Author: Oscar Baeza UrreaPublisher:
ISBN:
Category :
Languages : en
Pages : 524
Book Description
Lake and Fjord Sediments as Late Glacial to Holocene Environmental and Climate Archives of the Southernmost Andes at 53°S, Chile
Author: Oscar Baeza UrreaLake and Fjord Sediments as Late Glacial to Holocene Environmental and Climate Archives of the Southernmost Andes at 53°S, Chile
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Environmental and climatic changes during the last 20,000 years were investigated along an east-west transect across the southernmost Andes (53°S) within the interdisciplinary project "Late and Post Glacial Environmental Conditions in the Range of the Southern Hemispheric Westerlies". Twelve coring locations in the different geographical, geological and vegetational zones of the transect, were selected as drill sites on the basis of parametric echo sounding sediment profiles in the fjords of the Gran Campo Nevado area. The stratigraphy of the sediment cores is based on 14C-AMS ages and tephrachronology. Sedimentological and geochemical characteristics were investigated in order to determine sediment sources and their pathways as well as climate and environmental changes. The ice retreat after the Last Glacial Maximum (LGM) is marked in a sediment core from the eastern section of the proglacial lake Seno Skyring by an ice rafted debris layer (IRD), which was formed at around 18,700 to 17,800 cal. years B.P. This indicates a rapid response of the Seno Skyring glaciers to warming of the southeast Pacific soon after the LGM. However, between around 16,000 and 13,000 cal. years B.P. this core still shows relatively high amounts of Andean-derived glacial clay, characterized by high-MgO andesitic composition with low SiO2/Al2O3 ratios. This suggests a still extended glaciation of the Andes and a slowdown of the ice retreat. Further towards the Andes a core from an ancient glacial valley (Estero Vogel) contains an IRD layer formed at around 13,600 cal. years B.P, indicating a still extended glaciation at that time. Moreover, subaquatic ridges located in an echo sounding profile of Estero Vogel are interpreted as a moraine system, which can be related to a moraine system identified in the middle section of the Gajardo Channel. These moraines may be coeval with the moraine E system in the Strait of Magellan dated 15,043±607 to 12,275±201 cal. years B.P. by Clapperton et al.).
Ice Age Southern Andes
Author: C.J. HeusserPublisher: Elsevier
ISBN: 0080534384
Category : Science
Languages : en
Pages : 257
Book Description
The Southern Andes, stretching from the subtropics to the subantarctic, are ideally located for palaeoenvironmental research. Over the broad and continuous latitudinal extent of the cordillera (-24˚), vegetation is adjusted to climatic gradients and atmospheric circulation patterns. Opposed to the prevailing Southern Westerlies, the Southern Andes are positioned to receive the brunt of the winds, while biota are set to record the shifting of incoming storm systems over time. Sequential, latitudinally-placed, sedimentary deposits containing microfossils and macroremains, as archives of past vegetation and climate, make possible the detection of equatorward and poleward displacement of plant communities and, as a consequence, changes in climatic controls. No terrestrial setting in the Southern Hemisphere is so unique for palaeoenvironmental reconstruction during and since the last ice age. Twenty radiocarbon-dated fossil pollen and spore records chosen to place emphasis on the last ice age include high-resolution, submillennial data sets that also cover the Holocene, thus providing contrast between present interglacial and past glacial ages. From a refined data base, the records constitute the foundation for interpreting factors responsible for vegetation change over >50,000 14C years, glacial-interglacial migration and refugial patterns for a diversity of taxa, and the extent of intrahemispheric and polar hemispheric synchroneity versus asynchroneity.
Late Holocene High-resolution Quantitative Climate Reconstructions from Varved and Non-varved Lake Sediments in Southern Chile, Patagonian Andes (40 - 47°S)
Author: Julie ElbertLate Pleistocene and Holocene Sediments Around South Georgia
Author: Nina-Marie LešićPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
The island of South Georgia, along with a number of other smaller islands, is part of a microcontinent surrounded by oceanic crust in the Atlantic sector of the sub-Antarctic. Oceanographically, South Georgia lies within the Antarctic Circumpolar Current (ACC), the broad oceanic current system that is driven by the Southern Hemisphere Westerlies (SHW) and climatically isolates the Antarctic continent from the warmer Northern Hemisphere. Its location in the middle of the ACC and its isolation from continental influences makes South Georgia a sensitive region, where climate changes are registered earlier than on the more thermally isolated Antarctic continent. So far, however, the timing and extent of the Last Glacial Maximum on South Georgia have not been completely resolved, mostly because radiocarbon dated sediment investigations are missing. This is mainly due to the lack of marine geological studies on the continental shelf of the southern side of the island, which is climatically much harsher and therefore less accessible than the northern side. This information, however, is important to create and evaluate reliable climate and ice sheet models. This thesis, based on the investigations of sediment cores, sediment echosounder profiles and high-resolution bathymetry data, closes important knowledge gaps in the King Haakon Trough System and Drygalski Fjord System on the southern shelf of South Georgia. For the latter, the radiocarbon-dated sediments reveal an extensive ice cap before 30 ka BP during the Local Last Glacial Maximum. In the King Haakon Trough System, the bathymetric and sediment echo-graphic mapping of this thesis also reveal shelf-wide glaciation, possibly related to the last glacial period. Furthermore, this thesis investigates the subsequent deglaciation and the traces left by climate variability and its drivers within the sedimentary records in the two cross-shelf troughs. The results show that the southern shelf environments were ice-free since before the Antarctic Cold Reversal and thus exposed to currents at least since the start of the Holocene. These likely reacted to climate fluctuations of the present interglacial and, therefore, impacted trough sedimentation. Thus, this thesis does not only provide evidence for past ice-extent, which is crucial for benchmarking modelling approaches, but also gives further insight into the Holocene climate variability and sedimentary processes around South Georgia, potentially even archiving shelf-intruding behaviour of the nearby Southern Antarctic Circumpolar Current Front (SACCF) for at least the last 8 ka BP.
Late Glacial and Holocene Environmental Change Inferred from Sedimentary Archives of Kusawa Lake, Boundary Range Mountains, Yukon Territory, Canada
Author: Nicole Angela ChowPublisher:
ISBN: 9780494593356
Category :
Languages : en
Pages : 414
Book Description
Modern Kusawa Lake (60° 19' 55" N, 136° 4' 48" W, 142 km2) of southwestern Yukon Territory drains a 4290 km 2 catchment, 4.7% of which is glacier covered. Sediment cores show variability both down-lake and within specific sub-basins of the lake. In Regions II--V of Kusawa Lake, sediments are mainly clastic with massive to weakly laminated silts and clays interrupted by fine sand units, which reflect distinct runoff events into Region IV from glacier sources. In Region I, massive silts, silt-clay couplets are interrupted by thick sand deposits derived from the Primrose River delta. Further up-lake, the sediment record is further interrupted by modern sediment delivery from the Kusawa Campground alluvial fan.The relatively small accumulation of lake glacial and Holocene sediment input in Kusawa Lake is similar to other large lakes of the Canadian Cordillera. These patterns reflect a particular style of deglaciation and Holocene sediment inputs.
Glaciation and climate change in the andean cordillera
Author: Jacob M. BendlePublisher: Frontiers Media SA
ISBN: 2832515525
Category : Science
Languages : en
Pages : 322
Book Description
Holocene Paleohydrology of the Tropical Andes from Lake Records
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 14
Book Description
Two century-scale time series in northern Bolivia constrain the ages of abrupt changes in the physical, geochemical, and biological characteristics of sediments obtained from lakes that formed during deglaciation from the late Pleistocene glacial maximum. The watersheds of Laguna Viscachani (16°12'S, 68°07'W, 3780m) and Lago Taypi Chaka Kkota (16°13'S, 68°21'W, 4300m), located on the eastern and western slopes of the Cordillera Real, respectively, contain small cirque glaciers. A high-resolution chronology of the lake sediments is provided by 23 AMS 14C dates of discrete macro-fossils. Late Pleistocene glaciers retreated rapidly, exposing the lake basins between 10,700 and 9700 14C yr B.P. The sedimentary facies suggest that after 8900 14C B.P. glaciers were absent from the watersheds and remained so during the middle Holocene. An increase in the precipitation-evaporation balance is indicated above unconformities dated to about 2300 14C yr B.P. in both Lago Taypi Chaka Kkota and Laguna Viscachani. An abrupt increase in sediment accumulation rated after 1400 14C yr B.P. signals the onset of Neoglaciation. A possible link exists between the observed millennial-scale shifts in the regional precipitation- evaporation balance and seasonal shifts in tropical insolation.
Lake sediments - archives of late quaternary climatic and environmental changes
Author: Martin MellesHolocene Glacial Variability Recorded in Lake Sediments from Nevado Huaguruncho, Peru
Author: Christopher M. SedlakPublisher:
ISBN:
Category :
Languages : en
Pages : 46
Book Description
Abstract: Glaciers and lakes are recorders of high altitude climate changes, and these archives are important in our understanding of past global changes. This study aims to provide further insight into how temperature and precipitation varied in the past, and combined to drive glacial variability in the tropical Andes of South America. A percussion core was taken in the field at Lake Yanacocha located in the watershed of Nevado Huaguruncho, Peru. Bulk density was measured along the profile of core and the chronology was determined by measuring radiocarbon on macrofossil samples within the sediments. The core geochemistry was analyzed using scanning X-Ray Fluorescence (XRF), Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and coulometry. Changes in clastic sediment concentrations in the Yanacocha sediment core are represented by shifting values of Ti, K, bulk density, organic carbon, and residual flux. High clastic sediment values characterize the early Holocene, followed by low values during most of the early stages of the mid-Holocene, at a time the lake sediments suggest there was a period of more arid conditions. There is a notable increase in clastic sediments starting at the end of the mid-Holocene, and again during the late Holocene. This study, when paired with other similar research, further improves our knowledge of the timing and causes of climate variability in the tropical Andes, and suggests that glaciers during the Holocene advanced at times of both colder and wetter conditions.