Clay Minerals as Climate Change Indicators—A Case Study

The clay mineralogy of the Late Pliocene-Early Pleistocene Pinjor Formation of the type area, northwestern Himalaya, India has been investigated to understand the paleoclimatic conditions and paleotectonic regime prevailing in the frontal Himalayan terrain during 2.5 Ma to 1.7 Ma. The clay minerals were investigated by X-ray diffraction analysis and scanning electron microscope studies. Study of the oriented aggregates of 47 representative clay samples of the Pinjor Formation of the type area reveals that illite is the most dominant mineral followed by chlorite, kaolinite, vermiculite and mixed layer clay minerals. The distribution of the clay minerals in the three lithostratigraphic units of the Formation, namely the Kona Clay Member, the Tanda Bhagwanpur Wacke Member and the Chauki Nadah Pebbly Bed Member which are well exposed along the Berwala-Mandhna section, the Kona-Karaundanwala section and the Ghaggar River-Chauki Nadah section, is nearly uniform suggesting thereby the prevalence of similar sedimentation environments in the Himalayan foreland basin. The presence of illite and kaolinite suggests their derivation from crystalline rocks containing felspar and mica as also from pre-existing soils and sedimentary rocks. Further, the paleoclimatic conditions were moderate. Presence of chlorite suggests the weathering of intermediate and basic crystalline rocks and low grade metamorphic rocks in the positive areas. The presence of kaolinite in the Pinjor Formation is mainly attributed to the weathering and subsequent leaching of the mineral from granitic and basic rocks in the hinterland. Vermiculite has been mainly formed by weathering and transformation of biotite. Warm and humid climatic conditions prevailed for a major part during the deposition of the detritus which favored weathering and transformation of minerals. During the terminal phase of sedimentation there was renewed tectonic activity which had a significant impact on climate as precipitation and mechanical weathering rates increased substantially. Post 1.7 Ma there was a marked shift in temperature patterns and subsequent cooling of the landmass, which resulted in a decreased vegetation cover and a subsequent decrease in animal population thriving on it.

Morphotectonic Study of Frontal Siwalik Hills, near Gandhiri, Kangra, Himachal Pradesh, India

The densely populated foothill zone of western Himalaya between the Beas river and the Chakki stream in and around Kangra is being critically examined by us considering the seismo-tectonic destructive potential of the 1905 (Mw 7.8) Kangra earthquake which has not been evaluated so far. We use Resourcesat 1: LISS III Ortho satellite imageries and field studies to qualitatively and quantitatively assess the active tectonic setup of the terrain. Quantitative morphotectonic analysis viz. hypsometric integral, drainage basin asymmetry, stream sinuosity index, ratio of valley floor width to valley height, stream length gradient index, basin shape index and mountain front sinuosity index are being evaluated on high resolution digital elevation model. The five sub-drainage basins of the Gandhiri stream, the Sukar stream and the Duhg stream of Kangra district of Himachal Pradesh, India are being morphotectonically analyzed. The value of hypsometric integral, drainage basin asymmetry, stream sinuosity index, ratio of valley floor width to valley height, stream length gradient index, basin shape index and mountain front sinuosity index reveal that the terrain is tectonically active. An active dextral strike slip fault with significant oblique slip component has been inferred and is being named as the Gandhiri Fault. This fault crosses all the five sub-drainage basins and results in multiple stream offsets. The Index of Relative Tectonic Activity (IRAT) has been established for different sub-drainage basins. The study reveals that the terrain near Gandhiri in Kangra district of Himachal Pradesh is seismo-tectonically active and proper building codes should be followed in construction activity.

Active Tectonic Strike-Slip Fault Development near Goran, Samba and Kathua Districts, Jammu and Kashmir

Active tectonic morphometric studies of the sparsely investigated frontal Siwalik terrain around Goran in the Samba district bordering the Kathua district of J&K reveal the presence of NW-SE trending active sinistral strike-slip fault with oblique slip component which is parallel to the Surin-Masatgarh anticline. The Basantar River, the Tarnah stream, the Ujh River, the Sahaar stream and the Ravi River exhibit significant stream offsets where the fault crosses these channels. The values of the morphometric indices viz. stream sinuosity index (S), stream length gradient index (SL), valley floor width to valley height ratio (Vf), mountain front sinuosity index (Smf), hypsometric integral (Hi), basin asymmetry ratio (AF) and basin elongation ratio (Eb) calculated along the linear river offsets with respect to longitudinal River segments of the Rivers Basantar, Tarnah, Ujh, Sahaar and Ravi Rivers reveal that terrain is tectonically active and can be placed in tectonic active class I. The fault has an apparent offset of about 2000 m with it as it crosses the Basantar, the Tarnah, the Ujh, the Sahaar and the Ravi Rivers. The stream offsets upon field and laboratory investigations are developed due to an active sinistral strike slip fault which is being named as Goran fault. This fault has a surface expression of 100 km extending from the Basantar in the northwest up to the Beas River in the southwest whereas the remaining segment may exist as a hidden fault all along the Himalaya.

Geological Observations from a Palaeolake Basin, Lamayuru, Ladakh, Northwestern Himalaya

A well known Buddhist monastery of Lamayuru is located in a village about 128 Km West of Leh. It is situated on more than 100 m thick Late Quaternary palaeolake deposits which are surrounded by rocks of Lamayuru Formation. Geologically, the Lamayuru Formation includes the Lamayuru and Namikala flysch deposits of Triassic-Jurassic age. This Formation is composed of shales, schist and phyllites. This Lamayuru Formation forms the base and source of palaeolake deposits. In Late-Pleistocene (35 ka B.P.) the Lamayuru River was dammed due to tectonically triggered landslide and the Lamayuru palaeolake came into existence. The sedimentation in the palaeolake basin commenced at 35 ka B.P. and culminated at 1 ka B.P. The deposits of palaeolake consist of carbonaceous mud, sand, silty clay and matrix supported breccia. The palaeolake deposits are a product of complex interplay of lacustrine, fluvio-deltaic to colluvial processes. The research study shows the prevalence of glacio-lacustrine conditions during the major part of depositional history as evidenced by the dominance of varves in these deposits.

Size Analysis of the Late Pliocene-Early Pleistocene Upper Siwalik Sediments, Northwestern Himalaya, India

Size analysis of the Late Pliocene-Early Pleistocene Upper Siwalik sediments comprising the Pinjor Formation in the type area and adjoining regions reveals that the sediments are bimodal to polymodal in nature, medium to fine grained and are moderately sorted. The inclusive graphic standard deviation and moment standard deviation values suggest the deposition of sediments in shallow to moderately deep fluvial agitated water. The log probability plots reveal that saltation mode is the dominant mode of transportation of detritus. The sediments are continental in character and are derived from crystalline, metamorphic and sedimentary rocks of the Himalaya exposed to the North of the type area Pinjor.