Abstract

The Indus River carries sediments from the western Himalaya and deposits some of these as channel and floodplain sediments or molasse. The rest of its load forms the Indus delta at the margin of the Indian Ocean. The Indus delta passes some of its sediments to be deposited as Indus submarine fan turbidites. Thus, as elsewhere, Himalayan molasse, delta, and fan deposition are related hi tune and space. However, when we examine fluvial and marine age-range data of the older Indus deposits, in terms of this sedimentary assemblage, a major portion of its marine record is missing. The oldest known molasse along the Indus suture zone, and hi the foredeep are middle Eocene and late Palaeocene hi age, respectively. A recent synthesis of sedimentation in the northern Indian Ocean, however, shows that turbidite sedimentation started around early Miocene in the modern Indus fan, and even later in the Bengal fan. Where are the Palaeogene Indus delta and fan sediments? We suggest herein that these are preserved as the Palaeogene siliciclastic Khojak Formation hi the Katawaz Basin and eastern Makran.

The modern Indus River is 2900 km long (Coumes & Kolla 1984) and has 30 000 m3 s − 1 discharge (Milliman et al. 1984) in summer (Fig. 1), twice that of the Mississippi River. The annual suspended sediment load (Wells & Coleman 1984) varies between 395 and 435 x 103 t, almost equal to that of the Mississippi. The existence of the middle Eocene to middle Miocene Indus molasse along the

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