西沙北海槽第四纪的介形虫

西沙北海槽位于南海北部,是南海大陆坡上较大的海槽之一。本文所研究的介形虫化石系取自西沙北海槽东段的两个站位(KL37、KL41)柱样中。以上两站位中的介形虫化石组合以Krithe属居优势,其次是Wichmannella, Bradleya, Cytheropteron, Acantho-cythereis, Argilloecia, Abyssocythere, "Cythere", Parakrithe, Paijen-borchella等; KL37站、KL41站其沉积地层划分为中、上更新统及全新统。中、上更新统中介形虫化石数量比较丰富,化石面貌相似,均以Krithe sawanensis, Wichmannella dasy-derma, Acanthocythereis cf. araneosa等为主要成分。全新统中介形虫属种单调,化石少,含量较多的有"Cythere" sulcatoperfonata, Bradleya albatrossia, Kriteintrocurva, Abyssocythere regalis等。化石的破碎、溶蚀现象较普遍。

QUATERNARY OSTRACODA FROM NORTHERN XISHA TROUGH OF SOUTH CHINA SEA

The Northern Xisha trough is situated in the northern part of the South China Sea.The ostracoda fossils dealt with in this paper were collected from the stations KL37 and KL41 in the eastern part of the Northern Xisha trough. The sampling station KL37 is located in the southern slope of the trough, which is 2004m below the sea level and its columnar sediment is 13.05m in length; the station KL41 is situated in the northern slope of the trough, which is 2120m deep and the columnar sediment is 13m in length (fig.l ) .Among the ostracoda fossil assemblages of the Northern Xisha trough, the most dominant genus is Krithe, other genera are Wichmannella, Bradleya, Cytheropteron, Acanthocythereis, Argilloecia, Abyssocythere, "Cythere" , Parakrithe and Paijenborchella etc. The sediments of stations KL37 and KL41 are divided into Middle, Upper Pleisto-cene and Holocene series. 1. In ostracoda assemblage of the Middle Pleistocene series the most domi-nant species are Krithe sawanensis Wichmannella dasyderma, Acanthocythereis cf. araneosa and Bradleya albatrossia, other species are Bradleya diet yon, Cy-theropteron sawanense, Abyssocythere recalls, Argilloecia af finis, "Cythere" sulcatoperfonata, Cytheropteron? trinidadensis and Krithe introcurva. 2. The principal features of the ostracoda assemblage in the Upper Pleistocene series resemble those of the Middle Pleistocene series in appearance, but the diver-sity of both species and genera and abundance of individuals are relatively higher in Upper Pleistocene. 3. The ostracoda fossils of Holocene series are monotonous in genus and species, and less in numbers, the species are dominated by "Cythere" sulcatoper-fonata, Abyssocythere regalis, Bradleya albatrossia, Krithe introcurva and Wichmannella circumdentata etc. 4. Only small amount of. Abyssocyther regalis and "Cythere" sulcatopernata has been found from the surface sediments of the station KL41.