The Longmenshan area is located at the western margin of Yangtze platform, where the Devonian is composed of clastic rocks, mixed clastic-carbonate rocks and carbonate rocks in ascending order, and was formed in the m...The Longmenshan area is located at the western margin of Yangtze platform, where the Devonian is composed of clastic rocks, mixed clastic-carbonate rocks and carbonate rocks in ascending order, and was formed in the marine environment from nearshore to outer shelf. Based on a study of six sections the Devonian in Longemenshan area is divided into 18 sequences and 5 sequence sets. The maximum transgressive high in the Devonian of this area occurred in Early Frasnian, corresponding to asymmetricus zone. The boundaries among the sequence sets are roughly corresponding to the bottom boundaries of Ⅰa',Ⅰc',Ⅱa, and Ⅱd in the Devonian of West Europe and North America, respectively. The frequencies of the relative sea level changes in this area vary in different periods, but can be correlated with those in the other regions of the world.展开更多
龙门山地区中泥盆统养马坝组混合沉积较为发育。通过对龙门山地区北川甘溪剖面养马坝组的野外实测,在混合相和混积层序研究的基础上,分析了养马坝组层序体系域中的混合沉积机理及其控制因素。研究表明:龙门山地区中泥盆统养马坝组由下...龙门山地区中泥盆统养马坝组混合沉积较为发育。通过对龙门山地区北川甘溪剖面养马坝组的野外实测,在混合相和混积层序研究的基础上,分析了养马坝组层序体系域中的混合沉积机理及其控制因素。研究表明:龙门山地区中泥盆统养马坝组由下部的以泥质为背景的Ⅰ型混积类型和中、上部以砂、灰为背景的Ⅱ型混积类型组成,混积机理包括间断混合、相混合和原地混合,前两种是主要类型。由陆向海依次发育混积滨岸、碎屑混积陆棚沉积和碳酸盐混积陆棚,建立了混积滨岸-混积陆棚沉积模式。养马坝组发育Ⅱ型混积层序,沉积体系域可划分为4种:陆架边缘体系域(shelf-margin systems tract,SMST)、海侵体系域(transgressive systems tract,TST)、早期高位体系域(early highstand systems tract,EHST)和晚期高位体系域(late highstand systems tract,LHST)。各体系域均有不同程度的混合沉积现象,但混积沉积机理存在差别:SMST和LHST以间断混合为主,相混合为次,TST和EHST以相混合为主;风暴作用是引起龙门山地区中泥盆统养马坝组间断混合的最主要的驱动因素。相对海平面变化、物源供给、碳酸盐生产速率和气候变化是控制和影响混合沉积的因素。SMST和高位体系域(highstand systems tract,HST)主要受相对海平面的变化有关,TST则受控于物源供给,气候变化不同程度地影响各体系域的混合作用。展开更多
文摘The Longmenshan area is located at the western margin of Yangtze platform, where the Devonian is composed of clastic rocks, mixed clastic-carbonate rocks and carbonate rocks in ascending order, and was formed in the marine environment from nearshore to outer shelf. Based on a study of six sections the Devonian in Longemenshan area is divided into 18 sequences and 5 sequence sets. The maximum transgressive high in the Devonian of this area occurred in Early Frasnian, corresponding to asymmetricus zone. The boundaries among the sequence sets are roughly corresponding to the bottom boundaries of Ⅰa',Ⅰc',Ⅱa, and Ⅱd in the Devonian of West Europe and North America, respectively. The frequencies of the relative sea level changes in this area vary in different periods, but can be correlated with those in the other regions of the world.
文摘龙门山地区中泥盆统养马坝组混合沉积较为发育。通过对龙门山地区北川甘溪剖面养马坝组的野外实测,在混合相和混积层序研究的基础上,分析了养马坝组层序体系域中的混合沉积机理及其控制因素。研究表明:龙门山地区中泥盆统养马坝组由下部的以泥质为背景的Ⅰ型混积类型和中、上部以砂、灰为背景的Ⅱ型混积类型组成,混积机理包括间断混合、相混合和原地混合,前两种是主要类型。由陆向海依次发育混积滨岸、碎屑混积陆棚沉积和碳酸盐混积陆棚,建立了混积滨岸-混积陆棚沉积模式。养马坝组发育Ⅱ型混积层序,沉积体系域可划分为4种:陆架边缘体系域(shelf-margin systems tract,SMST)、海侵体系域(transgressive systems tract,TST)、早期高位体系域(early highstand systems tract,EHST)和晚期高位体系域(late highstand systems tract,LHST)。各体系域均有不同程度的混合沉积现象,但混积沉积机理存在差别:SMST和LHST以间断混合为主,相混合为次,TST和EHST以相混合为主;风暴作用是引起龙门山地区中泥盆统养马坝组间断混合的最主要的驱动因素。相对海平面变化、物源供给、碳酸盐生产速率和气候变化是控制和影响混合沉积的因素。SMST和高位体系域(highstand systems tract,HST)主要受相对海平面的变化有关,TST则受控于物源供给,气候变化不同程度地影响各体系域的混合作用。
