Given the boulder-sized clasts and different mineralogy, geologists have inferred that these clasts must have originated from several different large vents close by. The chain begins with Cuba and ends with Trinidad. Water Island is the smallest populated island of the USVI It is only 491.5 acres in size, it is also 2½ miles long and ½ to 1 mile wide. The Stratigraphy of the Virgin Islands, U.S.A. Abh. The Virgin Islands National Park is an American national park preserving about 60% of the land area of Saint John in the United States Virgin Islands, as well as more than 5,500 acres (2,226 ha; 9 sq mi) of adjacent ocean, and nearly all of Hassel Island, just off the Charlotte Amalie, Saint Thomas harbor. “Isis” in Dresden, There is no doubt that the key to these problems lies in the larger islands of the Greater Antilles, for it is only there that unaltered fossiliferous sediments occur and can be studied in relation to the igneous intrusion and metamorphism. Point Reyes National Seashore, California. Virgin Islands National Park's hills, valleys and beaches are breath-taking. According to Hill (4), however, “in mid-Tertiary times granitoid intrusions were pushed upward into the sediments of the Greater Antilles, the Caribbean, Costa Eican, and Panamic regions.” Frazer, on the other hand (8), considered the nuclear axis of Cuba and San Domingo, and possibly of all the Caribbean islands, to be Archaean, a view upheld also by Dr. W. Bergt. The 1983 Master Plan has been put into practice. Location: U.S. Virgin Islands Established: August 2, 1956 Size: 15,135 acres. Igneous activity then changed to that of an island arc, characterized by the Louisenhoj Formation, consisting of andesite and basalt. (7). The Caribbean Plate borders the North American Plate, the South American Plate and the Cocos Plate. By continuing to use our website, you are agreeing to our, American Association of Petroleum Geologists, Cushman Foundation for Foraminiferal Research, Mineralogical Society of Great Britain and Ireland. Wythe Cooke considers that the igneous basal complex in the Dominican Republic certainly dates from Cretaceous time, but that part is probably older. Silt or sand-sized material is most common unlike the Louisenhoj Formation boulders, suggesting a more distant volcanic source. We use cookies to distinguish you from other users and to provide you with a better experience on our websites. John's wide range of rainfall and exposure give it surprising variety. (9). Radiolarian chert deposited along with the submarine volcanic activity, accompanied by dikes and small plutons in the Careen Hill Intrusive Suite. Photograph by RosaBetancourt, 0 … More than 800 subtropical plant species grow in areas from moist, high-elevation forests to desertlike terrain to mangrove swamps, among them mangoes, soursops, turpentine trees, wild tamarind, century plants, and sea grapes. The islands … Terrigenous sediments are absent, and the entire volcanic sequence appears to have been extruded on the ocean floor. View all Google Scholar citations The geology of the U.S. Virgin Islands includes mafic volcanic rocks, with complex mineralogy that first began to erupt in the Mesozoic overlain and interspersed with carbonate and conglomerate units. Create your own unique website with customizable templates. Terrigenous sediments are absent, and the entire volcanic sequence appears to have been extruded on the ocean floor. The eruptive center during Louisenhoj time was probably located close to Pillsbury Sound, between St. Thomas and St. John. Keratophyre magma is believed to have been a low-melting fraction of hydrated mantle material which was depressed during compressive deformation. Over many eons, molten rock flowed from volcanic vents, forming the foundation of the island that we now know as St. John. 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. On Saint John, a large dike swarm formed in formed in the early or mid-Cenozoic. In 1493 Columbus sighted the large assemblage of islands and cays and named it after St. Ursula's legendary 11,000 virgins. The poorly exposed Hans Lollik Formation (6000–10,000 feet exposed) is the youngest unit present and lithologically resembles the Louisenhoj Formation. The Danes began colonization in the 17th century, and in 1717 planters arrived on St. John. * Views captured on Cambridge Core between . 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. [2], Geologic History, Stratigraphy & Tectonics,,, Salt River Bay National Historical Park and Ecological Preserve,, 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 size—19 square miles—St. 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, A NPS Soil Resources Inventory project has been completed for Virgin Islands National Park and can be found on the NPS Data Store.