摘要
根据作者倡导的“单因素分析综合作图法”,对中下扬子地区二叠系进行了岩相古地理学研究及编图,共编制出下二叠统的鸡公岭组、栖霞组和茅口组(孤峰组)以及上二叠纪的吴家坪组(龙潭组)和长兴组(大隆组)的单因素基础图件20幅和岩相古地理图5幅,比例尺均为1:200万。从这些定量化的图件可以看出中下扬子地区二叠纪各期的岩相古地理特征及其演化历史。这是本区二叠系的油气以及其他沉积矿产预测和勘探的重要科学依据。
Middle and Lower Yangtze Region referred in this paper relates to eightprovinces, Sichuan,Guizhou. Hubei, Hunan, Jiangxi, Anhui,Jiangsu and Zhejiang i.e. , the region between 108°-122°E and 27°-33°N with an area of about 300,000km2
Perman of Middle and Lower Yangtze Region can be divided int two series and five five formations, the Lower Series including Jigongling, Qixia and Maokou Formation (Gufeng Formation), and the Upper Series including Wujiaping (Longtan Formation) and Changxing Formation (Dalong Formation).
'Single Factor Analysis and Comprehensive Mapping Method' advocated by the present author is used in this paper to study and map the lithofacies paleogeography of Permian of this area. 'Single factor', refers lithological. paleontological or other characteristics which independently reflect certain aspects of the sedime-nary environments of stratigraphical interval in an area. The following single factors are usedin this paper: thickness (m), content (%) of carbonate rocks, sparry grain limestones thin -bedded siliceous rocks, sandstones and biograins, thickness ratio of deep - water sediments to shallow - water sediments (D/S),etc. 20 single factor fundamental maps and 5 lithofacies paleogeographical maps of Jigongling, Qixia, Maokou (Gufeng), Wujiaping (Longtan) and Changxing Formation (Dalong Formation ) of Middle and Lower Yangtze Region were compiled, all with the scale of 1:2,000,000.
From these quantitative maps, the following can be seen :During of Jigongling Age In early Early Permian, the southeastern part of the study region, i. e. , the area in the south side of Lianyuan -Leping -Tonglu was an open carbonate platform sea while the most area in the north side was land.
During the deposition of Liangshan Member (belong to Qixia formation), the seawater invaded into study region from the south to the north . Then the former wide land area in northern part became clastic littoral zone, whereas in the south part it was still carbonate platform. With seawater rapidly invading into, the study region became a huge open carbonate platform sea throughout Middle to Late Qixia Age, and the paleogeographical differentiation in Qixia Age was not clear.
In Maokou Age. the differentiation of paleogeography was clear. In Lower Yangtze , the southeast clastic littoral zone, southwest slope and north basin were located respectively from southeast to northwest, displayed a threefold pattern. While in Middle Yangtze Region, the south Lichuan - Jiujiang carbonate platform, north slope and north basin were located respectively from south to north, displayed a sevenfold pattern. There wasSusong Penebank in the eastern margin of lichuan - jiujiang carbonate platfrom, a Tongling penebank within the-north basin, and a short -time sponge reef in the southeast clastic littoral zone. At the end of Maokou Age, the whole region was universally uplifted and some area suffered erosion in various degrees.
At the beginning of Late Permian, seawater invaded again. During Wujiaping Age, most of the Middle to Lower Yangtze Re to north, a fivefold pattern was displayed. There was a western Hubei basin and periphery slope around the basin on the west of the central carbonate platform.
In Changxing Age, with the developing of the transgression, southeast clastic littoral zone, southeast restricted sea,Jiangnan carbonate platform, north slope and north Basin were located orderly from southeast to northwest while .within western part, the south basin, the South slope, west carbonate platform, Jiang-nan carnonate Platfrom, West Hubei circumbasin slope, north slope, west basin and north basin were found from south to north, various banks were developed on the interior and margins of the platform in the eastern part.
Generally there were two cycles of transgressions and regressions throughout Permian in the strdy region. The first is from the beginning of Qixia Age to the end of Maokou Age and the second is from the beginning of Wujiaping Age to the end of Changxing Age , and or last to the Early Triassic. The paleogeographi
出处
《沉积学报》
CAS
CSCD
北大核心
1993年第3期12-24,共13页
Acta Sedimentologica Sinica
