Is the Simultaneous Onset of the Florida, East Australia, and Indian
Ocean Currents Related to Himalayan tectonics?
Abstract
Carbonate drift deposits in the Santaren Channel, on the Marion Plateau
and in the Inner Sea of the Maldives were cored and dated by ODP and
IODP expeditions. The ages based on biostratigraphy of these drifts are
11.4 Ma (Marion Drift), 12.3 Ma (Santaren Drift) and 12.9 Ma (Maldives
Inner Sea), indicating a near simultaneous onset of the Florida, East
Australia and Indian Ocean Currents that are all part of the global
ocean current system. The Himalayan tectonics started with the collision
of the Indian continent with Asia about ~50 Ma ago and
continues today. The uplift of the Himalaya and Tibetan Plateau was not
steady and not consistent across the mountain belt. The uplift of the
southern and central Tibetan Plateau occurred from 40–35 Ma, at the
northern Tibetan plateau at approximately 25–20 Ma, and at the
northeastern to eastern Tibetan plateau at ~15 Ma.
Significant increases in altitude of the entire Tibetan plateau are
thought to have occurred about 10–8 Ma agoor more recently, some 3 myrs
after the onset of the modern Indian Ocean monsoon-driven circulation
system that is dated at 12.9 Ma. This sudden onset or intensification is
puzzling in light of the continuous uplift of the Himalaya and Tibetan
Plateau. If a linkage between tectonics and climate exists, the uplift
must have stepped over a threshold that caused the climate to change
dramatically. The near simultaneous onset of the global ocean
circulation and the intensification of the monsoon is strong evidence
that a combination of factors caused the sudden climate change. It is
likely that onset of the intense monsoon is the combined result of the
tectonic configuration, consisting of the Himalayan uplift but also the
closing of the Tethyan seaway, and progressive glaciation on Antarctica.