A multi-proxy palaeonenvironmental reconstruction from sediment cores, offshore Iran - Natural hazards and climatic change within the Late Holocene

Abstract

During the last millennia, North African and Arabian palaeoclimatic records indicate a number of important climatic transitions. As a direct consequence, terrestrial ecosystems experiences significant changes. Although palaeoenvironmental records do exist in proximity to the north-western Arabian Sea, they remain sparse and provide little insight into environmental and climatic change of this region during the Late Holocene (the dating here is from 2300 cal. yr BP to present). Additionally, the north-western Arabian Sea is prone to natural disasters including recent cyclones and tsunamis such as the Makran tsunami, 1945 and cyclone Gonu, 2007, which leave a signal in the sediment. This thesis presents the results of detailed pollen and dinoflagellate cyst analysis in concert with a range of sedimentological techniques from sediment cores recovered from southern Iran (Chabahar Bay, Sea of Oman, Iran 25° 20’N, 60° 30’E). The data reveal the patterns of vegetation and oceanographic response to climatic change during the Late Holocene in the north-western Arabian Sea. Zonation on pollen and dinoflagellate results divides the last 2300 years into three distinct climatic phases: a wet period (2300 – 1830 cal. yr BP), a dry period (1830 – 1500 cal. yr BP) and a wet period (1500 – 120 cal. yr BP). The wet period (2300 – 1830 cal. yr BP) corresponds with well-known phases of intensive agriculture, including the Sassanid Period. The dry period (1830 – 1500 cal. yr BP) corresponds well with the end of the Beysehir occupation phase in southern Turkey. Moreover, an abrupt event is preserved in a single core and is dated at AD < 1808. Palynological evidence constrains the source of the sediment to be inner-continental but not of coastal origin, with a fluvial flood being the most likely mechanism of transportation.