Crustal thickness under the Gulf of St. Lawrence, northern Appalachians, from gravity and deep seismic data

1989 ◽  
Vol 26 (8) ◽  
pp. 1517-1532 ◽  
Author(s):  
F. Marillier ◽  
J. Verhoef
Keyword(s):  
Seismic Data ◽  
Bouguer Anomaly ◽  
Crustal Thickness ◽  
Moho Depth ◽  
Crustal Layer ◽  
Reflection Seismic ◽  
Middle Paleozoic ◽  
Lateral Extent ◽  
Well Data ◽  
Lower Crustal

We have determined crustal thickness in the Gulf of St. Lawrence, an area that corresponds to an offset of the main northern Appalachians units. A "complete" Bouguer anomaly was calculated from recent depth-to-basement compilations and sediment densities from well data. The Moho surface was obtained by inverting the Bouguer anomaly, assuming a single density contrast at depth, and using an average depth provided by deep reflection seismic data. The resulting crustal model shows a Moho depth of 42–44 km beneath the Grenville Craton, north of the Appalachian deformation front. South of this front, the depth to Moho displays a pronounced thinning of the crust beneath the Carboniferous Magdalen Basin. This is in striking contrast to the deep seismic data, which give a Moho depth of about 43 km. The modelling of the Bouguer anomaly in the Magdalen Basin, taking into account the seismic reflection and refraction data, reconciles these different results and suggests that a 43 km deep Moho beneath the basin is associated with a lower crustal layer about 13 km thick, with high velocity (7.35 km/s) and density (3.05 g/cm3). The Bouguer anomaly suggests that the lateral extent of this high-density layer is confined roughly to the Magdalen Basin. We suggest that this layer is due to mantle underplating of the crust as a result of the Carboniferous-age formation of the Magdalen Basin, and that it is not a feature related to the early to middle Paleozoic development of the Appalachian Orogen.

A multidisciplinary study of the Palaeogene succession offshore southern West Greenland

2002 ◽  
pp. 90-96
Author(s):  
Finn Dalhoff ◽  
James A. Chalmers ◽  
Henrik Nøhr-Hansen ◽  
Jan A. Rasmussen ◽  
Emma Sheldon ◽  
...  
Keyword(s):  
Seismic Data ◽  
Seismic Stratigraphy ◽  
Depositional Sequences ◽  
Original Series ◽  
West Greenland ◽  
Dinoflagellate Cyst ◽  
Reflection Seismic ◽  
Multidisciplinary Study ◽  
New Interpretation ◽  
Well Data

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Dalhoff, F., Chalmers, J. A., Nøhr-Hansen, H., Rasmussen, J. A., Sheldon, E., & Gregersen, U. (2002). A multidisciplinary study of the Palaeogene succession offshore southern West Greenland. Geology of Greenland Survey Bulletin, 191, 90-96. https://doi.org/10.34194/ggub.v191.5134 _______________ A project with the aim of amalgamating an interpretation of reflection seismic data from offshore southern West Greenland with a new interpretation of well data was finalised at the Geological Survey of Denmark and Greenland (GEUS) in 2001 (Chalmers et al. 2001b). As part of this study, seismic and depositional sequences between major regional unconformities of Danian and mid-Eocene age were delineated and dated. New palaeoenvironmental and sedimentological interpretations using dinoflagellate cyst, microfossil and nannoplankton stratigraphies and palaeoenvironmental interpretations from the five exploration wells drilled offshore West Greenland in the 1970s have been combined with a revised interpretation of lithology and correlated with the aid of seismic stratigraphy. The Qulleq-1 well drilled in 2000 was relinquished late in the project period (Christiansen et al. 2002, this volume), and it has therefore only been possible to incorporate biostratigraphic information from this well into the project.

scholarly journals Time-Depth Curve Evaluation Method for Conversion Time to Depth at Penobscot Field, Nova-Scotia, Canada

2017 ◽  
Vol 17 (1) ◽  
pp. 25
Author(s):  
Fitri Rizqi Azizah ◽  
Puguh Hiskiawan ◽  
Sri Hartanto
Keyword(s):  
Time Domain ◽  
Seismic Data ◽  
Evaluation Method ◽  
Seismic Survey ◽  
Seismic Exploration ◽  
Reflection Seismic ◽  
Conversion Time ◽  
Well Data ◽  
The Time Domain ◽  
Depth Curve

Oil and natural gas as a fossil fuel that is essential for human civilization, and included in nonrenewable energy, making this energy source is not easy for updated availability. So that it is necessary for exploration and exploitation reliable implementation. Seismic exploration becomes the method most widely applied in the oil, in particular reflection seismic exploration. Data wells (depth domain) and seismic data (time domain) of reflection seismic survey provides information wellbore within the timescale. As for the good interpretation needed information about the state of the earth and is able to accurately describe the actual situation (scale depth). Conversion time domain into the depth domain into things that need to be done in generating qualified exploration map. Method of time-depth curve to be the method most preferred by the geophysical interpreter, in addition to a fairly short turnaround times, also do not require a large budget. Through data information check-shot consisting of the well data and seismic data, which is then exchanged plotted, forming a curve time-depth curve, has been able to produce a map domain depth fairly reliable based on the validation value obtained in the range of 54 - 176m difference compared to the time domain maps previously generated.Keywords: Energy nonrenewable, survei seismik, peta domain waktu, peta domain kedalaman, time-depth curve

scholarly journals Bulk Crustal Properties and Layered Velocity Structure in Fujian, SE China: Constraints From P and S Receiver Functions

2021 ◽  
Vol 9 ◽  
Author(s):  
Ayush Goyal ◽  
Shu-Huei Hung
Keyword(s):  
Velocity Structure ◽  
Crustal Thickness ◽  
Receiver Functions ◽  
Nonlinear Inversion ◽  
Low Velocity ◽  
Metamorphic Belt ◽  
Crustal Layer ◽  
Late Mesozoic ◽  
Geological Features ◽  
Lower Crustal

Multiple tectonic events since the Neoproterozoic era have framed the present-day lithosphere in the Fujian province affiliated with the eastern part of the South China Block. Comprehensive information of the crustal structure and bulk properties can aid to understand the geological features and tectonic processes of still much debate in this region. An attempt is made in this study to explore crustal thickness and internal velocities across Fujian using the teleseismic receiver functions (RFs). The H-V stacking of joint P and S RFs improves to simultaneously estimate crustal thickness, average Vp and Vs, and derived Vp/Vs ratio and bulk sound speed in three backazimuth sectors for each of 17 stations. Furthermore, a Neighborhood Algorithm nonlinear inversion of P RFs is employed to determine the layered structures of Vs and Vp/Vs beneath all the stations. Results indicate the crustal thickness varies from at most ∼35 km in northwest Fujian to 30–35 km in the inland mountains and 27–30 km in the southeastern coasts. The inferred Moho geometry is nonplanar or inclined across the Zhenghe-Dapu (ZD) and Changle-Zhaoan (CZ) fault zones, especially in the southern ZD fault area. The average Vp/Vs suggests that the crust is predominantly felsic in the Wuyi-Yunkai orogen and intermediate-to-mafic in the Cretaceous magmatic and metamorphic zones. A high-velocity upper crust along the coastline is revealed, which attributes to the Pingtan-Dongshan metamorphic belt. At the sites near the ZD fault zone, the intracrustal negative discontinuity occurs at a shallower depth of ∼15 km marking an abrupt Vs decrease into the low-velocity mid-to-lower crustal layer, probably linked to the closed paleo-rift basin remnants. The lower crust across the Fujian is generally characterized by relatively lower Vs and higher Vp/Vs (1.80–1.84) consistent with those of the mafic-ultramafic rocks, which do not support the proposed extensive magmatic underplating in the Late Mesozoic.

scholarly journals Crustal thickness and velocity structure across the Moroccan Atlas from long offset wide-angle reflection seismic data: The SIMA experiment

2014 ◽  
Vol 15 (5) ◽  
pp. 1698-1717 ◽  
Author(s):  
P. Ayarza ◽  
R. Carbonell ◽  
A. Teixell ◽  
I. Palomeras ◽  
D. Martí ◽  
...  
Keyword(s):  
Seismic Data ◽  
Velocity Structure ◽  
Crustal Thickness ◽  
Wide Angle ◽  
Reflection Seismic ◽  
Long Offset

Porosity from seismic data: A geostatistical approach

Geophysics ◽  
1988 ◽  
Vol 53 (10) ◽  
pp. 1263-1275 ◽  
Author(s):  
Philippe M. Doyen
Keyword(s):  
Seismic Data ◽  
Mean Square ◽  
Least Squares Regression ◽  
Reservoir Properties ◽  
Reflection Seismic ◽  
Geostatistical Approach ◽  
Independent Observations ◽  
Local Correlations ◽  
Mapping Techniques ◽  
Well Data

Using a geostatistical technique called cokriging, the areal distribution of porosity is estimated first in a numerically simulated reservoir model, then in an oil‐bearing channel‐sand of Alberta, Canada. The cokriging method consistently integrates 3-D reflection seismic data with well measurements of the porosity and provides error‐qualified, linear mean square estimates of this parameter. In contrast to traditional seismically assisted porosity mapping techniques that treat the data as spatially independent observations, the geostatistical approach uses spatial autocorrelation and crosscorrelation functions to model the lateral variations of the reservoir properties. In the simulated model, the experimental root‐mean square porosity error with cokriging is 50 percent smaller than the error in predictions relying on a least‐squares regression of porosity on seismically derived transit time in the reservoir interval. In the Alberta reservoir, a cross‐validation study at the wells demonstrates that the cokriging procedure is 20 percent more accurate, in a mean square sense, than a standard regression method, which accounts only for local correlations between porosity and seismically derived impedances. In both cases, cokriging capitalizes on areally dense seismic measurements that are indirectly related to porosity. As a result, when compared to estimates obtained by interpolating the well data, this technique considerably improves the spatial description of porosity in areas of sparse well control.

Cross-profile seismic data acquisition, imaging, and modeling of iron-oxide deposits: A case study from Blötberget, south-central Sweden

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. B233-B247
Author(s):  
Georgiana Maries ◽  
Alireza Malehmir ◽  
Paul Marsden
Keyword(s):  
Iron Oxide ◽  
Seismic Data ◽  
Large Scale ◽  
Seismic Profiles ◽  
Data Set ◽  
Reflection Seismic ◽  
South Central ◽  
3D Data ◽  
Lateral Extent ◽  
3D Processing

Two 2D reflection seismic profiles were acquired in Blötberget, south-central Sweden, for deep targeting and delineation of sheet-like iron-oxide deposits, known to dip toward the southeast and extend down to at least 0.8 km depth from core drilling observations. The two perpendicular profiles recorded shots at every receiver station along the main and cross profiles. To obtain more information on the lateral extent of the mineralized horizons, data from the two profiles, including the cross-profile records, were binned together in a 3D grid and further processed as a 3D data set. Processing results suggest that more information is retrieved when 3D processing is used and the mineralization lateral extent can be inferred for at least 0.3 km. The seismic response of the mineralization was further studied through forward reflection traveltime modeling, using a 3D ray-tracing approach; thus, the 3D geometry of several planar reflectors was validated. Additionally, 2D elastic finite-difference modeling work showed that the observed reflection pattern in the seismic data may originate from several mineralized horizons, suggesting potential resources in the footwall of the known deposits and large-scale geologic structures. The results encourage the use of seismic methods for direct delineation of mineral deposits even from 2D profiles and prompted a 3D survey in the area.

scholarly journals Crustal structure of the Volgo-Uralian subcraton revealed by inverse and forward gravity modeling

2021 ◽  
Author(s):  
Igor Ognev ◽  
Jörg Ebbing ◽  
Peter Haas
Keyword(s):  
Crustal Structure ◽  
Seismic Data ◽  
Lower Crust ◽  
Crustal Thickness ◽  
Moho Depth ◽  
Gravity Modeling ◽  
Gravity Inversion ◽  
Ural Mountains ◽  
Satellite Gravity ◽  
Crustal Model

Abstract. Volgo-Uralia is a Neoarchean easternmost part of the East European craton. Recent seismic studies of the Volgo-Uralian region provided new insights into the crustal structure of this area. In this study, we combine satellite gravity and seismic data in a common workflow to perform a complex study of Volgo-Uralian crustal structure which is useful for further basin analysis of the area. In this light, a new crustal model of the Volgo-Uralian subcraton is presented from a step-wise approach: (1) inverse gravity modeling followed by (2) 3D forward gravity modeling. First, inversion of satellite gravity gradient data was applied to determine the Moho depth for the area. Density contrasts between crust and mantle were varied laterally according to the tectonic units present in the region, and the model is constrained by the available active seismic data. The Moho discontinuity obtained from the gravity inversion was consequently modified and complemented in order to define a complete 3D crustal model by adding information on the sedimentary cover, upper crust, lower crust, and lithospheric mantle layers in the process of forward gravity modeling where both seismic and gravity constraints were respected. The obtained model shows crustal thickness variations from 32 to more than 55 km in certain areas. The thinnest crust with a thickness below 40 km is found beneath the Pericaspian basin, which is covered by a thick sedimentary layer. The thickest crust is located underneath the Ural Mountains as well as in the center of the Volga-Uralian subcraton. In both areas the crustal thickness exceeds 50 km. At the same time, initial forward gravity modeling has shown a gravity misfit of ca. 95 mGal between the measured Bouguer gravity anomaly and the forward calculated gravity field in the central area of the Volga-Uralian subcraton. This misfit was interpreted and modeled as a high-density lower crust which possibly represents underplated material. Our preferred crustal model of the Volga-Uralian subcraton respects the gravity and seismic constraints and reflects the main geological features of the region with Moho thickening in the cratons and under the Ural Mountains and thinning along the Paleoproterozoic rifts, Pericaspian sedimentary basin, and Pre-Urals foredeep.

scholarly journals Deep electrical resistivity tomography for the prospection of low- to medium-enthalpy geothermal resources

2019 ◽  
Vol 219 (3) ◽  
pp. 2056-2072
Author(s):  
A Carrier ◽  
F Fischanger ◽  
J Gance ◽  
G Cocchiararo ◽  
G Morelli ◽  
...  
Keyword(s):  
Electrical Potential ◽  
Bouguer Anomaly ◽  
Industrial Area ◽  
Gravity Models ◽  
Efficient Technology ◽  
Geothermal Resources ◽  
Reflection Seismic ◽  
Resistivity Model ◽  
Noise Data ◽  
Geoelectrical Methods

SUMMARY The growth of the geothermal industry sector requires innovative methods to reduce exploration costs whilst minimizing uncertainty during subsurface exploration. Until now geoelectrical prospection had to trade between logistically complex cabled technologies reaching a few hundreds meters deep versus shallow-reaching prospecting methods commonly used in hydro-geophysical studies. We present a recent technology for geoelectrical prospection, and show how geoelectrical methods may allow the investigation of medium-enthalpy geothermal resources until about 1 km depth. The use of the new acquisition system, which is made of a distributed set of independent electrical potential recorders, enabled us to tackle logistics and noise data issues typical of urbanized areas. We acquired a 4.5-km-long 2-D geoelectrical survey in an industrial area to investigate the subsurface structure of a sedimentary sequence that was the target of a ∼700 m geothermal exploration well (Geo-01, Satigny) in the Greater Geneva Basin, Western Switzerland. To show the reliability of this new method we compared the acquired resistivity data against reflection seismic and gravimetric data and well logs. The processed resistivity model is consistent with the interpretation of the active-seismic data and density variations computed from the inversion of the residual Bouguer anomaly. The combination of the resistivity and gravity models suggest the presence of a low resistivity and low density body crossing Mesozoic geological units up to Palaeogene–Neogene units that can be used for medium-enthalpy geothermal exploitation. Our work points out how new geoelectrical methods may be used to identify thermal groundwater at depth. This new cost-efficient technology may become an effective and reliable exploration method for the imaging of shallow geothermal resources.

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