A 2,000 year Record of Biomarker Identification in Santa Barbara Basin, California Flood Sediments
Abstract
Sediments provide information about the source, magnitude and composition of buried organic carbon (OC). Within Southern California, the Santa Barbara Basin (SBB) provides an optimal environment for paleoenvironmental reconstructions due to its suboxic bottom waters and high sedimentation rate. Presently, the impacts of flooding and terrestrial input to marine sediments in this region have been overlooked. Here we present a biomarker analysis from a well-dated SBB sediment core that spans the last 2,000 years (SPR0901-03KC; 34°16.99'N, 120°2.41'W; 586 m depth) to determine the relative contributions of terrestrial versus marine sources to basin sediments over time. Bulk sediment elemental analysis (e.g., Ti, Fe, and Ca) was used to identify drought conditions and flood layers. Bulk sediment C:N ratios (< 10) suggest that the sediments associated with flood layers are marine in origin, however, isotopic analyses, δ15N (< 6 ‰) and δ13C (< -24 ‰), indicate significant terrestrial OC input during flooding.
To elucidate sediment sources to SBB during flood events, n-alkane lipids analyses were conducted to partition terrestrial (longer n-alkane chain length) from marine sources (shorter n-alkane chain length). Flood sediments had higher n-alkane abundances relative to non-flood sediments. During floods there was significantly more terrestrial material (C27, C29, C31, C33) and to a lesser extent, increased marine algae (C15, C17, C19) and macrophytes (C21, C23, C25) delivered to the sediments. This n-alkane results supports our isotopic data, in that a significant input of fresh OC from terrestrial sources entered the basin during flood events. Although relatively small in contribution to OC burial, macrophytes and marine algae also contribute to flood sediments via kelp forest destruction along the coastline and increased nutrient concentrations during enhanced river discharge. This study demonstrates that flood events have the potential to transport and bury significant quantities of terrestrial OC to the ocean as well as to disrupt and destruct coastal ecosystems.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B52B..08S
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0428 Carbon cycling;
- BIOGEOSCIENCESDE: 1635 Oceans;
- GLOBAL CHANGEDE: 3022 Marine sediments: processes and transport;
- MARINE GEOLOGY AND GEOPHYSICS