Document Type

Article

Publication Date

1-1-1992

Abstract

Five major reflectors in multichannel seismic common-depth-point line 667 (acquired with an airgun source), single-channel seismic ODP line 5 (acquired with a high-resolution watergun), and expanded spread profile C2 can be dated and tied to lithologic units. Through an initial τ-sum construction, followed by traveltime and full waveform forward modeling, ESP-derived compressional wave velocities can more accurately match traveltimes of these reflectors than full-reflectivity synthetic seismograms produced from shipboard-derived properties. Instrument calibration, drilling disturbance, and rebound effects suffered by the laboratory samples are sources of error. The authors speculate, based on the physical properties of the units that reflector "b' (~2 s TWT) marks a decrease in the degree of induration of upper Oligocene chalk. Reflector "c' marks the Cretaceous/Tertiary unconformity; "e' (~2.25 s) marks the abrupt disappearance of the terrigenous component of the sediments at the Cenomanian/Turonian boundary in response to the disappearance of the clastic supply; "f' (~2.4 s) is found above a breakup unconformity; and "g' (~3.15 s) arises near the top of the Triassic pre-rift basement in a thin (50 m) high-velocity (4 km/s) region of shallow-water reefal limestones. -Authors

Publication Source (Journal or Book title)

Proc. scientific results, ODP, Leg 122, Exmouth Plateau

First Page

393

Last Page

409

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