加里东运动构造古地理及滇黔桂盆地的形成——兼论滇黔桂盆地深层油气勘探潜力

Tectonic palaeogeographic changes resulting from the Caledonian movement and the formation of the Dianqiangui Basin: Discussion on the deep exploration potential of oil and gas in the Dianqiangui Basin

中国南方的滇黔桂地区,早古生代与晚古生代之交曾经发生过较为强烈的加里东运动,包括三个幕:寒武纪末期的郁南运动,中、奥陶世末期的都匀运动以及志留纪末期的广西运动;奥陶系与志留系的残留不全和晚奥陶世至志留纪大片古陆———滇黔桂古陆的展布是加里东运动的重要体现。志留纪末期的广西运动之后,在大致相当于早古生代“滇黔桂古陆”分布的地区形成一个特殊的“滇黔桂盆地”,而且在滇黔桂盆地的主体部位常常是泥盆系直接覆盖在寒武系之上。寒武系,特别是下寒武统,由于寒武纪初期的快速海侵作用而在研究区域普遍发育烃源岩系;研究区域的泥盆系,特别是中泥盆统,在台间盆地中发育优质烃源岩。因此,巨大的构造古地理演变和海陆变迁,形成了一个晚古生代的泥盆系优质烃源岩与早古生代的下寒武统优质烃源岩的空间叠合区域,该叠合区域的加里东运动不整合面上、下的储集体即成为该地区的深层油气勘探对象,预示着滇黔桂盆地的深层存在较大的油气勘探潜力。

In the transitional period from the Early Palaeozoic to the I.ate Palaeozoic, there was strong Caledonian move ment in the Yunnar-Guizhou-Guangxi Area. The Caledonian movement can be divided into three episodes： the Yunan movement at the end of the Cambrian： the Duyun movement at the end of the Middle Ordovician; and the Guangxi movenment at the turn of the end of the Silurian and the beginning of the Devonian. The Caledonian movement in the study area led to the partial development of Ordovician strata and the absence of Silurian strata in the study area. There fore, a region called the Dianqiangui Oldland was formed between the Late Ordovician to the Silurian. After the Guangxi movement in the Late Palaeozoic. the Dianqiangui Oldland became a special sedimentary basin, i.c. the Dianqiangui Basin. Thus, Devonian strata rest directly on Cambrian strata in the main part of the study area. As a result of rapid transgression in the Early Cambrian. a sequence of excellent source rock was widely developed in the Lower Cambrian. Another sequence of Devonian .source rock, especially in the Middle Devonian, was formed in the inter-platform basin. Therefore, the great changes of continent and sea caused by the Caledonian movement in the study area resulted in the formation of a special region that is marked hy the superimposition of the Middle Devonian and Early Cambrian source rocks. The Middle Devonian souree rock is an excellent one in the Late Palaeozoic and the Early Cambrian .source rock is an excellent ,source rock in the Early Palaeozoic. In this special region, reservoirs situated above and below the unconformity of the Caledonian movement are important targets of oil-gas exploration, thus indicating great potential for oil and gas exploration in the Dianqiangui Basin.