Cessation Of Deposition Research Articles

Recovery from microplastic-induced marine deoxygenation may take centuries

Climate change and plastics pollution are dual threats to marine environments. Here we use biogeochemical and microplastic modelling to show that even if there is complete removal of microplastics and cessation of deposition in the oceans in 2022, regional recovery from microplastic-induced remineralization and water column deoxygenation could take hundreds of years for coastal upwelling zones, the North Pacific and Southern Ocean. Surface stratification and reduced sea ice cover further impede regional recovery, highlighting the importance of aggressive mitigation of plastic pollution.

Accelerated sediment delivery to continental margins during post‐orogenic rebound of mountain ranges

AbstractChanges in sediment flux to continental margins are commonly interpreted in terms of tectonic growth of topography or climatic change. Here, we show that variations in sediment yield from orogenic systems, previously considered as resulting from climate change, drainage reorganisation or mantle processes can be explained by intrinsic mechanisms of mountain belt/foreland basin systems naturally evolving during post‐orogenic decay. Numerical modelling indicates an increase of sediment flux leaving the orogenic system synchronous with the cessation of deposition in the foreland basin and the transition from late syn‐ to post‐orogenesis. Experiments highlight the importance of lithospheric flexure that causes the post‐orogenic isostatic rebound of the foreland basin. Erosion of the rebounding foreland basin combined with continued sediment flux from the thrust wedge drives an acceleration in sediment outflux towards continental margins. Sediment budget records in natural settings such as the Northern Pyrenees or Western European Alps also indicate accelerated post‐orogenic sediment delivery to the Bay of Biscay and Rhône Delta respectively. These intrinsic processes that determine sediment yield to continental margins must be accounted for prior to consideration of additional external tectonic or climatic controls.

Diagenesis of the Sappington Formation in the Bridger Range, Montana: Implications for the burial and thermal history of the Western Crazy Mountain Basin

The Devonian-Mississippian Sappington Formation in the Bridger Range, Montana was investigated for its paragenetic sequence and thermal history. These results were used to establish a burial history for the area and compared to data from nearby oil and gas wells. The paragenetic evolution of the Sappington includes early diagenetic feldspar dissolution, formation of quartz overgrowths, and illite precipitation during early diagenesis at temperatures < 50 °C. Subsequent burial diagenesis resulted in the precipitation of non-ferroan and ferroan dolomite, followed by calcite cementation and replacement, pyrite replacement, and hydrocarbon generation and expulsion at temperatures > 130 °C. Devonian formations were the source of the non-ferroan dolomite cement and began precipitating in the latest Mississippian. Subsequent growth of ferroan dolomite resulted from clay transformation reactions in the Upper and Lower Sappington Members and was initiated during rapid burial in the late Cretaceous. The Bridger Range and the adjacent Western Crazy Mountain Basin underwent similar Paleozoic and Mesozoic burial histories. Vastly different Cenozoic burial histories resulted from movement along the Cross Range and Pass thrusts that caused the Bridger Range to begin uplift prior to the cessation of deposition of the Livingston Group in the early Paleocene. The discrepancies in burial history caused the Sappington Formation to reach a maximum temperature of ~135 °C in the Bridger Range and ~230 °C in the western Crazy Mountain Basin.

The stratigraphic, sedimentological and structural evolution of the southern margin of the Kazakhstan continent in the Tien Shan Range during the Devonian to Permian

Abstract The passive margin carbonate platform in the Middle Tien Shan rests on Givetian–Frasnian red siliciclastic strata. It evolved from an attached carbonate platform in the Famennian and early Tournaisian to an isolated carbonate platform in the late Tournaisian to early Bashkirian. The open-ocean side of the platform was reef-rimmed, whereas the continental side was both reef- and shoal-rimmed. Platform interiors exhibit low-energy facies during the Famennian to early Visean and high-energy facies during the late Visean to Bashkirian. Eustatic sea-level rises in the middle Tournaisian, early Visean and near the Visean and Serpukhovian boundary caused major reorganizations in platform architecture. Deformation in the middle Bashkirian reflects the onset of a convergent margin. Flexural loading by an orogenic thrust wedge controlled basin subsidence along the southern edge of the Middle Tien Shan in the Late Pennsylvanian to Asselian. Cessation of deposition in the Asselian followed by folding and granitoid plutonism reflects the onset of a rigid collision. Devonian to Permian carbonates represent outcrop analogues of coeval oil- and gas-rich carbonate platforms in the North Caspian basin and can be used for comparative and predictive sedimentological studies. Palaeozoic carbonate reservoir facies may host subsurface Cenozoic oil fields in the Fergana Basin.

Stratigraphy and structure of interior layered deposits in west Candor Chasma, Mars, from High Resolution Stereo Camera (HRSC) stereo imagery and derived elevations

Interior layered deposits (ILDs) within western Candor Chasma were studied by mapping lithologies, measuring layer attitudes and comparing the stratigraphy of two adjacent mounds. Layering tends to dip in the same direction as the local topographic slope, although at different angles. Regionally consistent attitudes do exist, suggesting postdepositional block rotations. The stratigraphy of two adjacent mounds correlates, but the thicknesses of the units differ. Most layered material appears to have been deposited conformably, with one late major unconformity. Several fault populations are identified and correlate well with regional faults associated with the formation of Valles Marineris. The data suggest that here the ILDs predate the faulting and may be early basin fill. According to our model for ILD formation, ILDs are deposited syntectonically during early basin collapse. Subsequent subsidence of surrounding areas, accompanied by little or no sedimentation, left the early deposits as individual mounds, remnants of the former subbasins. Stratigraphic differences between mounds resulted from different subsidence rates of subbasins. A significant change in depositional environment, from depositional to a near cessation of deposition and the onset of a major erosion event, possibly coincided with the opening of the main Valles Marineris troughs. We further suggest that groundwater played an important role in the formation of sulfates. The youngest unit identified, not including surficial deposits, is likely the result of a posttectonic, regionally limited volcanic event. If basin collapse continued following the cessation of deposition, this model can also account for mounds within closed basins, such as Hebes.

Isotope records in submarine speleothems from the Adriatic coast, Croatia

Abstract Isotope studies, using 14C dating, δ13C and δ18O measurements, were performed at eight speleothems taken from three submerged caves situated along the eastern Adriatic coast, Croatia. The speleothems were taken from 17 m to 38.5 m depth below mean sea level. The samples consist of four stalagmites and four stalactites in position of growth, covered with marine biogenic overgrowth, and the length of speleothems ranges from ~80 mm to ~190 mm. The youngest (surface) and the oldest (base) layers of speleothems were radiocarbon dated and the 14C ages range from 21,600 cal B.P. to 37,000 yr B.P. During that period the global sea level was more than 40 m below the recent one, so presently submerged objects were under the subaerial conditions necessary for speleothem deposition. 14C ages of the youngest layer range from 21,600 to 32,200 cal B.P. for different submerged speleothems. This indicates the time when the speleothem growth ceased, most probably due to flooding of the cave with either fresh or brackish water. Speleothem growth during the Last Glacial Maximum (30–19 kyr ago) and different time of growth cessation for the different speleothem samples suggest that climate change was not the reason for cessation of deposition. Samples for δ13C and δ18O measurements were taken from six submerged speleothems with sampling distances of ca. 5–10 mm from the surface to the base of speleothems. Most of the δ13C values are in the range from −10.5‰ to −8.5‰, with few exceptions to −6‰. These values are typical for Dinaric karst, and very different values for marine biogenic overgrowth indicate that no isotopic exchange took place during the submerged period. δ18O values range from −6.7‰ to −4.1‰. A weak correlation between δ13C and δ18O values indicates possible kinetic isotope fractionation during the calcite precipitation. If the δ18O record is interpreted as climatic signal, it suggests similar climatic conditions for the late Pleistocene and the Holocene, especially no significant differences in temperature and/or moisture transport.

Consolidation of a soil layer subsequent to cessation of deposition

It is necessary in certain cases to estimate the progress of consolidation in a soil layer that has ceased increasing in thickness over time. In this paper, the existing excess pore pressures for two time–thickness relations are used as the "initial" pore pressures for analysing the consolidation of soil subsequent to the cessation of deposition. Average degrees of consolidation of the soil layer are presented for one-way drainage and two-way drainage boundary conditions. The average degrees of consolidation are compared with those for uniform and triangular initial excess pore pressure distributions. It is found that the average degree of consolidation for one-way drainage boundaries can be estimated using the value for the triangular distribution. The average degree of consolidation for two-way drainage boundaries is bound by the averages for both the uniform and the triangular initial excess pore pressure distributions.Key words: consolidation, deposition, drainage, settlement, soil.

Interaction between alluvial fan sedimentation, thrusting, and sea-level changes: an example from the komeno formation (early pleistocene), Southwest Japan

The gravelly Komeno Formation, 300 m thick or less, accumulated during 1.0-0.7 Ma along the faulted, N—S-trending Suzuka Mountain front in southwest Japan. The deposits originated as an alluvial fan on the mountain front. Three facies, deposited by debris flow, debris flow and braided flow, and braided flow, can be recognized in the fan body. These facies built two downcurrent facies successions that enable reconstruction of a three-dimensional facies architecture of the body. This fan (Komeno Fan) can be divided into three smaller fans, each stratigraphically composed of two to four different facies and bounded on the west by a segment of the Ichishi Thrust. The bases of these fan bodies become tephrostratigraphically younger northward. The Ichishi thrusting, triggered by severe horizontal crustal compression in SW Japan, began at about 1 Ma. The Komeno Fan, therefore, can be interpreted to be a northerly-formed, coalesced, composite alluvial fan generated by the northerly-shifted Ichishi thrusting. The Komeno Fan sedimentation ended at 0.7 Ma, although the Ichishi thrusting in the study area persisted to near the end of the Middle Pleistocene. The cessation of deposition was probably due to extra-lowering of the base-level of erosion caused by a combination of basin uplift by compression and sea-level fall during deposition.

Oscillatory behavior of the agglomeration rate in island copper films.

The post-deposition dc electrical-resistance increase of island copper films deposited on glass substrates at room temperature and at a pressure of 2\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}5}$ torr is studied. Films in the resistance range 10\char21{}95 M\ensuremath{\Omega}/\ensuremath{\square} were studied under different conditions to ascertain the role of residual gases and substrate-surface contaminants on the agglomeration rate. Mobility coalescence of small islands of Cu giving rise to an agglomerated film structure is assumed to explain the post-deposition resistance increase. It was found that the logarithm of the normalized resistance [ln(R/${R}_{0}$); ${R}_{0}$ is the initial resistance of the film at a time t=0] varies linearly as the logarithm of the time elapsed after the cessation of deposition. The constant of proportionality in the above relationship, termed the agglomeration rate m, shows an interesting oscillatory dependence on the initial resistance of the film and the condition of study. Nearly all the maxima and minima of m for two of the conditions studied in detail as a function of the initial resistance occur at about the same initial resistance values with the films having almost the same structure at these points. An argument is put forward based on the oscillatory nature of the effective tunneling barrier as a function of the island size to explain this unusual behavior. It is found that the presence of a thin film of water vapor on the substrate surface impedes the agglomeration rate to a great extent while the presence of adsorbed ${\mathrm{O}}_{2}$ and ${\mathrm{N}}_{2}$ decreases the energy for surface migration of islands of copper thereby increasing the agglomeration rate.

Stratigraphy of Upper Cambrian-Lower Ordovician Subsurface Sequence in Williston Basin

Trilobites and brachiopods of Late Cambrian and Early Ordovician ages were obtained from seven wells that penetrated the Deadwood Formation in the Williston basin in Montana and North Dakota. The sections contain a basal transgressive sandstone overlain by interbedded limestone pebble conglomerate, dark shale, and light colored sandstone. On the east in North Dakota the section becomes markedly sandy. In these eastern sections it is difficult to place the Deadwood-Winnipeg boundary exactly, but in Montana there is a sharp lithic contact which represents a significant subaerial erosion break in the section. In Montana Dicellomus of Dresbachian age is present in the basal sandstone. The Elvinia, Conaspis, Ptychaspis-Prosaukia, and Saukia zones of Franconian and Trempealeauan ages occur in the overlying 287 feet. There is no evidence of a depositional break between the Upper Cambrian and the Lower Ordovician, and beds at this level carry the transitional Apoplanias faunule. An arbitrary boundary is placed at the first appearance of Symphysurina and (or) the associated Euloma. Faunas of the Lower Ordovician trilobite Zones A, B, C, D, E, and G (of Ross [1951] and Hintze [1953]) have been found. Intercalated graptolite shales permit correlation with Berry's Lower Ordovician graptolite Zones 1, 2, and 3. On the basis of the faunas the Deadwood can be correlated with formations throughout the anadian Rockies, Montana, Wyoming, Utah, Nevada, Colorado, New Mexico, Texas, and Missouri. Lithofacies exhibit many lateral changes within the basin. No persistent units can be recognized for the entire basin, but local facies members useful for mapping in smaller areas are distinguished. Reconstruction of paleogeographic conditions for the Late Cambrian shows the region as a wide, shallowly inundated coastal shelf with a west-northwesterly slope. A positive transcontinental arch between Laurentia and Siouxia forms a low sandy eastern shore or a maze of islands and shallow straits connecting with the upper Mississippi Valley region. The recurring transgressions of the middle Dresbachian, the early Franconian, and the middle Trempealeauan were not accompanied by upwarping of the land areas and may have been caused by eustatic sea-level changes. Shoaling in the Late Cambrian moved the shoreline gradually westward to western North Dakota. The Saukia zone trilobite genera died out, but dendroid graptolites persisted on the oxygenated shoals. Slow deposition of carbonate oo es, muds, and glauconites continued in the basin sites. The appearance of Euloma, Symphysurina, and Hystricurus marks the beginning of a new marine transgression which altered the shore topography and eventually carried the Zones A and B assemblages into the upper Mississippi Valley. Depositional thickening of the basal Lower Ordovician strata from the Richey to the Pine and Cabin Creek fields near the Montana-North Dakota border suggests that the axis of the earliest basin depocenter was in the direction of the Pine and Cabin Creek fields. During Zones D-E time, widespread carbonate shoals supported a gastropod-brachiopod fauna allied to assemblages of the central interior states. By Zones F-G time, the eastern sections were markedly sandy. Zone G faunas are the youngest Early Ordovicia assemblages known in the basin. The continued shoaling and eventual cessation of deposition probably occurred throughout the Williston basin during Zone H time, or definitely before the end of the Early Ordovician. Although no hydrocarbons are known in the Deadwood, it is suggested that the Deadwood shales may be source rocks. Stratigraphic entrapment of these postulated hydrocarbons may have occurred in Winnipeg strata or in sandy Deadwood facies during Early to Middle Ordovician time along the then newly formed eastern rim of the basin.

Structure variation within two red-brown earth profiles

Stereomicroscopic and thin-section studies of structure and fabric features of two red-brown earth profiles from the Riverine Plain of south eastern Australia are assessed in relation to depositional layering and soil formation as suggested by field evidence. Internal fabric in relation to mode of occurrence suggests that some of these features are inherited from, and characteristic of, the original depositional layer whilst others have been formed or accumulated during soil formation subsequent to the cessation of deposition. Trends in the degree of development of these features with increasing depth suggest that the Hanwood profile consists of five depositional layers with evidence for a depositional time break, accompanied by soil formation, at the top of the fourth layer below the present surface. The Deniboota profile includes three depositional layers with evidence for a time break at the top of the second layer below the present surface.