The present volume is rooted in a map of sedimentary successions of the Arctic Region by Grantz et al. (2011), and contains a brief, but comprehensive compilation of geological and geophysical data characterizing all significant sedimentary successions in the Arctic, which cover 57% of the polar area north of 64°N. Two main goals have been designated: (i) to provide, based on the present-day knowledge and data, a characterization of all Arctic sedimentary successions (or sedimentary accumulations), and (ii) to supply a snapshot of hydrocarbon-related exploration in the Arctic at the end of the second decade of this millennium. To achieve these goals, we represent sedimentary successions as consisting of one or several “Tectono-Sedimentary Elements” (TSE). This concept allows delineation, mapping, and characterization of 9 categories of TSEs based of main tectonic regimes that formed accommodation space.A TSE characterization template has been developed as an efficient method of organising and presenting the most important information about stratigraphy, structure, and petroleum geology of a TSE, including most significant exploration facts. This organizational architecture is the backbone of the volume and is a key feature that distinguishes it from other similar works about the sedimentary basins.

The modern Arctic has been formed through a series of continent-continent collisions, accretion of terranes and phases of crustal extension. The Neoproterozoic Timanian, Paleozoic Caledonian and Uralian, and late Mesozoic Verkhoyansk-Kolyma, Chukotkan and Brookian orogenies formed several large fold-and-thrust belts (FTBs). The FTBs are exposed across vast areas of continents and continue offshore to form a complex tectonic basement for thick sedimentary basins, playing an important role in the history of accumulation and deformation of younger unmetamorphosed sedimentary successions that are the subject of this volume. Recognition of the importance of FTBs in the Arctic geological history and their role as a controlling factor of development of Arctic sedimentary basins resulted in this chapter, in which we review the current state-of-knowledge about Arctic FTBs and highlight questions that remain to be addressed. The Enclosure D, a Map showing boundaries of the FTB and their internal first-order structural fabric, is a part of the overview.

When incorporated into a top-hat electrostatic analyzer, a gate electrode enables the separation of ions by their mass-per-charge with modest mass resolution (M/∆M ∼ 10). Gated-time-of-flight (TOF) instruments avoid the energy straggling and angular scattering effects prevalent in foil-based detection systems, providing more pristine measurements of three-dimensional distribution functions of incident ions. Gated-TOF implementations are ideal for measuring the properties of low-energy (i.e., <100 eV) thermal ions in various space environments. We present an instrument prototype capable of separating H+, He+, O+, and O2+ in Earth's ionosphere and demonstrate that in addition to providing species determination, precise operation of the gate electrode provides an electronically adjustable geometric factor that can extend a single instrument's dynamic range by several orders of magnitude.

Turbulence is characterized by the formation of small-scale structures, observed to occur down to electron scales. Furthermore, spacecraft observations have found active magnetic reconnection within such electron-scale current sheets. This points to small-scale structures serving as a pathway of energy conversion in collisonless plasma turbulence. However, the extent of their contribution to turbulent energy dissipation, compared to other energy conversion mechanisms, is still under investigation. The instruments of the MMS spacecraft are able to adequately resolve electron-scale processes, and in recent years have been gathering a large volume of burst resolution data in near-Earth space, allowing us to investigate this further. Here, we present the results of a statistical study of electron-scale structures observed by MMS in Earth’s magnetosheath. We show that the abundance of these structures as well as their properties, appear to depend more on the local turbulence parameters rather than on the large-scale dynamics of the magnetosheath, and bow-shock configuration. We report their contribution to the overall dissipation and their significance in plasma heating and particle acceleration. These results provide further insight into the pathways of energy conversion in collisionless turbulence, and contribute to our understanding of turbulent dissipation and particle energization.

Numerous prior studies have shown that as proton beta increases, a narrower range of proton temperature anisotropy values is observed. This effect has often been ascribed to the actions of kinetic microinstabilities because the distribution of observational data aligns with contours of constant instability growth rates in the beta-anisotropy plane. However, the linear Vlasov theory of instabilities assumes a uniform background in which perturbations grow. The established success of linear-microinstability theories suggests that the conditions in regions of extreme temperature anisotropy may remain uniform for a long enough time so that the instabilities have the chance to grow to sufficient amplitude. Turbulence, on the other hand, is intrinsically non-uniform and non-linear. Thin current sheets and other coherent structures generated in a turbulent plasma, may destroy the uniformity fast enough. It is therefore not a-priori obvious whether the presence of intermittency and coherent structures favors or disfavors instabilities. To address this question, we examined the statistical distribution of growth rates associated with proton temperature-anisotropy driven microinstabilities and local nonlinear time scales in turbulent plasmas. Linear growth rates are, on average, substantially less than the local nonlinear rates. However, at the regions of extreme values of temperature anisotropy, near the "edges" of the populated part of the proton temperature anisotropy-parallel beta plane, the instability growth rates are comparable or faster than the turbulence time scales. These results provide a possible answer to the question as to why the linear theory appears to work in limiting plasma excursions in anisotropy and plasma beta.

The Amawk thrust and the underlying structural window in the Mt. Doonerak antiform in the central Brooks Range were originally recognized by Gil Mull, who estimated over 90 km of northward displacement on the thrust. The parautochthonous lower plate consists of deformed pre-Mississippian metavolcanic and metasedimentary rocks overlain on a regional unconformity by the Mississippian to Triassic Ellesmerian Sequence, units that extend northward across the North Slope. Upper plate rocks on the northern flank consist of latest Devonian to Jurassic strata of the north-vergent Endicott Mountains allochthon (EMA). The southern flank consists of a low-grade metamorphic assemblage of Devonian and older strata assigned to the central belt (CB) of the Brooks Range because of their metamorphic character. Only the Frasnian (lower Upper Devonian) Hunt Fork Shale (Dhf) is recognized on both flanks of the antiform, with it being the basal unit of the EMA and the youngest unit in the CB. On the southern flank, the lowest Dhf is marked by local units of quartz-rich sandstone, sometimes overlain by thin fossiliferous units of Frasnian limestone, and locally intruded by mafic sills and dikes having rift-like geochemistry. The sandstone rests directly on various lithologic units, including Middle Cambrian metaclastic rocks, Silurian-Middle Devonian platform carbonate, and Middle Devonian felsic metavolcanic and metagraywacke rocks, which together provide evidence of an angular unconformity at the base of the Dhf. Units below the unconformity have significant DZ peaks at 600-650 Ma indicative of Timanian sources, whereas the Dhf quartzite above lacks those peaks and has peaks at ~400 Ma, similar to the Dhf in the EMA. We conclude a major sub-Frasnian unconformity exists in the CB that separates post-rift fill (Dhf) from deformed Middle Devonian rift and older pre-rift units. With the Amawk thrust restored, this unconformity appears to young progressively northward from the CB to the sub-Mississippian unconformity in the core of the antiform and north to the North Slope. In contrast, the Amawk thrust must ramp down to the south under the south-flank stratigraphy in a hanging wall cut-off relation, suggesting the CB comprises the stratigraphically lower part of the EMA. Folding of the Mt. Doonerak antiform occurred later in Cenozoic time.

First posted February 5, 2021 For additional information, contact: Geology, Energy & Minerals Science CenterU.S. Geological Survey12201 Sunrise Valley Drive954 National CenterReston, VA 20192Contact Pubs Warehouse Using a geology-based assessment methodology, the U.S. Geological Survey estimated a mean of 1,407 billion (1.4 trillion) cubic feet of gas in conventional accumulations in Upper Devonian to Lower Cretaceous strata of the western North Slope, Alaska.

Kinetic dissipation of turbulence is an important physical process occurring in collisionless plasmas. Using in‐situ data from the Magnetospheric Multiscale ( MMS ) Mission, we investigate the statistical distribution of kinetic dissipation in the terrestrial magnetosheath. We make use of an analysis of the Vlasov–Maxwell equations that provides a general description of transfer of internal energy, fluid‐flow energy, and electromagnetic energy in collisionless plasma, including both spatial transport and conversion between forms. In particular, we focus on the channels that separately produce proton and electron internal energies. Applying those results to MMS burst‐mode data obtained in the weakly collisional, turbulent magnetosheath plasma, it is possible to quantify contributions to dissipation from the compressive pressure‐dilatation channel, and from the incompressive pressure‐strain channel, for both plasma species. We also employ a simple spatial filtering approach as a first step to quantifying plasma heating at large and small scales. The analysis is carried out for 50 selected turbulent data intervals, and statistical distributions of the results are presented.

The Earth's magnetosphere is filled by particles from two sources: the solar wind and the ionosphere.Ionospheric ions are initially cold and contain He + and O + , in addition to to H + .Depending on their initial magnetic latitude and local time, and the state of the magnetosphere, they may contribute to the plasmasphere, the plasma sheet, the ring current, the warm plasma cloak etc. Depending on which path they follow in the magnetosphere, some of these ionospheric ions remain cold when they reach the two key reconnection regions: the Earth's magnetopause and the plasma sheet in the tail.In this presentation, we will first review previous statistical works that quantify the number of cold/ionospheric ions near these two regions.Several works have attempted to quantify these populations, but they are inherently difficult to characterize due to their low energy, often below the spacecraft potential.We will also discuss the impacts they have on the magnetic reconnection process.Ionospheric ions mass-load the regions where reconnection takes place and change the characteristic Alfven speed, resulting in a smaller reconnection electric field.They also take a portion of the energy that is imparted to particles, affecting the energy budget of magnetic reconnection.Finally, they introduce new length and time scales, associated to their gyroradius and gyroperiod.We will discuss what are the implications of these impacts for the evolution of the magnetosphere -solar wind interactions.

Processes driven by unsteady reconnection can efficiently accelerate particles in many astrophysical plasmas. An example is the reconnection jet fronts in an outflow region. We present evidence of suprathermal ion acceleration between two consecutive reconnection jet fronts observed by the Magnetospheric Multiscale mission in the terrestrial magnetotail. An earthward propagating jet is approached by a second faster jet. Between the jets, the thermal ions are mostly perpendicular to magnetic field, are trapped, and are gradually accelerated in the parallel direction up to 150 keV. Observations suggest that ions are predominantly accelerated by a Fermi-like mechanism in the contracting magnetic bottle formed between the two jet fronts. The ion acceleration mechanism is presumably efficient in other environments where jet fronts produced by variable rates of reconnection are common and where the interaction of multiple jet fronts can also develop a turbulent environment, e.g., in stellar and solar eruptions.

Charged particles escape our atmosphere following Earth’s magnetic field and constitute a main source of matter that modulates Sun-Earth interactions.

Spacecraft formation flying in co-planar identical orbits with oppositely directed apse lines (eccentricity vectors) allows simultaneous in-situ measurements in different altitudes and time-sequential measurements in a limited altitude range (rapid revisit); a key enabling factor in understanding many poorly understood phenomena in our atmosphere and its interaction with the magnetosphere. The dynamics and control problem for flying formations in mirrored orbits are investigated using the Mechanisms of Energetic Mass Ejection - Explorer (MEME-X) mission concept as a case study. It is determined that the proposed two-craft and four-craft configurations require routine maintenance to correct their relative motion. The formation maintenance costs are quantified for both configurations and determined to be within the capabilities of small satellites. A high-fidelity end-to-end simulation is developed to model the entire two-craft mission concept, from orbit insertion to decommissioning, providing an approximate baseline for the flight dynamics costs of similar missions using multiple spacecraft flying in mirrored orbits.

We present estimates of the turbulent energy-cascade rate derived from a Hall-magnetohydrodynamic (MHD) third-order law. We compute the contribution from the Hall term and the MHD term to the energy flux. Magnetospheric Multiscale (MMS) data accumulated in the magnetosheath and the solar wind are compared with previously established simulation results. Consistent with the simulations, we find that at large (MHD) scales, the MMS observations exhibit a clear inertial range dominated by the MHD flux. In the subion range, the cascade continues at a diminished level via the Hall term, and the change becomes more pronounced as the plasma beta increases. Additionally, the MHD contribution to interscale energy transfer remains important at smaller scales than previously thought. Possible reasons are offered for this unanticipated result.

A familiar problem in space and astrophysical plasmas is to understand how dissipation and heating occurs. These effects are often attributed to the cascade of broadband turbulence which transports energy from large scale reservoirs to small scale kinetic degrees of freedom. When collisions are infrequent, local thermodynamic equilibrium is not established. In this case the final stage of energy conversion becomes more complex than in the fluid case, and both pressure-dilatation and pressure strain interactions (Pi-D≡-Π_{ij}D_{ij}) become relevant and potentially important. Pi-D in plasma turbulence has been studied so far primarily using simulations. The present study provides a statistical analysis of Pi-D in the Earth's magnetosheath using the unique measurement capabilities of the Magnetospheric Multiscale (MMS) mission. We find that the statistics of Pi-D in this naturally occurring plasma environment exhibit strong resemblance to previously established fully kinetic simulations results. The conversion of energy is concentrated in space and occurs near intense current sheets, but not within them. This supports recent suggestions that the chain of energy transfer channels involves regional, rather than pointwise, correlations.

Weakly collisional space plasmas are rarely in local thermal equilibrium and often exhibit non-Maxwellian electron and ion velocity distributions that lead to the growth of microinstabilities, that is, enhanced electric and magnetic fields at relatively short wavelengths. These instabilities play an active role in the evolution of space plasmas, as does ubiquitous broadband turbulence induced by turbulent structures. This study compares certain properties of a 2.5 dimensional Particle-In-Cell (PIC) simulation for the forward cascade of Alfvenic turbulence in a collisionless plasma against the same properties of turbulence observed by the Magnetospheric Multiscale Mission spacecraft in the terrestrial magnetosheath. The PIC simulation is of decaying turbulence which develops both coherent structures and anisotropic ion velocity distributions with the potential to drive kinetic scale instabilities. The uniform background magnetic field points perpendicular to the plane of the simulation. Growth rates are computed from linear theory using the ion temperature anisotropies and ion beta values for both the simulation and the observations. Both the simulation and the observations show that strong anisotropies and growth rates occur highly intermittently in the plasma, and the simulation further shows that such anisotropies preferentially occur near current sheets. This suggests that, though microinstabilities may affect the plasma globally , they act locally and develop in response to extreme temperature anisotropies generated by turbulent structures. Further studies will be necessary to understand why there is an apparent correlation between linear instability theory and strongly intermittent turbulence.

Using in situ data, accumulated in the turbulent magnetosheath by the Magnetospheric Multiscale (MMS) Mission, we report a statistical study of magnetic field curvature and discuss its role in the turbulent space plasmas. Consistent with previous simulation results, the Probability Distribution Function (PDF) of the curvature is shown to have distinct power-law tails for both high and low value limits. We find that the magnetic-field-line curvature is intermittently distributed in space. High curvature values reside near weak magnetic-field regions, while low curvature values are correlated with small magnitude of the force acting normal to the field lines. A simple statistical treatment provides an explanation for the observed curvature distribution. This novel statistical characterization of magnetic curvature in space plasma provides a starting point for assessing, in a turbulence context, the applicability and impact of particle energization processes, such as curvature drift, that rely on this fundamental quantity.

First posted January 23, 2020 For additional information, contact: Director, Eastern Energy Resources Science CenterU.S. Geological Survey12201 Sunrise Valley Drive, MS-954Reston, VA 20192 Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 3.6 billion barrels of oil and 8.9 trillion cubic feet of natural gas (associated and nonassociated) in conventional accumulations in Mississippian through Paleogene strata in the central North Slope of Alaska.

First posted November 8, 2019 For additional information, contact: Contact Information,Geology, Minerals, Energy, & Geophysics Science Center—Menlo ParkU.S. Geological Survey345 Middlefield RoadMenlo Park, CA 94025-3591FAX 650-329-4936 The Lomonosov-Makarov Province lies in the central Arctic Ocean and encompasses the northern part of the oceanic Amerasia Basin (Makarov and Podvodnikov Basins) and the adjoining Lomonosov Ridge and Siberian continental margins. The Amerasia Basin is thought to have been created in the Jurassic and Early Cretaceous by rotational rifting of the Alaska-Siberia margin away from the Canada margin about a pivot point in the Mackenzie Delta and an associated continental-scale transform fault along the Lomonosov Ridge. The province is bounded on the south by the Cretaceous Alpha-Mendeleev Ridge, an undersea ridge composed of plume-type volcanic rocks that obliquely crosses the Amerasia Basin, dividing it into northern and southern parts. The thickest passive-margin succession in the province lies along the Siberian margin, where sediments thin from a maximum thickness along the continental margin to less than 2 km in the basin. The northern part of the province consists of the Lomonosov Ridge, which was rifted away from the Eurasia Plate in the Paleocene during formation of the oceanic Eurasia Basin, creating an isolated, narrow, submerged, but high-standing microcontinent. This part of the province contains sediments that were shed from the Eurasia Plate in the Mesozoic and covered by pelagic and hemipelagic sediments in the Cenozoic, creating depositional successions with thicknesses ranging from about 1 to more than 5 km.This tectonic framework provides the basis for division of the province into four assessment units (AUs), including (1) Lomonosov Ridge AU, (2) Makarov Basin Margin AU, (3) Siberian Passive Margin AU, and (4) Makarov Basin AU. The Lomonosov Ridge and Makarov Basin Margin AUs compose a displaced part of the Cretaceous shelf and slope, respectively, of the Eurasia continental margin with a covering drape of pelagic Cenozoic sediments. The Siberian Passive Margin and Makarov Basin AUs represent the slope of the Siberian continental margin and adjoining basin plain deposits, respectively, deposited on oceanic crust of the northern Amerasia Basin. All of the AUs are entirely submarine and covered by the polar icecap, and consequently have not been explored for petroleum. Petroleum source rock units considered in the assessment of the province are mostly hypothetical, and include Triassic and Jurassic platformal marine shale units on the Lomonosov Ridge, and province-wide Lower Cretaceous synrift, Lower and Upper Cretaceous postrift, and Paleogene organic-rich shale intervals. The most prospective reservoirs and traps are envisioned to include base-of-slope turbidite-fan complexes, slope channels and basins, extensional and growth fault structures, and other stratigraphic, structural, and composite trap features typically present on clastic-dominated continental passive margins. Because of concerns about reservoir quality in the Makarov Basin AU and the detrimental effect of Paleocene rifting in the Lomonosov Ridge AU, these units were not quantitatively assessed, as they were judged to have less than 10 percent probability of containing at least one accumulation of hydrocarbons equal to or greater than 50 million barrels of oil equivalent (MMBOE). The mean volumes of undiscovered resources for the Makarov Basin Margin AU are estimated to be 0.12 billion barrels of oil and 0.74 trillion cubic feet of nonassociated gas, whereas the undiscovered resources for the Siberian Passive Margin AU are estimated to be ~1 billion barrels of oil and 4.7 trillion cubic feet of nonassociated gas.