Depositional Successions On Glaciated Continental Margins Microform The Cenozoic Of Antarctica And The Neoproterozoic Of Rodinia

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.

Understanding the sedimentary and geophysical archive of glaciated margins is a complex task that requires integration and analysis of disparate sedimentological and geophysical data. Their analysis is vital for understanding the dynamics of past ice sheets and how they interact with their neighbouring marine basins, on timescales that cannot be captured by observations of the cryosphere today. As resources, sediments deposited on the inner margins of glaciated shelves also exhibit resource potential where more sand-dominated systems occur, acting as reservoirs for both hydrocarbons and water. This book surveys the full gamut of glaciated margins, from deep time (Neoproterozoic, Ordovician and Carboniferous–Permian) to modern high-latitude margins in Canada and Antarctica. This collection of papers is the first attempt to deliberately do this, allowing not only the similarities and differences between modern and ancient glaciated margins to be explored, but also the wide spectrum of their mechanisms of investigation to be probed. Together, these papers offer a high-resolution, spatially and temporally diverse blueprint of the depositional processes, ice sheet dynamics, and basin architectures of the world’s former glaciated margins; a vital resource in advancing understanding of our present and future marine-terminating ice sheet margins.

This book documents and interprets the onshore Cenozoic temperate carbonate depositional system along the southern margin of Australia. These strata, deposited in four separate basins, together with the extensive modern marine system offshore, comprise the largest such cool-water carbonate system on the globe. The approach is classic and comparative but the information is a synthesis of recent research and new information. A brief section of introduction outlines the setting, modern comparative sedimentology offshore, and structure of the Cenozoic onshore. The core of the book is a detailed analysis and illustration of the four Eocene to Pleistocene successions. Deposits range from temperate carbonates, to biosiliceous spiculites, to marginal marine siliciclastics. Each unit is interpreted, as much as possible, based on our understanding of the modern offshore depositional system. A subsequent part concentrates on diagenesis both before and after the late Miocene uplift. It turns out that alteration in the two packages is entirely different. The preceding attributes of each succession are then interpreted on the basis of controlling factors such as tectonics, oceanography, climate, and glaciation of nearby Antarctica. This research has revealed new implications for the interpretation of specific attributes of cool-water carbonate sedimentology that could only be discovered from the rock record. Insights concerning cyclicity, reef mounds, biosiliceous deposition, and trophic resources are detailed in the next section. The concluding part focuses on global comparisons, especially the Mediterranean and New Zealand.

This book examines the process and patterns of glacier-influenced sedimentation on high-latitude continental margins and the geophysical and geological signatures of the resulting sediments and landforms. It contains a range of papers concerning modern and glacially-influenced sedimentation in high-latitude areas from both hemispheres, many of which discuss the relationship between glacier dynamics and the sediments and landforms preserved in the glacimarine environment.

This book, based on the proceedings of third symposium held on 17th August 1977 during the Xth INQUA Congress at Birmingham, UK, focuses on the influence the Antarctic glaciation had on world palaeoenvironments.

Antarctica preserves a rock record that spans three and a half billion years of history and has a remarkable story to tell about the evolution of our Earth, from the hottest crustal rocks yet found in an orogenic system, to the assembly and breakup of Gondwana in the Phanerozoic. This volume highlights our improved understanding of the tectonic events that have shaped Antarctica and how these potentially relate to supercontinent assembly and fragmentation. The internal constitution of the East Antarctic Shield is assessed using information available from the basement geology and from detritus preserved as Mesozoic sediments in the Trans Antarctic Mountains. Accretionary orogenesis along the proto-Pacific margin of Antarctica is examined and the volumes of intracrustal melting compared with juvenile magma additions in these complex orogenic systems assessed. This special volume demonstrates the diversity of approaches required to elucidate and understand crustal evolution and evaluate the supercontinent concept.

In recent years, interest in Neoproterozoic glaciations has grown as their pivotal role in Earth system evolution has become increasingly clear. One of the main goals of the IGCP Project number 512 was to produce a synthesis of newly available information on Neoproterozoic successions worldwide. This Memoir consists of a series of overview chapters followed by site-specific chapters. The overviews cover key topics including the history of research on Neoproterozoic glaciations, identification of glacial deposits, chemostratigraphic techniques and datasets, palaeomagnetism, biostratigraphy, geochronology and climate modelling. The site specific chapters include reviews of the history of research on these rocks and up-to-date syntheses of the structural framework, tectonic setting, palaeomagnetic & geochronological constraints, physical, biological, and chemical stratigraphy, and descriptions of the glaciogenic and associated strata, including economic deposits.

We live in the Quaternary Ice Age, the last million years when large ice sheets covered much of North America and Eurasia, with successive glaciations lasting about 90,000 years interspersed with interglaciations lasting about 10,000 years, such as our preset Holocene interglaciation. Quaternary glaciations were discovered and mapped by glacial geologists from evidence for glacial erosion and deposition on a large scale. Glaciology began as a descriptive branch of geology and has become a quantitative branch of physics. Glaciology and glacial geology are two sides of the same coin. Glaciologists study ice dynamics to model present and past ice sheets. Glacial geologists study the evidence produced by ice dynamics, evidence that controls the models. This book is written for glacial geologists that have a modest exposure to mathematics so they can understand the fundamental link between glaciology and glacial geology. This link is the height of an ice sheet above its bed. Ice height depends primarily on the strength of ice-bed coupling. The stronger the coupling, the higher the ice, and therefore the larger the ice sheet. Glacial geology allows an assessment of ice-bed coupling. Coupling weakens under the interior of an ice sheet when a frozen bed thaws and thereby allows ice to slide over the bed to produce glacial geology by erosion and deposition processes. Coupling weakens much more near ice-sheet margins where ice moves as fast currents called ice streams, under which ice-bed coupling vanishes where basal water drowns bedrock bumps or soaks basal sediments. The book consists of seven chapters. Chapter One shows how glacial geology can be used to quantify the strength of ice-bed coupling. Chapter Two quantifies how coupling is weakened when a frozen bed thaws for slow sheet flow in the interior of an ice sheet, thereby lowering the ice surface. Chapter Three quantifies how the surface is lowered much more toward the margin of an ice sheet where basal water partly downs the bed along linear topography (river valleys, coastal straits, etc.), allowing for slow sheet flow to become fast stream flow. Chapter Four quantifies the ability of large partly confined floating ice shelves to reduce the discharge from fast ice streams entering the sea. Chapter Five discusses glacial geology produced by Northern Hemisphere ice sheets during a cycle of Quaternary glaciation, with a white hole needed to initiate an ice sheet, marine ice transgression needed to grow it, and marine ice instability needed to terminate it; these are all linked to glacial geology. Chapter Six shows how the Arctic ice sheet can be reconstructed during a cycle of Quaternary glaciation using glacial geology. Chapter Seven shows how glacial geology can be mapped under the Antarctic ice sheet as it exists today, with an emphasis on ongoing gravitational collapse of the Western Antarctic Ice Sheet, grounded mostly below sea level in the Western Hemisphere.