scholarly journals Stratigraphic and structural framework of the Neoproterozoic Paracuellos Group, Iberian Chains, NE Spain

2002 ◽  
Vol 173 (3) ◽  
pp. 219-227 ◽  
Author(s):  
J. Javier Álvaro ◽  
Marie-Madeleine Blanc-Valleron
Keyword(s):  
Seismic Reflection ◽  
Structural Complexity ◽  
Gradual Transition ◽  
Seismic Profiles ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Sedimentary Evolution ◽  
Structural Framework ◽  
Bedded Chert ◽  
Seismic Reflection Profiles

Abstract The Neoproterozoic Paracuellos Group of the Iberian Chains constitutes the core of two disconnected faulted blocks, named the Paracuellos and Codos antiforms. Precise lithostratigraphic correlations between both areas are not possible due to the structural complexity and because marker beds do not persist laterally. This paper presents a crustal cross-section of the Neoproterozoic axial core (the Paracuellos antiform) based on surface geology, boreholes and seismic reflection profiles. Seismic reflection data reveal that the basement was directly involved by a major Hercynian structure, named here the Paracuellos fault, which splits longitudinally the Paracuellos axial core. In seismic profiles this fault occurs as a northeasterly-dipping reflector (60–70° steep), evidencing a bivergent geometry of the lateral crustal elements. The sedimentary evolution of the Neoproterozoic Iberian platform ranges from transgressive, non-cyclic, offshore to hemipelagic, black and green shales (Sestrica Formation) to progradational trends recording shoaling during episodes of rapid sediment influx (Saviñán Formation), presumably in response to a low standing sea-level. The siliciclastic succession is punctuated in the inner platform by deposition of phosphatic limestones (Codos Bed), representing a major shoaling event and demarcating a sharp regional change of sedimentation separating two similar siliciclastic tendencies. A diagenetically induced bedded chert (Frasno Bed) occurs in the outer platform, and is interpreted as being the product of at least two silicification episodes. Both the Codos and Frasno Beds are overlain by the Aluenda Formation, which exhibits nearshore to offshore features. An important sedimentary discontinuity appears across the Neoproterozoic-Cambrian transition. The Cambrian(?) Bámbola Formation is paraconformable with the Paracuellos Group displaying a gradual transition in inner platform areas, whereas an erosive unconformity occurs in outer areas. The horizon of the Neoproterozoic-Cambrian boundary is not identified in the Iberian Chains, where neither Cadomian deformation nor discordances are recognisable.

Integrating high‐resolution refraction data into near‐surface seismic reflection data processing and interpretation

Geophysics ◽  
1998 ◽  
Vol 63 (4) ◽  
pp. 1339-1347 ◽  
Author(s):  
Kate C. Miller ◽  
Steven H. Harder ◽  
Donald C. Adams ◽  
Terry O’Donnell
Keyword(s):  
Seismic Reflection ◽  
Velocity Model ◽  
Surface Velocity ◽  
Seismic Profiles ◽  
Seismic Reflection Data ◽  
Near Surface ◽  
Interval Velocity ◽  
Velocity Models ◽  
Reflection Data ◽  
Seismic Reflection Profiles

Shallow seismic reflection surveys commonly suffer from poor data quality in the upper 100 to 150 ms of the stacked seismic record because of shot‐associated noise, surface waves, and direct arrivals that obscure the reflected energy. Nevertheless, insight into lateral changes in shallow structure and stratigraphy can still be obtained from these data by using first‐arrival picks in a refraction analysis to derive a near‐surface velocity model. We have used turning‐ray tomography to model near‐surface velocities from seismic reflection profiles recorded in the Hueco Bolson of West Texas and southern New Mexico. The results of this analysis are interval‐velocity models for the upper 150 to 300 m of the seismic profiles which delineate geologic features that were not interpretable from the stacked records alone. In addition, the interval‐velocity models lead to improved time‐to‐depth conversion; when converted to stacking velocities, they may provide a better estimate of stacking velocities at early traveltimes than other methods.

Crustal structure and surface zonation of the Canadian Appalachians: implications of deep seismic reflection data

1989 ◽  
Vol 26 (2) ◽  
pp. 305-321 ◽  
Author(s):  
François Marillier ◽  
Charlotte E. Keen ◽  
Glen S. Stockmal ◽  
Garry Quinlan ◽  
Harold Williams ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Three Dimensional ◽  
Surface Expression ◽  
Seismic Profiles ◽  
Crust And Upper Mantle ◽  
Seismic Reflection Data ◽  
Central Block ◽  
Reflection Data ◽  
Lower Crustal ◽  
Canadian Appalachians

In 1986, 1181 km of marine seismic reflection data was collected to 18–20 s of two-way traveltime in the Gulf of St. Lawrence area. The seismic profiles sample all major surface tectono-stratigraphic zones of the Canadian Appalachians. They complement the 1984 deep reflection survey northeast of Newfoundland. Together, the seismic profiles reveal the regional three-dimensional geometry of the orogen.Three lower crustal blocks are distinguished on the seismic data. They are referred to as the Grenville, Central, and Avalon blocks, from west to east. The Grenville block is wedge shaped in section, and its subsurface edge follows the form of the Appalachian structural front. The Grenville block abuts the Central block at mid-crustal to mantle depths. The Avalon block meets the Central block at a steep junction that penetrates the entire crust.Consistent differences in the seismic character of the Moho help identify boundaries of the deep crustal blocks. The Moho signature varies from uniform over extended distances to irregular with abrupt depth changes. In places the Moho is offset by steep reflections that cut the lower crust and upper mantle. In other places, the change in Moho elevation is gradual, with lower crustal reflections following its form. In all three blocks the crust is generally highly reflective, with no distinction between a transparent upper crust and reflective lower crust.In general, Carboniferous and Mesozoic basins crossed by the seismic profiles overlie thinner crust. However, a deep Moho is found at some places beneath the Carboniferous Magdalen Basin.The Grenville block belongs to the Grenville Craton; the Humber Zone is thrust over its dipping southwestern edge. The Dunnage Zone is allochthonous above the opposing Grenville and Central blocks. The Gander Zone may be the surface expression of the Central block or may be allochthonous itself. There is a spatial analogy between the Avalon block and the Avalon Zone. Our profile across the Meguma Zone is too short to seismically distinguish this zone from the Avalon Zone.

Seismic reflection, borehole and outcrop geometry of Late Wisconsin tills at a proposed landfill near Toronto, Ontario

1995 ◽  
Vol 32 (9) ◽  
pp. 1331-1349 ◽  
Author(s):  
Joseph I. Boyce ◽  
Nicholas Eyles ◽  
André Pugin
Keyword(s):  
Seismic Reflection ◽  
Seismic Reflection Data ◽  
Geophysical Logging ◽  
Greater Toronto Area ◽  
Reflection Data ◽  
Shallow Seismic ◽  
Surface Contaminants ◽  
Sand And Gravel ◽  
Seismic Reflection Profiles ◽  
High Degree

The search for new landfill sites in the Greater Toronto area of southern Ontario, Canada, is producing a wealth of data regarding the subsurface stratigraphy and geometry of Late Wisconsin (<25 ka) till deposits. Till strata are favoured as landfill substrates because of their wide surface extent, thickness (maximum ~60 m), high degree of overconsolidation, apparently massive character, and low permeability. However, problems are emerging where surface contaminants have migrated through till deposits into underlying aquifers along poorly understood transport paths. This paper reports the results of a detailed shallow seismic reflection investigation of a proposed 275 ha landfill site 40 km northeast of Toronto near Whitevale, where previous hydrochemical analysis and hydrogeological monitoring identified rapid vertical recharge of contaminated surface waters through Late Wisconsin tills up to 60 m thick. Seismic reflection data are ground truthed by drilling (36 holes; total drilled 3157 m), coring (1600 m), downhole geophysical logging, and outcrop data. The site stratigraphy at Whitevale consists of an uppermost Late Wisconsin till (Halton Till) separated from a lower till (informally named Northern till) by a silt, sand, and gravel complex. Seismic reflection profiles identify the presence of well-defined reflectors within the Northern till, which are correlated in outcrop with laterally extensive erosion surfaces overlain by sheet-like sands and gravels, up to 1 m thick, and boulder concentrations. Erosion surfaces and associated sediments record episodic scouring by subglacial meltwaters and provide potential "hydraulic windows" for the movement of surface contaminants through the till into underlying aquifers.

Ultrashallow seismic reflection monitoring of seasonal fluctuations in the water table

2000 ◽  
Vol 6 (3) ◽  
pp. 271-277 ◽  
Author(s):  
G. S. Baker ◽  
D. W. Steeples ◽  
C. Schmeissner ◽  
K. T. Spikes
Keyword(s):  
Water Table ◽  
Seismic Reflection ◽  
Test Site ◽  
Seasonal Fluctuations ◽  
Seismic Profiles ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Velocity Information ◽  
One Year

Abstract Ultrashallow seismic-reflection data were collected at a test site in Great Bend, Kansas. The purpose of the experiment was to image seasonal submeter-scale fluctuations in the water table over a period of one year to identify the factors important in monitoring the water table when using seismic-reflection techniques. The study indicates that detailed velocity information must be used when interpreting water-table levels. Using detailed velocity information as a control when depth-converting the seismic profiles yielded correct positioning of the water table within + or -12 cm at the test site.

scholarly journals Active deformation evidence in the offshore of western Calabria (southern Tyrrhenian Sea) from ultra-resolution multichannel seismic reflection data: results from the Gulf of Sant'Eufemia

2020 ◽  
Author(s):  
Fabrizio Pepe ◽  
Mor Kanari ◽  
Pierfrancesco Burrato ◽  
Marta Corradino ◽  
Henrique Duarte ◽  
...  
Keyword(s):  
Data Acquisition ◽  
Seismic Reflection ◽  
Fault System ◽  
Tyrrhenian Sea ◽  
Seismic Profiles ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Multichannel Seismic Reflection Data ◽  
Earthquake Potential

&lt;p&gt;An ultra-resolution, multichannel seismic reflection data set was collected during an oceanographic cruise organised in the frame of the &amp;#8220;&lt;em&gt;Earthquake Potential of Active Faults using offshore Geological and Morphological Indicators&lt;/em&gt;&amp;#8221; (EPAF) project, which was founded by the Scientific and Technological Cooperation (Scientific Track 2017) between the Italian Ministry of Foreign Affairs and International Cooperation and the Ministry of Science, Technology and Space of the State of Israel. The data acquisition approach was based on innovative technologies for the offshore imaging of stratigraphy and structures along continental margins with a horizontal and vertical resolution at decimetric scale. In this work, we present the methodology used for the 2D HR-seismic reflection data acquisition and the preliminary interpretation of the data set. The 2D seismic data were acquired onboard the R/V Atlante by using an innovative data acquisition equipment composed by a dual-sources Sparker system and one HR 48-channel, slant streamers, with group spacing variable from 1 to 2 meters, at 10 kHz sampling rate. An innovative navigation system was used to perform all necessary computations to determining real-time positions of sources and receivers. The resolution of the seismic profiles obtained from this experiment is remarkable high respect to previously acquired seismic data for both scientific and industrial purposes. In addition to the seismic imaging, gravity core data were also collected for sedimentological analysis and to give a chronological constraint using radiocarbon datings to the shallower reflectors. The investigated area is located in the western offshore sector of the Calabrian Arc (southern Tyrrhenian Sea) where previous research works, based on multichannel seismic profiles coupled with Chirp profiles, have documented the presence of an active fault system. One of the identified faults was tentatively considered as the source of the Mw 7, 8 September 1905 seismic event that hit with highest macroseismic intensities the western part of central Calabria, and was followed by a tsunami that inundated the coastline between Capo Vaticano and the Angitola plain. On this basis, the earthquake was considered to have a source at sea, but so far, the location, geometry and kinematics of the causative fault are still poorly understood. In this study we provide preliminary results of the most technologically advanced ultra-high-resolution geophysical method used to reveal the 3D faulting pattern, the late Quaternary slip rate and the earthquake potential of the marine fault system located close to the densely populated west coast of Calabria.&lt;/p&gt;

Shallow Deformation Along the Crittenden County Fault Zone Near the Southeastern Boundary of the Reelfoot Rift, Northeast Arkansas

1992 ◽  
Vol 63 (3) ◽  
pp. 263-275 ◽  
Author(s):  
E. A. Luzietti ◽  
L. R. Kanter ◽  
E. S. Schweig ◽  
K. M. Shedlock ◽  
R. B. VanArsdale
Keyword(s):  
Fault Zone ◽  
Seismic Reflection ◽  
Vertical Displacement ◽  
Surface Expression ◽  
Late Eocene ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Structural Relief ◽  
Well Data ◽  
Seismic Reflection Profiles

Abstract The Crittenden County fault zone (CCFZ) is located near the southeast boundary of the Reelfoot rift in northeastern Arkansas. The southeastern boundary of the rift has been characterized as an 8-km-wide zone of down-to-the-northwest displacement. The CCFZ, however, shows significant down-to-the-southeast reverse faulting of Paleozoic and Cretaceous rocks and flexure and thinning within the Tertiary sedimentary section. We discuss four of nine Mini-Sosie seismic reflection profiles, each 1 to 2 km long, acquired over the surface projection of the CCFZ and Reelfoot rift boundary. One second of two-way traveltime data was recorded, which corresponds to a maximum depth of approximately 1.2 km. Sedimentary layers between 50 and 800 m are well imaged; deeper strata are evident but not well imaged. Well data at one site on the CCFZ indicate approximately 63 and 82 m of vertical displacement of Cretaceous and Paleozoic rocks, respectively. Proprietary seismic-reflection data show reverse displacement of these rock units, indicating compressional tectonics. From the Mini-Sosie profiles, we estimate structural relief across the CCFZ at the Paleocene (Fort Pillow Sand) level to range between 14 and 70 m. The overlying middle-to-late Eocene section shows a similar or slightly smaller amount of thinning, indicating that much of the movement on the CCFZ dates mid-to-late Eocene. Displacement, flexure, and thinning in the geologic section increases as the CCFZ converges with the Reelfoot rift boundary, in the southwest part of the area studied. Surface expression of the CCFZ has not been identified. Reflections from the Quaternary-Eocene unconformity, however, show warping, dip, or interruptions in places over the CCFZ, suggesting that the CCFZ may have experienced Quaternary or Holocene movement as well.

Quaternary Transgressive/Regressive Cycles in the Gulf of Argos, Greece

1990 ◽  
Vol 34 (3) ◽  
pp. 317-329 ◽  
Author(s):  
Tjeerd H. van Andel ◽  
Eberhard Zangger ◽  
Constantine Perissoratis
Keyword(s):  
High Resolution ◽  
Sea Level ◽  
Seismic Reflection ◽  
Stratigraphic Sequence ◽  
Seismic Reflection Data ◽  
Marine Deposits ◽  
Reflection Data ◽  
Marine Seismic ◽  
Seismic Reflection Profiles ◽  
Mediterranean Soil

AbstractBorings in the Argive Plain reveal cycles of marine incursions, each ending with a Mediterranean soil profile and followed by a prograded fluvial and coastal wedge. The sediment prism of the Gulf of Argos shelf, visible in high-resolution seismic reflection profiles, also consists of transgressive and regressive depositional sequences identified by onlap, downlap, and truncation of deposits. At least four major reflectors, recognizable by their high acoustic impedance and erosional features, can be correlated across the shelf. The sediments between each pair of reflectors represent the seaward part of a set of transgressive and regressive marine deposits. They can be matched to the stratigraphic sequence on land where each marine unit is topped by a soil. Corrected for subsidence, the terminations of the onlapping and downlapping units define a local sea-level history; its time scale can be derived from a comparison with the eustatic sea-level history deduced from ocean cores. Thus, marine seismic reflection data can be used for the correlation of Quaternary oceanic and terrestrial chronologies.

Crustal geometry of the Abitibi Subprovince, in light of three-dimensional seismic reflector orientations

1998 ◽  
Vol 35 (5) ◽  
pp. 569-582 ◽  
Author(s):  
G Bellefleur ◽  
A J Calvert ◽  
M C Chouteau
Keyword(s):  
Seismic Reflection ◽  
Three Dimensional ◽  
Seismic Reflection Data ◽  
Volcanic Arc ◽  
The North ◽  
Reflection Data ◽  
Abitibi Subprovince ◽  
Seismic Reflection Profiles ◽  
Lower Crustal ◽  
Seismic Reflector

We provide precise estimates of reflector orientations beneath the Archean Abitibi Subprovince, using two distinct approaches based on Lithoprobe seismic reflection data. In the first, we use the dip of reflections observed on intersecting profiles to establish the three-dimensional orientation of reflective structures. In the second, the strikes and dips of reflectors are estimated in the crooked parts of seismic reflection profiles by calculating a measure of coherency along the traveltime trajectories defined by a particular azimuth, dip, depth, and medium velocity. Mid-crustal reflectors define two areas with distinctive geometry: reflectors beneath the southern Abitibi belt are oppositely dipping, and convergent at depth, providing a V-shape aspect to the greenstone rocks; other reflectors beneath the northern Abitibi belt are, in general, subparallel, dipping at an average of 30° toward the north. These north-dipping reflectors are partly disrupted by a low-reflectivity zone, which is attributed to rocks of the Opatica Subprovince, located underneath the northern Abitibi belt. Lower-crustal reflectors have a similar, shallowly north-dipping orientation throughout the Abitibi Subprovince. The geometry of the reflectors recovered is consistent with the different tectonic histories proposed for the southern and northern Abitibi assemblages, until common deformation during a north-south shortening event. Attitudes recovered in the northern Abitibi belt are consistent with tectonic scenarios involving underthrusting of Abitibi middle and lower crustal terranes beneath the Opatica belt, whereas the oppositely dipping reflectors recovered in the middle crust beneath the southern Abitibi belt could be representative of a rifted volcanic arc environment.

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