Surrency bright spot: possible evidence for fluid in the deep crust

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:5951893

Wille, D M; Brown, L D; Nelson, K D; Arnow, J A; McBride, J H; Oliver, J E; Kaufman, S

New COCORP profiles in eastern Georgia may indicate the presence of trapped fluid and/or gas in the deep crust. The evidence takes the form of an anomalously high amplitude reflection occurring at 6 sec 2-way time (15-18 km depth) on Georgia line 16. This reflection, termed the Surrency bright spot bears a startling resemblance to bright spots that are observed by the petroleum industry in sedimentary sequences, and which are commonly associated with hydrocarbon accumulations. The Surrency bright spot has a very high amplitude, is overlain by a faint anticlinal feature, and is quite flat over its 10 km extent - features characteristic of bright spots in sedimentary strata. Bright spots in sedimentary strata commonly result from interfaces between fluids of differing densities or between a gas and a fluid, trapped within porous sedimentary rock. At mid-crustal depth most gases only exist in a supercritical phase. Preliminary calculations indicate that the Surrency bright spot has a reflection coefficient of .18 to .36, which is extremely high for such deep reflections. It is questionable whether a rock-rock interface at this depth could produce such a reflection coefficient. The bright reflection occurs within a broad zone of complex dipping reflections that extend downward through the crust, and which have been suggested to mark a Paleozoic suture zone. The authors speculate that the Surrency bright spot may represent formation and/or metamorphic fluids trapped within underthrust sedimentary strata.

• Research Organization: Cornell Univ., Ithaca, NY (USA)
• OSTI ID: 5951893
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 36
• Country of Publication: United States
• Language: English

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03 NATURAL GAS
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ANTICLINES
EARTH CRUST
EXPLORATION
FEDERAL REGION IV
GEOLOGIC DEPOSITS
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
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RESOURCE POTENTIAL
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USA