Tracing Tectonic Activity with Frogs
Sunday, August 8, 2010 11:06:49 AM
The collision of the Indian continent with Eurasia affected the regional wildlife. Looking into the genetic evolution of a special frog species has now highlighted critical aspects of the timing of geological events responsible for the currents geography of Southeast Asia.
The findings are published in PNAS of 3 August 2010 as a freely available open access paper:
Che et al.
Spiny frogs (Paini) illuminate the history of the Himalayan region and Southeast Asia
I am grateful for the open access option. Thank you, PNAS.
Following the initial collision between India and Asia in the early Cenozoic (ca. 50–55 million years ago) or even earlier, about 70 million years ago, many effects associated with the major tectonic episode continued through the Oligocene (34 - 23 million years) and well into the Miocene (about 23 - 5 million years ago). During these times, associated geological processes occurred, ranging from the uplift (thickening) of the Himalaya–Tibetan plateau to lateral extrusion of the continental land-mass. However, details of the evolution in space and time related to the creation of the Himalayas and the Tibetan Plateau are still debated.
Most species of the tribe Paini (often called stone frogs in China) prefer to sit on moss-covered rocks near cold mountain streams. This long-conserved life history trait, coupled with their present distribution in Asia, makes this species group a potential model for examining geological evolution and environmental changes in Asia during the Tertiary. Their diversification can be related to massive mountains and deeply carved valleys acting as barriers, adaptations from streams to still water environments, adaptation to low oxygen levels on the Tibetan Plateau, and other drastic environmental changes.
The sequence of evolution supports a minority view of how the India/Asia collision played out. Rather than merely pushing the Himalayas upward, as some geologists believe, the Indian plate also pushed Southeast Asia and China aside and toward the Pacific Ocean, a process referred to as extrusion or escape tectonics.
The process sometimes known as escape tectonics, first elucidated by Paul Tapponnier, occurs during a collisional event where one of the plates deforms internally along a system of strike-slip faults. Between 1975 and 1981, Paul Tapponnier proposed, along with Peter Molnar, that most of today's deformation observed in Eastern Asia, where the greatest continental fault system occurs (20 earthquakes with a magnitude >8 since 1892), is the result of the penetration of India, at a speed of more than 5 cm per year, inside the Asian continent. India, modeled as a rigid block, has made its way over more than 2500 km, northward, inside Asia, causing the extrusion of the Indochinese peninsula and Southeast Asia. This extrusion also leads to the formation of two rifts, the most famous being that of Lake Baikal. This became the first coherent and global explanation for a great variety of deformations and structures observed in the Himalayan and Tibetan regions.