The Indus-Tsangpo Suture Zone (ITSZ), a pivotal geological feature in the Himalayas, has been identified as tectonically active by scientists from the Wadia Institute of Himalayan Geology (WIHG) in Dehradun. Prior to this discovery, the suture zone was assumed to be inactive or ‘locked’. The following article delves deeper into tectonics, the findings about the ITSZ, and the techniques used to determine its current state.
Tectonics – A Brief Overview
At the root of the discovery lies the science of Tectonics. This scientific study revolves around the deformation of rocks that constitute the Earth’s crust. It is concerned with the forces that cause such changes including those associated with mountain building, large-scale movements of the crust, and sudden displacements along faults.
Indications of Tectonic Activity in the ITSZ
Several geologic features corroborated the tectonic activity in the ITSZ. These observations include tilted sedimentary beds and thrust broken rivers, which are associated with uplifted terraces. Additionally, brittle deformation was found at much shallower depths in the bedrock. The age of these deformities was determined using Optically Stimulated Luminescence (OSL), with data on seismicity and denudation rates providing further support for the conclusion.
Techniques Used: OSL, Seismicity, and Denudation
OSL is a dating technique applied to deduce the last exposure of quartz sediment to light. It’s particularly useful in studying quaternary geologic periods, the most recent of which spanned the past 2.6 million years. Seismicity refers to the distribution and frequency of earthquakes, while denudation indicates the steady wear and tear of the Earth’s surface. These three factors played a crucial role in authenticating the findings of the WIHG scientists.
The ITSZ: An Overview and its Importance
The ITSZ is located in the Ladakh region, marking the boundary where the Indian and Eurasian plates collide. The region spans over 200 km and showcases a multitude of rock associations that suggest a complex nature of plate collision. Until recently, it was presumed to be a locked zone, but this research upends that notion and brings forth significant implications for earthquake research, seismic structure understanding, and the study of mountain chain evolution.
Understanding Suture Zones
Suture zones are belts characterized by intense deformation where different terranes with distinct tectonic, metamorphic, and paleogeographic histories meet. They offer valuable insights into deep oceanic crust and ancient seafloor processes. In plate tectonics, sutures are considered remnants of subduction zones, possibly representing fragments of different tectonic plates. Often, they manifest on the surface as mountain ranges comprised of intensely deformed rocks. Notable examples include the Iapetus Suture from Great Britain and the Indo-Tsangpo Suture in the Himalayas.
The groundbreaking discovery of the tectonic activity in the ITSZ renews our understanding of the Earth’s seismic structure, contributing substantially to the field of geology. However, it also necessitates revisiting existing geological theories, emphasizing the dynamic and evolving nature of our planet.