Search results for "Glaciation"

A high-resolution record of the last deglaciation in the Sicily Channel based on foraminifera and calcareous nannofossil quantitative distribution

2003

Abstract Relative abundance fluctuations in planktic foraminiferal and calcareous nannofossil assemblages are reported on the basis of a high-resolution study of ODP Leg 160 Hole 963D, drilled in the Sicily Strait, near Capo Rossello (southern Sicily). With its 8 m of undisturbed sediments, the core covers the interval from 1.5 to 23 kyr, allowing a 50–100-yr sampling resolution. All the short warm and cold events and sub-events recorded in this time interval in the GRIP Greenland ice core and at several Mediterranean sites were recognized. On this basis, a total number of nine ecozones based on planktic foraminifera and seven ecozones based on calcareous nannofossils were identified. A sho…

South Asian monsoon climate change and radiocarbon in the Arabian Sea during early and middle Holocene

2002

The 1 4 C ages of planktonic foraminifers Globigerinoides sacculifer bracketing the Younger Dryas in a δ 1 8 O record of Globigerinoides ruber from a laminated sediment core on the Pakistani continental margin suggest thatsurface reservoir ages in the Arabian Sea were in excess of 1000 years during the deglaciation. A least squares error fit of a detailed 1 4 C chronology to the (atmospheric) tree ring record gave variable early Holocene reservoir ages between 780 and 1120 years, well above the prebomb value of 640 years. Mid-Holocene reservoir ages are less well constrained but were probably closer to the prebomb value. The method used to fit individual core sections to the tree ring recor…

Kēmu terases Latvijas starplobu izometriskajās augstienēs

2013

Elektroniskā versija nesatur pielikumus

The arid–humid transition in the Sahara and the Sahel during the last deglaciation

1990

At the time of the Last Glacial Maximum, the Sahara and Sahel regions of North Africa were extremely dry. New records of rainfall show that during the subsequent deglaciation, the transition from arid to humid conditions in these regions occurred synchronously in two main steps. Comparison with other records of palaeoclimate in Europe and the North Atlantic Ocean shows that certain common factors controlled changes in ocean and atmosphere dynamics during the deglaciation.

Chemostratigraphy, magnetostratigraphy, chronology, palaeoenvironments and correlations.

2013

4 pages

Sedimentation in the Kandi extensional basin (Benin and Niger): fluvial and marine deposits related to the Late Ordovician deglaciation in West Africa

2003

Abstract The Lower Paleozoic detrital succession of the half-graben Kandi Basin in West Africa (Niger-Benin) is about 600 m thick and rests unconformably on the Pan-African basement. Along the western edge of the basin, the base of the succession locally features large glacial fault-bounded paleovalleys. These valleys are filled by the lowermost continental deposits of the Were Formation characterized by massive diamictites with dropstones, and coarse to conglomeratic sandstones associated with large-scale channel structures and internal erosional truncations. The uppermost braided-river deposits of the Were Formation deposited across the entire basin are overlain by the Late Ordovician–Ear…

Prehistoric land use at an archaeological hot-spot (the rock art park of Campo Lameiro, NW Spain) inferred from charcoal, synanthropic pollen and non…

2013

Pollen, non-pollen palynomorphs and charcoal from a colluvial soil surrounded by prehistoric petroglyphs (Campo Lameiro, NW Spain) were studied in order to assess the nature of human activities and their impact on Holocene vegetation patterns. Several phases of anthropogenic impact were observed. (i) Between 7.6 and 6.5 ka cal BP, synanthropic taxa (Urtica dioica type, Plantago lanceolata type) and coprophilous fungi (e.g. Sporormiella-type) are indicative of early (pre-agricultural) creation of small patches of pasture using fire, possibly for incipient animal husbandry or as part of a deliberate strategy to improve game availability. Such activities only had a minor effect on the deciduou…

Upper Pleistocene biostratigraphy and traces of glaciotectonics at the Satiki site, western Latvia

2007

Structural, lithological, palynological and plant macroremain investigations of test-boring cores and gravel pit walls at the Satiki site suggest that gyttja and sandy gyttja units of basin sediments were deposited during the Felicianova (Eemian) Interglacial. A pollen diagram reflects the characteristic forest succession of the Eemian Interglacial: Betula, Pinus, Ulmus, Corylus, Quercus, Fraxinus, Tilia, Carpinus, Picea and Pinus. Forests of broadleaved trees and thermophilous plants dominated in the surroundings of the lake during the interglacial climatic optimum. The basin sediments contain a large number of warmth-demanding water plants such as Salvinia natans and Trapa sp. Paleobotani…

Outlines of the Quaternary geology of Latvia

2014

Sedimentological and deformational criteria for discriminating subglaciofluvial deposits from subaqueous ice-contact fan deposits: A Pleistocene exam…

2014

A pit located near Ballyhorsey, 28 km south of Dublin (eastern Ireland), displays subglacially deposited glaciofluvial sediments passing upwards into proglacial subaqueous ice-contact fan deposits. The coexistence of these two different depositional environments at the same location will help with differentiation between two very similar and easily confused glacial lithofacies. The lowermost sediments show aggrading subglacial deposits indicating a constrained accommodation space, mainly controlled by the position of an overlying ice roof during ice-bed decoupling. These sediments are characterized by vertically stacked tills with large lenses of tabular to channelized sorted sediments. The…