Assessing environmental change associated with early Eocene hyperthermals in the Atlantic Coastal Plain, USA
Assessing environmental change associated with early Eocene hyperthermals in the Atlantic Coastal Plain, USA
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DOI：
10.5194/cp-19-1677-2023
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发表时间：
2023-08
影响因子：
4.3
通讯作者：
W. Rush;J. Self‐Trail;Yang Zhang;A. Sluijs;H. Brinkhuis;J. Zachos;J. Ogg;M. Robinson
中科院分区：
文献类型：
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作者：
W. Rush;J. Self‐Trail;Yang Zhang;A. Sluijs;H. Brinkhuis;J. Zachos;J. Ogg;M. Robinson
抽象的。始新世短暂的全球变暖事件（高温）可以提供对未来变暖世界的洞察力。虽然许多研究都集中在古新世-始新世热最大值（PETM），但较小幅度的高温可以用来表征不同强迫幅度的气候响应。本研究确定了两个事件，即始新世热最大值2（ETM 2和H2），在浅海相沉积物的始新世年龄的索尔兹伯里湾的马里兰州，基于磁性地层学，钙质超微化石，和dinocyst生物地层学，以及负稳定碳同位素偏移（CIE）的认识，在生物方解石。利用粘土矿物学、海洋孢粉学、生物成因方解石的δ 18 O和生物标志物古温度测定法（TEX 86），我们评估了索尔兹伯里湾的局部环境变化。古水温代用指标表明，表层水温和底层水温变化之间存在广泛的一致性。然而，变暖的时间并不对应于从其他记录预期的ETM 2的CIE，并在H2期间观察到最高值，这表明除了pCO 2强迫的因素影响了该地区的温度变化。ETM 2区间的粘土矿物学表现出从蒙皂石为主的相转变为伊利石丰富的相，这表明水文气候变化，但相对于同一地区的PETM，风化反应相当减弱。有机壁甲藻孢囊组合在整个研究剖面中表现出较大的波动，但似乎都与CIE变暖没有系统性关系。这些观察结果与PETM，区域和全球以及北冰洋ETM 2之间气候变化和组合之间典型的紧密对应关系相反。这些数据确实表明H2上非常温暖和（季节性）分层的条件，可能是盐度驱动的。与PETM相比，ETM 2和H2期间当地水文和养分供应缺乏强烈扰动的证据，这与极端强迫和事件前基线的温暖以及水文气候对温室强迫的非线性响应是一致的。
Abstract. Eocene transient global warming events (hyperthermals) can provide insight into a future warmer world. While much research has focused on the Paleocene–Eocene Thermal Maximum (PETM), hyperthermals of a smaller magnitude can be used to characterize climatic responses over different magnitudes of forcing. This study identifies two events, namely the Eocene Thermal Maximum 2 (ETM2 and H2), in shallow marine sediments of the Eocene-aged Salisbury Embayment of Maryland, based on magnetostratigraphy, calcareous nannofossil, and dinocyst biostratigraphy, as well as the recognition of negative stable carbon isotope excursions (CIEs) in biogenic calcite. We assess local environmental change in the Salisbury Embayment, utilizing clay mineralogy, marine palynology, δ18O of biogenic calcite, and biomarker paleothermometry (TEX86). Paleotemperature proxies show broad agreement between surface water and bottom water temperature changes. However, the timing of the warming does not correspond to the CIE of the ETM2 as expected from other records, and the highest values are observed during H2, suggesting factors in addition to pCO2 forcing have influenced temperature changes in the region. The ETM2 interval exhibits a shift in clay mineralogy from smectite-dominated facies to illite-rich facies, suggesting hydroclimatic changes but with a rather dampened weathering response relative to that of the PETM in the same region. Organic walled dinoflagellate cyst assemblages show large fluctuations throughout the studied section, none of which seem systematically related to CIE warming. These observations are contrary to the typical tight correspondence between climate change and assemblages across the PETM, regionally and globally, and ETM2 in the Arctic Ocean. The data do indicate very warm and (seasonally) stratified conditions, likely salinity-driven, across H2. The absence of evidence for strong perturbations in local hydrology and nutrient supply during ETM2 and H2, compared to the PETM, is consistent with the less extreme forcing and the warmer pre-event baseline, as well as the non-linear response in hydroclimates to greenhouse forcing.