Younger Glaciation Research Articles

Glacial Landforms as Geodiversity Resources for Geotourism in Tierra del Fuego, Argentina

Abstract The southern extreme location and the natural landscapes, highly modelled by glaciers during the Quaternary period, give Tierra del Fuego a unique opportunity to attract visitors worldwide. Its glacial landforms are geodiversity resources that are witness to global climate changes as natural processes. Therefore, this study aims to highlight different glacial landforms considering their geodidactic potential for educational information in terms of geographical study. Sixteen georesources connected by routes are analysed, using bibliographic research, fieldwork and a datasheet designed ad-hoc. Four of them were formed during middle Pleistocene glaciations and the other twelve during the Last Glacial Maximum (LGM), out of which two also represent the Holocene, which happens to be the youngest glaciation.

Pleistocene deposits in the western part of the Holy Cross Mountains

The paper presents characteristics of the Pleistocene sediments in the western part of the Holy Cross Mountains. They are subdivided into four complexes and their stratigraphic setting is referred to the updated scheme for the Pleistocene of Poland. The Preglacial Complex includes fluvial sediments characteristic for its lack of Scandinavian material. Sediments of three main glaciations (Nidanian, Sanian 1 and Sanian 2) within the South Polish Complex, are referred also as the South Polish Glaciations. The oldest of these glaciations (Nidanian) is separated from the middle glaciation (Sanian 1) by sediments of the Podlasian Interglacial, represented by clay at the Kozi Grzbiet Cave that contains faunal remains and record of the Brunhes/Matuyama palaeomagnetic boundary. During the middle (Sanian 1) and youngest glaciation (Sanian 2), the Holy Cross Mountains were almost completely covered by the Scandinavian ice sheet, forming glacial deposits separated by fluvial series of the Ferdynandovian Interglacial. The Middle Polish Complex begins with sediments of the Mazovian Interglacial, represented by a pollen record from the Zakrucze site. They are followed by deposits of periglacial and fluvial origin of the Liwiecian Glaciation, Zbójnian Interglacial, Krznanian Glaciation and Lublinian Interglacial. The following glaciation (Odranian) is represented by the youngest glacial deposits that document presence of the Scandinavian ice-sheet in the westernmost part of the Holy Cross Mountains. The North Polish Complex is composed of a climatic warming (Eemian Interglacial) and cooling (Vistulian Glaciation), and is represented by valley and periglacial deposits. The last cooling of the Pleistocene is recorded in faunal remains in the Raj Cave.

Characterization and engineering properties of AMU Morasko soft clay

AMU Morasko soft clay is the normally consolidated, postglacial clayey silty sand to sandy clay, deposited during the last glaciation (Weichselian) within the marginal zone of end moraine of Posnanian Phase. These soils are characterized by low plasticity, high porosity and are fully saturated, therefore, from a geotechnical point of view they can be defined as soft clays. The over 10 meter thick complex of clayey glacial sediments is covered with fine and medium sands with single grains of gravel of the so-called first sandur level from the youngest glaciation. This kind of sediments are very common in the area of north-western Poland and, due to high compressibility, become a problematic subsoil for the shallow foundations. The high porosity and saturation also causes significant problems in obtaining high quality samples for laboratory tests. This means that in situ tests are very often the only possible and economically justifiable test methods. Extended investigations carried out on these clays, which provide reliable correlations between in situ and laboratory test results, will be very useful. For the purpose of this research paper, a wide variety of in situ (CPTU, DMT, FVT) and laboratory (physical properties, direct shear, oedometer) tests have been carried out on the material found at the depth of up to 16 m, in the area of 8 ha, within the campus of Adam Mickiewicz University (AMU) in Poznan, Poland. Preliminary investigations (performed four years ago) showed high uniformity of the test site. The current laboratory tests were carried out on both high quality natural samples and reconstructed samples. The rate effect on the results of some of the tests was also investigated. The obtained results allowed to present a wide geological and engineering characterization of these interesting glacial deposits.

Reconstruction of a complex late Quaternary glacial landscape in the Cordillera de Cochabamba (Bolivia) based on a morphostratigraphic and multiple dating approach

Although glacial landscapes have previously been used for the reconstruction of late Quaternary glaciations in the Central Andes, only few data exist for the Eastern Cordillera in Bolivia. Here, we present results from detailed morphostratigraphic mapping and new data of surface exposure dating (SED), optically stimulated luminescence (OSL), and radiocarbon dating ( 14C) from the Huara Loma Valley, Cordillera de Cochabamba (Bolivia). Discrepancies between individual dating methods could be addressed within the context of a solid geomorphic framework. We identified two major glaciations. The older is not well constrained by the available data, whereas the younger glaciation is subdivided into at least four major glacial stages. Regarding the latter, a first advance dated to ~ 29–25 ka occurred roughly contemporaneous with the onset of the global last glacial maximum (LGM) and was followed by a less extensive (re-)advance around 20–18 ka. The local last glacial maximum (LLGM) in the Huara Loma Valley took place during the humid lateglacial ~ 17–16 ka, followed by several smaller readvances until ~ 10–11 ka, and complete deglaciation at the end of the Early Holocene.

Quaternary glacial, lacustrine, and fluvial interactions in the western Noatak basin, Northwest Alaska

The 130 km long Noatak basin is surrounded by mountains of the western Brooks Range. Middle and late Pleistocene glaciers flowing southeast into the basin dammed a succession of proglacial lakes defined by shorelines, outlet channels, and upper limits of wave erosion. More than 60 bluffs along the Noatak River and its principal tributaries expose glacial and glaciolacustrine sediments that exhibit cut-and-fill relationships with interglacial and interstadial river-channel and floodplain deposits. This report focuses on the western Noatak basin, where high bluffs created by deep postglacial erosion record four major glacial advances. During the Cutler advance, a floating ice tongue terminated in a large proglacial lake that filled the Noatak basin. The retreating glacier abandoned a trough along the valley center that subsequently filled with about 40 m of sediment during several younger glaciations and probably two major interglacial episodes. Alluvium that formed near the beginning of the younger interglaciation contains the 140,000 yr old Old Crow tephra. The subsequent closely spaced Okak and Makpik advances are clearly younger than the maximum of the last interglaciation, but they preceded a middle Wisconsin (36–30 ka) nonglacial interval in the Noatak basin. The Okak advance terminated in an extensive lake, whereas glaciers of the Makpik and the subsequent Anisak advances flowed into much narrower lakes that filled only the basin center. The Anisak advance, bracketed by radiocarbon ages of about 35 and 13.6 ka, represents the Last Glacial Maximum (LGM) in the western Noatak basin. Correlations with the oldest and youngest glacial deposits of the central Brooks Range are clear, but relationships to events of intermediate age are more tenuous. Early Pleistocene and older glacial advances from the central Brooks Range must have filled the Noatak basin and overflowed northward through Howard Pass. A younger glacial advance, of inferred middle Pleistocene (Sagavanirktok River) age, extended down the Noatak valley into the basin center, but its deposits are deeply buried beneath the basin floor and must be older than the Cutler moraine. The Cutler advance may have been synchronous with the older of two advances of Itkillik I age in the Atongarak Creek area, but other evidence indicates that the Okak-Makpik moraine succession more likely was synchronous with the two Atongarak Creek moraines. Radiocarbon ages, surface morphology, soil and weathering profiles, and lake-level history all support correlation of the last (Anisak) major glacial advance in the western basin with the Douglas Creek moraine farther east and with Itkillik II (late Wisconsin) glaciation of the central Brooks Range.

Late Proterozoic glacial carbonates in northeast Spitsbergen: new insights into the carbonate–tillite association

AbstractCarbonate-rich glacial deposits from two discrete Vendian glacial periods are described. The older is represented by the 24–40 m thick Petrovbreen Member (E2) of the Elbobreen Formation which contains abundant detrital dolomite. Clasts in E2 and their possible source rocks have positive δ13C and negative δ18OPDBvalues. In contrast the carbonate mud-fraction of E2 sediments has different cathodoluminescence characteristics from clasts, slightly negative δ13C values, and higher Fe and Mn concentrations than clasts. Oxygen isotopes vary from −2.5 to +4.5‰PDB, thought to be related to various seawater–meltwater mixtures in the depositional environment. Preservation of information about glacial sedimentary environments is attributed to early diagenetic recrystallization forced by excess surface free energy (Ostwald's ripening) and coinciding with sulphate reduction.The younger glaciation is represented by the Wilsonbreen Formation (170 m) which has a distinctive glaciolacustrine Middle Carbonate Member (W2). W2 contains precipitated periglacial carbonates (with high Mn/Fe ratio): both limestone (rhythmitic and stromatolitic) and dolostone (rhythmites, stromatolites and dolomite-rich sandstones) which are compared with carbonates in modern Antarctic lakes. Evaporitic environments for dolomitic sandstones and stromatolitic dolostones are indicated by heavy oxygen isotope values (up to + 10.5‰PDB), high Na concentration and evidence for dissolved evaporites. High Mn concentration in detrital dolostones in W2 is suggestive of syn-sedimentary dolomite recrystallization in freshwater diamictites and haematitic siltstones.The carbonate–tillite association ultimately arises from the erosion of underlying carbonates which originated (in this case) under radically different climatic conditions. Glacial depositional waters then became carbonate-saturated as a result of dissolution of detrital carbonate. Massive recrystallization of glacially transported carbonate is proposed as a geologically significant process with considerable potential for palaeoenvironmental analysis. In glacial lakes carbonate precipitated in response to evaporation or photosynthesis. Carbonate precipitation as the result of seawater freezing, or in warm interglacial conditions, is not yet established. Oxygen isotope value are inconsistent (too heavy) with the presence of high-latitude meltwaters, implying that glaciation extended to low latitudes as proposed by Harland.

Eruption age of a ∼100,000‐year‐old basalt from 40Ar‐39Ar analysis of partially degassed xenoliths

We have applied 40Ar‐39Ar dating, using stepwise thermal extraction of Ar, to five potassium‐rich granitic xenoliths and their host basalt from Sawmill Canyon in the Sierra Nevada, California. Previous K/Ar analyses showed the age of the basalt to be roughly 100,000 years or less. The xenoliths, which had accumulated large amounts of radiogenic 40Ar since their crystallization ∼100 m.y. ago, were partially degassed upon their inclusion in the basaltic magma. Ar released from the xenoliths in the laboratory at temperatures substantially below the melting temperature of the basalt, was created since the host magma cooled. Isotopic compositions of Ar released from the xenoliths in several extraction steps at temperatures below ∼900°C were colinear in 36Ar/40Ar versus 39Ar/40Ar diagrams and defined isochrons giving a mean age of degassing of 119,000±7000 (2σ) years. 40Ar extracted at higher temperatures included ancient radiogenic 40Ar that was never diffused from the xenoliths during immersion in the magma. This 40Ar caused an increase in the apparent age for the high‐temperature extractions. The high precision of the eruption age determined by this method is comparable to that obtained elsewhere by conventional K/Ar dating of sanidine. 40Ar‐39Ar analysis of granitic xenoliths to date young basaltic lava flows may prove to yield results superior to those found from analysis of the lava itself. Establishing the age of eruption of the basalt flow in Sawmill Canyon establishes age limits for two Sierran glaciations which left moraines stratigraphically above and below the lava. Thus the younger glaciation must be Wisconsin; the older must be pre‐Wisconsin in age.

Late Pleistocene Glaciations of the Snag-Klutlan Area, Yukon Territory

Two late Pleistocene limits of glaciation were delineated in the Snag-Klutlan area. Radiocarbon dates, surficial characteristics of its drift, and the palynology of overlying sediments imply the older glaciation (Mirror Creek) is early Wisconsin in age; the younger glaciation (Macauley) is late Wisconsin in age and culminated c. 13 700 BP. The stratigraphy of deposits within the Macauley glacial limit implies that deglaciation between the two glaciations was minimal.

Evidence of Multiple Stades in the Lower Pleistocene of Northeastern Kansas

Nebraskan and Kansan glacial and glacio-fluvial deposits in Kansas occur only in the northeastern part of Kansas. generalized four-fold history of continental glaciation has long been accepted in the United States. Generally the highest till was correlated with the youngest glaciation and an underlying till correlated with the next youngest glaciation. In areas where only early Pleistocene glaciations occurred, this same method of correlation was practiced. Recognition of a more complex system of advances and retreats of ice in the Wisconsinan Stage lead to the adoption of substage or stade division of this stage. Each of the glacial stages is separated from the succeeding glacial stage by an interglacial stage. This period was one of relative stability under comparatively warm conditions during which extensive interglacial soils were developed in the periglacial regions as well as in the glaciated regions. Buried profiles of weathering, or fossil soils, are perhaps the most usable criteria for stratigraphic correlation and classification of the Pleistocene sediments in Kansas. The top of a buried soil is unmistakably an unconformity, and where deep well-developed soil profiles occur, a significant interval of nondeposition and only slight erosion is indicated. Interpretation of the soils within the Pleistocene sequence involves the evaluation of the soil horizons as interglacial or interstadial and may lead to errors in correlation. The strength of soil development is believed to be the most important factor in this interpretation. Pronounced zones of clay enrichment in the B horizon, considerable depth of leaching, great depth of oxidation, and significant thicknesses of secondary lime accumulation are believed to be more important and better indicators of interglacial nature of soils than the thickness of the humic A horizon which often has been removed by erosion or scour. Frye and Leonard (1949, 1952) described the exposure of two tills in a quarry in the Missouri River Bluff near Iowa Point in northeastern Doniphan County. well-developed soil on the lower till was indicative of a long period of weathering prior to deposition of the upper till.

Frequence et extension des glaciations a l'extremite sud-ouest des Vosges meridionales (region de Luxeuil-les-Bains)

Abstract Two series of glacial and fluvioglacial deposits can be distinguished east and northeast of Luxeuil-les-Bains (France). Deposits of the older glaciation are found on the plateaus and probably represent the Rissian. The deposits are characterized by fluvioglacial material and erratics of basic green crystalline rocks, light colored acidic rocks, and conglomerates. The younger glaciation, probably Wuermian, is represented in the valleys by moraines and terrace deposits.

Glaciation in the Desert Ranges, Utah

Typical and reasonably well-developed moraines are present in the Deep Creek Range and its extension, the Snake Range. Two sets of moraines are present in various valleys draining the slopes of Haystack Peak (Deep Creek Range); some scanty evidence suggests a third glaciation of much greater age. Wheeler Peak and Mount Moriah (Snake Range) were definitely glaciated, rough reconnaissances indicating two ages considerably separated in time. The younger glaciations in this general area are tentatively assigned to the Later Epoch of Glaciation.' A thorough study of this area should be productive. Poorly developed moraines, nivation scars, and several types of solifluction ridges are widespread in the Oquirrh