Washover deposits formed by overwash are important deposits for evaluating the stratigraphy and evolution of coastal environments. Examination of preserved washover fans also provide a palaeotempestological record that can used to inform on past and recent coastal risk with a view to predicting future coastal risk. To evaluate coastal systems and accurately recognise past washover deposits, requires detailed knowledge of the internal structure of recent deposits including washover fans. We used very high frequency Ground Penetrating Radar and satellite imagery to examine the internal architecture of the 31 st December 2011 Cyclone Thane surge-generated washover deposit on the beach that blocked the Then Pennai River at Thazhamkuda, near Cuddalore in Tamil Nadu Province, southeastern India. Cyclone Thane overwash overtopped the beach and deposited sediments on the contemporary beach and behind the beach within the former channel of the blocked river. The modern washover fan thus contains sediments that are preserved subaqueously Manuscript File Click here to view linked References and subaerially. We demonstrate that the internal architecture of the fan at Thazhamkuda is largely controlled by the pre-existing topography, and erosional and depositional processes as the cyclone washed sediment inland. At the landward margin of the fan, terminal foreset bedding is preserved and this sedimentary structure remains one of the only features that can discriminate storm and over tsunami deposits.

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Fault-bounded sag pond sediment records are commonly found to be excellent archives of palaeoearthquakes and more rarely, they can provide robust evidence of local environment and climate change. We examined the sedimentary and geomorphological record of the Aksay Pond within the Karachingar Valley along the southern margin of the Altai Mountain Range in northwestern China. This pond is associated to a shutter ridge resulting from cumulative deformation associated with successive earthquakes along the Fuyun Fault, including the most recent 11 August 1931 Mw7.9 Manuscript Click here to view linked References earthquake. However, detailed chronology based on 14 C Accelerator Mass Spectrometry, 210 Pb and 137 Cs dating suggests that only deformation related to the 1931 earthquake have been preserved at the pond site. A small wedge of sediments comprising cobble and gravel sized clasts are separated by two palaeosoil deposits suggesting that very minor sediment could accumulate prior to 1931. In the northern part of the pond, sediment was deposited predominantly from a colluvial fan that has periodically been mobilised from the steep mountain slopes to the east. In the southern part of the pond we find that the dry climate of the region has experienced periodic storms that have resulted in the deposition of 11 fining upwards packages formed by remobilised and deposited sand to mud-sized sediments within the pond. Associated with these fining upward cycles are two colluvial wedges that emanate from the fault scarp. The upper wedge is dated at approximately 1986 CE and coincides with a high precipitation event recorded at the Fuyun Meteorological Station in 1986. The middle wedge may be related to an earlier high precipitation event, but due to challenges in obtaining accurate ages, cannot be verified. Alternatively, these two colluvial wedges could coincide with minor ca. Mw5 earthquakes in the region. Importantly, these wedges are not associated with large scale rupturing similar to the 1931 earthquake. Based on the sedimentary and geomorphological evidence of the Aksay Pond, we propose a model for the sequential formation of sag ponds highlighting the influence of both climatic and tectonics processes.

Burning histories derived from charcoal preserved in sediment archives offer scope to reconstruct past climate and landscape dynamics. The fault-bounded Aksay Pond in northwestern China preserved 24 macrocharcoals that when analysed for 14C using Accelerated Mass Spectrometry recorded three periods spanning two sigma error ranges of 1053 to 1379 CE, 1424 to 1622 CE and 1652 to 1990 CE. These periods of charcoal formation span the early to middle stages of the Medieval Climate Anomaly, the early stages of the Little Ice Age (LIA), and the transition from peak LIA to Recent Warming. The charcoal record from Aksay Pond differs from other Altai climate and burning records suggesting the region has a complex burning history.