Sequence stratigraphy of a wave-dominated, tidally influenced delta in the Danian of Seymour Island, Antarctica: An integrated sedimentological-palaeoecological approach
Sequence stratigraphy of a wave-dominated, tidally influenced delta in the Danian of Seymour Island, Antarctica: An integrated sedimentological-palaeoecological approach
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南极洲西摩岛达尼安期波浪主导、潮汐影响三角洲的层序地层学：综合沉积学-古生态学方法
DOI：
10.1016/j.palaeo.2023.111789
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发表时间：
2023
期刊：
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通讯作者：
Ineson J
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作者：
Ineson J
下古新统索布拉尔组（Seymour Island，Antarctica）的海相硅质碎屑岩是南部高纬度Maastrichtian-Eocene基准剖面的重要组成部分。该地层包括一个向上变粗的海退序列（270 m厚），从前三角洲、富泥到桑迪近岸沉积物变浅。沉积相分析，结合大型动物群和microflora古生态研究，表明波浪为主，潮汐影响的三角洲环境。4个沉积层序（1-4）记录了相对海平面变化对体系逐步扩展的控制作用。前三角洲和远三角洲前缘沉积物（层序1、2）包括富含泥质杂岩和生物扰动细粒泥质砂的向上变粗准层序，显示出披覆的滑塌疤痕。上覆侵蚀层序边界以充满河流-河口沉积物的下切河谷为标志;随后的富砂相（层序3、4）代表近端三角洲前缘和三角洲台地。宏观无脊椎动物和孢粉数据集显示形成的回归历史的对比反应。在远三角洲沉积物中的大型底栖动物记录反映了海洋的影响，虽然地层的多样性增加控制的生态因素和生物恢复后的K-Pg事件。相关的孢粉组合也显示出强烈的海洋信号，包括典型的外浅海-大洋沟鞭藻孢囊类群。序列3、4中宏体化石多样性和丰度的急剧下降与浅水、限制性近岸环境中的生态压力是相容的。虽然这一层的孢粉学记录以陆源为主，但海洋成分反映了甲藻的世界性，显示了该层中最高的多样性。回归索布拉尔形成结束了一个protractedc.60百万年的区域沉降和海洋沉积的历史，虽然放大了两个可能的海平面升降的起源，丹尼海平面下降福尔斯，回归趋势预示着中古新世盆地反转可能与区域构造重组的开始，最终导致开放的斯科舍海。
Lower Paleocene marine siliciclastics of the Sobral Formation (Seymour Island, Antarctica) form an important component of a key southern high latitude reference section for the Maastrichtian–Eocene. The formation comprises a coarsening-upward, regressive succession (270 m thick), shallowing from prodeltaic, mud-rich to sandy nearshore sediments. Sedimentary facies analysis, integrated with macrofaunal and microfloral palaeoecological studies, indicate a wave-dominated, tidally influenced deltaic environment. Four depositional sequences (1–4) record the role of relative sea-level changes in controlling the stepwise progradation of the system. Prodeltaic and distal delta-front deposits (Sequences 1, 2), comprise coarsening-upward parasequences of mud-rich heteroliths and bioturbated fine-grained muddy sands displaying draped slump scars. The overlying erosional sequence boundary is marked by incised valleys filled with fluvio-estuarine sediments; succeeding sand-rich facies (Sequences 3, 4) represent the proximal delta front and delta platform. The macro-invertebrate and palynological datasets display contrasting responses to the regressive history of the formation. The macrofaunal record in the distal deltaic sediments reflects the marine influence, though a stratigraphic increase in diversity was controlled both by ecological factors and biotic recovery following the K–Pg event. The associated palynological assemblage also displays a strong marine signal and includes typical outer neritic – oceanic dinoflagellate cyst taxa. A sharp decline in macrofossil diversity and abundance in Sequences 3, 4 is compatible with ecological stress in shallow-water, restricted inshore settings. Though the palynological record at this level is terrestrially dominated, the marine component reflects the cosmopolitan nature of dinoflagellates, displaying the highest diversities in the formation. The regressive Sobral Formation ended a protractedc.60 Myr history of regional subsidence and marine sedimentation; although amplified by two Danian sea-level falls of probable eustatic origin, the regressive trend heralded mid-Paleocene basin inversion potentially linked to the onset of regional tectonic reorganization that ultimately led to opening of the Scotia Sea.