Snapshots of Coastal Ecology Using Multiproxy Analysis Reveals Insights Into the Preservation of Swamp and Marsh Environments Since the Late Pleistocene
Kendall Fontenot, Kristine L. DeLong, Brian A. Schubert, Sophie Warny, Davin J. Wallace, Carrie M. Miller, Erin Culver-Miller, Michael J. Polito, Carl A. Reese, Kathryn Garretson, Kehui Xu, Grant L. Harley, Jeffrey Obelcz, Kelli L. Moran, Julian Traphagan, Douglas Jones, Alicia Caporaso
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引用次数: 0
Abstract
The southeastern United States Coastal Plain ecosystem contains baldcypress (Taxodium distichum) swamps and grass-dominated marshes. These ecosystems also occurred on the exposed continental shelf during lower sea levels but are rarely preserved due to the mechanically erosive nature of transgression and regression. Two presently marine sites on the northeastern Gulf of Mexico's continental shelf contain well-preserved woody terrestrial sediments that were the subject of previous studies. This study continues the investigation using geochemical (δ13C, δ15N, δ34S) and palynological characteristics of these formerly terrestrial sediments to determine if swamps and/or marshes existed at the time of deposition. The first site is located ∼20 km southeast of Horn Island, Mississippi (MS) and the core has terrestrial sediments radiocarbon dated to 11,066–10,228 (2σ) calibrated years BP (early Holocene). The second site is the “Alabama Underwater Forest” located ∼13 km south of Gulf Shores, Alabama (AL) and the cores have terrestrial sediments optically stimulated luminescence dated to 63 ka (±10 ka, 2σ) to 72 ka (±16 ka, 2σ) (late Pleistocene). Geochemical results for the MS sediments indicate a swamp-to-freshwater marsh transitional series, whereas the AL sediments indicate a swamp-to-saltwater marsh transitional series, both supported by palynological results. Further exploration of the geochemical results using linear discriminant analysis, trained with published geochemical data, supports the swamp and marsh interpretations. We conclude that the near-pristine preservation of these woody deposits is not solely due to physical mechanisms, such as rapid burial, but is also coupled with anoxia- and euxinia-driven biogeochemical reactions promoting wood and woody debris preservation in swamp and marsh environments.
美国东南部沿海平原生态系统包括秃杉(Taxodium distichum)沼泽和以草为主的沼泽。在海平面较低时,这些生态系统也曾出现在裸露的大陆架上,但由于横断和回归的机械侵蚀性质,这些生态系统很少被保存下来。目前,墨西哥湾东北部大陆架上的两个海洋遗址含有保存完好的木质陆地沉积物,这些沉积物是之前研究的主题。本研究利用这些原陆地沉积物的地球化学特征(δ13C、δ15N、δ34S)和古生物学特征继续进行调查,以确定沉积时是否存在沼泽和/或沼泽。第一个地点位于密西西比州霍恩岛东南 20 公里处,岩芯中的陆地沉积物的放射性碳年代为公元前 11,066-10,228 (2σ) 年(全新世早期)。第二个地点是 "阿拉巴马水下森林",位于阿拉巴马州(AL)湾岸以南 13 千米处,岩芯中陆地沉积物的光激发发光年代为 63 ka (±10 ka, 2σ) 至 72 ka (±16 ka, 2σ) (晚更新世)。MS 沉积物的地球化学结果表明是沼泽向淡水沼泽的过渡系列,而 AL 沉积物则表明是沼泽向咸水沼泽的过渡系列,两者都得到了古生物学结果的支持。根据已公布的地球化学数据,使用线性判别分析对地球化学结果进行了进一步探讨,结果支持沼泽和沼泽的解释。我们得出的结论是,这些木质沉积物近乎原始的保存并不完全是物理机制(如快速掩埋)造成的,还与缺氧和缺氧驱动的生物地球化学反应有关,这些反应促进了木材和木质碎屑在沼泽和沼泽环境中的保存。
期刊介绍:
Geochemistry, Geophysics, Geosystems (G3) publishes research papers on Earth and planetary processes with a focus on understanding the Earth as a system. Observational, experimental, and theoretical investigations of the solid Earth, hydrosphere, atmosphere, biosphere, and solar system at all spatial and temporal scales are welcome. Articles should be of broad interest, and interdisciplinary approaches are encouraged.
Areas of interest for this peer-reviewed journal include, but are not limited to:
The physics and chemistry of the Earth, including its structure, composition, physical properties, dynamics, and evolution
Principles and applications of geochemical proxies to studies of Earth history
The physical properties, composition, and temporal evolution of the Earth''s major reservoirs and the coupling between them
The dynamics of geochemical and biogeochemical cycles at all spatial and temporal scales
Physical and cosmochemical constraints on the composition, origin, and evolution of the Earth and other terrestrial planets
The chemistry and physics of solar system materials that are relevant to the formation, evolution, and current state of the Earth and the planets
Advances in modeling, observation, and experimentation that are of widespread interest in the geosciences.