An aerial view of the Andaman Islands, India
An aerial view of the Andaman Islands, India, which lie on the accretionary wedge left over from the India-Myanmar oblique convergence. The boundary, along with many other features of the north Indian Ocean, was the focus of a recent workshop on the unique geodynamics of the region. Credit: Venkatesh k, CC BY-2.0

The northern Indian Ocean is home to some of the most spectacular tectonic processes on Earth thanks to a series of unique active and passive margins.

For example, the Bay of Bengal contains enormously thick fan sediments, whereas the archipelago of the Andaman and Nicobar Islands resides on an accretionary wedge resulting from the India-Myanmar oblique convergence. The Andaman-Sumatra subduction zone remains one of the most active convergent margins in the world, marked by major seismic events like the Mw 9.1 quake that caused the 2004 tsunami. The western Indian shelf adjoining the Arabian Sea, however, has one of the most enigmatic passive margins with anomalous magmatism. In addition, thick sediments on both Indian margins contain long-term records of monsoon-linked continental weathering, erosion processes, and tectonics. What’s more, open ocean bathymetric highs are key to reconstructing the history of intermediate- and deep-water circulation in the Indian Ocean.

The primary goal of the workshop was to foster new ideas for scientific drilling proposals in the northern Indian Ocean.

To identify and improve understanding of several geological paradoxes in this region, the National Centre for Polar and Ocean Research (NCPOR), India, hosted the second International Ocean Discovery Program workshop. The primary goal of the workshop was to discuss, deliberate, and foster new ideas for scientific drilling proposals in the northern Indian Ocean (Figure 1).

About 50 international scientists took part in more than two intensive days of plenary and breakout sessions, focused on three main priorities:

  1. understanding the tectonics of oblique convergence in the Andaman subduction zone, including the convergence-transpressional transition, the generation and propagation of seismicity, the effect of subduction of large sediment piles onto slab processes, the history of volcanism in the Andaman arc, the growth of continental crust beneath the arc, the timing and nature of back-arc spreading, and the relationship between the thermal structure of the oceanic crust and the development of magnetic anomalies
  2. recovering Asian monsoon archives from the Andamans and Indian margins: long-term, high-resolution records of Indian monsoon circulation from the Paleogene to present, including the influence of the Himalayan orogeny and its consequential signatures of uplift, weathering, erosion, and sediment deposition
  3. recovering depth transects from open ocean bathymetric highs, including the assessment of dust transport pathways; timing of gateway restrictions; and surface, intermediate-, and deep-water circulation over time

Proposals would fill critical knowledge gaps using tectonic, climatic, geochemical, and oceanographic information recovered from crustal rocks.

Each of these broad themes has the potential to answer high-priority scientific questions. Participants also emphasized the necessity of international collaboration for writing innovative drilling proposals. Such proposals would fill critical knowledge gaps using tectonic, climatic, geochemical, and oceanographic information recovered from the crustal rocks.

Fig. 1. Tectonics, paleoceanography, and paleoclimate regions of proposal interests around the Indian margin. These include the Andaman Nicobar Islands (AND), Andaman Sea (AS), Bangladesh margin (BM), eastern margin (EM), oceanic bathymetric highs (OBH), southern margin (SM), and western margin (WM). The red dashed line represents the subduction front. Red arrows represent oblique plate convergence rates. Credit: Dhananjai Pandey, Steven Clemens, Marie Edmonds

Attendees also formed operational working groups to communicate in the coming months and years and to promote increased participation by interested scientists who weren’t able to attend the workshop. To that end, full abstracts of the ideas discussed at the workshop are available on the workshop website.

The authors acknowledge financial support from the Ministry of Earth Sciences, India, the U.S. Science Support Program, and the European Consortium for Ocean Research Drilling. We are also grateful to the director of NCPOR, participants, and other session coordinators: J. S. Ray, A. D. Singh, and Nisha Nair.

—Dhananjai Pandey (, National Centre for Antarctic and Ocean Research, Vasco de Gama, India; Steven Clemens, Brown University, Providence, R.I.; and Marie Edmonds, University of Cambridge, U.K.


Pandey, D.,Clemens, S., and Edmonds, M (2018), Investigating the northern Indian Ocean’s puzzling geodynamics, Eos, 99, Published on 28 December 2018.

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