Title: UPPER JURASSIC BUCHIID (BIVALVE) SEQUENCE IN SUIBIN AREA, EASTERN HEILONGJIANG, NE CHINA
Abstract: The present article reports a fossil buchiid sequence discovered from the bore-holes in Mesozoic coal-bearing measures in Suibin area near the Heilongjiang (Amur) River (Text-figs. 1, 2), where the Mesozoic strata are overlain by several hundred meters of Cenozoic or Recent river deposits. The stratigraphic sequence of the coal-bearing measures were surveyed and summarized by the 110th Exploring Team of the NE China-Nei Monggol Coal Corporation (Huang, 1989) as follows:
Muling Formation: Grey sandstones and siltstones with plant-bearing coal seams. 480—1000 m
conformity
Chengzihe Formation: Blackish grey coal measure containing plants, bivalves and gastropods. 350—1290 m
disconformity
Dongrong Formation: Blackish green sandstones and siltstones with buchiids, ammonites and dinoflagellates. 395m
conformity
Suibin Formation: Grey sandstones and gravelly sandstones. 263 m
Marine bivalves have mainly been found in the Dongrong Formation, the upper part of the Suibin Formation and the basal part of the Chengzihe Formation, whereas brackish water bivalves commonly occur in the coal-bearing Muling and Chengzihe Formations. This paper is the first study on the bivalve faunas of, this area, dealing with the fossil buchiids from the marine sediments of the Dongrong Formation. Text-fig. 3 shows the occurrence of buchiids in the relatively complete stratigraphic column of this formation, in which the fauna can be subdivided into four buchiid zones in ascending order as follows: (1) B. concentrica zone. This zone occurs in the lower part of the Dongrong Formation and contains the only buchiid species B. concentrica(J, de C. Sowerby) distributed at depths from 762m to 690m in Bore No. 86-11; no ammonites were found therein, but rich dinoflagellates have been obtained at the depths of 755—754m and determined as the Gonyaulacysta jurassica assemblage by Sun X. K. and He C. Q., indicating the age of late Oxfordian-early Kimmeridgian. B. concentrica is a zonal species in the Boreal realm, ranging from Middle Oxfordian to basal Upper Kimmeridgian with its abundant occurrence in Lower Kimmeridgian according to Surlyk and Zakharoy (1982, p. 732). In combination with the evidences of buchiids and dinoflagellates, the B. concentrica zone of Suibin area is dated Upper Oxfordian—Lower Kimmeridgian. This zone is associated with some non-buchiid bivalves, such as Meleagrinella sp., Palaeonucula makitoensis Hayami, Palaeoneilo cf. belaensis Cox, etc.
(2) B. tenuistriata zone. This zone is represented by the great abundance of Buchia tenuistriaca (Lahusen) occurring in the middle part of the Dongrong Eormation at depths from 642m to 608m in the same bore. An ammonite-bearing bed was found near the top of the zone (608.75m), with the pcorly preserved ammonites preliminarily identified as Perisphinctidae gen. et sp. ind. by Wang Y. G. However, B. tenuistriata is commonly regarded as the zonal species ranging from the upper part of Lower Kimmeridgian to basal Lower Volgian in the Boreal realm. It was found to be especially abundant in the Upper Kimmeridgian of the realm (Zakharov, 1981; Surlyk and Zakharov, 1982). In the Suibin area B. tenuistriata is very rich within the present zone, indicating that this zone can be considered as belonging to the thriving stage of the species in the Upper Kimmeridgian.
(3) B. mosquensis-B, rugosa zone. This zone continuously overlies the B. tenuistriata zone, occupying the beds with a greater thickness in the upper part of the Dongrong Formation, at a depth from 600m up, to 512m as seen in Bore No. 86-11. The buchiids are grouped by B. rnosquensis (yon Buch), B. rugosa (Fischer), B. ex gr. russiensis (Favlow), and B. ex gr. taimyrensis Zakharov, while non-buchiid bivalves are also developed, with such species as Praesaccella yatsushiroensis Tamura, Pleuromya cf. hidensis Hayami, Thracia shokawensis Hayami, Trigonucula suibinensis sp. nov., Oxytoma tetoriense Hayami, Palaeoneilo cuneiformis (J. Sowerby), Camptonectes (C.) cf. wandaensis Gu, etc. In the middle and upper parts of this zone there exist two beds bearing ammonites which have been identified as cf. Streblites sp. by Wang Y. G. in colletions. Many dinoflagellates were also discovered from the middle part of the zone; they are summarized as the Amphorula delicata assemblage and dated the Portlandian in age by Sun X. K. and He C. Q.
In this zone B. rugosa is restricted to the lower part, while B. mosquensis has a longer range from the base to the top. In the Boreal localities the two species mainly ranged from Upper Kimmeridgian to Middle Volgian and especially developed in Lower-Middle Volgian.
Since the specimens of B. ex gr. russiensis and B. ex gr. taimyrensis are not well-preserved, their occurrences in the upper part of this zone in the Suibin area accordingly will not be helpful for age dating, although their typical forms are limited to the Middle Volgian of the Russian Platform and northern Siberia. However, the age of the present buchiid zone can be determined as belonging to early-Middle Volgian mainly based on the development of the former two species with reference to the range of the underlying B. tenuistriata zone.
(4) B. fischeriana zone. The materials of this zone are taken from Bore No. 79-1, in which the buchiid-horizone can be accurately correlated with the uppermost part of the Dongrong Formation, corresponding to the depth of about 435m in Bore No. 86-11 which beara the above-mentioned three buchiid zones. The species B. fischeriana (d'Orbigny) is the only representative of this zone; however, it is rich in occurrence. In the Boreal realm B. fischeriana is a common zonal species widely distributed in eastern Greenland, northern Canada, California, northeast Asia, Spitzbergen, Russian Platform and north Siberia. Since in these localities its great abundance is in Upper Volgian and rarely in the upper part of Middle Volgian and basalRyazannian (Surlyk and Zakharov, 1982), the present paper refers this zone to the Upper Volgian.
Publication Year: 1992
Publication Date: 1992-01-01
Language: en
Type: article
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Cited By Count: 7
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