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45-517: Situated on a low ridge of the Dorsale Mountains , the town has a mild climate and presents a green aspect. Cold water from here was taken by the Zaghouan Aqueduct to Carthage . The town is famous for its roses , originally cultivated by Muslim refugees from Spain in the seventeenth century. The town is located around 60 km due south of Tunis and around 50 km inland (west) from

90-495: A clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains, cemented together by another mineral. Sandstones comprise about 20–25% of all sedimentary rocks . Most sandstone is composed of quartz or feldspar , because they are the most resistant minerals to the weathering processes at the Earth's surface. Like uncemented sand , sandstone may be imparted any color by impurities within

135-470: A thin section using a method like the Gazzi-Dickinson Method . This yields the relative percentages of quartz, feldspar, and lithic grains and the amount of clay matrix. The composition of a sandstone can provide important information on the genesis of the sediments when used with a triangular Q uartz, F eldspar, L ithic fragment ( QFL diagrams ). However, geologist have not been able to agree on

180-439: A 4-metre-wide (13 ft), crescent-shaped portico. In the center of the portico is a cella from which the spring sprang. The outer wall had a core of Roman concrete covered with coarse limestone bossages . This wall continued from the ends of the crescent-shaped portico and was divided into 26 sections be engaged columns. In every second section, there is a niche for statues, which do not survive. Opposite each engaged column

225-478: A sandstone goes through as the degree of kinetic processing of the sediments increases. Dott's (1964) sandstone classification scheme is one of many such schemes used by geologists for classifying sandstones. Dott's scheme is a modification of Gilbert's classification of silicate sandstones, and it incorporates R.L. Folk's dual textural and compositional maturity concepts into one classification system. The philosophy behind combining Gilbert's and R. L. Folk's schemes

270-420: A second source was attached to the aqueduct. This was located in the region of Djouggar. A sacred fountain was built over this spring too, but it never reached the significance of the one at Zaghouan. The aqueduct is a masterpiece of Roman engineering. In the journey from Zaghouan to Carthage, it travels a little over 90 km and drops only 264 m in height, which is an average decline of 0.3%. However, 130 m of

315-459: A set of boundaries separating regions of the QFL triangle. Visual aids are diagrams that allow geologists to interpret different characteristics of a sandstone. For example, a QFL chart can be marked with a provenance model that shows the likely tectonic origin of sandstones with various compositions of framework grains. Likewise, the stage of textural maturity chart illustrates the different stages that

360-445: A twofold classification: Cement is what binds the siliciclastic framework grains together. Cement is a secondary mineral that forms after deposition and during burial of the sandstone. These cementing materials may be either silicate minerals or non-silicate minerals, such as calcite. Sandstone that becomes depleted of its cement binder through weathering gradually becomes friable and unstable. This process can be somewhat reversed by

405-837: Is a distinction that can be recognized in the field . In turn, the distinction between an orthoquartzite and a metaquartzite is the onset of recrystallization of existing grains. The dividing line may be placed at the point where strained quartz grains begin to be replaced by new, unstrained, small quartz grains, producing a mortar texture that can be identified in thin sections under a polarizing microscope. With increasing grade of metamorphism, further recrystallization produces foam texture , characterized by polygonal grains meeting at triple junctions, and then porphyroblastic texture , characterized by coarse, irregular grains, including some larger grains ( porphyroblasts .) Sandstone has been used since prehistoric times for construction, decorative art works and tools. It has been widely employed around

450-452: Is a full column, which together once supported a vaulted peristyle. The vaults are made of porous travertine covered in marble , while the columns are sandstone . The exterior of the vault was sealed with waterproof Opus signinum and left without further protection. The floor of the portico was decorated with mosaic . The cella, the most important part of the building was built from limestone and clad in marble. There were five springs in

495-523: Is likely formed during eogenesis. Deeper burial is accompanied by mesogenesis , during which most of the compaction and lithification takes place. Compaction takes place as the sand comes under increasing pressure from overlying sediments. Sediment grains move into more compact arrangements, ductile grains (such as mica grains) are deformed, and pore space is reduced. In addition to this physical compaction, chemical compaction may take place via pressure solution . Points of contact between grains are under

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540-457: Is located near the town of Zaghouan in the Djebel Zaghouan , a mountain range about 60 km south of Carthage. In Roman times a sacred fountain structure was built over the spring, which became one of the most important in ancient North Africa. The sacred fountain is located on an artificial terrace. It is open on the north side, and on the southern side there is an open space enclosed by

585-720: Is meant to have come to an end. The water shortage resulting from the drought might have convinced him that the people should not rely only on rainwater anymore. A second event that might have inspired it was the opening of the Baths of Antonius in Carthage in 162. These facilities on the same scale as the Imperial baths in Rome demanded a steady supply of water, which could not be fulfilled with rainwater. The aqueduct draws on several sources which ran dry at different times. The first and most important source

630-431: Is redeposited in the unstrained pore spaces. Mechanical compaction takes place primarily at depths less than 1,000 meters (3,300 ft). Chemical compaction continues to depths of 2,000 meters (6,600 ft), and most cementation takes place at depths of 2,000–5,000 meters (6,600–16,400 ft). Unroofing of buried sandstone is accompanied by telogenesis , the third and final stage of diagenesis. As erosion reduces

675-443: Is that it is better able to "portray the continuous nature of textural variation from mudstone to arenite and from stable to unstable grain composition". Dott's classification scheme is based on the mineralogy of framework grains, and on the type of matrix present in between the framework grains. In this specific classification scheme, Dott has set the boundary between arenite and wackes at 15% matrix. In addition, Dott also breaks up

720-572: The Arabs in 698, but each time it was subsequently restored. In the thirteenth century, one of the Hafsid rulers added a branch leading to his palace in Manouba in order to supply water for his garden. From the sixteenth century, the aqueduct deteriorated rapidly and was employed as a stone quarry. In 1859 a French engineer received the task of restoring the water channel in order to supply Tunis with water. While

765-667: The Gulf of Hammamet and has an estimated population of around 20,837 (2014). It is the capital of the Zaghouan Governorate . On the mountain south of the city is the Roman Water Temple Djebel Zaghouan (Temple de Eaux), source of an aqueduct which used to take water to the city of Carthage over 100 km away. The ruins here are illustrated in Fisher's Drawing Room Scrap Book, 1840, as 'Temple and Fountain of Zagwhan',

810-513: The lesser kestrel Falco naumanni (30 pairs), but also by the Lanner falcon Falco biarmicus and the common kestrel Falco tinnunculus as well as the European roller Coracias garrulus , rock sparrows Petronia petronia , spotless starlings Sturnus unicolor and common ravens Corvus corax . The site is of particular significance for the lesser krestel as it regularly holds significant numbers

855-498: The percolation of water and other fluids and are porous enough to store large quantities, making them valuable aquifers and petroleum reservoirs . Quartz-bearing sandstone can be changed into quartzite through metamorphism , usually related to tectonic compression within orogenic belts . Sandstones are clastic in origin (as opposed to either organic , like chalk and coal , or chemical , like gypsum and jasper ). The silicate sand grains from which they form are

900-560: The Baths of Antonius. The construction date is unknown, but modifications have been detected in connection with the construction of the Baths of Antonius, implying that the cistern preceded the baths. Since the water supply was essential for the city, the aqueduct was destroyed during the Vandal siege of 439, the Eastern Roman reconquest under Justinian and finally at the conquest of Carthage by

945-491: The application of tetraethyl orthosilicate (Si(OC 2 H 5 ) 4 ) which will deposit amorphous silicon dioxide between the sand grains. The reaction is as follows. Pore space includes the open spaces within a rock or a soil. The pore space in a rock has a direct relationship to the porosity and permeability of the rock. The porosity and permeability are directly influenced by the way the sand grains are packed together. Sandstones are typically classified by point-counting

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990-407: The area of the sacred fountain. These were in the area of the artificial terrace in their original, underground bed and gathered in a basin under the terrace. From this basin, the water then flowed into the pipe of the aqueduct. As well as feeding the aqueduct intake, the basin also served to clean the water - while the water sat in the basin, impurities would settle on the bottom. In Severan times,

1035-436: The channel follows the contours of hills. In three places it was not possible for the channel to remain at ground level, so the engineers erected imposing arcades . They are: In cross-section, the channel measures about 90 cm in width and 130 cm in height. It was closed on top by a vault. The walls were made from Roman cement and were clad with sandstone bossage. The part of the channel which came in contact with water

1080-468: The common minerals most resistant to weathering processes at the Earth's surface, as seen in the Goldich dissolution series . Framework grains can be classified into several different categories based on their mineral composition: Matrix is very fine material, which is present within interstitial pore space between the framework grains. The nature of the matrix within the interstitial pore space results in

1125-456: The depositional environment, older sand is buried by younger sediments, and it undergoes diagenesis . This mostly consists of compaction and lithification of the sand. Early stages of diagenesis, described as eogenesis , take place at shallow depths (a few tens of meters) and are characterized by bioturbation and mineralogical changes in the sands, with only slight compaction. The red hematite that gives red bed sandstones their color

1170-407: The depth of burial, renewed exposure to meteoric water produces additional changes to the sandstone, such as dissolution of some of the cement to produce secondary porosity . Framework grains are sand-sized (0.0625-to-2-millimeter (0.00246 to 0.07874 in) diameter) detrital fragments that make up the bulk of a sandstone. Most framework grains are composed of quartz or feldspar , which are

1215-446: The different types of framework grains that can be present in a sandstone into three major categories: quartz, feldspar, and lithic grains. When sandstone is subjected to the great heat and pressure associated with regional metamorphism , the individual quartz grains recrystallize, along with the former cementing material, to form the metamorphic rock called quartzite . Most or all of the original texture and sedimentary structures of

1260-433: The greatest strain, and the strained mineral is more soluble than the rest of the grain. As a result, the contact points are dissolved away, allowing the grains to come into closer contact. Lithification follows closely on compaction, as increased temperatures at depth hasten deposition of cement that binds the grains together. Pressure solution contributes to cementing, as the mineral dissolved from strained contact points

1305-442: The hardness of individual grains, uniformity of grain size and friability of their structure, some types of sandstone are excellent materials from which to make grindstones , for sharpening blades and other implements. Non-friable sandstone can be used to make grindstones for grinding grain, e.g., gritstone . A type of pure quartz sandstone, orthoquartzite, with more of 90–95 percent of quartz, has been proposed for nomination to

1350-545: The height difference occurs in the first 6 km from Zaghouan to Moghrane. For the rest of the journey to Carthage, the decline averages only 0.15%. In Moghrane the aqueduct met the later channel coming from Djouggar, another 33 km away. Including all its tributary channels, the aqueduct has a length of 132 km and is among the longest in the Roman empire. The channel discharged between 200 and 370 L of water per second or between 17 and 32 million liters per day. The flow rate

1395-521: The longest aqueducts in the Roman Empire . Some of its length (40 ha area) is also classified as an Important Bird Area (TN013) as the cavities and holes in the aqueduct are used as nesting and roosting sites for falcons and other species. The date of the construction of the aqueduct is not entirely clear. Sources mention a visit by the Emperor Hadrian in 128, with which a five-year-long drought

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1440-416: The majority of the channels at ground level could be reused, the parts of the channel on pillars were mostly destroyed and a modern pressure pipe system was installed. Since it was put into operation in 1862, the channel has remained in use and today it supplies an average of 12,000,000 L per day in winter and 3,000,000 in summer. The cavities and holes in the aqueduct are used as nesting and roosting sites by

1485-483: The minerals, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black. Because sandstone beds can form highly visible cliffs and other topographic features, certain colors of sandstone have become strongly identified with certain regions, such as the red rock deserts of Arches National Park and other areas of the American Southwest . Rock formations composed of sandstone usually allow

1530-493: The much lower temperatures and pressures associated with diagenesis of sedimentary rock, but diagenesis has cemented the rock so thoroughly that microscopic examination is necessary to distinguish it from metamorphic quartzite. The term orthoquartzite is used to distinguish such sedimentary rock from metaquartzite produced by metamorphism. By extension, the term orthoquartzite has occasionally been more generally applied to any quartz-cemented quartz arenite . Orthoquartzite (in

1575-464: The narrow sense) is often 99% SiO 2 with only very minor amounts of iron oxide and trace resistant minerals such as zircon , rutile and magnetite . Although few fossils are normally present, the original texture and sedimentary structures are preserved. The typical distinction between a true orthoquartzite and an ordinary quartz sandstone is that an orthoquartzite is so highly cemented that it will fracture across grains, not around them. This

1620-413: The nature of the mortar , they are dated to the first century AD. It is not yet clear how these cisterns were used in that period, since the aqueduct had not yet been built and this enormous volume could never have been filled by rainwater alone. The cistern of Bordj Djedid is made up of 18 barrel-shaped basins arranged in parallel and held between 25 and 30 million liters. It was responsible for supplying

1665-556: The painting being by Sir Greenville Temple with a poetical illustration by Letitia Elizabeth Landon . Zagwan is the presumed site of the Ancient city of Zica (or Ziqva). The city was among the many of sufficient importance in the Roman province of Africa Proconsularis to become a suffragan diocese of the Metropolitan of Carthage , in the papal sway, yet was to fade completely, probably at

1710-638: The product of physical and chemical weathering of bedrock. Weathering and erosion are most rapid in areas of high relief, such as volcanic arcs , areas of continental rifting , and orogenic belts . Eroded sand is transported by rivers or by the wind from its source areas to depositional environments where tectonics has created accommodation space for sediments to accumulate. Forearc basins tend to accumulate sand rich in lithic grains and plagioclase . Intracontinental basins and grabens along continental margins are also common environments for deposition of sand. As sediments continue to accumulate in

1755-417: The sandstone are erased by the metamorphism. The grains are so tightly interlocked that when the rock is broken, it fractures through the grains to form an irregular or conchoidal fracture. Geologists had recognized by 1941 that some rocks show the macroscopic characteristics of quartzite, even though they have not undergone metamorphism at high pressure and temperature. These rocks have been subject only to

1800-483: The seventh century advent of Islam. Its historically documented bishops were : This Tunisia location article is a stub . You can help Misplaced Pages by expanding it . Zaghouan Aqueduct The Zaghouan Aqueduct or Aqueduct of Carthage is an ancient Roman aqueduct , which supplied the city of Carthage , Tunisia with water. From its source in Zaghouan it flows a total of 132 km, making it among

1845-452: The species, (which is a species of global conservation concern). The protected area extends over 40 ha as a band stretching near the Milliana river along the aqueduct 20-m-high pillars and arches in which many cavities and holes used by birds have developed. The surrounding area consists of cereal fields and is a hunting reserve. General Specific Sandstone Sandstone is

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1890-409: The water within Carthage is not yet entirely clear. It seems that the channel discharged into two cisterns and the water was further distributed from these. To date, however, archaeological excavations have found no sure signs of discharge into the cisterns. The cisterns of La Malga form the largest cisterns surviving from the ancient world anywhere. They held approximately 51 million liters. Based on

1935-612: The world in constructing temples, churches, homes and other buildings, and in civil engineering . Although its resistance to weathering varies, sandstone is easy to work. That makes it a common building and paving material, including in asphalt concrete . However, some types that have been used in the past, such as the Collyhurst sandstone used in North West England , have had poor long-term weather resistance, necessitating repair and replacement in older buildings. Because of

1980-454: Was around 3.5 and 5.5 km per hour. Therefore, the water made the journey from Zaghouan to Carthage in between a day and a half, to two days. The channel was built such that it had a steady, if not uniform, fall so that the water would travel the route by the force of gravity alone. In order to minimize the building work, the channel was laid on or a little under the Earth's surface where possible. In order to avoid unnecessary loss of height,

2025-468: Was further clad in waterproof opus signinum . The screed also served to smooth the channel's rate of decline. Ventilation was provided by small, square openings in the roof. At regular intervals on the base of the channel, there were circular depressions, which served to purify the water, since detritus would settle in them. To continue to operate, these had to be cleaned out regularly, so the channel required ongoing care and attention The distribution of

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