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Isotopic composition of gypsum hydration water in deep Core SG-1, western Qaidam basin (NE Tibetan Plateau), implications for paleoclimatic evolution.
- Source :
-
Global & Planetary Change . Aug2017, Vol. 155, p70-77. 8p. - Publication Year :
- 2017
-
Abstract
- The oxygen and hydrogen isotopic compositions of gypsum hydration water can be useful for determining the isotopic composition of the original brine from which gypsum precipitated. However, relatively few long-term and continuous records of the stable isotope geochemistry of gypsum hydration water in arid regions have been reported. We measured the δ 18 O and δD of primary gypsum hydration water from a 938.5 m-long deep core (SG-1) in the western Qaidam Basin to study the mechanisms that contributed to gypsum formation and to reconstruct potential paleoclimatic change. The measured δ 18 O and δD ranged from − 4.21‰ to 8.69‰ and from − 72.77‰ to 49.73‰, respectively. The linear relationship between δ 18 O and δD indicates that meteoric water was the original source of the gypsum hydration water. The gradient of 5.39 for the δ 18 O and δD plots is lower than that of global meteoric water, suggesting that paleo-lakewater evaporated and became a CaSO 4 -rich brine leading to gypsum deposition. The evaporation/precipitation (E/P) ratio played an important role in determining δ 18 O and δD. The oscillations noted in the δ 18 O and δD of the gypsum hydration water imply that: (a) there was a long-term and stepwise aridification after ~ 2.2 Ma in the western Qaidam Basin; and (b) there were three increasingly dry phases at 2.2–1.2 Ma, 1.2–0.6 Ma, and 0.6–0.1 Ma, with two cold and dry events at ~ 1 Ma and ~ 0.6 Ma. Global cooling, especially during the Mid Pleistocene Climate Transition event (MPT), may have been the primary cause of the aridification recorded in core SG-1 in the Asian inland. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 09218181
- Volume :
- 155
- Database :
- Academic Search Index
- Journal :
- Global & Planetary Change
- Publication Type :
- Academic Journal
- Accession number :
- 124510645
- Full Text :
- https://doi.org/10.1016/j.gloplacha.2017.06.006