Both magmatic and tectonic processes contribute to the formation of volcanic continental margins. Such margins are thought to undergo extension across a narrow zone of lithospheric thinning (~100 km). New observations based on existing and reprocessed data from the Eastern North American Margin contradict this hypothesis. With ~64,000 km of 2‐D seismic data tied to 40 wells combined with published refraction, deep reflection, receiver function, and onshore drilling efforts, we quantified along‐strike variations in the distribution of rift structures, magmatism, crustal thickness, and early post‐rift sedimentation under the shelf of Baltimore Canyon Trough (BCT), Long Island Platform, and Georges Bank Basin (GBB). Results indicate that BCT is narrow (80–120 km) with a sharp basement hinge and few rift basins. The seaward dipping reflectors (SDR) there extend ~50 km seaward of the hinge line. In contrast, the GBB is wide (~200 km), has many syn‐rift structures, and the SDR there extend ~200 km seaward of the hinge line. Early post‐rift depocenters at the GBB coincide with thinner crust suggesting “uniform” thinning of the entire lithosphere. Models for the formation of volcanic margins do not explain the wide structure of the GBB. We argue that crustal thinning of the BCT was closely associated with late syn‐rift magmatism, whereas the broad thinning of the GBB segment predated magmatism. Correlation of these variations to crustal terranes of different compositions suggests that the inherited rheology determined the premagmatic response of the lithosphere to extension.

中文翻译：

---

前岩浆裂谷在塑造火山大陆边缘上的作用：以北美东部边缘为例

岩浆和构造过程都有助于火山大陆边缘的形成。这种边缘被认为在岩石圈变薄的狭窄区域（〜100 km）内扩展。基于现有的和经过重新处理的来自北美东部边缘的数据的新观察结果与这一假设相矛盾。利用与40口井相关的〜64,000 km的二维地震数据，结合已发表的折射，深反射，接收器功能和陆上钻探成果，我们量化了裂谷构造分布，岩浆作用，地壳厚度和早期地震沿走向的变化巴尔的摩峡谷槽（BCT），长岛平台和乔治银行盆地（GBB）架下的裂谷后沉积。结果表明，BCT狭窄（80-120 km），具有尖锐的基底铰链和少量裂谷盆。那里的向海浸入式反射器（SDR）沿铰链线向海延伸约50公里。相比之下，GBB宽（约200 km），具有许多同线结构，那里的SDR扩展了铰链线向海约200公里。GBB裂谷后的早期震中与薄壳相吻合，表明整个岩石圈“均匀”变薄。火山边缘形成的模型不能解释GBB的广泛结构。我们认为BCT的地壳变薄与晚期同裂谷岩浆作用密切相关，而GBB段的广泛变薄早于岩浆作用。这些变化与不同成分的地壳的相关性表明，继承的流变学决定了岩石圈对伸展的前岩浆反应。