Some Aspects of the Bedrock Geology of Hudson Bay As Interpreted From Continuous Seismic Reflection Profiles

1968 ◽  
Author(s):  
A C Grant
Keyword(s):  
Seismic Reflection ◽  
Hudson Bay ◽  
Bedrock Geology ◽  
Seismic Reflection Profiles

Phanerozoic vertical motions of Hudson Bay

2004 ◽  
Vol 41 (10) ◽  
pp. 1181-1200 ◽  
Author(s):  
Detlef Hanne ◽  
Nicky White ◽  
Andrew Butler ◽  
Stephen Jones
Keyword(s):  
Seismic Reflection ◽  
Hudson Bay ◽  
Data Sets ◽  
Reflection And Refraction ◽  
Crustal Thinning ◽  
Basin Subsidence ◽  
Starting Point ◽  
Intracratonic Basin ◽  
Seismic Reflection Profiles ◽  
Two Stages

We analyze the sedimentary record of the Hudson Bay basin, an intracratonic basin which is widely believed to have been formed by convective downwelling within the mantle. This belief largely stems from the coincidence of a long-wavelength negative gravity anomaly and an approximately circular basin which is filled with about 2 km of predominantly Paleozoic sedimentary rocks. Our starting point is a set of wells and seismic reflection profiles which demonstrate that the basin subsided rapidly from Ordovician to Devonian times. One- and two-dimensional subsidence modeling show that water-loaded subsidence occurred in two stages and is too rapid to be accounted for by thermal contraction alone. Instead, we suggest that basin subsidence is consistent with minor phases of lithospheric thinning which occurred during Ordovician–Silurian and Early–Middle Devonian times. Stretching factors for these minor extensional episodes vary from 1.05 to 1.2 with vertical strain rates of 2–10 Ga–1. Our interpretation of the subsidence record is corroborated by limited evidence for syn-rift normal faulting and crustal thinning inferred from legacy seismic reflection and refraction data sets. Subsidence modelling also suggests that about 1 km of expected thermal subsidence is missing. This discrepancy suggests that the basin was uplifted and denuded at least once, but possibly several times, between Late Devonian and Middle Cretaceous times (i.e., 360–100 Ma) and between Cretaceous and Quaternary times. We conclude that the Hudson Bay basin was not generated by convective downwelling that initiated in Paleozoic times and that remained coupled to the lithospheric plate.

scholarly journals Spatial Relationships between Pockmarks and Sub-Seabed Gas in Fjordic Settings: Evidence from Loch Linnhe, West Scotland

Geosciences ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 283
Author(s):  
Allan Audsley ◽  
Tom Bradwell ◽  
John Howe ◽  
John Baxter
Keyword(s):  
Water Column ◽  
Seismic Reflection ◽  
Hot Spot ◽  
Geophysical Data ◽  
Spatial Relationships ◽  
Hydrocarbon Gases ◽  
Offshore Industry ◽  
Seismic Reflection Profiles ◽  
Spot Analysis ◽  
Sedimentary Carbon

Sub-seabed gas is commonly associated with seabed depressions known as pockmarks—the main venting sites for hydrocarbon gases to enter the water column. Sub-seabed gas accumulations are characterized by acoustically turbid or opaque zones in seismic reflection profiles, taking the form of gas blankets, curtains or plumes. How the migration of sub-seabed gas relates to the origin and distribution of pockmarks in nearshore and fjordic settings is not well understood. Using marine geophysical data from Loch Linnhe, a Scottish fjord, we show that shallow sub-seabed gas occurs predominantly within glaciomarine facies either as widespread blankets in basins or as isolated pockets. We use geospatial ‘hot-spot’ analysis conducted in ArcGIS to identify clusters of pockmarks and acoustic (sub-seabed) profile interpretation to identify the depth to gas front across the fjord. By combining these analyses, we find that the gas below most pockmarks in Loch Linnhe is between 1.4 m and 20 m deep. We anticipate that this work will help to understand the fate and mobility of sedimentary carbon in fjordic (marine) settings and advise offshore industry on the potential hazards posed by pockmarked seafloor regions even in nearshore settings.

scholarly journals Inverted Basins by Africa–Eurasia Convergence at the Southern Back-Arc Tyrrhenian Basin

Geosciences ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 117
Author(s):  
Maria Filomena Loreto ◽  
Camilla Palmiotto ◽  
Filippo Muccini ◽  
Valentina Ferrante ◽  
Nevio Zitellini
Keyword(s):  
Seismic Reflection ◽  
Magnetic Data ◽  
Normal Faults ◽  
Sedimentary Sequence ◽  
Initiation Zone ◽  
Arc Setting ◽  
Seismic Reflection Profiles ◽  
Back Arc ◽  
Flower Structures ◽  
Tyrrhenian Basin

The southern part of Tyrrhenian back-arc basin (NW Sicily), formed due to the rifting and spreading processes in back-arc setting, is currently undergoing contractional tectonics. The analysis of seismic reflection profiles integrated with bathymetry, magnetic data and seismicity allowed us to map a widespread contractional tectonics structures, such as positive flower structures, anticlines and inverted normal faults, which deform the sedimentary sequence of the intra-slope basins. Two main tectonic phases have been recognised: (i) a Pliocene extensional phase, active during the opening of the Vavilov Basin, which was responsible for the formation of elongated basins bounded by faulted continental blocks and controlled by the tear of subducting lithosphere; (ii) a contractional phase related to the Africa-Eurasia convergence coeval with the opening of the Marsili Basin during the Quaternary time. The lithospheric tear occurred along the Drepano paleo-STEP (Subduction-Transform-Edge-Propagator) fault, where the upwelling of mantle, intruding the continental crust, formed a ridge. Since Pliocene, most of the contractional deformation has been focused along this ridge, becoming a good candidate for a future subduction initiation zone.

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