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130-544: The Floridan aquifer system , composed of the Upper and Lower Floridan aquifers, is a sequence of Paleogene carbonate rock which spans an area of about 100,000 square miles (260,000 km) in the southeastern United States. It underlies the entire state of Florida and parts of Alabama , Georgia , Mississippi , and South Carolina . The Floridan aquifer system is one of the world's most productive aquifers and supplies drinking water for nearly 10 million people. According to

260-707: A divergent to convergent plate boundary. The Alpine Orogeny developed in response to the collision between the African and Eurasian plates during the closing of the Neotethys Ocean and the opening of the Central Atlantic Ocean. The result was a series of arcuate mountain ranges, from the Tell - Rif - Betic cordillera in the western Mediterranean through the Alps , Carpathians , Apennines , Dinarides and Hellenides to

390-436: A house or road is on top. Sinkholes can be classified on the basis of the processes by which they are formed: dissolution, cover-subsidence, and cover-collapse. Formation of sinkholes can be accelerated by intense withdrawals of groundwater over short periods of time, such as those caused by pumping for frost-protection of winter crops in west-central Florida. Sinkholes that developed beneath gypsum stacks in 1994 and 2016 caused

520-645: A large proportion of the water withdrawn starting in the late 1930s. In the 1950s, all municipal, domestic, and industrial supply (except cooling), and about half of agricultural supply in Orlando, Florida had been converted to groundwater from the Floridan aquifer system. Groundwater withdrawals from the Floridan aquifer system increased steadily from 630 Mgal/d (2.4 million m/d; 1,900 acre⋅ft/d) in 1950 to 3,430 Mgal/d (13.0 million m/d; 10,500 acre⋅ft/d) in 1990. Permitting and regulations enacted during

650-418: A loss of millions of gallons mineralized water containing phosphogypsum and phosphoric acid , by-products of the production of fertilizer from phosphate rock . These sinkholes were likely formed from the collapse of preexisting dissolution cavities in the limestone beneath the stacks. Lake Jackson near Tallahassee, FL occasionally drains into a sinkhole in the bottom of the lake bed when water levels in

780-507: A pioneer of the study of karst in Slovenia and a fellow of the Royal Society , London, introduced the word karst to European scholars in 1689 to describe the phenomenon of underground flows of rivers in his account of Lake Cerknica . Jovan Cvijić greatly advanced the knowledge of karst regions to the point where he became known as the "father of karst geomorphology". Primarily discussing

910-535: A proliferation of aquatic ferns from the genus Azolla , resulting in the sequestering of large amounts of CO 2 from the atmosphere by the plants. From this time until about 34 Ma, there was a slow cooling trend known as the Middle-Late Eocene Cooling. As temperatures dropped at high latitudes the presence of cold water diatoms suggests sea ice was able to form in winter in the Arctic Ocean, and by

1040-562: A proper noun, the Slovene form Grast was first attested in 1177. Ultimately, the word is of Mediterranean origin. It has also been suggested that the word may derive from the Proto-Indo-European root karra- 'rock'. The name may also be connected to the oronym Kar(u)sádios oros cited by Ptolemy , and perhaps also to Latin Carusardius . Johann Weikhard von Valvasor ,

1170-531: A rapid surge of diversification in the early Paleogene, as survivors of the Cretaceous–Paleogene extinction event took advantage of empty ecological niches left behind by the extinction of the non-avian dinosaurs, pterosaurs, marine reptiles, and primitive fish groups. Mammals continued to diversify from relatively small, simple forms into a highly diverse group ranging from small-bodied forms to very large ones, radiating into multiple orders and colonizing

1300-872: A result, rather than a cause, of the plate tectonic forces that led to the propagation of rifting from the Central to the North Atlantic. Mountain building continued along the North America Cordillera in response to subduction of the Farallon plate beneath the North American Plate. Along the central section of the North American margin, crustal shortening of the Cretaceous to Paleocene Sevier Orogen lessened and deformation moved eastward. The decreasing dip of

1430-401: A sport than a science and so the underground karst caves and their associated watercourses were, from a scientific perspective, understudied. Karst is most strongly developed in dense carbonate rock , such as limestone, that is thinly bedded and highly fractured . Karst is not typically well developed in chalk , because chalk is highly porous rather than dense, so the flow of groundwater

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1560-483: A study published in 2018, from about 56 to 48 Ma, annual air temperatures over land and at mid-latitude averaged about 23–29 °C (± 4.7 °C). For comparison, this was 10 to 15 °C higher than the current annual mean temperatures in these areas. This rapid rise in global temperatures and intense greenhouse conditions were due to a sudden increase in levels of atmospheric carbon dioxide (CO 2 ) and other greenhouse gases . An accompanying rise in humidity

1690-519: A well in a fracture trace or intersection of fracture traces increases the likelihood to encounter good water production. Voids in karst aquifers can be large enough to cause destructive collapse or subsidence of the ground surface that can initiate a catastrophic release of contaminants. Groundwater flow rate in karst aquifers is much more rapid than in porous aquifers. For example, in the Barton Springs Edwards aquifer, dye traces measured

1820-493: Is a UNESCO World Heritage Site. Many karst-related terms derive from South Slavic languages , entering scientific vocabulary through early research in the Western Balkan Dinaric Alpine karst. The study of the various aspects of karst regions is called karstology. This includes biological, chemical, ecological, geomorphological, hydrogeological, hydrological, political, socio-economical, and other processes over

1950-542: Is a development of karst observed in geological history and preserved within the rock sequence, effectively a fossil karst. There are for example palaeokarst surfaces exposed within the Clydach Valley Subgroup of the Carboniferous Limestone sequence of South Wales which developed as sub-aerial weathering of recently formed limestones took place during periods of non-deposition within the early part of

2080-525: Is a karst landscape which is developed beneath a cover of insoluble rocks. Typically this will involve a cover of sandstone overlying limestone strata undergoing solution. In the United Kingdom for example extensive doline fields have developed at Cefn yr Ystrad , Mynydd Llangatwg and Mynydd Llangynidr in South Wales across a cover of Twrch Sandstone which overlies concealed Carboniferous Limestone ,

2210-502: Is associated with the Cretaceous–Paleogene extinction event. The boundary is defined as the rusty colored base of a 50 cm thick clay , which would have been deposited over only a few days. Similar layers are seen in marine and continental deposits worldwide. These layers include the iridium anomaly, microtektites , nickel -rich spinel crystals and shocked quartz , all indicators of a major extraterrestrial impact. The remains of

2340-611: Is characterized by features like poljes above and drainage systems with sinkholes and caves underground. There is some evidence that karst may occur in more weathering -resistant rocks such as quartzite given the right conditions. Subterranean drainage may limit surface water, with few to no rivers or lakes. In regions where the dissolved bedrock is covered (perhaps by debris) or confined by one or more superimposed non-soluble rock strata, distinctive karst features may occur only at subsurface levels and can be totally missing above ground. The study of paleokarst (buried karst in

2470-571: Is confined (and isolated) beneath the Upper Floridan aquifer and may be important to the offshore movement of groundwater in areas previously unknown. The carbonate rocks that compose the Floridan aquifer system have highly variable hydraulic properties, including porosity and permeability. Transmissivity within the aquifer system has been reported over a range of more than six orders of magnitude, from less than 8 ft/d (0.74 m/d) to greater than 9,000,000 ft/d (840,000 m/d), with

2600-468: Is developed in areas where salt is undergoing solution underground. It can lead to surface depressions and collapses which present a geo-hazard. Karst areas tend to have unique types of forests. The karst terrain is difficult for humans to traverse, so that their ecosystems are often relatively undisturbed. The soil tends to have a high pH, which encourages growth of unusual species of orchids, palms, mangroves, and other plants. Paleokarst or palaeokarst

2730-612: Is frequently unseen until the roof of a cavern suddenly collapses. Such events have swallowed homes, cattle, cars, and farm machinery. In the United States, sudden collapse of such a cavern-sinkhole swallowed part of the collection of the National Corvette Museum in Bowling Green, Kentucky in 2014. The world's largest limestone karst is Australia's Nullarbor Plain . Slovenia has the world's highest risk of sinkholes, while

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2860-399: Is not concentrated along fractures. Karst is also most strongly developed where the water table is relatively low, such as in uplands with entrenched valleys , and where rainfall is moderate to heavy. This contributes to rapid downward movement of groundwater, which promotes dissolution of the bedrock, whereas standing groundwater becomes saturated with carbonate minerals and ceases to dissolve

2990-454: Is reflected in an increase in kaolinite in sediments, which forms by chemical weathering in hot, humid conditions. Tropical and subtropical forests flourished and extended into polar regions. Water vapour (a greenhouse gas) associated with these forests also contributed to the greenhouse conditions. The initial rise in global temperatures was related to the intrusion of magmatic sills into organic-rich sediments during volcanic activity in

3120-611: Is the following: In very rare conditions, oxidation can play a role. Oxidation played a major role in the formation of ancient Lechuguilla Cave in the US state of New Mexico and is presently active in the Frasassi Caves of Italy. The oxidation of sulfides leading to the formation of sulfuric acid can also be one of the corrosion factors in karst formation. As oxygen (O 2 )-rich surface waters seep into deep anoxic karst systems, they bring oxygen, which reacts with sulfide present in

3250-576: The Bering Straits between North America and Eurasia allowing the movement of land animals between the two continents. The PETM was followed by the less severe Eocene Thermal Maximum 2 (c. 53.69 Ma), and the Eocene Thermal Maximum 3 (c. 53 Ma). The early Eocene warm conditions were brought to an end by the Azolla event . This change of climate at about 48.5 Ma, is believed to have been caused by

3380-826: The Canadian Arctic Archipelago , Svalbard and northern Greenland resulting in the Eureka Orogeny . From c. 47 Ma, the eastern margin of Greenland was cut by the Reykjanes Ridge (the northeastern branch of the Mid-Atlantic Ridge) propagating northwards and splitting off the Jan Mayen microcontinent . After c. 33 Ma seafloor spreading in Labrador Sea and Baffin Bay gradually ceased and seafloor spreading focused along

3510-858: The Izu-Bonin-Mariana and Tonga-Kermadec arcs. Subduction of the Farallon Plate beneath the American plates continued from the Late Cretaceous. The Kula-Farallon spreading ridge lay to its north until the Eocene (c. 55 Ma), when the northern section of the plate split forming the Vancouver/Juan de Fuca Plate . In the Oligocene (c. 28 Ma), the first segment of the Pacific–Farallon spreading ridge entered

3640-740: The Tasmanian Passage in the Eocene and deep ocean routes opening from the mid Oligocene. Rifting between the Antarctic Peninsula and the southern tip of South America formed the Drake Passage and opened the Southern Ocean also during this time, completing the breakup of Gondwana. The opening of these passages and the creation of the Southern Ocean established the Antarctic Circumpolar Current . Glaciers began to build across

3770-612: The Taurides in the east. From the Late Cretaceous into the early Paleocene, Africa began to converge with Eurasia. The irregular outlines of the continental margins, including the Adriatic promontory (Adria) that extended north from the African Plate, led to the development of several short subduction zones, rather than one long system. In the western Mediterranean, the European Plate

3900-506: The United States Geological Survey , total withdrawals from the Floridan aquifer system in 2000 were ranked 5th highest of all principal aquifers in the nation at 3,640 million gallons per day (Mgal/d) (13.8 million m/d; 11,200 acre⋅ft/d). Of the total, 49% (1,949 Mgal/d; 7.38 million m/d; 5,980 acre⋅ft/d) was used for irrigation, 33% (1,329 Mgal/d; 5.03 million m/d; 4,080 acre⋅ft/d)

4030-471: The air and marine ecosystems by the Eocene . Birds , the only surviving group of dinosaurs, quickly diversified from the very few neognath and paleognath clades that survived the extinction event, also radiating into multiple orders, colonizing different ecosystems and achieving an extreme level of morphological diversity. Percomorph fish, the most diverse group of vertebrates today, first appeared near

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4160-469: The hydrologic and lithologic similarities of the Tertiary carbonate formations in southeast Florida, concluded that they represented a single hydrologic unit, and named that unit the "Floridan aquifer". With additional information collection, more zones of high and low hydraulic conductivity have been identified. As a result, the name Floridan Aquifer has evolved into "Floridan aquifer system", which contains

4290-626: The range of the Dinaric Alps , stretching from the northeastern corner of Italy above the city of Trieste , across the Balkan peninsula along the coast of the eastern Adriatic to Kosovo and North Macedonia , where the massif of the Šar Mountains begins. The karst zone is at the northwesternmost section, described in early topographical research as a plateau between Italy and Slovenia . Languages preserving this form include Italian : Carso , German : Karst , and Albanian : karsti . In

4420-435: The stratigraphic column ) is important in petroleum geology because as much as 50% of the world's hydrocarbon reserves are hosted in carbonate rock , and much of this is found in porous karst systems. The English word karst was borrowed from German Karst in the late 19th century, which entered German usage much earlier, to describe a number of geological, geomorphological, and hydrological features found within

4550-629: The trench leading to the development of the Dinarides, Hellenides and Tauride mountain chains as the passive margin sediments of Adria were scrapped off onto the Eurasia crust during subduction. The Zagros mountain belt stretches for c. 2000 km from the eastern border of Iraq to the Makran coast in southern Iran . It formed as a result of the convergence and collision of the Arabian and Eurasian plates as

4680-511: The 1990s curtailed the year-on-year increases in withdrawal; however, withdrawals in 2000 increased to 4,020 Mgal/d (15.2 million m/d; 12,300 acre⋅ft/d) due to extreme drought conditions between 1999 and 2001 that prevailed over much of the Southeastern United States. Much of the increase was due to increased agricultural demand. The Floridan aquifer system spans an area of about 100,000 square miles (260,000 km) in

4810-499: The Antarctica continent that now lay isolated in the south polar region and surrounded by cold ocean waters. These changes contributed to the fall in global temperatures and the beginning of icehouse conditions. Extensional stresses from the subduction zone along the northern Neotethys resulted in rifting between Africa and Arabia, forming the Gulf of Aden in the late Eocene. To the west, in

4940-688: The Central Andes were dominated by the subduction of oceanic crust and the Southern Andes were impacted by the subduction of the Farallon-East Antarctic ocean ridge. The Caribbean Plate is largely composed of oceanic crust of the Caribbean Large Igneous Province that formed during the Late Cretaceous. During the Late Cretaceous to Paleocene, subduction of Atlantic crust was established along its northern margin, whilst to

5070-686: The Eocene-Oligocene boundary and the present day Late Cenozoic ice age began. The Paleogene began with the brief but intense " impact winter " caused by the Chicxulub impact , which was followed by an abrupt period of warming. After temperatures stabilised, the steady cooling and drying of the Late Cretaceous-Early Paleogene Cool Interval that had spanned the last two ages of the Late Cretaceous continued, with only

5200-646: The Farallon Plate beneath the western edge of South America continued from the Mesozoic. Over the Paleogene, changes in plate motion and episodes of regional slab shallowing and steepening resulted in variations in the magnitude of crustal shortening and amounts of magmatism along the length of the Andes . In the Northern Andes, an oceanic plateau with volcanic arc was accreted during the latest Cretaceous and Paleocene, whilst

5330-418: The Floridan aquifer system are of late Paleocene to early Oligocene age and are overlain by low-permeability clays of Miocene age (upper confining unit) and surficial sands of Pliocene and Holocene age ( surficial aquifer system). In west-central Florida, north Florida, and along the updip margin of the system, the limestone crops out and the aquifer system is unconfined. Where low-permeability clays of

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5460-517: The Greenland and northwest European margins and is associated with the proto-Icelandic mantle plume , which rose beneath the Greenland lithosphere at c. 65 Ma. There were two main phases of volcanic activity with peaks at c. 60 Ma and c. 55 Ma. Magmatism in the British and Northwest Atlantic volcanic provinces occurred mainly in the early Palaeocene, the latter associated with an increased spreading rate in

5590-676: The Himalayas in India through Myanmar ( West Burma block ) Sumatra , Java to West Sulawesi . During the Late Cretaceous to Paleogene, the northward movement of the Indian Plate led to the highly oblique subduction of the Neotethys along the edge of the West Burma block and the development of a major north-south transform fault along the margin of Southeast Asia to the south. Between c. 60 and 50 Ma,

5720-700: The India-Eurasia collision continued, movement of material away from the collision zone was accommodated along, and extended, the already existing major strike slip systems of the region. During the Paleocene, seafloor spreading along the Mid-Atlantic Ridge propagated from the Central Atlantic northwards between North America and Greenland in the Labrador Sea (c. 62 Ma) and Baffin Bay (c. 57 Ma), and, by

5850-427: The Labrador Sea, whilst northeast Atlantic magmatism occurred mainly during the early Eocene and is associated with a change in the spreading direction in the Labrador Sea and the northward drift of Greenland. The locations of the magmatism coincide with the intersection of propagating the rifts and large-scale, pre-existing lithospheric structures, which acted as channels to the surface for the magma . The arrival of

5980-624: The Middle Avon Park Composite Unit, and the Lisbon-Avon Park Composite Unit. The Upper and Lower Floridan aquifers behave as a single hydrogeologic unit in areas where these composite units are leaky. The Lower Floridan aquifer is generally less permeable than the Upper Floridan aquifer and the water produced can be highly mineralized and/or saline; however, the Lower Floridan aquifer is relatively fresh water to

6110-403: The Neotethys Ocean closed and is composed sediments scrapped from the descending Arabian Plate. From the Late Cretaceous, a volcanic arc developed on the Eurasia margin as the Neotethys crust was subducted beneath it. A separate intra-oceanic subduction zone in the Neotethys resulted in the obuction of ocean crust onto the Arabian margin in the Late Cretaceous to Paleocene, with break-off of

6240-498: The Neotethys Ocean lying between it and southern Eurasia. Debate about the amount of deformation seen in the geological record in the India–Eurasia collision zone versus the size of Greater India, the timing and nature of the collision relative to the decrease in plate velocity, and explanations for the unusually high velocity of the Indian plate have led to several models for Greater India: 1) A Late Cretaceous to early Paleocene subduction zone may have lain between India and Eurasia in

6370-467: The Neotethys, dividing the region into two plates, subduction was followed by collision of India with Eurasia in the middle Eocene. In this model Greater India would have been less than 900 km wide; 2) Greater India may have formed a single plate, several thousand kilometres wide, with the Tethyan Himalaya microcontinent separated from the Indian continent by an oceanic basin . The microcontinent collided with southern Eurasia c. 58 Ma (late Paleocene), whilst

6500-418: The North American subduction zone near Baja California leading to major strike-slip movements and the formation of the San Andreas Fault . At the Paleogene-Neogene boundary, spreading ceased between the Pacific and Farallon plates and the Farallon Plate split again forming the present date Nazca and Cocos plates. The Kula Plate lay between Pacific Plate and North America. To the north and northwest it

6630-417: The North Atlantic Igneous Province, between about 56 and 54 Ma, which rapidly released large amounts of greenhouse gases into the atmosphere. This warming led to melting of frozen methane hydrates on continental slopes adding further greenhouses gases. It also reduced the rate of burial of organic matter as higher temperatures accelerated the rate of bacterial decomposition which released CO 2 back into

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6760-416: The Ocala Lower-Permeability Zone, and the Avon Park Permeable Zone. The base of the Upper Floridan aquifer is marked by two composite units (see below) and one confining unit in the middle part of the Floridan aquifer system: the Lisbon-Avon Park Composite Unit or the Middle Avon Park Composite Unit, and the Bucatunna Clay Confining Unit. In updip areas, the base of the Upper Floridan is either coincident with

6890-409: The Oligocene. The Paleogene is divided into three series / epochs : the Paleocene, Eocene, and Oligocene. These stratigraphic units can be defined globally or regionally. For global stratigraphic correlation, the International Commission on Stratigraphy (ICS) ratify global stages based on a Global Boundary Stratotype Section and Point (GSSP) from a single formation (a stratotype ) identifying

7020-524: The Pacific Plate moved north. At c. 47 Ma, movement of the hotspot ceased and the Pacific Plate motion changed from northward to northwestward in response to the onset of subduction along its western margin. This resulted in a 60 degree bend in the seamount chain. Other seamount chains related to hotspots in the South Pacific show a similar change in orientation at this time. Slow seafloor spreading continued between Australia and East Antarctica. Shallow water channels probably developed south of Tasmania opening

7150-441: The Pacific, Farallon, Kula and Izanagi plates. The central Pacific Plate grew by seafloor spreading as the other three plates were subducted and broken up. In the southern Pacific, seafloor spreading continued from the Late Cretaceous across the Pacific–Antarctic, Pacific-Farallon and Farallon–Antarctic mid ocean ridges. The Izanagi-Pacific spreading ridge lay nearly parallel to the East Asian subduction zone and between 60–50 Ma

7280-459: The Paleogene, and lasted from 33.9 Ma to 23.03 Ma. It is divided into two stages: the Rupelian 33.9 Ma to 27.82 Ma; and, Chattian 27.82 - 23.03 Ma. The GSSP for the base of the Oligocene is at Massignano , near Ancona , Italy . The extinction the hantkeninid planktonic foraminifera is the key marker for the Eocene-Oligocene boundary, which was a time of climate cooling that led to widespread changes in fauna and flora. The final stages of

7410-413: The Upper and Lower Floridan aquifers. The Upper Floridan aquifer is the main source of water withdrawn from the Floridan aquifer system due to high yields and proximity to land surface. Groundwater in the Upper Floridan is fresh in most areas, though locally may be brackish or saline, particularly in coastal areas with saltwater intrusion problems, and in South Florida. The Upper Floridan aquifer includes

7540-489: The Upper and Lower Floridan aquifers. Withdrawals from the Floridan aquifer system began in 1887 when the City of Savannah, Georgia , began to supplement surface water withdrawals from the Savannah River with groundwater. At that time artesian heads in the system were 40 feet (12 m) above land surface and no pumps were needed; by 1898, it was estimated that between 200 and 300 wells had been finished in South Georgia, and by 1943, about 3,500 wells had been completed in

7670-473: The aquifer drop. Dover Sinkhole, located along the Peace River near Bartow, FL , was witnessed draining about 10 Mgal/d (38,000 m/d) of water from the Peace River during June 2006. There are 824 springs inventoried across the Floridan aquifer system of which 751 are located in Florida, 17 in Alabama, and 56 in Georgia. Springs are classified according to median value of all available discharge measurements. In Florida, there are 33 magnitude 1 springs,

7800-419: The aquifer in its unconfined areas, and the interaction between fresh and saline water along the coastlines. Where the Floridan aquifer system is at or near land surface (areas shaded brown in image above), clays are thin or absent and dissolution of the limestone is intensified and many springs and sinkholes are apparent. Transmissivity of the aquifer in karstified areas such as these is much higher owing to

7930-425: The aquifer system is either unconfined or thinly confined. In areas where the aquifer is thickly confined, Miller (1986) indicated lower transmissivity was related primarily to textural changes and secondarily to the thickness of the rocks. Micritic limestone in southern Florida and in the updip outcrop areas was identified as having much lower transmissivity than elsewhere in the system. Sinkholes are common where

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8060-423: The base of the Eocene is at Dababiya, near Luxor , Egypt and is marked by the start of a significant variation in global carbon isotope ratios, produced by a major period of global warming. The change in climate was due to a rapid release of frozen methane clathrates from seafloor sediments at the beginning of the Paleocene-Eocene thermal maximum (PETM). The Oligocene is the third and youngest series/epoch of

8190-428: The base of the Floridan aquifer system. The Floridan aquifer system ranges in thickness from less than 100 feet (30 m) in updip areas where the rocks pinch out to more than 3,700 feet (1,100 m) in southwestern Florida. Recharge, flow, and natural discharge in the Floridan aquifer system are largely controlled by the degree of confinement provided by upper confining units, the interaction of streams and rivers with

8320-412: The base of the Upper Floridan aquifer is coincident with the top of the evaporite unit. In regions where no distinct lower permeability unit is known to be present, the base of the Upper Floridan is extrapolated along a horizon that allows for a stratigraphic grouping of permeable rock into the upper or lower parts of the aquifer system. In southeastern Alabama, northern Florida, Georgia, and South Carolina,

8450-449: The base of the system in central Florida and in updip areas of central and southern Georgia and Alabama. A new basal permeable zone is mapped throughout the Florida peninsula, and slightly into southeastern Georgia, that incorporates the previously established Boulder Zone and Fernandina permeable zone; this more extensive unit is called the Oldsmar permeable zone. The Oldsmar permeable zone appears to have higher permeability, far greater than

8580-511: The bedrock. The carbonic acid that causes karst features is formed as rain passes through Earth's atmosphere picking up carbon dioxide (CO 2 ), which readily dissolves in the water. Once the rain reaches the ground, it may pass through soil that provides additional CO 2 produced by soil respiration . Some of the dissolved carbon dioxide reacts with the water to form a weak carbonic acid solution, which dissolves calcium carbonate . The primary reaction sequence in limestone dissolution

8710-425: The breakup of Pangaea occurred during the Paleogene as Atlantic Ocean rifting and seafloor spreading extended northwards, separating the North America and Eurasian plates, and Australia and South America rifted from Antarctica , opening the Southern Ocean . Africa and India collided with Eurasia forming the Alpine-Himalayan mountain chains and the western margin of the Pacific Plate changed from

8840-430: The brief interruption of the Latest Danian Event (c. 62.2 Ma) when global temperatures rose. There is no evidence for ice sheets at the poles during the Paleocene. The relatively cool conditions were brought to an end by the Thanetian Thermal Event, and the beginning of the PETM. This was one of the warmest times of the Phanerozoic eon, during which global mean surface temperatures increased to 31.6 °C. According to

8970-472: The cavernous areas of the Boulder and Fernandina permeable zones, and contains freshwater in the central peninsula area. This newly delineated areally extensive basal unit containing freshwater may influence the movement of freshwater water through the deepest part of the aquifer system toward the discharge areas. The Oldsmar permeable zone, which is part of the Lower Floridan aquifer, is of interest because it may be an important alternative source of water where it

9100-406: The cold circumpolar current. Dense polar waters sank into the deep oceans and moved northwards, reducing global ocean temperatures. This cooling may have occurred over less than 100,000 years and resulted in a widespread extinction in marine life. By the Eocene-Oligocene boundary, sediments deposited in the ocean from glaciers indicate the presence of an ice sheet in western Antarctica that extended to

9230-418: The collision of the Tethyan (Tibetan) Himalayas , the leading edge of Greater India, with the Lhasa Terrane of Tibet (southern Eurasian margin), along the Indus-Yarling-Zangbo suture zone . To the south of this zone, the Himalaya are composed of metasedimentary rocks scraped off the now subducted Indian continental crust and mantle lithosphere as the collision progressed. Palaeomagnetic data place

9360-450: The complexity of karst aquifers, and need to be supplemented with dye traces , measurement of spring discharges, and analysis of water chemistry. U.S. Geological Survey dye tracing has determined that conventional groundwater models that assume a uniform distribution of porosity are not applicable for karst aquifers. Linear alignment of surface features such as straight stream segments and sinkholes develop along fracture traces . Locating

9490-480: The cooler oceans also reduced moisture in the atmosphere and increased aridity. By the early Oligocene, the North American and Eurasian tropical and subtropical forests were replaced by dry woodlands and widespread grasslands. The Early Oligocene Glacial Maximum lasted for about 200,000 years, and the global mean surface temperature continued to decrease gradually during the Rupelian . A drop in global sea levels during

9620-685: The crater are found at Chicxulub on the Yucatan Peninsula in Mexico . The extinction of the non-avian dinosaurs , ammonites and dramatic changes in marine plankton and many other groups of organisms, are also used for correlation purposes. The Eocene is the second series/epoch of the Paleogene, and lasted from 56.0 Ma to 33.9 Ma. It is divided into four stages: the Ypresian 56.0 Ma to 47.8 Ma; Lutetian 47.8 Ma to 41.2 Ma; Bartonian 41.2 Ma to 37.71 Ma; and, Priabonian 37.71 Ma to 33.9 Ma. The GSSP for

9750-592: The development of large, well-connected conduits within the rock (see image at right). Springs form where the water pressure is great enough for the groundwater to flow out on the land surface. More than 700 springs have been mapped in Florida. Wakulla Springs in Wakulla County is one of a number of major outflows of the aquifer with a flow rate of 200–300 million US gallons (0.76–1.14 million cubic metres; 610–920 acre-feet) of water per day. A record peak flow from

9880-590: The disruption of the Chicxulub impact settled, a period of cool and dry conditions continued from the Late Cretaceous. At the Paleocene-Eocene boundary global temperatures rose rapidly with the onset of the Paleocene-Eocene Thermal Maximum (PETM). By the middle Eocene, temperatures began to drop again and by the late Eocene (c. 37 Ma) had decreased sufficiently for ice sheets to form in Antarctica. The global climate entered icehouse conditions at

10010-662: The early Eocene (c. 54 Ma), into the northeastern Atlantic between Greenland and Eurasia. Extension between North America and Eurasia, also in the early Eocene, led to the opening of the Eurasian Basin across the Arctic, which was linked to the Baffin Bay Ridge and Mid-Atlantic Ridge to the south via major strike slip faults. From the Eocene and into the early Oligocene, Greenland acted as an independent plate moving northwards and rotating anticlockwise. This led to compression across

10140-461: The early Oligocene, flood basalts erupted across Ethiopia , northeast Sudan and southwest Yemen as the Afar mantle plume began to impact the base of the African lithosphere. Rifting across the southern Red Sea began in the mid Oligocene, and across the central and northern Red Sea regions in the late Oligocene and early Miocene. Climatic conditions varied considerably during the Paleogene. After

10270-532: The end of the Cretaceous but saw a very rapid radiation into their modern order and family-level diversity during the Paleogene, achieving a diverse array of morphologies. The Paleogene is marked by considerable changes in climate from the Paleocene–Eocene Thermal Maximum , through global cooling during the Eocene to the first appearance of permanent ice sheets in the Antarctic at the beginning of

10400-586: The existence of the Floridan Aquifer in peninsular Florida and referred to the carbonate units as the "principal artesian formations." In 1944, M.A. Warren of the Georgia Geological Survey described an extension of this system in south Georgia and applied the term "principal artesian aquifer " to the carbonate units involved. In 1953 and 1966 Stringfield also applied the term "principal artesian aquifer" to these rocks. In 1955, Garald G. Parker noted

10530-557: The fissures. The enlarged fissures allow a larger quantity of water to enter which leads to a progressive enlargement of openings. Abundant small openings store a large quantity of water. The larger openings form a conduit system that drains the aquifer to springs. Characterization of karst aquifers requires field exploration to locate sinkholes, swallets , sinking streams , and springs in addition to studying geologic maps . Conventional hydrogeologic methods such as aquifer tests and potentiometric mapping are insufficient to characterize

10660-466: The global demand for drinkable water. Farming in karst areas must take into account the lack of surface water. The soils may be fertile enough, and rainfall may be adequate, but rainwater quickly moves through the crevices into the ground, sometimes leaving the surface soil parched between rains. The karst topography also poses peculiar difficulties for human inhabitants. Sinkholes can develop gradually as surface openings enlarge, but progressive erosion

10790-456: The karst groundwater flow rates from 0.5 to 7 miles per day (0.8 to 11.3 km/d). The rapid groundwater flow rates make karst aquifers much more sensitive to groundwater contamination than porous aquifers. Groundwater in karst areas is also just as easily polluted as surface streams, because Karst formations are cavernous and highly permeable, resulting in reduced opportunity for contaminant filtration. Well water may also be unsafe as

10920-525: The karst regions of the Balkans, Cvijić's 1893 publication Das Karstphänomen describes landforms such as karren, dolines and poljes . In a 1918 publication, Cvijić proposed a cyclical model for karst landscape development. Karst hydrology emerged as a discipline in the late 1950s and the early 1960s in France. Previously, the activities of cave explorers, called speleologists , had been dismissed as more of

11050-492: The land surface to the south where it becomes buried beneath surficial sand deposits and clay. In areas depicted in brown in the image at the right, the Floridan aquifer system crops out and is again exposed at land surface. These regions are particularly prone to sinkhole activity due to the proximity of the karstified limestone aquifer to land surface. Some of the fractures/conduits within the aquifer are large enough for scuba divers to swim through. The carbonate rocks that form

11180-552: The last-named locality having been declared a site of special scientific interest in respect of it. Kegelkarst is a type of tropical karst terrain with numerous cone-like hills, formed by cockpits, mogotes , and poljes and without strong fluvial erosion processes. This terrain is found in Cuba, Jamaica, Indonesia, Malaysia, the Philippines, Puerto Rico, southern China, Myanmar, Thailand, Laos and Vietnam. Salt karst (or 'halite karst')

11310-509: The late Eocene (c. 37 Ma) there is evidence of glaciation in Antarctica. Changes in deep ocean currents, as Australia and South America moved away from Antarctica opening the Drake and Tasmanian passages, were responsible for the drop in global temperatures. The warm waters of the South Atlantic, Indian and South Pacific oceans extended southward into the opening Southern Ocean and became part of

11440-468: The leading northeastern edge of Greater India collided with the West Burma block resulting in deformation and metamorphism . During the middle Eocene, north-dipping subduction resumed along the southern edge of Southeast Asia, from west Sumatra to West Sulawesi, as the Australian Plate drifted slowly northwards. Collision between India and the West Burma block was complete by the late Oligocene. As

11570-412: The local South Slavic languages , all variations of the word are derived from a Romanized Illyrian base (yielding Latin : carsus , Dalmatian : carsus ), later metathesized from the reconstructed form * korsъ into forms such as Slovene : kras and Serbo-Croatian : krš , kras , first attested in the 18th century, and the adjective form kraški in the 16th century. As

11700-539: The lower boundary of the stage. The Paleocene is the first series/epoch of the Paleogene and lasted from 66.0 Ma to 56.0 Ma. It is divided into three stages: the Danian 66.0 - 61.6 Ma; Selandian 61.6 - 59.2 Ma; and, Thanetian 59.2 - 56.0 Ma. The GSSP for the base of the Cenozoic, Paleogene and Paleocene is at Oued Djerfane, west of El Kef , Tunisia . It is marked by an iridium anomaly produced by an asteroid impact, and

11830-425: The magnitude of discharge from these springs is largely unknown. Crescent Beach spring, located approximately 2.5 miles (4.0 km) offshore of Crescent Beach, Florida, was estimated to flow at a rate of up to 1,500 cu ft/s (42 m/s), or 970 million US gal/d (3.7 million m/d; 3,000 acre⋅ft/d). Paleogene Much of the world's modern vertebrate diversity originated in

11960-502: The majority of values ranging from 10,000 to 100,000 ft/d (930–9,290 m/d). Where the aquifer is unconfined or thinly confined, infiltrating water dissolves the rock and transmissivity tends to be relatively high. Where the aquifer is thickly confined, less dissolution occurs and transmissivity tends to be lower. In the first regional map depicting transmissivity variation across the aquifer, Miller (1986) showed that transmissivity values exceed 250,000 ft/d (23,000 m/d) where

12090-493: The mid Oligocene indicates major growth of the Antarctic glacial ice sheet. In the Late Oligocene , global temperatures began to warm slightly, though they continued to be significantly lower than during the previous epochs of the Paleogene and polar ice remained. Karst Karst ( / k ɑːr s t / ) is a topography formed from the dissolution of soluble carbonate rocks such as limestone and dolomite . It

12220-597: The more notable of which include: In Georgia, there is only one magnitude 1 spring, Radium Spring , which no longer flows during drought conditions; there are also six magnitude 2 and five magnitude 3 springs. The largest of the 17 springs in Alabama are three magnitude 3 springs; there are no springs in South Carolina of magnitude 3 or higher. Many springs are known to exist offshore in the Gulf of Mexico and Atlantic Ocean, however

12350-637: The most dramatic of these formations can be seen in Thailand 's Phangnga Bay and at Halong Bay in Vietnam . Calcium carbonate dissolved into water may precipitate out where the water discharges some of its dissolved carbon dioxide. Rivers which emerge from springs may produce tufa terraces, consisting of layers of calcite deposited over extended periods of time. In caves, a variety of features collectively called speleothems are formed by deposition of calcium carbonate and other dissolved minerals. Interstratal karst

12480-579: The northeast Atlantic. By the late Oligocene, the plate boundary between North America and Eurasia was established along the Mid-Atlantic Ridge, with Greenland attached to the North American plate again, and the Jan Mayen microcontinent part of the Eurasian Plate, where its remains now lie to the east and possibly beneath the southeast of Iceland. The North Atlantic Igneous Province stretches across

12610-619: The ocean. The development of the circumpolar current led to changes in the oceans, which in turn reduced atmospheric CO 2 further. Increasing upwellings of cold water stimulated the productivity of phytoplankton , and the cooler waters reduced the rate of bacterial decay of organic matter and promoted the growth of methane hydrates in marine sediments. This created a positive feedback cycle where global cooling reduced atmospheric CO 2 and this reduction in CO 2 lead to changes which further lowered global temperatures. The decrease in evaporation from

12740-470: The oceans. The (relatively) sudden climatic changes associated with the PETM resulted in the extinction of some groups of fauna and flora and the rise of others. For example, with the warming of the Arctic Ocean, around 70% of deep sea foraminifera species went extinct, whilst on land many modern mammals, including primates , appeared. Fluctuating sea levels meant, during low stands, a land bridge formed across

12870-414: The panhandle (Bucatunna Clay) and low-permeability dolomites and gypsiferous anhydrite in west-central Florida to permeable limestones along the east coast of Florida and elsewhere. Where these intervening sediments and rock are permeable, the Upper and Lower Floridan aquifers behave as a single unit. Conversely, where the intervening sediments are less permeable, there is less hydraulic connection between

13000-704: The period. Sedimentation resumed and further limestone strata were deposited on an irregular karst surface, the cycle recurring several times in connection with fluctuating sea levels over prolonged periods. Pseudokarsts are similar in form or appearance to karst features but are created by different mechanisms. Examples include lava caves and granite tors —for example, Labertouche Cave in Victoria, Australia —and paleocollapse features. Mud Caves are an example of pseudokarst. Karst formations have unique hydrology, resulting in many unusual features. A karst fenster (karst window) occurs when an underground stream emerges onto

13130-454: The present day Indian continent further south at the time of collision and decrease in plate velocity, indicating the presence of a large region to the north of India that has now been subducted beneath the Eurasian Plate or incorporated into the mountain belt. This region, known as Greater India, formed by extension along the northern margin of India during the opening of the Neotethys. The Tethyan Himalaya block lay along its northern edge, with

13260-399: The proto-Iceland plume has been considered the driving mechanism for rifting in the North Atlantic. However, that rifting and initial seafloor spreading occurred prior to the arrival of the plume, large scale magmatism occurred at a distance to rifting, and that rifting propagated towards, rather than away from the plume, has led to the suggestion the plume and associated magmatism may have been

13390-757: The river flows into a cave in a formation known as the Madison Limestone and then rises again 800 m ( 1 ⁄ 2  mi) down the canyon in a placid pool. A turlough is a unique type of seasonal lake found in Irish karst areas which are formed through the annual welling-up of water from the underground water system. Main Article Aquifer#Karst Karst aquifers typically develop in limestone . Surface water containing natural carbonic acid moves down into small fissures in limestone. This carbonic acid gradually dissolves limestone thereby enlarging

13520-401: The rock below the land surface is limestone, carbonate rock, salt beds, or rocks that can naturally be dissolved by groundwater circulating through them. As the rock dissolves, spaces and caverns develop underground. If there is not enough support for the land above the spaces then a sudden collapse of the land surface can occur. These collapses can be small or they can be huge and can occur where

13650-457: The six coastal counties of Georgia. By around 1910–1912, development of the Floridan aquifer system had already occurred in Fernandina and Jacksonville and south along the east coast of Florida, as well as from Tampa south to Fort Myers on the west coast. Over time, the number of wells increased, as did the finished depths, as demand increased. Industrial supply for pulp and paper mills became

13780-461: The southeastern United States and underlies all of Florida and parts of southern Alabama, southeastern Georgia, and southern South Carolina. The Upper Floridan aquifer contains freshwater over much of its extent, though is brackish and saline south of Lake Okeechobee. The Floridan aquifer system crops out in central and southern Georgia where the limestone, and its weathered byproducts, are present at land surface. The aquifer system generally dips below

13910-659: The southwest, an island arc collided with the northern Andes forming an east dipping subduction zone where Caribbean lithosphere was subducted beneath the South American margin. During the Eocene (c. 45 Ma), subduction of the Farallon Plate along the Central American subduction zone was (re)established. Subduction along the northern section of the Caribbean volcanic arc ceased as the Bahamas carbonate platform collided with Cuba and

14040-520: The spreading ridge began to be subducted. By c. 50 Ma, the Pacific Plate was no longer surrounded by spreading ridges, but had a subduction zone along its western edge. This changed the forces acting on the Pacific Plate and led to a major reorganisation of plate motions across the entire Pacific region. The resulting changes in stress between the Pacific and Philippine Sea plates initiated subduction along

14170-415: The spring on April 11, 1973, was measured at 14,324 US gallons (54.22 m) per second – equal to 1.24 billion US gal (4.68 million m; 3,800 acre⋅ft) per day. The Floridan aquifer system is composed of two main aquifers : the Upper Floridan aquifer and the Lower Floridan aquifer. These aquifers are separated by sediments that range from low-permeability clays in

14300-491: The stratigraphic units are grouped into the Lisbon-Avon Park Composite Unit. In peninsular Florida, this horizon is coincident with one or more evaporite-bearing or non-evaporite-bearing units of the Middle Avon Park Composite Unit. In the panhandle of Florida and southwest Alabama, the base is coincident with the top of the Bucatunna Clay Confining Unit. The hydrogeologic framework of the Floridan aquifer system

14430-524: The subducted oceanic plate close to the Arabian margin occurring during the Eocene. Continental collision began during the Eocene c. 35 Ma and continued into the Oligocene to c. 26 Ma. The Indian continent rifted from Madagascar at c. 83 Ma and drifted rapidly (c. 18 cm/yr in the Paleocene) northwards towards the southern margin of Eurasia. A rapid decrease in velocity to c. 5 cm/yr in the early Eocene records

14560-527: The subducting Farallon Plate led to a flat-slab segment that increased friction between this and the base of the North American Plate. The resulting Laramide Orogeny , which began the development of the Rocky Mountains , was a broad zone of thick-skinned deformation , with faults extending to mid-crustal depths and the uplift of basement rocks that lay to the east of the Sevier belt, and more than 700km from

14690-625: The surface between layers of rock, cascades some distance, and then disappears back down, often into a sinkhole. Rivers in karst areas may disappear underground a number of times and spring up again in different places, even under a different name, like Ljubljanica , the "river of seven names". Another example of this is the Popo Agie River in Fremont County, Wyoming , where, at a site named "The Sinks" in Sinks Canyon State Park ,

14820-415: The surface, complex underground drainage systems (such as karst aquifers ) and extensive caves and cavern systems may form. Erosion along limestone shores, notably in the tropics , produces karst topography that includes a sharp makatea surface above the normal reach of the sea, and undercuts that are mostly the result of biological activity or bioerosion at or a little above mean sea level . Some of

14950-1002: The system ( pyrite or hydrogen sulfide ) to form sulfuric acid (H 2 SO 4 ). Sulfuric acid then reacts with calcium carbonate, causing increased erosion within the limestone formation. This chain of reactions is: This reaction chain forms gypsum . The karstification of a landscape may result in a variety of large- or small-scale features both on the surface and beneath. On exposed surfaces, small features may include solution flutes (or rillenkarren), runnels , limestone pavement (clints and grikes), kamenitzas collectively called karren or lapiez. Medium-sized surface features may include sinkholes or cenotes (closed basins), vertical shafts, foibe (inverted funnel shaped sinkholes), disappearing streams, and reappearing springs . Large-scale features may include limestone pavements , poljes , and karst valleys. Mature karst landscapes, where more bedrock has been removed than remains, may result in karst towers , or haystack/eggbox landscapes. Beneath

15080-474: The top of the confining units above the Claiborne, Lisbon, or Gordon aquifers, or it lies above any clay bed that marks the boundary between mostly carbonate and mostly clastic units or previously mapped numbered MCUs of Miller (1986). If one or more evaporite units are present, such as middle confining unit MCUIII near Valdosta in south-central Georgia (Miller, 1986) or MCUII in southwestern Florida (Miller, 1986),

15210-649: The trench. With the Laramide uplift the Western Interior Seaway was divided and then retreated. During the mid to late Eocene (50–35 Ma), plate convergence rates decreased and the dip of the Farallon slab began to steepen. Uplift ceased and the region largely levelled by erosion . By the Oligocene, convergence gave way to extension, rifting and widespread volcanism across the Laramide belt. Ocean-continent convergence accommodated by east dipping subduction zone of

15340-487: The upper confining unit are present and substantial, the system is confined and groundwater is contained under pressure. The upper confining unit is particularly thick in Coastal Georgia and South Florida; downward leakage of water through the upper confining unit in these areas is minimal and the Floridan aquifer system is thickly confined. Low permeability limestone rocks of Paleocene age (e.g. Cedar Keys Formation) form

15470-406: The uppermost or shallowest permeable zones in the Floridan aquifer system. In the northern half of the study area, this aquifer behaves as a single hydrogeologic unit and is undifferentiated. In the southern half of the study area, including most of central and southern Florida, the Upper Floridan aquifer is thick and can be differentiated into three distinct zones, namely the uppermost permeable zone,

15600-478: The velocity of the plate did not decrease until c. 50 Ma when subduction rates dropped as young, oceanic crust entered the subduction zone; 3) This model assigns older dates to parts of Greater India, which changes its paleogeographic position relative to Eurasia and creates a Greater India formed of extended continental crust 2000 - 3000 km wide. The Alpine-Himalayan Orogenic Belt in Southeast Asia extends from

15730-461: The water may have run unimpeded from a sinkhole in a cattle pasture, bypassing the normal filtering that occurs in a porous aquifer . Sinkholes have often been used as farmstead or community trash dumps . Overloaded or malfunctioning septic tanks in karst landscapes may dump raw sewage directly into underground channels. Geologists are concerned with these negative effects of human activity on karst hydrology which, as of 2007 , supplied about 25% of

15860-507: The western Highland Rim in the eastern United States is at the second-highest risk of karst sinkholes. In Canada, Wood Buffalo National Park , Northwest Territories contains areas of karst sinkholes. Mexico hosts important karst regions in the Yucatán Peninsula and Chiapas . The West of Ireland is home to The Burren , a karst limestone area. The South China Karst in the provinces of Guizhou , Guangxi , and Yunnan provinces

15990-513: The western Mediterranean arc of the Tell, Rif, Betic and Apennine mountain chains. The rate of convergence was less than the subduction rate of the dense lithosphere of the western Mediterranean and roll-back of the subducting slab led to the arcuate structure of these mountain ranges. In the eastern Mediterranean, c. 35 Ma, the Anatolide-Tauride platform (northern part of Adria) began to enter

16120-607: Was being subducted beneath the Aleutian trench . Spreading between the Kula and Pacific and Farallon plates ceased c. 40 Ma and the Kula Plate became part of the Pacific Plate. The Hawaiian-Emperor seamount chain formed above the Hawaiian hotspot . Originally thought to be stationary within the mantle, the hotspot is now considered to have drifted south during the Paleocene to early Eocene, as

16250-535: Was followed by a c.10 million year pause in the convergence of Africa and Eurasia, connected with the onset of the opening of the North Atlantic Ocean as Greenland rifted from the Eurasian Plate in the Palaeocene. Convergence rates between Africa and Eurasia increased again in the early Eocene and the remaining oceanic basins between Adria and Europe closed. Between about 40 and 30 Ma, subduction began along

16380-433: Was introduced to refer to regionally extensive litho-stratigraphic units of rock, previously classified as one of eight "Middle Confining Units" by Miller (1986), which have been found to be neither confining nor permeable across their entire extents. Three regionally mapable litho-stratigraphic units are used to consistently divide the Upper and Lower Floridan aquifer in the revised framework: the Bucatunna Clay Confining Unit,

16510-542: Was replaced by strike-slip movements as a transform fault, extending from the Mid-Atlantic Ridge, connected with the northern boundary of the Caribbean Plate. Subduction now focused along the southern Caribbean arc ( Lesser Antilles ). By the Oligocene, the intra-oceanic Central American volcanic arc began to collide with northwestern South American. At the beginning of the Paleogene, the Pacific Ocean consisted of

16640-491: Was revised by the U.S. Geological Survey in 2015. The extent of the system was revised to include some of the updip clastic facies which grade laterally into the Lower Floridan aquifer and have been previously included in the Southeastern Coastal Plain aquifer system, the Floridan aquifer system, or both. A new method for dividing the Upper and Lower Floridan aquifers was proposed and a new term, "composite unit",

16770-555: Was subducted southwards beneath the African Plate, whilst in the eastern Mediterranean, Africa was subducted beneath Eurasia along a northward dipping subduction zone. Convergence between the Iberian and European plates led to the Pyrenean Orogeny and, as Adria pushed northwards the Alps and Carpathian orogens began to develop. The collision of Adria with Eurasia in the early Palaeocene

16900-495: Was used for public water supply , 14% (576 Mgal/d, 2.18 million m/d; 1,770 acre⋅ft/d) was used for industrial purposes, and 4% were domestic self-supplied withdrawals. The Floridan aquifer system is the primary source of drinking water for most cities in central and northern Florida as well as eastern and southern Georgia, including Brunswick, Savannah, and Valdosta. In 1936, geologist Victor Timothy (V.T.) Stringfield first identified

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