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Neogene evolution of the margin adjacent to the La Plata River Delta (Pelotas Basin): Sedimentary pathways and the origins of the Rio Grande Cone
Basin Research ( IF 2.8 ) Pub Date : 2024-02-01 , DOI: 10.1111/bre.12848 Gabriel Tagliaro 1 , Adolfo Britzke 2 , Mateus A. C. Gama 2 , Pedro Bauli 2 , André P. Negrão 2 , Luigi Jovane 1
Basin Research ( IF 2.8 ) Pub Date : 2024-02-01 , DOI: 10.1111/bre.12848 Gabriel Tagliaro 1 , Adolfo Britzke 2 , Mateus A. C. Gama 2 , Pedro Bauli 2 , André P. Negrão 2 , Luigi Jovane 1
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Continental margins that exhibit high terrigenous input are generally located near deltas that are capable of transporting large quantities of sediments into the basin. However, in rare cases, high terrigenous sedimentation occurs in regions deprived of major riverine systems where the sedimentary pathway is enigmatic. One such case is the Neogene of the Pelotas Basin of Brazil and Uruguay, adjacent to the La Plata River mouth. Since the Miocene, anomalous sedimentation formed a giant progradational wedge, the Rio Grande Cone, one of the largest submarine fan-like features on Earth. To understand the Neogene evolution of the margin and the origins of the Rio Grande Cone, here we present a seismic-stratigraphic framework based on well-logs and 2D seismic data. Three depositional environments are identified: (1) on the shelf, upper Miocene to Pliocene fluvial channels delivered sand deposits on the mud-dominated shelf; (2) on the slope, sediment instability resulted in structural deformation and multiple phases of mass transport deposition and (3) on the lower slope and basin floor, large contourite drifts formed by sediment reworking. We classify the Rio Grande Cone as a megaslide complex, due to its depositional and structural setting. Local deltaic systems were active on the shelf in the Neogene, but the limited size of their paleo-drainage systems in comparison to the volume of sedimentation in the margin suggests that an additional sedimentary pathway existed. In this sense, the demise of an epicontinental sea over the La Plata Basin during the Neogene likely enabled the input of large volumes of fine sediments into the margin, via the La Plata plume water. We suggest that the desiccation of this epicontinental sea and the intensification of ocean currents since the middle Miocene explains the anomalous Neogene terrigenous influx into the SW Atlantic margin.
中文翻译：
拉普拉塔河三角洲（佩洛塔斯盆地）附近边缘的新近纪演化：沉积路径和格兰德锥体的起源
表现出高陆源输入的大陆边缘通常位于能够将大量沉积物输送到盆地的三角洲附近。然而，在极少数情况下，高度的陆源沉积发生在缺乏主要河流系统的地区，这些地区的沉积路径是神秘的。其中一个例子是巴西和乌拉圭佩洛塔斯盆地的新近纪，毗邻拉普拉塔河口。自中新世以来，异常沉积形成了一个巨大的进积楔，即格兰德锥体，这是地球上最大的海底扇状特征之一。为了了解边缘的新近纪演化和格兰德锥体的起源，我们在这里提出了一个基于测井和二维地震数据的地震地层框架。确定了三种沉积环境：（1）在陆架上，上中新世至上新世的河流河道在以泥为主的陆架上输送了砂沉积物； （2）在斜坡上，沉积物不稳定导致结构变形和多期物质输送沉积；（3）在下部斜坡和盆地底部，沉积物改造形成大型等高线漂移。由于其沉积和结构环境，我们将格兰德锥体归类为大型滑坡复合体。新近纪大陆架上的局部三角洲系统很活跃，但与边缘的沉积量相比，其古排水系统的规模有限，表明存在额外的沉积通道。从这个意义上说，新近纪期间拉普拉塔盆地上陆缘海的消亡可能使大量细小的沉积物通过拉普拉塔羽流水输入到边缘。我们认为，自中新世中期以来，陆缘海的干燥和洋流的加强解释了新近纪陆源异常流入西南大西洋边缘的原因。
更新日期：2024-02-02
中文翻译：
拉普拉塔河三角洲（佩洛塔斯盆地）附近边缘的新近纪演化：沉积路径和格兰德锥体的起源
表现出高陆源输入的大陆边缘通常位于能够将大量沉积物输送到盆地的三角洲附近。然而，在极少数情况下，高度的陆源沉积发生在缺乏主要河流系统的地区，这些地区的沉积路径是神秘的。其中一个例子是巴西和乌拉圭佩洛塔斯盆地的新近纪，毗邻拉普拉塔河口。自中新世以来，异常沉积形成了一个巨大的进积楔，即格兰德锥体，这是地球上最大的海底扇状特征之一。为了了解边缘的新近纪演化和格兰德锥体的起源，我们在这里提出了一个基于测井和二维地震数据的地震地层框架。确定了三种沉积环境：（1）在陆架上，上中新世至上新世的河流河道在以泥为主的陆架上输送了砂沉积物； （2）在斜坡上，沉积物不稳定导致结构变形和多期物质输送沉积；（3）在下部斜坡和盆地底部，沉积物改造形成大型等高线漂移。由于其沉积和结构环境，我们将格兰德锥体归类为大型滑坡复合体。新近纪大陆架上的局部三角洲系统很活跃，但与边缘的沉积量相比，其古排水系统的规模有限，表明存在额外的沉积通道。从这个意义上说，新近纪期间拉普拉塔盆地上陆缘海的消亡可能使大量细小的沉积物通过拉普拉塔羽流水输入到边缘。我们认为，自中新世中期以来，陆缘海的干燥和洋流的加强解释了新近纪陆源异常流入西南大西洋边缘的原因。
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