The structure of the southeastern Gulf of California rifted margin is only partly known because of the thick sedimentary cover of the continental shelf and coastal areas of Sinaloa and Nayarit. Here we report the subsurface structure and probable age of the Mazatlán basin, one of the largest buried basins, based on interpretation of reprocessed by multichannel 2D reflection seismic profiles and an exploratory well drilled by Petroleos Mexicanos (PEMEX) between 1979 and 1980, as well as gravimetric data. The Mazatlán basin is located just north of the active subduction zone of the Rivera plate and west of the new oceanic crust accreted since the Pliocene at the mouth of the Gulf. The basin is bounded to the west by a high of the Late Cretaceous batholiths exposed in the Tres Marias Islands and in the normal faults bounding the Nayarit Troughs, and to the east by the late Oligocene-early Miocene extensional faults bounding the Sierra Madre Occidental. Based on the characteristics of the seismic profiles, the basin can be divided into three main sectors. The transition between the northern and central sectors is defined by an abrupt deepening of the basement that corresponds to the westward prolongation of ENE-WSW trending accommodation zones separating opposite tilted domains in the Sierra Madre Occidental. The acoustic basement is clearly defined in the central sector by a set of high-amplitude reflectors suggesting an igneous origin. The deepest part of the basin is located toward the coastal plain of Nayarit and coincides with a gravimetric minimum. We identify several high amplitude reflectors interpreted as mafic sills, which become more abundant toward the south. At least part of them can be correlated with the widespread mafic volcanism emplaced at 9–12 Ma along the eastern margin of the Gulf of California rift. In the northern and central sectors we identified three main stratigraphic boundaries (L1, L2, and L3) within the basin filling, which define seismo-stratigraphic sequences. The shallower sequences, limited by the L1 and L2 boundaries and attributed to the Pleistocene and part of the Pliocene, lack evidence of significant deformation. The sequence above L3 boundary, can be assigned to the earliest Pliocene and the Miocene since they are intruded by a ~ 10 Ma basaltic sill cut by the Huichol-1 exploratory well. The lower part of the basin is characterized by high amplitude reflectors that pinches out against the acoustic basement and correspond to volcanic tuffs and sedimentary deposits correlative with the lower member of the Comondú group exposed in Baja California, which includes ~23 to ~19 Ma distal part of ignimbrites sourced from the Sierra Madre Occidental in Nayarit. Faults with the most significant displacements have a listric geometry and dip from the E to NE. The maximum sediment thickness reported in the Huichol-1 well is 2800 m, with a two-way travel time of 2.7 s, but it reaches 3.7 TWTT in some areas. Based on sedimentation rates, the minimum age for the onset of sedimentation in the basin is ~19 Ma, which is consistent with the regional tectonic evolution of the margin.

中文翻译：

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墨西哥加利福尼亚湾东南部马萨特兰盆地的地下结构，来自地震反射和井数据

由于大陆架以及锡那罗亚州和纳亚里特州沿海地区的厚沉积层覆盖，加利福尼亚湾东南部裂谷边缘的结构仅部分为人所知。在此，我们报告了马萨特兰盆地的地下结构和可能年龄，该盆地是最大的埋藏盆地之一，基于对多道二维反射地震剖面再处理的解释以及墨西哥石油公司 (PEMEX) 在 1979 年至 1980 年间钻探的一口探井的解释。作为重量数据。马萨特兰盆地位于里维拉板块活跃俯冲带以北，以及自上新世以来在海湾口增生的新洋壳以西。该盆地的西边以特雷斯马里亚斯群岛中暴露的晚白垩世岩基高点和纳亚里特海槽的正断层为界，东边以渐新世晚期至中新世早期的伸展断层为界，西马德雷山脉为界。根据地震剖面特征，盆地可分为三个主要扇区。北部和中部地区之间的过渡是由基底的突然加深来定义的，这对应于 ENE-WSW 趋势的住宿区向西延伸，分隔了西马德雷山脉的相对倾斜区域。声学基底在中央区域由一组高振幅反射器清晰界定，表明火成岩起源。盆地最深处位于纳亚里特沿海平原，与重力最小值重合。我们发现了几个被解释为镁铁质基岩的高振幅反射体，这些反射体向南变得更加丰富。至少其中一部分可以与加利福尼亚湾裂谷东缘 9-12 Ma 广泛分布的镁铁质火山活动相关。在北部和中部地区，我们确定了盆地充填物内的三个主要地层边界（L1、L2 和 L3），它们定义了地震地层序列。较浅的层序受 L1 和 L2 边界限制，属于更新世和部分上新世，缺乏明显变形的证据。 L3 边界以上的层序可归属于最早的上新世和中新世，因为它们被 Huichol-1 探井切割的约 10 Ma 玄武岩基台侵入。盆地下部的特点是高振幅反射体在声学基底上尖灭，对应于火山凝灰岩和沉积物，与下加利福尼亚州暴露的 Comondú 群下部成员相关，其中包括 ~23 至 ~19 Ma 远端部分来自纳亚里特州西马德雷山脉的凝灰岩。位移最显着的断层呈列表状几何形状，倾角从 E 向 NE。 Huichol-1井报道的最大沉积物厚度为2800 m，双向走时时间为2.7 s，但在某些地区达到3.7 TWTT。根据沉积速率，盆地内沉积起始的最小年龄为~19 Ma，这与边缘的区域构造演化相一致。