Age derminations of rocks from the Read Mountains, Antarctica

The Shackleton Range can be divided into three major units: (1) The East Antarctic Craton and its sedimentary cover (Read Group and Watts Needle Formation), (2) the allochthonous Mount Wegener Nappe (Mount Wegener Formation, Stephenson Bastion Formation, and Wyeth Heights Formation), and (3) the northern belt (basement: Pioneer and Stratton Groups, sedimentary cover: Haskard Highlands Formation (allochthonous?), and Blaiklock Glacier Group). The northern units are thrust over the southern ones. The thrusting is related to the Ross Orogeny. The Mount Wegener Nappe, which appears to be a homogeneous tectonic unit, consists of a Precambrian basement (Stephenson Bastion Formation, Wyeth Heights Formation?) and a Cambrian cover (Mount Wegener Formation). Some questions are still open for discussion: the position of the Haskard Highlands Formation (trilobite shales) may be erratic or represent a tectonic sliver, the relation of the former Turnpike Bluff Group, the origin of the crystalline basement west of Stephenson Bastion and others.

(Table 1) Luminescence datings from Varchushka and Pyoza rivers, Russia

The Pyoza River area in the Arkhangelsk district exposes sedimentary sequences suitable for study of the interaction between consecutive Valdaian ice sheets in Northern Russia. Lithostratigraphic investigations combined with luminescence dating have revealed new evidence on the Late Pleistocene history of the area. Overlying glacigenic deposits of the Moscowian (Saalian) glaciation marine deposits previously confined to three separate transgression phases have all been connected to the Mikulinian (Eemian) interglacial. Early Valdaian (E. Weichselian) proglacial, lacustrine and fluvial deposits indicate glaciation to the east or north and consequently glacier damming and meltwater run-off in the Pyoza area around 90-110 ka BP. Interstadial conditions with forest-steppe tundra vegetation and lacustrine and fluvial deposition prevailed at the end of the Early Valdaian around 75-95 ka BP. A terrestrial-based glaciation from easterly uplands reached the Pyoza area at the Early to Middle Valdaian transition around 65-75 ka BP and deposited glaciofluvial strata and subglacial till (Yolkino Till). During deglaciation, laterally extensive glaciolacustrine sediments were deposited in ice-dammed lakes in the early Middle Valdaian around 55-75 ka BP. The Barents-Kara Sea ice sheet deposited the Viryuga Till on the lower Pyoza from northerly directions. The ice sheet formed the Pyoza marginal moraines, which can be correlated with the Markhida moraines further east, and proglacial lacustrine deposition persisted in the area during the first part of the Middle Valdaian. Glacio-isostatic uplift caused erosion followed by pedogenesis and the formation of a deflation horizon in the Middle Valdaian. Widely dispersed periglacial river plains were formed during the Late Valdaian around 10-20 ka BP. Thus, the evidence of a terrestrial-based ice sheet from easterly uplands in the Pyoza area suggests that local piedmont glaciers situated in highlands such as the Timan Ridge or the Urals could have developed into larger, regionally confined ice sheets. Two phases of ice damming and development of proglacial lakes occurred during the Early and Middle Valdaian. The region did not experience glaciation during the Late Valdaian.