鄂尔多斯地块南缘构造演化及其对盆地腹部的构造—沉积分异的效应

鄂尔多斯地块南缘处在盆地与秦岭造山带之间这一盆—山结合的过渡部位，由于构造位置的特殊性，自古生代以来其构造及沉积面貌与盆地腹部地区存在较大差异，具体表现在：1）早古生代沉积开始早、结束晚；2）晚古生代沉积开始晚；3）印支期西南部发生局部坳陷沉降；4）燕山晚期盆地南部强烈抬升（远高于盆地东部的同期抬升）；5）喜马拉雅期渭河地区快速沉陷与渭北隆升。盆地南部经历了3次大的构造格局转换：一是晚古生代末—印支期西南部“由隆到坳”的构造转换；二是印支期末—燕山期主体构造走向由北西—南东向到南北向的转换（构造转向）；三是燕山期末—喜马拉雅期渭河地区由强烈隆升到快速沉降的转换（构造反转）。盆地南部在不同时期所表现出的与盆地本部的不同耦合特征均根源于区域大地构造背景的差异：1）早古生代处于活动大陆边缘构造环境；2）海西期—印支期受古特提斯洋开裂—闭合的影响；3）燕山期受古太平洋板块俯冲的影响；4）喜马拉雅期受印度板块俯冲与太平洋板块俯冲的共同制约。鄂尔多斯地块南缘经历强烈伸展与造山过程，引起了其与盆地腹部的构造—沉积分异。

Tectonic evolution in the southern Ordos block and its significance in the tectono-depositional differentiation in the interior of the Ordos Basin

The southern part of the Ordos Basin is located in the transitional position between the basin and the Qinling orogenic belt. Due to the particularity of the tectonic location, the structural and sedimentary features of the southern parts of the basin have been greatly different from those of the basin itself since the Paleozoic, which are shown in the following aspects: 1） Early Paleozoic sedimentation started early and ended late; 2） Late Paleozoic sedimentation started late; 3） Partial depression subsidence occurred in the southwest during the Indosinian; 4） Strong uplift in the south of the basin in the late stage of Yanshanian （much higher than that of the eastern part of basin）; 5） Rapid subsidence of Weihe area and uplift of the northern Weihe area in the Himalayan. The southern part of the basin has experienced three major structural pattern transformations: The first is the structural transformation from uplift to depression in the southwest during Late Paleozoic to Indosinian; the second is the direction transformation （structural turn） of the main structural trend from northwest-southeast to north-south orientation during the end of Indosinian to Yanshanian; the third is the transformation （structural inversion） from strong uplifting to rapid subsidence in Weihe area from Late Yanshanian to Himalayan. The different structure-sediment characteristics of the southern basin from those of the main part of basin itself in different periods all rooted in the difference of regional tectonic background: 1） It was in the active continental margin tectonic environment in the Early Paleozoic; 2） It was affected by the opening and closing of the Paleo-Tethys ocean in the Hercynian-Indosinian; 3） It was affected by the subduction of the Paleo-Pacific plate in the Yanshanian; 4） It was restricted jointly by the subduction of the Indian plate and the Pacific plate in the Himalayan Period.