Geology of Odisha is a fascinating and diverse subject that provides insights into the physical structure, history, and formation of the landmass in the state. Geology is the scientific study of the Earth, encompassing its rocks, minerals, landforms, and the processes that shape them. It examines the Earth’s composition, structure, history, and the dynamic forces that have shaped our planet over millions of years. Geologists analyze rocks and minerals to understand their properties, origins, and ages, providing insights into Earth’s past climates, ancient environments, and the evolution of life. They also investigate processes such as plate tectonics, volcanism, erosion, and sedimentation to comprehend the formation of mountains, valleys, rivers, and other landforms. Geology plays a vital role in resource exploration, assessing mineral and energy deposits, groundwater resources, and environmental impact. By studying the Earth’s past and present, geologists contribute to our understanding of natural hazards, climate change, and sustainable resource management. Through fieldwork, laboratory analysis, and advanced technologies, geology provides valuable knowledge for addressing challenges related to the Earth’s past, present, and future.
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Features of Geology of Odisha
- Oldest Geological Formations: Champua in Kendujhar district of Odisha is known for hosting some of the oldest rocks on Earth, dating back 4.2 billion years. These rocks represent a significant period in Earth’s geological history and offer valuable information about the planet’s early stages.
- Cratonic Blocks: Odisha is divided into two major cratonic blocks: the North Odisha Craton and the West Odisha Craton. These cratons are stable continental blocks that have remained relatively unchanged for billions of years. The North Odisha Craton comprises extensive banded iron formations, granite intrusives, and undisturbed volcano-sedimentary assemblages dating from the Archean to the early Proterozoic. Proterozoic folded limestone-bearing rock formations follow these. The West Odisha Craton is underlain by Archean granites and undeformed Proterozoic limestone-bearing platform sediments. There are also isolated occurrences of Archean banded iron formations and greenstones in this craton.
- Eastern Ghats Granulite Belt: The Eastern Ghats Granulite Belt is a significant geological feature in Odisha. It covers an area of approximately 52,000 square kilometers and is primarily composed of Khondalite formations, along with charnockites, granites, migmatites, and local pegmatites. The belt also contains anorthosites, alkaline rocks, and ultramafic rocks containing chromite along its boundaries. The term “Khondalite” is derived from the Khond tribe, who reside in Odisha. The lithology, tectono-thermal processes, and large rift features in Odisha are similar to those found in Eastern Antarctica, highlighting the geological significance of the region.
- Gondwana Basins: Odisha is home to Gondwana basins, which represent later geological formations. The Mahanadi Master Basin is a major Gondwana basin that spans a significant portion of Odisha. It exposes sediments from the early Permian to the Early Cretaceous periods. These sedimentary basins are found in the Ib River valley, Talcher, Karinga, Gaisilat, Athmallik, Chhatrapur, and Athgarh regions. The Gondwana deposits in these basins are of great economic importance as they contain a significant portion of Odisha’s coal reserves.
- East Coast Deposits: Odisha’s eastern coast is characterized by various types of deposits. Deltaic deposits from rivers such as the Mahanadi, Brahmani, Baitarani, and Subarnarekha dominate the region. These deposits result from the deposition of sediments carried by these rivers. Additionally, aeolian (wind-driven) and marine deposits are present along the coast. The development of Odisha’s eastern coastline occurred in the post-Cretaceous period and has been influenced by river delta expansion as well as the effects of glaciation and deglaciation during the Quaternary period. The Quaternary deposits along the east coast comprise laterites, unconsolidated clays, silts, sands, and gravels.
Overall, the geology of Odisha encompasses a wide range of geological formations, from ancient rocks and stable cratons to granulite belts, Gondwana basins, and coastal deposits. These geological features provide valuable information about the history, structure, and resources of the landmass in Odisha.
Geological Time Scale
The geological time scale is a system used to divide Earth’s history into distinct time intervals, each characterized by specific geological events, environmental conditions, and the evolution of life forms. It provides a framework for understanding the vast expanse of time since the formation of the Earth. The geological time scale is divided into several major divisions, each with its own time period and significant evolutionary events. Here are the main aspects of the geological time scale:
| Eon | Era | Period | Epoch | Age / Years Before Present | Life / Major Events |
|---|---|---|---|---|---|
| Cenozoic (From 65 million years to present) | Quaternary | Holocene | 0 – 10,000 | Modern Man | |
| Pleistocene | 10,000 – 2 million | Homo sapiens | |||
| Tertiary | Pliocene | 2 – 5 million | Early Human Ancestor | ||
| Miocene | 5 – 24 million | Ape: Flowering Plants and Trees | |||
| Oligocene | 24 – 37 million | Anthropoid Ape | |||
| Eocene | 37 – 58 million | Rabbits and Hare | |||
| Palaeocene | 57 – 65 million | Small Mammals: Rats – Mice | |||
| Mesozoic (65 – 245 million years) | Cretaceous | — | 65 – 144 million | Extinction of Dinosaurs | |
| Jurassic | — | 144 – 208 million | Age of Dinosaurs | ||
| Triassic | — | 208 – 245 million | Frogs and Turtles | ||
| Palaeozoic (245 – 570 million years) | Permian | — | 245 – 286 million | Reptiles dominate; replace amphibians | |
| Carboniferous | — | 286 – 360 million | First Reptiles; Vertebrates; Coal beds | ||
| Devonian | — | 360 – 408 million | Amphibians | ||
| Silurian | — | 408 – 438 million | First trace of life on land: Plants | ||
| Ordovician | — | 438 – 505 million | First Fish | ||
| Cambrian | — | 505 – 570 million | No terrestrial life; Marine invertebrates | ||
| Proterozoic | Pre-Cambrian (570 – 4,800 million) | — | — | 570 – 2,500 million | Soft-bodied arthropods |
| Archean | — | — | 2,500 – 3,800 million | Blue-green algae; Unicellular bacteria | |
| Hadean | — | — | 3,800 – 4,800 million | Oceans and continents form; Atmosphere rich in carbon dioxide | |
| Origin of Stars | — | — | 5,000 million | Origin of the Sun | |
| Supernova / Big Bang | — | — | 12,000 – 13,700 million | Origin of the Universe |
Oldest Pre-Cambrian Formations in Odisha
The Pre-Cambrian era, spanning from approximately 4.6 billion to 541 million years ago, is a crucial period in the geological evolution of Odisha. During this era, the region experienced significant tectonic activity and the formation of various rock units. Here is a comprehensive account of the geological evolution of Odisha during the Pre-Cambrian era.
1. Archean Era (4.0 to 2.5 billion years ago):
- Basement Rocks: The Archean era witnessed the formation of the basement rocks in Odisha, which are some of the oldest rocks in the Indian subcontinent. These rocks primarily consist of granites, gneisses, and schists. They provide insights into the early stages of the region’s geological history.
2. Proterozoic Era (2.5 billion to 541 million years ago):
- Eastern Ghats Formation: During the Proterozoic era, the Eastern Ghats, including the Odisha region, started to take shape. This involved the collision of several crustal blocks, resulting in the formation of mountain ranges. The rocks in the Eastern Ghats are mainly granites, gneisses, and schists.
- Iron Ore Deposits: The Proterozoic era also witnessed the formation of significant iron ore deposits in Odisha. The Iron Ore Group (IOG) formations, consisting of banded iron formations (BIFs) and associated rocks, were deposited during this period. These deposits have been extensively mined and contribute to India’s iron ore production.
- Proterozoic Basins: Proterozoic basins, such as the North Odisha Iron Ore Basin and the Bonai-Keonjhar Belt, formed during this era. These basins contain sedimentary rocks, including shale, sandstone, and conglomerates. They also host important mineral resources such as iron ore, manganese, and chromite.
- Proterozoic Granites: Several granitic intrusions were emplaced during the Proterozoic era in Odisha. These granites are associated with the Eastern Ghats Belt and are important from an economic perspective, as they host valuable minerals like mica, feldspar, and quartz.
Palaeozoic Formations in Odisha
The Paleozoic era, spanning from approximately 541 to 252 million years ago, played a crucial role in the geological evolution of Odisha. This era witnessed significant tectonic activity, the formation of diverse sedimentary environments, and the development of important rock formations. While the available data up until September 2021 provides an understanding of this era, ongoing research may refine our knowledge further. Here is a comprehensive account of the geological evolution of Odisha during the Paleozoic era, with examples of specific rock formations.
1. Cambrian Period (541 to 485 million years ago):
- Sedimentary Deposition: During the early Cambrian, sedimentary rocks were deposited in parts of Odisha. For example, the Athgarh Formation in the Mahanadi Basin consists of sandstones, siltstones, and shales. These rocks represent shallow marine environments and may contain fossil assemblages of early marine life.
2. Ordovician Period (485 to 443 million years ago):
- Marine Sediments: The Ordovician period in Odisha is characterized by the deposition of marine sediments. The Kaimur Group, found in the northern part of Odisha, consists of shale, sandstone, and limestone. These rocks represent shallow marine environments and can contain fossilized remains of marine organisms.
3. Silurian Period (443 to 419 million years ago):
- Sedimentary Deposition: The Silurian period in Odisha witnessed the deposition of sedimentary rocks. The Talchir Formation, found in the Talcher Coalfield, comprises sandstones, shales, and siltstones. These rocks represent various environments such as deltaic, fluvial, and marine settings. Fossils found in these rocks include plant fragments, bivalves, and brachiopods.
4. Devonian Period (419 to 359 million years ago):
- Transitional Environments: During the Devonian period, Odisha experienced the deposition of sediments in transitional environments. The Kamthi Formation, found in the northern part of Odisha, represents a sequence of sandstones, shales, and limestones. These rocks reflect environments such as river deltas, estuaries, and shallow marine settings. Fossils found in these rocks include plant fragments, gastropods, and brachiopods.
5. Carboniferous Period (359 to 299 million years ago):
- Coal Formation: The Carboniferous period played a significant role in the formation of coal deposits in Odisha. The Talcher Coalfield in Odisha, part of the Mahanadi Basin, is rich in coal seams. These coal deposits formed from the accumulation and burial of swamp vegetation. The coal reserves in the Talcher Coalfield are an important energy resource for the region.
6. Permian Period (299 to 252 million years ago):
- Gondwana Sequences: The Permian period in Odisha is characterized by the deposition of sedimentary rocks known as the Gondwana sequences. These sequences consist of sandstones, shales, and coal deposits. The Ib Valley Coalfield and the Talcher Coalfield in Odisha are part of the Gondwana sequences and contain significant coal reserves. These coal deposits formed in environments ranging from fluvial to lacustrine, reflecting the diverse geological history of the region.
Mesozoic Formations in Odisha
The Mesozoic era, spanning from approximately 252 to 66 million years ago, played a significant role in the geological evolution of Odisha. This era witnessed major tectonic events, the breakup of the supercontinent Pangea, and the formation of various sedimentary basins. Here is a comprehensive account of the geological evolution of Odisha during the Mesozoic era, with examples of specific rock formations.
1. Triassic Period (252 to 201 million years ago):
- Rifting and Sedimentation: The Triassic period in Odisha was marked by the rifting of the supercontinent Pangea, leading to the formation of sedimentary basins. The Talchir Formation, present in the Talcher Coalfield, represents Triassic sedimentary rocks consisting of sandstones, shales, and conglomerates. These rocks reflect fluvial and lacustrine environments.
2. Jurassic Period (201 to 145 million years ago):
- Continental Breakup: During the Jurassic period, the supercontinent Pangea continued to break up, leading to the opening of the Indian Ocean. This tectonic activity influenced the sedimentation patterns in Odisha.
- Karharbari Formation: The Karharbari Formation, found in the Karharbari Basin in northern Odisha, represents Jurassic sedimentary rocks. These rocks include sandstones, siltstones, shales, and limestones, indicating deposition in fluvial, lacustrine, and shallow marine environments.
3. Cretaceous Period (145 to 66 million years ago):
- Deccan Traps: During the Cretaceous period, the Deccan Traps, a large volcanic province, were formed in Odisha and other parts of India. The Deccan Traps consist of basaltic lava flows that cover extensive areas. These volcanic activities were associated with the breakup of Gondwana and contributed to the mass extinction event that marked the end of the Mesozoic era.
- Lameta Formation: The Lameta Formation, found in parts of Odisha, represents Cretaceous sedimentary rocks. These rocks include sandstones, shales, and conglomerates. Fossil discoveries in the Lameta Formation have revealed a diverse array of dinosaurs and other Mesozoic fauna.
Cenozoic Formations in Odisha
The Cenozoic era, spanning from approximately 66 million years ago to the present, is the most recent geological era. It witnessed significant tectonic events, the formation of the Himalayas, and the development of modern landscapes. Here is a comprehensive account of the geological evolution of Odisha during the Cenozoic era, with examples of specific rock formations.
1. Paleogene and Neogene Periods (66 to 2.6 million years ago):
- Baripada Beds: The Baripada Beds, found in the Mayurbhanj district of Odisha, represent sedimentary deposits of the Paleogene and Neogene periods. These beds consist of sandstones, shales, and clays, indicating deposition in shallow marine and estuarine environments. Fossils of marine organisms, including bivalves and gastropods, have been discovered in the Baripada Beds.
2. Quaternary Period (2.6 million years ago to present):
- Alluvial Deposits: During the Quaternary period, extensive alluvial deposits were formed in Odisha’s coastal plains and river valleys. These deposits consist of sands, silts, and clays transported and deposited by rivers such as the Mahanadi, Brahmani, and Baitarani. The alluvial plains provide fertile soils for agriculture and are crucial for the state’s economy.
- Laterite Formations: Laterite, a soil type rich in iron and aluminum, is widespread in Odisha and formed during the Quaternary period. It develops through the intense weathering of underlying rocks under tropical monsoon conditions. Laterite formations are found in various parts of the state, including the coastal areas and the inland plateaus.
Rocks formations of Odisha
The rock systems of Odisha represent different geological time periods and provide insights into the state’s geological history. Here are the major rock systems found in Odisha:
1. Archean Crystalline Basement Complex:
- Age: Archean Eon (4 to 2.5 billion years ago)
- Description: This is the oldest rock system in Odisha, composed of granites, gneisses, schists, and amphibolites. It formed through intense metamorphism and deformation during the early stages of Earth’s history.
2. Proterozoic Mobile Belt:
- Age: Proterozoic Eon (2.5 billion to 541 million years ago)
- Description: The Proterozoic Mobile Belt comprises sedimentary, volcanic, and intrusive igneous rocks. It includes banded iron formations (BIFs), quartzites, phyllites, shales, and volcanics. This belt formed due to tectonic collisions, sedimentation, and subsequent metamorphism.
3. Gondwana Supergroup:
- Age: Late Paleozoic to early Mesozoic era (318 to 201 million years ago)
- Description: The Gondwana Supergroup consists primarily of sedimentary rocks such as sandstones, shales, conglomerates, and coal deposits. It formed in fluvial, lacustrine, and deltaic environments during the breakup of the supercontinent Pangea.
4. Cretaceous Sediments:
- Age: Cretaceous period (145 to 66 million years ago)
- Description: Cretaceous sediments are found in parts of Odisha, particularly in the coastal areas. They comprise sandstones, shales, and limestones, representing marine and coastal depositional environments during the Cretaceous period.
5. Tertiary and Quaternary Deposits:
- Age: Cenozoic era (66 million years ago to the present)
- Description: Tertiary and Quaternary deposits include alluvium, riverine deposits, coastal sediments, and volcanic ash layers. These deposits formed through fluvial, marine, and volcanic processes, shaping the current landscape of Odisha.