Preprints
Filtering by Subject: Tectonics and Structure
Mechanical models to estimate the paleostress state from igneous intrusions
Published: 2018-03-09
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology
Dikes and sills represent an important component of the deformation history in volcanic systems, but unlike dikes, sills are typically omitted from traditional paleostress analyses in tectonic studies. The emplacement of sheet intrusions is commonly associated with mode I fracturing in a low deviatoric stress state, where dilation is perpendicular to the fracture plane. Many natural examples of [...]
Revisiting the crustal structure and kinematics of the Central Andes at 33.5°S : implications for the mechanics of Andean mountain-building
Published: 2018-03-02
Subjects: Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure
The Andean belt is the only present-day active case example of a subduction-type orogeny. However, an existing controversy opposes classical views of Andean growth as an east-verging retro-wedge, against a recently proposed bi-vergent model involving a primary west-vergent crustal-scale thrust synthetic to the subduction. We examine these diverging views by quantitatively re-evaluating the orogen [...]
Active deformation of Malawi Rift’s North Basin hinge zone modulated by reactivation of pre-existing Precambrian shear zone fabric
Published: 2018-02-19
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
Key Points: 1. Filtered aeromagnetic data elucidates the relationship between earthquake surface ruptures and buried faults along the North Basin hinge-zone, Malawi Rift. 2. Fault segments align with basement shear zone fabric. 3. Strain accommodation in the North Basin hinge zone is modulated by reactivation of the underlying Precambrian shear zone fabric. Abstract: We integrated temporal [...]
Fracture patterns associated with the evolution of the Teton anticline, Sawtooth Range, Montana, USA
Published: 2018-02-16
Subjects: Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure
The Teton anticline and adjacent structures at the deformation front of the Sawtooth Range fold-thrust belt in Montana are fractured in such a way that some have used these as a model for the fractures that propagate during buckle folding. However, advances in understanding both the process of folding in forelands and the evolution of fracture patterns found within these folds suggests that it [...]
Outcrop-scale tomography: insights into the 3D structure of multiphase boudins
Published: 2018-02-15
Subjects: Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure
We analyze the 3D geomorphology of a boudinaged amphibolite layer encased in marble using meter-scale tomography by serial sectioning, high resolution imaging and 3D reconstruction of a 2 m³ block from a quarry in the high-grade core of the Naxos core complex. Local uncertainties in the model are resolved by dissolution of marble in selected slabs, yielding a large, highly accurate 3D [...]
Overview to the Regional Thrust Wedge Tectonics in Indonesia: Similarities and Differences in Orogenic Belts
Published: 2018-02-06
Subjects: Earth Sciences, Geology, Geomorphology, Physical Sciences and Mathematics, Tectonics and Structure
Overview to the regional thrust wedge tectonics in Indonesia attempts to compile and review geologic settings related to the development of compressive structures. Comprehensive overview will be represented in six orogenic belts of various geologic settings: Langsa Fold-Thrust Belt (North Sumatra Basin), Banyumas Fold-Thrust Belt (Western Central Java), Kutei Basin, West Sulawesi Fold-Thrust Belt [...]
Rift-related magmatism influences petroleum systems development in the NE Irish Rockall Basin, offshore Ireland
Published: 2018-01-29
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology
Large volumes of hydrocarbons reside in volcanically influenced sedimentary basins. Despite having a good conceptual understanding of how magmatism impacts the petroleum system of such basins, we still lack detailed case studies documenting precisely how intrusive magmatism influences, for example, trap development and reservoir quality. Here we combine 3D seismic reflection, borehole, [...]
Detecting orogenic wedge state and the rise of the External Alps by detrital thermochronology
Published: 2018-01-26
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics, Tectonics and Structure
Critical taper theory permits the modelling of an orogenic wedge as a single mechanical entity. However, although shallow-crustal orogens dominated by brittle failure have been successfully modelled using critical taper, this remains controversial for major, ductile-failure-dominated orogens. In critical taper models, the steepness of the basal and upper orogenic surfaces defines the critical [...]
Salt thickness and composition influence rift structural style, northern North Sea, offshore Norway
Published: 2018-01-24
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Sedimentology, Stratigraphy, Tectonics and Structure
‘Salt’ giants are typically halite-dominated, although they invariably contain other evaporite (e.g. anhydrite, bittern salts) and non-evaporite (e.g. carbonate, clastic) rocks. Rheological differences between these rocks mean they impact or respond to rift-related, upper crustal deformation in different ways. Our understanding of basin-scale lithology variations in ancient salt giants, what [...]
How do normal faults grow?
Published: 2018-01-21
Subjects: Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure
Normal faults grow via synchronous increase in displacement and length (‘propagating fault model’, also known as the ‘isolated fault model’), or by rapid length establishment and subsequent displacement accrual (constant-length fault model). We here use time-series displacement (D) and length (L) data from natural and experimental faults to elucidate growth styles and D-L trajectories throughout [...]
Relict topography within the Hangay Mountains in central Mongolia: Quantifying long-term exhumation and relief change in an old landscape
Published: 2018-01-14
Subjects: Earth Sciences, Geochemistry, Geology, Geomorphology, Physical Sciences and Mathematics, Tectonics and Structure
The Hangay Mountains are a high-elevation, low-relief landscape within the greater Mongolian Plateau of central Asia. New bedrock apatite (U-Th)/He single-grain ages from the Hangay span ~70 to 200 Ma, with a mean of 122.7 ± 24.0 Ma (2σ). Detrital apatite samples from the Selenga and Orkhon Rivers, north of the mountains, yield dominant (U-Th)/He age populations of ~115 to 130 Ma, as well as an [...]
Geometry and Kinematics of Salt-detached Ramp Syncline Basins
Published: 2017-12-23
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Stratigraphy, Tectonics and Structure
Ramp-syncline basins (RSBs) are characterized by asymmetric depocentres that form by translation above flat-ramp extensional faults or salt detachments having basal steps. Both types of RSBs are composed by landward-dipping and expanding strata defined by basinward-dipping axial traces. 3D seismic data from the São Paulo Plateau, Santos Basin, Brazil, image a series of RSBs formed above thick [...]
Topographic modulation of fault kinematics in the Himalaya and Tibet
Published: 2017-12-21
Subjects: Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure
In many locations in the Himalaya and Tibet, extensional stepovers on strike-slip faults occur beneath pre-existing topographic highs. An influential physical model of orogens, explaining contemporaneous high-elevation normal faulting and low-elevation reverse faulting, holds that horizontal tectonic compression is invariant across the orogen while vertical stress varies with topography, [...]
Structural signatures of igneous sheet intrusion propagation
Published: 2017-12-08
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology
The geometry and distribution of planar igneous bodies (i.e. sheet intrusions), such as dykes, sills, and inclined sheets, has long been used to determine emplacement mechanics, define melt source locations, and reconstruct palaeostress conditions to shed light on various tectonic and magmatic processes. Since the 1970’s we have recognised that sheet intrusions do not necessarily display a [...]
Subsurface expression of a tertiary salt weld, Gulf of Mexico
Published: 2017-12-06
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure
Salt welds form due to salt expulsion and thinning by mechanical (e.g. salt flow) and/or chemical (e.g. salt dissolution) processes. Despite being ubiquitous in salt-bearing sedimentary basins, where they may trap large volumes of hydrocarbons, little is published on weld thickness and composition. We here use 3D seismic reflection, borehole, and biostratigraphic data from the Atwater Valley [...]