Sediment Velocities and Deep Structure from Wide-Angle Reflection Data around Leg 116 Sites

Bull, Jonathan M.; Scrutton, R. A.

doi:10.2973/odp.proc.sr.116.155.1990

Cited by 9 publications

(10 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It has previously been recognized that the long wavelength undulations contribute little to the total shortening within the deformation area (Weissel & Geller 1981;Gordon et al 1990). By coarse digitization of oceanic basement from seismic profiles and depth conversion using the velocities from Bull & Scrutton (1990b) we found that the long wavelength undulations had certainly contributed much less than 0.1% shortening, in agreement with the previous studies.…”

Section: Estimates Of Shortening From Multichannel Seismic Reflectionsupporting

confidence: 77%

See 1 more Smart Citation

Seismic reflection images of intraplate deformation, central Indian Ocean, and their tectonic significance

Bull

Scrutton

1992

JGS

View full text Add to dashboard Cite

, which is at the lower end of predictions from plate motions, but significant enough to recognize this area as a diffuse plate boundary. The formation of long-wavelength basement undulations and the reactivation of fracture zones and ridge-parallel fault fabrics are linked in a unified tectonic model driven by the high level of intraplate compressive stress in the area. There is little evidence from the seismic profiles for intraplate deformation starting before the widespread unconformity dated as 7 Ma.

show abstract

Section: Estimates Of Shortening From Multichannel Seismic Reflectionsupporting

confidence: 77%

“…Displacements of a number of horizons at the two faults are given bottom left. These displacements were calculated using the velocity structure in the sedimentary cover established by Bull & Scrutton (1990b). The scatter in the value on the north fault probably arises in part from difficulty in interpretation near to the fault plane.…”

Section: Tectonic Historymentioning

confidence: 99%

Seismic reflection images of intraplate deformation, central Indian Ocean, and their tectonic significance

Bull

Scrutton

1992

JGS

View full text Add to dashboard Cite

show abstract

“…Superimposed on these -175 km wavelength ridges are smaller-scale faulted and rotated thrust blocks with wavelengths of 5-20 km (Cochran et al 1989). These faults are prevalent within the sedimentary column and may cut into or through the lower crust, as suggested by recent multichannel reflection profiles (Bull & Scrutton 1990aJestin, Chamot-Rooke & de Voogd 1993). They are probably widespread and must have been recently active, given the diffuse zone of teleseismic and microseismic activity throughout the region (Sykes 1970;Stein & Okal 1978;Wiens et al 1985;Neprochnov et al 1988).…”

Section: Introductionmentioning

confidence: 85%

“…3) along line 2 south of 4"N (Leger & Louden 1990) and from the adjacent profile Vema-3616 to the north (Geller et al 1983). The sediment was divided into three layers according to the seismic refraction models and consistent with SIB sediment velocity measurements at the ODP Leg 116 sites (Bull & Scrutton 1990b). Densities for the upper two sediment layers conform to measurements on cores from ODP sites 717 and 718 (Cochran et al 1989).…”

Section: Gravity Modelsmentioning

confidence: 99%

“…This alteration is consistent with the penetration of water into the lower crust down steeply dipping normal faults, which have been reactivated by compressive stress within the deformation zone. Such faults have recently been imaged by deep multichannel reflection profiles (Bull & Scrutton 1990a. Enhanced circulation of water in the crust and through the sediment may also help to explain the observed heat flow anomalies in this region.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Variations in crustal structure related to intraplate deformation: evidence from seismic refraction and gravity profiles in the Central Indian Basin

Louden

1995

Geophysical Journal International

View full text Add to dashboard Cite

S U M M A R YIn this paper, an analysis of seismic refraction and gravity profiles is presented to define the crustal structure across a ridge-trough deformational feature in the Central Indian Basin. The purpose is to investigate what effects the deformation has had on the crust during the incipient rupture of oceanic lithosphere. The wide-angle seismic reflection/refraction profiles which are modelled in this paper come from two previously reported data sets (three R/V Conrad profiles and two R/V Mendeleev profiles) located south of the ODP Leg 116 drilling sites, where N-S reflection profiles clearly delineate a symmetrically upwarped and faulted basement ridge bounded by two undeformed troughs. Previous analyses of the refraction data gave conflicting accounts of velocity and thickness variations between trough and ridge structures. In this paper, the refraction profiles are displayed in similar manner and both u, and up structures are determined by forward modelling using 1-D reflectivity synthetics. Results indicate a typically mature oceanic upper crust for all profiles (up = 4.5-6.3 km s-'; depth = 0-1.2 km; u = 0.35-0.27) above a transitional crust (up = 6.3-6.8 km s-'; depth = 1.2-2.6 km; u = 0.25). In the middle and lower crust, there are major changes between trough and ridge profiles: (i) within the basement troughs, there is a sharp transition between layer 3A (up = 6.7 km s-'; thickness = 1.7 km; u = 0.26) and layer 3B (up = 7.1-7.4 km s-'; thickness = 2.0-2.5 km; u = 0.25); (ii) on the ridge crest, up is increased to 7.2 km s-' in layer 3A ( a = 0.26) but reduced to 6.6 f 0.2 km s-' in layer 3B (u = 0.24-0.30), forming a distinct low-velocity zone in both up and us. The crustal thickness is reduced progressively at its base from 6.2 f 0.3 km to 5.4 f 0.2 km. A 2-D gravity model across the ridge-trough structure, based on the 1-D seismic velocity-depth models, is consistent with an observed anomaly of 40-45 mGal.These results demonstrate that the crust does not thicken beneath the basement ridge crest, as has previously been suggested. The crustal structure is, therefore, more consistent with lithospheric deformation by buckling than by boudinage. The crust beneath the ridge is altered primarily by the development of a low-velocity and low-density zone within the high-velocity lower crust of seismic layer 3B. A possible primary origin for the LVZ is by serpentinization at low temperatures of olivine clasts within the mafic gabbro of layer 3B. Asymmetric folding of the lower crust or lateral flow of the more viscous serpentine might explain the possible crustal thinning under compression. Penetration of water to deep crustal levels within this region is consistent with recent deep multichannel reflection images of reverse faults which penetrate into or through the lower crust. It is also consistent with fluid flow along faults within the sediment which have perturbed the surface geothermal gradients. This process could explain the discrepancy between the high regionally averaged heat flow and normal...

show abstract

Periodic deformation of oceanic crust in the central Indian Ocean

Krishna¹,

Ramana²,

Rao³

et al. 1998

J. Geophys. Res.

View full text Add to dashboard Cite

Sediment Velocities and Deep Structure from Wide-Angle Reflection Data around Leg 116 Sites

Cited by 9 publications

References 15 publications

Seismic reflection images of intraplate deformation, central Indian Ocean, and their tectonic significance

Seismic reflection images of intraplate deformation, central Indian Ocean, and their tectonic significance

Variations in crustal structure related to intraplate deformation: evidence from seismic refraction and gravity profiles in the Central Indian Basin

Periodic deformation of oceanic crust in the central Indian Ocean

Contact Info

Product

Resources

About