摘要:

AbstractEaster Island occupies an exceptionally isolated position in the south Pacific Ocean. It is entirely volcanic, and is famous for its giant statues. Late Quaternary sediments have been investigated in three craters: Rano Raraku, Rano Aroi and Rano Kao, giving a continuous record over the past 30 Ka. Pollen records indicate that the island was formerly forested. Palynological and sedimentological evidence suggests a Late Pleistocene climate slightly cooler and drier than the present. Deforestation by people occurred mainly between 1200 and 800 yr BP. This may have led to an ecological disaster and to the decline of the megalithic civilization. The depauperation of the present native flora owes more to human activity than to isolation.

ISSN:0267-8179    

DOI:10.1002/jqs.3390060202

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe Balderton Terrace marks a former course of the River Trent between Newark and the Lincoln Gap. The principal deposit, the Balderton Sand and Gravel, is interpreted as a braided river sediment. Ice wedge casts truncated by intraformational erosion surfaces at many levels indicate syndepositional permafrost. Remnant cover deposits overlying the Balderton Sand and Gravel include the partly aeolian Whisby Sand. Locally, both the upper part of the Balderton Sand and Gravel and the cover deposits exhibit features indicative of temperate climate pedogenesis. All these deposits are affected by subsequent cryoturbation. On the basis of these features and the geomorphological and topographical relationship to other terrace deposits of the area, the Balderton Sand and Gravel and Whisby Sand are regarded as post‐Hoxnian and pre‐lpswichian, i.e. Wolstonian. Electron spin resonance age determinations for fossil elephant teeth and amino acid analyses on molluscs from the Balderton Sand and Gravel suggest correlation with Oxygen Isotope Stage 6. The Balderton Sand and Gravel has yielded a cold‐climate mammalian fauna dominated by woolly mammoth and woolly rhinoceros, though rarer species suggest periods of milder climate. Silts from channels near the base of the deposit have produced pollen, mollusc, ostracod and beetle assemblages also indicating a cold cl

ISSN:0267-8179    

DOI:10.1002/jqs.3390060203

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe Balderton Sand and Gravel has yielded one of very few mammalian faunas dated to the penultimate Cold Stage in Britain. The assemblage is dominated by mammoth and woolly rhinoceros, with subordinate horse, red deer, bison, straight‐tusked elephant, musk ox, reindeer, wolf, lion, brown bear and cf. narrow‐nosed rhinoceros. This fauna indicates cold stage conditions, probably including one or more interstadial episodes. The presence of straight‐tusked elephant and cf. narrow‐nosed rhinoceros supports its pre‐Devensian age, and provides corroboration for the occurrence of these taxa in the British Wolstonian. An attempt is made to analyse the fossil collection by preservation type and adhering sediment: the occurrence of individual species appears to be largely uncorrelated with lithology. The Balderton assemblage corresponds well to other British mammal faunas assigned to a cold interval between the Hoxnian and Ipswichian Inte

ISSN:0267-8179    

DOI:10.1002/jqs.3390060204

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractFour Quaternary volcanic ash zones in the southern Norwegian Sea have been investigated in core P57‐7 from the Iceland Plateau. Both the geochemical composition and morphological variation of each ash layer have been studied. The four volcanic ash zones appear in the light oxygen isotope stages 1, 5, 7 and 11. The ash zones are composed of transparent platy grains, light brown transparent grains, brown blocky and black blocky grains and white/transparent pumice, and each zone shows a distinct stratigraphic evolution. The geochemical results show a mixture of basaltic and silicic grains in each ash zone, and that each zone contains grains from more than one eruption. The geochemical investigations strongly suggest that all the ashes are derived from Iceland. The youngest ash zone includes two layers, which based on their geochemical composition and stratigraphic position are correlated with the14C‐dated Vedde Ash (10 600 yr BP) and Saksunarvatn Ash (9 100 yr BP). Possible sources on Iceland for these layers are discus

ISSN:0267-8179    

DOI:10.1002/jqs.3390060205

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

ISSN:0267-8179    

DOI:10.1002/jqs.3390060206

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

ISSN:0267-8179    

DOI:10.1002/jqs.3390060207

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

ISSN:0267-8179    

DOI:10.1002/jqs.3390060201

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY