Short-wave infrared continuous-variable quantum key distribution over satellite-to-submarine channels

The trans-media transmission of quantum pulse is one of means of free-space transmission which can be applied in continuous-variable quantum key distribution (CVQKD) system. In traditional implementations for atmospheric channels, the 1500-to-1600-nm pulse is regarded as an ideal quantum pulse carrier. Whereas, the underwater transmission of this pulses tends to suffer from severe attenuation, which inevitably deteriorates the security of the whole CVQKD system. In this paper, we propose an alternative scheme for implementations of CVQKD over satellite-to-submarine channels. We estimate the parameters of the trans-media channels, involving atmosphere, sea surface and seawater and find that the short-wave infrared performs well in the above channels. The 450 nm pulse is used for generations of quantum signal carriers to accomplish quantum communications through atmosphere, sea surface and seawater channels. Numerical simulations show that the proposed scheme can achieve the transmission distance of 600 km. In addition, we demonstrate that non-Gaussian operations can further lengthen its maximal transmission distance, which contributes to the establishment of practical global quantum networks.

Environment of Deposition and Paleogeography of the Late Cretaceous Glenburn Formation, Eastern North Island, New Zealand

<p>The Glenburn Formation of the East Coast of New Zealand is a Late Cretaceous sedimentary formation consisting of alternating layers of sandstone, mudstone and conglomerate. The Glenburn Formation spans a depositional timeframe of over 10 Ma, is over 1000 m thick, is regionally extensive and is possibly present over large areas offshore. For these reasons, it is important to constrain the paleoenvironment of this unit. Late Cretaceous paleogeographic reconstructions of the East Coast Basin are, however, hampered by a number of factors, including the pervasive Neogene to modern tectonic deformation of the region, the poorly understood nature of the plate tectonic regime during the Cretaceous, and a lack of detailed sedimentological studies of most of the region’s Cretaceous units. Through detailed mapping of the Glenburn Formation, this study aims to improve inferences of regional Cretaceous depositional environments and paleogeography. Detailed facies based analysis was undertaken on several measured sections in eastern Wairarapa and southern Hawke’s Bay. Information such as bed thickness, grain size and sedimentary structures were recorded in order to identify distinct facies. Although outcrop is locally extensive, separate outcrop localities generally lie in different thrust blocks, which complicates comparisons of individual field areas and prevents construction of the large-scale, three-dimensional geometry of the Glenburn Formation. Glenburn Formation consists of facies deposited by sediment gravity flows that were primarily turbidity currents and debris flows. Facies observed are consistent with deposition on a prograding submarine fan system. There is significant variation in facies both within and between sections. Several distinct submarine fan architectural components are recognised, such as fan fringes, fan lobes, submarine channels and overbank deposits. Provenance and paleocurrent indicators are consistent with deposition having occurred on several separate submarine fans, and an integrated regional paleogeographic reconstruction suggests that deposition most likely occurred in a fossil trench following the mid-Cretaceous cessation of subduction along the Pacific-facing margin of Gondwana.</p>

Environment of Deposition and Paleogeography of the Late Cretaceous Glenburn Formation, Eastern North Island, New Zealand

<p>The Glenburn Formation of the East Coast of New Zealand is a Late Cretaceous sedimentary formation consisting of alternating layers of sandstone, mudstone and conglomerate. The Glenburn Formation spans a depositional timeframe of over 10 Ma, is over 1000 m thick, is regionally extensive and is possibly present over large areas offshore. For these reasons, it is important to constrain the paleoenvironment of this unit. Late Cretaceous paleogeographic reconstructions of the East Coast Basin are, however, hampered by a number of factors, including the pervasive Neogene to modern tectonic deformation of the region, the poorly understood nature of the plate tectonic regime during the Cretaceous, and a lack of detailed sedimentological studies of most of the region’s Cretaceous units. Through detailed mapping of the Glenburn Formation, this study aims to improve inferences of regional Cretaceous depositional environments and paleogeography. Detailed facies based analysis was undertaken on several measured sections in eastern Wairarapa and southern Hawke’s Bay. Information such as bed thickness, grain size and sedimentary structures were recorded in order to identify distinct facies. Although outcrop is locally extensive, separate outcrop localities generally lie in different thrust blocks, which complicates comparisons of individual field areas and prevents construction of the large-scale, three-dimensional geometry of the Glenburn Formation. Glenburn Formation consists of facies deposited by sediment gravity flows that were primarily turbidity currents and debris flows. Facies observed are consistent with deposition on a prograding submarine fan system. There is significant variation in facies both within and between sections. Several distinct submarine fan architectural components are recognised, such as fan fringes, fan lobes, submarine channels and overbank deposits. Provenance and paleocurrent indicators are consistent with deposition having occurred on several separate submarine fans, and an integrated regional paleogeographic reconstruction suggests that deposition most likely occurred in a fossil trench following the mid-Cretaceous cessation of subduction along the Pacific-facing margin of Gondwana.</p>

The formation and evolution of submarine headless channels

The scale of submarine channels can rival or exceed those formed on land and they form many of the largest sedimentary deposits on Earth. Turbidity currents that carve submarine channels pose a major hazard to offshore cables and pipelines, and transport globally significant amounts of organic carbon. Alongside the primary channels, many systems also exhibit a range of headless channels, which often abruptly terminate at steep headscarps. These enigmatic features are widespread in lakes and ocean floors, either as branches off the main submarine channel thalweg or as isolated secondary channels. Prior research has proposed that headless channels may be associated with early and incipient stages of channel development, but their formation and evolution remain poorly understood. Here, we investigate the morphology, origin and development of headless channels by examining repeat bathymetric surveys spanning a period from 1986 to 2018, in Bute Inlet, Canada. We show how channel switching processes, the extension of turbidity currents across distal fans, along with overbanking turbidity currents, are able to initiate headless channels in submarine settings. We discuss how the evolution of headless channels plays an important role in shaping submarine channels, promoting channel extension and modifying the overall longitudinal profile, as well as impacting the character of sedimentary records in channel-lobe transition zones.

Quantifying structural controls on submarine channel architecture and kinematics

Over the past two decades, the increased availability of three-dimensional (3-D) seismic data and their integration with outcrop and numerical modeling studies have enabled the architectural evolution of submarine channels to be studied in detail. While tectonic activity is a recognized control on submarine channel morphology, the temporal and spatial complexity associated with these systems means submarine channel behavior over extended time periods, and the ways in which processes scale and translate into time-integrated sedimentary architecture, remain poorly understood. For example, tectonically driven changes in slope morphology may locally enhance or diminish a channel’s ability to incise, aggrade, and migrate laterally, changing channel kinematics and the distribution of composite architectures. Here, we combined seismic techniques with the concept of stratigraphic mobility to quantify how gravity-driven deformation influenced the stratigraphic architecture of two submarine channels, from the fundamental architectural unit, a channel element, to channel complex scale, on the Niger Delta slope. From a 3-D, time-migrated, seismic-reflection volume, we evaluated the evolution of widths, depths, sinuosities, curvatures, and stratigraphic mobilities at fixed intervals downslope as the channel complexes interacted with a range of gravity-driven structures. At channel element scale, sinuosity and bend amplitude were consistently elevated over structured reaches of the slope, displaying a nonlinear increase in length, perpendicular to flow direction. At channel complex scale, the same locations, updip of structure, correlated to an increase in channel complex width and aspect ratio. Normalized complex dimensions and complex-averaged stratigraphic mobilities showed lateral migration to be the dominant form of stratigraphic preservation in these locations. Our results explain the intricate relationship between the planform characteristics of channel elements and the cross-sectional dimensions of the channel complex. We show how channel element processes and kinematics translate to form higher-order stratigraphic bodies, and we demonstrate how tectonically driven changes in slope develop channel complexes with distinct cross-sectional and planform architectures.

Campanian Calciturbidites from Northeast Iraq, Kurdistan Region: Insight into Paleogeography and Source Areas of the Shiranish Formation

Calciturbidites are similar to siliciclastic turbidites in structure, texture, basin physiography and processes of deposition; nevertheless, their clasts (grains) are carbonate minerals. Turbidity currents transport carbonate grains from carbonate source areas and coastal areas to the deep basins after passing the shelf (peri-platform). These currents are triggered by short-lived catastrophic events, such as tsunamis, earthquakes, marine slides, and typhoons. The Late Cretaceous Zagros Foreland and Hinterland in NE-Iraq (Kurdistan Region) was an active source for the shedding of voluminous sediments to the deep basin of Zagros Foreland Basin. During late Campanian, Shiranish Formation was deposited in the foreland basin; it occurs in the most famous oil fields in the Middle East and represents hemplagite facies (much diluted turbidite facies). Previous studies have not broached the origins of Shiranish Formation, neither in detail or briefly. Conversely, the present study focused on linking the calciturbidite system to the origin of the deposition of the Shiranish Formation via derivation from main carbonate source areas. Along long distance, the sediments crossed the marginal slope, scoring submarine channels and depositing coarse detrital carbonates before reaching the basin plain. On the plain, mostly the fine fractions have settled down and mixed with pelagic sediment. The calciturbidite evidence could be tracked for more than 40 km in the studied area from the slope and outer shelf (present Thrust Zone) to the basin plain (High Folded zone). In several places, channelized detrital laminated limestones are found inside Shiranish Formation and in the most proximal area near Qaladiza town. Bouma sequences are clearly observable with erosional base and A, B, and C divisions. These calciturbidites are keys for picturing Campanian paleogeography and nature of the source area which was consisted of limestone.

How fast do submarine fans grow? Insights from the Quaternary Golo fans, offshore Corsica

High-resolution seismic, core, and chronological data from the Quaternary Golo deep-sea fans, offshore Corsica, France, give new insights into rates of submarine fan growth. Average vertical deposition rates for units that represent the Late Pleistocene glacial periods are 0.1–0.5 m/k.y. Glacial-age deposits are sand rich; in contrast, post-glacial deposits lack a significant sand fraction and are dominated by carbonate-rich mud. As a result, seismically constrained volumetric rates of deposition for glacial periods with low sea level and a subaerially exposed shelf are ~0.23 km3/k.y., 2×–5× higher than rates during interglacials when sea level is high, the shelf is submerged, and sand is trapped in shallow-marine environments. At millennial time scales, variations in deposition rate reflect climate-driven sea-level changes, autogenic avulsion of river channels that extend across the shelf during low sea level, and autogenic avulsion of submarine channels that shift the locus of deposition laterally. Short-term deposition rates range from 8.6 m/k.y. at proximal portions of submarine fans to 0.4 m/k.y. along the distal fringe. Our data show that submarine fans can be dynamic environments with formation and evolution of levee-confined channels and lobe complexes in 103–104 yr, comparable to the time scales needed to form fluvial channel belts and delta lobes.

New statistical quantification of the impact of active deformation on the distribution of submarine channels

Submarine channel systems play a crucial role in governing the delivery of sediments and pollutants such as plastics from the shelf edge to deep water. Understanding their distribution in space and time is important for constraining the locus, magnitude, and characteristics of deep-water sedimentation and for predicting stratigraphic architectures and depositional facies. Using three-dimensional seismic reflection data covering the outer fold-and-thrust belt of the Niger Delta, we determined the pathways of Miocene to Pliocene channels that crossed, at 173 locations, 11 fold-thrust structures for which the temporal and spatial evolution of strain rates has been constrained over a period of 11 m.y. We use a statistical approach to quantify strain and shortening rate distributions recorded where channels have crossed structures compared to the fault array as a whole. Our results prove unambiguously that these distributions are different. The median strain rate where channels cross faults is &lt;0.6%/m.y. (~40 m/m.y.), 2.5× lower than the median strain rate of active fault segments (1.5%/m.y.) with a marked reduction in the number of channel-fault crossings where fault strain rates are &gt;1%/m.y. Our results quantify the sensitivity of submarine channels to active deformation at a population level for the first time and enable us to predict the temporal and spatial routing of submarine channels affected by structurally driven topography.