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The Impacts of Flood, Drought, and Turbidites on Organic Carbon Burial Over the Past 2,000 years in the Santa Barbara Basin, California
Author(s) -
Sarno Caitlyn T.,
BenitezNelson Claudia R.,
Ziolkowski Lori A.,
Hendy Ingrid L.,
Davis Catherine V.,
Tappa Eric J.,
Thunell Robert C.
Publication year - 2020
Publication title -
paleoceanography and paleoclimatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.927
H-Index - 127
eISSN - 2572-4525
pISSN - 2572-4517
DOI - 10.1029/2020pa003849
Subject(s) - sediment , turbidite , geology , total organic carbon , terrestrial plant , sedimentary depositional environment , surface runoff , deposition (geology) , macrophyte , flood myth , structural basin , environmental science , hydrology (agriculture) , oceanography , environmental chemistry , geomorphology , ecology , geography , chemistry , geotechnical engineering , archaeology , biology
Climate conditions and instantaneous depositional events can influence the relative contribution of sediments from terrestrial and marine environments and ultimately the quantity and composition of carbon buried in the sediment record. Here, we analyze the elemental, isotopic, and organic geochemical composition of marine sediments to identify terrestrial and marine sources in sediment horizons associated with droughts, turbidites, and floods in the Santa Barbara Basin (SBB), California, during the last 2,000 years. Stable isotopes (δ 13 C and δ 15 N) indicate that more terrestrial organic carbon (OC) was deposited during floods relative to background sediment, while bulk C to nitrogen (C/N) ratios remained relatively constant (~10). Long‐chain n ‐alkanes (C 27 , C 29 , C 31 , and C 33 ), characteristic of terrestrial OC, dominated all types of sediment deposition but were 4 times more abundant in flood layers. Marine algae (C 15 , C 17 , and C 19 ) and macrophytes (C 21 and C 23 ) were also 2 times higher in flood versus background sediments. Turbidites contained twice the terrestrial n ‐alkanes relative to background sediment. Conversely, drought intervals were only distinguishable from background sediment by their higher proportion of marine algal n ‐alkanes. Combined, our data indicate that 15% of the total OC buried in SBB over the past 2,000 years was deposited during 11 flood events where the sediment was mostly terrestrially derived, and another 12% of deep sediment OC burial was derived from shelf remobilization during six turbidite events. Relative to twentieth century river runoff, our data suggest that floods result in considerable terrestrial OC burial on the continental margins of California.