Major Descriptors: *BALLISTIC MISSILE DEFENSE -- TEST FACILITIES; *MILITARY
FACILITIES -- TEST FACILITIES; *TEST FACILITIES -- ENVIRONMENTAL
IMPACTS
Descriptors: CALIFORNIA; COLORADO; CONTRACTORS; FLIGHT TESTING; FLORIDA;
MARSHALL ISLANDS; MARYLAND; MASSACHUSETTS; NEVADA; NEW YORK; SIMULATION
; TENNESSEE; VALIDATION; VIRGINIA
Broader Terms: FEDERAL REGION I; FEDERAL REGION II; FEDERAL REGION III;
FEDERAL REGION IV; FEDERAL REGION IX; FEDERAL REGION VIII; ISLANDS;
MICRONESIA; NATIONAL DEFENSE; NORTH AMERICA; OCEANIA; TESTING; USA
Subject Categories: 350000*
-- Arms Control -- (1987-)
290300
-- Energy Planning & Policy -- Environment,
Health,
& Safety
10/5/456
{Item 156 from file: 103)
02037274
EDB-87-165230
Title: Geologic reconnaissance of natural fore-reef slope and a large
submarine rockfall exposure, Enewetak Atoll
Author(s): Halley, R.B.;
Slater, R.A.
Affiliation: Geological Survey, Denver,
CO
Conference Title: American Association of Petroleum Geologists annual
meeting
”
Conference Location: Los Angeles, CA, USA
Conference Date: 7 Jun 1987
Source:
AAPG
(Am.
Coden: AABUD
Publication Date:
Report Number(s):
Assoc.
Pet.
May 1987
Geol.)
Bull.
(United States)
v 71:5.
Pp 563-564
CONF-870606-
Document Type: Journal Article; Conference literature
Language: English
Journal Announcement: EDB8710
Subfile:
JMT (DOE contractor)
Country of Origin: United States
Abstract: In 1958 a submarine rockfall exposed a cross section through the
reef and fore-reef deposits along the northwestern margin of Enewetak
Atoll, Marshall Islands. Removal of more than 10/sup 8/ MT of rock left
a Cirque-shaped submarine scarp 220 m high, extending back 190 m into
the modern reef, and 1000 m along the reef trend. The scarp exposed
older, steeply dipping beds below 220 m along which the rockfall
detached. They sampled this exposure and the natural fore-reef slope
surrounding it in 1984 and 1985 using a manned submersible. The natural
slope in this area is characterized by three zone: (1) the reef plate,
crest,
and near fore reef that extends
slope of less than 10/sup 0/,
(2)
from sea level to
-16 m,
with a
the bypass slope that extends from
-16 to -275 m, with slopes of 55/sup 0/ decreasing to 35/sup 0/ near
the base,
and
(3)
a debris slope of less than 35/sup 0/ below -275 m.
Vertical walls,
grooves,
and chutes,
common on other fore-reef slopes,
appearance: (1)
appears rubbly,
a near-vertical wall from the reef crest to 76 m that
has occasional debris-covered ledges, and is composed
are sparse on the northwestern slope of Enewetak. The scarp exposes
three stratigraphic units that are differentiated by surficial
mainly of coral; (2) a vertical to overhanging wall from -76 m to -220
m that is massive and fractured, and has smooth, blocky surfaces; and
(3) inclined bedding below -220 m along which the slump block has
fractured, exposing a dip slope of hard, dense, white limestone and
dolomite that extends below -400 m. Caves occur in all three units.
Open cement-lined fractures
and voids
layered with cements are most
common in the middle unit, which now lies within the thermocline. Along
the sides of the scarp are exposed fore-reef boulder beds dipping at
30/sup 0/ toward the open sea; the steeper
(55/sup 0/)
dipping natural
surface truncates these beds, which gives evidence of the erosional
nature of the bypass slope.
Major Descriptors: *ENIWETOK -- GEOLOGY
Descriptors: GEOLOGIC SURVEYS; REEFS
Broader Terms: “GEOLOGIC STRUCTURES; ISLANDS;
OCEANIA; SURVEYS
Subject Categories:
SOc3 1b
580100*
MARSHALL ISLANDS;
-- Geology & Hydrology --
(-1989)
MICRONESIA;