Nubian Sandstone
Encyclopedia
Nubian Sandstone refers to a variety of sedimentary rocks deposited on the Precambrian
Basement
in the eastern Sahara, north-east Africa and Arabia. It consist of continental sandstones with thin beds of marine
limestones, and marl
s. Nubian sandstone was deposited between the Lower Paleozoic
and Upper Cretaceous
, with marine beds dating from the Carboniferous
to Lower Cretaceous.
in Africa during 210 to 110 million years and extended this period to 85 million years. Nubian sandstone is deposited under a tropical to subtropical climate and is formed under a variety of continental conditions, excluding eolian merging intermittently into shallow marine.
The Nubian sandstone complex has a thickness varying from under 500 m to over 3000 m, resting on the Precambrian basement. This is complicated by various structural faults and fold axes traversing the region in a north-eastern direction. Maximum development occurs in the Ain Dalla basin, a downthrown structural block south-west of the Bahariya oasis. Basement
features present a dominant control on the complex's structural and sedimentological form. Despite many structural complications, Nubian sandstone likely constitutes a single hydrogeological system west of the Suez Gulf
. To the east, on the Sinai peninsula
, a second system might exist with some connection to the primary western system in the north. The main western system, extending into Libya
and Sudan, consists of a multi-layered artesian
basin where massive groundwater reserves accumulated, principally during pluvials of the Quaternary
. Locally, carbonate
rocks overlying the complex display karst
features and are recharged by upwards leaks from the underlying major aquifer
. Fluvial
and structural interpretations from 2007 show the desert in western Egypt was induced by fluvial action, including recently mapped alluvial fans. In central areas, braided channels are spatially aligned to a north-east structural trend, suggesting preferential water flow paths. Alluvial fans and structurally enclosed channels coincided to gentle slopes and optimal recharge conditions between 1 and 5%, indicating high groundwater potential. Synthetic Aperture Radar
(SAR) interpretations correlated with anomalies from groundwater in 383 wells, suggesting a connection between the spatial organization of fluvial and structural features with low-salinity
groundwater, which exists adjacent to alluvial fans and the south-west reaches of structurally enclosed channels. Wells in the vicinity of structures contained low-salinity water.
conditions produce soil
that is red-sandy but very different in other aspects. Only in sub-humid zones do these soils contain a moderately developed profile, including a textural B horizon lacking soluble salts and carbonates. In semi-arid and arid zones, profile differentiation is either weak or does not exist. In arid zones soils are shallow and contain carbonates, and soluble salts, including gypsum
. The sole clay
common to all Nubian sandstone parent materials is Kaolinite
, which is the major clay mineral in sub-humid zone soil. In semi-arid soils smectite is a second major clay component. In arid zones small amounts of smectite and palygorskite
accompany kaolinite. It is likely that smectite and palygorskite are products of pedogenic neoformation. Aeolian material was probably introduced into the silt
and fine sand fractions from semi-arid and arid soils. It is also possible that some contamination of clay fractions occurred.
, Nubian sandstone underlies the latter conformably. In Lebanon
, Anti-Lebanon
and Hermon it is underlaid by Jurassic limestone. Its upper strata is likely from the Lower or Middle Cretaceous age. However, Jurassic limestone is absent in southern areas. In Western Sinai, Nubian sandstone rests on Carboniferous limestone, and by the Dead Sea
on Cambrian limestone: at Petra
and other locations it rests unconformably on Crystalline rocks. While age calculation for Nubian sandstone is relatively simple in Lebanon, Anti-Lebanon and Hermon, it is much more complicated in Western Sinai and the Dead Sea. Since sandstone is assumed to form more rapidly than other rocks it is difficult to conceive that the 2,000 feet of sandstone in the southeastern Dead Sea was in the formative process from the Cambrian to the Cretaceous.
Nubian Sandstone is most commonly brown or reddish, but in places it shows a much wider variety of color. The ancient temples and tombs in Petra were carved from this rock. In certain places it is extremely friable, and in others compact and hard. Sand in the Arabian deserts was primarily derived from it, carried by prevailing western winds. Where it is covered by a sheet of eruptive rock (charrah), it is protected from erosion
. Nubian sandstone frequently includes strata of clay and shale and thin seams of coal
or lignite
. This indicates that it was deposited in seas that were relatively shallow at the time.
by Joseph Rüssegger in 1837, who used the term "Sandstein von Nubien" to designate nonfossiliferous sandstone
sections of Paleozoic or Mesozoic age. Russegger followed and studied this series of sandstone formations from the Sudan
, Egypt
, Libya
, and Arabia Petrsea.
Precambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
Basement
Basement (geology)
In geology, the terms basement and crystalline basement are used to define the rocks below a sedimentary platform or cover, or more generally any rock below sedimentary rocks or sedimentary basins that are metamorphic or igneous in origin...
in the eastern Sahara, north-east Africa and Arabia. It consist of continental sandstones with thin beds of marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
limestones, and marl
Marl
Marl or marlstone is a calcium carbonate or lime-rich mud or mudstone which contains variable amounts of clays and aragonite. Marl was originally an old term loosely applied to a variety of materials, most of which occur as loose, earthy deposits consisting chiefly of an intimate mixture of clay...
s. Nubian sandstone was deposited between the Lower Paleozoic
Paleozoic
The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...
and Upper Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
, with marine beds dating from the Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
to Lower Cretaceous.
Formation
Nubian sandstone ranges in age from the Cambrian to Upper Cretaceous eras. Positioning of the paleoequator and paleolatitude at 20° S was derived from paleomagnetic data showing Nubian sandstone was originally deposited in the paleoequatorial to subequatorial zone. These paleomagnetic results corroborated previous studies suggesting there was no polar wandering and continental driftContinental drift
Continental drift is the movement of the Earth's continents relative to each other. The hypothesis that continents 'drift' was first put forward by Abraham Ortelius in 1596 and was fully developed by Alfred Wegener in 1912...
in Africa during 210 to 110 million years and extended this period to 85 million years. Nubian sandstone is deposited under a tropical to subtropical climate and is formed under a variety of continental conditions, excluding eolian merging intermittently into shallow marine.
Characteristics
Basement
__FORCETOC__A basement is one or more floors of a building that are either completely or partially below the ground floor. Basements are typically used as a utility space for a building where such items as the furnace, water heater, breaker panel or fuse box, car park, and air-conditioning system...
features present a dominant control on the complex's structural and sedimentological form. Despite many structural complications, Nubian sandstone likely constitutes a single hydrogeological system west of the Suez Gulf
Gulf of Suez
The northern end of the Red Sea is bifurcated by the Sinai Peninsula, creating the Gulf of Suez in the west and the Gulf of Aqaba to the east. The Gulf of Suez is formed within a relatively young, but now inactive rift basin, the Gulf of Suez Rift, dating back about 28 million years...
. To the east, on the Sinai peninsula
Sinai Peninsula
The Sinai Peninsula or Sinai is a triangular peninsula in Egypt about in area. It is situated between the Mediterranean Sea to the north, and the Red Sea to the south, and is the only part of Egyptian territory located in Asia as opposed to Africa, effectively serving as a land bridge between two...
, a second system might exist with some connection to the primary western system in the north. The main western system, extending into Libya
Libya
Libya is an African country in the Maghreb region of North Africa bordered by the Mediterranean Sea to the north, Egypt to the east, Sudan to the southeast, Chad and Niger to the south, and Algeria and Tunisia to the west....
and Sudan, consists of a multi-layered artesian
Artesian aquifer
An artesian aquifer is a confined aquifer containing groundwater under positive pressure. This causes the water level in a well to rise to a point where hydrostatic equilibrium has been reached. This type of well is called an artesian well...
basin where massive groundwater reserves accumulated, principally during pluvials of the Quaternary
Quaternary
The Quaternary Period is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS. It follows the Neogene Period, spanning 2.588 ± 0.005 million years ago to the present...
. Locally, carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
rocks overlying the complex display karst
KARST
Kilometer-square Area Radio Synthesis Telescope is a Chinese telescope project to which FAST is a forerunner. KARST is a set of large spherical reflectors on karst landforms, which are bowlshaped limestone sinkholes named after the Kras region in Slovenia and Northern Italy. It will consist of...
features and are recharged by upwards leaks from the underlying major aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
. Fluvial
Fluvial
Fluvial is used in geography and Earth science to refer to the processes associated with rivers and streams and the deposits and landforms created by them...
and structural interpretations from 2007 show the desert in western Egypt was induced by fluvial action, including recently mapped alluvial fans. In central areas, braided channels are spatially aligned to a north-east structural trend, suggesting preferential water flow paths. Alluvial fans and structurally enclosed channels coincided to gentle slopes and optimal recharge conditions between 1 and 5%, indicating high groundwater potential. Synthetic Aperture Radar
Synthetic aperture radar
Synthetic-aperture radar is a form of radar whose defining characteristic is its use of relative motion between an antenna and its target region to provide distinctive long-term coherent-signal variations that are exploited to obtain finer spatial resolution than is possible with conventional...
(SAR) interpretations correlated with anomalies from groundwater in 383 wells, suggesting a connection between the spatial organization of fluvial and structural features with low-salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
groundwater, which exists adjacent to alluvial fans and the south-west reaches of structurally enclosed channels. Wells in the vicinity of structures contained low-salinity water.
Derived soils
Nubian sandstone exposures in sub-humid, semi-arid, and aridArid
A region is said to be arid when it is characterized by a severe lack of available water, to the extent of hindering or even preventing the growth and development of plant and animal life...
conditions produce soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
that is red-sandy but very different in other aspects. Only in sub-humid zones do these soils contain a moderately developed profile, including a textural B horizon lacking soluble salts and carbonates. In semi-arid and arid zones, profile differentiation is either weak or does not exist. In arid zones soils are shallow and contain carbonates, and soluble salts, including gypsum
Gypsum
Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is found in alabaster, a decorative stone used in Ancient Egypt. It is the second softest mineral on the Mohs Hardness Scale...
. The sole clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
common to all Nubian sandstone parent materials is Kaolinite
Kaolinite
Kaolinite is a clay mineral, part of the group of industrial minerals, with the chemical composition Al2Si2O54. It is a layered silicate mineral, with one tetrahedral sheet linked through oxygen atoms to one octahedral sheet of alumina octahedra...
, which is the major clay mineral in sub-humid zone soil. In semi-arid soils smectite is a second major clay component. In arid zones small amounts of smectite and palygorskite
Palygorskite
Palygorskite or attapulgite is a magnesium aluminium phyllosilicate with formula 2Si4O10·4 which occurs in a type of clay soil common to the Southeastern United States. It is one of the types of fuller's earth.-Name:...
accompany kaolinite. It is likely that smectite and palygorskite are products of pedogenic neoformation. Aeolian material was probably introduced into the silt
Silt
Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...
and fine sand fractions from semi-arid and arid soils. It is also possible that some contamination of clay fractions occurred.
Nubian Sandstone in Arabia
When in contact with Upper Cretaceous limestoneLimestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
, Nubian sandstone underlies the latter conformably. In Lebanon
Lebanon
Lebanon , officially the Republic of LebanonRepublic of Lebanon is the most common term used by Lebanese government agencies. The term Lebanese Republic, a literal translation of the official Arabic and French names that is not used in today's world. Arabic is the most common language spoken among...
, Anti-Lebanon
Anti-Lebanon
The Anti-Lebanon mountains is the Western name for the Eastern Lebanon Mountain Range , which are a southwest-northeast-trending mountain range between Syria and Lebanon. Its Western name comes from the Greek word for ‘opposite’. The majority of the mountain range lies in Syria. The border between...
and Hermon it is underlaid by Jurassic limestone. Its upper strata is likely from the Lower or Middle Cretaceous age. However, Jurassic limestone is absent in southern areas. In Western Sinai, Nubian sandstone rests on Carboniferous limestone, and by the Dead Sea
Dead Sea
The Dead Sea , also called the Salt Sea, is a salt lake bordering Jordan to the east and Israel and the West Bank to the west. Its surface and shores are below sea level, the lowest elevation on the Earth's surface. The Dead Sea is deep, the deepest hypersaline lake in the world...
on Cambrian limestone: at Petra
Petra
Petra is a historical and archaeological city in the Jordanian governorate of Ma'an that is famous for its rock cut architecture and water conduits system. Established sometime around the 6th century BC as the capital city of the Nabataeans, it is a symbol of Jordan as well as its most visited...
and other locations it rests unconformably on Crystalline rocks. While age calculation for Nubian sandstone is relatively simple in Lebanon, Anti-Lebanon and Hermon, it is much more complicated in Western Sinai and the Dead Sea. Since sandstone is assumed to form more rapidly than other rocks it is difficult to conceive that the 2,000 feet of sandstone in the southeastern Dead Sea was in the formative process from the Cambrian to the Cretaceous.
Appearance
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
. Nubian sandstone frequently includes strata of clay and shale and thin seams of coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
or lignite
Lignite
Lignite, often referred to as brown coal, or Rosebud coal by Northern Pacific Railroad,is a soft brown fuel with characteristics that put it somewhere between coal and peat...
. This indicates that it was deposited in seas that were relatively shallow at the time.
Etymology
The term ״Nubia sandstone״ was first introduced to the Egyptian stratigraphyStratigraphy
Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....
by Joseph Rüssegger in 1837, who used the term "Sandstein von Nubien" to designate nonfossiliferous sandstone
sections of Paleozoic or Mesozoic age. Russegger followed and studied this series of sandstone formations from the Sudan
Sudan
Sudan , officially the Republic of the Sudan , is a country in North Africa, sometimes considered part of the Middle East politically. It is bordered by Egypt to the north, the Red Sea to the northeast, Eritrea and Ethiopia to the east, South Sudan to the south, the Central African Republic to the...
, Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
, Libya
Libya
Libya is an African country in the Maghreb region of North Africa bordered by the Mediterranean Sea to the north, Egypt to the east, Sudan to the southeast, Chad and Niger to the south, and Algeria and Tunisia to the west....
, and Arabia Petrsea.
See also
- Nubian Aquifer System
- Arabian-Nubian ShieldArabian-Nubian ShieldThe Arabian-Nubian Shield is an exposure of Precambrian crystalline rocks on the flanks of the Red Sea. The crystalline rocks are mostly Neoproterozoic in age. Geographically - and from north to south - the ANS includes the nations of Israel, Jordan. Egypt, Saudi Arabia, Sudan, Eritrea,...
- Sedimentary rockSedimentary rockSedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....
- ShieldShield (geology)A shield is generally a large area of exposed Precambrian crystalline igneous and high-grade metamorphic rocks that form tectonically stable areas. In all cases, the age of these rocks is greater than 570 million years and sometimes dates back 2 to 3.5 billion years...
- CratonCratonA craton is an old and stable part of the continental lithosphere. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates. They are characteristically composed of ancient crystalline basement rock, which may be covered by...
- PlatformPlatform (geology)In geology, a platform is a continental area covered by relatively flat or gently tilted, mainly sedimentary strata, which overlie a basement of consolidated igneous or metamorphic rocks of an earlier deformation...
- BasementBasement (geology)In geology, the terms basement and crystalline basement are used to define the rocks below a sedimentary platform or cover, or more generally any rock below sedimentary rocks or sedimentary basins that are metamorphic or igneous in origin...
- Platform basement