Triassic to Early Jurassic climatic trends recorded in the Jameson Land Basin,East Greenland: clay mineralogy,petrography and heavy mineralogy          下载免费PDF全文

Audrey Decou  Steven D. Andrews  David H. M. Alderton  Andrew Morton 《Basin Research》2017,29(5):658-673

During the Early Triassic the Jameson Land Basin (Central East Greenland) was located around 30° N, in the Northern arid belt, but by the Early Jurassic was positioned at a latitude of approximately 50° N. This study examines the record of this transition through a largely continental succession using clay mineralogy, sedimentology, petrography and heavy mineralogy. The Jameson Land Basin is aligned north–south and is 280 km long and 80 km wide. Following an Early Triassic marine phase the basin was filled by predominantly continental sediments. The Early‐to‐Late Triassic succession comprises coarse alluvial clastics (Pingo Dal Formation) overlain by a succession of fine‐grained evaporite‐rich playa/lacustrine sediments (Gipsdalen Formation), indicative of arid climatic conditions. The overlying buff, dolomitic and then red lacustrine mudstones with subordinate sandstones (Fleming Fjord Formation) record reduced aridity. The uppermost Triassic grades into dark organic‐rich, and in places coaly, mudstones and buff coarse‐grained sandstones of lacustrine origin that belong to the Kap Stewart Group, which spans the Triassic–Jurassic boundary, and appear to record more humid climatic conditions. Clay mineralogy analyses highlight significant variations in the kaolinite/illite ratio, from both mudstone and sandstone samples, through the Triassic and into the earliest Jurassic. Complementary heavy mineral analyses demonstrate that the variations recognised in clay mineralogy and sandstone maturity through the Triassic–Early Jurassic succession are not a product of major provenance change or the effect of significant diagenetic alteration. The observed variations are consistent with sedimentological evidence for a long‐term trend towards more humid conditions through the Late Triassic to Early Jurassic, and the suggestion of a significant pluvial episode in the mid‐Carnian.  相似文献   

UV transitions of astrophysical interest in Ge II, As II and Se II     

E. Biémont  D. C. Morton  & P. Quinet 《Monthly notices of the Royal Astronomical Society》1998,297(3):713-731

An extensive set of oscillator strengths and transition probabilities has been obtained for the UV transitions originating from the ground 4s²4p ⁿ ( n =1–3) states of Ge II , As II and Se II . These new data, calculated within the framework of a pseudo-relativistic Hartree–Fock (HFR) approach, fill in the gap existing in the atomic data needed for elemental abundance analysis of the interstellar medium. The f values are compared with the rather scarce results previously published in the literature. The astrophysical implications of the new transition rates regarding the interstellar medium are discussed.  相似文献   

The provenance and diagenesis of Palaeogene sandstones of southeast England as indicated by heavy mineral analysis     

Andrew C. Morton 《Proceedings of the Geologists' Association. Geologists' Association》1982,93(3):263-274

  相似文献   

The mineralogy,sulfur-isotope composition and origin of some copper deposits in the Belt Supergroup,Southwest Alberta,Canada     

R. D. Morton  R. J. Goble  P. Fritz 《Mineralium Deposita》1974,9(3):223-241

Stratabound Cu mineralization in the Precambrian, red-bed sequences of the Belt-Purcell Supergroup of SW Alberta, Canada is described. Local enrichment of mineralization has been effected by younger Precambrian dioritic intrusions and by hydrothermal activity adjacent to normal faults. Data from mineralogic and sulfur isotope studies suggest that the base metal deposits were originally syngenetic or diagenetic and that they have suffered redistribution and concentration during contact metamorphism and perhaps low grade regional metamorphism. The primary metal-bearing fluids may have been derived by exhalative activity associated with a Precambrian aulacogenic structure which possibly underlies the region.  相似文献   

LETTERS TO THE PRESIDENT OF THE ASSOCIATION     

Grant W. Miller  Fred E. Dohrs  Keith D. Harries  Glenn T. Trewartha  Wolf Roder  James S. Ward  Morton D. Winsberg  Bryce Decker  Thomas J. Wilbanks 《The Professional geographer》1973,25(4):383-390

  相似文献   

Identifying provenance-specific features of detrital heavy mineral assemblages in sandstones   总被引：20，自引：0，他引：20  

Andrew C. Morton  Claire Hallsworth 《Sedimentary Geology》1994,90(3-4):241-256

The composition of heavy mineral assemblages in sandstones may be heavily influenced by processes operating during transport, deposition and diagenesis. As a consequence, conventional heavy mineral data may not be a reliable guide to the nature of sediment source material. Certain features of heavy mineral suites, however, are inherited directly from the source area without significant modification, such as the varietal characteristics of individual mineral species. This paper describes an alternative approach to varietal studies that concentrates on relative abundances of minerals that are stable during diagenesis and have similar hydraulic behaviour. Ratios of apatite to tourmaline, TiO₂ minerals to zircon, monazite to zircon, and chrome spinel to zircon provide a good reflection of the source rock characteristics, because they are comparatively immune to alteration during the sedimentary cycle. These ratios are described as index values (ATi, RZi, MZi and CZi, respectively). This approach avoids some of the practical problems associated with varietal studies, such as the need to make subjective decisions about mineral properties or to use advanced analytical techniques that may not be accessible to the analyst. It also makes use of more components of the heavy mineral suite and thus provides a more balanced view of provenance characteristics. The use of these ratios is illustrated with examples from Upper Jurassic sandstones in the Outer Moray Firth area of the UK continental shelf and Triassic sandstones from onshore and offshore UK. Heavy mineral indices, notably ATi and MZi, show marked variations in Upper Jurassic Piper sandstones of the Outer Moray Firth. Main Piper sandstones have lower ATi and MZi values compared with Supra Piper sandstones, indicating significant stratigraphic evolution of provenance. The UK Triassic shows major regional variations in a number of index values, including ATi, MZi and CZi, demonstrating that sediment was supplied from several distinct source regions. This indicates a need for some modification of existing palaeogeographic models for the UK Triassic.  相似文献   

Is size important?     

Morton B 《Marine pollution bulletin》2012,64(1):1-2

  相似文献   

What a pile of old rubbish!     

Brian Morton 《Marine pollution bulletin》2009,58(8):1097-1098

  相似文献   

Marine conservation: What and why?     

Brian Morton 《Marine pollution bulletin》2010,60(3):317-318

  相似文献   

Evidence for glaciation in the Northern Hemisphere back to 44 Ma from ice-rafted debris in the Greenland Sea     

Aradhna K. Tripati  Robert A. Eagle  Andrew Morton  Julian A. Dowdeswell  Katie L. Atkinson  Yannick Bahé  Caroline F. Dawber  Emma Khadun  Ruth M.H. Shaw  Oliver Shorttle  Lavaniya Thanabalasundaram 《Earth and Planetary Science Letters》2008,265(1-2):112-122

The widely accepted age estimate for the onset of glaciation in the Northern Hemisphere ranges between 2 and 15 million years ago (Ma). However, recent studies indicate the date for glacial onset may be significantly older. We report the presence of ice-rafted debris (IRD) in ～ 44 to 30 Ma sediments from the Greenland Sea, evidence for glaciation in the North Atlantic during the Middle Eocene to Early Oligocene. Detailed sedimentological evidence indicates that glaciers extended to sea level in the region, allowing icebergs to be produced. IRD may have been sourced from tidewater glaciers, small ice caps, and/or a continental ice sheet.  相似文献