{"title":"3D structure of subsurface thrusts in the eastern Jaca Basin, southern Pyrenees","authors":"P. Labaume, A. Teixell","doi":"10.1344/GEOLOGICAACTA2018.16.4.9","DOIUrl":null,"url":null,"abstract":"This paper presents a new model of the subsurface structure of the eastern Jaca flexural basin of the west-central southern Pyrenees, by means of subsurface structural maps and four new balanced cross-sections. The study is based on the interpretation of a set of publicly available seismic reflection profiles tied to deep exploration well logs, which constitute a unique database in the southern Pyrenees associated to the gas discovery of the Serrablo field. Investigation of the deep basin structure highlights strong mechanical-stratigraphic contrasts between basement, a competent Upper Cretaceous-Eocene carbonate sequence in the deep basin and a weak infill of Eocene to lower Miocene synorogenic clastic deposits. These contrasts promote the occurrence of various decollement levels and a decoupled style of deformation between intervals of different competence. A contour map for the top of basement reveals a complex structure with lateral variations of the number of thrusts and the displacement on these and local transverse elements. Between the Gavarnie thrust at the southern edge of the Axial Zone and the Guarga thrust at the leading edge of the \nbasement thrust system, three main other basement thrusts are defined below the north-eastern Jaca Basin, from South to North the Fiscal, Yesero and Broto thrusts. In the Meso-Cenozoic sedimentary cover, two low-angle thrusts are mapped in the subsurface across the Upper Cretaceous-Eocene carbonates: i) the deep Oturia thrust, connected upsection to the emerging Oturia thrust known at the surface, and ii) the deep Jaca thrust, drilled by the Serrablo wells, and connected to the emerging Jaca thrust and Yebra de Basa anticline through a zone of disharmonic deformation. The deduced subsurface geometrical relationships are consistent with the connection of the Gavarnie and Broto basement thrusts to the Priabonian-Rupelian Oturia and Jaca thrusts while the younger Yesero, Fiscal and Guarga basement thrusts emerge at the South Pyrenean thrust front of the Sierras Exteriores, active until the early Miocene. This study highlights the complex structural pattern that characterizes the deep structure of the South Pyrenean basin and the role of disharmonic deformation that challenges the resolution of the deeper thrust system without the help of seismic profiles.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":null,"pages":null},"PeriodicalIF":1.3000,"publicationDate":"2018-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"18","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geologica Acta","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1344/GEOLOGICAACTA2018.16.4.9","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOLOGY","Score":null,"Total":0}
引用次数: 18
Abstract
This paper presents a new model of the subsurface structure of the eastern Jaca flexural basin of the west-central southern Pyrenees, by means of subsurface structural maps and four new balanced cross-sections. The study is based on the interpretation of a set of publicly available seismic reflection profiles tied to deep exploration well logs, which constitute a unique database in the southern Pyrenees associated to the gas discovery of the Serrablo field. Investigation of the deep basin structure highlights strong mechanical-stratigraphic contrasts between basement, a competent Upper Cretaceous-Eocene carbonate sequence in the deep basin and a weak infill of Eocene to lower Miocene synorogenic clastic deposits. These contrasts promote the occurrence of various decollement levels and a decoupled style of deformation between intervals of different competence. A contour map for the top of basement reveals a complex structure with lateral variations of the number of thrusts and the displacement on these and local transverse elements. Between the Gavarnie thrust at the southern edge of the Axial Zone and the Guarga thrust at the leading edge of the
basement thrust system, three main other basement thrusts are defined below the north-eastern Jaca Basin, from South to North the Fiscal, Yesero and Broto thrusts. In the Meso-Cenozoic sedimentary cover, two low-angle thrusts are mapped in the subsurface across the Upper Cretaceous-Eocene carbonates: i) the deep Oturia thrust, connected upsection to the emerging Oturia thrust known at the surface, and ii) the deep Jaca thrust, drilled by the Serrablo wells, and connected to the emerging Jaca thrust and Yebra de Basa anticline through a zone of disharmonic deformation. The deduced subsurface geometrical relationships are consistent with the connection of the Gavarnie and Broto basement thrusts to the Priabonian-Rupelian Oturia and Jaca thrusts while the younger Yesero, Fiscal and Guarga basement thrusts emerge at the South Pyrenean thrust front of the Sierras Exteriores, active until the early Miocene. This study highlights the complex structural pattern that characterizes the deep structure of the South Pyrenean basin and the role of disharmonic deformation that challenges the resolution of the deeper thrust system without the help of seismic profiles.
本文利用地下构造图和4个新的平衡剖面,建立了比利牛斯山脉中西部东部雅卡弯曲盆地的地下构造新模式。该研究基于对一组公开可用的地震反射剖面的解释,这些剖面与深部勘探测井相关联,构成了与Serrablo气田天然气发现相关的比利牛斯山脉南部独特的数据库。对深盆构造的研究表明,深盆的基底、上白垩统—始新统碳酸盐岩层序与始新统—下中新统同造碎屑沉积的弱充填之间存在强烈的机械地层对比。这些对比促进了不同沉降水平的发生和不同能力区间间变形的解耦样式。基底顶部的等高线图揭示了一个复杂的构造,其中逆冲断层的数量以及这些断层和局部横向元素上的位移都有横向变化。在轴向带南缘的加瓦尼逆冲和基底逆冲系统前缘的瓜尔加逆冲之间,在雅卡盆地东北部可划分出3个主要的基底逆冲,由南至北为Fiscal逆冲、Yesero逆冲和Broto逆冲。在中新生代沉积盖层中,在上白垩统-始新统碳酸盐岩中,在地下绘制了两个低角度逆冲断层:1)深Oturia逆冲断层,与地表已知的新兴Oturia逆冲断层上切相连;2)深Jaca逆冲断层,由Serrablo井钻探,通过非协调变形带与新兴Jaca逆冲断层和Yebra de Basa背斜相连。推断出的地下几何关系与加瓦尼和布罗托基底逆冲与普里阿伯尼亚-鲁佩利亚-奥图里亚和雅克逆冲的联系一致,而更年轻的耶塞罗、财政和瓜尔加基底逆冲出现在外山脉的南比利牛斯逆冲前缘,一直活跃到中新世早期。该研究强调了南比利牛斯盆地深层构造的复杂构造模式,以及非调和变形的作用,这对没有地震剖面帮助的深层冲断系统的分辨率提出了挑战。
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