of Precambrian rocks, that have been metamorphosed to one degree or another. 

 Deccan basalt covers much of Kathiawar, but the peninsula is rimmed by a variety 

 of Cretaceous and Tertiary sediments. Exposed in the Kutch are similar sediments 

 including limestones, sandstones, and shales. Most of the area between the 

 Aravalli Mountains and the west side of the Indus basin is covered by Pleistocene 

 and Recent sediments. These sediments, which range up to thousands of feet in 

 thickness, are mainly deposits of rivers of the Indo-Gangetic system . Wide ex- 

 panses of windblown quartz sand are present. This sand contains varying amounts 

 of calcareous grains. West of the Indus basin to the Pakistan-Iran border are ex- 

 posed thick sections of Tertiary sediments with Cretaceous sediments and minor 

 Eocene volcanics . Sandstones and shales dominate over limestones . The coast of 

 Iran is bounded by the Miocene Pars series consisting of marls, clays, and sand- 

 stones with some limestones and interbedded gypsum . 



Outcropping rocks of the Arabian coast are largely sedimentary although 

 Igneous and metamorphic rocks are present in significant amounts. The Carbo- 

 Trlassic Oman series, consisting for the most part of limestone, makes up the back- 

 bone of the Jebel Akhthar Range . Along the coast are widespread Pleistocene and 

 Recent sediments consisting of various types of alluvial deposits and a distinctive 

 friable limestone. Some Jurassic basic sills, made up of gabbros and diorites which 

 are much metamorphosed, crop out In several areas along the coast. Precambrian 

 high-grade metamorphic rocks of the Hatat series crop out in a small area near 

 Ra's Al Hadd. 



In summary, the regional geology from a standpoint of potential sediment 

 sources consists of volcanics, metamorphics, and minor amounts of sediments in 

 the southern portion of the study area In India . The remainder of the Indian, 

 Pakistan, and Iranian coasts are principally sedimentary rocks. The Arabian pe- 

 ninsula coast is also largely sedimentary in nature with some basic igneous and 

 and metamorphic rocks present . 



IV. MARINE ENVIRONMENT 



A . Currents 



Detailed current data are sparse . No direct current measurements were made 

 on the Arabian Sea phase of this survey. Current plots in the Atlas of Surface 

 Currents of the Indian Ocean (H . O . Pub . 566) show a surface circulation gyre 

 paralleling the coast of Arabia, crossing from Ra's Al Hadd toward Karachi and 

 south along the Indian coast. For most of the year, this clockwise circulation is 

 present, but the flow becomes slightly disrupted in October, shows some reversal 

 In November, and is entirely counter-clockwise in December and January. In 

 February, reversal occurs and by March a clockwise circulation is again established, 

 while the northeast monsoon still blows . Barlow (1934) explained this apparent 



