Accelerated mafic weathering in Southeast Asia linked to late Neogene cooling

Area of Science:

• Geochemistry
• Paleoclimatology
• Tectonics

Background:

• Arc-continent collisions in Southeast Asia during the Neogene may have influenced global cooling via chemical weathering of ophiolites, leading to atmospheric CO2 removal.
• The precise relationship between erosion, tectonics, and long-term climate evolution in this region remains poorly understood.

Purpose of the Study:

• To investigate the cause-and-effect relationships between erosion and the long-term evolution of tectonics and climate in Southeast Asia.
• To reconstruct an 8-million-year record of seawater chemistry and sediment provenance from the eastern Indian Ocean.

Main Methods:

• Geochemical analyses of foraminiferal shells and grain size-specific detrital fractions.
• Re-analysis of the seawater 87Sr/86Sr curve to assess mafic weathering rates.

Main Results:

• A significant increase in erosion and chemical weathering of ophiolitic rocks was observed after 4 million years ago (Ma).
• This increase coincided with widespread island emergence and strengthening Pacific sea-surface temperature gradients.
• Evidence suggests enhanced mafic weathering during the late Neogene.

Conclusions:

• Island uplift and hydroclimate changes in the western Pacific likely contributed to sustained atmospheric CO2 consumption throughout the late Neogene.
• These findings support the hypothesis that tectonic activity in Southeast Asia influenced global climate through chemical weathering processes.