Quaternary record of terrestrial environmental change in response to climatic forcing and anthropogenic perturbations, in Puerto Rico
Quaternary record of terrestrial environmental change in response to climatic forcing and anthropogenic perturbations, in Puerto Rico
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DOI：
10.1016/j.quascirev.2020.106770
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发表时间：
2021-02
影响因子：
4
通讯作者：
E. Harrison;J. Willenbring;G. Brocard
中科院分区：
文献类型：
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作者：
E. Harrison;J. Willenbring;G. Brocard
我们展示了波多黎各东北部 Rio Fajardo 流域过去约 25 公里内生物和非生物陆地过程的空间当代档案记录。代理记录源自切岸切口暴露的 5 米厚的地层剖面。我们通过沉积有机物质的稳定碳同位素比与当代碳源的 δ 13 C 比的变化来解释生态系统动态。沉积有机物质的δ 13 C 值范围为- 29.715 至- 15.291。我们根据洪泛区沉积物层中大气 10 Be 的浓度得出了流域古侵蚀速率的记录。古侵蚀率范围为 13 至 356 mm ky−1。沉积物的年代学受到有机沉积物放射性碳年龄的限制，最古老的年龄被校准为～ 22.4 ky BP（距今数千年），并在 440 cm 深度检索。我们收集了粒度数据、粘土矿物学，并分析了地球化学指数，包括化学风化指数、盐化和碱阳离子损失剖面。该地层序列记录了加勒比气候的重大变化、厄尔尼诺-南方涛动的加剧以及人类抵达该岛的情况。在末次冰期和全新世早期，生物（δ 13 C）和非生物指标（10 Be met 和地球化学数据）都表明与气候的动态平衡。过去五千年（ky）的记录的特点是对两个系统中的扰动的脉冲响应。殖民时代的土地利用带来的变化远远超过了记录期间任何替代物的自然变化。
We present cospatial, contemporary archival records of biotic and abiotic terrestrial processes operating over the past∼ 25 ky within the Rio Fajardo watershed, in northeastern Puerto Rico. The proxy records were derived from a 5-m-thick stratigraphic section exposed by cut bank incision. We interpreted ecosystem dynamics from changes in the stable carbon isotopic ratio of sedimentary organic material compared to δ 13 C ratios of contemporary carbon sources. Sedimentary organic material had δ 13 C values ranging from− 29.715 to− 15.291. We derived a record of paleo-erosion rates in the catchment from the concentration of meteoric 10 Be in layers of the floodplain sediments. Paleo-erosion rates ranged from 13 to 356 mm ky− 1. The chronology of the sediments was constrained with the radiocarbon ages of organic deposits, the oldest age was calibrated to∼ 22.4 ky BP (thousand years before present) and retrieved at 440 cm depth. We collected grain size data, clay mineralogies, and analyzed geochemical indices including the chemical weathering index, salinization, and base cation loss down profile. This stratigraphic sequence captures major shifts in the Caribbean climate, the intensification of the El Nino-Southern Oscillation, and the arrival of humans on the island. During the last glacial and early Holocene epochs both biotic (δ 13 C) and abiotic proxies (10 Be met and geochemical data) indicated dynamic equilibrium with climate. The past five thousand years (ky) of record are characterized instead by pulsed responses to disturbances in both systems. Colonial-era land use drove changes that significantly exceeded natural variability in any proxy over the period of record.