Bengal (India). Several other large rivers in Bangladesh and India provide smaller contributions. Turbidity currents have transported the sediment through a series of submarine canyons, some of which are more than in length, to be deposited in the Bay of Bengal up to 30 degrees latitude from where it began. To date, the oldest sediments recovered from the Bengal fan are from Early Miocene age. Their mineralogical and geochemical characteristics allow to identify their Himalayan origin and demonstrate that the Himalaya was already a major mountain range 20 million years ago. The fan completely covers the floor of the Bay of Bengal. It is bordered to the west by the continental slope of eastern India, to the north by the continental slope of Bangladesh and to east by the northern part of Sunda Trench off Myanmar and the Andaman Islands, the accretionary wedge associated with subduction of the Indo-Australian Plate beneath the Sunda Plate and continues along the west side of the Ninety East Ridge. The Nicobar Fan, another lobe of the fan, lies east of the Ninety East Ridge. The fan is now being explored as a possible source of fossil fuels for the surrounding developing nations. The fan was first identified by bathymetric survey in the sixties by Bruce C. Heezen and Marie Tharp which identified the abyssal cone and canyon structures. It was delineated and named by Joseph Curray and David Moore following a geological and geophysical survey in 1968. Oceanographic chemistry Coastal regions bordering the Bay of Bengal are rich in minerals. Sri Lanka, Serendib, or Ratna – Dweepa which means Gem Island. Amethyst, beryl, ruby, sapphire, topaz, and garnet are just some of the gems of Sri Lanka. Garnet and other precious gems are also found in abundance in the Indian states of Odisha and Andhra Pradesh. A 2014 study found that as a result of ocean acidification, there was reduced shell thickness of marine animals and breaking strength compared to normal shells. The study also showed that the pH in Bay of Bengal fell to 7.75 compared in 1994 when it averaged 7.95. Oceanographic climate From January to October, the current is northward flowing, and the clockwise circulation pattern is called the "East Indian Current". The Bay of Bengal monsoon moves in a northwest direction striking the Nicobar Islands, and the Andaman Islands first end of May, then coast of Mainland India by end