<P> The metamorphic basement consists of gneisses which are further classified into the Bengal gneiss, the Bundelkhand gneiss and the Nilgiri gneiss . The Nilgiri system comprises charnockites ranging from granites to gabbros . </P> <P> Rocks of the earliest part of the Cambrian Period are found in the Salt range in Punjab and the Spiti are in central Himalayas and consist of a thick sequence of fossiliferous sediments . In the Salt range, the stratigraphy starts with the Salt Pseudomorph zone, which has a thickness of 450 feet (137 m) and consists of dolomites and sandstones . It is overlain by magnesian sandstones with a thickness of 250 feet (76 m), similar to the underlying dolomites . These sandstones have very few fossils . Overlying the sandstones is the Neobolus Shale, which is composed of dark shales with a thickness of 100 feet (30 m). Finally there is a zone consisting of red or purple sandstones having a thickness of 250 feet (76 m) to 400 feet (122 m) called the Purple Sandstone . These are unfossiliferous and show sun - cracks and worm burrows which are typical of subaerial weathering . The deposits in Spiti are known as the Haimanta system and they consist of slates, micaceous quartzite and dolomitic limestones . The Ordovician rocks comprise flaggy shales, limestones, red quartzites, quartzites, sandstones and conglomerates . Siliceous limestones belonging to the Silurian overlie the Ordovician rocks . These limestones are in turn overlain by white quartzite and this is known as Muth quartzite . Silurian rocks which contain typical Silurian fauna are also found in the Vihi district of Kashmir . </P> <P> Devonian fossils and corals are found in grey limestone in the central Himalayas and in black limestone in the Chitral area . The Carboniferous is composed of two distinct sequences, the upper Carboniferous Po, and the lower Carboniferous Lipak . Fossils of brachiopods and some trilobites are found in the calcareous and sandy rocks of the Lipak series . The Syringothyris limestone in Kashmir also belongs to the Lipak . The Po series overlies the Lipak series, and the Fenestella shales are interbedded within a sequence of quartzites and dark shales . In many places Carboniferous strata are overlaid by grey agglomeratic slates, believed to be of volcanic origin . Many genera of productids are found in the limestones of the Permo - Triassic, which has led to these rocks being referred to as "productus limestone". This limestone is of marine origin and is divided into three distinct lithostratigraphic units based on the productus chronology: the Late Permian Chideru, which contains many ammonites, the Late--Middle Permian Virgal, and the Middle Permian Amb unit . </P> <P> In the Triassic the Ceratite beds, named after the ammonite ceratite, consist of arenaceous limestones, calcerous sandstones and marls . The Jurassic consists of two distinct units . The Kioto limestone, extends from the lower the middle Jurassic with a thickness 2,000 feet (610 m) to 3,000 feet (914 m). The upper Jurassic is represented by the Spiti black shales, and stretches from the Karakoram to Sikkim . Cretaceous rocks cover an extensive area in India . In South India, the sedimentary rocks are divided into four stages; the Niniyur, the Ariyalur, the Trichinopoly (a district in the Madras Presidency, covering present - day districts of Tiruchirappalli, Karur, Ariyalur and Perambalur), and the Utatur stages . In the Utatur stage the rocks host phosphatic nodules, which constitute an important source of phosphates in the country . In the central provinces, the well developed beds of Lameta contain fossil records which are helpful in estimating the age of the Deccan Traps . This sequence of basaltic rocks was formed near the end of the Cretaceous period due to volcanic activity . These lava flows occupy an area of 200,000 square miles (520,000 km). These rocks are a source of high quality building stone and also provide a very fertile clayey loam, particularly suited to cotton cultivation . </P>

In india rocks of which of the following regions was formed the earliest