Relative sea-level change in the Beauly Firth, Scotland     

B. ANDREW HAGGART 《Boreas: An International Journal of Quaternary Research》1986,15(2):191-207

Relative sea-level changes in the Beauly Firth have been inferred from stratigraphy, pollen and diatom analyses and by radiocarbon dating of former coastal reedswamp deposits. Using lithostratigraphic and biostratigraphic arguments for establishing the changes in coastal environment at the site, a preliminary scheme of positive and negative tendencies of sea-level is produced. This may be related to changes in relative sea-level. Two periods of falling relative sea-level have been identified: (1) between c . 9,600 B.P. and c . 8,800 B.P. and (2) post c . 6,400 B.P. The period of rising relative sea-level between c . 8,800 B.P. and c . 6,400 B.P. was interrupted briefly by a possible storm surge event which took place between c . 7,200 B.P. and c . 7,300 B.P.  相似文献   

Re‐dating the Pilgrimstad Interstadial with OSL: a warmer climate and a smaller ice sheet during the Swedish Middle Weichselian (MIS 3)?     

HELENA ALEXANDERSON  TIMOTHY JOHNSEN  ANDREW S. MURRAY 《Boreas: An International Journal of Quaternary Research》2010,39(2):367-376

Alexanderson, H., Johnsen, T. & Murray, A. S. 2009: Re‐dating the Pilgrimstad Interstadial with OSL: a warmer climate and a smaller ice sheet during the Swedish Middle Weichselian (MIS 3)? Boreas, 10.1111/j.1502‐3885.2009.00130.x. ISSN 0300‐9483. Pilgrimstad in central Sweden is an important locality for reconstructing environmental changes during the last glacial period (the Weichselian). Its central location has implications for the Scandinavian Ice Sheet as a whole. The site has been assigned an Early Weichselian age (marine isotope stage (MIS) 5 a/c; >74 ka), based on pollen stratigraphic correlations with type sections in continental Europe, but the few absolute dating attempts so far have given uncertain results. We re‐excavated the site and collected 10 samples for optically stimulated luminescence (OSL) dating from mineral‐ and organic‐rich sediments within the new Pilgrimstad section. Single aliquots of quartz were analysed using a post‐IR blue single aliquot regenerative‐dose (SAR) protocol. Dose recovery tests were satisfactory and OSL ages are internally consistent. All, except one from an underlying unit that is older, lie in the range 52–36 ka, which places the interstadial sediments in the Middle Weichselian (MIS 3); this is compatible with existing radiocarbon ages, including two measured with accelerator mass spectrometry (AMS). The mean of the OSL ages is 44±6 ka (n=9). The OSL ages cannot be assigned to the Early Weichselian for all reasonable adjustments to water content estimates and other parameters. The new ages suggest that climate was relatively mild and that the Scandinavian Ice Sheet was absent or restricted to the mountains for at least parts of MIS 3. These results are supported by other recent studies completed in Fennoscandia.  相似文献   

Correction     

JOHN COOPER 《Geology Today》1993,9(5):178-178

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THE ATMOSPHERE AND WEATHER OF SOUTHERN AFRICA     

ANDREW STURMAN 《New Zealand geographer》1991,47(2):90-91

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Modelling of late Quaternary climate over Asia: a synthesis     

ANDREW B. G. BUSH 《Boreas: An International Journal of Quaternary Research》2004,33(2):155-163

Through the late Quaternary, the global climate system ranged from full glacial to temperate interglacial conditions. On a smaller spatial scale, regional climates of the late Quaternary exhibited fluctuations that were at times asynchronous to these global changes. For example, glacier expansion in the Himalayas during the mid-Holocene appears to be at odds with the notion of increased global temperature. A clear understanding of the dynamical processes governing regional climate is therefore essential to the correct interpretation of proxy climate data. We summarize results from numerical simulations of the Last Glacial Maximum (LGM) and the mid-Holocene, and focus on the multiple processes that control regional climate of the Himalaya and surrounding areas, with emphasis on monsoon dynamics and variability. It is shown that changes in the south Asian monsoon (caused by fluctuations in Earth's orbital parameters, by tropical Pacific Ocean temperatures, or by exposure of the Sunda shelf) alter the hydrological balance in regions bordering the Tibetan Plateau, a balance for which there are extensive continental proxy records. Numerical results correlate with the expansion/contraction cycles of deserts near the Chinese Loess Plateau. In addition, the LGM monsoon exhibits significant snow accumulation in the eastern Himalaya, whereas the mid-Holocene monsoon exhibits increased accumulation in the northwestern Himalaya. Simulated changes are therefore in accord with field data and demonstrate that numerical simulations can be a useful tool in the interpretation of regional proxy data, particularly when those data are asynchronous to global records.  相似文献   

Calcretes,fluviolacustrine sediments and subsidence patterns in Permo‐Triassic salt‐walled minibasins of the south Urals,Russia     

ANDREW J. NEWELL  MICHAEL J. BENTON  TIMOTHY KEARSEY  GRAEME TAYLOR  RICHARD J. TWITCHETT  VALENTIN P. TVERDOKHLEBOV 《Sedimentology》2012,59(5):1659-1676

The south Uralian foreland basin forms part of the giant, yet sparsely documented, PreCaspian salt tectonic province. The basin can potentially add much to the understanding of fluviolacustrine sedimentation within salt‐walled minibasins, where the literature has been highly reliant on only a few examples (such as the Paradox Basin of Utah). This paper describes the Late Permian terrestrial fill of the Kul’chumovo salt minibasin near Orenburg in the south Urals in which sediments were deposited in a range of channel, overbank and lacustrine environments. Palaeomagnetic stratigraphy shows that, during the Late Permian, the basin had a relatively slow and uniform subsidence pattern with widespread pedogenesis and calcrete development. Angular unconformities or halokinetic sequence boundaries cannot be recognized within the relatively fine‐grained fill, and stratigraphic and spatial variations in facies are therefore critical to understanding the subsidence history of the salt minibasin. Coarse‐grained channel belts show evidence for lateral relocation within the minibasin while the development of a thick stack of calcrete hardpans indicates that opposing parts of the minibasin became largely inactive for prolonged periods (possibly in the order of one million years). The regular vertical stacking of calcrete hardpans within floodplain mudstones provides further evidence that halokinetic minibasin growth is inherently episodic and cyclical.  相似文献   

THE GEOGRAPHICAL REVIEW'S HISTORICAL DIMENSIONS AND RECENTISM*     

ANDREW SLUYTER 《Geographical review》2010,100(1):6-11

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SWISS POSCHIAVINI IN AUSTRALIA     

ANDREW D. TRLIN 《New Zealand geographer》1991,47(2):95-96

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Evidence for plant-arthropod interactions in the fossil record     

ANDREW C. SCOTT 《Geology Today》1991,7(2):58-61

From a study of extant arthropods (particularly insects) and plants it is clear that there are many close interactions between the two groups, which must have co-evolved over a considerable period of time. Surprisingly, the fossil record of such interactions has hardly been studied and has therefore often been assumed to be non-existent. Interactions include feeding (e.g. leaf and spore/pollen feeding, leaf mining and wood boring), shelter (e.g. the formation of galls), transport, and reproduction (flower pollination). There is fossil evidence for all of these interactions from the time that arthropods and plants first colonized the land. The shortage of data results from lack of study rather than a real absence of interactions.  相似文献   

Origin of hibonite-pyroxene spherules found in carbonaceous chondrites     

STEVEN B. SIMON  ANDREW M. DAVIS  LAWRENCE GROSSMAN  ERNST K. ZINNER 《Meteoritics & planetary science》1998,33(3):411-424

Abstract— We have studied both of the known glass-free, hibonite-pyroxene spherules: MYSM3, from Murray (CM2), and Y17–6, from Yamato 791717 (CO3). They consist of hibonite plates (～2 wt% TiO^tot₂) enclosed in Al-rich pyroxene that has such high amounts of CaTs (CaAl₂SiO₆) component, up to ～80 mol%, that it must have crystallized metastably. Within the pyroxene, abundances of MgO and SiO₂ are strongly correlated with each other and are anticorrelated with those of Al₂O₃, reflecting an anticorrelation between the diopside and CaTs components of the pyroxene. In contrast with previous results for Type B fassaite, however, we do not observe an anticorrelation between MgO and TiO^tot₂, possibly reflecting different relative distribution coefficients for Ti³⁺ and Ti⁴⁺ in the aluminous pyroxene of the spherules from those found for fassaite in Type B inclusions. Previously described hibonite-silicate spherules have ²⁶Mg deficits but the present samples do not. Furthermore, the pyroxene in Y17-6 has excess ²⁶Mg, while the hibonite it encloses does not, indicating that the two phases either had different initial ²⁶Al/²⁷Al ratios or different initial ²⁶Mg/²⁴Mg ratios. The Ti isotopic compositions of the present samples are highly unusual: δ⁵⁰Ti = 103.4 ± 5.2%o in MYSM3 and -61.4 ± 4.1%0 in Y17-6, which are among the largest ⁵⁰Ti anomalies reported for any refractory inclusion. The textures suggest that hibonite crystallized first; but based on the calculated bulk compositions of both spherules, it is not the liquidus phase in either sample, which suggests that the hibonite in both samples is relict. The presence of ragged hibonite grains in MYSM3 and rounded hibonite grains in Y17-6 and a lack of isotopic equilibrium between pyroxene and hibonite support this conclusion. The spherules crystallized from liquid droplets that probably formed as a result of the melting of solid precursor grains that included hibonite. The heating events were too short and/or not hot enough to melt all the hibonite. The droplets cooled quickly enough that CaTs-rich pyroxene crystallized instead of anorthite. Based on the observed differences in isotopic composition, it is unlikely that the precursors of the present samples formed in the same reservoir as each other or as the previously described hibonite-silicate spherules, providing further evidence of the isotopic heterogeneity of the early solar nebula.  相似文献