Geomorphic processes influence human settlement on two islands in the Islands of Four Mountains, Alaska

2018 ◽  
Vol 91 (03) ◽  
pp. 953-971 ◽  
Author(s):  
Lyman Persico ◽  
Henry Lanman ◽  
Lydia Loopesko ◽  
Kale Bruner ◽  
Kirsten Nicolaysen
Keyword(s):  
Debris Flow ◽  
Aleutian Island ◽  
Human Settlement ◽  
Sector Collapse ◽  
Fine Grained ◽  
Anthropogenic Deposits ◽  
Geomorphic Surfaces ◽  
The Last Glacial Maximum ◽  
Geomorphic Processes ◽  
The Last Glacial

AbstractThe Islands of Four Mountains island group of the Aleutian island arc is remote and difficult to access. Consequently, little fieldwork has focused on geomorphic processes and their relationship to island morphology, climatic change, and human settlement. We investigated glacial, fluvial, and slope processes on the morphologically different Carlisle, Cleveland, and Tana volcanoes. The islands were extensively glaciated at the last glacial maximum (LGM), and there is evidence for a Neoglacial advance. On the highly dissected Tana volcano, a large basin is likely the result of a pre-LGM sector collapse and subsequent glacial erosion into weak hydrothermally altered rock. Valley and moraine morphology is also influenced by hydrothermal alteration. On both Tana and Carlisle, there are sediment fans composed dominantly of thick debris flow deposits mantled by ~3 m of layered tephras, fine-grained alluvium, and anthropogenic deposits. Debris flow deposition was favored during the unstable paraglacial landscape of the early Holocene–latest Pleistocene. The earliest direct archaeological evidence for settlement is 3.8 cal ka BP, but soil geochemical evidence suggests that the islands were inhabited by 7.3 cal ka BP. This discrepancy in the archaeological record may be explained by geomorphic processes including coastal erosion and unstable geomorphic surfaces.

scholarly journals Caracterização paleohidrológica de estruturas sedimentares quaternárias através de análises macroscópias e microscópicas: do registro sedimentar local aos indícios de mudanças globais

2001 ◽  
Vol 28 (2) ◽  
pp. 183 ◽  
Author(s):  
MARCELO ACCIOLY TEIXEIRA DE OLIVEIRA ◽  
GISELE CAMARGO ◽  
JULIO CÉSAR PAISANI ◽  
MAURÍCIO CAMARGO FILHO
Keyword(s):  
Environmental Changes ◽  
Microscopic Analysis ◽  
Ice Cores ◽  
Evolutionary Pattern ◽  
Global Environmental ◽  
The Tropics ◽  
Global Environmental Changes ◽  
Geomorphic Surfaces ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Preliminary results based on macroscopic and microscopic analysis of quaternary sedimentary structures and paleosoils preserved on footslope deposits are presented in this paper. Together with geochronologic estimates for the main pedo-stratigraphic units, the paper suggests an evolutionary pattern for geomorphic surfaces situated at the highlands of the States of Paraná and Santa Catarina, Southern Brazil. the association of that pattern with global environmental changes is postulated. Based on sedimentologic and geomorphologic evidences, paleohydrologic interpretations suggest the predominance of relative wet local climates at the end of the Pleistocene. Indeed, 14C ages of paleosoils in the study area suggest the development of organic and hydromorphic soils during the coldest periods of isotopic stages 3 and 2. As peat horizons need anaerobic conditions to fully develop, such a result lead us to challenge the predominant role attributed to lower precipitation as a cause of geomorphic and vegetation changes during the Quaternary in the tropics and subtropics. Indeed, together with lower precipitation. Lower temperatures and, most important, an excess of precipitation over evaporation should be considered as the same importance. In so far, the indication of waterlogged soils, even during the Last Glacial Maximum, well explain the pattern of evolution of geomorphic surfaces and related pedo-stratigraphic features in the area. Indeed, taking into account the calibrated isotopic curves from Antarctic ice cores for the last 40 ka, we conclude that soil development and colluvial building by diffuse processes prevailed during Stadials, while pulses of erosive incision punctuated Insterstadials.

scholarly journals Glacial landform-sediment assemblages in the Canadian High Arctic and their implications for late Quaternary glaciations

1999 ◽  
Vol 28 ◽  
pp. 195-201 ◽  
Author(s):  
C. Ó Cofaigh ◽  
D.S. Lemman ◽  
D.J.A. Evans ◽  
J. Bednarski
Keyword(s):  
Thermal Regime ◽  
Late Quaternary ◽  
Thermal Conditions ◽  
High Arctic ◽  
Early Holocene ◽  
Canadian High Arctic ◽  
Fine Grained ◽  
Quaternary Glaciation ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractModern terrestrial glaciers in the Canadian High Arctic range from polythermal to cold-based. Where polythermal glaciers override thick unconsolidated sediment, longitudinal compression and glaciotectonic thrusting produce thrust-block moraines. In contrast, the dominant geomorphic record of cold-based glaciers consists of lateral and proglacial meltwater channels. Geomorphic and sedimentary evidence indicates that late Quaternary fiord glaciers were also characterized by variations in basal thermal regime. Erratic dispersal trains and striated bedrock record the flow of warm- based ice during the Last Glacial Maximum. Emergent grounding-line fans and morainal banks, deposited during deglaciation, consist of heterogeneous glaciomarine deposits that record well-developed subglacial drainage and high sedimentation rates. However, in other fiords, subaqueous outwash and fine-grained glaciomarine deposits are absent and deglaciation is recorded by lateral meltwater channels graded to raised glaciomarine deltas, suggesting these glaciers were predominantly cold-based during retreat. Regionally, deglacial depocentres are located at pinning points within fiords and a prominent belt of glaciogenic landforms at fiord heads records stabilization of ice margins during early Holocene retreat, rather than the limit of late Quaternary glaciation. Collectively, these observations refute previous reconstructions which inferred a climatically controlled switch from cold- to warm-based thermal conditions in fiord glaciers during early Holocene deglaciation, and indicate that the dominant controls on thermal regime were glaciological.

Comparison of Thermoluminescence and Radiocarbon Age-Determinations from Late-Pleistocene Alluvial Deposits Near Sydney, Australia

1987 ◽  
Vol 27 (3) ◽  
pp. 263-269 ◽  
Author(s):  
G.C. Nanson ◽  
R.W. Young
Keyword(s):  
New South ◽  
River System ◽  
Main Body ◽  
Alluvial Deposits ◽  
Radiocarbon Age ◽  
Fine Grained ◽  
South Wales ◽  
The Last Glacial Maximum ◽  
Age Determinations ◽  
The Last Glacial

AbstractRadiocarbon and thermoluminescence (TL) age-determinations have been obtained for a large Pleistocene alluvial terrace on the Nepean River near Sydney, New South Wales, Australia. The deposit was laid down by a braided river system prior to the last glacial maximum. Six thoroughly pretreated samples of charcoal and degraded wood buried within gravels at the base of the terrace yielded apparent 14C ages of ∼37,000–42,000 yr B.P. These compare favorably with four TL determinations that gave apparent ages of ∼41,000–47,000 yr B.P. for the same deposit. Adjustment of the 14C ages to take geomagnetic effects into account further improves the correlation between these two independent dating techniques. In addition, 14C and TL correctly identified a reworked portion of the fine-grained alluvial overburden as being substantially younger than the main body of the terrace. These results augur well for the usefulness of TL age determinations of certain alluvial deposits.

A 40,000-yr record of environmental change from Burial Lake in Northwest Alaska

2010 ◽  
Vol 74 (1) ◽  
pp. 156-165 ◽  
Author(s):  
Mark B. Abbott ◽  
Mary E. Edwards ◽  
Bruce P. Finney
Keyword(s):  
Lake Level ◽  
Organic Matter Content ◽  
Lacustrine Sediments ◽  
Matter Content ◽  
Radiocarbon Dates ◽  
Fine Grained ◽  
Shrub Tundra ◽  
Northern Alaska ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractBurial Lake in northwest Alaska records changes in water level and regional vegetation since ∼ 39,000 cal yr BP based on terrestrial macrofossil AMS radiocarbon dates. A sedimentary unconformity is dated between 34,800 and 23,200 cal yr BP. During all or some of this period there was a hiatus in deposition indicating a major drop in lake level and deflation of lacustrine sediments. MIS 3 vegetation was herb-shrub tundra; more xeric graminoid-herb tundra developed after 23,200 cal yr BP. The tundra gradually became more mesic after 17,000 cal yr BP. Expansions of Salix then Betula, at 15,000 and 14,000 cal yr BP, respectively, are coincident with a major rise in lake level marked by increasing fine-grained sediment and higher organic matter content. Several sites in the region display disrupted sedimentation and probable hiatuses during the last glacial maximum (LGM); together regional data indicate an arid interval prior to and during the LGM and continued low moisture levels until ∼ 15,000 cal yr BP. AMS 14C dates from Burial Lake are approximately synchronous with AMS 14C dates reported for the Betula expansion at nearby sites and sites across northern Alaska, but 1000–2000 yr younger than bulk-sediment dates.

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