Tectonic framework of india

Wednesday, 19 February 2025 9:44 AM

The Indian subcontinent can be divided into three major geological regions: the
Peninsular India, the Extra-Peninsular region, and the Indo-Gangetic Plain. Each
of these regions has distinct geological characteristics and formations.
Peninsular India
The Peninsular India is one of the oldest and most stable landmasses in the
world. It is composed of ancient Precambrian rocks, primarily from the Archean
era, and includes complex formations such as the Dharwar, Cuddapah, and
Gondwana systems.
Key geological features of Peninsular India include:
• Tectonically stable region with lower earthquake risk
• Complex mix of Archean, Gondwana, Cuddapah, and Dharwar
rock formations
• Presence of ancient mountain ranges like the Aravalli Range
• Rich mineral deposits, including coal and iron ore
• Deccan Traps, a vast plateau formed by volcanic activity during
the late Cretaceous period
Extra-Peninsular Region
The Extra-Peninsular region primarily refers to the Himalayan mountain range
and its associated features. This region is geologically younger and more active
than the Peninsular India.
Key geological characteristics include:
• Formed by the collision of the Indian and Eurasian tectonic plates
• Composed of folded and faulted sedimentary rocks
• Tectonically active, with frequent earthquakes and ongoing
mountain-building processes
• Rich in metamorphic rocks due to intense pressure and
temperature conditions
Indo-Gangetic Plain
The Indo-Gangetic Plain is a vast alluvial plain that lies between the Peninsular
India and the Extra-Peninsular region. It is one of the world’s largest and most
fertile alluvial plains.
Key geological features of the Indo-Gangetic Plain include:
• Formed by sediment deposition from the Indus, Ganges, and
Brahmaputra river systems
• Composed of the world’s largest expanse of uninterrupted
alluvium
• Divided into distinct regions: Bhabar, Terai, Bangar, and Khadir,
each with unique geological characteristics
• Relatively young geological formation compared to Peninsular
India
• Highly fertile due to continuous deposition of alluvial soil
The geological diversity of these three regions has significantly influenced
India’s topography, mineral resources, and agricultural potential, shaping the
country’s economic and cultural landscape over millennia.

The geology of the Indian subcontinent is highly diverse, with three broad
provinces that record very different tectonic histories. In broad terms:

1. Peninsular Region

This region forms the ancient, stable core of India and is often called the Indian
Shield. Its key features include:
• Ancient Cratonic Basement:
The peninsular region is dominated by Precambrian rocks—some of the oldest
on Earth—formed during the Archaean and Proterozoic eons. Major cratonic
blocks (e.g., the Dharwar, Bundelkhand, Singhbhum, Aravalli, and Bastar
cratons) contain extensive exposures of gneisses, schists, and granites. These
rocks record a long history of high-grade metamorphism and magmatic activity
that shaped a stable continental nucleus.

• Sedimentary Basins and Mobile Belts:

Overlying these ancient rocks are sedimentary basins such as the Vindhyan and
Cuddapah systems. These basins preserve records of later sedimentation and
minor tectonic reactivations that occurred during the Proterozoic and even into
the Phanerozoic. Additionally, mobile belts like the Eastern Ghats (which border
the shield) represent reworked fragments of this ancient crust.
• Volcanic Episodes:
A dramatic later event in peninsular geology is the eruption of the Deccan Traps
at the end of the Cretaceous period. These extensive basaltic lava flows (up to
several kilometers thick) not only blanketed large parts of the region but also
have had significant implications for the global climate and mass extinctions.

2. Extrapeninsular Region

Often contrasted with the stable shield is the extrapeninsular part of India,
which mainly includes the Himalayan orogen and its associated foreland
structures. Its geological characteristics are:
• Orogenic Dynamics and Plate Collision:
This region is the result of the relatively recent (in geological terms) collision
between the Indian Plate and the Eurasian Plate. The ongoing convergence has
produced the Himalayan mountain belt—a highly tectonically active zone
characterized by complex folding, thrust faulting, and high-grade
metamorphism. The extrapeninsular area can be subdivided into distinct zones
such as the Sub-Himalayan (Siwalik) sequence, the Lesser Himalayas, and the
Greater Himalayan crystalline complex. These units record progressive
deformation, metamorphism, and crustal thickening as India pushed into
Eurasia.

• Active Tectonics and Erosion:

The high relief and rapid uplift of the Himalayas have led to intense erosion.
This not only fuels the dynamics of the orogen but also provides a continuous
supply of sediments to adjacent basins.

3. Indo-Gangetic Plain

Lying at the foot of the Himalayas, the Indo-Gangetic Plain is a vast alluvial basin
formed by the erosion of the uplifted mountains. Its key geological aspects
include:
• Foreland Basin Development:
As the Himalayas rose, heavy erosion by monsoon-fed rivers (such as the Ganga,
Indus, and Brahmaputra and their tributaries) created an enormous deposit of
unconsolidated sediments. This process formed one of the world’s largest and
thickest alluvial plains.

• Sedimentary Record:
The plain’s sediments record the erosional history of the Himalayas. Layers of
silt, clay, sand, and gravel have been progressively deposited in a foreland basin
setting. The depositional history reflects variations in climate, tectonic uplift,
and river dynamics.
• Economic and Environmental Significance:
The fertile soils of the Indo-Gangetic Plain have underpinned agricultural
development for millennia. At the same time, its unconsolidated nature makes
it highly susceptible to flooding and, in some areas, seismic amplification.

Synthesis

In summary, while the peninsular region represents a stable, ancient shield

characterized by Precambrian crystalline rocks and subsequent volcanic events
(e.g., the Deccan Traps), the extrapeninsular region is a dynamic, tectonically
active zone shaped by the collision of India with Eurasia, giving rise to the
Himalayas and their associated thrust belts and metamorphic complexes. The
Indo-Gangetic Plain then forms a vast, sediment-filled foreland basin at the foot
of these rising mountains, continuously recharged by the erosion of the
extrapeninsular highlands.

Together, these three provinces not only illustrate a dramatic progression in the
tectonic evolution of the subcontinent but also explain much of its present-day
landscape, natural resources, and geohazards.