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24-752: Miami Limestone forms the Atlantic Coastal Ridge in southeastern Florida, near the coast in Palm Beach , Broward and Miami Dade counties. It also lies under the eastern (Miami-Dade County) part of the Everglades , Florida Bay , and the lower Florida Keys from Big Pine Key to the Marquesas Keys . Mitchell-Tapping also states that a component of the Miami Limestone extends under the Gulf of Mexico north to

48-465: A Spanish privateer schooner and her two British prizes, the ship Golden Grove and the brig Ceres , which the Spanish privateer had captured some two months earlier. The Spaniards had armed Golden Grove with eight 6-pounder guns and six swivels , and given her a crew of 50 men. The brig too was armed with swivels and small arms. The Spanish schooner carried six guns and a crew of 70 men. Pigot engaged

72-570: A calcite mosaic around the nucleus. Uranium-thorium dating indicates that the ooids in the Fort Dallas and Key West units formed at the same time. The fossils in the formation underlying the Everglades, which does not include any ooids , consists primarily of a single bryozoan species, Schizoporella floridana . The Miami Limestone was deposited during the Sangamon interglacial , when southern Florida

96-480: A fossil barrier bar on the sea-ward side with fossil shoals and channels inland to the northwest. The fossil channels underlie depressed features known as "transverse glades". The ridge in Miami-Dade County is 2 to 10 miles (3.2 to 16.1 km) wide. North of Homestead the ridge is 8 to 15 feet (2.4 to 4.6 m) above sea level, with some places 20 feet (6.1 m) or more above sea level. West of Homestead, it

120-487: A point 112 kilometers west of Tampa . The part of the Miami Limestone forming the Atlantic Coastal Ridge and the lower Florida Keys is an oolitic grainstone which includes fossils of corals, echinoids , mollusks , and algae. The oolitic formation in the lower Florida Keys has less quartz sand and fewer fossils than does the oolitic formation on the mainland. Based on those differences, Mitchel-Tapping divided

144-516: A relict oolite shoal, a few miles wide and 10 to 15 feet (3.0 to 4.6 m) high. The relict beach ridges that make up the Atlantic Coastal Ridge north of Palm Beach County decrease towards the south, and disappear north of Miami. The Miami Rock Ridge formed as a shoal of calcareous oolite, comparable to the ongoing process on the Bahama Banks . The area in which the Miami Rock Ridge formed is on

168-473: Is 5 to 8 feet (1.5 to 2.4 m) above sea level. The ridge is covered by sand, sometimes very thinly. The ridge has historically been a barrier to water flow from the Everglades , except at a few spots. St. Marys River (Florida%E2%80%93Georgia) The St. Marys River (named Saint Marys River by the United States Geological Survey , ) is a 126-mile-long (203 km) river in

192-571: Is a relict beach ridge created during what is called the "Pamlico time". Except in the southernmost part of the Atlantic Coastal Ridge (in Broward and Miami-Dade counties, the ridge was likely the mainland shore of Florida in the Pamlico period. The profile of the ridge on the sea-ward side closely resembles the current profile of the nearshore underwater slope along the Atlantic coast of Florida, suggesting that

216-721: The Florida scrub ecosystem. The Anastasia Formation shallowly underlies the Atlantic Coastal Ridge along most of the east coast of Florida. In southernmost Florida, the Anastasia Formation is deeper, 100 feet (30 m) or more under the surface in Miami-Dade County, where it is overlain by Miami Limestone . The Atlantic Coastal Ridge may have two or more parallel ridges which originated as beach ridges and swales produced by longshore drift . Seven parallel ridges have been described in Palm Beach County . The eastern side of

240-687: The Tamiami Formation in Collier and mainland Monroe counties, and by the Key Largo Limestone in the lower Florida Keys . Atlantic Coastal Ridge The Atlantic Coastal Ridge is a geomorphological feature paralleling the Atlantic coast of Florida from the border with Georgia to Miami-Dade County , where it transitions into the Miami Rock Ridge . For most of its length it consists of one or more relict beach ridges created when

264-472: The Fort Dallas Oolite. The ooids have generally formed on a nucleus of calcite crystals, and occasionally on shell fragments and quartz grains, and are covered with up to five layers of calcite. Fort Dallas ooids have a defined layer of calcite around the nucleus. The Key West Oolite is mostly white, includes very little quartz sand, does not harden on exposure to air or water, and its ooids do not have

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288-582: The Miami Limestone into the Fort Dallas Oolite on the mainland and under most of Florida Bay, and the Key West Oolite, under the southernmost corner of Florida Bay within the Everglades park boundaries, along the west side of the middle Florida Keys, and in the lower Keys, including the Marquesas Keys to near the Dry Tortugas . The Fort Dallas Oolite, white to yellow in color, is soft but hardens on exposure to air or water. Quartz sand grains occur throughout

312-494: The Miami limestone caps the Miami Rock Ridge. It is up to 35 feet (11 m) thick along the ridge summit, but extends only part-way under the Everglades. Valleys that cross the oölitic layer of the ridge probably originated as tidal channels when the sea level was high enough to partially inundate the ridge. The Atlantic Coastal Ridge, or Miami Rock Ridge, has a maximum elevation of 7.3 m in Miami-Dade County. It has been interpreted as

336-476: The easternmost ridge (on the barrier islands ) probably dates from 6,000 to 16,000 years BP. Moving inland the other ridges are progressively lower, and probably date to the Pamlico time. Before urban development eliminated them, there were large areas of scrub on all but the westernmost (and lowest) ridge, which had smaller areas of scrub. In northern Palm Beach County the ridges were 20 to 50 feet (6.1 to 15.2 m) above sea level. In southernmost Palm Beach County

360-517: The edge of the Florida platform . Southward movement of quartz sand along the Florida coast did not reach the area, and the lack of sand and shallow submergence (less than 6 feet (1.8 m)) of the area during the Pamlico time created conditions for oolite to form. The position of the Miami Rock Ridge largely corresponds with that of Pliocene reef tracts which extended from Palm Beach County to southern Miami-Dade County. The oölitic (upper) facies of

384-565: The harbour in the French privateer schooner Matilda , which the British had captured three days earlier. On 7 July Pigot took Matilda twelve miles (nineteen kilometres) up the St Marys River to attack three vessels reported to be there. Along the way militia and riflemen fired on Matilda . Eventually the British reached the three vessels, which were lashed in a line across the river. They consisted of

408-457: The ridge was formed by the same processes that are currently operating along the Florida coast. The preservation of that profile was likely due to a rapid fall of sea level at end of the Pamlico period due to a rapid onset of glaciation at the beginning of the Late Wisconsin. Old dune fields along the ridge were originally covered mainly by the sand pine scrub and scrubby flatwoods varieties of

432-470: The ridges curved towards the west and were irregular. This pattern has been attributed to changes in the channel of the Hillsboro River . The Miami Rock Ridge is a continuation of the Atlantic Coastal Ridge south of Palm Beach County. North of Palm Beach County the Atlantic Coastal Ridge is composed of quartz sand, but South of Palm Beach County it is increasingly composed of calcareous oolite , becoming

456-545: The river emerges from the Okefenokee Swamp at Baxter, Florida/Moniac, Georgia. It then flows south, then east, then north, then east-southeast intersecting I-95 near Yulee , and finally emptying its waters into the Atlantic, near St. Marys, Georgia and Fernandina Beach, Florida . The U.S. Board on Geographic Names discourages the use of apostrophes in place names, including St. Marys River. On 6 July 1805, Lieutenant Robert Pigot of HMS  Cambrian arrived off

480-614: The sea level was about 30 feet (9.1 m) higher than at present. The southernmost part of the Atlantic Coastal Ridge (the Miami Rock Ridge) was created as a carbonate platform during the same period. Before human modification for agriculture and urban development, much of the ridge hosted scrub vegetation. The Atlantic Coastal Ridge extends from the St. Marys River , which is the boundary between Florida and Georgia, to west of Homestead in southern Miami-Dade County. The Atlantic Coastal Ridge

504-648: The southeastern United States . The river was known to the Timucua as Thlathlothlaguphka , or Phlaphlagaphgaw , meaning "rotten fish". French explorer Jean Ribault named the river the Seine when he encountered it in 1562. From near its source in the Okefenokee Swamp , to its mouth at the Atlantic Ocean , it forms a portion of the border between the U.S. states of Georgia and Florida . The river also serves as

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528-550: The southernmost point in the state of Georgia. The St. Marys River rises as a tiny stream, River Styx, flowing from the western edge of Trail Ridge, the geological relic of a barrier island/dune system, and into the southeastern Okefenokee Swamp. Arching to the northwest, it loses its channel within the swamp, then turns back to the southwest and reforms a stream, at which point it becomes the St. Marys River. Joined by another stream, Moccasin Creek,

552-400: The vessels for an hour, and then after Matilda had grounded, took his crew in her boats and captured Golden Grove . The British then captured the other two vessels. Lastly, Pigot fired on a group of 100 militia, with a field gun, dispersing them. The British had two men killed, and 14 wounded, including Pigot, who had received two bullet wounds to head and one to a leg. A crowd of Americans on

576-677: Was under a shallow sea. Falling sea levels during the Wisconsin glaciation exposed the formation to air and rain, and rainwater percolating through the deposits replaced aragonite with calcite and formed an indurated rock. The Miami Limestone is underlain by the Anastasia Formation in eastern Broward and extreme southeastern Palm Beach counties, by the Fort Thompson Formation in southeastern Palm Beach County, central Broward County, all of Miami-Dade County, and Florida Bay , by

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