山东青岛早白垩世新地层单位--灵山岛组

THE LINGSHANDAO FORMATION:A NEW LITHOSTRATIGRAPHIC UNIT OF THE EARLY CRETACEOUS IN QINGDAO, SHANDONG, CHINA

近年的野外调查和室内研究发现,山东省青岛市灵山岛原被认为是河湖相的莱阳群法家茔组,实际上为一套早白垩世海相浊积岩,目前仅见于灵山岛。由于该套地层与临近地区的同期任何地层单位都无法进行对比,为此建议建立一新的岩石地层单位——灵山岛组。灵山岛组外观上为典型的复理石,主要表现为灰黄色薄层砂岩、粉砂岩与黑色的泥岩构成良好的韵律层;其下部被海水淹没,未见底,其上被一层流纹岩不整合覆盖,出露部分厚度超过100m。灵山岛组所含化石稀少,仅见少量孢粉且保存不好,以Classopollis和原始两气囊类为主;此外还含有与海水活动有关的沟鞭藻碎片和膜状藻类片段。综合碎屑锆石年龄和孢粉组合,灵山岛组的年龄大约可以限定为早白垩世早中期,不排除其下部含有晚侏罗世沉积的可能。灵山岛组之上的流纹岩大致相当于鲁东下白垩统青山群下部。

A new lithostratigraphic unit, the Lingshandao Formation, is established to represent a set of Early Cretaceous marine deposits in Lingshan Island, Qingdao, Shandong, China, which was previously considered to be the terrestrial Fajiaying Formation of the Laiyang Group. This formation, only distribu- ted in Lingshan Island, is a set of marine flysch composed of grayish yellow thin-bedded fine sandstones or siltstones interbedded with black mudstones or shales. The flysch rhythmites consist of graded sand or silt intervals interbedded with black mudstones. It has an exposed thickness of over 100 m with the lower part submerged and the top unconformably overlain by a thick layer of rhyolite. Fossils from the Lingshandao Formation are represented by rare and poorly preserved spores and pollen, dominated by Classopollis and bisaccate pollen, as well as scarce fragments of marine dinoflagellate cysts and membranous algae. Bios- tratigraphic data and detrital zircon ages indicate that the Lingshandao Formation is most likely early-mid- dle Early Cretaceous in age, although the possibility cannot be excluded that the lower Lingshandao For- mation may be Late Jurassic in age. The overlying rhyolite is considered to roughly belong to the lower part of the Lower Cretaceous Qingshan Group.