Quaternary glacial chronology and neotectonics in the Himalaya of northern Pakistan

Abstract

Thick deposits preserved in deep valleys in the Indus, Gilgit, and Hunza River Basins, and a variety of dates, allow new definition of Quaternary events in the Karakoram and Nanga ParbatHimalaya. An unusually long record for an actively eroding high mountain area is recognized in three major episodes of glaciation during Pleistocene time. An early glaciation is represented by the indurated lower Jalipur tillites and heterogeneous upper Jalipur valley-fill sedimentary rock younger than 1 to 2 Ma, which are folded, overturned, or overridden by rapid movement on the dextral-reverse Raikot fault. This is associated with high overall uplift rates of the Nanga Parbat-Haramosh massif during late Cenozoic time. The middle glaciation is represented by two tills intercalated within variable sediments, including thick lacustrine units dipping as much as 43° along the fault. The Indus-Shatial till of the early middle glaciation records the farthest advance of Pleistocene glaciers down the Indus River valley. The last glaciation apparently occurred after about 140,000 yr ago and consists of three to four or more separate advances, as recorded by morainic topography. The most prominent of these is the Dianyor moraine near Gilgit, which was produced by a major longitudinal glacier. Near Haramosh and downstream at Nanga Parbat, Shatial, and elsewhere, transverse glaciers blocked the Indus River to produce lake deposits now dipping as much as 6° near the fault. Catastrophic floods from failure of the ice dams, and possibly landslide dams as well, emplaced some Punjab erratics and sediments that may have been reworked into loesses and other sediments at the mountain front.on July 23, 2015 specialpapers.gsapubs.org Downloaded from

The Quaternary glacial history of the Zanskar Range, north-west Indian Himalaya

“…The majority of these recognize three glacial stages, the oldest being a glaciation of a broad valley, remnants of which remain as high palaeo surfaces, with two subsequent laterally confined glacial stages, recorded by moraine ridges within deep valleys (e.g. Porter, 1970;Shroder et al, 1989;Owen et al, 1996Owen et al, , 1997. One or two minor advances are also commonly reported (e.g.…”

“…The relationship of the tillite, which outcrops at a number of valley floor localities, to the glacial sequence is disputed (el Shroder et al, 1993). An early Pleistocene age is proposed by Shroder et al (1989) on the basis that the deposits are well lithified and have undergone major tectonic deformation. The valley floor position of such old sediment, which would be expected to pre-date the valley floor fonnation, is explained by overthrusting, with the sediment protected from erosion in the foot-wall of a fault.…”

“…However, there are many unresolved issues regarding the number of stades each event had and the assignment of sediments to particular events (el Shroder et at., 1993). High level glaciated surfaces, which are deeply incised by the present valley system are recorded in most of the areas studied in the north-west Himalaya, with ice interpreted as having occupied broad valleys (Porter, 1970;Zhang and Shi, 1980;Derbyshire, et aI., 1984;Owen, 1988;Shroder et al, 1989Shroder et al, , 1993Osmaston, 1994;Owen et al, 1996;Derbyshire and Owen, 1997;Mitchell et ai., 1999). In the Hunza Valley of northern Pakistan, Derbyshire et al (1984) distinguished two palaeosurfaces with weathered erratics, ascribing these to the Shanoz and Yunz glacial stages ( Fig.…”

Timing of Late Quaternary glaciations in the Himalayas of northern Pakistan

“…Complex moraine ridges and valley fills, incised to depths of more than 100 m, provide abundant evidence for multiple glaciation throughout the Himalayas of northern Pakistan (Porter, 1970;Derbyshire et al, 1984;Owen, 1988;Shroder et al, 1989;Scott, 1992). These sediments and landforms provide a useful record of the extent of glaciation throughout late Quaternary times in this high mountain region.…”

The Quaternary glacial history of Nanga Parbat

“…The valleys radiating from the Nanga Parbat Massif contain extensive accumulations of Quaternary glaciogenic sediments. Previous glacial geologic work has concentrated on the Rakhiot valley (Sloan et al, 1998) and the middle Indus valley, north of the Nanga Parbat massif (Owen, 1988(Owen, , 1989Shroder et al, 1989Shroder et al, , 1993Richards et al, 2000a,b). Research into the genesis of thick sedimentary deposits in other northwest Himalayan regions such as Swat Kohistan (Porter, 1970), the Hunza valley (Derbyshire et al, 1984), the Gilgit-middle Indus region (Owen, 1988;Shroder et al, 1989), Kashmir (Holmes, 1988) and Lahul (Owen et al, , 1997Sharma and Owen, 1996) has attributed these sediments to a series of Quaternary glacial #uctuations.…”