The Congo Basin: Stratigraphy and subsurface structure defined by regional seismic reflection, refraction and well data

2020 ◽  
pp. 103407
Author(s):  
Damien Delvaux ◽  
Francesca Maddaloni ◽  
Magdala Tesauro ◽  
Carla Braitenberg
Keyword(s):  
Seismic Reflection ◽  
Congo Basin ◽  
Subsurface Structure ◽  
Well Data

Unconformities on the Scotian Shelf

1974 ◽  
Vol 11 (1) ◽  
pp. 89-100 ◽  
Author(s):  
Lewis H. King ◽  
Brian MacLean ◽  
Gordon B. Fader
Keyword(s):  
High Resolution ◽  
Seismic Reflection ◽  
Upper Cretaceous ◽  
Scotian Shelf ◽  
Early Tertiary ◽  
Late Tertiary ◽  
Glacial Processes ◽  
Well Data ◽  
Seismic Reflection Profiles ◽  
Cut And Fill

Four erosional unconformities have been recognized within the Mesozoic-Cenozoic succession on the Scotian Shelf, on the basis of data from high resolution seismic reflection profiles. Older unconformities are known from well data and others may be revealed by detailed biostratigraphic studies.The oldest of the four unconformities discussed in this paper is of Early Cretaceous age and appears to mark, with discordance, the boundary between Jurassic and Cretaceous strata on the western part of the shelf. A second angular unconformity, of Late Cretaceous age, has been recognized on the central part of the shelf where the basal part of the Banquereau Formation (Tertiary and uppermost Cretaceous) oversteps the zero-edge of the Wyandot Formation (Upper Cretaceous) and lies upon truncated beds of the Dawson Canyon Formation (Upper Cretaceous). Cut-and-fill relationships characterize a third unconformity developed during Early Tertiary time. A fourth unconformity was developed in Late Tertiary – Pleistocene time by fluvial processes and later by glacial processes. Although in many areas the latest unconformity appears to be the most conspicuous one on the shelf, its configuration closely follows the geomorphic expression developed during the previous period of erosion. The regional extent of the Cretaceous unconformities is not known, and they might only occur near basin margins and on structural and basement highs.

scholarly journals Seismically detected porous Zechstein carbonates in Southern Jutland, Denmark

1995 ◽  
Vol 42 ◽  
pp. 34-46
Author(s):  
Kim Gunn Maver
Keyword(s):  
Seismic Data ◽  
Acoustic Impedance ◽  
Seismic Reflection ◽  
Synthetic Seismograms ◽  
Lateral Distribution ◽  
Seismic Modelling ◽  
Seismic Sections ◽  
Well Data ◽  
Impedance Models

Zechstein carbonates in Southern Jutland, Denmark, have been explored by 10 wells since 1952, and a total of more than 2000 km of 2D seismic data has been acquired by various contractors. Seismic modelling, based on all the well data, is used as an aid to predict the lateral distribution of porous Zechstein carbonate intervals from the seismic data. ID seismic modelling is used to define the maximum number of intervals detected by the seismic sections at well locations. The ID seismic modelling results are also used to derive 2D acoustic impedance models and corresponding synthetic seismograms. The seismic modelling results illustrate a number of diagnostic reflection patterns associated with the porous carbonate intervals. The predicted distribution of porous carbonate intervals is, however, found to be uncertain, as thickness and porosity variations of each interval cannot be distinguished. Furthermore, thin porous carbonate intervals are not detected by the seismic sections, and the seismic reflection patterns indicating the presence of porous carbonate intervals can be associated with other lithologies. Porous Ca-la, Ca-lb, Ca-2 and Ca-3 carbonate intervals are found to be detected by the seismic sections only in the Zechstein platform area, and only the porous Ca-2 carbonate interval can be mapped

scholarly journals Subsurface structure of Northwest in the source region of the 2003 Miyagiken-Hokubu Earthquake by the Seismic Reflection Survey

2010 ◽  
Vol 61 (7-8) ◽  
pp. 289-299
Author(s):  
Shinobu Ito ◽  
Kazuo Yamaguchi ◽  
Takanobu Yokokura ◽  
Naomi Kano ◽  
Toshiki Ohtaki ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Source Region ◽  
Subsurface Structure

TECTONIC CONTROLS ON SEDIMENTATION AND MATURATION IN THE OFFSHORE NORTH PERTH BASIN

1989 ◽  
Vol 29 (1) ◽  
pp. 450 ◽  
Author(s):  
John F. Marshall ◽  
Chao- Shing Lee ◽  
Douglas C. Ramsay ◽  
Aidan M.G. Moore
Keyword(s):  
Seismic Reflection ◽  
Source Rocks ◽  
Hydrocarbon Generation ◽  
Late Permian ◽  
Early Permian ◽  
The West ◽  
Australian Continent ◽  
Multichannel Seismic Reflection ◽  
Well Data ◽  
Coal Measures

The major tectonic and stratigraphic elements of the offshore North Perth Basin have been delineated from regional BMR multichannel seismic reflection lines, together with industry seismic and well data. This analysis reveals that three sub- basins, the Edel, Abrolhos and Houtman Sub- basins, have formed as a result of three distinct episodes of rifting within the offshore North Perth Basin during the Early Permian, Late Permian and Late Jurassic respectively. During this period, rifting has propagated from east to west, and has culminated in the separation of this part of the Australian continent from Greater India.The boundaries between the sub- basins and many structures within individual sub- basins are considered to have been produced by strike- slip or oblique- slip motion. The offshore North Perth Basin is believed to be a product of transtension, possibly since the earliest phase of rifting. This has culminated in separation and seafloor spreading by oblique extension along the Wallaby Fracture Zone to form a transform passive continental margin.This style of rifting and extension has produced relatively thin syn- rift sequences, some of which have been either partly or completely removed by erosion. While the source- rock potential of the syn- rift phase is limited, post- rift marine transgressional phases and coal measures do provide adequate and relatively widespread source rocks for hydrocarbon generation. Differences in the timing of rifting across the basin have resulted in a maturation pattern whereby mature sediments become younger to the west.

Tectonic evolution of the Congo Basin using geophysical data and 3D numerical simulations

2020 ◽  
Author(s):  
Francesca Maddaloni ◽  
Damien Delvaux ◽  
Magdala Tesauro ◽  
Taras Gerya ◽  
Carla Braitenberg
Keyword(s):  
Numerical Simulations ◽  
Gravity Model ◽  
Tectonic Evolution ◽  
Seismic Reflection ◽  
Congo Basin ◽  
Gravity Disturbance ◽  
Weak Zone ◽  
Gravity Field Model ◽  
Numerical Tests ◽  
Seismic Reflection Profiles

<p>The Congo basin (CB) is an intracratonic basin that occupies a large part of the Congo Craton (1.2 million km<sup>2</sup>) covering approximately 10% of the continent [1]. It contains up to 9 km of sedimentary rocks from the Mesoproterozoic until Cenozoic age. The formation of the CB started with a rifting phase during Mesoproterozoic with the amalgamation of the Rodinia supercontinent (1.2 Gyr). Afterwards, the main episodes of subsidence occurred during the subsequent Neoproterozoic post-rift phases, which were followed by phases of compression at the end of the Permian and during the Early Jurassic age and other sedimentation episodes during Upper Cretaceous and Cenozoic [2].</p><p> We reconstruct the stratigraphy and tectonic evolution of the basin by analyzing seismic reflection profiles. Furthermore, we estimated the velocity, density, and thickness of the sedimentary layers in order to calculate their gravity effect. Afterwards, we calculate the gravity disturbance and Bouguer anomalies using a combined satellite and terrestrial data gravity model. The gravity disturbance obtained from the EIGEN-6C4 gravity model [3] shows two types of anomalies. One with a long wavelength (~50 mGal) that covers the entire area of the Congo basin and a second one with a short wavelength (~130 mGal), having a NW-SE trend, which corresponds to the main depocenters of sediments detected by the interpretation of seismic reflection profiles. These results have been used as input parameters for 3D numerical simulations to test the main mechanisms of formation and evolution of the CB. For this aim, we used the thermomechanical I3ELVIS code [4] to simulate the initial rift phase. The numerical tests have been conducted considering a sub-circular weak zone in the central part of the cratonic lithosphere [2] and applying a velocity of 2.5 cm/yr in two orthogonal directions (NS and EW), to test the hypothesis of the formation of a multi extensional rift in a cratonic area. We repeated these numerical tests by increasing the size of the weak zone and varying its lithospheric thickness. The results of these first numerical experiments show the formation of a circular basin in the central part of the cratonic lithosphere, in response to extensional stress, inducing the uplift of the asthenosphere.</p><p>[1] Kadima, et al. (2011), Structure and geological history of the Congo Basin: an integrated interpretation of gravity, magnetic and reflection seismic data, doi:10.1111/j.1365-2117.2011.00500.x.<br>[2] De Wit, et al. (2008), Restoring Pan-African-Brasiliano connections: more Gondwana control, less Trans-Atlantic corruption, doi:10.1144/SP294.20<br>[3] Förste et al. (2014) EIGEN-6C4 The latest combined global gravity field model including GOCE data up to degree and order 2190 of GFZ Potsdam and GRGS Toulouse; doi: 10.5880/ICGEM.2015.1, 2014<br>[4] Gerya (2009), Introduction to numerical geodynamic modelling, Cambridge University Press</p>

Approximating subsurface structure in areas of severe subsea erosion—A nonprocessing technique

Geophysics ◽  
1989 ◽  
Vol 54 (11) ◽  
pp. 1397-1409
Author(s):  
Fred W. Lishman ◽  
Michael N. Christos
Keyword(s):  
Seismic Data ◽  
Seismic Reflection ◽  
Velocity Model ◽  
Subsurface Structure ◽  
Submarine Canyons ◽  
Arrival Times ◽  
Sea Floor ◽  
Static Corrections ◽  
Map Migration ◽  
Made In

Severe subsea erosion distorts seismic reflection times and velocity analyses and makes determining subsurface structure difficult. Although data reprocessing is the logical solution for removing these distortions, reprocessing can be expensive. We present a case history describing a nonprocessing depth‐conversion technique using a geologic erosional model. A grid of common‐midpoint seismic data located in and around several submarine canyons was used for this study. Establishing a geologic erosional model requires an accurate representation of the sea floor, which we obtain by map migration of the sea‐floor reflection. A velocity model was developed using only those analyses not adversely affected by sea‐floor erosion. To remove the effects of erosion from the arrival times of a mapped horizon, static corrections (velocity replacement and compaction) were developed. We replaced the water velocity in the eroded section with depth‐equivalent rock velocities from the velocity model. The compaction correction, which was derived empirically, is based on the assumption that porosity restoration occurred in the sediments beneath the canyons when erosion reduced the overlying pressure. Compaction correction in conjunction with velocity replacement produced structure maps (time and depth) that exhibit only minor effects of erosion. These results were further improved by applying dynamic corrections obtained by ray tracing a subsurface model to determine the traveltime through the water for the reflection from the mapped horizon. Our final structure maps demonstrate that a geologically reasonable structural interpretation in depth can be made in areas of severe subsea erosion without reprocessing the data.

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