摘要:

Interpretation of weathered glacial and interglacial deposits in the lower King Valley suggests that the Early Pleistocene Thureau Formation is conformably overlain by the Regency Formation. Pollen analysis of the Regency Formation provides evidence of a new climatic stage, the Regency Interglacial. The interglacial deposit consists of humified peat overlain by drifted wood and leaves. The pollen analysis shows a transition from montane scrub rainforest to lowland temperate rainforest dominated byLagarostrobos franklinii, Nothofagus cunninghamiiandPhyllocladus aspleniifolius.Trace quantities of the speciesQuintinia psi‐latisporaandGothanipollis perplexus, now both extinct in Tasmania, were also recorded. On the basis of intense chemical weathering and correlation with sediments that have a reversed magnetization the weathered glacial deposits of the Thureau Formation are thought to be older than 730,000 B.P. The eroded interglacial deposit rests on the weathered deposits and is buried by outwash gravels of the David Formation, which was deposited during an ice advance of the Middle Pleistocene Henty Glaciation (c. 150,000 B.P.). Comparison of the Regency site with a site 2 km to the south at Baxter Rivulet shows that the unconformity between the interglacial deposit and the overlying outwash gravel represents the erosion of the evidence for the Middle Pleistocene Moore Glaciatio

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1990.tb00415.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1990.tb00416.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Oxygen and carbon isotope analyses are described from a marl series of Lake Vanhalampi, NE Finland, covering the time interval between about 9,000 and 4,000 to 3,000 years B.P. Both oxygen and carbon isotope ratios show consistent trends through time, apparently in response to significant environmental changes. Maximum 6lsO levels of ‐12.0 on average are found in the Boreal Chronozone and minimum levels of –13.3 on average in the Subboreal Chronozone, with intermediate values during Atlantic time. A sharp decline occurs at the Atlantic/Subboreal transition between 5,000 and 4,000 years B.P. The δ15O trends are primarily believed to reflect trends in summer temperatures. The results from Lake Vanhalampi are compared with those from Lake Narotch in northwestern Beloru

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1990.tb00417.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The brachiopodMacandrevia cranium(Müller, 1776) occurs in Late Weichselian and Holocene sediments from the Norwegian continental shelf. It is particularly well known from the southern Barents Sea where it is a characteristic member of the Holocene macrofpssil assemblages. The Recent biogeography of the species is established. The general distribution is not random, but is almost completely confined to the continental shelves surrounding the North Atlantic and the Norwegian‐Greenland Sea. The distribution pattern is compared with information on autecology and possible limiting environmental factors. It is concluded that there is substantial evidence that the distribution of RecentM. craniumis a function of dispersal by the Gulf Stream and its continuations, e.g. the Norwegian Current and the North Cape Current. Thus the stratigraphic occurrence ofM.craniumin sediments on the Norwegian continental shelf may be used as an important marker for the presence of Atlantic water. Late Weichselian records of rare specimens of the species are related to incipient influx of Atlantic water following the deglaciation. Early Holocene records of abundant specimens are related to the final intrusion of the Norwegian Current. These records also suggest that the Holocene introduction of the species is time‐transgressive in a south‐north dir

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1990.tb00418.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1990.tb00419.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Palaeomagnetic measurements have been carried out on lava flows and volcaniclastic sedimentary rocks of Upper Pliocene and Pleistocene age from sections on the Tjömes Peninsula and a core section from the island of Flatey off North Iceland. Earlier palaeomagnetic work in the area is reviewed, and new data on the stratigraphy of the Hoskuldsvik Group on Tjörnes are presented. A revised polarity column based on our resultsisset upfortheoutcropson Tjörnes, including twoadditionalnormalsubchronswithin the Matuyama. Our palaeomagnetic results indicate that the rocks penetrated by the Flatey drillhole accumulated during the Matuyama. Age estimates for the Upper Tjömes sequence are reviewed, and correlation alternatives indicate that the earliest glaciation of Tjörnes took place either at c.2 Ma or near the Gauss/Matuyama boundary atc.2.5 Ma. Correlation of individual Matuyama subchrons remains uncertain. A comparison of the climatic evidence from the Tjörnes area with data on oxygen isotope and carbonate variations at DSDP site 552A is used to evaluate correlation alterna

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1990.tb00420.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Glaciotectonics in the limelight, LENA ADRIELSSON

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1990.tb00421.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A number of magnetic parameters have been measured on samples from a master sequence in Lake Adran, eastern Sweden. Based on the results, frequency dependent magnetic susceptibility, high isothermal rem‐anence magnetization and different magnetic ratios have been calculated. The results from the master sequence have also been compared with magnetically analysed soil samples from the lake catchment. The results of the magnetic analyses show that the sediments in Lake Ådran originate from two sources, one regional and one local. The different sources can be related to water level changes during the Ancylus and Litorina stages. Sediments originating from the regional source are characterized by high ferrimagnetic to antiferromagnetic ratios (high S‐ratios) and are assumed to have been deposited when the water level was well above the threshold. Sediments derived from the catchment, having lower S‐ratios, are assumed to have been deposited when the basin was cut off from the regional water circulation. On the basis of the magnetic results, combined with pollen and diatom analyses, tentative water level changes for the Lake Adran basin are co

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1990.tb00422.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Five new palynological sequences in the Bresse valley (France), covering Reuverian, Praetiglian, Tiglian and Eburonian‐Waalian times, yielded rodent teeth of theMimomys occitanus‐savinilineage evolving in Eurasia by phyletic gradualism. For the first time the west European palynological zonation is correlated with the Eurasiatic rodent one, leading to the following attributions:Mimomys occitanus:Reuverian;Mimomys polonicus: Praetiglian to early Tiglian;Mimomyspliocaenicus: Tiglian;Mimomys ostramosensis:Eburonian to early Waalian;Mimomys savinioccurring from Waalian to Cromerian. As a result, the Neogene biozones MN15 to MN17 can be defined by nine new subdivisi

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1990.tb00423.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Quartz sand grains in late Quaternary deposits of the Virunga Mountains, northwestern Rwanda, were found to contain glacial‐crushing microtextures. Glacially‐crushed subangular grains generally lack sharp edges, and carry mainly low frequency, linear crushing features. Because there are no known tills in the Virunga Volcanoes (and because quartz is rare in volcanic terrain), it is likely the grains were delivered by aeolian transport from the Ruwenzori Massif, ‐150 km to the north. All the grains studied are consistent with crushing under low shear stress, and over short transport distances, in alpine glaciers. An increase in the percentage of glacially‐crushed quartz from Holocene to Pleistocene beds likely reflects on the increased strength of the paleowind system (trade winds) during the last glacial maximum. Alternatively, it could reflect on the increased source area for glacially‐crushed grains resulting from an increase in the extent of the Afroalpine belt during the last g

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1990.tb00424.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY