当前位置:
X-MOL 学术
›
Mar. Petrol. Geol.
›
论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Origin, composition and relative timing of seaward dipping reflectors on the Pelotas rifted margin
Marine and Petroleum Geology ( IF 4.2 ) Pub Date : 2020-04-01 , DOI: 10.1016/j.marpetgeo.2020.104235 Caroline Harkin , Nick Kusznir , Alan Roberts , Gianreto Manatschal , Brian Horn
Marine and Petroleum Geology ( IF 4.2 ) Pub Date : 2020-04-01 , DOI: 10.1016/j.marpetgeo.2020.104235 Caroline Harkin , Nick Kusznir , Alan Roberts , Gianreto Manatschal , Brian Horn
Abstract The mechanism by which seaward dipping reflectors (SDRs) are formed is a topic of debate. Two contrasting models exist for their formation, the volcanic-faulting model and the volcanic-loading model. Each of these models has important implications for the processes which control the structure and formation of magma-rich rifted continental margins. We have examined high-quality deep-seismic reflection data across the Pelotas Basin, offshore Brazil. These data reveal a remarkable set of SDRs, for which we have investigated the likely nature of their formation. The total package of SDRs has an across-strike width of ~200 km and a variable vertical thickness of ~10–17 km, previously interpreted as volcanic flows. Detailed observations, however, show changes in seismic character and geometry within the SDR package, which suggest a complex and varied evolution. We have used gravity anomaly inversion and seismic observations together to investigate the likely composition of the SDRs by determining the proportion of basaltic material to sedimentary/volcaniclastic material (basalt fraction) within the SDRs. This has been achieved by minimising the difference between the depth of the gravity Moho and seismic Moho in order to quantify the lateral variation in basalt fraction, taken to be proportional to the bulk density of the package. The density of the SDR package together with seismic interpretation is then used to infer the composition, depositional environment, source and time of formation relative to breakup. Our analysis suggests that the overall SDR basalt fraction and bulk density decrease oceanwards, possibly due a change in the type of volcanic deposits from predominantly subaerial to volcaniclastics, possibly deposited subaqueously. The SDRs can be split into three sub-packages. The two inner SDR packages are interpreted to consist of lava flows sourced from syn-tectonic, subaerial eruptions, associated with the onshore Parana Large Igneous Province, flowing eastwards into an extensional basin. The outer SDR package shows reflector geometries that progressively offlap oceanwards, interpreted as extrusives sourced from an eastwards-migrating, newly formed ocean ridge. Our analysis suggests that both the volcanic-faulting and volcanic-loading models for SDR formation are applicable to the Pelotas rifted margin, recording distinct syn-rift and syn-breakup magmatic events. We show that both SDR formation models can be recognised in a naturally occurring example and can coexist on the same margin.
中文翻译:
Pelotas裂谷边缘向海倾角反射层的成因、组成和相对时间
摘要 向海倾角反射体 (SDR) 的形成机制是一个有争议的话题。它们的形成存在两种截然不同的模型,火山断层模型和火山加载模型。这些模型中的每一个都对控制富含岩浆的裂谷大陆边缘的结构和形成的过程具有重要意义。我们已经检查了巴西近海 Pelotas 盆地的高质量深地震反射数据。这些数据揭示了一组非凡的特别提款权,为此我们调查了它们形成的可能性质。SDR 的总包具有约 200 公里的横向宽度和约 10-17 公里的可变垂直厚度,以前被解释为火山流。然而,详细的观察显示了 SDR 包内地震特征和几何形状的变化,这表明了复杂而多样的演变。我们结合使用重力异常反演和地震观测,通过确定 SDR 中玄武岩物质与沉积/火山碎屑物质(玄武岩比例)的比例来研究 SDR 的可能组成。这是通过最小化重力莫霍面和地震莫霍面深度之间的差异来实现的,以便量化玄武岩分数的横向变化,与包装的体积密度成正比。然后使用 SDR 包的密度和地震解释来推断成分、沉积环境、形成的来源和相对于破裂的时间。我们的分析表明,整体 SDR 玄武岩比例和堆积密度向海洋方向降低,可能是由于火山沉积物的类型发生了变化,从主要是地下沉积到火山碎屑岩,可能沉积在水下。SDR 可以分为三个子包。两个内部 SDR 包被解释为包含源自同构造、地下喷发的熔岩流,与陆上巴拉那大火成岩省有关,向东流入伸展盆地。外部 SDR 包显示反射器几何形状逐渐向海洋外翻,解释为来自向东迁移的新形成的洋脊的喷出物。我们的分析表明,SDR 形成的火山断层和火山加载模型都适用于 Pelotas 裂谷边缘,记录了不同的同裂谷和同裂岩浆事件。
更新日期:2020-04-01
中文翻译:
Pelotas裂谷边缘向海倾角反射层的成因、组成和相对时间
摘要 向海倾角反射体 (SDR) 的形成机制是一个有争议的话题。它们的形成存在两种截然不同的模型,火山断层模型和火山加载模型。这些模型中的每一个都对控制富含岩浆的裂谷大陆边缘的结构和形成的过程具有重要意义。我们已经检查了巴西近海 Pelotas 盆地的高质量深地震反射数据。这些数据揭示了一组非凡的特别提款权,为此我们调查了它们形成的可能性质。SDR 的总包具有约 200 公里的横向宽度和约 10-17 公里的可变垂直厚度,以前被解释为火山流。然而,详细的观察显示了 SDR 包内地震特征和几何形状的变化,这表明了复杂而多样的演变。我们结合使用重力异常反演和地震观测,通过确定 SDR 中玄武岩物质与沉积/火山碎屑物质(玄武岩比例)的比例来研究 SDR 的可能组成。这是通过最小化重力莫霍面和地震莫霍面深度之间的差异来实现的,以便量化玄武岩分数的横向变化,与包装的体积密度成正比。然后使用 SDR 包的密度和地震解释来推断成分、沉积环境、形成的来源和相对于破裂的时间。我们的分析表明,整体 SDR 玄武岩比例和堆积密度向海洋方向降低,可能是由于火山沉积物的类型发生了变化,从主要是地下沉积到火山碎屑岩,可能沉积在水下。SDR 可以分为三个子包。两个内部 SDR 包被解释为包含源自同构造、地下喷发的熔岩流,与陆上巴拉那大火成岩省有关,向东流入伸展盆地。外部 SDR 包显示反射器几何形状逐渐向海洋外翻,解释为来自向东迁移的新形成的洋脊的喷出物。我们的分析表明,SDR 形成的火山断层和火山加载模型都适用于 Pelotas 裂谷边缘,记录了不同的同裂谷和同裂岩浆事件。