Stratigraphy

Geology -B.Sc. Semester Vth -Paper II (Mesozoic to Quaternary Stratigraphy) Prof. S K Kulshrestha / Dr. Sanjay Shukla Unit- I - Mesozoic Era After close of Palaeozoic Era commenced Mesozoic Era of Transition between Palaeozoic and Cenozoic which continued for about 120 Ma.

The term Mesozoic Era was introduced by Jonh Phillips in 1840 for The Rock Formation containing remains/fossils of “Middle forms of Life”. The Mesozoic Era has been further subdivided into three periods:

1. Triassic 2. Jurassic 3. Cretaceous

Triassic Period (Triassic Group)

The name Triassic was coined by Friedrich von Alberti. In 1834, after three-fold development of rocks of this period in Europe (Alps). Example Bunter, Muschelkalk and Keuper. The Triassic Period lasting for about 40 Ma ended about 140 Ma.

Distribution of Triassic Rocks in India

In India, the three well worked division of Triassic period are well developed in Himalaya in approximately 900 m thick deposits in Spiti Garhwal, Kumaon and Kashmir. At Lilang in Spiti valley, complete section is exposed showing a succession from The Permian to the Jurassic rocks. These marine rocks mostly comprise variegated shales, slates, limestone, dolomites, calcareous shales and red sandstone interrelated with layer of rock salt, gypsum, Alabaster and partly colored sand and clays.

The Terrestrial Rocks of this period are found in Satpura and Godawari regions. The successional orders of these rocks are known as to form Panchet, Mahadev and Maleri Formation.

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Stratigraphy

Triassic Succession of Spiti

Division Name of Formations Description of Beds Thicknss (m) LIAS Kioto (Megalodon) Massive Limestone and Dolomites 500 Limestone Massive Limestone and Dolomite (with Spirigera 250 moetlingi, Megalodon ladakhensis ) Quartzite Formation White and brown Quartzites with Grey Limestone and 100

black Shales (with Spirigera maniensis)

Monotis Shales Sandy and Shaly limestone with Monotis 100

NORIC Coral Limestone Limestone with Coral and Crinoids 30 Juvavites beds Shale, Limestone and Sandstone with Juvavites 150

Tropites beds Dolomitic Limestone with Tropites 300

Upper Triassic Grey beds Grey Shales and Shaly Limestones 150

CARNIC Halobia beds Dark splintery Limestone with Halobia 45

Daonella Limestone Dark Limestone with Daonella indica 45

Daonella Shales Limestone and Shale with Daonella lammeli 50

LADINIC Upper Muschelkalk Concretionary Limestone with Shale bands 6 Lower Muschelkalk Dark Shale and Grey Limestone 2

K

Middle Triassic Middle Nodular Limestone Hard nodular Limestone with few fossil 20

Basal Muschelkalk Shaly Limestone with Rhynchonella 1

MUSCHELKAL Limestone with Pseudomonotis 1

Hedenstromia beds. Shaly Limestone (unfossiliferous) 8

Thin bedded Limestone with Hedenstromia 2 Meekoceras Zone Limestone and Shale with Meekoceras varaha 1

BUNTER BUNTER Ophiceras Zone Grey Limestone with Ophiceras 0.3

Lower Triassic Otoceras Zone Brown Limestone with Otoceras 0.6 Permian Productus Shale Dark Shale with Permian Fossils ?

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