Mangrove ecosystems as indicators for environmental change (Oman, Indian Ocean)
Final Report Abstract
Mangrove ecosystems along the coastline of Oman today exist in isolated small patches. With Avicennia marina there is only a single species present. The most important findings on paleo-mangroves along the coastline of Oman is that substantially larger areas where covered during the Mid-Holocene. The disappearance of mangroves in most areas is related to climatic changes, rather than changes in sea level or human interference. There is clear sedimentological evidence, that the onset of dry conditions was abrupt. Radiocarbon dating results indicate that these changes took place 6000 years ago. At that time mangrove fringed lagoons existed. With the absence of freshwater input, the mangroves died off. These climatic changes are seen as a consequence of the southward shift of the Intertropical Convergence Zone and associated summer monsoon rainfalls. Evidence for a mid-Holocene sea level highstand was not documented. The mangrove soils identified rather suggest a sea-level on todays level. There is however, ample sedimentological and palaeontological evidence for Pleistocene sea-level highstands. Most of the documented facies suggest deltaic environments. These were found in elevations of up to 9m above present sea-level. There is no evidence for substantial tectonic movements so that these finding may be used for a global database on Pleistocene sea-level. We tentatively assign Marine Isotope Stage 5. A surprising finding was mangrove wood in association with a sediment layer that was identified as tsunamigenic by earlier research. Where these earlier studies failed to identify datable material and hence where not able to assign the time of the tsunami event, we could now date the wooden remains. Radiocarbon date revealed ages close to 1000 years. This date fits with other observations within the Northern Indian Ocean. Out results help to quantify the severity of this event.
Publications
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Collapse of Holocene mangrove ecosystems along the coastline of Oman. Quaternary Research, 100 (2020, 12, 29), 52-76.
Decker, Valeska; Falkenroth, Michaela; Lindauer, Susanne; Landgraf, Jessica; Al-Lawati, Zahra; Al-Rahbi, Huda; Franz, Sven Oliver & Hoffmann, Gösta
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Life on the Edge: A Powerful Tsunami Overwhelmed Indian Ocean Mangroves One Millennium Ago. Forests, 13(6), 922.
Decker, Valeska; Gee, Carole T.; Schucht, Pia J.; Lindauer, Susanne & Hoffmann, Gösta
