Isotopic and geochemical evidence of palaeoclimate changes in Salton Basin, California, during the past 20 kyr: 1. delta O-18 and delta C-13 records in lake tufa deposits

• Published in: Palaeogeography, Palaeoclimatology, Palaeoecology
• Main Authors: Li, Hong-Chun, Xu, Xiao-Mei, Ku, Teh-Lung, You, Chen-Feng, Buchheim, H. Paul, Peters, Rick
• Other Authors: Department of Earth Sciences
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2008
• Subjects: stable isotopes; AMS C-14; lake tufa; Salton Basin; Lake Cahuilla; north American monsoon; Basin Lake; Greenland; Greenland ice core; ice core
• Online Access: https://doi.org/10.1016/j.palaeo.2007.10.006; http://ir.lib.ncku.edu.tw/handle/987654321/86786

Investigation of 6180 and salt content of surface waters in the Salton Basin, California, shows that there is a strongly positive correlation between 6180 values and salt contents and that the 6180 of Salton Sea is much heavier than that of its input waters due to strong evaporation. Using a steady-state 6180 model, we have discussed the 6180 of Lake Cahuilla, an ancient lake in the basin, under through-flowed, closed and overflowed situations. An AMS-C-14-dated stable-isotope record of a 60-cm lake tufa slice (LC-1) from the ancient shoreline of Lake Cahuilla indicates that the lake experienced closed and/or overflowed conditions between 1,300 and 20,500 yr BP. The variations in 618 0 and delta C-13 values of LC-1 ranging from -8.52 parts per thousand to -2.50 parts per thousand (PDB) and from 0.8 parts per thousand to 3.76 parts per thousand, respectively, reflect changes in the relative humidity in Salton Basin and variations in the Colorado River inflow and hence climatic conditions in the Colorado River drainage basin. The tufa record exhibits palaeoclimates of Salton Basin as follows. (1) Relatively dry climate between 20 and 18 kyr BP was followed by a wet climate between 18 and 17 kyr BP. (2) Decreasing effective moisture (precipitation-evaporation) from 17 to 16 kyr BP corresponded to Heinrich-1 event, whereas effective moisture increased at ca.15.5 kyr BP during the Trans-US Wet Period. Contrasting patterns between the LC-1 record and the Greenland ice-core and Chinese speleothem records during the Bolling-Allerod interstadial from 15.2 to 11.7 kyr BP may be caused by age uncertainty of the LC-1 record. Further study of this interval is needed. (3) Wet/warm early Holocene corresponding to the Maximum Effective Moisture Period perhaps brought about by the strengthening of North American monsoon. (4) Toward 2 kyr BP, the climate became dryer, apparently resulting from weakening of the monsoons, especially around 6.2 and 2.5 kyr BP. (5) A wet regime occurred in the basin during the Medieval Warm Period. (c) 2007 Elsevier B.V. All rights reserved.