The chronology and rotational kinematics in the South-Eastern Jaca Basin (Southern Pyrenees): Las Bellostas section

IF 1.3 4区 地球科学 Q2 GEOLOGY
Emilio L. Pueyo, A. Rodríguez-Pintó, J. Serra-Kiel, A. Barnolas
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引用次数: 1

Abstract

Despite the large number of magnetostratigraphic studies in the South Pyrenean Basin aiming to calibrate the basin chronostratigraphy and the biostratigraphic scales, the South Eastern Jaca Basin remains unexplored from this perspective, and its relation with the Ainsa Basin is not fully understood. In this work we contribute with new magnetostratigraphic data from the 950m thick Las Bellostas section, located in the northern hinge of the Balzes anticline. Well-proven primary signal (positive fold test and two pseudo-antiparallel polarities) supported by numerous primary data in the surroundings allow us building a reliable local polarity sequence of eight magnetozones (from R1 to N4). Additionally, seven new biostratigraphic samples (Nummulites and Assilina) in the lower part of the section (marine environment) allows tightening the section to the Geomagnetic Polarity Time Scale (GPTS) and proposing a refined age model for the southeastern Jaca Basin. The section starts in the Boltaña Fm., of Cuisian age (Shallow Benthic Zone, SBZ11), is followed by a sedimentary gap from C22n to C20n as witnessed by biostratigraphic data (SBZ11 underneath the hiatus and SBZ16 just atop). The deltaic Sobrarbe Fm. can be tracked until the C19n (Late Lutetian). From this point (200m) until the top of the section (950m), at least, the entire C18n chron can be recognized within the molassic Campodarbe Fm. (C18n.2n-C18n.1r and C18n.1n) (Bartonian) equivalent to the West to the prodeltaic Arguis marls Fm. The Middle Cusian (SBZ11) to Middle Lutetian (SBZ15) stratigraphic hiatus is, in part, enhanced by the structural position at the hinge of the Balzes anticline. These new chronostratigraphic constraints help refining the W-E and N-S stratigraphic relationships in the eastern Jaca Basin and in the Ainsa Basin. This section also allows us to accurately refine the kinematics of the rotational activity in the eastern External Sierras. The important difference in magnetic declination along the section and neighboring paleomagnetic data from the Balzes anticline (from ≈70º clockwise at the base of the stratigraphic section to non-significant at the top) together with the new age model for the Eastern Jaca Basin help characterizing the rotational activity of the Balzes thrust sheet. The rotation took place between chrons C20r (Middle Lutetian; 45Ma) and C17 (Lower Priabonian 37-38Ma) in agreement to nearby structures (Boltaña, Picodel Aguila anticlines) but clearly diachronic to western ones (Santo Domingo anticline). Besides, the rotational activity seems to follow a linear and continuous pattern (velocity 9-11º/Ma, R: 0.83-0.96) in contrast to closer structures that show two distinct rotational velocities (i.e. Boltaña). These new data still let open the debate on the rotational kinematics along the South Pyrenean basal thrust.
Jaca盆地东南部(比利牛斯山脉南部)的年表和旋转运动学:Las Bellostas剖面
尽管在南比利牛斯盆地进行了大量的磁地层学研究,旨在校准盆地年代地层学和生物地层学规模,但从这个角度来看,东南部的贾卡盆地仍未被勘探,其与安萨盆地的关系也未被完全了解。在这项工作中,我们提供了950米厚的Las Bellostas剖面的新磁地层学数据,该剖面位于Balzes背斜的北部铰链。周围环境中的大量原始数据支持的经过充分验证的原始信号(正折叠测试和两个伪反平行极性)使我们能够构建八个磁带(从R1到N4)的可靠局部极性序列。此外,该剖面下部(海洋环境)的七个新的生物地层样本(Nummulites和Assilina)使该剖面能够缩小到地磁极性时间尺度(GPTS),并提出了雅卡盆地东南部的精细年龄模型。该剖面始于Cuisian时代的Boltaña组(浅海底带,SBZ11),随后是从C22n到C20n的沉积间隙,如生物地层学数据所示(SBZ11位于裂孔下方,SBZ16位于顶部)。三角洲Sobrarbe组可以追踪到C19n(晚卢泰期)。从这一点(200米)到剖面顶部(950米),至少可以在相当于西部到前三角洲Arguis泥灰岩组的molassic Campodarbe组(C18n.2n-C18n.1r和C18n.1n)(Bartonian)内识别整个C18n时间段,巴尔茨背斜铰链处的构造位置增强了这一点。这些新的年代地层约束有助于完善Jaca盆地东部和Ainsa盆地的W-E和N-S地层关系。本节还使我们能够准确地完善外部Sierras东部旋转活动的运动学。沿剖面的磁偏角和Balzes背斜的邻近古地磁数据的重要差异(从地层剖面底部的顺时针≈70º到顶部的不显著),以及东部Jaca盆地的新年龄模型,有助于表征Balzes逆冲片的旋转活动。旋转发生在C20r(中卢泰阶;45Ma)和C17(下普里亚博阶37-38Ma)之间,与附近的构造(Boltaña、Picodel-Aguila背斜)一致,但与西部构造(圣多明各背斜)明显具有历时性。此外,旋转活动似乎遵循线性和连续的模式(速度9-11º/Ma,R:0.83-0.96),而较近的结构显示出两种不同的旋转速度(即Boltaña)。这些新数据仍然开启了关于南比利牛斯基底逆冲断层旋转运动学的争论。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Geologica Acta
Geologica Acta 地学-地质学
CiteScore
2.50
自引率
6.70%
发文量
13
审稿时长
>12 weeks
期刊介绍: - Relevant conceptual developments in any area of the Earth Sciences. - Studies presenting regional synthesis. - Thematic issues or monographic volumes presenting the results from one or more research groups. - Short papers reflecting interesting results or works in progress. - Contributions and results from Research Projects, Workshops, Symposiums, Congresses and any relevant scientific activity related to Earth Sciences. - Geologica Acta aims to stimulate rapid diffusion of results and efficient exchange of ideas between the widespread communities of Earth Science researchers (with special emphasis on Latinamerica, the Caribbean, Europe, the Mediterranean
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