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 (δ¹³C and δ¹⁵N) 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 (C₂₇, C₂₉, C₃₁, and C₃₃), characteristic of terrestrial OC, dominated all types of sediment deposition but were 4 times more abundant in flood layers. Marine algae (C₁₅, C₁₇, and C₁₉) and macrophytes (C₂₁ and C₂₃) 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.

中文翻译：

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在过去的2,000年中，加利福尼亚州圣塔芭芭拉盆地的洪水，干旱和浊度对有机碳埋藏的影响

气候条件和瞬时沉积事件会影响陆地和海洋环境中沉积物的相对贡献，最终影响到沉积物中记录的碳的数量和组成。在这里，我们分析了海洋沉积物的元素，同位素和有机地球化学成分，以确定过去2,000年间与加利福尼亚州圣塔芭芭拉盆地（SBB）的干旱，浑浊和洪水相关的沉积物层中的陆地和海洋资源。稳定同位素（δ ¹³ C和δ ¹⁵ N）指示多个陆地有机碳（OC）相对于背景的沉积物在洪水期间沉积，而散装℃至氮（C / N）比保持相对恒定（〜10）。长链正构烷烃（C₂₇，C ₂₉，C ₃₁和C ₃₃）是陆地OC的特征，在所有类型的沉积物中都占主导地位，但在洪水层中的含量要高4倍。洪水中的海藻（C ₁₅，C ₁₇和C ₁₉）和大型植物（C ₂₁和C ₂₃）也比背景沉积物高2倍。相对于本底沉积物，浊质岩中的陆地正构烷烃含量是其两倍。相反，干旱区间分别通过其较高的海藻的比例仅从背景泥沙区分ñ烷烃。综合起来，我们的数据表明，在过去2,000年中，SBB埋藏的总OC中有15％是在11次洪水事件中沉积的，这些沉积物主要是陆生的，另外12％的深层沉积物OC埋藏是在6个时期的架子移动中获得的。浊度事件。相对于20世纪的河流径流，我们的数据表明，洪水导致加利福尼亚大陆边缘的大量地面OC埋葬。