Cyclic sedimentation in the Southern Alpine Rhaetic: the importance of climate and eustasy in controlling platform-basin interactions     

MARK T. BURCHELL  MARCO STEFANI†  DANIELE MASETTI† 《Sedimentology》1990,37(5):795-815

Uppermost Triassic (Rhaetic) facies, as developed in the Southern Alpine region of Northern Italy, were deposited in a rapidly subsiding, fault-dissected trough (the Lombardy Basin) bounded by carbonate platforms. The main part of the Rhaetic succession consists of 10-m-scale asymmetric cycles, each divided into three parts: a lower shale portion; a central rhythmic portion consisting of repeated marl-limestone couplets, the limestone parts of which thicken upward; and an upper, wholly carbonate unit. A study of the diagenetic history of the series demonstrates that both the major asymmetric cyclicity and the limestone-marl couplets of the central rhythmic member (together constituting a ‘compound’ cyclic form) are fundamentally depositional in nature. It is suggested that this compound cyclicity resulted from the superposition of a low-frequency (approximately 100 000-year periodicity) asymmetric carbonate mud signal with a higher-frequency terrigenous mud signal. Field, petrographic, and geochemical investigations suggest that the basinal carbonate is predominantly allochthonous in origin, having been derived as relatively pure aragonitic mud from adjacent carbonate platforms. It is postulated that the asymmetric carbonate signal was linked to the ecological effects of eustatic fluctuation on platform carbonate systems. Repeated subaerial exposure of subtidal muds in shallow areas indicates that such sea-level variations occurred. A model is presented in which the basinward export of carbonate was negligible in the deepening phase, increased to a maximum during shallowing and was finally halted by the emergence of large platform flats. In contrast, the higher frequency terrigenous mud signal of the basin is thought to have been climatically modulated; fluctuations of a shorter period than those predicted by the Milankovitch theory affected hinterland precipitation and runoff. Particularly rapid subsidence and high depositional rates may have allowed the preservation of this signal.  相似文献   

Atmospheric Mg²⁺ wet deposition within the continental United States and implications for soil inorganic carbon sequestration     

MEGAN A. GODDARD  ELENA A. MIKHAILOVA  CHRISTOPHER J. POST  MARK A. SCHLAUTMAN 《Tellus. Series B, Chemical and physical meteorology》2007,59(1):50-56

  相似文献   

Late Devensian and Holocene depositional environments associated with the coversand around Caistor, north Lincolnshire, UK     

MARK D. BATEMAN  JULIAN B. MURTON  WILLIAM CROWE 《Boreas: An International Journal of Quaternary Research》2000,29(1):1-15

Sand deposits described at three sites near Caistor, north Lincolnshire (UK), provide a record of Late Devensian (Late Weichselian) to Holocene palaeoenvironments at the western margin of the European sand belt. Thermoluminescence (TL) and radiocarbon analyses provide for the first time a chronological framework for the demise of proglacial Lake Humber and the onset of coversand deposition. The reconstructed palaeoenvironmental history suggests that proglacial Lake Humber had receded from its initial high-level stand before c. 18 ka, exposing the lake floor to periglacial conditions marked by the development of thermal contraction cracks. In the period between c. 18 and 14 ka, sand-depositional processes changed from dominantly fluvial to aeolian. The fluvial activity was possibly a consequence of ameliorating winter climates between c. 17 and 16 ka. The aeolian coversand deposition in this period has not been previously recognized in Britain and correlates with the Older Coversand II and Younger Coversand I deposits elsewhere in the European sand belt. Peat accumulation followed during the Windermere (Bølling/Allerød) Interstadial and early part of the Loch Lomond Stadial (Younger Dryas) before regionally extensive coversand deposition took place in the later part of the Loch Lomond Stadial. This coversand correlates with the widespread Younger Coversand II deposits found both within the UK and across the European sand belt. The Holocene has been characterized by widespread stability with the development of soils on the coversand punctuated with periods of localized reworking through to the present day.  相似文献   

Three-dimensional transport and concentration of SF₆     

A. SCOTT DENNING  MARK. HOLZER  KEVIN R. GURNEY  MARTIN HEIMANN  RACHEL M. LAW  PETER J. RAYNER  INEZ Y. FUNG  SONG-MIAO FAN  SHOICHI TAGUCHI  PIERRE FRIEDLINGSTEIN  YVES BALKANSKI  JOHN TAYLOR  MANFRED MAISS  INGEBORG LEVIN 《Tellus. Series B, Chemical and physical meteorology》1999,51(2):266-297

  相似文献   

Aspects of the large-scale tropical atmospheric circulation     

BRIAN HOSKINS  RICHARD NEALE  MARK RODWELL  GUI-YING YANG 《地球，A辑:动力气象学与海洋学》1999,51(1):33-44

  相似文献   

Re‐evaluation of the Last Glacial Maximum typesite at Dimlington,UK     

MARK D. BATEMAN  PAUL C. BUCKLAND  MARTIN A. WHYTE  ROBERT A. ASHURST  CLAIRE BOULTER  EVA PANAGIOTAKOPULU 《Boreas: An International Journal of Quaternary Research》2011,40(4):573-584

Bateman, M. D., Buckland, P. C., Whyte, M. A., Ashurst, R. A., Boulter, C. & Panagiotakopulu, E. 2011: Re‐evaluation of the Last Glacial Maximum typesite at Dimlington, UK. Boreas, 10.1111/j.1502‐3885.2011.00204.x. ISSN 0300‐9483. Recent erosion has allowed re‐examination of the stratigraphy and sampling for both optically stimulated luminescence dating and palaeoecological analysis of the key sections in the Last Glacial Maximum deposits at Dimlington in East Yorkshire, England. Both stratigraphy and fossil insect evidence support a subaerial origin for laminated and cross‐bedded sediments between two diamictons previously interpreted as synchronous. The fossil biota indicates conditions similar to those of a pond on sandur in the high Arctic, with little or no vegetation cover. The existence of distinct oscillations of the ice front is indicated. The first, within the period 21.7–16.2 ka, appears coincident with climate warming, as deduced from Greenland ice‐core evidence, and is interpreted as an ice stream associated with changing flow patterns within the British–Irish Ice Sheet (BIIS). The second, dating between 16.2 and 15.5 ka, appears to coincide with a climatic cooling, although current models show that the BIIS had by this period already retreated back to ice centres. This new evidence supports the view that the eastern sector of the BIIS did not reach its maximal extent synchronously with other parts of the BIIS.  相似文献   

On the background photochemistry of tropospheric ozone     

PAUL J. CRUTZEN  MARK G. LAWRENCE  ULRICH PÖSCHL 《地球，A辑:动力气象学与海洋学》1999,51(1):123-146

  相似文献   

Sr, Nd, Pb and O Isotopes of Minettes from Schirmacher Oasis, East Antarctica: a Case of Mantle Metasomatism involving Subducted Continental Material   总被引：2，自引：4，他引：2  

HOCH  MARION; REHKAMPER  MARK; TOBSCHALL  HEINZ J. 《Journal of Petrology》2001,42(7):1387-1400

Numerous minette dykes intersect the Precambrian crystallinebasement of Schirmacher Oasis, East Antarctica. This study presentsnew Sr, Nd, Pb and O isotope data for 11 minette samples fromfour different dykes. The samples are characterized by relativelyhigh ⁸⁷Sr/⁸⁶Sr (0·7077–0·7134), ²⁰⁷Pb/²⁰⁴Pb(15·45–15·55) and ²⁰⁸Pb/²⁰⁴Pb (37·8–39·8),combined with low ¹⁴³Nd/¹⁴⁴Nd (  相似文献   

The planform of epeirogeny: vertical motions of Australia during the Cretaceous   总被引：1，自引：0，他引：1  

MARK Russell  MICHAEL Gurnis 《Basin Research》1994,6(2-3):63-76

  相似文献   

Climatic control on Quaternary fluvial sedimentology of a Fenland Basin river, England   总被引：1，自引：0，他引：1  

REBECCA M. BRIANT  MARK D. BATEMAN†  G. RUSSELL COOPE‡  PHILIP L. GIBBARD 《Sedimentology》2005,52(6):1397-1423

  相似文献