Palynostratigraphic Study of the Nemuro Group.

1989年，Takahashi和Ueda从北海道东部Nemuro组的滨中- oborogawa组、Akkeshi组和Tokotan组采集了48个样本，Takahashi从Akkeshi组的7个样本中检测了565个孢型，从Ochiishi湾周围的Akkeshi组和Tokotan组的9个样本中检测了768个孢型，从Choboshi海边的Akkeshi组的3个样本中检测了36个孢子型。根据前人对有孔虫类、菊石类、锥虫类纳米化石等的生物地层资料，认为阿克什组属于马斯特里赫特时代，托克坦组属于大年时代。Akkeshi组和Tokotan组均产有大量的花粉粒，包括triprojtacites花粉组、Callistopollenites、Wodehouseia等。这是马斯特里赫特时间的一个很好的指示器。Akkeshi组和Tokotan组之间的微区系变化不大。1990年，Takahashi在Nemuro市Konbumori采集了11个Tokotan组样本，对其中9个样本的746个孢体进行了鉴定，鉴定出176种。并与大石的Tokotan组和马斯特里赫特时代的Tokotan组的孢粉植物群进行了比较。对于以砾岩层为主，只有部分泥岩层限制分布的Kiritappu组，Takahashi在Kiritappu的4个样品中发现了105个岩形，在Yururi岛的4个样品中发现了267个岩形。他总共研究了137个物种。Kiritappu组与Tokotan组和Akkeshi组共有52种。这些常见物种中的大多数出现了很长时间。基里塔布组岩石形态组合的最大本质区别是Auilapollenites、callistpollenites、Wodehousiea等。仅在马斯特里赫特地区出现的花粉粒没有出现，木兰科的花粉粒出现较新。据此，在Tokotan组和Kiritappu组之间划分白垩纪(Maastrichtian) /第三纪（Danian）界线可能是合理的。少

In 1989, Takahashi and Ueda collected 48 samples from the Hamanaka-Oborogawa, Akkeshi, and Tokotan Formations of the Nemuro Group in eastern Hokkaido and Takahashi examined 565 palynomorphs from 7 samples of the Akkeshi Formation around Akkeshi Bay, 768 palynomorphs from 9 samples of the Akkeshi and Tokotan Formations around Ochiishi Bay, and 36 sporomorphs from 3 samples of the Akkeshi Formation along the seaside of Choboshi. According the previous biostratigraphic data on foraminiferida, ammonoids, inoceramids nannofossils etc., the Akkeshi Formation is of Maastrichtian age the Tokotan Formation is of Danian age. Both the Akkeshi and Tokotan Formations yield many pollen grains of Triprojectacites pollen group, Callistopollenites, Wodehouseia etc. Which are a good indicator of Maastrichtian time. Microfloral change between the Akkeshi and Tokotan Formations is not so large. In 1990, Takahashi collected 11 samples of the Tokotan Formation at Konbumori, Nemuro city, examined 746 palynom … More orphs from 9 samples of it, and discriminated 176 species. This Tokotan palynoflora is compared with that of the Tokotan Formation at Ochiishi and of Maastrichtian age, too. Regarding the Kiritappu Formation which consists of predominant conglomerate beds and only some mudstone beds distributed restrictied, Takahashi found 105 palynomorphs from 4 samples at Kiritappu and 267 palynomorphs from 4 samples from Yururi Island. As a whole, he examined 137 species. The Kiritappu Formation yield 52 common species to both the Tokotan and Akkeshi Formations. Most of these common species appear for very long time. The largest essential difference of the palynomorph assemblage of the Kiritappu Formation is that Auilapollenites, Callistopollenites, Wodehousiea etc. Which appear restrictedly only in the Maastrichtian don't occur and pollen grains of the Magnoliaceae appear newly. Accordingly, it may be reasonable that the Cretaceous (Maastrichtian) /Tertiary (Danian) boundary is drawn between the Tokotan and Kiritappu Formations. Less