| 豫西荥巩——新密煤田太原组、山西组的沉积环境和聚煤规律 |
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| 引用本文： | 张年茂
,杨起
,李宝芳.豫西荥巩——新密煤田太原组、山西组的沉积环境和聚煤规律[J].现代地质,1988(2). |
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| 作者姓名： | 张年茂 杨起 李宝芳 |
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| 摘 要： | 荥巩和新密煤田是豫西北部的两个相邻煤田。主要含煤地层为晚古生代晚石炭世太原组和早二叠世山西组,总厚100—150m;下石盒子组及晚二叠世的上石盒子组在本区仅偶含薄煤层。太原组位于含煤岩系最底部,为碳酸盐岩和碎屑岩交替沉积,灰岩形成于清澈、温暖、浅水的陆表海潮下环境,碎屑岩则为潮道和潮间带为主的潮道、潮坪沉积。太原组含有6—7层薄煤层,形成于咸水或半咸水的泥炭沼泽中。山西组几乎全由碎屑岩组成,下部发育本区的主要可采煤层二_1煤。二_1煤以下层位为潮坪和横向与之共生的潮道、潮沟及河口潮汐砂脊沉积,二_1煤以上为河流作用为主的三角洲沉积,三角洲由北向南进积到半咸水的海湾中。二_1煤形成于海退时期,它们堆积在滨海平原的淡水泥炭沼泽中,其厚度变化及发育程度主要受成煤前沉积环境控制,但在本区西部构造较复杂处,煤层厚度受后期构造影响较大。沉积环境对煤层原生厚度的影响主要表现在潮坪和废弃的潮道、潮沟、河口潮汐砂背沉积物之上,煤层发育好,而在二_1煤之下有活动的潮道及河口潮汐砂脊发育时,煤层较薄或不发育。
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| 关 键 词： | 沉积环境 陆表海 潮道 潮坪 河流作用为主的三角洲 河口潮汐砂脊 分流 间湾充填 咸水或半咸水沼泽 淡水沼泽 豫西 |
DEPOSITIOML ENVIRONMENTS AND COAL-ACCUMULATING CHARACTERISTICS OF LATE PALEOZOIC TAJYUAN AND SHANXI FORMATION IN XINGGONG-XINMI COALFIELDS, WESTERN HENAN PROVINCE |
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| Zhang Nianmao Yang Qi Li Baofang.DEPOSITIOML ENVIRONMENTS AND COAL-ACCUMULATING CHARACTERISTICS OF LATE PALEOZOIC TAJYUAN AND SHANXI FORMATION IN XINGGONG-XINMI COALFIELDS, WESTERN HENAN PROVINCE[J].Geoscience——Journal of Graduate School,China University of Geosciences,1988(2). |
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| Authors: | Zhang Nianmao Yang Qi Li Baofang |
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| Institution: | Chinga University of Geosciences |
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| Abstract: | Xinggonginmi Coalfields are located in the southwest of the North China Coal Basin, western Henan Province. The Late Paleozoic coal-earing strata are composed of Taiyuan Formation of the Late Carboniferous and Shanxi Formation of the Early Permian. Mainly discussed in this paper are the depositional environments and the coal-ccumulating characteristics.
Taiyuan Formation, with a thickness of 40?0 m, lies uncomformably on the carbonate deposits of the Middle Ordovician Series. Taiyuau Formation can be divided into three members; the lower and upper members which mainly are composed of carbonate rocks, and the middle memberwhich consists of clastic rocks. From the combination of the mar-ine fossils and the microfacies analysis of the carbonate rocks, a shallow marine environment of epicontinental sea has been recognized. The detrital rocks of the middle member commonly occur as tidal flat deposits consisting of thin interbedded sandstone, siltstone and mudstone, associated with thick cross bedded sandstone of tidal channel deposits. These tidal channel sandstones used to be considered as fluvial deposits, since the meandering point bar and the bimodel cross bedding have been found in this area, it is suggested that the sandstones probably are related to the tidal channel deposits.
There are 6? thin coal seams occuring in Taiyuan Formation, but only the lowest seam is workable. Coal seams usually occur on the top of regressive sequence and are overlain by the carbonate rocks. The high sulphur content, especially in which the distinguished framboid, indicates that the marshes and peat swamps were developed on the extensive strand plain and inundated by the incursion of sea water intermittently.
Shanxi Formation, which overlying Taiyuan Formation, is composed of clastic rocks, with a thickness of 60?0m and contains the main mineable coal seam. The interval between the uppermost limestone of Carboniferous and the main coal seam of Shanxi Formation is generally several meters thick and consists of interbedded sandstone, siltstoiae and mudstone representing tidal flat deposits. Cross bedded fining upward sequence of tidal channel sandstone and coarsening upward sequence sandstone of tidal sand ridge of the river mouth have also been recognized. The roof of the main coal seam is represented by the dark grey mudstone, plant fragments are common and semi梑rackish fossils occasionally can be seen. Thick cross bedded sandstone which contains abundant muscovite and the associated fine deposits and thin coal seams overlie the main coal seam, indicating a fluvial-dominated delta environment. The progradational direction of the delta was from the north to the sputh during the Early Permian depositio-nal time.
The thickness of the main coal seam ranges from 0 to more than 10 meters, average 5?m, and is controlled mainly by the depositional environments except the subsequent tectonic movement which plays an important role in the northwest part of the study area. Contrast to the Carboniferous coal, the Permain coal is characterized by the low sulphur and high vitrinite content. These implicate that the peat swamps developing on the flat strand plain are dominated by fresh water and woody plant communities. Generally the thicker coal occurs where the underlying sandstone is thinner. Therefore the tidal flats and the abandonded tidal creeks and tidalchannels all are favorite for peat swamp developing, but where the active tidal channel occupied, the peat swamps are hardly persisted. |
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| Keywords: | : sedimentary environment epicontinental sea tidal channel tidal flat fluvial-dominated delta river mouth tidal sand ridge interdistri- butory bay fill marine or brackish swamp fresh swamp western ofHenan |
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