Stratigraphy and vertebrate paleoecology of Upper Cretaceous–?lowest Paleogene strata on Vega Island, Antarctica
Stratigraphy and vertebrate paleoecology of Upper Cretaceous–?lowest Paleogene strata on Vega Island, Antarctica
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DOI：
10.1016/j.palaeo.2014.03.005
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发表时间：
2014-05
期刊：
影响因子：
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通讯作者：
E. Roberts;M. Lamanna;J. Clarke;Jin Meng;E. Gorscak;J. Sertich;P. O’Connor;Kerin M. Claeson;R. Macphee
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文献类型：
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作者：
E. Roberts;M. Lamanna;J. Clarke;Jin Meng;E. Gorscak;J. Sertich;P. O’Connor;Kerin M. Claeson;R. Macphee
López de Bertodano组的上白垩统（Maastrichtian）Sandwich海崖段在南极半岛东北海岸詹姆斯罗斯盆地的维加岛上出露良好。虽然该单元是南极洲白垩纪末脊椎动物化石最丰富的来源之一，但它也是盆地中沉积学和地层学特征最少的单元之一。在深入勘探脊椎动物化石和对维加岛历史古生物区进行地层评估的同时，对雪丘岛组的三明治海崖段和下伏开普兰姆段进行了新的岩相和地层分析。这一努力导致了桑威奇海崖段地层学的修订，以及重要的陆地和海洋脊椎动物化石地点的精确地层位置。相分析显示，剖面呈变细变浅的上升趋势，在桑威奇海崖段顶部附近新识别的层序边界处达到高潮，随后沉积了以前未识别的6 m厚的可能是冲积成因的基质支撑卵石-卵石砾岩。紧接着覆盖在该单元上的细粒海侵砂岩和粉砂岩中发育良好的Thalassinoids洞穴网络表明快速恢复到海洋条件。在盆地南部西摩岛上的López de Bertodano地层顶部和上覆（古新世）索布拉尔地层底部，也有类似的地层模式。虽然没有发现化石来限制Vega岛上10-15 m层序的年龄，但这一级别以下的地层可以确信地置于Manumiella bertodano间隔带内，该间隔带延伸到西摩岛K-Pg边界以下的一小段距离。因此，根据层序地层学和岩石地层学证据，维加岛上最上部10-15 m的层序可能包括古近系-古近系边界以及古新统索布拉尔组的几米。
The Upper Cretaceous (Maastrichtian) Sandwich Bluff Member of the López de Bertodano Formation is well exposed on Vega Island in the James Ross Basin off the northeastern coast of the Antarctic Peninsula. Although this unit is one of the richest sources of end-Cretaceous vertebrate fossils in Antarctica, it is also one of the least sedimentologically and stratigraphically characterized units in the basin. New facies and stratigraphic analyses of the Sandwich Bluff Member and the underlying Cape Lamb Member of the Snow Hill Island Formation were performed in tandem with intensive prospecting for fossil vertebrates and stratigraphic assessment of historic paleontological localities on Vega Island. This effort has led to a revised stratigraphy for the Sandwich Bluff Member and the precise stratigraphic placement of important terrestrial and marine vertebrate fossil localities.Facies analysis reveals a fining and shallowing upward trend through the section that culminates in a newly recognized sequence boundary near the top of the Sandwich Bluff Member, followed by the deposition of a previously unrecognized, 6 m-thick, matrix-supported pebble–cobble conglomerate of probable alluvial origin. Immediately overlying this unit, well-developedThalassinoidesburrow networks in fine-grained transgressive sandstones and siltstones indicate a rapid return to marine conditions. A similar stratigraphic pattern is well documented at the top of the López de Bertodano Formation and the base of the overlying (Paleocene) Sobral Formation on Seymour Island in the southern part of the basin. Although no fossils were recovered to constrain the age of the upper 10–15 m of the succession on Vega Island that preserves the newly recognized upper sequence boundary, strata below this level can be confidently placed within theManumiella bertodanointerval zone, which extends to a short distance below the K–Pg boundary on Seymour Island. Hence, based on sequence stratigraphic and lithostratigraphic evidence, the uppermost 10–15 m of the succession on Vega Island may encompass the Cretaceous–Paleogene boundary together with a few meters of the Paleocene Sobral Formation.