Olajide Oladipo

Research subject

Insights into recent environmental variability in Sumatra (Indonesia) from lacustrine sub-bottom profiles and sediment cores

Lake sediments are fantastic archives of long-term (e.g., climate) and short-term (e.g., floods, landslides, and volcanic eruptions) geological processes. These processes, together with anthropogenic activities, are known to cause significant environmental changes to the lake system, resulting in processes such as eutrophication and pollution. Previous studies around the world have successfully demonstrated that utilization of continuous lake records can serve as excellent archives, not only for climate variability and tectonic events through time, but also to determine the magnitude of human impacts on the environment. The latter is highly important when tackling overpopulated areas in fast growing economies and the impact they have in the natural system, such as in Indonesia. Lake Maninjau in western Sumatra, might possess the necessary record for tackling such a goal. In fact, the records of climatic changes, tectonic events and impacts of anthropogenic activities in the region of Lake Maninjau, one of earth’s largest volcanic lakes, are far from being known due to the lack of documentation.

Thus, this proposed study aims to amalgamate shallow sub-bottom profile (CHIRP) data and short sediment cores recovered from Lake Maninjau in western Sumatra (Indonesia) with the aim of:  (a) estimating the age and scale of occurrences of past natural hazards such as volcanic eruptions, landslides, or flooding, (b) assessing the limnological processes that occurred in this region and shaped the evolution of the lake through time, and (c) revealing the anthropogenic activities in the region and their possible impact on the environment. Preliminary results of geophysical data analysis reveal a nearly flat ~165 m deep lake floor with some hard substrate morphologies, and a structural high in the center of the lake that seems to have divided the lake basin into two -the northern basin and the southern basin with different seismic reflection pattern and sedimentary basin fill occasionally disturbed by a sequence of events, interpreted as mass wasting deposits, some of which are closely associated with fluid escape features. Four short sediment cores have been retrieved and consecutively sampled for age determination (210Pb and radiocarbon), C/N ratio, and isotope analyses while magnetic susceptibility and XRF data sets are being analyzed. The study shall shed light on both climatic and anthropogenic changes that shaped the Lake Maninjau system aiming to present a better knowledge of the centennial scale environmental variability in the region, with implications for understanding climatic and anthropogenic changes in other similar volcanic lake systems elsewhere.

The project was done in collaboration with Dr. Caroline Bouvet de la Maisonneuve from the Earth Observatory of Singapore at Nanyang Technological University.