Moisture and Seasonality Shifts Recorded in Holocene and Pleistocene Speleothems From Southeastern Arabia

• Published in: Geophysical research letters 2022-08, Vol.49 (16), p.n/a
• Main Authors: Fleitmann, D., Burns, S. J., Matter, A., Cheng, H., Affolter, S.
• Format: Article
• Language: English
• Subjects: Analytical methods; Chemical composition; Climate change; Coastal waters; Coastal zone; Coasts; Composition; Fluid inclusions; Fossils; Holocene; Hydrogen; Indian monsoon; Inland waters; Interglacial periods; Intervals; Isotope composition; Isotopes; Lacustrine sedimentation; Lacustrine sediments; Lake deposits; Lake sediments; Lakes; Moisture; Moisture effects; moisture source; Monsoons; Oman; Oxygen; Oxygen isotopes; Paleoprecipitation; Pleistocene; Precipitation; Quaternary; Rain; Rain water; Rainfall; Rainfall amount; Rainfall regime; Seasonal variations; Seasonality; Sediment; Sediment deposits; Sediments; speleothems; stable isotopes; Summer; Wetlands; Wind; Winter
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2021GL097255

The source and seasonality of rainfall in southern Arabia during the early‐ to mid‐Holocene and preceding humid periods are controversial because fossil lacustrine sediments provide solely indirect information on the amount of rainfall. Hydrogen and oxygen isotope measurements on fluid inclusion water trapped in Holocene and Pleistocene stalagmites from Hoti Cave in Northern Oman are direct indicators of the isotopic composition of paleoprecipitation. Isotope values of fluid inclusions formed during peak interglacial periods plot along monsoonal water lines and are indicative of a southern monsoonal moisture source. The last monsoon‐dominated period lasting from ∼10,100 to 6,300 years before present was terminated within a few decades in southeastern Arabia. The subsequent reduction in rainfall amount and change from predominantly summer to predominantly winter rainfall had a profound impact on human communities living in this area and triggered migration from inland to coastal areas where resources were more abundant. Plain Language Summary During the Quaternary period, the Arabian Peninsula experienced short intervals of enhanced rainfall, turning the Arabian Desert into a savannah‐type landscape with abundant lakes and wetlands. These intervals are well‐documented in lake sediments and cave deposits throughout Arabia, whereas the source of rainfall is uncertain. Ancient rainwater trapped in fluid inclusions in stalagmites from Hoti Cave, Northern Oman, allows us to determine moisture source changes over the last 350,000 years before present. Using new analytical methods to extract the water from fluid inclusions and measure its hydrogen and oxygen isotopic composition, we are able to show that greatly enhanced rainfall was caused by an intensification and greater northward extension of the African and Indian monsoons into Arabia. For the last humid period between ∼10,500 and 6,300 years before present, stalagmites from Hoti Cave reveal an abrupt termination of the monsoon‐dominated period, a sharp decline in precipitation and change from a summer‐ to winter‐dominated rainfall regime in southeastern Arabia. As a result, human communities were severely affected by this major climatic change and forced to migrate from inland to coastal areas, where water and resources were more abundant. Key Points Hydrogen and oxygen isotopes in fluid inclusions in stalagmites from Hoti Cave, Northern Oman, reveal changes in the source of rainfall Rainfall during the earl