Role Of Subsidence Research Articles

Land loss in the Mississippi River Delta: Role of subsidence, global sea-level rise, and coupled atmospheric and oceanographic processes

Land loss in the Mississippi River Delta: Role of subsidence, global sea-level rise, and coupled atmospheric and oceanographic processes

The role of subsidence and accommodation generation in controlling the nature of the aeolian stratigraphic record

Despite a well-documented record of preserved aeolian successions from sedimentary basins characterized by widely variable subsidence rates, the relationship between aeolian architecture and subsidence-driven accommodation generation remains poorly constrained and largely unquantified. Basin subsidence as a control on aeolian sedimentary architecture is examined through analysis of 55 ancient case-studies categorized into settings of ‘slow’ (>1–≤10 m Myr −1 ), ‘moderate’ (>10–≤100 m Myr −1 ) and ‘rapid’ (>100 m Myr −1 ) time-averaged subsidence rates. In rapidly subsiding basins, aeolian successions are thicker and associated with (1) thicker and more laterally extensive dune-sets with increased foreset preservation, (2) greater proportions of wet-type interdunes and surface stabilization features and (3) more extensive interdune migration surfaces, bounding sets that climb more steeply. In slowly subsiding basins, aeolian successions are thinner, and associated with a greater proportion of (1) aeolian sandsheets and (2) supersurfaces indicative of deflation and bypass. Rapid subsidence promotes (1) steeper bedform climb, resulting in increased preservation of the original dune foreset deposits and (2) relatively elevated water tables, leading to sequestration of deposits beneath the erosional baseline and encouraging development of stabilizing agents; both factors promote long-term preservation. Slow subsidence results in (1) lower angles of climb, associated with increased truncation of the original dune forms, and (2) greater post-depositional reworking, where sediment is exposed above the erosional baseline for extended time-periods. Quantitative analysis of sedimentary stratal architecture in relation to rates of basin subsidence helps constrain the mechanisms by which sedimentary successions are accumulated and preserved into the long-term stratigraphic record. Supplementary material: Results of statistical analyses presented here are available at https://doi.org/10.6084/m9.figshare.c.5515695.v1

P5. In vitro comparison of novel adjustable-lordotic expandable and static hyperlordotic lateral interbody spacers on endplate loading and lordosis correction

BACKGROUND CONTEXT For restoration of sagittal alignment, hyperlordotic lateral lumbar interbody fusion (LLIF) spacers are available as expandable or static spacers with many sizes, and possess up to 30° of implant lordosis to maximize lumbar lordosis when used in combination with anterior longitudinal ligament (ALL) resection. However, angular mismatch between the implant and vertebral endplates may play a role in subsidence due to asymmetric loading of the anterior implant edge. The relationship between implant size and their effect on segmental lordosis correction and anterior-posterior endplate loading is poorly understood. PURPOSE The aim of this study is to compare adjustable-lordosis expandable and static LLIF spacers in regards to lordosis correction and endplate force distribution. STUDY DESIGN/SETTING In vitro human cadaveric study. PATIENT SAMPLE A total of 14 cadaveric specimens. OUTCOME MEASURES Lordosis and anterior-posterior endplate forces. METHODS Fourteen L4–L5 cadaveric segments were used. A 55 lb axial load was applied to L4 to simulate intraoperative loads. Segments were instrumented with bilateral pedicle screws and a sequence of expandable spacers with anterior fixation (n=7) or static spacers (n=7) at varied heights and implant lordosis matched between spacers (nine constructs per spacer), including (A three height and lordosis combinations with intact ALL; and B) six height and lordosis combinations following ALL resection. Segmental lordosis and endplate force-maps were collected and compared between the two spacers. An equivalent loading ratio (ELR=anterior load/total load*100%) was calculated; ELR=80% refers to 80% anterior and 20% posterior edge loading. An ELR of 50% is equivalent anterior-posterior loading. RESULTS No significant differences in lordosis was observed between spacers except at between the 20° expandable spacer (17.4mm) and the 13mm 20° static spacer (22.5°±4.9° and 16.7°±2.3°, respectively, p=0.020). Equivalent anterior-posterior loading ratios were also quantified. Prior to ALL resection, the 9mm 10° static spacer had a significantly larger ELR than the 20° expandable spacer (11.5mm, p=0.016), indicating more anterior loading with the static spacer (91.5% ± 7.6 versus 70.5% ± 18.8%). Following ALL resection, the 11mm 10°, 11mm 20°, and 13mm 20° static spacers (85.1%, 99.2%, and 94.8%, respectively) all had significantly larger ELRs than the 20° expandable at 11.5mm, 14.7mm, and 17.4mm heights (52.0%, 70.0%, and 76.2%), respectively (p CONCLUSIONS This study suggests that expandable and static spacers have comparable lordosis correction; however, greater anterior endplate loading was observed with static spacers. Increased anterior endplate loading may lead to subsidence. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

289. Optimizing lateral sagittal correction and anterior-posterior interbody loading: in vitro biomechanical assessment of effect of implant lordosis and height on endplate loading and segmental lordosis

BACKGROUND CONTEXT Restoration of sagittal balance is critical for deformity correction. Hyperlordotic lateral lumbar interbody fusion (LLIF) spacers are available in many sizes, and possess up to 25° of implant lordosis to maximize lumbar lordosis when used in combination with anterior longitudinal ligament (ALL) resection. However, angular mismatch between the implant and vertebral endplates may play a role in subsidence due to asymmetric loading of the anterior implant edge. The relationship between implant height and lordosis selection, and their effect on segmental lordosis correction and anterior-posterior endplate loading, is poorly understood. PURPOSE Investigators quantified segmental lordosis and anterior-posterior endplate loading achieved over a range of commercially available implant dimensions (heights: 9–21mm, and lordosis: 0–25°). STUDY DESIGN/SETTING In vitro human cadaveric study PATIENT SAMPLE Six cadaveric specimens OUTCOME MEASURES Lordosis and anterior-posterior endplate forces METHODS Six L2–L3 cadaveric segments were used. A 112.5 lb axial load was applied to L2 to simulate forces during upright stance. Segments were instrumented with bilateral pedicle screws and a sequence of LLIFs under fluoroscopy, including: (A) 9mm height with 0°, 6° and 10° lordosis with intact ALL; (B) 9mm height with 0°, 6° and 10° lordosis following ALL resection; (C) 11mm height with 10° and 20° lordosis; (D) 13mm height with 20° lordosis; and (E) 25° lordosis of 13, 15, 17, 19 and 21mm heights. Segmental lordosis and endplate force-maps were collected until anterior expulsion precluded testing completion (n=6, unless otherwise noted). An equivalent loading ratio (ELR=anterior load/total load*100%) was calculated; ELR=80% refers to 80% anterior and 20% posterior edge loading. An ELR between 40–60% is believed to be desirable. RESULTS The average intact L2–L3 lordosis was 8.5°±2.6° (n=6). With the ALL intact, the 9mm 10° spacer increased lordosis to 10.6°±2.9° (P>0.05). Following ALL resection, use of 11mm 10° and 20° spacers increased lordosis to 14.6°±2.2° and 15.3°±1.8° (P>0.05), respectively. The 13mm 20° and 25° LLIF significantly increased lordosis to 16.7°±2.3° and 16.4°±2.3°, respectively, compared to intact and all constructs prior to ALL release (P CONCLUSIONS This study suggests that LLIF implant lordosis and height can be optimized to mitigate excessive anterior loading while maximizing lordosis correction. Following ALL release, larger spacers with greater posterior heights—not necessarily implant lordosis—may have an increased effect on segmental lordosis while reducing anterior edge loading. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Dramatic Inner-Core Tropopause Variability during the Rapid Intensification of Hurricane Patricia (2015)

Abstract Dropsondes with horizontal spacing as small as 4 km were released from the stratosphere in rapidly intensifying Hurricane Patricia (2015) during the Office of Naval Research Tropical Cyclone Intensity experiment. These observations provide cross sections of unprecedented resolution through the inner core of a hurricane. On 21 October, Patricia exhibited a strong tropopause inversion layer (TIL) across its entire circulation, with a maximum magnitude of 5.1 K (100 m)−1. This inversion weakened between 21 and 22 October as potential temperature θ increased by up to 16 K just below the tropopause and decreased by up to 14 K in the lower stratosphere. Between 22 and 23 October, the TIL over the eye weakened further, allowing the tropopause to rise by 1 km. Meanwhile over Patricia’s secondary eyewall, the TIL restrengthened and bulged upward by about 700 m into what was previously the lower stratosphere. These observations support many aspects of recent modeling studies, including eyewall penetration into the stratosphere during rapid intensification (RI), the existence of a narrow inflow layer near the tropopause, and the role of subsidence from the stratosphere in developing an upper-level warm core. Three mechanisms of inner-core tropopause variability are hypothesized: destabilization of the TIL through turbulent mixing, weakening of the TIL over the eye through upper-tropospheric subsidence warming, and increasing tropopause height forced by overshooting updrafts in the eyewall. None of these processes are seen as the direct cause of RI, but rather part of the RI process that includes strong increases in boundary layer moist entropy.

Coupled geomechanics and flow modeling of thermally induced compaction in heavy oil diatomite reservoirs under cyclic steaming

Shallow, heavy oil diatomite reservoirs produced using cyclic steaming are often associated with significant subsidence. In cases where the pore pressure is not allowed to deplete noticeably, observed subsidence suggests a mechanism other than pressure decline is responsible. We perform coupled flow and geomechanics modeling to determine whether thermally induced compaction of the reservoir rock could play an important role in subsidence. First, we model laboratory-scale tests on diatomite samples subjected to mechanical and thermal loads. During these tests, substantial non-recoverable thermal compaction was measured. Using the modified Cam-clay model as a basis, thermally induced compaction is implemented by reducing the size of the yield surface as a function of temperature. This leads to a satisfactory modeling of the test results. Second, this new approach is used to model a symmetric pattern of wells in a generic heavy oil diatomite field produced using cyclic steaming. Results from simulations that consider or neglect thermally induced diatomite compaction show that thermal effects can potentially induce significant inelastic pore volume reduction and substantial subsidence.

The role of subsidence in a weakly unstable marine boundary layer: a case study

Abstract. The diurnal evolution of a cloud free, marine boundary layer is studied by means of experimental measurements and numerical simulations. Experimental data belong to an investigation of the mixing height over inner Danish waters. The mixed-layer height measured over the sea is generally nearly constant, and does not exhibit the diurnal cycle characteristic of boundary layers over land. A case study, during summer, showing an anomalous development of the mixed layer under unstable and nearly neutral atmospheric conditions, is selected in the campaign. Subsidence is identified as the main physical mechanism causing the sudden decrease in the mixing layer height. This is quantified by comparing radiosounding profiles with data from numerical simulations of a mesoscale model, and a large-eddy simulation model. Subsidence not only affects the mixing layer height, but also the turbulent fluctuations within it. By analyzing wind and scalar spectra, the role of subsidence is further investigated and a more complete interpretation of the experimental results emerges.

Observed and Modelled Convective Mixing-Layer Height at Dome C, Antarctica

The mixing-layer height is estimated using measurements from a high resolution surface-layer sodar run at the French-Italian station of Concordia at Dome C, Antarctica during the summer 2011–2012. The temporal and spatial resolution of the sodar allows the monitoring of the mixing-layer evolution during the whole diurnal cycle, i.e. a very shallow nocturnal boundary layer followed by a typical daytime growth. The behaviour of the summer mixing-layer height, variable between about 10- and 300 m, is analyzed as a function of the mean and turbulent structure of the boundary layer. Focusing on convective cases only, the retrieved values are compared with those calculated using a one-dimensional prognostic equation. The role of subsidence is examined and discussed. We show that the agreement between modelled and experimental values significantly increases if the subsidence is not kept fixed during the day. A simple diagnostic equation, which depends on the time-averaged integral of the near-surface turbulent heat flux, the background static stability and the buoyancy parameter, is proposed and evaluated. The diagnostic relation performance is comparable to that of the more sophisticated prognostic model.

A comparative study of structure of vertical motions in the lower troposphere over Pune, a tropical Indian station in March 2004 and 2005 using Wind Profiler data

Abstract. An extended heat wave condition affected Pune (18.31° N, 73.58° E), India and surrounding region during the pre-monsoon month of March 2004, when surface temperatures were observed to be above normal. In contrast, March 2005 showed a long spell of below normal temperatures. The vertical velocity measurements from UHF (404 MHz) Wind Profiler at Pune have been used to understand the role of vertical motions in the lower troposphere in maintenance of long spells of above (in March 2004) and below (in March 2005) normal surface temperatures over the station. The altitude profiles of vertical wind velocities showed different behavior in the two contrasting years 2004 and 2005. It is observed that for a major part of the month and at all heights, downward motions (subsidence) dominate during March 2004. Strong downward motions persisted for spells of 2 to 3 days when high surface temperatures (above 38°C) were recorded over this station. A positive relation between surface temperature anomalies and depth of subsidence points to the role of subsidence. March 2005 showed the persistence of upward motion for longer time duration during morning hours which prevented the surface temperatures from reaching high values with weak subsidence during afternoon hours. This is supported by observation of more frequent and organized thermal plumes extending right into the free troposphere. There are distinct episodes of advective warmings during March 2004 while March 2005 showed weak or absence of temperature advection from north. Hence a combination of meridional transport of heat and persistent subsidence in the lower troposphere seemed to have led to recording of above normal surface temperatures during March 2004 over the station.

Long-term thermal consequences of tectonic activity at Mount Isa, Australia: Implications for polyphase tectonism in the Proterozoic

Abstract Mount Isa is a Palaeo-Mesoproterozoic terrane in Northern Australia characterized by >300 Ma of episodic tectonic activity prior to effective cratonization. This tectonic activity has resulted in dramatic changes in the heat production distribution in the crust and must have been accompanied by long-term changes in thermal regimes. Primary differentiation of crust initially enriched in heat producing elements has been achieved by felsic magmatism over much of the 300 Ma history, often associated with extensional deformation. The flux of heat producing elements from lower to mid-upper crustal levels associated with this magmatism was sufficient to cause long-term lower crustal cooling of at least 200°C. The accumulation of the radiogenic intrusives (which comprise c. 230f surface outcrop and have heat production rates averaging 5.2 µWm −3 ) in the mid-upper crust resulted in a highly stratified heat production distribution. One consequence of this distribution is that small changes in the depth to this heat production, through processes such as deformation, erosion and the deposition of sediments, lead to significant changes in deep crustal temperatures (up to 100°C) and consequently lithospheric strength. These considerations suggest that the long-term evolution of the Mount Isa region partly reflects the progressive concentration of heat-producing elements in the upper crust leading to a long-term increase in lithospheric strength, and eventually to effective cratonization. The long-term cooling and strengthening trend was locally countered by the role of subsidence during basin formation which, through burial of heat producing elements in the existing crust and the accumulation of more heat production in insulating sediments, helped to localize subsequent contractional deformation.

Major geodynamic processes studied from the ECORS deep Seismic profiles in France and adjacent areas

For more than five years, the French ECORS project has obtained deep Seismic profiles across major structural features that are related to the Variscan, Alpine and Pyrenean belts as well as the Permo-Mesozoic subsidence in the Celtic Sea, the English Channel and the Bay of Biscay. Profiles across the orogenic belts show striking similarities such as the flexure of the down-going plate and the geometry of the frontal detachment and related thrusts and nappes whatever the age of the belt. However, straight dipping reflections cutting through large sections of the crust seem to be common in the Variscan belt and are interpreted as late features in its tectonic history. The Tertiary Alpine and Pyrenean belts show extensive crustal thickening and crust-mantle imbrication, while the layered lower crust and its bottom are flat beneath the late Palaeozoic Variscan belt. This is interpreted as a late equilibration of the crust-mantle boundary, which involved deep metamorphism in the crust and occurred between the Permian and the middle Jurassic. The Permo-Jurassic basins reveal an unattenuated lower crust, while both the upper and lower crusts are thinned beneath the Cretaceous-Tertiary ones. Observation does not support the current models of basin formation and nowhere does extension appear to have played a major role in subsidence. The lower crust of the Permo-Jurassic basins may have been reworked and equilibrated after their rifting.

The North American Midcontinent Rift beneath Lake Superior from Glimpce seismic reflection profiling

The Midcontinent rift system is a 1.1‐b.y.‐old structure extending from Kansas, through the Lake Superior region, and into southern Michigan. The rift is filled with thick sequences of basaltic volcanic rocks and clastic sediments. For most of its extent it is buried beneath Paleozoic rocks but can be traced by its strong gravity and magnetic anomalies. The rocks of the rift system are exposed only in the Lake Superior region and comprise the Keweenawan Supergroup. Much of the geology of the Keweenawan is beneath Lake Superior and has only been inferred from potential field studies and seismic refraction studies and extrapolation from on‐shore geology. Seismic reflection surveys by the Great Lakes International Multidisciplinary Program on Crustal Evolution in 1986 imaged much of the deep structure of the rift beneath the lake in detail. The reflection profiles across the rift reveal a deep, asymmetrical central graben whose existence and magnitude was not previously documented. They show that, in addition to crustal sagging documented by previous investigations, normal faulting played a major role in subsidence of the axial region of the rift. A sequence of volcanic and sedimentary rocks, in places greater than 30 km thick, fills the graben. Thinner volcanic and sedimentary units lie on broad flanks of the rift outside of the graben. Near the axis, the prerift crust is thinned to about one fourth of its original thickness, apparently by a combination of low‐angle extensional faulting and ductile stretching or distributed shear. The sense of asymmetry of the central graben changes along the trend of the rift, documenting the segmented nature of the structure and suggesting the existence of accommodation zones between the segments. The location of the accommodation zones is inferred from abrupt disruptions in the Bouguer gravity signature of the rift. Uplift of the central graben occurred when the original graben‐bounding normal faults were reactivated as high‐angle reverse faults with throws of 5 km or more in places. The Midcontinent rift has some striking similarities to some younger passive continental margins. We propose that it preserves a record of nearly complete continental separation which, had it not been arrested, would have created a Middle Proterozoic ocean basin.

Tectonic loading and subsidence of intermontane basins: Wyoming foreland province

Research Article| August 01, 1985 Tectonic loading and subsidence of intermontane basins: Wyoming foreland province E. Sven Hagen; E. Sven Hagen 1Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071 Search for other works by this author on: GSW Google Scholar Mark W. Shuster; Mark W. Shuster 1Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071 Search for other works by this author on: GSW Google Scholar Kevin P. Furlong Kevin P. Furlong 2Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802 Search for other works by this author on: GSW Google Scholar Author and Article Information E. Sven Hagen 1Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071 Mark W. Shuster 1Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071 Kevin P. Furlong 2Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1985) 13 (8): 585–588. https://doi.org/10.1130/0091-7613(1985)13<585:TLASOI>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation E. Sven Hagen, Mark W. Shuster, Kevin P. Furlong; Tectonic loading and subsidence of intermontane basins: Wyoming foreland province. Geology 1985;; 13 (8): 585–588. doi: https://doi.org/10.1130/0091-7613(1985)13<585:TLASOI>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Results of two-dimensional flexural modeling of the northern Bighorn and northern Green River basins in the Wyoming foreland province suggest that these basins formed as flexures in response to loading by basin-margin uplifts and basin sedimentary sequences. The northern Bighorn Basin subsided due to loading by the Beartooth uplift along its western margin. The northern Green River Basin developed as a result of concurrent loading by the Wyoming thrust belt to the west and the Wind River uplift to the east. Tectonic loading from basement-involved uplifts played a major role in subsidence and sedimentation, as evidenced by isopach patterns within each basin. Lithospheric flexural rigidities of 1021 to 1022 newton metres (N·m) can adequately explain subsidence in both basins. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

SOURCE AND ROLE OF PEROXIDASE IN SOIL ORGANIC MATTER OXIDATION IN PAHOKEE MUCK

ABSTRACTWe examined the source of peroxidase (E.C. 1.11.1.7) activity in Pahokee muck, its role in subsidence of this organic soil, the effect of exogenous nutrients in soil peroxidase levels, and oxidation of humic acid by peroxidase produced by a fungus native to Pahokee muck. Amendment of soil wi