Radiocarbon and stable isotope evidence of early to mid‐Holocene wet events from fluvial tufa deposits in Santa Cruz, CA
Radiocarbon and stable isotope evidence of early to mid‐Holocene wet events from fluvial tufa deposits in Santa Cruz, CA
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DOI：
10.1002/jqs.3450
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发表时间：
2022-07
影响因子：
2.3
通讯作者：
Maura C. Kanner;L. Cortés;Y. Ibarra
中科院分区：
文献类型：
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作者：
Maura C. Kanner;L. Cortés;Y. Ibarra
记录易发生干旱地区过去的水文变化记录越来越重要，以便更好地预测该地区未来的补给和供水脆弱性。全新世泉水相关的碳酸盐沉积物作为水平衡的陆地记录，可以补充其他对湿度敏感的局部高分辨率代理。在这里，我们研究了由常温淡水泉形成的两个碳酸盐沉积物（一个不活跃的栖息凝灰岩地点和一个活跃的河流凝灰岩地点），作为其沉积条件的代表。对来自不活动的栖息凝灰岩的木炭碎片进行的放射性碳 (14C) 分析记录沉积年龄为 6.2 ± 0.06 (2σ) cal ka bp 和 8.0 ± 0.04 (2σ) cal ka bp，并与该地区过去洪流期其他代理的年龄模型一致（~16 至 5 ka）。活跃的河流凝灰岩可追溯到 853 ± 0.4 cal bp，代表与现代水流类似的条件。地貌和放射性碳结果表明，栖息的凝灰岩反映了较高地下水位滋养的湿润条件。碳酸盐的稳定同位素分析（δ13C、δ18O）揭示了现代和早中期全新世凝灰岩之间不同的同位素值。这项工作强调了分析加州中部沿海其他对湿度敏感的凝华沉积物的潜力。
It is increasingly important to document past records of hydrologic change in areas that are drought‐prone to better predict the region's future vulnerability to recharge and water supply. Holocene spring‐associated carbonate deposits serve as terrestrial records of water balance that can complement other local, high‐resolution proxies that are moisture‐sensitive. Here we examine two carbonate deposits (one inactive perched tufa site and one active fluvial tufa site) that form from ambient‐temperature freshwater springs, as proxies of their depositional conditions. Radiocarbon (14C) analyses of charcoal fragments from the inactive perched tufa record depositional ages of 6.2 ± 0.06 (2σ) cal ka bp and 8.0 ± 0.04 (2σ) cal ka bp and agree with the age models from other proxies of past pluvial periods in the region (~16 to 5 ka). The active fluvial tufas date to 853 ± 0.4 cal bp, representing conditions similar to modern flow. Geomorphologic and radiocarbon results indicate the perched tufa reflects wetter conditions fed by a higher water table. Stable isotopic analyses of carbonate (δ13C, δ18O) reveal distinct isotopic values between modern and early–mid‐Holocene tufa. This work underscores potential for the analysis of other moisture‐sensitive tufa deposits in coastal central California.