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      https://www.ias.ac.in/article/fulltext/jess/130/0093

    • Keywords

       

      Palynology; diatoms; sponge spicules; sediment texture; Karewa; Indian summer monsoon.

    • Abstract

       

      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.

    • Author Affiliations

       

      ANJUM FAROOQUI1 SURESH K PILLAI1 DEEPA AGNIHOTRI1 SALMAN KHAN1 RAJNI TEWARI1 SUNIL K SHUKLA 1 SAJID ALI1 S K PANDITA2 KAMLESH KUMAR1 G D BHAT1 RAJESH AGNIHOTRI1

      1. Birbal Sahni Institute of Palaeosciences, 53, University Road, Lucknow 226 007, India.
      2. Department of Geology, University of Jammu, Jammu 180 006, India.
    • Dates

       
  • Journal of Earth System Science | News

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