Major sea-level cycles occurred in the Cenomanian-early Turonian greenhouse world and impacted depositional conditions and ecosystems across the paleo-shelf seas. These sea-level cycles have been interpreted from various paleogeographic settings around the globe, such as the Western Interior Seaway (North America), the Proto-North Atlantic, Western Europe, and eastern Tethys (SE India). However, their drivers remain poorly understood and may include glacio-, aquifer-, thermo-, and/or tectono-eustasy. Uncertainties also persist regarding the timing, synchronicity, and magnitude of Cenomanian-early Turonian eustatic cycles. By combining palynological data from northern Africa (Gindi Basin, Egypt) with data available in the literature, a detailed synthesis of Cenomanian palynostratigraphy and sea-level dynamics is presented. Age-diagnostic spores, pollen, and organic walled dinoflagellate cysts (dinocysts) are correlated to global marine biozonation schemes, which provide a comprehensive biostratigraphic framework for the Cenomanian-early Turonian. Additionally, palynological data enable the identification of an early late Cenomanian bio-event marked by the highest abundances of dinocysts. This bio-event can be correlated to the ammonite bio-event and the Jukes-Browne Carbon Isotope Event. The bio-events stratigraphically constrain with a major transgression, which occurred in the early late Cenomanian, slightly preceding Oceanic Anoxic Event 2 (OAE2). Another major transgression spans the late Cenomanian-early Turonian, referred to the Plenus transgression bio-event, and consistent with the onset of the OAE2. Regional to global correlations indicate that these transgressive events reflect eustatic sea-level rises that can be recognized throughout the Tethys, Proto-North Atlantic, Europe, Western Interior Seaway, and India. These transgressions occurred within <1.0 Myr with modest magnitudes of 10–60 m. Rates of sea-level change has commonly been attributed to glacio-eustasy, which is however difficult to reconcile with a probably ice-free Cenomanian-early Turonian greenhouse world. Both transgressions coincide with phases of rising temperatures, whereby warming was most pronounced during the early late Cenomanian transgression. However, we can only speculate whether rising temperatures indicate the demise of polar glaciations. Eustatic processes, including tectono-eustasy, and to some extent aquifer- and thermo-eustasy, likely played a role in the sea-level rise during the early late Cenomanian and early Turonian. Environmental changes associated with the early late Cenomanian transgression may have triggered the onset of OAE2 possibly exacerbated by sluggish ocean circulation in a warming greenhouse world where sea ice formation was limited.

中文翻译：

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塞诺曼阶-土伦阶早期海平面演化及相关动态的区域与全球相关性：新视角


主要的海平面循环发生在塞诺曼阶-土伦阶早期的温室世界，影响了整个古陆架海洋的沉积条件和生态系统。这些海平面循环是根据全球不同的古地理环境来解释的，例如西部内陆海道（北美）、原始北大西洋、西欧和东特提斯（印度东南部）。然而，它们的驱动因素仍然知之甚少，可能包括冰川、含水层、热和/或构造海平面。塞诺曼阶-土伦早期海平面上升周期的时间、同步性和幅度也存在不确定性。通过将北非（埃及金迪盆地）的孢粉学数据与文献中可用的数据相结合，提出了塞诺曼期孢粉地层学和海平面动态的详细综合。年龄诊断孢子、花粉和有机壁甲藻包囊（甲藻）与全球海洋生物区划方案相关，为塞诺曼阶-早期土兰阶提供了全面的生物地层框架。此外，孢粉学数据能够识别早期晚期塞诺曼阶生物事件，该事件以最高丰度的恐龙囊为标志。该生物事件可以与菊石生物事件和朱克斯-布朗碳同位素事件相关。这些生物事件在地层上受到重大海侵的影响，该海侵发生在塞诺曼纪晚期早期，略早于海洋缺氧事件 2 (OAE2)。另一次重大海侵跨越塞诺曼阶晚期至土伦阶早期，称为普莱纳斯海侵生物事件，与 OAE2 的爆发一致。 区域与全球的相关性表明，这些海侵事件反映了海平面的上升，这种上升在整个特提斯海、原始北大西洋、欧洲、西部内陆航道和印度都可以看到。这些海侵发生在 <1.0 Myr 范围内，程度适中，为 10-60 m。海平面变化率通常归因于冰川平衡，然而，这很难与可能无冰的塞诺曼阶-土伦阶早期温室世界相协调。两次海侵都与气温上升的阶段同时发生，其中在塞诺曼阶海侵早期晚期期间变暖最为明显。然而，我们只能推测气温上升是否表明极地冰川消亡。海平面上升过程，包括构造海平面上升，以及某种程度上的含水层和热海平面上升，可能在塞诺曼纪晚期和图伦早期海平面上升中发挥了作用。与塞诺曼纪晚期海侵相关的环境变化可能引发了 OAE2 的发生，而在海冰形成有限的变暖温室世界中，海洋环流缓慢可能会加剧 OAE2 的发生。