scholarly journals Piedmont deposits as seismic energy dissipators, Sierras Pampeanas of Argentina

2021 ◽  
Vol 3 (12) ◽  
Author(s):  
Adolfo Antonio Gutiérrez ◽  
Ricardo Mon ◽  
Ahmad Arnous ◽  
Rodolfo Germán Aranda-Viana
Keyword(s):  
Seismic Energy ◽  
Tectonic Activity ◽  
Study Region ◽  
Sierras Pampeanas ◽  
The North ◽  
Neotectonic Deformation ◽  
Drainage Channels ◽  
Energy Dissipators ◽  
Energy Dissipated ◽  
Fault Scarps

AbstractThis study shows the neotectonic deformation occurred in the southern piedmont of the Cumbres Calchaquíes, in the Amaicha and Tafí valleys. Neotectonic deformation manifests itself through faults, folds and diversions of drainage channels. The Amaicha valley is bounded to the north by the Tafí del Valle fault and to the south by the Los Cardones fault. The Cumbres Calchaquíes ride over the Sierra de Aconquija through the Los Cardones and Carapunco faults. The Carapunco fault also has a synestral component, responsible for generating an imbricated system of contractional fractures. In the study region many earthquakes of ≥ 3 and ≥ 4 magnitude coincide with regional faults evidencing its neotectonic activity. The seismic energy dissipated through materials with less cohesion that form the fill of the valleys, generating discrete fault scarps and strongly folded conglomerate strata. The foothills deposits of the Cumbres Calchaquíes absorbed most of the seismic energy released during the reactivation of the faults. Tectonic activity is deforming 630 a BP deposits in the Cumbres Calchaquíes piedmont.

North-South variation in tectonic activity along left-stepping extensional basins revealed by morphometric analysis: Gofa province, southwestern Ethiopia, East Africa

2020 ◽  
Author(s):  
Asfaw Erbello ◽  
Gerold Zeilinger ◽  
Manfred R. Strecker
Keyword(s):  
Strain Localization ◽  
Tectonic Activity ◽  
Southern Ethiopia ◽  
Climatic Data ◽  
Long Term Effects ◽  
Study Region ◽  
The North ◽  
Hypsometric Integral ◽  
Mountain Front ◽  
Channel Steepness

<p>We report on the morphotectonic characteristics in the tectonically active Southern Ethiopia Rift (SER) based on the analysis of high-resolution topographic data (12m TanDemX) and satellite imagery. The study region is a wide zone of distributed extension at the transition from the SER and the Northern Kenyan Rift and reflects the long-term effects of episodic tectonic events in the landscape.  The uplifted footwall margins of the north-south trending and left stepping ēn ēchelon basins of the SER constitute Pan-African basement rocks in the southern and central part (Chew Bahir, Mali-Dancha and part of Beto) and tectonized Miocene basalts in the north (Sawula). As such this region is an ideal location to record the tectonic characteristics of a major transition zone between two rift systems. Some of the unsolved problems in this area concern the degree of tectonic activity, spatiotemporal variations in the amount of extension, and the nature of kinematic linkage between different faults. To examine these issues, we calculated morphometric indices of river catchments along major fault-bounded blocks as proxies for tectonic activity and combined this information with structural, seismicity, and climatic data. <br>We determined basin asymmetry, hypsometric integral, mountain-front sinuosity, valley floor to valley-width-height ratio, basin shape, the range of basin form and mean slope; additionally, we calculated knickpoint distributions and channel-steepness index values from 89 sub-basins. Combined, the data suggest a significant north-south variation in extensional processes. For example, in the northern basins knickpoints are generally located in upstream areas near the channel heads. They are rare in the Mali-Dancha basin, whereas in the Chew Bahir basin a distinct distribution along the main channel is recognized from basin head to the mountain front. In the south the knickpoints are closest to the mountain front. This unique spatial arrangement of knickpoints in rivers draining the footwalls of extensional blocks in the north-south transect suggests a gradual, southward-directed shift in extensional deformation and recent tectonic activity. The normalized channel-steepness index value is generally small; however, it also exhibits a significant southward trend with higher values (i.e., tectonic activity). Additionally, the normalized channel steepness indices are higher at orthogonally interacting faults compared to neighbouring areas, suggesting strain localization. <br>Our new results suggest a northward increase in the geomorphic maturity of the analyzed sub-basins from Chew Bahir (juvenile) to Sawula (mature), which is compatible with a northward decrease in tectonic activity and a dominance of erosional processes. This is consistent with published, northward-decreasing extension rates and the degree of regional seismicity. Furthermore, strain localization at interacting faults suggests kinematic linkage of the left-stepping bounding faults of the sub-basins.</p>

Les surfaces a Rhizocorallium de l'Aptien inferieur sur la bordure meridionale du bassin vocontien (France Sud-Est), marqueurs de dynamiques locales; leur relation avec un evenement anoxique global

2000 ◽  
Vol 171 (2) ◽  
pp. 229-238 ◽  
Author(s):  
Pierre Cotillon ◽  
Martial Banvillet ◽  
Christian Gaillard ◽  
Daniele Grosheny ◽  
Davide Olivero
Keyword(s):  
Black Shales ◽  
Tectonic Activity ◽  
Carbonate Sediment ◽  
The West ◽  
The North ◽  
Current Activity ◽  
Lower Aptian ◽  
Anoxic Event ◽  
Fault Scarps ◽  
Short Event

Abstract On the North-Provence margin, an omission surface with Rhizocorallium often characterizes the sub-Aptian discontinuity between Eocretaceous carbonates and Aptian-Albian marls. This discontinuity is recorded in various successions described along a palaeoslope joining the Vocontian Basin and the Provence platform, between the Jabron valley in the west and the Var valley in the east. The successions including Aptian marls always exhibit an omission surface with Rhizocorallium. Through this area, the Aptian discontinuity equates to at least part of the Goguel Level. The latter is represented by black shales occurring in the Vocontian Basin at the top of Deshayesi zone and is a regional expression of the global anoxic event OAE1a. Thus, the surface with Rhizocorallium can be regarded, on the North-Provence margin, as a marker coincident with the onset of the anoxic event which, in the Vocontian basin, succeeded to a nannoconid crisis. Representing a short event, the surface is also a marker of various processes: (1) current activity, deduced from a dominant orientation of Rhizocorallium. The Barremian-early Aptian carbonate succession is strongly eroded by the formerly more active currents along the Peipin Channel, south-east of Sisteron; these currents also led to the omission of the Bedoulian (= carbonate Lower Aptian) to upper Valanginian series from the top of the hemipelagic palaeoreliefs in the eastern Castellane arc; (2) tectonic activity in the Lower Aptian, marked by N080 degrees to N100 degrees extension faults and slumping of a semi-lithified carbonate sediment. Slumped material and fault scarps are burrowed with Rhizocorallium; (3) differential lithification of the Barremian limestones which has led to distinctive types of current erosion.

scholarly journals Increasing benthic vent formation: a threat to Japan’s ancient lake

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Michio Kumagai ◽  
Richard D. Robarts ◽  
Yasuaki Aota
Keyword(s):  
Lake Biwa ◽  
Autonomous Underwater Vehicle ◽  
Tohoku Earthquake ◽  
Water Source ◽  
Tectonic Activity ◽  
Drinking Water Source ◽  
Sudden Increase ◽  
The North ◽  
Slow Earthquakes ◽  
Near Future

AbstractAn autonomous underwater vehicle (AUV) was deployed in Lake Biwa from 2000 to 2012. In December 2009, ebullition of turbid water was first found in the deepest area (> 90 m) of the North Basin. Follow-up investigations in April and December 2010 and January 2012 confirmed the existence of benthic vents similar to the vents observed in other deep lakes. Importantly, vent numbers per unit travel distance in Lake Biwa dramatically increased from only two vents (0.37 vents km−1) in December 2009 to 54 vents (5.28 vents km−1) in January 2012, which could be related to recent tectonic activity in Japan, e.g., the M9.1 Tohoku earthquake in March 2011 and slow earthquakes along the Nankai Trough from 2006 to 2018. Continuous back-up investigations from 2014 to 2019 revealed additional benthic vents in the same area. The sudden increase in benthic vent activity (liquid and gaseous ebullitions) have significant potential to alter lake biogeochemistry and, ultimately, degrade Japan’s major drinking water source and may be a harbinger of major crustal change in the near future.

scholarly journals Anomalous azimuthal variations with 360° periodicity of Rayleigh phase velocities observed in Scandinavia

2020 ◽  
Vol 224 (3) ◽  
pp. 1684-1704
Author(s):  
Alexandra Mauerberger ◽  
Valérie Maupin ◽  
Ólafur Gudmundsson ◽  
Frederik Tilmann
Keyword(s):  
Seismic Anisotropy ◽  
Broad Band ◽  
Shear Velocity ◽  
Velocity Variation ◽  
The South ◽  
Study Region ◽  
Lithospheric Thickness ◽  
Phase Velocities ◽  
The North ◽  
Southern Norway

SUMMARY We use the recently deployed ScanArray network of broad-band stations covering most of Norway and Sweden as well as parts of Finland to analyse the propagation of Rayleigh waves in Scandinavia. Applying an array beamforming technique to teleseismic records from ScanArray and permanent stations in the study region, in total 159 stations with a typical station distance of about 70 km, we obtain phase velocities for three subregions, which collectively cover most of Scandinavia (excluding southern Norway). The average phase dispersion curves are similar for all three subregions. They resemble the dispersion previously observed for the South Baltic craton and are about 1 per cent slower than the North Baltic shield phase velocities for periods between 40 and 80 s. However, a remarkable sin(1θ) phase velocity variation with azimuth is observed for periods >35 s with a 5 per cent deviation between the maximum and minimum velocities, more than the overall lateral variation in average velocity. Such a variation, which is incompatible with seismic anisotropy, occurs in northern Scandinavia and southern Norway/Sweden but not in the central study area. The maximum and minimum velocities were measured for backazimuths of 120° and 300°, respectively. These directions are perpendicular to a step in the lithosphere–asthenosphere boundary (LAB) inferred by previous studies in southern Norway/Sweden, suggesting a relation to large lithospheric heterogeneity. In order to test this hypothesis, we carried out 2-D full-waveform modeling of Rayleigh wave propagation in synthetic models which incorporate a steep gradient in the LAB in combination with a pronounced reduction in the shear velocity below the LAB. This setup reproduces the observations qualitatively, and results in higher phase velocities for propagation in the direction of shallowing LAB, and lower ones for propagation in the direction of deepening LAB, probably due to the interference of forward scattered and reflected surface wave energy with the fundamental mode. Therefore, the reduction in lithospheric thickness towards southern Norway in the south, and towards the Atlantic ocean in the north provide a plausible explanation for the observed azimuthal variations.

scholarly journals Flow velocity and nutrients affect CO2 emissions from agricultural drainage channels in the North China Plain

2020 ◽  
Vol 32 (1) ◽  
Author(s):  
Peifang Leng ◽  
Fadong Li ◽  
Kun Du ◽  
Zhao Li ◽  
Congke Gu ◽  
...  
Keyword(s):  
Flow Velocity ◽  
North China Plain ◽  
North China ◽  
Groundwater Depletion ◽  
Agricultural Drainage ◽  
Agricultural Practice ◽  
The North ◽  
The North China Plain ◽  
Groundwater Irrigation ◽  
Drainage Channels

Abstract Background Groundwater is typically over-saturated in CO2 with respect to atmospheric equilibrium. Irrigation with groundwater is a common agricultural practice in many countries, but little is known about the fate of dissolved inorganic carbon (DIC) in irrigation groundwater and its contribution to the CO2 emission inventory from land to the atmosphere. We performed a mesocosm experiment to study the fate of DIC entering agricultural drainage channels in the North China Plain. Specifically, we aimed to unravel the effect of flow velocity and nutrient on CO2 emissions. Results All treatments were emitting CO2. Approximately half of the DIC in the water was consumed by TOC production (1–16%), emitted to the atmosphere (14–20%), or precipitated as calcite (CaCO3) (14–20%). We found that DIC depletion was stimulated by nutrient addition, whereas more CO2 evasion occurred in the treatments without nutrients addition. On the other hand, about 50% of CO2 was emitted within the first 50 h under high flow velocity. Thus, in the short term, high nutrient levels may counteract CO2 emissions from drainage channels, whereas the final fate of the produced biomass (burial versus mineralization to CO2 or even CH4) determines the duration of the effect. Conclusion Our study reveals that both hydrology and biological processes affect CO2 emissions from groundwater irrigation channels. The estimated CO2 emission from total groundwater depletion in the North China Plain is up to 0.52 ± 0.07 Mt CO2 year−1. Thus, CO2 emissions from groundwater irrigation should be considered in regional CO2 budgets, especially given that groundwater depletion is expected to acceleration in the future.

scholarly journals Geological region by multi-signal method of gravity anomaly data in central Vietnam area

2021 ◽  
Vol 62 (5) ◽  
pp. 43-54
Author(s):  
Hong Thi Phan ◽  
Petrov Aleksey Vladimirovich ◽  
Phuong Minh Do ◽  
Luu Truong Nguyen ◽  
Keyword(s):  
Central Area ◽  
Tectonic Activity ◽  
Horizontal Gradient ◽  
Spectral Correlation ◽  
Sliding Windows ◽  
The North ◽  
Central Vietnam ◽  
Two Dimensional Filtering ◽  
Calculation Results ◽  
Signal Method

This paper presents the research results of applying the combined method of probabilistic statistical approaches, energy density spectral correlation, two-dimensional filtering in dynamic sliding windows, full horizontal gradient and heterogeneous axis tracking method to process and interpret the Bughe gravitational anomaly field in central area Vietnam. The calculation results have shown the superiority of the twodimensional filter in dynamic sliding windows compared to the filters in fixed windows in GEOSOFT software, GMT software. According to the physical characteristics of the field, the study area was divided into 13 homogeneous classes, this result is consistent with the geological-tectonic data in the area. In the north and northeast, the stabilized rock layers are characterized by homogeneous layers that extend in the northwestsoutheast direction. In the south and southwest, there is complex tectonic activity characterized by high density rock layers overlain by low density rock layers in each fault band with different directions of development. This suggests that there may be deeply buried mineral deposits of magmatic origin in central area Vietnam.

scholarly journals Spatial Management Measures Alter Vessel Behavior in the Aleutian Archipelago

2021 ◽  
Vol 7 ◽  
Author(s):  
Benjamin K. Sullender ◽  
Kelly Kapsar ◽  
Aaron Poe ◽  
Martin Robards
Keyword(s):  
North Pacific ◽  
Risk Mitigation ◽  
Spatial Scales ◽  
Great Circle ◽  
Ecological Impacts ◽  
Study Region ◽  
The North ◽  
Management Measures ◽  
Before And After ◽  
The North Pacific

The Aleutian Archipelago and surrounding waters have enormous ecological, cultural, and commercial significance. As one of the shortest routes between North American and Asian ports, the North Pacific Great Circle Route, which crosses through the Aleutian Archipelago, is traveled by thousands of large cargo ships and tanker vessels every year. To reduce maritime risks and enhance navigational safety, the International Maritime Organization built upon earlier offshore routing efforts by designating five Areas To Be Avoided (ATBAs) in the Aleutian Islands in 2016. The ATBAs are designed to keep large vessels at least 50 nautical miles (93 km) from shore unless calling at a local port or transiting an authorized pass between islands. However, very few studies have examined the effectiveness of ATBAs as a mechanism for changing vessel behavior and thereby reducing the ecological impacts of maritime commerce. In this study, we use 4 years of satellite-based vessel tracking data to assess the effectiveness of the Aleutian ATBAs since their implementation in 2016. We determined whether vessels transiting the North Pacific Great Circle Route changed behavior after ATBA implementation, both in terms of overall route selection and in terms of compliance with each ATBA boundary. We found a total of 2,252 unique tankers and cargo vessels >400 gross tons transited the study region, completing a total of 8,794 voyages. To quantify routing changes of individual vessels, we analyzed the 767 vessels that transited the study region both before and after implementation. The percentage of voyages transiting through the boundaries of what would become ATBAs decreased from 76.3% in 2014–2015 (prior to ATBA designation) to 11.8% in 2016–2017 (after implementation). All five Aleutian ATBAs had significant increases in compliance, with the West ATBA showing the most dramatic increase, from 32.1% to 95.0%. We discuss the framework for ATBA enforcement and highlight the value of local institutional capacity for real-time monitoring. Overall, our results indicate that ATBAs represent a viable strategy for risk mitigation in sensitive ecological areas and that through monitoring, spatial protections influence vessel route decisions on multiple spatial scales.

scholarly journals Geochemical trends in central and western North Greenland

1987 ◽  
Vol 133 ◽  
pp. 123-132
Author(s):  
A Steenfelt
Keyword(s):  
Cross Sections ◽  
Sedimentary Environment ◽  
Distribution Patterns ◽  
Major Elements ◽  
Tectonic Activity ◽  
Chemical Analyses ◽  
The North ◽  
Platform Margin ◽  
Vein Type ◽  
North Greenland

Geochemical maps and geochemical cross-sections, based on chemical analyses of the < 0.1 mm fraction of stream sediment samples collected at a density of approximately 1 sample per 30 km2 in central and western North Greenland, show that the distribution patterns for the major elements and some trace elements reflect the main lithological units of the North Greenland Palaeozoic platform and trough. By contrast the distribution patterns for S and Sr are different. High S values are correlated with zones of tectonic activity and are thought to indicate migration of H2S along faults. High Sr values are correlated with evaporitic rocks in the platform sequence and with deep sea carbonates. High BaO values occurring along the Silurian platform margin and in the Ordovician platform-slope sequence are the result of Ba enrichment in the sedimentary environment, combined with epigenetic vein-type baryte mineralisation.

scholarly journals Seasonal trends and phenology shifts in sea surface temperature on the North American northeastern continental shelf

Elem Sci Anth ◽  
2017 ◽  
Vol 5 ◽  
Author(s):  
Andrew C. Thomas ◽  
Andrew J. Pershing ◽  
Kevin D. Friedland ◽  
Janet A. Nye ◽  
Katherine E. Mills ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Continental Shelf ◽  
Sea Surface Temperature ◽  
North American ◽  
Gulf Of Maine ◽  
Sea Surface ◽  
Scotian Shelf ◽  
Seasonal Differences ◽  
Study Region ◽  
The North

The northeastern North American continental shelf from Cape Hatteras to the Scotian Shelf is a region of globally extreme positive trends in sea surface temperature (SST). Here, a 33-year (1982–2014) time series of daily satellite SST data was used to quantify and map spatial patterns in SST trends and phenology over this shelf. Strongest trends are over the Scotian Shelf (&gt;0.6°C decade–1) and Gulf of Maine (&gt;0.4°C decade–1) with weaker trends over the inner Mid-Atlantic Bight (~0.3°C decade–1). Winter (January–April) trends are relatively weak, and even negative in some areas; early summer (May–June) trends are positive everywhere, and later summer (July–September) trends are strongest (~1.0°C decade–1). These seasonal differences shift the phenology of many metrics of the SST cycle. The yearday on which specific temperature thresholds (8° and 12°C) are reached in spring trends earlier, most strongly over the Scotian Shelf and Gulf of Maine (~ –0.5 days year–1). Three metrics defining the warmest summer period show significant trends towards earlier summer starts, later summer ends and longer summer duration over the entire study region. Trends in start and end dates are strongest (~1 day year–1) over the Gulf of Maine and Scotian Shelf. Trends in increased summer duration are &gt;2.0 days year–1 in parts of the Gulf of Maine. Regression analyses show that phenology trends have regionally varying links to the North Atlantic Oscillation, to local spring and summer atmospheric pressure and air temperature and to Gulf Stream position. For effective monitoring and management of dynamically heterogeneous shelf regions, the results highlight the need to quantify spatial and seasonal differences in SST trends as well as trends in SST phenology, each of which likely has implications for the ecological functioning of the shelf.

scholarly journals The geology of the north-eastern corner of Greenland - photogeological studies and 1993 field work

1994 ◽  
Vol 161 ◽  
pp. 21-33
Author(s):  
H.F Jepsen ◽  
J.C Escher ◽  
J.D Friderichsen ◽  
A.K Higgins
Keyword(s):  
Field Work ◽  
Tectonic Activity ◽  
Mobile Belt ◽  
North East ◽  
The North ◽  
Upper Proterozoic ◽  
North Eastern ◽  
Field Season ◽  
Upper Boundary ◽  
Middle Proterozoic

Late Archaean and Early Proterozoic crust-forming events in North-East and eastern North Greenland were succeeded by Middle Proterozoic sedimentation and volcanic activity; Late Proterozoic through Tertiary sedimentation was interrupted by several periods of tectonic activity, including the Caledonian orogeny in East Greenland and the Mesozoic deformation of the Wandel Hav mobile belt. Photogeological studies helped pinpoint areas of special interest which were investigated during the short 1993 field season. Insights gained during field work include: the nature of the crystalline basement terrain in the Caledonian fold belt, redefinition of the upper boundary of the Upper Proterozoic Rivieradal sandstones, revision of Caledonian nappe terminology, and the northern extension of the Caledonian Storstrømmen shear zone.

Sign in / Sign up

Export Citation Format

Share Document