New constraints on the sedimentation and uplift history of the Andaman-Nicobar accretionary prism, South Andaman Island

As an important driver of global climate change during the Cenozoic, the uplift of the Tibetan Plateau (TP) has strongly influenced the origination and evolution of the Asian monsoon system, and therefore the aridification of central Asia. Over the last two decades, the application of stable isotope paleoaltimeters and the discoveries of mammal and plant fossils have greatly promoted the understanding of the uplift history of the TP. However, paleoaltitudinal reconstructions based on different paleoaltimeters have suggested differing outcomes and therefore remain controversial. Novel paleoaltimeters have therefore needed to be developed and applied to constrain the uplift history of the TP more accurately and effectively by comparing and verifying multi-proxies. Paleothermometers based on glyceryl dialkyl glycerol tetraethers (GDGTs) are widely used in terrestrial and ocean temperature reconstructions. In this study, GDGT-based paleothermometers were tentatively applied to the Gyirong Basin on the southern TP, and the Xining Basins on the northern TP, in an attempt to quantitatively reconstruct their paleoaltitudes.Both soil and aquatic-typed branched GDGTs have been identified from Late Miocene to Mid-Pliocene (7.0-3.2 Ma) samples taken from the Gyirong Basin; their reconstructed paleotemperatures were 7.5&#177;3.3&#176;C and 14.2&#177;4.5&#176;C, respectively. The former temperature may represent the mean temperature of the terrestrial organic matter input area, while the latter may represent the lake surface temperature. The results would suggest that the lake surface of the Gyirong Basin during the Late Miocene to Mid-Pliocene was 2.5&#177;0.8 km and that the surrounding mountains exceeded 3.6&#177;0.6 km, implying that the central Himalayas underwent a rapid uplift of ~1.5 km after the Mid-Pliocene.GDGT-based paleotemperature reconstructions using MBT'5ME values show that the Xining Basin dropped in temperature by ~10&#176;C during the ~10.5-8 Ma period, exceeding that in sea surface temperatures and low-altitude terrestrial temperatures during these periods. By combining these results with contemporaneous tectonic and sedimentary records, we infer that these cooling events signaled the regional uplift with the amplitude of ~1 km of the Xining basins. Our results support that the TP was still growing and uplifting substantially since the Late Miocene, which may provide new evidence for understanding the growth, expansion and uplift patterns of the TP.

Download Full-text

Palynodiversity in the Climbers of Andaman Islands, India

Indian Journal of Forestry ◽

10.54207/bsmps1000-2016-7uev2b ◽

2016 ◽

Vol 39 (2) ◽

pp. 125-131

Author(s):

Mudavath Naik ◽

J. Kailas ◽

H. Ramakrishna ◽

Boyina Rao

Keyword(s):

Morphological Characters ◽

Andaman Islands ◽

Andaman Island ◽

South Andaman

The present investigation deals with the study of pollen diversity of forty one climbers of forests in South Andaman Island. These 41 taxa belong to diversified families viz. Acanthaceae, Apocynaceae, Asteraceae, Capparaceae, Combretaceae, Convolvulaceae, Cucurbitaceae, Euphorbiaceae, Fabaceae, Hernandiaceae, Lauraceae, Passifloraceae, Polygonaceae, Malvaceae, Rhamnaceae, Rubiaceae and Sapindaceae. The pollen of these taxaare diversified in morphological characters viz., symmetry, shape, polarity, apertural pattern and ornamentation.

Download Full-text