富饶阶地表地层剖面

黑龙江省嘉荫县乌云镇地区中生代结束前后连续沉积了两套含煤地层,即上部的古新统乌云组和下部的马斯特里赫特阶富饶组。富饶阶相当于富饶组上段地层,但由于其代表剖面顶、底不全,且可参照的钻孔岩心已不复存在,因此有必要在原命名地区寻找新的地表露头剖面。乌云镇西北白头山黑龙江沿岸出露富饶阶上部地层,其上部含有丰富的孢粉化石,自下而上初步确定了两个孢粉组合:杉粉(Taxodiaceaepollenites)-红杉粉(Sequoiapol-lenites)孢粉组合和鹰粉(Aquilapollenites)-肋桦粉(Betulaepollenites)孢粉组合。这两个孢粉组合都有鹰粉类(Aquilapollis)化石,计有5属10多种化石,其中除了小刺鹰粉(Aquilapollenites spinulosus)一种可由上白垩统上延入古近系下部地层外,其他多数出现在环太平洋的上白垩统最上部地层中(马斯特里赫特阶)。由于富饶组下段相当于明水阶(马斯特里赫特阶中、下部),因而富饶组上段,即富饶阶,相当于马斯特里赫特阶的上部。对该剖面下部的流纹质晶屑沉凝灰岩采样进行SHRIMP锆石U-Pb法测年,定年结果为66±1Ma,与上述孢粉生物地层学结论相吻合。由此可以推测白垩系-古近系界线似在乌云组与富饶组之间,即厚层含砾砂岩的底部,但需进一步证实。

SEARCHING FOR THE STRATOTYPE OF THE FURAOAN STAGE IN HEILONGJIANG PROVINCE, NORTHEAST CHINA

The Cretaceous/Paleogene (Tertiary) (K/T) boundary is defined by great extinctions which oc- curred 65. 5Ma ago. The study of this boundary attracts the interest of the geologists in searching for the causes of the dramatic extinctions. In China the Cretaceous and Paleogene deposits are mainly terrestrial in origin. And the non-marine K/T boundary transition beds are found in the Baitoushan section in Jiayin County of Heilongjiang Province. The coal-bearing Palaeocene Wuyun Formation lies conformably over the coal-bearing Maastrichtian Furao Formation. Below the coal-bearing sequence crops out the Companian Yuliangzi Formation, which yields Mandschurisaurus amurensis Riabinia. The Furao Formation is subdi- vided into two members.Its Lower Member contains an Aquilapollenites-Ulmoideipites Assemblage,and indicates Mingshuian in age(early—middle Maastrichtian).Its Upper Member(the Furaoan Stage)yields a rich polynomorph assemblage yielding more than 10 species of Aquilapollis,which indicates a late Maas- trichtian in age.SHRIMP Zircon radiometric dating of tuff from the Baitoushan section gives 66±1Ma. This age Is consistent with the result of the palymorph biostratigraphy.And the K/T boundary lies be- tween the Wuyun and Furao Formations.