Oceanic basement structure, sediment thickness, and heat flow near Hole 504B

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doi: 10.1029/98JB00698
Author(s): Swift, Stephen A.; Kent, Graham M.; Detrick, Robert S.; Collins, John A.; Stephen, Ralph A.
Author Affiliation(s): Primary:
Woods Hole Oceanographic Institution, Department of Geology and Geophysics, Woods Hole, MA, United States
Volume Title: Journal of Geophysical Research
Source: Journal of Geophysical Research, 103(B7), p.15,377-15,391. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0148-0227
Note: In English. 53 refs.; illus., incl. sketch map
Summary: A new seismic reflection survey around Hole 504B, the deepest borehole in ocean crust, reveals active faulting, possible volcanic centers, and a lateral change in the relationship of heat flow and basement structure near the borehole. Migration of single channel and multichannel seismic profiles collected in a 25 by 25 km grid with a 1 km line spacing significantly improved the resolution of basement structure and sediment thickness. West of Hole 504B, heat flow is high above east-west lineated basement ridges, whereas heat flow to the east is normal above ridges and high above two buried basement knolls. The difference is probably due to lateral variations in sediment thickness. Small, buried basement knolls are common and may have been point sources for lava flows. Hole 504B lies in a flat-floored basin that slopes gently upward to the west. A recently active fault 1.1-1.2 km south of Hole 504B is indicated by sediment reflector discontinuities that extend up to the seafloor. The fault strikes east-west and crosses a buried volcanic knoll where Holes 678B and 896A were drilled. Regionally, basement relief north of Hole 504B is 100 to 150 m lower than to the south, which we attribute to an increased spreading rate obtained from dating published local magnetic anomaly patterns with a recent timescale. We find at least five graben structures resembling failed rifts which may have formed in response to asymmetric spreading or to the change in tectonic stress accompanying the spreading rate change. South facing scarps on basement ridges are as common as north facing scarps. Sediment thickness is highly correlated to basement depth due to preferential deposition in topographic lows when the crust was 1-2 Ma old and to later winnowing. Copyright 1998 by the American Geophysical Union.
Year of Publication: 1998
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; 20 Geophysics, Applied; Basement; Bathymetry; Crust; DSDP Site 504; Deep Sea Drilling Project; Depth; East Pacific; Equatorial Pacific; Faults; Geophysical methods; Geophysical profiles; Geophysical surveys; Heat flow; IPOD; Leg 111; Leg 137; Leg 140; Leg 148; Leg 69; Leg 70; Leg 83; Leg 92; Lithofacies; Ocean Drilling Program; Ocean floors; Oceanic crust; Pacific Ocean; Panama Basin; Plate tectonics; Reflection methods; Sea-floor spreading; Seismic methods; Seismic profiles; Spreading centers; Surveys; Thickness; Velocity structure
Coordinates: N011335 N011338 W0834348 W0834357
Record ID: 1998056381
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute.