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Tectonic inversion in the Santa Barbara System of the central Andean foreland thrust belt, northwestern Argentina
Get PDFThe Santa Barbara System (SBS) of northern Argentina is a 400 km long segment of the Subandean foreland thrust belt. It is characterized by predominantly west verging, relatively high-angle thrust faults. Many of these faults are reactivated normal faults from one branch of a complex Cretaceous to Paleogene rift system. Heteroaxial folding in parts of the SBS is probably due to a slight component of range-parallel dextral strike-slip motion acting on preexisting faults striking north and NE during inversion. Regional balanced cross sections along two transects across the northern SBS indicate that the major faults flatten into a detachment in the basement at about 10 km depth. Neogene E-W contraction in the SBS is of the order of 21-26 km. Rift extension is not very well constrained but was probably less than 10 km. The structural style of the SBS differs from the thin-skinned Subandean thrust belt to the north and from the large-wavelength Sierras Pampeanas basement uplifts to the south. The changes between the different styles are sharp and coincide with the northern and southern boundaries of the rift in the foreland, suggesting that crustal or lithospheric heterogeneities exert an overriding control on foreland structural style.Fil: Kley, Jonas. Universität Karlsruhe. Institut Geologisches; AlemaniaFil: Monaldi, Cesar Ruben. Universidad Nacional de Salta; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta; Argentin
Preserved extensional structures in an inverted Cretaceous rift basin, northwestern Argentina: Outcrop examples and implications for fault reactivation
Get PDFDuring the Cretaceous-Eocene interval a system of intracontinental rift basins, the Salta group rift, evolved in northwestern Argentina. Individual segments of the rift later suffered different degrees of inversion during Cenozoic shortening. The Tres Cruces subbasin, on the west side of the Eastern Cordillera, was strongly deformed, being now part of a thick-skinned thrust belt with a predominantly N-S structural trend. On its eastern border, tilting due to folding and thrusting and subsequent erosion have produced exceptional outcrops of preserved east-trending extensional structures including half grabens, rollover anticlines, and extensional fault-propagation folds. Farther west, the synrift succession is only intermittently exposed, although the interference of north- and east-trending structures as well as peculiar, dome-shaped anticlines with spur-like extensions suggest that north-and east-trending Cretaceous faults were reactivated, particularly near their intersections. Compilation of published data and analysis of our new data focused on the Salta rift indicates three main factors favoring the contractional reactivation of normal faults: dip angles lower than approximately 60°, especially for faults striking roughly normal to contraction; strikes no closer to the contraction direction than approximately 30°; and low downdip fault curvatures. Occasional dip-slip reactivation of east-trending faults does not match the present and long-term Andean stress regimes and presents an unresolved problem.Fil: Monaldi, Cesar Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Salta; ArgentinaFil: Salfity, Jose Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Salta; ArgentinaFil: Kley, Jonas. Universitat Jena; Alemani
"Saxonian tectonics" in the 21st century
No full textThis paper deals with the German term "Saxonische Tektonik" (Saxonian tectonics) and problems related to it. These are specific to the German geoscience literature and community - that is why this paper is written in German. The term was coined in the early 20th century and came to describe essentially all deformation that had taken place in Central Europe and parts of Western Europe from Triassic time to the present. It is today understood that this deformation comprises a protracted history of extension and graben evolution from Triassic to Early Cretaceous time, followed by one or several pulses of contraction and inversion in the Late Cretaceous to Palaeogene. Both extensional and contractional structures are often strongly modified by salt movement. Renewed extension from Eocene time onward created the European rift system. Originally, the characteristic inversion-related style of many Mesozoic "Saxonian" structures was called "Bruchfaltentektonik" ("fracture-fold tectonics"). Both terms linger to the present day in the German literature, despite no longer being adequate to our knowledge of changing tectonic regimes, their sequence over time, and the control exerted on specific structural styles by stratigraphy, lithology and the thermal and tectonic history. I therefore propose to abandon the terms "Saxonische Tektonik" and "Bruchfaltentektonik" for good. Nevertheless, many of the articles in which the original concepts were developed are still highly interesting to read. In particular those from the 1930s dealing with inversion tectonics - if under a still different name - anticipated later developments by some 50 years
Hans Stille in Göttingen
No full textHans Stille studied geology at the University of Göttingen from 1897 and received his Dr. phil. there in 1899. He returned to Göttingen in 1913 as ordinary professor of geology and palaeontology and held this position until following a call to Berlin in 1932. Stille’s scientific achievements in Göttingen begin with the recognition, during the field work for his doctoral thesis, of important pre-Cenozoic tectonic events which he later collectively termed “Saxonische Tektonik” (Saxonian tectonics). As a professor in Göttingen he published his chief work “Grundfragen der vergleichenden Tektonik” (Fundamental questions of comparative tectonics) in 1924. Stille’s idea of globally synchronous orogenic phases, although already introduced in his earlier publications, was summarized in this book and became extremely influential in the geological community worldwide. During his Göttingen years Stille earned a reputation as one of the leading geologists of his time. This is reflected in his appointment to Berlin where he joined pre-eminent scientists like Albert Einstein and Max Planck
Transition from basement‐involved to thin‐skinned thrusting in the Cordillera Oriental of southern Bolivia
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Seismic and field evidence for selective inversion of Cretaceous normal faults, Salta rift, northwest Argentina
Get PDFNorthwestern Argentina was the site of the continental Salta rift in Cretaceous to Paleogene time. The Salta rift had a complex geometry with several subbasins of different trends and subsidence patterns surrounding a central high. Fault trends in the rift were extremely variable. There is evidence of normal and/or transfer faults trending N, NE, E and SE. It is not clear if all these faults were active at the same time, indicating a poorly defined extension direction, or if they formed in different, non-coaxial extension phases. In either case, their trends were very likely influenced by preexisting fault systems. Beginning in early Eocene time, the rift basins were superseded by Andean foreland basins and later became caught in the Andean thrust deformation propagating eastward, resulting in the inversion of rift faults. Due to their different orientations, not all faults were equally prone to reactivation as thrusts. N to NNE trending faults were apparently most strongly inverted, probably often to a degree where the traces of their normal fault origin have become obliterated. We present seismic evidence of moderately inverted N trending faults in the Tres Cruces basin and field examples of preserved E trending normal faults. However, reactivation sometimes also affects faults trending approximately parallel to the main Neogene shortening direction, indicating short-term deviations from the general pattern of Neogene thrust deformation. These pulses of orogen-parallel contraction may be linked to the intermittent activity of oblique transfer zones.Fil: Kley, Jonas. Universitat Jena; AlemaniaFil: Rossello, Eduardo Antonio. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Monaldi, Cesar Ruben. Universidad Nacional de Salta; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Habighorst, Bjórn. Universität Karlsruhe; Alemani
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