Late Quaternary glacial history of the central west coast of Jameson Land, East Greenland     

ÓLAFUR INGÓLFSSON  ASTRID LYSÅ  SVEND FUNDER  PER MÖLLER  SVANTE BJÖRCK 《Boreas: An International Journal of Quaternary Research》1994,23(4):447-458

The Late Quaternary ( c . 130,000–10,000 BP) glacial history of the central west coast of Jameson Land, East Greenland, is reconstructed through glacial stratigraphical studies. Seven major sedimentary units are described and defined. They represent two interglacial events (where one is the Holocene). one interstadial event and two glacial events. The older interglacial event comprises marine and fluvial sediments, and is correlated to the Langelandselv interglacial, corresponding to oxygen isotope sub-stage 5e. It is followed by an Early Weichselian major glaciation during the Aucellaelv stade, and subsequently by an Early Weichselian interstadial marine and deltaic event (the Hugin Sø interstade). Sediments relating to the Middle Weichselian have not been recognized in the area. The Hugin Sø interstade deposits have been overrun by a Late Weichselian ice advance, during the Flakkerhuk stade, when the glacier, which probably was a thin, low gradient fjord glacier in Scoresby Sund, draped older sediments and landforms with a thin till. Subsequent to the final deglaciation, some time before 10,000BP, the sea reached the marine limit around 70 m a.s.l., and early Holocene marine, fluvial and littoral sediments were deposited in the coastal areas.  相似文献   

Factors influencing magnetic susceptibility in the southern Pyrenees     

Óscar Pueyo Anchuela  Andrés J. Pocoví  Andrés Gil Imaz  Antonio M. Casas-Sainz 《Studia Geophysica et Geodaetica》2013,57(4):692-709

We analyse paramagnetic, ferrimagnetic and frequency-dependent susceptibility in the southern Pyrenees and northern Ebro basin. The analyzed rocks show a wide range of values for the three parameters within the different lithological groups. Sandstones, shales and marls exhibit middle to high values of paramagnetic susceptibility while mudstones usually show low values. However, a general correlation can be established for the different rock types with a wide variability for each group (for example, Eocene marls show average values of paramagnetic susceptibility of 82% but within a range between 12 and 99%, or Flysch materials, with mean values of 47–52% within a range between 15 and 90%). These changes in the paramagnetic contribution to the susceptibility are due to the change in the ferrimagnetic susceptibility. This wide variability is independent of the sedimentological characteristics and can be related to the higher ferrimagnetic contribution to the susceptibility with similar ferrimagnetic mineral phase assemblages. The ferrimagnetic and superparamagnetic contributions, independent of site location with respect to individual macrostructures (thrusts and nappes), show a sharp increase at the occurrence of the macroscopic regional Pyrenean cleavage, probably relating both aspects with changes in pressure-temperature (P-T) conditions.  相似文献   

Geodetic data shed light on ongoing caldera subsidence at Askja, Iceland     

Elske de Zeeuw-van Dalfsen  Hazel Rymer  Erik Sturkell  Rikke Pedersen  Andy Hooper  Freysteinn Sigmundsson  Benedikt Ófeigsson 《Bulletin of Volcanology》2013,75(5):1-13

Subsidence within the main caldera of Askja volcano in the North of Iceland has been in progress since 1983. Here, we present new ground- and satellite-based deformation data, which we interpret together with new and existing micro-gravity data, to help understand which processes may be responsible for the unrest. From 2003 to 2007, we observe a net micro-gravity decrease combined with subsidence and from 2007 to 2009 we observe a net micro-gravity increase while the subsidence continues. We infer subsidence is caused by a combination of a cooling and contracting magma chamber at a divergent plate boundary. Mass movements at active volcanoes can be caused by several processes, including water table/lake level movements, hydrothermal activity and magma movements. We suggest that, here, magma movement and/or a steam cap in the geothermal system of Askja at depth are responsible for the observed micro-gravity variations. In this respect, we rule out the possibility of a shallow intrusion as an explanation for the observed micro-gravity increase but suggest magma may have flowed into the residing shallow magma chamber at Askja despite continued subsidence. In particular, variable compressibility of magma residing in the magma chamber as well as compressibility of the surrounding rock may be the reason why this additional magma did not create any detectable surface deformation.  相似文献   

Age,growth, and sexual maturity of two New Zealand endemic skates,Dipturus nasutus and D. innominatus     

Malcolm P. Francis  Caoimhghin Ó Maolagáin  Darren Stevens 《新西兰海洋与淡水研究杂志》2013,47(4):831-842

Abstract

Rough and smooth skates (Dipturus nasutus (Banks 1841) and/), innominatus (Garrick &; Paul 1974)) were aged by counting growth bands on X‐rays of thick sections of vertebral centra. Band counts were imprecise, but there was no between‐reader bias. Age estimates were not validated. The oldest rough skate was 9 years old, but few were more than 6 years old. Females may live longer than males. The combined sexes von Bertalanffy growth curve was L_r = 91.3 (1 ‐ e^?0.16[^{t + 1.20}]). Half the males matured by c. 52 cm pelvic length (PL) and 4 years, and females by 59 cm PL and 6 years. The oldest smooth skate in the sample was 24 years, but longevity probably exceeds that. Females appear to live longer than males. The combined sexes von Bertalanffy growth curve was: L_t = 150.5 (1 ‐ e^{?0.095[t + 1.06]}). Half the males matured by c. 93 cm PL and 8 years, and females by 112 cm PL and 13 years. Smooth skate are late maturing and long‐lived relative to other skates, whereas rough skate are early maturing with a moderate life span.  相似文献   

A stimulating (but uneven) textbook on Ice Age Earth     

ÓLAFUR INGÓLFSSON 《Boreas: An International Journal of Quaternary Research》1992,21(2):187-189

Book reviewed in this article:
Dawson, Alastair, G. 1992: Ice Age Earth. Late Quaternary Geology and Climate  相似文献   

DEPENDENCE OF ROTATION VELOCITY OF INDIVIDUAL SUNSPOTS ON THEIR LIFETIME     

Abuzeid  Bashir  Marik  MiklÓs 《Solar physics》1997,173(1):25-29

By using a large number (452) of individual sunspots or individual sunspots with small spots around them, taken from the Greenwich Photoheliographic Results (GPR) for the years 1964–1976 that cover solar cycle No. 20, it is shown that the rotation velocity of the sunspots varies with their lifetimes. This investigation indicates that at the equator, the rotation rate for the last three days (of the lifetime) is about 1.3% slower than that over the whole lifetime and about 0.5% slower than during the first three days, but this is reversed at high and low latitudes, and the difference is much larger in the northern hemisphere than in the southern hemisphere. These results confirm to the fact that the rotation rate of the solar layers increases with depth.  相似文献   

The sedimentology of the Late Pleistocene Bannow Till stratotype,County Wexford,southeast Ireland     

David J.A. Evans  Colm Ó Cofaigh 《Proceedings of the Geologists' Association. Geologists' Association》2008,119(3-4):329-338

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Geophysical characterization of buried active faults: the Concud Fault (Iberian Chain,NE Spain)   总被引：2，自引：0，他引：2  

Óscar Pueyo Anchuela  Paloma Lafuente  Luis Arlegui  Carlos L. Liesa  José L. Simón 《International Journal of Earth Sciences》2016,105(8):2221-2239

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Early Pleistocene palaeoenvironments at the time of the Homo antecessor settlement in the Gran Dolina cave (Atapuerca,Spain)     

HUGUES‐ALEXANDRE BLAIN  GLORIA CUENCA‐BESCÓS  FRANCESC BURJACHS  JUAN MANUEL LÓPEZ‐GARCÍA  IVÁN LOZANO‐FERNÁNDEZ  JORDI ROSELL 《第四纪科学杂志》2013,28(3):311-319

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Glacimarine lithofacies,provenance and depositional processes on a West Greenland trough‐mouth fan     

C. Ó Cofaigh  J. T. Andrews  A. E. Jennings  J. A. Dowdeswell  K. A. Hogan  A. A. Kilfeather  C. Sheldon 《第四纪科学杂志》2013,28(1):13-26

Along the West Greenland continental margin adjoining Baffin Bay, bathymetric data show a series of large submarine fans located at the mouths of cross‐shelf troughs. One of these fans, termed here ‘Uummannaq Fan’, is a trough‐mouth fan built largely by debris delivered from a fast‐flowing outlet of the Greenland Ice Sheet during past glacial maxima. Cores from this fan provide the first information on glacimarine sedimentary facies within a major West Greenland trough‐mouth fan and on the nature of Late Weichselian–Holocene glacigenic sediment delivery to this region of the Baffin Bay margin. Glacigenic debris flows deposited on the upper slope and extending to at least 1800 m water depth in front of the trough‐mouth are related to the remobilization of subglacial debris that was delivered onto the upper slope at times when an ice stream was positioned at the shelf edge. In contrast, sedimentary facies from the northern sector of the fan are characterized by hemipelagic and ice‐rafted sediments and turbidites; glacigenic debris flows are notably absent in cores from this region. Quantitative X‐ray diffraction studies of the <2‐mm sediment fraction indicate that the bulk of the sediment in the fan is derived from Uummannaq Trough but there are distinct intervals when sediment from northern Baffin Bay sources dominates, especially on the northern limit of the fan. These data demonstrate considerable variation in the nature of sediment delivery across the Uummannaq Fan when the Greenland Ice Sheet was at the shelf edge. They highlight the variability of glacimarine depositional processes operating on trough‐mouth fans on high‐latitude continental margins during the last glacial maximum and indicate that glacigenic debris flows are just one of a number of mechanisms by which such large depocentres form. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献