Abstract. Tsunami, storm and flash-flood event layers, which have been deposited over the last century on the shelf offshore Khao Lak (Thailand, Andaman Sea), are identified in sediment cores based on sedimentary structures, grain size compositions, Ti / Ca ratios and 210Pb activity. Individual offshore tsunami deposits are 12 to 30 cm in thickness and originate from the 2004 Indian Ocean Tsunami. They are characterized by (1) the appearance of sand layers enriched in shells and shell debris and (2) the appearance of mud and sand clasts. Storm deposits found in core depths between 5 and 82 cm could be attributed to recent storm events by using 210Pb profiles in conjunction with historical data of typhoons and tropical storms. Massive sand layers enriched in shells and shell debris characterize storm deposits. The last classified type of event layer represents reworked flash-flood deposits, which are characterized by a fining-upward sequence of muddy sediment. The most distinct difference between storm and tsunami deposits is the lack of mud and sand clasts, mud content and terrigenous material within storm deposits. Terrigenous material transported offshore during the tsunami backwash is therefore an important indicator to distinguish between storm and tsunami deposits in offshore environments.
Abstract The timing and magnitude of sea-surface temperature (SST) changes in the tropical southern South China Sea (SCS) during the last 16,500 years have been reconstructed on a high-resolution, 14 C-dated sediment core using three different foraminiferal transfer functions (SIMMAX28, RAM, FP-12E) and geochemical (U k′ 37 ) SST estimates. In agreement with CLIMAP reconstructions, both the FP-12E and the U k′ 37 SST estimates show an average late glacial–interglacial SST difference of 2.0°C, whereas the RAM and SIMMAX28 foraminiferal transfer functions show only a minor (0.6°C) or no consistent late glacial–interglacial SST change, respectively. Both the U k′ 37 and the FP-12E SST estimates, as well as the planktonic foraminiferal δ 18 O values, indicate an abrupt warming (ca. 1°C in <200 yr) at the end of the last glaciation, synchronous (within dating uncertainties) with the Bølling transition as recorded in the Greenland Ice Sheet Project 2 (GISP2) ice core, whereas the RAM-derived deglacial SST increase appears to lag during this event by ca. 500 yr. The similarity in abruptness and timing of the warming associated with the Bølling transition in Greenland and the southern SCS suggest a true synchrony of the Northern Hemisphere warming at the end of the last glaciation. In contrast to the foraminiferal transfer function estimates that do not indicate any consistent cooling associated with the Younger Dryas (YD) climate event in the tropical SCS, the U k′ 37 SST estimates show a cooling of ca. 0.2–0.6°C compared to the Bølling–Allerød period. These U k′ 37 SST estimates from the southern SCS argue in favor of a Northern Hemisphere-wide, synchronous cooling during the YD period.
The Turpan Basin, a back-arc basin formed during Late Permian, underwent first thermal subsidence and then flexure subsidence. The thermal subsidence took place during Late Permian and Early Triassic following the period of magmatic activities in this region. The flexural subsidence was throughout the Middle Triassic to Early Tertiary induced by orogenic movements which produced periods of high subsidence rates. Accelerated subsided periods occurred during Late Triassic/Early Jurassic, Late Jurassic, terminal Jurassic/initial Cretaceous, and terminal Cretaceous/early Cenozoic, indicating the effect of the collision and accretion onto the south Asian continental margin of the Qiangtang Block in Late Triassic/Early Jurassic, the Gangdise Block in Late Jurassic and terminal Jurassic/initial Cretaceous, and the Indian subcontinent in the terminal Cretaceous/early Cenozoic. There are relatively large breaks in the variation of the petrologic and geochemical data among these events. The Turpan Basin evolved from a back-arc basin in late Paleozoic into a foreland basin in Mesozoic, and a large intermontane basin of the Tianshan Mts. in Cenozoic.