Download Morphotectonics of the Chambal and the Yamuna Valleys in the

Geological Survey of India MORPHOTECTONICS OF THE CHAMBAL AND THE YAMUNA VALLEYS IN THE
WESTERN MARGINAL GANGETIC ALLUVIAL PLAINS
INTRODUCTION
The Marginal Gangetic Alluvial Plain (MGAP) constitutes the southern part of the Ganga Plain
active foreland basin, formed due to flexing of the Indian lithosphere brought about by thrust fold loading
of the Himalayan Orogen. It forms a NNW – SSE to E – W trending alluvial tract that extends from the
Great Boundary Thrust (GBT) in the west to the Rajmahal Hills in the east. The northern limit of the
MGAP is formed by the axial rivers of the Ganga Plain, i.e., the Yamuna in the west and the Ganga in the
east, while its southern margin is defined by the hard rock terrain of Indian peninsula.
The western part of the MGAP is drained by the Yamuna and its right bank tributaries, which
include the Chambal, the Gambhir, the Sind, the Pahuj, the Betwa, and the Ken. This region is
characterized by its distinct fluvial landforms, deeply incised drainage system, and morphotectonic
features. It is also notorious for its spectacular badlands having a labyrinthine network of deeply incised
gullies and ravines which reach up to a depth of 50-60 m along the rivers. Though the Chambal is
regarded as a tributary of the Yamuna, its discharge capacity, degree of incision, and channel width and
depth is significantly more than that of the Yamuna. Hence, the Chambal constitutes the trunk stream of
the region. Also, the river course downstream of the Chambal – Yamuna confluence, which is at present
known as the Yamuna entirely due to mythological and historical reasons, has the same channel geometry
and gradient as that of the Chambal River upstream of the confluence. This suggests that the Yamuna, in
reality, follows the course of the Chambal River below the confluence of the two rivers.
METHODS AND MATERIALS
The present work is based on the data generated by the authors during three seasons of geoenvironmental studies and geological and geomorphologic mapping (1:50,000) of extensive areas of the
western MGAP. Field studies were supplemented by interpretation of aerial photographs, IRS imagery,
and Survey of India toposheets of 1922, 1956, and 1977 editions. For morphotectonic studies, ultra highresolution imagery data from Google Earth, 90-m SRTM elevation data, and spot heights from Survey of
India maps were used to create 3-D terrain models and digital topographic sections on Arc GIS platform.
GEOLOGIC SET-UP
The western MGAP is underlain by Quaternary alluvium deposited by the present as well as the
ancestral river systems of the Peninsular rivers debouching the Ganga Basin. The basement for the
alluvium is formed by the Bundelkhand Granite, the Gwalior Group, and the Vindhyan Supergroup. The
Precambrian rocks occur at shallow depth (50 to 60 m) towards the west in Morena and Dhaulpur areas,
with the sporadic outcrops protruding out of the alluvial cover. Towards the east and the north, the
thickness of the alluvium attains 145 m at Bhind and 190 m at Barhi at the bank of the Chambal River.
Deep incision by the Chambal and its tributaries has exposed up to 55 m of the alluvial sequence for
study.
1 Contributed by M N Mishra and L L Vishwakarma
Central Region
Geological Survey of India The Older Alluvium:
The Older Alluvium comprises a highly oxidized polycyclic sequence of fine sands, silt, and clay
in varying proportions. Coarse channel sand and grit bodies also occur at places. Numerous kankar and
hardpan horizons are characteristically present in it. The lower part of the alluvial sequence consists of a 5
to 7 m thick conglomerate unit containing pebbles derived from the peninsular source. This unit has also
yielded profuse vertebrate fauna of Upper Siwalik age. The Older Alluvium constitutes a vast regional
tableland forming a major planation surface.
The Newer Alluvium:
The Newer Alluvium comprises the channel and the overbank floodplain deposits of the present
rivers. Due to prominent incision of the rivers within the Older Alluvium and presence of high banks, the
Newer Alluvium is restricted along the river channel and some distance away from it along the meanders
of the rivers, just below the erosional terraces that occur at a higher elevation.
GEOMORPHOLOGY
The alluvial tract exhibits a remarkable homogeneous topography with the only relief perceptible
to the eye being formed by the river bluffs and the belt of ravines along the river courses. It has been
sculptured by the rivers in a stepped sequence, forming distinct erosional and depositional surfaces,
separated from one another by steep scarps.
T2-surface:
It is the regional planation surface which is developed on the Older Alluvium. It occupies the
highest elevation and forms an extensively flat tableland. The present drainage network is superimposed
on this oldest morphostratigraphic surface with considerable incision (Fig. 1, 2, & 3). The surface exhibits
extensive development of badlands along the rivers and streams of this region. The elevation of this
surface is 178 m above MSL in the west and falls to 145 m towards the east over a distance of nearly 100
km. The elevation of the T2-surface over the river bed of the Chambal is as much as 55 to 60 m.
T1-surface:
The T1-surface forms the erosional terrace of the rivers and is deeply incised on the T2-surface,
the elevation difference between the two surfaces being as much as 25 m. Along some sections of the
rivers, the T1-surface shows more than one levels, with low, steep scarps separating them. This surface is
normally not inundated during the seasonal floods and its development is not uniform and continuous
along the river courses. The T1-surface has resulted due to lateral migration of the river channel within the
older alluvium after an initial period of entrenchment and the consequent removal of the latter from the
areas swept across by the river channel.
The rivers of the area exhibit a number of incised cut-off meanders at nearly the same elevation
as that of the T1-surface. This indicates that while the rivers in some sections had freedom to shift
laterally and to carve out the T1-surface by lateral erosion, elsewhere, the courses of the rivers were fixed
with the consequent growth of entrenched meanders. With further lowering of the base level due to
rejuvenation, the rivers abandoned the T1-surface and the cut-off meanders also formed simultaneously.
2 Contributed by M N Mishra and L L Vishwakarma
Central Region
Geological Survey of India The arms of the entrenched meanders invariable enclose the remnants of the T2-surface, now showing
badland topography.
T0-surface:
This is a depositional surface and represents the recent floodplains of the present rivers. It
includes mainly the channel and to a lesser extent, the overbank flood basin geomorphic features and
landforms, e.g., point bars, channel bars, meander scrolls, natural levees etc. On account of deep incision
of the T0-surface on T1-surface and degradational nature of the rivers, the overbank floodplains are
confined along river meanders, just below the T1-erosional terrace with a steep break in slope.
The Badlands:
Badland topography, showing an intricate network of gullies and ravines, stretches for hundreds
of kilometers along all the rivers and streams and may attain a width of as much as 12 km across them
(Fig. 1). Though badlands are mainly developed on T2-surface, the T1-surface also shows the development
of ravines in some sections. The badland tract displays an extensively dissected landscape having high
drainage density; dendritic, trellis, and rectangular drainage patterns; deep gullying; steep to sub-vertical
scarps with narrow interfluves, and steep banks rising to a height of 50 m (Fig. 6, 7, 8, 9). The depth of
the ravines varies from 10 m in the upper reaches to 50 m adjacent to the Chambal River. Downstream of
Etawah, the badlands of the Yamuna, Chambal, Kunwari, Sind, and Pahuj Rivers have become so wide
that the interfluves between the rivers have almost totally been destroyed by the headward erosion of the
gullies.
MORPHOTECTONICS
Regional tectonic setting of the western MGAP:
The Ganga Plain, an active foreland basin, has come into existence by the flexing of the Indian
lithosphere in response to continent – continent collision and thrust fold loading of the Himalayan
mountain chain. The Himalayan orogeny is responsible for the development of a prominent bulge in the
flexed Indian lithosphere in central India, which encompasses the Satpura – Malwa – Bundelkhand region
from the south to the north. The western MGAP is situated on the northern slopes of this bulge.
Continuing northward journey and concomitant deformation of the Indian plate has caused accumulation
of stresses in the Indian plate. The northern part of the bulge displays features characteristic of a tensional
tectonic regime. Deeply incised nature of the drainage, presence of entrenched cut-off meanders hanging
over the modern river channels, large difference of elevation between the T0-, T1-, and T2- geomorphic
surfaces, degradational nature of the rivers, warping of the regional planation surface, and active gully
erosion are suggestive of uplift of the MGAP during the Late Quaternary.
Basement lineaments and their control on drainage:
The western part of the MGAP is traversed by ENE – WSW, NW – SE, NNW – SSE, and NE –
SW trending lineaments, mainly represented by basement fractures and faults traversing the Precambrian
rocks (Fig. 4). The upper reaches of the Chambal, Sind, Betwa, and Ken rivers are controlled by NE – SW
trending set of lineaments. The abrupt easterly and south-easterly bends in their lower reaches, prior to
3 Contributed by M N Mishra and L L Vishwakarma
Central Region
Geological Survey of India their confluence with the Yamuna, is due to the combined influence of the NW – SE, NNW – SSE, and
ENE – WSW trending sets of lineaments. Because of the lineaments, free meanders are virtually absent
along the rivers and the channels follow zig-zag courses having sharp kinks and abrupt bends along the
main lineament trends of the region. The ephemeral gullies too depict strong controls of lineaments and
bed rock joints with trellis, rectangular, and parallel drainage patterns being ubiquitous in the badland
tract.
Seismogenic nature of basement lineaments:
Some of the basement lineaments have not only affected the overlying Gwalior and Vindhyan
strata but have also left their imprints in the Quaternary alluvial tract. This suggests that reactivation of
these ancient basement fractures, with accompanying tectonic adjustments, have been a feature
throughout the geological history of the area. The Bhind earthquake of 1994 has been attributed to the
dextral transcurrent movement along a NNW – SSE trending lineament passing between Pinahat (Fig. 4)
and Tikatpura. Abrupt and conspicuous shift in the course of Chambal and Gambhir rivers at Pinahat and
Tikatpura respectively along this lineament, a high order of meandering in the Yamuna where this
lineament crosses the river, a faster rate of headward erosion along gullies following this lineament, and
tilting of Older Alluvium near Pinahat at the right bank of the Chambal provide manifestations of
neotectonic deformation along this lineament. The Kunwari River also shows abrupt change in shift along
this lineament.
Presence of nick-points and block movement across lineaments:
The Chambal river bed shows segmental variations, ranging from 27 cm / km to 9 cm / km, in its
gradient. The longitudinal profile of the Chambal River (Fig. 5) exhibits the presence of several knickpoints over a distance of 160 km in the study area. The most conspicuous nick-point is observed across
the Pinahat – Tikatpura lineament where the river bed falls from 112 m to 106 m over a channel length of
14 km, corresponding to a rather steep gradient of 43 cm / km. Topographic section across the Pinahat –
Tikatpura lineament also depicts steepening of the easterly slope of the T2-surface in an abrupt manner.
The thickness of the alluvium also increases from a few tens of meters to the west of this lineament to
around 200 m to the east. This indicates that this lineament is a morphotectonic fault. All these
observations suggest the possibility of differential uplift of blocks bound by lineaments represented by
basement fractures. Deeply incised nature of the thalweg in the point bar deposits, some of which show
break in slope or even the presence of two levels, and sectorial development of floodplains along the river
course further corroborate possibility of differential block movements.
Evidences of neotectonics from the Palaeochannel of Dhaulpur area:
Between Basai Dang and Garhi Jafar in Dhaulpur area, a 74 km long palaeochannel (Fig. 1, 4),
which once served as the left bank tributary of the Chambal is observed on the T2-surface. Following a
course sub-parallel to the Chambal, it meanders its way across the regional tableland before meeting the
former at Garhi Jafar. The advancing ravines at the left bank of the Chambal have consumed a large part
of the palaeochannel at several places. Relative recency of abandonment of this channel is attested by
well defined palaeo-banks and bluffs along the abandoned valley and well preserved meanders. The
paleochannel also contains large villages on its either banks though archeological study is required to
establish the period of earliest settlements.
Contributed by M N Mishra and L L Vishwakarma
4 Central Region
Geological Survey of India The present drainage network on the T2-surface of the MGAP exhibits prominent entrenchment,
gullying, controls of the basement fractures and development of erosional terraces. In sharp contrast the
palaeochannel is devoid of such features and displays in its lower reaches, meanders of high amplitude – a
characteristics typical of a sluggish stream meandering its way across a surface having very low gradients.
These observations indicate that the palaeochannel predates the event of incision, terracing, and gullying
and that by the time the rivers of the region engaged themselves in such activities, it had already gone dry
and become inactive. Also the difference in elevation between the Chambal River and the paleochannel is
about 55 m. Such an enormous difference in elevation between a major river and its tributary in an
alluvial tract having very low gradient is difficult to explain unless the role of neotectonics is called for.
Warping of the alluvial tract:
The micro-relief and the gentle slopes on the T2-surface are imperceptible to the eye. However,
contouring of this surface on 2-m interval, utilizing about 800 spot heights on the Survey of India
topographical sheets, reveals the presence of synformal downwarps and antiformal / domal upwarps (Fig.
1, 2,3) in the alluvial tract along NE – SW and ENE – WSW trending axes. The courses of the rivers of
the area are seen to coincide with these upwarps and downwarps. The Yamuna, the Gambhir, and the
Kunwari rivers follow the downwarps while the Chambal for the most part of its course follows the
antiformal axis and thus occupies the topographic high of the area. As a result, the T2-surface slopes away
from the river along both its banks rather than towards it. The upwarps and the downwarps have also
influenced the width of the ravinous tract and that of the catchment area of the rivers of the region. As the
Chambal follows the antifromal upwarp, its catchment is relatively narrow (4 to 12 km across the banks)
and is solely represented by the width of the ravinous tract with no major streams meeting it along either
bank. In contrast the Yamuna, Gambhir and Kunwari which flow along the downwarps have wider
catchments and receive large streams draining the T2-surface. As a consequence the width of the ravinous
tract along these rivers is also more than that along the Chambal though the gullies are understandably
deeper along the latter on account of its greater degree of incision.
Geomorphic evidences suggest that the warping of the alluvial tract took place long after the
superimposition of the major rivers of the area on T2-surface and it must have been responsible for the
demise of the palaeochannel of Dhaulpur area. The warping has resulted either due to folding / warping of
the basement rocks or due to block uplift of a part of the basement along lineaments. Rampant gully
erosion along the banks of the present rivers, warping of the alluvial tract, and characteristics of the
paleochannel described above furnish convincing evidence of neotectonic activity in the region.
Incised cut-off meanders:
Entrenched meanders are commonly cut-off at their narrow necks through normal erosional
processes, yet some of the cut-off meanders of the Chambal are not very tight and the separation between
the two arms may be as much as 5 km. Such cut-off meanders have come into existence solely due to
tectonic movements along lineaments passing through the neck of the meanders rather than normal
erosional processes or change in the hydrology of the river channel.
5 Contributed by M N Mishra and L L Vishwakarma
Central Region
Geological Survey of India MORPHOTECTONIC EVOLUTION AND REGIONAL IMPLICATIONS
The rivers of the western MGAP display significant vertical incision with little lateral migration
restricted along some sections. Even the Yamuna, a river of highly meandering nature in the northern part
of the study area, shows almost no lateral migration though numerous deeply entrenched meanders are
seen along its course. The entire drainage network bears evidence of rejuvenation on a regional scale.
Such features are indicative of a large sudden and rapid lowering of base level.
Study of the cross valley profile suggests that in an earlier stage of their evolution they were of
more meandering nature than at present. The plaeochannel of Dhaulpur area was a left bank tributary of
the Chambal and the two rivers following a mature course and having almost the same bed level flowed
on the T2-surface without any significant entrenchment. A sudden rejuvenation in relief due to block
uplift of the region in response to Himalayan tectonics, caused the rivers of the area to experience a phase
rapid incision in the soft and unconsolidated Older Alluvium. The tectonic movement also caused
epeirogenic warping of the alluvial tract and as the bed level of the Chambal rose up due to the formation
of an upwarp along its course, the river was displaced from its state of metastable hydrologic equilibrium.
This resulted in a faster rate of erosion and degradation of the river bed and also accentuated the
hydrologic gradient in the tributary streams, i.e., the Yamuna, Ken, Betwa, Gambhir, Kunwari, Sind etc.
Continued arching of the T2-surface along the Chambal caused a reversal of slope (Fig. 1, 2) and resulted
in the disruption of the palaeochannel before it could incise itself. Accelerated erosion along the rivers to
attend the local base level of the Chambal - the trunk history in this part, lead to prominent incision of the
drainage and initiated the formation of badland topography. The rapidly marching heads of the expanding
gullies also consumed parts of the palaeochannel.
After the initial cycle of the rapid uplift and the resultant incision of the drainage, the rate of
vertical degradation experienced a relative decline. The rivers engaged themselves to lateral erosion in
some sections with the formation of the T1-surface in their narrow incised valleys. Another cycle of
rejuvenation caused the abandonment of the T1-surface and the formation of cut-off meanders. This cycle
comprised several short pulses of tectonic uplift which gave rise to a flight of erosional surfaces of limited
aerial extent just below the T1-surface. As the degree of incision increased due to the cycles of
rejuvenation, the basement lineaments established their control in the alignments of the river channels.
It is an established fact that tectonic movements and continued uplift of the Aravalli Mountain
belt during the Holocene and as late as the historic period have brought drastic changes in the drainage
network of northwest India. Geo-archaeological evidences suggest that during the pre-historic and the
historic period, the Yamuna, following a southwesterly course, shared its waters with the mighty
Saraswati on the fecund banks of which the Vedic civilization (~5000 years BP). K S Valdiya opines
that, a minor tributary of the Chambal (the present Yamuna), through rapid headward erosion, robbed the
waters of the then southwesterly flowing Yamuna, causing the decline of the Vedic Civilization. From the
present study it may be suggested that tectonic movements leading to the warping of the alluvial tract,
derangement of the palaeochannel, incision of the rivers, and the onset of severe gully erosion in the study
area had a close link with the uplift of the Aravallis during the pre-historic and the historic period. It
appears that the incision of the Chambal due to neotectonic movements might have been instrumental in
bringing about rapid headward erosion in the tributary stream which subsequently beheaded the then
southwesterly flowing Yamuna.
6 Contributed by M N Mishra and L L Vishwakarma
Central Region
Geological Survey of India Recent dating of the Quaternary alluvium by I B Singh and others suggests two distinct episodes
of intense neotectonic activity in the southern part of the Ganga Plains during the Middle and the Late
Holocene around 9 Ka BP and 5 Ka BP. Historical evidence from the western MGAP suggests that the
development of a major part of the badlands has indeed taken place during the historic past. The
entrenched cut-off meanders, hanging well above the present rivers, contain innumerable villages, old
castles, and temples right on the banks within the ravines. Legend has it that these settlements were once
situated on the banks of the rivers. Ruins of former settlements, broken potteries, and temples with their
foundations almost entirely eroded away by the encroaching ravines (Fig. 10) and idols of Buddha and of
Hindu deities dot the ravine landscape. Near Ater, an eleventh century, as shown on an ASI plaque, Durga
temple is seen entangled amidst the labyrinth of ravines. These observations suggest that the areas
presently inaccessible due to ravine formation, were inhabited by the people during the historic period.
Excavations by the ASI reveal that the ravinous area was occupied by people even during the
Mahabharata period (published leaflets of the ASI). Analyzing the historical evidence, R L Singh
concludes that most of the erosion and ravine formation has occurred during the last 400 years. Also,
during the Mediaeval period, Dhaulpur town was situated near the Chambal where its old site is occupied
by a dilapidated fort. Later on due to onslaught of the ravines the entire town was shifted about 4 km
towards the north.
CONCLUSIONS
The present study corroborates that the western part of the MGAP has witnessed two distinct
episodes of neotectonism mainly in the form of epeirogenic uplift causing regional stream rejuvenation
and prominent incision of the drainage. The basement lineaments provide an active tectonic regime in
which accumulation of stress and differential block movements have been taking place intermittently. The
causative factor for the neotectonic activity appears to be the growth and the uplift of the peripheral bulge
in the northern part of the Peninsula in response to the Himalayan Orogeny. As a considerable part of the
ravinous tract has come into existence well within the historic period, it is suggested that the tectonic
movements responsible for the topographic rejuvenation of the western MGAP must have taken place
during the past few millennia in the Late Holocene. The rapid advance of the badlands at present is the
manifestation of the continuing neotectonic activity.
7 Contributed by M N Mishra and L L Vishwakarma
Central Region
Geological Survey of India Fig. 1: Geomorphic map of a part of MGAP showing T0, T1 & T2 – surfaces and belts of ravines. Note
upwarps and downwarps in the alluvium. Contour values are in meter. Palaeochannel is shown in red.
Fig. 2: Diagrammatic representation of the deeply incised nature of the drainage and the presence
of upwarps and downwarps in the alluvial terrain. The arrows indicate the direction of slope of
the T2-surface. Note that the meanders of the palaeochannel are up the gradient.
8 Contributed by M N Mishra and L L Vishwakarma
Central Region
Geological Survey of India Fig. 3: Digital 3-D model of the geomorphic surfaces showing deep incision of rivers
Fig. 4: Lineament fabric of the western MGAP. Paleochannel between Basai Dang and Garhi Jafar shown
in white in the western part
9 Contributed by M N Mishra and L L Vishwakarma
Central Region
Geological Survey of India Fig. 5: Longitudinal profile of the Chambal River. Note prominent nick-point near Pinahat.
Fig. 6: Amphitheatre-headed ravines along the Chambal River. The height of the escarpment is 12 m.
10 Contributed by M N Mishra and L L Vishwakarma
Central Region
Geological Survey of India Fig. 7: Rill erosion in clay-rich alluvium
Fig. 8: Vast expanse of ravines along the Chambal
11 Contributed by M N Mishra and L L Vishwakarma
Central Region
Geological Survey of India Fig. 9: Thick layers of sand (light tone), silt (medium tone), and clay (dark tone) in ravine section
Fig. 10: Almost complete erosion of foundation of a 6th century temple due to the onslaught of ravines
12 Contributed by M N Mishra and L L Vishwakarma
Central Region