Academic literature on the topic 'Junggar Alatau'

In 1967‑2015, Institute of Geography of the USSR/Russian Academy of Sciences together with other organizations carried out field expeditions in different areas of mountain and polar glaciations in many regions: the Polar Urals, Caucasus, Pamir, Zailiysky and Jungar Alatau, Tien‑Shan, Pamir‑Alai, the Kamchatka Peninsula, the Pyrenees, the Arctic – Spitsbergen, Novaya Zemlya, Franz Josef and Severnaya Zemlya, and Antarctica – on the ice flow B, and in the sub‑Antarctic – Islands King George, Galindez, and Livingston. The gravimetric and ground and aerial radar observations were made in these expeditions. About 300 glaciers of different morphological types and sizes with cold, subpolar and temperate thermal regime were studied. Basic results of these studies are the following: (1) the new data on the ice thicknesses, ice volumes, subglacial relief, internal structure, and thermal state of the glaciers were obtained; (2) the two‑layered (polythermal) glaciers consisting of the upper layer of cold ice and the lower layer of temperate water‑filled ice had been revealed in Svalbard for the first time; spatial distribution of cold, polythermal and temperate glaciers had been determined; (3) the evidences were obtained that measured changes in thickness of the upper cold ice layer in polythermal glaciers can be used to estimate the long‑period variations of regional climates and serve as regional paleothermometers; (4) methods for estimating the water content in temperate and polythermal glaciers from the RES data were developed; and its space‑time variations in temperate ices of the Svaldbald glaciers were estimated since even small water content inside of them can noticeably change their dynamic behavior; (5) methods for estimating the ice volume within glaciers in large regions of mountain and polar glaciations had been created; the ice storages were estimated in Svalbard, Franz Josef Land, Dzhungrsky Alatau, the Great Caucasus, and Mt. Elbrus; (6) detailed data on the ice thicknesses and the subglacial relief had been obtained for 40 glaciers in framework of different national and international programs and projects; the data can be used to solve a wide range of practical and theoretical problems, including numerical modeling. These studies demonstrated the following: (1) the use of monopulse radars VIRL‑6 and VIRL‑7 of decameter range (the central frequency is 20 MHz) with digital recording of the radar and GPS data is quite efficient for ground‑based and airborne (from helicopters) radio‑echo sounding of mountain and polar glaciers with their ice thicknesses up to 500–600 m; (2) it was found that thicknesses of glaciers in the Caucasus and Tien Shan can reach 330–430 m, while in regions of mountain, ice‑sheet and transitional glaciation on the Spitsbergen Archipelago – 300, 560 and 600 m, respectively, on the ice caps of the Franz‑Josef Land and Severnaya Zemlya – 450 and 813 m, and on King George and Livingston Islands (Sub‑Antarctica) – 330 and 500 m; (3) large parts of ice caps and outlet glaciers in Svalbard, Franz Josef Land, Severnaya Zemlya which beds were located below the sea level were found. Precisely these parts can be undergone quick shortening due to climate warming, and, thus, cause formation of icebergs making threats for ships and gas‑oil marine platforms in the Barents and Kara seas; (4) data of the measurements made possible to calculate volumes of a number of investigated glaciers and ice caps and to estimate the ice storages in large areas of mountain and polar glaciations (the Jungar Alatau, Great Caucasus, Spitsbergen, Franz Josef Land); (5) decreasing of glacier volumes on the Franz Josef Land and some Spitsbergen glaciers for the last decades had been estimated. Analysis of the data obtained had shown that considerable part of polythermal glaciers in Spitsbergen belong to type of surging glaciers; they have the winter englacial runoff and form the near‑glacier icings. It allows considering such glaciers as dynamically unstable, predisposed to surges as well as possible sources of winter water supply and additional sources of paleoinformation about long‑period variations of regional climate.

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The Junggar Alatau is located along the border of SE Kazakhstan and NW China, representing the western extent of the northern Chinese Tian Shan within the Central Asian Orogenic Belt. This study applies apatite U–Pb and low temperature thermochronology to constrain the exhumation history of the Junggar Alatau through the Meso-Cenozoic period. Apatite U–Pb results record Ordovician-Permian ages, reflecting the post-magmatic cooling of granitoids that intruded during the progressive closure of the Palaeo-Asian Ocean. Apatite fission track data obtained from Palaeozoic basement and (meta)sedimentary samples record (partial) preservation of post-magmatic cooling ages and suggests at least two subsequent cooling periods during the Late Triassic (~230–210 Ma) and Early Cretaceous (~150–120 Ma). Permian-Triassic cooling signals are preserved in low-relief areas distal to major NW-SE orientated shear zones, reflecting post-magmatic cooling during the Palaeo-Asian Ocean closure and regional exhumation in response to the Qiangtang collision. The Early Cretaceous rapid cooling signal is localised for samples taken along the Central Kazakhstan Fault Zone (CKFZ). The record of younger signals localised in the CKFZ suggests the reactivation of faulting during the Early Cretaceous, which can be linked to a phase of slab-rollback and associated extension in the distant Tethys Ocean. Cretaceous exhumation is thought to have induced rapid cooling in the exhuming footwalls with respect to subsiding hanging walls of the CKFZ. Additionally, few samples from higher relief areas record Late Cretaceous cooling, although there is no consensus on the cause. The results obtained in this study indicate that the extent of Cenozoic exhumation within Central Asia has not propagated to the Junggar Alatau. Results obtained in this work fit with those obtained from samples along other major NW-SE orientated shear zones in the vicinity of the study area, improving the overall understanding of strain propagation through Central Asia.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2018