis with a recent understanding of the tectonic setting of Neoproterozoic sedimentary basins provides a basis for an alternative 'zipper-rift' hypothesis for Neoproterozoic glaciations. The 'zipper-rift' model emphasizes a strong linkage between the first-order reorganisation of the Earth's surface created by rifting of Rodinia, the climatic effects of uplifted rift flanks and the resulting sedimentary record deposited in newly formed rift basins. Neoproterozoic glaciation was regional in extent, strongly controlled by tectonics and diachronous in its timing as Rodinia progressively broke apart over some 150 million years. This thesis is presented in two parts. The first half deals with the Cenozoic glacial record of Antarctica and the second half focuses on the Neoproterozoic glacial record of Rodinia. The glacially-influenced Cenozoic continental margin of Antarctica shows a large-scale subsurface seismic stratigraphy consisting of flat-lying 'topsets' recording episodic aggradation of the continental shelf, that rest on seaward-dipping, wedge-shaped 'foresets' formed by the progradation of the continental slope. Strata from topsets record aggradation by till deposition alternating with glacial-marine sedimentation. Strata from foresets record debris flows and turbidity currents on an active slope close to a source of poorly-sorted glacial debris such as an ice sheet margin reaching the shelf break. The original intention at the commencement of the thesis was to use depositional models derived from Antarctica as 'modern' analogues for Neoproterozoic successions. Critical evaluation of Neoproterozoic successions shows that many are not glacial in origin. Many Neoproterozoic 'glacial' successions have been identified as glacial on the basis of the presence of diamictite facies. Diamictite facies are commonly present within thick turbidite successions and are the product of active rifting and the shedding of poorly sorted debris into rapidly subsiding marine rift basins. The sedimentary record from the continental shelf of Prydz Bay, East Antarctica was examined by Ocean Drilling Program Leg 188. This record constrains the onset of glaciation in Antarctica to the late Eocene (c. 39 Ma) and records an important interval in the history of Antarctica, capturing for the first time the transition from a warmer preglacial climate, through early-glacial, and culminating in continental-scale glaciation of Antarctica.
