South Boundary Research Articles

Evaluation of the South Boundary of the Mu Us Sandy Land When Building the Ming Great Wall

The factors responsible for the sand invasion that occurred during the Ming Dynasty and destroyed the Ming Great Wall have long been the subject of debate.An analysis of the historical records conducted in April 2007 revealed that the Mu Us Sandy Land was located south of the Ming Great Wall before its construction.Therefore,the Ming Great Wall cannot be regarded as a boundary between the sandy land and the grasslands in the Ming Dynasty.Analysis of the historical records and sedimentary documentations indicated that the sandy land,lakes,meadows and grasslands coexisted in the east Mu Us Sandy Land during the Ming dynasty.Desertification,however,was at a low level at that time,and most dunes were fixed when the vegetation coverage around the Ming Great Wall was higher than at present.Desertification became serious as the areas of lakes in the region decreased during the late Ming dynasty;therefore,it is believed that such a situation was the evolution of desertification degree instead of enlargement of the desert area.

Is Oreochromis niloticus invading the Samborombón Bay, Río de la Plata, Argentina?

The Nile tilapia (Oreochromis niloticus) is a species widely cultivated worldwide. In recent decades it was an increasing development of fish farming of this species and the red variety in Argentina and Uruguay. From January to March 2010, four specimens of O. niloticus were captured in the south boundary of Samborombón Bay (S 36° 17´- W 56° 46´), which is the external sector of the Río de la Plata. Probably the collected specimens were released accidentally from hatcheries placed on the banks of aquatic environments in communication with the Samborombón Bay. The patterns and mechanisms of species dispersal are of significant interest, while the interactions among factors determining invasion success often remain poorly understood. Invasion success is influenced by the ability of invading specie to withstand, interactions with native species and oceanographic characteristics of the new habitat. Of four specimens obtained two were females, one in spawning stage. This is the first record of Nile tilapia from a natural environment in Argentina and could indicate the beginning of a new invasion by a non native species.

Conodont biostratigraphy of a more complete Reef Trail Member section near the type section, latest Guadalupian Series type region

The original type section of the Reef Trail Member (uppermost part of the Bell Canyon Formation) is called the Park Boundary Section, and is less than satisfactory in several aspects. We propose a new reference section designated Reef Trail Reference section 1 (RTR1) on the same hill as the original type section. Section RTR1 compensates for some of the Park Boundary Section’s shortcomings, including better exposure of a single measured section with only minor offset. The conodont biostratigraphy of section RTR1 is presented that, when combined with a better set of described correlation intervals, allows for improved correlation to recently discovered, complete, basinal sections in the Patterson Hills. In comparison with the South Boundary basin section, both the Park Boundary and RTR1 sections are missing approximately the upper third of the Reef Trail Member. Transitional conodonts from the basin demonstrate that Jinogondolella crofti evolved directly from J. altudaensis. We formally elevate Clarkina postbitteri hongshuiensis to C. hongshuiensis.

West Antarctic Rift System in the Antarctic Peninsula

Decades after the recognition of the West Antarctic Rift System, and in spite of its global importance, the location and nature of the plate boundary it formed at are unknown east of the Byrd Subglacial Basin. Alternative constructions of the circuit of South Pacific plate boundaries suggest the presence of either a transcurrent plate boundary or a continuation of the extensional rift system. We identify George VI Sound, a curved depression separating Alexander Island from Palmer Land, as the easternmost basin of a rift system that terminated at a triple junction with the Antarctic Peninsula subduction zone. The history of the triple junction's third, transform, arm suggests extension started around 33.5–30 Ma. A more speculatively identified basin further west may have formed earlier during the same episode of rifting, starting around 43 Ma. Proposals of earlier Cenozoic relative motion between East and West Antarctica cannot be verified from this region.

Deep Fault Drilling Project—Alpine Fault, New Zealand

The Alpine Fault, South Island, New Zealand, constitutes a globally significant natural laboratory for research into how active plate-bounding continental faults work and, in particular, how rocks exposed at the surface today relate to deep-seated processes of tectonic deformation, seismogenesis, and mineralization. The along-strike homogeneity of the hanging wall, rapid rate of dextral-reverse slip on an inclined fault plane, and relatively shallow depths to mechanical and chemical transitions make the Alpine Fault and the broader South Island plate boundary an important international site for multi-disciplinary research and a realistic target for an ambitious long-term program of scientific drilling investigations.

Transected folds with opposite patterns in Terena Formation (Ossa Morena Zone, Portugal): anomalous structures resulting from sedimentary basin anisotropies

The Terena Formation is located in the central part of the Ossa-Morena Zone (OMZ) and outcrops in the core of a latter (D3) first order syncline. This Formation is a Lower Devonian flysch and shows an unusual “Z” shape, with a central sector trending nearly N-S, and the tips trending NW-SE. This central sector is crossed by the cleavage (NW-SE) showing an apparent dextral (clockwise) transection pattern, anomalous and opposite to the regional widespread sinistral (anti-clockwise) transpression. The same sector with cartographic dextral transection, shows at outcrop scale, mesoscopic folds with a sinistral transection. During the Lower Devonian a N-S trending basin was developed as an effect of an early tectonic deformation phase. This trough was filled with turbidites and its elongated geometry determined the shape of the main syncline. We propose that the dextral transection pattern, at cartographic scale, result from the superposition of the NW-SE upright S3 cleavage on this major regional structure controlled by a sedimentary trough. The mesoscopic folds, observed on the upper levels of the sedimentary sequence were not influenced by the topographic anisotropy of the basin, and therefore they developed a left transection, according to the regional deformation mechanisms. The “Z” shape of the syncline could be explained as a consequence of two major tectonic shear zones situated along the north and south boundaries of the OMZ, respectively the Tomar-Badajoz-Cordoba Shear Zone and the South Iberian Suture, lined by the Beja-Acebuches Ophiolitic Complex. Both shear zones have a sinistral transpressive character and were active during late Variscan tectonic events.

A Sediment Budget Analysis and Management Strategy for Fort Pierce Inlet, Florida

Quantification of the sediment transport processes in the Fort Pierce Inlet, Florida area and the influence of the inlet onto the adjacent beaches was performed by means of analytical methods. This analysis is formalized as a sediment budget and is based on available survey data, nourishment events, and dredging records of the navigational channel at Fort Pierce Inlet, which cover the period from 1972 to 2002. Available survey data encompass shoreline distances approximately 9.7 km north and 24.7 km south of Fort Pierce Inlet. Three intersurvey periods were examined in this study: 1972 to 1987, 1987 to 1997, and 1997 to 2002. Average annual sediment volume and shoreline changes derived from the profile data collected during these three periods were analyzed. Application of general sediment budget principles established that for the total period from 1972 to 2002, there was an average annual deficit of approximately 12,500 m3/y on the beach south (downdrift) of Fort Pierce Inlet. The general sediment budget suggests that 88,700 m3/y enter the north boundary of Riomar Beach some 18 km north of the inlet; 62,700 m3/y enter the north boundary of St. Lucie County some 10 km north of the inlet; and 43,600 m3/y leave the south boundary of St. Lucie County some 25 km south of the inlet. Application of numerical modeling to develop an understanding and predictability of the performance of beach nourishment south of the inlet was carried out as a supporting method to better understand the littoral processes in the area. Recommendations to improve the sediment management practices, including sand bypassing to restore balance to the south beaches, are presented.

A structuring event of Campanian age in western Venezuela, interpreted from seismic and palaeontological data

Abstract A period of structuring, uplift, non-deposition and/or erosion in the Campanian in Western Venezuela, different from the generally known Late Cretaceous event is proposed to explain: (1) a varying time gap (10 to 1 million years) from east to west across the Maracaibo basin between La Luna and Colón formations; (2) a correlating time gap of 11 million years between the Santonian and Upper Campanian sediments in the Barinas basin; (3) structuring at the Top La Luna seismic horizon in the southwestern, west and central parts of the Maracaibo basin which is not reflected in the overlying section; (4) different thickness patterns in the isopach maps for the units underlying the Top La Luna seismic level and the immediately overlying section at least in area of the Colón Unit; (5) an abrupt change in vitrinite reflectance values in the SW of the basin from 0.47–0.60% above to 1.09–1.80% below the top of La Luna Formation; and (6) fission track ages in the range 70–80 Ma in the Circum-Caribbean. The predominant north–south trend of this structuring suggests that it is related to changes on the dynamics of the South American plate boundary during Campanian that may have involved a major igneous and volcanic event registered 70–80 Ma.

The lattice Boltzmann method and the finite volume method applied to conduction–radiation problems with heat flux boundary conditions

AbstractThis article deals with the implementation of the lattice Boltzmann method (LBM) in conjunction with the finite volume method (FVM) for the solution of conduction–radiation problems with heat flux and temperature boundary conditions. Problems in 1‐D planar and 2‐D rectangular geometries have been considered. The radiating–conducting participating medium is absorbing, emitting and scattering. In the 1‐D planar geometry, the south boundary is subjected to constant heat flux, while in the 2‐D geometry the south and/or the north boundary is at constant heat flux condition. The remaining boundaries are at prescribed temperatures. The energy equation is solved using the LBM and the radiative information for the same is computed using the FVM. In the direct method, by prescribing temperatures at the boundaries, the temperature profile and heat flux are calculated. The computed heat flux values are imposed at the boundaries to establish the correctness of the numerical code in the inverse method. Effects of various parameters such as the extinction coefficient, the scattering albedo, the conduction–radiation parameter, the boundary emissivity and the total heat flux and boundary temperatures are studied on the distributions of temperature, radiative and conductive heat fluxes. The results of the LBM in conjunction with the FVM have been found to compare very well with those available in the literature. Copyright © 2008 John Wiley & Sons, Ltd.

Effects of the Incidence of a Gaussian Temporal Short-Pulse Laser of Different Spatial Profiles on a Two-Dimensional, Rectangular, Inhomogeneous Participating Medium

This article deals with the effects of a short-pulse laser of Gaussian temporal and different spatial profiles on the signals emanating from a two-dimensional rectangular participating medium containing localized inhomogeneities. An incident short-pulse laser of Gaussian temporal profile has spatial loading on the south boundary either as a Gaussian or as a step function. The absorbing and scattering participating medium consists of a localized circular or elliptical inhomogeneity. The extinction coefficient of the inhomogeneity is the same as the containing medium, while its scattering albedo is different. Transmittance and reflectance signals are analyzed for the effects of the extinction coefficient and the spatial profile of the incident short-pulse laser. Spatial distributions of the signals along the boundaries and temporal evolution of the heat flux distributions inside the medium are also studied. The problem is analyzed using the finite-volume method.

Upper plate deformation and seismic barrier in front of Nazca subduction zone: The Chololo Fault System and active tectonics along the Coastal Cordillera, southern Peru

The South America plate boundary is one of the most active subduction zone. The recent Mw = 8.4 Arequipa 2001 earthquake ruptured the subduction plane toward the south over 400 km and stopped abruptly on the Ilo Peninsula. In this exact region, the subduction seismic crisis induced the reactivation of continental fault systems in the coastal area. We studied the main reactivated fault system that trends perpendicular to the trench by detailed mapping of fault related-geomorphic features. Also, at a longer time scale, a recurrent Quaternary transtensive tectonic activity of the CFS is expressed by offset river gullies and alluvial fans. The presence of such extensional fault systems trending orthogonal to the trench along the Coastal Cordillera in southern Peru is interpreted to reflect a strong coupling between the two plates. In this particular case, stress transfer to the upper plate, at least along the coastal fringe, appears to have induced crustal seismic events that were initiated mainly during and after the 2001 earthquake. The seafloor roughness of the subducting plate is usually thought to be a cause of segmentation along subduction zones. However, after comparing and discussing the role of inherited structures within the upper plate to the subduction zone segmentation in southern Peru, we suggest that the continental structure itself may exert some feedback control on the segmentation of the subduction zone and thus participate to define the rupture pattern of major subduction earthquakes along the southern Peru continental margin.

Modelling the impact of possible snowpack emissions of O(3P) and NO2 on photochemistry in the South Pole boundary layer

Environmental context. The study of surface photochemical ozone production on the Antarctic continent has direct relevance to climate change and general air quality and is scientifically noteworthy given the otherwise pristine nature of this environmental region. The identification of possible direct ozone emissions from snow surfaces and their contribution to the already active photochemical pollution present there represents a unique physical phenomenon. This process could have wider global significance for other snow-covered regions and therefore for global climate change. Abstract. O(3P) emissions due to photolysis of nitrate were recently identified from ice surfaces doped with nitric acid. O(3P) atoms react directly with molecular oxygen to yield ozone. Therefore, these results may have direct bearing on photochemical activity monitored at the South Pole, a site already noted for elevated summertime surface ozone concentrations. NO2 is also produced via the photolysis of nitrate and the firn air contains elevated levels of NO2, which will lead to direct emission of NO2. A photochemical box model was used to probe what effect O(3P) and NO2 emissions have on ozone concentrations within the South Pole boundary layer. The results suggest that these emissions could account for a portion of the observed ozone production at the South Pole and may explain the observed upward fluxes of ozone identified there.

Taxonomy and biogeography of the subgenus Eopaederus of the genus Paederus Fabricius (Coleoptera: Staphylinidae: Paederinae) from China

The subgenus Eopaederus Scheerpeltz 1957 belongs to the genus Paederus sensu stricto (Coleoptera: Staphylinidae: Paederinae) and exhibits a wide geographical distribution from the far east of Asia through West Europe. In this paper, we describe two new species: Paederus (Eopaederus) noncurvatus n. sp. and P. (E.) curvatus n. sp. from Hubei in the middle of China. The species P. (E.) basiventris Bernhauer 1933 is resurrected to a valid species and not anymore a synonym of P. (E.) nigricornis Bernhauer 1911. Other two species, P. (E.) birmanus Fauvel 1895 and P. (E.) alternans Walker 1858 are designed to the subgenus Eopaederus based on the materials collected respectively from Yunnan and Hainan, South China, whereas the former P. (E.) birmanus Fauvel 1895 is the first-time-record species to the Chinese fauna. A key to nine Chinese species is presented. Zoogeographic analyses show that the subgenus track can be divided into three parts (namely Asia, Middle East and Europe) and each one possesses its own endemic species. Likewise, endemic species ranges can also designed as Europe type, Middle East type, or South and East Asia type. Along the south boundary of Himalayas (Qinghai-Tibet Plateau) through South China, species richness and endemism are obviously higher than in other regions.

Modelling the impact of oxygenated VOC and meteorology upon the boundary layer photochemistry at the South Pole

AbstractA chemistry box model is used to explore implications of recent measurements of methyl hydroperoxide (MHP) across Antarctica and their influence upon high ozone events in the South Pole boundary layer. To reconcile, recent data models suggest that chemistry and meteorology play an important role. Copyright © 2007 Royal Meteorological Society

Collision leading to multiple-stage large-scale extrusion in the Qinling orogen: Insights from the Mianlue suture

The geologic framework of the Phanerozoic Qinling–Dabie orogen was built up through two major suturing events of three blocks. From north to south these include the North China craton (including the north Qinling block), the Qinling–Dabie microblock, and the South China craton (including the Bikou block), separated by the Shangdan and Mianlue sutures. The Mianlue suture zone contains evidence for Mesozoic extrusion tectonics in the form of major strike–slip border faults surrounding basement blocks, a Late Paleozoic ophiolite and a ca. 240–200 Ma thrust belt that reformed by 200–150 Ma thrusts during A-type (intracontinental) subduction. The regional map pattern shows that the blocks are surrounded by complexly deformed Devonian to Early Triassic metasandstones and metapelites, forming a regional-scale block-in-matrix mélange fabric. Five distinct tectonic units have been recognized in the belt: (1) basement blocks including two types of Precambrian basement, crystalline and transitional; (2) continental margin slices including Early Paleozoic strata, and Late Paleozoic fluviodeltaic sedimentary rocks, proximal and distal fan clastics, reflecting the development of a north-facing rift margin on the edge of the South China plate; (3) out of sequence oceanic crustal slices including strongly deformed postrift, deep-water sedimentary rocks, sheeted dikes, basalts, and mafic–ultramafic cumulates of a Late Paleozoic ophiolite suite, developing independent of the rift margin in a separate basin; (4) out-of-sequence island-arc slices; (5) accretionary wedge slices. All the tectonic units were deformed during three geometrically distinct deformation episodes (D 1, D 2 and D 3 during 240–200 Ma). Units 2–4 involved southward thrusting and vertical then southward extrusion of about 20 km of horizontal displacement above the autochthonous basement during the D 1 episode. Thrust slices 20 km south of the Mianlue suture are related to this vertical extrusion due to the same rock assemblages, ages and kinematics. The D 2 and D 3 episodes folded all the units in a thick-skinned style about east–west (D 2) and west–northwest (D 3) axes in the Mianlue suture zone. An early foreland propagating sequence of accretion of Late Paleozoic rocks deposited above the Yangtze craton is not involved in D 1 deformation but is temporally equivalent to the D 2 and D 3 deformation in the Mianlue suture. Two stages of strike–slip faulting mainly occurred at the end of D 2 and D 3, respectively. During D 2 deformation, the Bikou block was obliquely indented to the ESE into the Mianlue suture, rather than being thrust over the Mianlue suture from the north as a part of the Qinling–Dabie microblock. During D 3 deformation, however, the Bikou block was bounded by the south boundary fault of the Mianlue suture, and the Yangpingguan fault on the south. These faults are coeval strike–slip faults, but of opposite senses, and accommodated minor southwestward extrusion of the Bikou block into Songpan–Ganze orogen. The other basement blocks north of the Mianlue suture were extruded eastward by about 20 km of lateral displacement, based on the offset of the Wudang dome, during the D 3 episode due to the northeastward indentation of the Hannan complex of the South China craton. Post-D 3 emplacement of granite, cutting across the strike–slip faults such as the Mianlue suture, provides a minimum age of 200 Ma for D 3 deformation. Therefore, based on insights from the evolution of the Mianlue suture, the D 2 and D 3 episodes in the Mianlue suture and its neighbors are not responsible for and associated with the two-stage extrusion of the Dabie UHP-HP terranes from the Foping dome to the present erosional surface (more than 350 km).

Simulations of water resource environmental changes in China during the last 20 000 years by a regional climate model

We utilize a regional climate model with detailed land surface processes (RegCM2) to simulate East Asian monsoon climates at 0 ka, 6 ka and 21 ka BP, and evaluate the changes in hydrology process, including vapor transportation, precipitation, evapotranspiration and runoff in the eastern and western China during these periods. Results indicate that the Tibetan Plateau climate presents a wet–cold status during the LGM while it exhibits a wet–warm climate at 6 ka BP. The LGM wetter climate over the Tibetan Plateau mainly results from the increased vapor inflow through its south boundary, while the increase in the vapor import over the Tibetan Plateau at 6 ka BP mostly sources from its west boundary. The increase in the LGM runoff over the Tibetan Plateau is mainly caused by the decrease in evapotranspiration, while the increase in runoff at the 6 ka BP mainly by the enhanced precipitation. Eastern China (including southern China) presents a dry status during the LGM, which precipitation and runoff decreases significantly due largely to weakened Asian summer monsoon that results in the decreased vapor inflow through the south boundary of eastern China. The variation pattern in the hydrological cycle in eastern China is contrary to that in western China during the LGM. The increase in precipitation and runoff at 6 ka BP in eastern China is tightly related to the strong Asian summer monsoon that leads to increased vapor import through the south boundary. Long term decrease trend in precipitation and runoff in northern China since the last 20 000 years may be attributed to the steady increase in vapor export through the east boundary as a result of the changes of East Asian monsoon and the adjustments of local atmospheric circulations in this area.

Seismic potential of Southern Italy

To improve estimates of the long-term average seismic potential of the slowly straining South Central Mediterranean plate boundary zone, we integrate constraints on tectonic style and deformation rates from geodetic and geologic data with the traditional constraints from seismicity catalogs. We express seismic potential (long-term average earthquake recurrence rates as a function of magnitude) in the form of truncated Gutenberg–Richter distributions for seven seismotectonic source zones. Seismic coupling seems to be large or even complete in most zones. An exception is the southern Tyrrhenian thrust zone, where most of the African–European convergence is accommodated. Here aseismic deformation is estimated to range from at least 25% along the western part to almost 100% aseismic slip around the Aeolian Islands. Even so, seismic potential of this zone has previously been significantly underestimated, due to the low levels of recorded past seismicity. By contrast, the series of 19 M6–7 earthquakes that hit Calabria in the 18th and 19th century released tectonic strain rates accumulated over time spans up to several times the catalog duration, and seismic potential is revised downward. The southern Tyrrhenian thrust zone and the extensional Calabrian faults, as well as the northeastern Sicilian transtensional zone between them (which includes the Messina Straits, where a destructive M7 event occurred in 1908), all have a similar seismic potential with minimum recurrence times of M ≥ 6.5 of 150–220 years. This potential is lower than that of the Southern Apennines ( M ≥ 6.5 recurring every 60 to 140 years), but higher than that of southeastern Sicily (minimum M ≥ 6.5 recurrence times of 400 years). The high seismicity levels recorded in southeastern Sicily indicate some clustering and are most compatible with a tectonic scenario where the Ionian deforms internally, and motions at the Calabrian Trench are small. The estimated seismic potential for the Calabrian Trench and Central and Western Sicily are the lowest (minimum M ≥ 6.5 recurrence times of 550–800 years). Most zones are probably capable of generating earthquakes up to magnitudes 7–7.5, with the exception of Central and Western Sicily where maximum events sizes most likely do not exceed 7.

Simulation of CFCs Distribution in the North Pacific Using a Basin-Wide Ocean General Circulation Model with an Open Boundary

A basin-wide ocean general circulation model with open boundaries is used to study the uptake and distribution of CFCs in the North Pacific. The air-sea flux and distribution of CFC-11 are computed. Based on the simulation the influences of different isopycnal diffusion coefficients and open boundaries on the distribution of CFC-11 are examined. Opening the south boundary of the model can improve the simulation of CFC-11 in the area south of the equator dramatically. Increasing the isopycnal diffusivity can make the water with high CFC-11 concentration at 137°E and 165°E have stronger transports southward and downward so to cover a larger area. The simulated distribution of CFC-11 can be improved greatly with the increasing isopycnal diffusivity in the western North Pacific. The west North Pacific is an important sink of CFC-11 and the eastern equator is also a sink.

Energetic Electrons as a Field Line Topology Tracer in the High Latitude Boundary/CUSP Region: Cluster Rapid Observations

Energetic electrons (e.g., 50 keV) travel along field lines with a high speed of around 20 R E s −1. These swift electrons trace out field lines in the magnetosphere in a rather short time, and therefore can provide nearly instantaneous information about the changes in the field configuration in regions of geospace. The energetic electrons in the high latitude boundary regions (including the cusp) have been examined in detail by using Cluster/RAPID data for four consecutive high latitude/cusp crossings between 16 March and 19 March 2001. Energetic electrons with high and stable fluxes were observed in the time interval when the IMF had a predominately positive B z component. These electrons appeared to be associated with a lower plasma density exhibiting no obvious tailward plasma flow (< 20 keV). On the other hand, no electrons or only spike-like electron events have been observed in the cusp region during southward IMF. At that time, the plasma density was as high as that in the magnetosheath and was associated with a clear tailward flow. The fact that no stable energetic electron fluxes were observed during southward IMF indicates that the cusp has an open field line geometry. The observations indicate that both the South and North high latitude magnetospheric boundary regions (including both North and South cusp) can be energetic particle trapping regions. The energetic electron observations provide new ways to investigate the dynamic cusp processes. Finally, trajectory tracing of test particles has been performed using the Tsyganenko 96 model; this demonstrates that energetic particles (both ions and electrons) may be indeed trapped in the high latitude magnetosphere.

Neotectonics of the Offshore Oak Ridge Fault near Ventura, Southern California

The Oak Ridge fault is a large-offset, south-dipping reverse fault that forms the south boundary of the Ventura Basin in southern California. Previous research indicates that the Oak Ridge fault south of the town of Ventura has been inactive since 200–400 ka ago and that the fault tip is buried by ∼ 1 km of Quaternary sediment. However, very high-resolution and medium-resolution seismic reflection data presented here show a south-dipping fault, on strike with the Oak Ridge fault, that is truncated at 80 m depth by an unconformity that is probably at the base of late Pleistocene and Holocene sediment. Furthermore, if vertically aligned features in seismic reflection data are eroded remnants of fault scarps, then a subsidiary fault within the Oak Ridge system deforms the shallowest imaged sediment layers. We propose that this subsidiary fault has mainly left-slip offset. These observations of Holocene slip on the Oak Ridge fault system suggest that revision of the earthquake hazard for the densely populated Santa Clara River valley and the Oxnard coastal plain may be needed.