Aptian to Coniacian (Early-Late Cretaceous) palynostratigraphy of the Gustav Group, James Ross Basin, Antarctica
Aptian to Coniacian (Early-Late Cretaceous) palynostratigraphy of the Gustav Group, James Ross Basin, Antarctica
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南极洲詹姆斯·罗斯盆地古斯塔夫群的阿普第期到科尼亚期（早白垩世至晚白垩世）孢粉地层学
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发表时间：
2002
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通讯作者：
J. Crame
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作者：
J. Riding;J. Crame
南极半岛詹姆斯罗斯盆地的古斯塔夫群是南半球白垩纪重要参考剖面的一部分。结合大型底栖动物和锶同位素地层学资料，以甲藻孢囊为主要成分的孢粉学资料表明，古斯塔夫群的时代为阿普提安-科尼亚期，厚度约2.6km。詹姆斯·罗斯盆地的阿普第阶-科尼亚阶孢粉植物群与澳大利亚和新西兰的同时代植物群非常相似，澳大利亚的孢粉学分带方案适用于古斯塔夫群。最低的单位，同时代的佩德森和Lagrelius点地层，都产生了早期Aptian甲藻孢囊。由于上覆的Kotick Point地层是早至中期Albian年龄，Aptian/Albian边界被放置在詹姆斯罗斯岛的Lagrelius Point地层-Kotick Point地层边界上，这一过渡可能是不整合的。虽然科蒂克角组主要是早期Albian的甲藻孢囊的证据，形成的最高部分似乎是中期Albian年龄。早期和中期Albian的这种分化细化了形成的年龄，以前被认为是Aptian-Albian，基于大型动物的证据。威士忌湾组是晚Albian到最新的Turonian时代的甲藻孢囊证据，这支持了大型动物的年龄。晚Albian孢粉植物群已记录从金湾，较低的Tumbledown悬崖，毕比点和中下刘易斯山成员。然而，Cenomanian年龄的上Tumbledown悬崖和朗姆酒湾成员，根据软体动物的证据，是不支持的甲藻孢囊植物群和进一步的工作，需要对这一继承。詹姆斯罗斯岛西北部威士忌湾组的最上部是中晚Turonian时代，这是由锶同位素地层学证实。最上面的单位，隐湖组，在古生物学和锶同位素证据上都是科尼亚阶。地层的最上部似乎是基于甲藻孢囊的早期Santonian，但锶同位素地层学限制了这一点，因为它不年轻于晚期Coniacian。这种精细的孢粉地层学极大地提高了詹姆斯罗斯盆地作为白垩纪南半球主要参考剖面的潜力。
Abstract The Gustav Group of the James Ross Basin, Antarctic Peninsula, forms part of a major Southern Hemisphere Cretaceous reference section. Palynological data, chiefly from dinoflagellate cysts, integrated with macrofaunal evidence and strontium isotope stratigraphy, indicate that the Gustav Group, which is approximately 2.6 km thick, is Aptian–Coniacian in age. Aptian–Coniacian palynofloras in the James Ross Basin closely resemble coeval associations from Australia and New Zealand, and Australian palynological zonation schemes are applicable to the Gustav Group. The lowermost units, the coeval Pedersen and Lagrelius Point formations, have both yielded early Aptian dinoflagellate cysts. Because the overlying Kotick Point Formation is of early to mid Albian age, the Aptian/Albian boundary is placed, questionably, at the Lagrelius Point Formation–Kotick Point Formation boundary on James Ross Island, and this transition may be unconformable. Although the Kotick Point Formation is largely early Albian on dinoflagellate cyst evidence, the uppermost part of the formation appears to be of mid Albian age. This differentiation of the early and mid Albian has refined the age of the formation, previously considered to be Aptian–Albian, based on macrofaunal evidence. The Whisky Bay Formation is of late Albian to latest Turonian age on dinoflagellate cyst evidence and this supports the macrofaunal ages. Late Albian palynofloras have been recorded from the Gin Cove, lower Tumbledown Cliffs, Bibby Point and the lower–middle Lewis Hill members. However, the Cenomanian age of the upper Tumbledown Cliffs and Rum Cove members, based on molluscan evidence, is not supported by the dinoflagellate cyst floras and further work is required on this succession. The uppermost part of the Whisky Bay Formation in north-west James Ross Island is of mid to late Turonian age and this is confirmed by strontium isotope stratigraphy. The uppermost unit, the Hidden Lake Formation, is Coniacian in age on both palaeontological and strontium isotope evidence. The uppermost part of the formation appears to be early Santonian based on dinoflagellate cysts, but strontium isotope stratigraphy constrains this as being no younger than late Coniacian. This refined palynostratigraphy greatly improves the potential of the James Ross Basin as a major Cretaceous Southern Hemisphere reference section.