Quaternary glacial chronology and neotectonics in the Himalaya of northern Pakistan

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 Parbat Himalaya. 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 degrees 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 degrees 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.