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Kinematics and extent of the Piemont–Liguria Basin – implications for subduction processes in the Alps
Solid Earth ( IF 3.4 ) Pub Date : 2021-04-21 , DOI: 10.5194/se-12-885-2021 Eline Le Breton , Sascha Brune , Kamil Ustaszewski , Sabin Zahirovic , Maria Seton , R. Dietmar Müller
Solid Earth ( IF 3.4 ) Pub Date : 2021-04-21 , DOI: 10.5194/se-12-885-2021 Eline Le Breton , Sascha Brune , Kamil Ustaszewski , Sabin Zahirovic , Maria Seton , R. Dietmar Müller
Assessing the size of a former ocean of which only remnants are found in mountain belts is challenging but crucial to understanding subduction and exhumation processes. Here we present new constraints on the opening and width of the Piemont–Liguria (PL) Ocean, known as the Alpine Tethys together with the Valais Basin. We use a regional tectonic reconstruction of the Western Mediterranean–Alpine area, implemented into a global plate motion model with lithospheric deformation, and 2D thermo-mechanical modeling of the rifting phase to test our kinematic reconstructions for geodynamic consistency. Our model fits well with independent datasets (i.e., ages of syn-rift sediments, rift-related fault activity, and mafic rocks) and shows that, between Europe and northern Adria, the PL Basin opened in four stages: (1) rifting of the proximal continental margin in the Early Jurassic (200–180 Ma), (2) hyper-extension of the distal margin in the Early to Middle Jurassic (180–165 Ma), (3) ocean–continent transition (OCT) formation with mantle exhumation and MORB-type magmatism in the Middle–Late Jurassic (165–154 Ma), and (4) breakup and mature oceanic spreading mostly in the Late Jurassic (154–145 Ma). Spreading was slow to ultra-slow (max. 22 mm yr−1, full rate) and decreased to ∼51 mm yr−1 after 145 Ma while completely ceasing at about 130 Ma due to the motion of Iberia relative to Europe during the opening of the North Atlantic. The final width of the PL mature (“true”) oceanic crust reached a maximum of 250 km along a NW–SE transect between Europe and northwestern Adria. Plate convergence along that same transect has reached 680 km since 84 Ma (420 km between 84–35 Ma, 260 km between 35–0 Ma), which greatly exceeds the width of the ocean. We suggest that at least 63 % of the subducted and accreted material was highly thinned continental lithosphere and most of the Alpine Tethys units exhumed today derived from OCT zones. Our work highlights the significant proportion of distal rifted continental margins involved in subduction and exhumation processes and provides quantitative estimates for future geodynamic modeling and a better understanding of the Alpine Orogeny.
中文翻译:
皮埃蒙特-利古里亚盆地的运动学和范围–对阿尔卑斯俯冲过程的影响
评估仅在山脉带中发现残留物的前海洋的规模具有挑战性,但对于理解俯冲和掘尸过程至关重要。在这里,我们对皮埃蒙特-利古里亚(PL)海洋(称为高山特提斯)和瓦莱州盆地的开放和宽度提出了新的限制。我们使用地中海西部-高山地区的区域构造重建,将其实施为具有岩石圈变形的全球板块运动模型,以及裂陷阶段的2D热力学模型,以测试我们的运动学重建的地球动力学一致性。我们的模型非常适合独立的数据集(例如,同裂谷沉积物的年龄,与裂谷有关的断层活动和镁铁质岩石),并表明,在欧洲和阿德里亚北部之间,PL盆地分四个阶段开放:(1)侏罗纪早期(200–180 Ma)近海大陆边缘裂谷,(2)侏罗纪早期至中侏罗纪(180–165 Ma)远侧边缘超伸,(3)海洋-大陆过渡侏罗纪中晚期(165-154 Ma)地幔发掘和MORB型岩浆作用(OCT)形成,以及(4)侏罗纪晚期(154-145 Ma)的破裂和成熟的海洋扩散。传播速度从慢到极慢(最高22 毫米yr -1(全速率)并降低至〜5 1 毫米yr -1在北大西洋开放期间,由于伊比利亚相对于欧洲的运动而在145 Ma之后停止,而在130 Ma左右完全停止。PL成熟(“真”)大洋壳的最终宽度沿欧洲和西北阿德里亚之间的西北-东南断面达到最大250公里。自84 Ma以来,沿同一横断面的板块汇聚已达到680 km(84-35 Ma之间为420 km,35-0 Ma之间为260 km),大大超过了海洋的宽度。我们建议,至少63%的俯冲和增生物质是高度变薄的大陆岩石圈,而今天挖掘出的大多数高山特提斯单元都来自OCT区。
更新日期:2021-04-21
中文翻译:
皮埃蒙特-利古里亚盆地的运动学和范围–对阿尔卑斯俯冲过程的影响
评估仅在山脉带中发现残留物的前海洋的规模具有挑战性,但对于理解俯冲和掘尸过程至关重要。在这里,我们对皮埃蒙特-利古里亚(PL)海洋(称为高山特提斯)和瓦莱州盆地的开放和宽度提出了新的限制。我们使用地中海西部-高山地区的区域构造重建,将其实施为具有岩石圈变形的全球板块运动模型,以及裂陷阶段的2D热力学模型,以测试我们的运动学重建的地球动力学一致性。我们的模型非常适合独立的数据集(例如,同裂谷沉积物的年龄,与裂谷有关的断层活动和镁铁质岩石),并表明,在欧洲和阿德里亚北部之间,PL盆地分四个阶段开放:(1)侏罗纪早期(200–180 Ma)近海大陆边缘裂谷,(2)侏罗纪早期至中侏罗纪(180–165 Ma)远侧边缘超伸,(3)海洋-大陆过渡侏罗纪中晚期(165-154 Ma)地幔发掘和MORB型岩浆作用(OCT)形成,以及(4)侏罗纪晚期(154-145 Ma)的破裂和成熟的海洋扩散。传播速度从慢到极慢(最高22 毫米yr -1(全速率)并降低至〜5 1 毫米yr -1在北大西洋开放期间,由于伊比利亚相对于欧洲的运动而在145 Ma之后停止,而在130 Ma左右完全停止。PL成熟(“真”)大洋壳的最终宽度沿欧洲和西北阿德里亚之间的西北-东南断面达到最大250公里。自84 Ma以来,沿同一横断面的板块汇聚已达到680 km(84-35 Ma之间为420 km,35-0 Ma之间为260 km),大大超过了海洋的宽度。我们建议,至少63%的俯冲和增生物质是高度变薄的大陆岩石圈,而今天挖掘出的大多数高山特提斯单元都来自OCT区。