Phanerozoic earth history of Australia

Phanerozoic earth history of Australia

336 beautifully brown-and-white banded Castile Anhydrite (Permian) in the Delaware Basin of west Texas. Cyclic lacustrine deposits of Late Triassic ag...

206KB Sizes 1 Downloads 42 Views

336 beautifully brown-and-white banded Castile Anhydrite (Permian) in the Delaware Basin of west Texas. Cyclic lacustrine deposits of Late Triassic age in the Newark Basin of New Jersey and Pennsylvania likewise are linked to Milankovitch cycles by P. E. Olsen. The rhythmic facies alternations that characterize so much of the Cretaceous in western Europe have received a great deal of detailed attention from Milankovitch-oriented researchers. Much of the recent work on Cretaceous bedding rhythms is summarized in three intriguing papers (by Fischer and Schwarzacher; De Boer and Wonders; Arthur, Dean, Bottjer and Scholle). Most of the Milankovitch-related research by geologists has emphasized Cenozoic, particularly Quarternary, paleoclimatic cycles. The remaining 18 papers in Part H of the report focus on the Late Cenozoic, as do virtually all of the 23 papers in Part III ("Modelling Long-Term Climatic Variations in Response to Astronomical Forcing"). Cyclic variations in deep-sea sediment chemistry (calcium carbonate, organic carbon, stable isotopes, etc.) and nonmarine pollen assemblages provide the fundamental data base from which paleoclimatic trends have been derived. The last part of the report ("Climatic Variations at Astronomical Frequencies") contains conclusions and recommendations prepared by the conference participants. These recommendations are numerous, and they relate specifically to the research papers offered in the report. There is some uncertainty in my mind as to the value of such recommendations to the casual but interested reader. Perhaps they are meant for the ears of program directors of the major research funding agencies, or perhaps they simply are expressions of the new research directions the participating scientists would like to pursue in the next few years. Milankovitch and Climate is a ponderous collection of works that serves to provide a state-of-art summary of the fascinating field of paleoclimatic megacycles. It is not tightly edited, and typos abound. The book is printed directly from typescript copy, and there are hardly any photographs, so the enormous pricetag is a bit of a mystery. Nevertheless, this a very hot area of research that currently is receiving incredibly large expenditures of time and money, so I'm certain this report will be welcomed by a great many people. A. A. EKDALE (Salt Lake City, Utah)

Phanerozoic Earth History of Australia (Oxford Geological Sciences Series, 2) Edited by J. J. Veevers, Clarendon Press, Oxford, 1984, 364 pp., £55.00. Hardback. The striking LANDSAT images used as the frontispiece set the tone for this volume with its emphasis on the continuum of plate tectonic and related surface processes throughout the Phanerozoic. There is a strong uniformitarian theme to the work which "begins and ends with the modern surface of

337 Australia, the only living expression we have of Australian tectonic regimes". For most of its history Australia was an integral part of Gondwanaland becoming, with India and Antarctica, Eastern Gondwanaland about 160 Ma ago and finally separating from Antarctica to form an independent continent about 95 Ma ago. "The appropriate frame for the study of the Phanerozoic history of the daughter continents is Gondwanaland itself." Much of the depositional history of the continent is linked to the development of rifted/ divergent margins on the one hand and magmatic arcs/convergent margins on the other. The present-day tectonic situation of Australia is reviewed and past global settings are derived from studies of continental and oceanic palaeomagnetism. The area of greatest uncertainty in the reconstructions is in the zone of convergence between Sundaland (Southeast Asia) and Australia. The boundary between the Australian lithosphere and the allochthonous Asian and Pacific terrains is not clearly defined and conflicting models have been proposed. To what extent are the Banda Arcs underthrust by Australian continental lithosphere? There is a substantial section on palaeoclimates and palaeoenvironments. During the last glacial maximum about 18,000 yr ago sea-level was 150-200 m lower than at present so that New Guinea, Tasmania and other islands were linked with the Australian mainland. The changing biogeography of Australia is linked with the dispersal of continental blocks and controls on migration have led to the distinctiveness of contemporary Australian flora and fauna. A predeliction towards biological analogy persists in this book and is nowhere more apparent than in the chapter on "Lithospheric Structure" which is subdivided into sections on "Gross anatomy" and "Physiology". A major feature is the Tasman Line which separates the Precambrian blocks of the west from the Phanerozoic fold belts and basins to the east. The Precambrian is underlain by thick lithosphere and a felsic granulite/eclogite lower crust in contrast to the thin lithosphere and mafic/ultramafic lower crust below the Phanerozoic terrain. The "physiology" (seismicity and fault motions) points to substantial horizontal compression within the Australian platform and anticlockwise rotation of the continent in response to sinistral shear motion in New Guinea. Volcanicity is concentrated along the northern active margin of the continent but Cenozoic volcanism in Eastern Australia appears to reflect intraplate stresses. The two longest chapters deal with "Morphotectonics of the Australian platform and margins" and "Australia's Phanerozoic history". The former is concerned with neotectonic structures where landforms reflect the processes that formed them. Emphasis is firstly on the complex Pliocene collision zone of the northern margin, Timor and the New Guinea Highlands. The greater part of the chapter is devoted to a detailed stratigraphical analysis of the Eastern Highlands of Australia in terms of morphotectonic cycles and epeirogenic movements. Finally, the divergent southern and western margins of Australia are examined taking the modern East Africa-Arabia rift system as an analogy.


The following chapter reviews the major regimes of the late Precambrian and Phanerozoic starting with the Adelaidean (rift valley, glacigene sediments, Ediacara Fauna), and the Uluru (Palaeozoic - plateau basalts, evaporites, carbonates, magmatic arc, marginal sea, granitoids). During the Innamincka (Upper Palaeozoic - Mesozoic) continent-wide glaciation occurred at ca. 240 Ma and Southeast Australia was situated over the South Pole: this phase was followed by magmatic arcs and volcanigenic sedimentation. The Potoroo Regime (late Mesozoic-Cenozoic) was marked by the separation of Australia from Antarctica and sediment accumulation in the Ceduna Depocentre, followed by a series of marine transgressions. The volume concludes with a brief synopsis and so-called "cinematograph"-a curious misuse of the term for the "time-lapse sequence of palaeogeographic reconstructions". However, this is a comprehensive and scholarly text, well written and clearly illustrated. The price will be a deterrent but unfortunately it is almost inevitable nowadays for a research-level book of this kind. P. E. BAKER(Nottingham,U.K.)

Coated Grains. Edited by T. M, Peryt, Springer, Heidelberg. 1983, 655 pp., DM 140,00]approx. US $55.60 (clothbound). This attractive book on "Coated Grains", which would be better entitled "Carbonate coated grains", contains 52 articles in 6 chapters: Problems of classification, textural, mineralogical and geochemical composition and formation of ooids, rhodoids, oncoids and vadoids. Their genesis in relation mainly to carbonate environmental conditions in time and space are discussed. In the approaches (Chapter I) the two introducing papers of Peryt and Richter present possible classifications of carbonate coated grains, whereby Peryt includes genetic terms whereas Richter pleads for a more descriptive subdivision. The following two papers (Brand and Veizer; Margaritz) characterize texture, mineralogy and trace element contents in carbonate coated grains from recent and ancient marine and terrestrial environments and discuss the use of the carbon and oxygen isotope composition for milieu interpretations. Hottinger interprets macroid growth from the Mediterranean and Red Sea by coating organisms like coralline algues in the euphotic, subtidal, neritic zone within narrow equilibra conditions. Accretionary lapillis, their mechanical formation in recent and ancient periods and their indicative value as time and paleo-environmental marks are discussed by Reimer. Chapter II presents 12 papers on "Ooid" genesis. The introducing paper of Richter typifies texture varieties of marine and non-marine primary and diagenetic ooids and points out the mineralogical and chemical change from initial to diagenetic composition, the role of organic material for ooid genesis,