. The oldest rock unit of the northern Virgin Islands is the ?Lower Cretaceous Water Island Formation (10,000–15,000 feet plus), which consists of keratophyre flows and tuffs, spilite flows, and radiolarian tuffs. © 1996-2015 National Geographic Society, © 2015- The sinistral strike-slip faults in many cases have a considerable normal component, and appear to parallel the principal fault of the Anegada Trough. , Geologic History, Stratigraphy & Tectonics, https://pubs.usgs.gov/pp/p1631/P1631-tag.pdf, https://pubs.er.usgs.gov/publication/wri934162, Salt River Bay National Historical Park and Ecological Preserve, https://en.wikipedia.org/w/index.php?title=Geology_of_the_United_States_Virgin_Islands&oldid=911297544, Geography of the United States Virgin Islands, Creative Commons Attribution-ShareAlike License, This page was last edited on 17 August 2019, at 23:24. Narro w, rock-w alled terraces are still present on some of the steep, forest-covered slopes. An extensional environment is inferred by the presence of sheeted dikes. The work of Cleve (1), Hill (4), Vaughan (5), and others (6) in the American Virgin Islands, Porto Rico, the Dominican Republic, Cuba, Haiti, and Jamaica, indicates that the British Virgin Islands form geologically only the eastern termination of that main group of islands and have been subjected to the same earth movements as them. Here you will find all you need to know about the natural history of the park. 2 GEOLOGY OF ST JOHN, U.S. VIRGIN ISLANDS colonial times. To search for additional information, visit the Data Store. Svensk. To search for additional information, visit the Data Store. Published online by Cambridge University Press. Virgin Islands National Park in the U. S. Virgin Islands is located on another transform plate boundary, where the Caribbean Plate is sliding past the oceanic part of the North American Plate. The latter are composed essentially of Tertiary volcanic rocks of andesitic or basaltic type, with or without development of sedimentary strata which, when present, only dip at gentle angles and never show the violent effects of such dynamic forces as have been responsible for the folding and “up-ending” of the strata in the Virgin Islands. Despite its small sizeâ19 square milesâSt. Contact-metamorphic aureoles of hornblende hornfels and probably pyroxene hornfels facies surround the plutons. There is also a north-south set of normal faults. 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. The servicewide Geodiversity Atlas provides information on geoheritage and geodiversity resources and values within the National Park System. East-west compression brought brittle fractures filled with veins of calcite and limonite. Local hydrothermal alteration was proposed as a reason for metal anomalies in the Lameshur Volcanic-Intrusive Complex. Except as pillow basalt on Ramgoat Cay, primary volcanic units are scarce from this time period. Stockholm, Contributions to the Geology and Palæontology of the Canal Zone, Panama, The Geology and Physical Geography of Jamaica, The Geology of Porto Rico and the Virgin Islands. Full text views reflects the number of PDF downloads, PDFs sent to Google Drive, Dropbox and Kindle and HTML full text views. It also feels pressure from the numerous cruise ships that disgorge large numbers of visitors at once, badly straining park resources. There are many islands that make up the virgin islands like St.John, St.Thomas, St.Croix, and the smallest of the islands, Water Island. The 1.5 kilometer thick Louisenhoj Formation contains clasts which record a shift toward clinopyroxene andesite and basalt more typical of island arcs, above the Water Island Formation. Geologists have debated the origins of keratophyres, suggesting a back-arc basin environment, although this is challenged by high-levels of silica in the rocks. Today, though its boundary includes three-quarters of St. John, the national park owns only slightly more than half the island. Sort By: 20. In the Late Cretaceous, the overlying Tutu Formation took shape with volcanic turbidite and rare pyroxene basalt. You could not be signed in. the picture above show fort willough which is a beautiful and popular landform to visit. The Virgin Islands National Park covers much of the island and includes substantial offshore area as well. Gesell. St. John is a volcanic island, part of a submarine mountain range which includes the larger islands of the Greater Antilles, the Virgin Islands and the Lesser Antilles. 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. Pyroclastic flows are preserved on Saint Thomas, together with limited fossil-bearing limestone deposits and calcite cement in upper rock units. By mid-century 88 plantations had been established there; slaves stripped the steep hillsides of virgin growth and cultivated the cane. Geodiversity refers to the full variety of natural geologic (rocks, minerals, sediments, fossils, landforms, and physical processes) and soil resources and processes that occur in the park. Source: Data Store Saved Search 3215. The island has an weird shape with many bays and peninsulas. Narrow, rock-walled terraces are still present on some of the steep, forest-covered slopes. More than 100 million years ago, complex geologic processes began forming the setting of Virgin Islands Although the island chain comprises Saint Croix, Saint Thomas and Saint John, the most research has focused on the origins of Saint John. The Narrows pluton and Virgin Gorda batholith, which are dominated by tonalite followed the episode of compression, forming around 39 million years ago in the Eocene. for this article. Virgin Islands Coral Reef National Monument, established in 2001, encompasses 5,143 ha (12,708 ac) of submerged lands adjacent to St. John. The island formed during the Cretaceous with the eruption of the Water Island Formation, consisting of keratophyres and pillow basalts. Spreading at the Cayman Trough may explain north-plunging late folds, due to eastward movement of the Caribbean plate. See Maps and Reports, below. The island began to form with keratophyre and pillow basalt below water, creating the two kilometer thick Water Island Formation in the Early Cretaceous on oceanic plateau crust. USVI has a total of 133 square miles, while the BVI only have a total of 59 square miles. The contrasting mineralogy of the spilite and augite andesite is thought to have originated from contrasting environments of extrusion. Photograph by RosaBetancourt, 0 people images/Alamy, https://www.nationalgeographic.com/travel/national-parks/virgin-islands-national-park.html. A NPS Soil Resources Inventory project has been completed for Virgin Islands National Park and can be found on the NPS Data Store.