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四川江油马角坝、北川沙窝子是龙门山上泥盆统、下石炭统区域性主要岩石地层单位的命名地,对这两地及前龙门山北段地区的调查发现:1)前人关于马角坝地区下石炭统的层序和马角坝组主要化石群的记载有与实际不符之处,当地实际缺失杜内期至维宪早、中期地层,总长沟群的时代应属晚维宪—谢尔普霍夫期,重新厘定马角坝组含义,新指定北川桂溪沙窝子的长滩子剖面为该组的参考剖面;2)在长滩子剖面长滩子组顶部Beichuano-phyllum与Cystophrentis珊瑚化石富集层之上、马角坝组Pseudouralinia富集层之下的大套厚层白云岩层组合的中上部层位,发现Cystophrentis等化石,基于这套厚层白云岩组合的岩性特征明显、顶底接触关系清楚、区域展布广泛,建议引用前人提出的黑岩窝组,同时对黑岩窝组的岩性、岩层组合与古生物组合特征、厚度和时代归属等作了补充和修正,根据其中所含生物群认为黑岩窝组时代为晚泥盆世法门晚期;3)通过与周边地区的地层对比,探讨了龙门山石炭纪的古地理格局及环境演变,认为除前龙门山中部的桂溪—沙窝子等狭窄地区因长期地处泥盆纪海水入侵通道,地势低洼,出现了残存式的杜内期沉积外,前龙门山南、北段广大地区杜内期至维宪早、中期已大部抬升露出水面,直到维宪晚期的全球性海侵,前龙门山遂再度没于水下,出现准平原化浅滩相沉积环境,并延续至石炭纪末。
Sichuan Jiangyou Ma Kok Dam and Beichuan Chu Shazi are the naming of the Upper Devonian and Lower Carboniferous lithologic units in the Longmen Mountains. The survey on these two places and the northern part of Longmenshan found that: 1) The sequences of the Lower Carboniferous in Majiaba area and the records of the major fossil groups in the Majiaba Formation are inconsistent with the actual records. The time when the local Dumenian-Weixian early, middle-stage strata and the total Changgou Group were actually missing should be Late- In the constitution-Serpukhov period, the meaning of the Majiaba Formation was re-determined. The Longtan section newly designated as Shawozi in Guixi, Beichuan was the reference section of the group. 2) Beichuano-phyllum and Cystophrentis coral at the top of the Longtan Sub- Above the fossil-rich layer, the middle-upper strata of the large set of thick dolomite assemblages beneath the Pseudouralinia enrichment layer of the Majiaba Formation show the presence of Cystophrentis and other fossils based on the lithologic features of this thick layer of dolomite assemblages, It is suggested to refer to the black rock nest set proposed by the predecessor, and to supplement and amend the lithology, lithology combination, palaeo-creature assemblage, thickness and age attribution of Heiwo-Wei Formation. According to The biota in it holds that the age of the Black Rock Formation was Late Phanerozoic. (3) By comparing with the strata in the surrounding area, the paper discussed the paleogeographic pattern and environmental evolution of the Longmen Shan Carboniferous. Because of long-standing Devonian seawater intrusion channels and low-lying terrain, residual sedimentary Duneian sediments were found in the narrow areas such as Xi-Shawozi. Long ago, Most of the water has been lifted up to the surface until the late Vistula global transgression. The former Longmen Mountain was once again submerged, and a quasi-plain shoal facies sedimentary environment was formed and extended to the end of the Carboniferous.