• SAJID ALI

      Articles written in Journal of Earth System Science

    • Impact of climate on the evolution of vegetation in tectonically active Karewa basin, Kashmir Himalayas

      ANJUM FAROOQUI SURESH K PILLAI DEEPA AGNIHOTRI SALMAN KHAN RAJNI TEWARI SUNIL K SHUKLA SAJID ALI S K PANDITA KAMLESH KUMAR G D BHAT RAJESH AGNIHOTRI

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      The rise of the Himalayas governed the Indian Summer Monsoon in Karewa basin during Plio-Pleistocene. A palynological study is presented to delineate the climate-vegetation relationship using an 8.5-m thick fluvio-lacustrine sequence of the Hirpur Formation (2.4–2.1 Ma). Our results suggest that the sediment sequence is mainly comprised of two units, namely, Unit 1 and Unit 2. Unit 1 shows the dominance of sub-tropical to broad-leaf temperate vegetation when mean annual temperature (MAT) was ${\sim}$ 17$^{\circ}$ C and mean annual precipitation (MAP) was 1025 mm. The subsequent increase in sand followed by a thin lignite layer with Trapa, megafossil (fruits) demarcates fluvial adjustments, suggesting a low altitude fluvio-lacustrine ecosystem. Conversely, Unit 2 shows a decline in rainforest pollen with a steady increase in conifers. The abrupt dominance of diatom species Tetracyclus lacustris and related species with MAT and MAP reducing to 10$^{\circ}$ C and 770 mm reveal a colder climate with the lacustrine ecosystem. This change of tropical to cool temperate vegetation could be attributed to the altitudinal rise of the Pir Panjal Mountains and consequent obstruction of the south-west monsoon, which resulted in lower precipitation and temperature during ${\sim}$ 2.4–2.1 Ma. Hence, the relic tropical flora of Palaeogene/Neogene transformed to Himalayan temperate flora sometime ${\sim}$ 2.1 Ma.

      $\bf{Highlights}$

      $\bullet$ Climate–vegetation relationship is established through a palynological record.

      $\bullet$ Unit 1 comprises subtropical to broad-leaf temperate vegetation with warmer mean annual temperature and higher mean annual precipitation.

      $\bullet$ Unit 2 comprises colder diatom species and is following cooler mean annual temperature and lower mean annual precipitation.

      $\bullet$ A shift of tropical to cool temperate vegetation is related to the rise of the Pir Panjal Mountains, obstructing monsoon.

    • Geochemical evidence for the provenance, tectonic settings and depositional environment during the Cambrian Series 2-Wuliuan (Miaolingian) from the Kunzam La Formation in the Sumna Valley, Spiti, NW Himalaya

      GARRY SINGLA SAJID ALI BIRENDRA P SINGH OM N BHARGAVA SCOTT MORRISON RAMANPREET KAUR MADHUSUDHAN SATI STANZIN STOPDEN

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      We present trace-element compositions and rare-earth elements (REEs) analyses of the Cambrian Series 2-Wuliuan (Miaolingian), Kunzam La Formation from the Sumna Valley, Spiti, Tethyan Himalaya, in order to identify the provenance, tectonic settings and depositional environment in the region. The trace elemental ratios (Th/Co, Th/Sc, La/Sc, Cr/Th) and REE patterns show compositions similar to the felsic composition, which are comparable with the upper continental crust, suggesting that the sediments in the Sumna Valley were derived from a felsic source that possibly lie in the felsic igneous province of the old Precambrian Indian craton. The elemental discrimination diagrams show deposition of the Sumna Valley rocks in a passive continental margin tectonic setting. The selected trace-element ratios such as V/Cr, Ni/Co, Th/U and V/V+Ni as well as positive Ce and negative Eu anomalies indicate oxidising conditions prevailed during the deposition of the Cambrian Series 2-Wuliuan (Miaolingian) rocks. The concentration of Y and Rb trace elements indicates continental sediments depositional site was proximal and close to near-shore environment. Finally, the low REE+Y and selected trace elements (La, Th, Sc, Ni, Cr, V, U, Rb, Zn, Y) concentration indicate a major transgressive event at the boundary of the Cambrian Series 2-Wuliuan (Miaolingian) associated with the Oryctocephalus indicus biozone.

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