Geophysical studies on the eastern continental margin of Baffin Bay and in Lancaster Sound

1977 ◽  
Vol 14 (9) ◽  
pp. 1991-2001 ◽  
Author(s):  
H. R. Jackson ◽  
C. E. Keen ◽  
D. L. Barrett
Keyword(s):  
Structural Characteristics ◽  
Seismic Refraction ◽  
Continental Drift ◽  
Baffin Island ◽  
Seismic Reflection Data ◽  
Baffin Bay ◽  
Reflection Data ◽  
Basement High ◽  
Seismic Refraction Data ◽  
Sea Floor Spreading

The results of three crustal refraction lines on the western margin of Baffin Bay and one in Lancaster Sound are described. The refraction measurements in Baffin Bay along with earlier refraction, gravity, magnetic, and seismic reflection data are used to define the boundary between continental and oceanic crust. The results suggest that the transition from continental to oceanic material takes place in about 30 km. The seismic refraction data also suggest a sedimentary basin on the continental shelf with at least 6 km thickness of sediment which, however, thins rapidly near Baffin Island. This basin is truncated under the slope by either a basement high or carbonate rocks. Lancaster Sound is filled by about 10 km of sediments that could be either of Mesozoic or Paleozoic age based on comparisons with velocities in nearby wells. The sedimentary and structural characteristics of Lancaster Sound are discussed and related to the concepts of sea-floor spreading and continental drift.

Seismicity of the Baffin Bay region

1974 ◽  
Vol 64 (1) ◽  
pp. 87-98
Author(s):  
Anthony Qamar
Keyword(s):  
Upper Mantle ◽  
Baffin Island ◽  
Sea Floor ◽  
Baffin Bay ◽  
Hypocenter Determination ◽  
Joint Hypocenter Determination ◽  
Glacial Rebound ◽  
Sea Floor Spreading ◽  
Linear Trends ◽  
Northeast Coast

abstract Twenty-eight earthquakes in the Baffin Bay region have been relocated using the method of Joint Hypocenter Determination. The revised locations indicate two parallel, linear trends, one along the northeast coast of Baffin Island and the other in the western part of Baffin Bay. The seismicity does not appear to be controlled by glacial rebound but may be a remnant of sea-floor spreading which occurred 40 to 60 m.y. ago. Early P arrivals at near seismograph stations (Δ < 20°) can be explained by a high-velocity (8.5 km/sec) upper mantle in the Baffin region.

Structural Characteristics of some Sedimentary Basins in Northern Baffin Bay

1973 ◽  
Vol 10 (8) ◽  
pp. 1267-1278 ◽  
Author(s):  
C. E. Keen ◽  
D. L. Barrett
Keyword(s):  
Seismic Reflection ◽  
Magnetic Measurements ◽  
Structural Characteristics ◽  
Gravity Data ◽  
Seismic Refraction ◽  
Sedimentary Basins ◽  
Structural Features ◽  
Ocean Basin ◽  
Normal Faults ◽  
Baffin Bay

Geophysical measurements along tracks crossing some of the main structural features of the northern Baffin Bay shelf are described. The data consist of seismic reflection, seismic refraction, gravity, and magnetic measurements. Results in four areas—Lancaster Sound, Melville Bay, Smith Sound and Jones Sound—are presented. Magnetic and gravity data are used to define the extent of sedimentary basins in these areas. Seismic reflection measurements delineate the structural characteristics of the upper 2 km of the sedimentary strata and allow comparisons between them to be made. Seismic refraction measurements show that the upper 2 km of sediment exhibit low velocities—less than 3.2 km/s. Little deformation of the sediments is observed in any of these areas, however, the strata in Lancaster Sound and in the Melville Bay graben appear to have experienced less faulting than those in Jones Sound and Smith Sound. Normal faults are characteristic of the latter two areas. Jones Sound is a structurally complex area and is filled by a lesser thickness of sediments than is found in the other basins. These sediments are terminated near the entrance to the sound by Precambrian basement. A deeper sedimentary basin occupies Smith Sound and trends across the Nares Strait lineament. Although the data are insufficient to allow a detailed structural analysis of the strata in these regions, we speculate that the differences in sedimentary structures can be related to the formation of the Baffin Bay ocean basin.

QUEENSLAND PLATEAU AND CORAL SEA BASIN STRATIGRAPHY, STRUCTURE AND TECTONICS

1977 ◽  
Vol 17 (1) ◽  
pp. 13 ◽  
Author(s):  
Lloyd Taylor ◽  
David Falvey
Keyword(s):  
Seismic Refraction ◽  
Circulation Pattern ◽  
Late Eocene ◽  
Reflection And Refraction ◽  
Coral Sea ◽  
Australian Continent ◽  
Project Site ◽  
Seismic Refraction Data ◽  
Sea Floor Spreading ◽  
Refraction Data

Seafloor spreading in the Coral Sea Basin is dated by Deep Sea Drilling Project Site 287 as Early Eocene (51 my bp). This requires normal rifting and breakup of an extended Australian continent including the Queensland. Papuan and Louisiade Plateaus as well as the Cretaceous portions of East Papua. A reconstruction based on continental and plateau margin physiography and Papua-New Guinea geology points to a pole of relative opening at lat. 11.3° S., long. 141.3° E. This results in left-lateral transform motion along the Moresby Trough and Bismarck-Lagaip Fault Zones through breakup, plus the deformation of the Owen Stanley sediment pile, and emplacement of the Papuan Ultramafic Belt.Following initiation of sea-floor spreading, subsidence commenced at what are now the marginal plateaus bordering the Coral Sea Basin. A widespread unconformity spanning the late Eocene-mid Ollgocene can be recognised on all plateaus as well as in the basin proper. This is attributed to the commencement of a significant equatorial circulation pattern in the deepening basin and over the subsided plateaus. Stabilisation of this equatorial circulation pattern permitted coral reef development on residual basement highs on the marginal plateaus and eventually) on the subsiding Queensland continental shelf and Papuan stable platform areas in the late Oligocene-early Miocene.On the basis of seismic refraction and gravity evidence, rift valley sequences up to 3 km thick are inferred beneath the Queensland and Townsville Troughs and bordering the Queensland and Papuan Plateaus. Though seismic refraction data are lacking, similar sequences are also inferred beneath parts of the Eastern and Marion Plateaus. Bligh Trough and Louisiade Rise. The age of this pre-breakup rifting is suggested to be mid Cretaceous-Palaeocene although direct evidence is absent.Gravity modelling over the Queensland Trough, Plateau and Coral Sea Basin supports the interpretation from seismic reflection and refraction data. Continental crustal structure with a deep metamorphic layer is indicated for the Queensland Trough and Plateau with a depth to the Moho of 22-28 km. The continental/ocean crust transition occurs towards the base of the continental slope at a water depth of up to 4.5 km along the Queensland Plateau. Crust beneath the Coral Sea abyssal plain is oceanic with a depth to mantle of 11-13 km.

Attribute-assisted characterization of basement faulting and the associated sedimentary sequence deformation in north-central Oklahoma

2020 ◽  
Vol 8 (4) ◽  
pp. SP175-SP189
Author(s):  
Max Firkins ◽  
Folarin Kolawole ◽  
Kurt J. Marfurt ◽  
Brett M. Carpenter
Keyword(s):  
Structural Characteristics ◽  
Sedimentary Cover ◽  
Areal Density ◽  
Fault Reactivation ◽  
Vertical Separation ◽  
Seismogenic Fault ◽  
Seismic Reflection Data ◽  
North Central ◽  
Reflection Data ◽  
Arbuckle Group

Patterns of recent seismogenic fault reactivation in the granitic basement of north-central Oklahoma necessitate an understanding of the structural characteristics of the inherited basement-rooted faults. Here, we focus on the Nemaha Uplift & Fault Zone (NFZ) and the surrounding areas, within which we analyze the top-basement and intrabasement structures in eight poststack time-migrated 3D seismic reflection data sets. Overall, our results reveal 115 fault traces at the top of the Precambrian basement with sub-vertical dips, and dominant trends of west-northwest–east-southeast, northeast–southwest, and north–south. We observe that proximal to the NFZ, faults dominantly strike north–south, are fewer (<10), and have the lowest areal density and intensity, while displaying the largest maximum vertical separation. However, farther away (>30 km) from the NFZ, faults exhibit predominantly northeast–southwest trends, fault areal density and intensity increases, and maximum vertical separation decreases steadily. Of the analyzed faults, approximately 49% are confined to the basement (intrabasement), ~28% terminate within the Arbuckle Group, and approximately 23% transect units above the Arbuckle Group. These observations suggest that (1) proximal to the NFZ, deformation is dominantly accommodated along a few but longer fault segments, most of the mapped faults cut into the sedimentary rocks, and most of the through-going faults propagate farther up-section above the Arbuckle Group; and (2) with distance away from the NFZ, deformation is diffuse and distributed across relatively shorter fault segments, and most basement faults do not extend into the sedimentary cover. The existence of through-going faults suggests the potential for spatially pervasive fluid movement along faults. Further, observations reveal pervasive, subhorizontal intrabasement reflectors (igneous sills) that terminate at the basement-sediment interface. Results have direct implications for wastewater injection and seismicity in north-central Oklahoma and southern Kansas. Additionally, they provide insight into the characteristics of basement-rooted structures around the NFZ region and suggest a means by which to characterize basement structures where seismic data are available.

Detection of seismic refraction signals using a variance fractal dimension technique

Geophysics ◽  
2000 ◽  
Vol 65 (1) ◽  
pp. 286-292 ◽  
Author(s):  
Lingxiu Jiao ◽  
Wooil M. Moon
Keyword(s):  
Fractal Dimension ◽  
High Resolution ◽  
Seismic Reflection ◽  
Seismic Refraction ◽  
Window Size ◽  
Real Data ◽  
Seismic Signals ◽  
Seismic Reflection Data ◽  
Reflection Seismic ◽  
Reflection Data

Seismic signals in deep crustal surveys are often contaminated with various types of noise, mainly caused by the low signal‐to‐noise (S/N) earth environment. A variance fractal dimension (VFD) technique is investigated and tested with real data sets for detection of seismic refraction signals from background noise. The data tested in this study were collected during the 1992 Lithoprobe Abitibi‐Grenville Transect high‐resolution refraction and wide‐angle reflection seismic experiments. The sharpness of transition features on the VFD trajectory is used as a criterion for distinguishing specific seismic phases. The window size and window interval applied in the application of VFD technique were determined using synthetic seismic data for generation of the optimum VFD trajectory. The window size of 48 samples and the window interval of 8 sample intervals were chosen to calculate the fractal dimension values and create the trajectories for detecting phases Pg, Pn, PmP, and ground roll. The VFD technique was also tested and applied for automatic detection of the first breaks in the high‐resolution seismic reflection data collected during the 1990 Lithoprobe regional and high‐resolution seismic surveys. The sharp transition features corresponding to the first arrivals in the seismic reflection data are distinct and provide us with a robust and powerful tool for separating the seismic signals from noise.

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