scholarly journals Burial Ages Imply Miocene Uplift of Lu Mountain in East China due to Crustal Shortening

2021 ◽  
Vol 9 ◽  
Author(s):  
Zhiyong Han ◽  
Rouxian Pan ◽  
Xusheng Li ◽  
Yujia Liu ◽  
Yufang Li ◽  
...  
Keyword(s):  
Hanging Wall ◽  
Vertical Displacement ◽  
East China ◽  
Western Boundary ◽  
Reverse Fault ◽  
Boundary Fault ◽  
Denudation Rates ◽  
Eastern Boundary ◽  
Field Evidence ◽  
Tectonic Style

Confined by the eastern and western boundary faults, Lu Mountain has long been considered a block mountain uplifted due to Mesozoic and Cenozoic crustal deformation in East China. However, the formation and evolution of this block mountain are still debated. In this study, the eastern boundary fault is investigated to confirm the tectonic style of the block mountain. In addition, the burial ages of sediments on the fans of the eastern piedmont are measured by 26Al/10Be dating to evaluate the denudation rate. Field evidence indicates the presence of a reverse fault (Xingzi reverse fault) acting as the eastern boundary fault, which demonstrates that the block mountain is not a horst as once thought but an extrusion structure. Corrected 26Al/10Be burial ages show that the sediments on the high-level fans were deposited at approximately 1.1–1.2 Ma, which indicates denudation rates ranging from 0.033 to 0.082 m/kyr. The vertical displacement along the Xingzi reverse fault is estimated to be at least 1,100 m. The hanging wall could have been eroded to its present position within 13–33 Myr at the above denudation rates. Combining our results with regional geological and geomorphological evidence, we suggest that Lu Mountain was mainly uplifted in the Miocene due to crustal compression deformation, which may have been a response to the movement of the Pacific plate.

scholarly journals Grenville Foreland Deformation and Sedimentation in Southwest Ohio Indicated by Reprocessed Seismic Reflection Profiles near Middletown, Ohio, USA

2020 ◽  
Vol 120 (2) ◽  
pp. 39
Author(s):  
David J. Peterman ◽  
Ernest C. Hauser ◽  
Doyle R. Watts
Keyword(s):  
Cross Section ◽  
Seismic Reflection ◽  
Vertical Displacement ◽  
Reverse Fault ◽  
Seismic Line ◽  
The North ◽  
North American Craton ◽  
Tectonic Style ◽  
Seismic Reflection Profiles ◽  
Depositional Setting

The late Mesoproterozoic to early Neoproterozoic Middle Run Formation contains vital information about the crustal evolution of the North American Craton. Four reprocessed seismic reflection lines in the vicinity of the AK Steel facility in Middletown, Ohio, provide new insights into the structural and depositional setting of the Middle Run Formation in this region. A residual statics solution improved the resolution and coherency of reflections in these profiles that underlie the Cambrian Mount Simon Sandstone. Reprocessing revealed gently inclined, west-southwest-dipping reflectors and the occurrence of an angular unconformity between the Middle Run Formation and the overlying Paleozoic strata. The weak and discontinuous seismic reflection character of the Middle Run Formation in these seismic lines overlies a sequence of stronger parallel reflections that are like those observed on the eastward ODNR-1-88 seismic line located near core hole DGS 2627, the stratotype of the Middle Run Formation. This inferred thickness indicates that the basin in which the Middle Run Formation was deposited ranges from at least 670 to 1,128 m (2,200 to 3,700 ft) deep at the AK Steel area and dips gently west-southwest, which is in contrast with the moderate easterly dip observed on the ODNR-1-88 seismic line to the northeast. Correlation of these features across the 10 km (approximately 6 mi) cross-strike gap between the AK Steel lines and the ODNR-1-88 seismic line suggests the presence of a reverse fault with approximately 792 m (2,600 ft) of estimated vertical displacement. A regional cross section—including the WSU 1990 seismic line eastward of the ODNR-1-88 line—exhibits a faulted west-verging asymmetric syncline in near proximity to the Grenville Front. This cross section also shows that deformation of the Middle Run Formation and the underlying layered sequence exhibits a consistent tectonic style of reverse faulting and folding that developed in response to Grenville Front tectonism.

PALEOSTRESS ANALYSIS TO INTERPRET THE LANDSLIDE MECHANISM: A CASE STUDY IN PARANGTRITIS, YOGYAKARTA

2015 ◽  
Vol 2 (2) ◽  
Author(s):  
Salahuddin Husein ◽  
Ignatius Sudarno ◽  
Subagyo Pramumijoyo ◽  
Dwikorita Karnawati
Keyword(s):  
Mass Movement ◽  
Western Boundary ◽  
Northern Boundary ◽  
Boundary Fault ◽  
Landslide Mechanism ◽  
Eastern Boundary ◽  
Sliding Mechanism ◽  
Main Fault ◽  
Paleostress Analysis

Paleostress analysis on the landslide boundary faults is able to explain the sliding mechanism. This method is particularly useful to study a paleolandslide. About 30 striated fault planes from the Parangtritis paleo-landslide, located in the Yogyakarta coastline, were analyzed to define their principle stress axes. The eastern boundary fault, named as the Girijati Fault, was the main fault responsible for the mass movement and leaving a considerable steep cliff. It moved normal in a left lateral sense with ENE – WSW extension and dragged the rockmass southward, creating a NNW – SSW extension along the Parangtritis Fault and turn it into the western boundary fault. The rockmass slided along the stratigraphic contact between the underlying Nglanggran Formation and the overlying Wonosari Formation, created a semi-circular crown cliff as the northern boundary and produced some isolated topographic highs of the thrust block near the toe. Keywords: Paleostress, landslide boundary, fault, paleolandslide

scholarly journals Radiating Instability of a Meridional Boundary Current

2008 ◽  
Vol 38 (10) ◽  
pp. 2294-2307 ◽  
Author(s):  
Hristina G. Hristova ◽  
Joseph Pedlosky ◽  
Michael A. Spall
Keyword(s):  
Western Boundary ◽  
Far Field ◽  
Boundary Current ◽  
Important Conclusion ◽  
Western Boundary Currents ◽  
Horizontal Structure ◽  
Boundary Currents ◽  
Zonal Jets ◽  
Eastern Boundary ◽  
Eastern Boundary Current

Abstract A linear stability analysis of a meridional boundary current on the beta plane is presented. The boundary current is idealized as a constant-speed meridional jet adjacent to a semi-infinite motionless far field. The far-field region can be situated either on the eastern or the western side of the jet, representing a western or an eastern boundary current, respectively. It is found that when unstable, the meridional boundary current generates temporally growing propagating waves that transport energy away from the locally unstable region toward the neutral far field. This is the so-called radiating instability and is found in both barotropic and two-layer baroclinic configurations. A second but important conclusion concerns the differences in the stability properties of eastern and western boundary currents. An eastern boundary current supports a greater number of radiating modes over a wider range of meridional wavenumbers. It generates waves with amplitude envelopes that decay slowly with distance from the current. The radiating waves tend to have an asymmetrical horizontal structure—they are much longer in the zonal direction than in the meridional, a consequence of which is that unstable eastern boundary currents, unlike western boundary currents, have the potential to act as a source of zonal jets for the interior of the ocean.

The Connemara Eastern Boundary Fault: A correction

2017 ◽  
Vol 35 (1) ◽  
pp. 55-56
Author(s):  
Alan Lees ◽  
Martin Feely
Keyword(s):  
Boundary Fault ◽  
Eastern Boundary

scholarly journals Meridional Overturning Circulations Driven by Surface Wind and Buoyancy Forcing

2015 ◽  
Vol 45 (11) ◽  
pp. 2701-2714 ◽  
Author(s):  
Michael J. Bell
Keyword(s):  
Heat Loss ◽  
Water Mass ◽  
Surface Wind ◽  
Surface Heat ◽  
Meridional Overturning Circulation ◽  
Western Boundary ◽  
Eastern Boundary ◽  
Transformation Rates ◽  
Meridional Overturning ◽  
Water Mass Transformations

AbstractThe meridional overturning circulation (MOC) can be considered to consist of a downwelling limb in the Northern Hemisphere (NH) and an upwelling limb in the Southern Hemisphere (SH) that are connected via western boundary currents. Steady-state analytical gyre-scale solutions of the planetary geostrophic equations are derived for a downwelling limb driven in the NH solely by surface heat loss. In these solutions the rates of the water mass transformations between layers driven by the surface heat loss determine the strength of the downwelling limb. Simple expressions are obtained for these transformation rates that depend on the most southerly latitudes where heat loss occurs and the depths of the isopycnals on the eastern boundary. Previously derived expressions for the water mass transformation rates in subpolar gyres driven by the Ekman upwelling characteristic of the SH are also summarized. Explicit expressions for the MOC transport and the depths of isopycnals on the eastern boundary are then derived by equating the water mass transformations in the upwelling and downwelling limbs. The MOC obtained for a “single-basin” two-layer model is shown to be generally consistent with that obtained by Gnanadesikan. The model’s energetics are derived and discussed. In a world without a circumpolar channel in the SH, it is suggested that the upwelling limb would feed downwelling limbs in both hemispheres. In a world with two basins in the NH, if one of them has a strong halocline the model suggests that the MOC would be very weak in that basin.

Matrilineal Kinship among the Kunda

Africa ◽  
1958 ◽  
Vol 28 (3) ◽  
pp. 207-224 ◽  
Author(s):  
J. P. Van S. Bruwer
Keyword(s):  
Western Boundary ◽  
The South ◽  
Administrative District ◽  
Eastern Province ◽  
The North ◽  
Eastern Boundary ◽  
Game Reserve ◽  
Opening Paragraph

Opening ParagraphThe Kunda, a matrilineal Bantu people numbering about 20,000, occupy part of the Luangwa valley in the Eastern Province of Northern Rhodesia. Their country, located within the administrative district of Fort Jameson, stretches along the east bank of the Luangwa between the Lusangazi in the south and the Lukuzi in the north. Its western boundary is the Luangwa river proper; across the river a game reserve, stretching up from the Muchinga range, forms an uninhabited barrier between them and the tribes beyond the mountains. The eastern boundary is less clearly demarcated, but marches with the territory of the adjacent Cewa. To the south and north live the Nsenga and Bisa respectively. All these adjacent tribes are matrilineal.

scholarly journals A vertical-mode decomposition to investigate low-frequency internal motion across the Atlantic at 26° N

Ocean Science ◽  
2012 ◽  
Vol 8 (3) ◽  
pp. 345-367 ◽  
Author(s):  
Z. B. Szuts ◽  
J. R. Blundell ◽  
M. P. Chidichimo ◽  
J. Marotzke
Keyword(s):  
Low Frequency ◽  
Western Boundary ◽  
Original Signal ◽  
Baroclinic Mode ◽  
Eastern Boundary ◽  
Mode Decomposition ◽  
Oceanic Response ◽  
Vertical Density ◽  
Baroclinic Modes ◽  
Pressure Perturbations

Abstract. Hydrographic data from full-depth moorings maintained by the Rapid/\\-MOCHA project and spanning the Atlantic at 26° N are decomposed into vertical modes in order to give a dynamical framework for interpreting the observed fluctuations. Vertical modes at each mooring are fit to pressure perturbations using a Gauss-Markov inversion. Away from boundaries, the vertical structure is almost entirely described by the first baroclinic mode, as confirmed by high correlation between the original signal and reconstructions using only the first baroclinic mode. These first baroclinic motions are also highly coherent with altimetric sea surface height (SSH). Within a Rossby radius (45 km) of the western and eastern boundaries, however, the decomposition contains significant variance at higher modes, and there is a corresponding decrease in the agreement between SSH and either the original signal or the first baroclinic mode reconstruction. Compared to the full transport signal, transport fluctuations described by the first baroclinic mode represent <25 km of the variance within 10 km of the western boundary, in contrast to 60 km at other locations. This decrease occurs within a Rossby radius of the western boundary. At the eastern boundary, a linear combination of many baroclinic modes is required to explain the observed vertical density profile of the seasonal cycle, a result that is consistent with an oceanic response to wind-forcing being trapped to the eastern boundary.

scholarly journals Influence of hydrodynamic mixing on the distribution of dissolved organic carbon in the East China Sea and the northwest Pacific

2018 ◽  
Author(s):  
Ling Ding ◽  
Tiantian Ge ◽  
Xuchen Wang
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
East China Sea ◽  
Kuroshio Extension ◽  
Water Masses ◽  
East China ◽  
Northwest Pacific ◽  
Western Boundary ◽  
Oxygen Utilization ◽  
China Sea

Abstract. Oceanic dissolved organic carbon (DOC) is one of the largest carbon reservoirs on Earth, and its distribution and behavior play important roles in carbon cycling and biogeochemical processes in the ocean. Here, we report distribution and concentrations of DOC for water samples collected from the shelf-edge and slope regions in East China Sea (ECS) and the Kuroshio Extension (KE) in the northwestern North Pacific (NP) during two cruises in 2014–2015. Concentrations of DOC were 45–88 µM in the ECS and 35–65 µM in the KE. In addition to biological processes, the distribution of DOC is largely controlled by hydrodynamic mixing of different water masses. The intrusion of Kuroshio Current could dilute DOC concentrations at stations in the outer shelf and slope ranges of the ECS. The inverse correlation of DOC with apparent oxygen utilization (AOU) suggests that DOC oxidation only contributes 18 % of the oxygen consumption in the ECS slope waters. In contrast, concentrations of DOC in the KE were significantly lower in surface waters, and a relatively low and stable DOC level (~ 40 µM) was found in deep waters. The observed spatial variations of DOC in the upper 700 m among the stations in the KE were largely influenced by the mixing of the two water masses carried by the two major western boundary currents: Kuroshio and Oyashio that mix and form the KE. The hydrodynamic processes play important roles not only in the distribution of DOC but nutrients as well, thus could have major impact to primary production and ecosystems in the KE region.

scholarly journals Observed Transport Variability of the Atlantic Subtropical Cells and Their Connection to Tropical Sea Surface Temperature Variability

2021 ◽  
Author(s):  
Franz Philip Tuchen ◽  
Joke F. Lübbecke ◽  
Peter Brandt ◽  
Yao Fu
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Time Scales ◽  
Wind Stress ◽  
Large Scale ◽  
Sea Surface ◽  
Ekman Transport ◽  
Western Boundary ◽  
Eastern Boundary ◽  
Stress Changes

&lt;p&gt;The shallow meridional overturning cells of the Atlantic Ocean, the subtropical cells (STCs), consist of poleward Ekman transport at the surface, subduction in the subtropics, equatorward flow at thermocline level and upwelling along the equator and at the eastern boundary. In this study, we provide the first observational estimate of transport variability associated with the horizontal branches of the Atlantic STCs in both hemispheres based on Argo float data and supplemented by reanalysis products.&lt;/p&gt;&lt;p&gt;Thermocline layer transport convergence and surface layer transport divergence between 10&amp;#176;N and 10&amp;#176;S are dominated by seasonal variability. Meridional thermocline layer transport anomalies at the western boundary and in the interior basin are anti-correlated and partially compensate each other at all resolved time scales. It is suggested that the seesaw-like relation is forced by the large-scale off-equatorial wind stress changes through low-baroclinic-mode Rossby wave adjustment. We further show that anomalies of the thermocline layer interior transport convergence modulate sea surface temperature (SST) variability in the upwelling regions along the equator and at the eastern boundary at time scales longer than 5 years. Phases of weaker (stronger) interior transport are associated with phases of higher (lower) equatorial SST. At these time scales, STC transport variability is forced by off-equatorial wind stress changes, especially by those in the southern hemisphere. At shorter time scales, equatorial SST anomalies are, instead, mainly forced by local changes of zonal wind stress.&lt;/p&gt;

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