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may explain north-plunging late folds, due to eastward movement of the
Caribbean plate. The formation of the Cayman Trough produced the last significant tectonic feature on the islands after 39 million years ago, with sinistral strike-slip faults. A structural block produced as a result creates a 5.7
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basalt. Silt or sand-sized material is most common unlike the
Louisenhoj Formation boulders, suggesting a more distant volcanic source. In fact, sediments become finer, ascending upward into the Picara Member and Mandal Member. Striking slump folds and deformation of limestone and conglomerate beds
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deposited along with the submarine volcanic activity, accompanied by dikes and small plutons in the Careen Hill
Intrusive Suite. An extensional environment is inferred by the presence of sheeted dikes. Geologists have debated the origins of keratophyres, suggesting a back-arc basin environment,
184:
more typical of island arcs, above the Water Island
Formation. Except as pillow basalt on Ramgoat Cay, primary volcanic units are scarce from this time period. Given the boulder-sized clasts and different mineralogy, geologists have inferred that these clasts must have originated from several
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One of the most in-depth studies of groundwater in the U.S. Virgin
Islands was conducted by the U.S. Geological Survey in 1995, focused on Saint Croix. The south-central part of the island is underlain by alluvium and carbonate rocks, including lenses of silt and clay. The
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Kingshill
Limestone and Pliocene Post-Kingshill Limestone are all a single hydrological unit. The water-table aquifer ranges between five and 68 feet below the grounds surface and overall groundwater in the area contained comparatively high sodium chloride concentrations.
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243:. Broad folds formed due to north–south compression, likely due to the collision of the Greater Antilles arc with the Bahama Platform of the North American Plate. Deformation increases northward across Saint John.
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although this is challenged by high-levels of silica in the rocks. Local hydrothermal alteration was proposed as a reason for metal anomalies in the
Lameshur Volcanic-Intrusive Complex.
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Unlike Saint John, on Saint Thomas, radiolarian chert exists but is much rarer. Pyroclastic flows are preserved on Saint Thomas, together with limited fossil-bearing
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followed the episode of compression, forming around 39 million years ago in the Eocene. East-west compression brought brittle fractures filled with veins of
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On Saint John, the Tutu
Formation is the youngest stratified unit, although volcanism continued on the neighboring
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cement in upper rock units. The Outer Brass
Limestone deposited during a lull in volcanic activity in the
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kilometer sinistrally offset contact between the Water Island and
Louisenhoj formations.
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The 1.5 kilometer thick Louisenhoj Formation contains clasts which record a shift toward
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includes mafic volcanic rocks, with complex mineralogy that first began to erupt in the
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bound together with calcareous cement and including both marble and andesite clasts.
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below water, creating the two kilometer thick Water Island Formation in the
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The Narrows pluton and Virgin Gorda batholith, which are dominated by
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overlain and interspersed with carbonate and conglomerate units.
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Salt River Bay National Historical Park and Ecological Preserve
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315:"Hydrogeology of south-central St. Croix, U.S. Virgin Islands"
151:, the most research has focused on the origins of Saint John.
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219:, the overlying Tutu Formation took shape with volcanic
204:. The limestone unit also contains calc-silicate rocks,
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48:. Unsourced material may be challenged and removed.
154:The island began to form with keratophyre and
1100:Geography of the United States Virgin Islands
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135:Geologic history, stratigraphy, and tectonics
57:"Geology of the United States Virgin Islands"
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302:https://pubs.usgs.gov/pp/p1631/P1631-tag.pdf
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108:Learn how and when to remove this message
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280:Jealousy formation, the Miocene and
139:Although the island chain comprises
46:adding citations to reliable sources
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185:different large vents close by.
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33:needs additional citations for
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1095:Geology of the United States
744:Geology of the United States
697:Virgin Islands Coral Reef NM
368:United States Virgin Islands
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576:Delegates to U.S. Congress
162:on oceanic plateau crust.
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1046:Northern Mariana Islands
581:Congressional district
571:USVI Police Department
313:Graves, R. P. (1995).
233:British Virgin Islands
746:by political division
611:Charlotte Amalie West
378:Charlotte Amalie
517:Lieutenant Governors
42:improve this article
1056:U.S. Virgin Islands
682:Buck Island Reef NM
443:Tourist attractions
258:. Spreading at the
124:U.S. Virgin Islands
484:Telecommunications
470:Danish West Indies
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702:Virgin Islands NP
687:Christiansted NHS
564:Same-sex marriage
323:10.3133/wri934162
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1020:Washington, D.C.
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527:Attorney General
522:Dept. of Justice
438:Sugar production
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59: –
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53:Find sources:
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31:This article
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1051:Puerto Rico
959:South Dakota
949:Rhode Island
944:Pennsylvania
924:North Dakota
659:Water Island
654:Saint Thomas
626:Frederiksted
406:Demographics
396:Bibliography
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267:Hydrogeology
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210:conglomerate
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145:Saint Thomas
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40:Please help
35:verification
32:
15:
1028:Territories
874:Mississippi
789:Connecticut
644:Saint Croix
539:Legislature
228:is common.
164:Radiolarian
141:Saint Croix
1089:Categories
989:Washington
909:New Mexico
904:New Jersey
779:California
649:Saint John
507:Government
289:References
235:until the
149:Saint John
98:March 2023
68:newspapers
999:Wisconsin
964:Tennessee
869:Minnesota
844:Louisiana
544:Elections
512:Governors
475:Governors
455:Geography
450:Education
416:Languages
381:(capital)
364:Territory
274:Oligocene
223:and rare
221:turbidite
202:Santonian
190:limestone
984:Virginia
934:Oklahoma
914:New York
889:Nebraska
879:Missouri
864:Michigan
854:Maryland
839:Kentucky
819:Illinois
794:Delaware
784:Colorado
774:Arkansas
621:Cruz Bay
554:Cannabis
499:Politics
460:Highways
421:Religion
282:Pliocene
256:limonite
248:tonalite
241:Cenozoic
225:pyroxene
198:Turonian
178:andesite
129:Mesozoic
1004:Wyoming
979:Vermont
884:Montana
824:Indiana
804:Georgia
799:Florida
769:Arizona
759:Alabama
636:Islands
549:Members
465:History
433:Economy
411:Culture
401:Climate
278:Miocene
252:calcite
215:In the
194:calcite
82:scholar
939:Oregon
894:Nevada
834:Kansas
809:Hawaii
764:Alaska
752:States
664:Others
593:Cities
388:Topics
237:Eocene
206:marble
182:basalt
84:
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63:
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969:Texas
849:Maine
814:Idaho
674:Parks
426:Women
167:chert
89:JSTOR
75:books
1041:Guam
974:Utah
929:Ohio
829:Iowa
559:LGBT
254:and
208:and
200:and
180:and
147:and
120:The
61:news
366:of
319:doi
276:to
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