field trip to nainital
DESCRIPTION
FIIELD REPORT FOR TRIIP TOOUTER LESSER HIMALAYA,NAINITAL – BHIMTAL-AMRITPUR AREA,KUMAUN HIMALAYA, UTTARAKHANDTRANSCRIPT
FFIIEELLDD RREEPPOORRTT FFOORR TTRRIIPP TTOO OUTER LESSER HIMALAYA,
NAINITAL – BHIMTAL-AMRITPUR AREA, KUMAUN HIMALAYA, UTTARAKHAND
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Acknowledgement
I would like to acknowledge and express my gratitude to Dr. Aashima
Sakia and Mr. R.P.Singh for guiding us throughout the trip .Special
mention must be given to teachers at Kumaun University who took out
time from their schedule and gave us a firsthand knowledge of geology of
areas,in and around Nainital .
I am grateful to my entire team members and classmates for their kind
co-operation and help in the field.
COMMON TERMINOLOGIES USED IN THE FIELD
STRIKE: - The direction of a line formed by the intersection of bedding
and a horizontal plane.
DIP: - It is the angle that it makes with a horizontal plane in a direction
perpendicular to the strike of the plane.
FAULT: - It is the plane along which the relative displacement of beds is
taking place.
JOINT: - Joints are opening or cracks in the rocks that join the simplest
fracture structure without involving displacement of the surface.
CLEAVAGE: - It is the formation of a set of fractures along closely
spaced, parallel surface in a rock by the alignment of various
mineralogical and structural elements during metamorphism and
deformation.
RIPPLE MARKS: - is another common sedimentary structure which is
frequently used to determine facing. Ripple marks may form on the
bottom of the water or by wind action at the surface of the Earth.
SYN-FORM: A fold that closes downward.
ANTI-FORM: A fold that closes upward.
CROSS BEDDING: - Cross bedding is a type of stratification in which
some sediment layers have an inclined attitude in relation to those
immediately above or below.
SLICKENSIDE:A lineation on a fault or bedding plane caused by the
frictional movement of rock body against another. The plane may be
coated by mineral often Quartz or Calcite, which itself shows striations in
the direction of movement.
Field Equipments & Procedures
BRUNTON COMPASS: - Designed by Canadian scientist/geologist
D.W. Brunton, it is used for field mapping of geological objects by
Geologists. It provides a precise sighting clinometers and hand level
capacity.
HAMMER: - A heavy hard steel geological hammer with one side blunt,
to crush and hence break the rock along fractures and partings. It should
preferable have a rubber grip.
HAND LENS:- A hard lens is used to magnify the textural feature of the
rock sample when held closely between the eye and the sample towards
the sources of light.
SATCHEL: - A cloth bag for carrying rock samples and field equipments,
with special pockets provided.
FIELD DIARY: - It is used to note down the data and observation,
including sketches observed or collected from the field.
MEASURING STRIKE:-Place the bottom edge of the brunton compass at
against the plane of intersect.Adjust the compass orientation, making
sure the bottom edge is always flat against the plane, until the air bubble
in the Bull is Eye level’ is centered.Read either end of the compass
needle to obtain the value of strike.
MEASURING DIP:-
After determining the strike, we rotate the compass 90.Place the side of
the compass flat against the plane.Adjust lever on the back of the
compass until the air bubble in the ‘clinometers level’ is centered.Read
the dip directly from the scale in the compass.
REGIONAL GEOLOGICAL SETTING
The Nainital hills represent the southeastern part of a strip of enechelon
basins of the Krol belt, which stretches southeastward from Solan
(Himachal) to Nainital (Uttarakhand).The southern limit of the Krol belt is
delineated by the highly tectonized rocks of the Amritpur granites which
have been brought up along Main Boundary Thrust (MBT).
The sedimentary succession of Krol belt in Nainital area begins with the Nagthat Formation of the Jaunsar Group, which is sharply overlain by the Blaini Formation, which in turn gives way to Krol and Tal formations. These outer Lesser Himalayan rocks are sandwiched between the Main Boundary Thrust (MBT) in the south, which separates them from the Neogene Siwalik and Ramgarh thrust in the north marking a faulted contact with crystallines rocks of the Almora Nappe. The rocks aredipping north to northeast at angles ranging 10° to 60°.
The Almora hills represent the central sector of the Almora Nappe,
stretching west from Dandeldhura (western Nepal) to Dudhatoli in
Garhwal, Geologists have recognized the Almora Nappe a thick pile of
metasedimentaries and granites, representing central crystallines
designated as Saryu Formation,Gwalikhet Formation and Champawat
granitoid as the Almora Group, and the lower Nathuwakhan Formation
and Ramgarh (Devguru) Porphyry as Ramgarh Group.
NAINITAL:
The lake district of the mountains,Nainital town was first discovered by an
English traveller P. Barren in 1842. The town witnessed a devastating
landslide in September 1880, which also created today’s playground, or
Flats on the northwestern corner of the lake. Set over 2000m above the
sea, the headquarter of Nainital rises around its large lake. Being a
touristic place, it is highly crowed during summer months of April to June.
DAY ONE(17.12.11)
LOCATION: Durham House near Sherwood College OBJECTIVES: To observe the rocks of the Upper Krol and their Biohermal structures. A thick succession of light to dark-grey dolomite of upper Krol succession characterizing development of 1000 to 900 m.y. old biohermal structures is well exposed at this site. The important bioherm (stromatolites) present in this rock unit are columnar, laminar, domal, oncoidal, plumose and irregular stromatolites. The bioherms are namely Baicalia baicalica, Kursinella, Minjaria, Colonella Columnaris . These bioherms suggest a shallow marine depositional environment in middle to late Proterozoic age.
1000 to 900 m.y. old biohermal structures (stromatolites) built by algae-bacteria are exposed in Sherwood College section
Elephant skin texture dolomite
Highly weathered
Taking out dip strike at durham
house.
2119m
N29.22.54
E79.27.24
Strike=N50E
Dip=56SE
Some shales & slate also seen
DAY TWO(18.12.11) LOCATION : Naina Devi OBJECTIVES: To observe the rocks of the Upper Krol
LOCATION: Bada patthar,Tiffin Top, OBJECTIVES: To observe phyllites
Intensely folded slates & shales
and some phyllites.
1936m
N29.23.16
E79.27.18
Strike=N62W
Dip=52NW
Striated rocks due to tectonic
activity
LOCATION :Lands End OBJECTIVE: To observe the rocks of Upper Krol - Tal succession, and P-c Boundary The lower part of the sequence characterizes interbeds of pyretic, carbonaceous shales and dolomite; however the upper part has grey and purple shales with local, isolated beds of fine to medium-grained sandstone. In the upper levels (Gairkhet Member), the Tal Formation becomes sandy with thick (1-3m thick) horizons of sandstone, silty shales and dolomite.
Flame structures
as seen on the
rock
Interbedding of pyritic
shale & dolomite
N29.22’48.3”
E79.26’10”
2027m
LOCATION: Narayan Nagar OBJECTIVES: To observe the rocks of Upper Krol - Tal succession, and
A thick succession of grey-black coloured, carbonaceous silty shales and dolomites marking the transition between the Krol and the Tal Formations. Corresponding sedimentary log
Succession of grey-black carbonaceous silty shales and dolomites marking the transition between the Krol and the Tal formations at
charkhet.
N29.23;6”
E79.25’50”
1849m
Strike=N10
Dip=21SE
This horizon marks the Precambrian-Cambrian boundary within the Lesser
Himalaya.
DAY THREE(19.12.11)
LOCATION: Pines Nala and OBJECTIVES: To observe Early- Proterozoic rocks of the Blaini Formation(Mussourie group) A thick succession (~1200m) of Blaini Formation is characterized by interbedded diamictite and quartzarenite sequence with subordinate representation of limestone,siltstone and shale horizons
Diamictite
1892m
N29.23’23”-
E79.28’40”
The diamictite units have sharp contacts with the quartz
arenites, and are mostly
matrix-supported
other secondary
structures visible are
hummocky
ripple,lamination etc
Plume structure
LOCATION: Bhowali (Cant) OBJECTIVES: To observe the rocks of Lower Krol Rocks of Lower Krol (Krol- A) are greenish grey gypsaceous silty shales characterizing fining upward cycles. The sequence shows small-scale parallel laminations, micro ripples, ripples cross-laminations and faintly developed large scale cross-beds. The bed transitions are sharp and sometimes even erosional.
strike=N203
dip=26SE
purple phyllite overlaying
diamictite overlaying
grey-green gypsaceous
silty shales
LOCATION: Bhimtal OBJECTICES: To observe Paleo-Proterozoic Bhimtal Volcanic suit The Palaeo-Proterozoic volcanism has been found in abundance in the region of the Kumaun Himalaya that led the stretching and partings of the floor of the Lesser Himalayan Sea. The Bhimtal Volcanics are vesicular, amygdaloidal, cut by dolerite dykes and sills and are associated with spilitic lavas.
N29.20’15”
E79.33’36”
1342m
Strike=N25
Dip=35SE
Highly weathered
basalt(greenish
hornblende basalt)
LOCATION: Amritpur OBJECTIVES: To observe ~1800my old Amritpur granite & deformation along MBT The Amritpur granites is Pre Himalayan, Precambrian granite of porphyritic and equigranular nature. The mineralogical and geochemical characteristics are consistent with those of S-type granites; however the melt produced by anatexis has intruded into the Precambrian Bhimtal-Bhowali litho succession.
942m
N29.18’37”
E79.33’26”
Thin section was made of
samples taken from here
Gorge section enroute Amritpur
Various coloured granite
samples were seen (purple to
leucocratic)
Dyke intrusion assumed due to
change in colours &
lithology.LEFT.
Gola river section near Amritpur is the most critical section that exposes a ~100m thick deformation zone, namely the MBT Zone. This zone consists several subzones each showing a characteristic style of deformation. This section clearly shows that the leucratic component of Amritpur granite overlies a well foliated and intensely kinked metabasalt green schist.
The section showing different deformation zones in Main Boundary Thrust
DAY FOUR(20.12.11)
LOCATION: Niglat (Bhowali Gaon)(10 KM stone) OBJECTIVES: To observe the Lowe-Proterozoic rocks of the Nagthat Formation The Nagthat Formation, made up of a thick succession (~1400m) of quartzarenite associated with penecontemporaneous lava flows, constitutes the lowest siliciclastic litho unit of the Krol-Belt. The basaltic flows are interbedded with the quartzarenite horizons. It is overlain by the Blaini Formation with a distinct sharp contact. The quartzarenites sequence of the Nagthat Formation comprising fine to coarse-grained quartzarenite interbedded with siltstone and grey to pink silty shales, shows coarsening upwards.
Very hard basalt
found pene-
contemporaeous
with Krol.
Blini & Krol Fm
contact seen
Lava & quartz
arenite seen
LOCATION:ENROUTE RATI GHAT
Pyrite leaching also seen
trough the rocks.
(golden in colour)
All types of tectonic folds
seen in road cut section
Folding,chevron folding
etc
LOCATION: Ratighat OBJECTIVES: To observe the Garampani Fault The Lesser Himalayan tear faults and fractures are oriented predominantly in the NW/NNW –SE/SSE directions, along them the streams and rivers have carved wide and straight valleys. The most important fault is the one which follows the north – south courses of the Garampani fault, established as a tear fault, follows the north-south courses of the Khairna and Kuch Gad streams, and is traceable through Ratighat and Garampani to Bamsyu on Bhowali – Ranikhet road section. Offsetting of Ramgarh lithounit by 700m, faulted quartz veins, fault breccia, slickensides, striations, faulting of fluvial terraces suggest a brittle nature of the Garampani fault.
CLOCKWISE presence of fault breccias suggests brittle nature of the fault, and mylonitized rocks relative movement of walls along the fault has produces slickensides with high angle & The trace of this fault is characterizes by fault scarp, cone and facets and straight sediment filled valley.
LOCATION: Lohai- Bhujan OBJECTIVES: To observe the Ramgarh Thrust and mylonitized Ramgarh Porphyry An assemblage of low-grade metamorphics, comprising of porphyritic granite, metaflysch, carbonaceous phyllites and marble, thrust over the Nagthat quartzites has been recognized as the Ramgarh Nappe. The marginal parts of these granitic rocks are mylonitic to ultramylonite/pseudo trachyte and finegrained streaky banded mylonites found in a wide zone.
Mylonitic to ultramylonite and fine- grained streaky banded mylonite.
Quart z vein intrusions in rocks of Ramgarh.& quartz Vein in 2D
Micro hydro electric project,Ramgarh
LOCATION :Kakrighat OBJECTIVE:to view Garnet Mica schist At Kakrighat quartz-mica-schist (garnetiferous) of the Saryu Formation of Almora Group are thrust over fine grained sericitic quartzites and metasiltstone of the Nathuwakhan Formation of Ramgarh Group along the South Almora Thrust (SAT). Increase in grade of metamorphism and deformation has been observed from base (green schist facies) to top (amphibolite facies) across the SAT.
Garnet mica schist from
Kakrighat.
LAB WORK
THE THIN SECTION AND SEM-EDS WERE MADE OF THE FOLLOWING:
Basalt
Trachytic texture
Granite
Garnet mica Schist
HORNEBLEND BASALT FROM
BHIMTAL
MINERALS PRESENT: p-clase,
Quartz,Hornblende,pyroxene
Amritpur granite
Minerals present:
quartz,plagioclase,
biotite, muscovite
GMS from kakrighat
Augen structure, mica fish, garnet,
biotite, quartz, muscovite
Scanning Electron Microscope
granite
Spectrum processing :
Peak possibly omitted : 2.142 keV
Processing option : Oxygen by stoichiometry (Normalised)
Number of iterations = 2
Element Weight% Atomic% Compd% Formula
Na K 1.26 1.15 1.69 Na2O
Mg K 0.51 0.44 0.85 MgO
Al K 11.41 8.87 21.55 Al2O3
Si K 30.30 22.63 64.81 SiO2
K K 5.11 2.74 6.16 K2O
Ti K 1.02 0.45 1.71 TiO2
Fe K 2.51 0.94 3.22 FeO
O 47.88 62.78
Totals 100.00
Garnet Mica Schist
Spectrum processing :
Peaks possibly omitted : 2.140, 9.720 keV
Processing option : Oxygen by stoichiometry (Normalised)
Number of iterations = 2
Element Weight% Atomic% Compd% Formula
Na K 2.17 1.96 2.92 Na2O
Al K 9.68 7.46 18.29 Al2O3
Si K 32.73 24.23 70.02 SiO2
K K 4.16 2.21 5.01 K2O
Ti K 0.67 0.29 1.13 TiO2
Fe K 2.04 0.76 2.63 FeO
O 48.54 63.08
Totals 100.00
GARNET MICA SCHIST
Spectrum processing :
Peaks possibly omitted : 2.143, 4.450 keV
Processing option : Oxygen by stoichiometry (Normalised)
Number of iterations = 3
Element Weight% Atomic% Compd% Formula
Na K 0.81 0.75 1.09 Na2O
Mg K 1.87 1.65 3.10 MgO
Al K 9.23 7.32 17.43 Al2O3
Si K 29.03 22.14 62.11 SiO2
K K 9.73 5.33 11.72 K2O
Ca K 0.61 0.32 0.85 CaO
Fe K 2.87 1.10 3.69 FeO
O 45.85 61.38
Totals 100.00
Basalt
Comment:bhimtal basalt
Conclusion
Our second field trip to Uttrakhand (Nainital) was a success and an
enthralling experience in all ways. It enhanced our knowledge about
various aspects of geology from structural to stratigraphy.
We were made familiar with geology of Uttrakhand in general&
Nainital in particular. We also got to know about the various textural
varieties of rock and their identification. We have observed various
kinds of folds and different kinds of intrusion. We learnt various
aspects of sedimentational environment through ripples and cross-
bedding.
We are thankful to our department for providing this opportunity to
us. We are also thankful to our professors for their guidance during
this field.
Bibliography
• Field guide by P.D. Pant