Supplemental Material: Initial uplift of the Qilian Shan, northern Tibet since ca. 25 Ma: Implications for regional tectonics and origin of eolian deposition in Asia

Supplemental dataset: Detrital zircon U-Pb ages of the sandstone samples from the Lulehe and Hongshangou sections; Figure S1: SEM images of 129 grains from sandstone sample LLH-1 showing grain roundness characteristics; Figure S2: SEM images of 140 grains from sandstone sample LLH-2 showing grain roundness characteristics; Figure S3: SEM images of 123 grains from sandstone sample LLH-3 showing grain roundness characteristics; Figure S4: SEM images of 122 grains from sandstone sample HSG-7 showing grain roundness characteristics; Figure S5: SEM images of 123 grains from sandstone sample HSG-8 showing grain roundness characteristics; Figure S6: SEM images of 123 grains from sandstone sample HSG-9 showing grain roundness characteristics; Figure S7: SEM images of representative grains from the Lulehe and Hongshangou sections showing surface microtextures.

Supplemental Material: Initial uplift of the Qilian Shan, northern Tibet since ca. 25 Ma: Implications for regional tectonics and origin of eolian deposition in Asia

Supplemental dataset: Detrital zircon U-Pb ages of the sandstone samples from the Lulehe and Hongshangou sections; Figure S1: SEM images of 129 grains from sandstone sample LLH-1 showing grain roundness characteristics; Figure S2: SEM images of 140 grains from sandstone sample LLH-2 showing grain roundness characteristics; Figure S3: SEM images of 123 grains from sandstone sample LLH-3 showing grain roundness characteristics; Figure S4: SEM images of 122 grains from sandstone sample HSG-7 showing grain roundness characteristics; Figure S5: SEM images of 123 grains from sandstone sample HSG-8 showing grain roundness characteristics; Figure S6: SEM images of 123 grains from sandstone sample HSG-9 showing grain roundness characteristics; Figure S7: SEM images of representative grains from the Lulehe and Hongshangou sections showing surface microtextures.

Solid as a rock: Tectonic control of graben extension and dike propagation

The 2014–2015 CE rift event associated with the Bárðarbunga eruption at Holuhraun, Iceland, offers a unique opportunity to study the spatial and temporal evolution of a rift graben. We present the first four-dimensional (three-dimensional plus time) monitoring of the formation and evolution of a graben during active magma transport using a suite of digital elevation models spanning from shortly before the eruption throughout 6 months of magma transport and up to 4.5 years after the eruption. This multiscale data set enables investigations of how magma supply and eruption dynamics affect tectonic structures that feed eruptions. After formation (time scale of a few days), the graben is remarkably stable throughout the eruption and for years beyond. It is unaffected by large changes in eruptive activity and effusion and seismicity rates within the plumbing system. These data document that (1) there was no direct feedback between eruptive dynamics and graben topography, and (2) graben formation is near instantaneous on tectonic time scales. These results challenge the overarching role ascribed to magma transport in recent studies of tectonomagmatic relationships in rift events, favoring regional tectonics as the fundamental driving force.

Constraining tectonic components during a geomechanics-aided successful hydrofracturing campaign of tight gas exploration field

The horizontal stress profile plays an important role, extending from wellbore stability analysis to well completion optimization of tight gas reservoirs. When considering exploration fields with planned wells being drilled to 5500-m TVD, it is imperative to quantify tectonic effects at the well location. In addition, accurately predicting stress profile and fracture initiation values in vertical wells is required to identify sweet zones and barriers. This paper presents the details of a pre-fracture geomechanical model using breakouts and advanced acoustic data for post-fracture analysis. The analysis contains a history match of fracture initiation pressure, which consider the effects of filter cake around permeable sand, variation in tensile strength, and quantification of horizontal stress contrast in the different fields. Overall, three reservoirs have been analyzed, each containing more than eight wells with operations history. Core tests were used to calibrate dynamic-to-static rock elastic and mechanical properties, both of which reduced uncertainty in the model. The poroelastic horizontal strain method was used to build a continuous stress profile. Typically, the rock fabric found in the cores, images, and anisotropy data from the three reservoirs is different and required various dynamic-to static conversions. The Aeolian deposits-based reservoir has a wide variation in horizontal stress, and fracture height is typically governed by the stiffness of the layers. The lower permeability zones have relatively higher tensile strength, compared with higher permeability zones leading to relatively higher fracture initiation values. Overall, the ratio of maximum horizontal stress-to-minimum horizontal stress varies between 1.20 and 1.28 based on post-fracture analysis, which correlates well with regional tectonics and structural data. Depending on lithological variation and structure changes, the horizontal strain component varies at the layer level within regional tectonics. Inversion of fracturing data helped to constrain horizontal strain and stress variations in the field.

Supplemental Material: Neogene sedimentary record of the evolution of a translated strike-slip basin along the Denali fault system: Implications for timing of displacement, composite basin development, and regional tectonics of southern Alaska

Ar/Ar geochronologic and U-Pb detrital zircon geochronologic ages.

Supplemental Material: Neogene sedimentary record of the evolution of a translated strike-slip basin along the Denali fault system: Implications for timing of displacement, composite basin development, and regional tectonics of southern Alaska

Ar/Ar geochronologic and U-Pb detrital zircon geochronologic ages.

On the Origin of Orphan Tremors and Intraplate Seismicity in Western Africa

On September 5–7, 2018, a series of tremors were reported in Nigeria’s capital city, Abuja. These events followed a growing list of tremors felt in the stable intraplate region, where earthquakes are not expected. Here, we review available seismological, geological, and geodetic data that may shed light on the origin of these tremors. First, we investigate the seismic records for parent location of the orphan tremors using a technique suitable when a single-seismic station is available such as the Western Africa region, which has a sparse seismic network. We find no evidence of the reported tremors within the seismic record of Western Africa. Next, we consider the possibility of a local amplification of earthquakes from regional tectonics, reactivation of local basement fractures by far-field tectonic stresses, post-rift crustal relaxation, landward continuation of oceanic fracture zones, or induced earthquakes triggered by groundwater extraction. Our assessments pose important implications for understanding Western Africa’s intraplate seismicity and its potential connection to tectonic inheritance, active regional tectonics, and anthropogenic stress perturbation.

Tectonics of the Barents Sea Continental Edge

The tectonic situation of the studied region was formed as a result of a long (about 3 billion years) evolution of the Earth's crust. The problem of tectonic zoning of the region is not devoted to many published works and cartographic materials. The position of the borders between the East European and West Arctic platforms remains a debatable issue. More ambiguous, and in some cases, approaches to tectonic zoning of the region are not clear. Nevertheless, the work is based on a unified theoretical basis, reflecting the approach to solving the problems of regional tectonics from the perspective of geodynamic evolution.