Clay Minerals as Climate Change Indicators—A Case Study

Abstract

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.

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

“…In this paper, an attempt has been made to work out the size characteristics of the Late Pliocene-Early Pleistocene Upper Siwalik sediments with a view to comprehend the provenance and sedimentation environment of the detritus constituting the Pinjor sediments of the type area and adjoining regions. During the last decade, the sedimentology of the Siwalik Group has been examined by [1,[3][4][5][6][7][8][9][10][11] and others.…”

Paleoenvironmental conditions during deposition of Kolosh and Gercus formations in northern Iraq as deduced from clay mineral distributions

“…These minerals are useful indicators for the past changes in weathering regimes. In general, continental weathering is highly affected by climatic change, which in turn affects the weathering rates, runoff, soil formation, and transport of terrigenous (detrital) material to the sea [3,18,19].…”

Clinoform identification and correlation in fine‐grained sediments: A case study using the Triassic Montney Formation

“…() and Chaudhri & Singh () highlight the lithological and climatic drivers behind changes in clay content, although climate analysis using clay alone should be interpreted with caution (Thiry, ). With regard to lithology, illite may be detrital, having been weathered from feldspars and micas, while chlorite is produced from the weathering of crystalline intermediate and basic, or low‐grade metamorphic rocks (Chaudhri & Singh, ). Detrital illite is attributed to physical erosion being the predominant process within the hinterlands (Ruffell & Batten, ; Ruffell et al ., ).…”

“…Detrital illite is attributed to physical erosion being the predominant process within the hinterlands (Ruffell & Batten, ; Ruffell et al ., ). In contrast, kaolinite forms from the weathering of basic and granitic sources (Chaudhri & Singh, ). Additionally, as kaolinite is more prone to flocculation than other clays (e.g.…”