208
Phaunti Village Sections
A thick sedimentary sequence of gravel fill terrace deposit comprising maximum
units is exposed at Phaunti village area (near bridge across Yamuna R. on the
way from Barkot to Purola Village) along road cutting on either banks of Yamuna
River. On the left bank, ~125 m thick sedimentary sequence consists of clast supported, moderately sorted, well imbricated, well rounded to rounded clasts (Gm)
with few sand lenses. At places the gravel is cross-stratified with lensoidal geometry
representing channel bar deposits, besides few sand lenses at bottom of the section
(Fig. 15b–d). A lower terrace surface of about 14 m from present day channel, comprising matrix supported unit of gravel embedded in a matrix (Gm2) is observed at
the same location. The unit is overlain by 5 m thick Gm facies with upwards coarsening trend (Fig. 15d). The depositional pattern suggests a channel bar deposit
under braided river condition in warm humid climate. Whereas on right bank, the
sedimentary sequences of higher terraces, which occur at 120 and 150 m, are
exposed along road cutting. The sections are measured in parts and composite log is
prepared. The lower terrace deposits (~100 m thick) consist of vertical stacking of
Gm, Fs, Sm, Sm1 and Gdm facies. The well exposed upper part of section contains
alternate beds of Gm and Sm facies (Fig. 16a, c, d). The uppermost terrace deposit
at height of ~140 m from present day Yamuna River rests over the bed rock and
consists of around 12 m thick Gm facies with highly weathered gravel. The sequence
is capped by Gm2 facies (Fig. 16d). The vertical accretion of Gm, Fs, Sm, Sm1
facies assemblage indicates channel bar deposition and the presence of occasional
beds of sand suggests varying energy conditions. Patch of Fs facies with erosional
contact with Gm facies (at middle of section) indicates post depositional dissection
of terrace deposit.
Lakhamandal Section
Around 40 Km downstream of Barkot, at Lakhamandal, terrace staircase ranging in
height from 220 m to 5 m is well preserved on the right bank of the Yamuna River.
The terraces occurring at levels of 5–10 m, 60 m, 120–125 m and around 240 m
height from present day Yamuna River bed, expose multiple sedimentary sequences
(Fig. 17). The topmost terrace, at the height of around 220 m to 130 m, exposes
9–10 m thick sedimentary sequence with alternate stacking of Gm and Gdm
(Figs. 17 and 18b). The next level of terrace commences at around the height of
125 m with exposed sedimentary sequence of ~60 m and comprises stack of 6 m of
Gm facies intercalated with Sm facies at base (Fig. 17). These units are overlain by
thick beds of Gm and Gdm facies. The subsequent level of terrace in the descending
order exposes ~6 m thick sedimentary sequence characterized by alternate Gm,
Gdm, Sm and St facies upto ~326 m from the river bed and is overlain by around
26 m thick alternate beds of Gm, Sm and Gm, Gdm facies association (Fig. 17). The
top ~7 m is not well exposed (Figs. 17 and 18a, c). The Yamuna River deposit in the
section is characteristically dominant by quartzite and granite gneiss clasts showing
S. Dutta et al.
Phaunti Village Sections
A thick sedimentary sequence of gravel fill terrace deposit comprising maximum
units is exposed at Phaunti village area (near bridge across Yamuna R. on the
way from Barkot to Purola Village) along road cutting on either banks of Yamuna
River. On the left bank, ~125 m thick sedimentary sequence consists of clast supported, moderately sorted, well imbricated, well rounded to rounded clasts (Gm)
with few sand lenses. At places the gravel is cross-stratified with lensoidal geometry
representing channel bar deposits, besides few sand lenses at bottom of the section
(Fig. 15b–d). A lower terrace surface of about 14 m from present day channel, comprising matrix supported unit of gravel embedded in a matrix (Gm2) is observed at
the same location. The unit is overlain by 5 m thick Gm facies with upwards coarsening trend (Fig. 15d). The depositional pattern suggests a channel bar deposit
under braided river condition in warm humid climate. Whereas on right bank, the
sedimentary sequences of higher terraces, which occur at 120 and 150 m, are
exposed along road cutting. The sections are measured in parts and composite log is
prepared. The lower terrace deposits (~100 m thick) consist of vertical stacking of
Gm, Fs, Sm, Sm1 and Gdm facies. The well exposed upper part of section contains
alternate beds of Gm and Sm facies (Fig. 16a, c, d). The uppermost terrace deposit
at height of ~140 m from present day Yamuna River rests over the bed rock and
consists of around 12 m thick Gm facies with highly weathered gravel. The sequence
is capped by Gm2 facies (Fig. 16d). The vertical accretion of Gm, Fs, Sm, Sm1
facies assemblage indicates channel bar deposition and the presence of occasional
beds of sand suggests varying energy conditions. Patch of Fs facies with erosional
contact with Gm facies (at middle of section) indicates post depositional dissection
of terrace deposit.
Lakhamandal Section
Around 40 Km downstream of Barkot, at Lakhamandal, terrace staircase ranging in
height from 220 m to 5 m is well preserved on the right bank of the Yamuna River.
The terraces occurring at levels of 5–10 m, 60 m, 120–125 m and around 240 m
height from present day Yamuna River bed, expose multiple sedimentary sequences
(Fig. 17). The topmost terrace, at the height of around 220 m to 130 m, exposes
9–10 m thick sedimentary sequence with alternate stacking of Gm and Gdm
(Figs. 17 and 18b). The next level of terrace commences at around the height of
125 m with exposed sedimentary sequence of ~60 m and comprises stack of 6 m of
Gm facies intercalated with Sm facies at base (Fig. 17). These units are overlain by
thick beds of Gm and Gdm facies. The subsequent level of terrace in the descending
order exposes ~6 m thick sedimentary sequence characterized by alternate Gm,
Gdm, Sm and St facies upto ~326 m from the river bed and is overlain by around
26 m thick alternate beds of Gm, Sm and Gm, Gdm facies association (Fig. 17). The
top ~7 m is not well exposed (Figs. 17 and 18a, c). The Yamuna River deposit in the
section is characteristically dominant by quartzite and granite gneiss clasts showing
S. Dutta et al.