Paleoclimatic and vegetational change in the Siwalik sub-Group of Pakistan and its contemporary geographic regions: a stable isotope perspective

  • M. T. Waseem (Contributor)
  • A. M. Khan (Contributor)
  • Jay Quade (Contributor)
  • S. Von Nelson (Contributor)

Dataset

Description

Paleoclimatic archives preserved in bioapatite provide long-term temporal records of climatic change and allow us to explore how climate may have affected faunal and floral changes through time. Among the most comprehensively debated research questions is the question of C<sub>4</sub> grassland expansion and its effects on community structure and dynamics. Here, we present compiled datasets of carbon isotopes from fossil tooth enamel and paleosol to evaluate how C<sub>4</sub> grasslands expanded and its apparent causes. The C<sub>4</sub> expansion has been argued to be around <i>ca</i> 8–7 Ma in the Siwalik sub-Group of Pakistan, but the later stages of C<sub>3</sub>/C<sub>4</sub> proportion shifts on the Siwalik floodplains are less understood. We found that although C<sub>4</sub> expansion occurred during the late Miocene, C<sub>3</sub> vegetation never entirely disappeared but was persisted in pockets on floodplain up to the present, as indicated by the C<sub>3</sub> diet consumed by some herbivores. The expansion was further modulated by the microclimate in different regions. The same scenario can be seen in East Africa, South America and low-latitude North America where C<sub>4</sub> grasslands expanded rapidly in late Miocene most likely owing to decrease in global <i>p</i>CO<sub>2</sub>. By contrast, C<sub>4</sub> plants did not expand in high-latitude North America and Palearctic regions during the past <i>ca</i> 17 Ma. Thus, we assume that C<sub>4</sub> plants expanded at low latitudes during the late Miocene owing to one major global factor (decreased <i>p</i>CO<sub>2</sub>) and perhaps other local microclimatic factors like paleofires.KEY POINTSDuring the late Miocene, low-latitude regions experienced a climatic change followed by a transition from C<sub>3</sub> to C<sub>4</sub> vegetation.The timing of C<sub>4</sub> expansion was not synchronous across all the regions and was controlled by global and microclimatic factors.Although C<sub>4</sub> vegetation expanded after the late Miocene, C<sub>3</sub> vegetation did not disappear and was present at the edges of floodplains.The new adaptive physiologies (like hypsodonty) in faunal elements were evolutionary adaptive responses toward new vegetational types available. During the late Miocene, low-latitude regions experienced a climatic change followed by a transition from C<sub>3</sub> to C<sub>4</sub> vegetation. The timing of C<sub>4</sub> expansion was not synchronous across all the regions and was controlled by global and microclimatic factors. Although C<sub>4</sub> vegetation expanded after the late Miocene, C<sub>3</sub> vegetation did not disappear and was present at the edges of floodplains. The new adaptive physiologies (like hypsodonty) in faunal elements were evolutionary adaptive responses toward new vegetational types available.
Date made available2021
PublisherTaylor & Francis

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