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This content will become publicly available on September 29, 2018

Title: Bottom-water oxygenation and environmental change in Santa Monica Basin, southern California during the last 22 kyr

The Southern California Borderland (SCB) is a region that experiences strong natural variations in bottom water oxygen and pH. Here, we use marine sediments from the Santa Monica Basin (SMB) to reconstruct environmental conditions and changes in the basin's bottom water oxygenation from the Last Glacial Maximum (LGM) to present, and compare the records to the adjacent Santa Barbara Basin (SBB) and Santa Lucia Slope (SLS). High-resolution records of benthic foraminiferal oxygen and carbon isotopes (δ 18O and δ 13C), benthic foraminiferal assemblages, and bulk sedimentary organic matter geochemistry records exhibit major changes associated with late Quaternary millennial-scale global climate oscillations. Our data show the dominance of low-oxygen benthic foraminifera assemblages during warm intervals, and assemblages representing higher dissolved oxygen during cooler intervals, as also seen in SBB and SLS. But, our record shows a stronger and longer-lasting oxygen minimum zone (OMZ) between the end of the Bølling-Allerød (B-A) and the Early Holocene (including the Younger Dryas) than at neighboring sites, indicated by dominance of Bolivina tumida (characteristic of major hypoxia) in the assemblage. The middle to late Holocene (from ~ 8.8 to 0 ka) had weaker hypoxia than the early Holocene, with assemblages mainly composed of Bolivina argentea andmore » Uvigerina peregrina. The SMB remains mostly slightly low in oxygen throughout the studied interval, with differences in the degree of hypoxia relative to SBB and SLS (especially from the B-A to the Early Holocene) likely due to its greater depth and its more southern geographic position and therefore decreased exposure to North Pacific Intermediate Water current. Regional effects, such as changing intermediate water source and/or changing ventilation (oxygenation) of the intermediate water source, also affect SMB deep water. Our analysis utilizing parallel geochemical and micropaleontological records brings new insights into bottom water and climate conditions in SMB, indicating regional similarities and differences with adjacent basins, and provides insight into the causes for changes in bottom water oxygenation.« less
Authors:
 [1] ;  [2] ;  [1] ; ORCiD logo [3] ;  [3] ;  [1]
  1. Univ. of California, Santa Cruz, CA (United States). Inst. of Marine Science
  2. Univ. of California, Santa Cruz, CA (United States). Inst. of Marine Science; Lund Univ. (Sweden). Dept. of Geology
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Report Number(s):
LA-UR-17-28251
Journal ID: ISSN 0031-0182
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Palaeogeography, Palaeoclimatology, Palaeoecology
Additional Journal Information:
Journal Volume: 490; Journal ID: ISSN 0031-0182
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; benthic foraminifera; santa monica basin; last 22 kyr; oxygen and carbon isotope records; organic matter geochemistry
OSTI Identifier:
1398937