The relative contributions of astronomical forcing and tectonics to ocean anoxia in the Cretaceous are unclear. This study establishes the pacing of Late Cretaceous black cherts and shales. We present a 6-million-year astrochronology from the Furlo and Bottaccione sections in Italy that spans the Cenomanian–Turonian transition and OAE2. Together with a new radioisotopic age for the mid-Cenomanian event, we show that astronomical forcing determined the timing of these carbon cycle perturbations.
This study focuses on the impact of major rift border faults on fluid circulation and hanging wall sediment diagenesis by investigating a well-exposed example in NE Greenland using field observations, U–Pb calcite dating, clumped isotope, and minor element analyses. We show that fault-proximal sediments became calcite cemented quickly after deposition to form a near-impermeable barrier along the fault, which has important implications for border fault zone evolution and reservoir assessments.
This paper presents a numerical method for restoring models of the subsurface to a previous state in their deformation history, acting as a numerical time machine for geological structures. The method relies on the assumption that rock layers can be modeled as highly viscous fluids. It shows promising results on simple setups, including models with faults and non-flat topography. While issues still remain, this could open a way to add more physics to reverse time structural modeling.
The aim of this paper is to describe, evaluate and develop a simple but robust low-cost method for capturing 2-D fracture network data in GIS and make them more accessible to a broader range of users in both academia and industry. We present a breakdown of the key steps in the methodology, which provides an understanding of how to avoid error and improve the accuracy of the final dataset. The 2-D digital method can be used to interpret traces of 2-D linear features on a wide variety of scales.
Nicolas E. Beaudoin, Aurélie Labeur, Olivier Lacombe, Daniel Koehn, Andrea Billi, Guilhem Hoareau, Adrian Boyce, Cédric M. John, Marta Marchegiano, Nick M. Roberts, Ian L. Millar, Fanny Claverie, Christophe Pecheyran, and Jean-Paul Callot
This paper reports a multiproxy approach to reconstruct the depth, timing, and extent of the past fluid flow during the formation of a fold-and-thrust belt in the Northern Apennines, Italy. The unique combination of paleopiezometry and absolute dating returns the absolute timing of the sequence of deformation. Combined with burial models, this leads to predict the expected temperatures for fluid, highlighting a limited hydrothermal fluid flow we relate to the large-scale subsurface geometry.
At the St. Johns Dome, Arizona, CO2 naturally occurs in the subsurface, but there are travertine rocks on the surface which are an expression of CO2 leakage to the surface. These travertine deposits occur along faults, zones where the rock layers are fractured and displaced. In our research, we use geomechanical analysis to show that the CO2 leakage occurs at points where the faults are likely to be permeable due to the orientation of the geological stress field in the subsurface.
In carbonate rocks, fault zones influence the fluid flows and lead to important diagenetic processes modifying reservoir properties. The aim of this study is to identify the impact of two polyphase fault zones on fluid flows and reservoir properties during basin history. We determined petro-physic and diagenetic properties on 92 samples. This study highlights that fault zones acted as drains at their onset and induced fault zone cementation, which has strongly altered local reservoir properties.
When carbon dioxide is introduced into the subsurface it will migrate upwards and can encounter faults, which, depending on their hydrogeological properties and composition, can form barriers or pathways for the migrating fluid. We analyse uncertainties associated with these properties in order to better understand the implications for the retention of CO2 in the subsurface. We show that faults that form seals for other fluids may not be seals for CO2, which has implications for storage sites.
Physical properties of layered sedimentary rocks affect nucleation and propagation of discontinuities therein. Fractures developing through sedimentary sequences characterized by the alternation of strong and weak layers are strongly deviated along their track at layers’ boundaries, and depending on the layer they cross-cut, they show very thick (strong layers) or very thin (weak layers) infills of precipitated minerals, potentially representing pathways for ore deposits and oil/water resources.
In this paper we present an original multidisciplinary workflow involving various tools (e.g., seismic profiles, satellite images, well logs) and techniques (e.g., photogeology, seismic interpretation, well correlation, geophysics, geochronology, backstripping) as a basis for discussing the potential factors controlling the tectono-stratigraphic architecture within the Palaeozoic intracratonic basins of the Saharan Platform using the Reggane, Ahnet, Mouydir and Illizi basins as examples.
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The anisotropy of magnetic susceptibility (AMS) technique provides an effective way to interpret deforming mountain belts. In both the Betics, Spain, and Apennines, Italy, weak but well-organized AMS fabrics were recovered from young unconsolidated and unburied rocks that could not be analyzed with more traditional methods. Collectively, these studies demonstrate the novel ways that AMS can be combined with other data to resolve earthquake hazards in space and time.
The anisotropy of magnetic susceptibility (AMS) technique provides an effective way to interpret...