The Rio Grande Rise , also called the Rio Grande Elevation or Bromley Plateau , is an aseismic ocean ridge in the southern Atlantic Ocean off the coast of Brazil . Together with the Walvis Ridge off Africa, the Rio Grande Rise forms a V-shaped structure of mirrored hotspot tracks or seamount chains across the northern South Atlantic . In 2013, Brazilian scientists announced that they found granite boulders on the Rio Grande Rise and speculated that it could be the remains of a submerged continent, which they called the "Brazilian Atlantis". Other researchers, however, noted that such boulders can end-up on the ocean floor by less speculative means.
91-518: The Rio Grande Rise separates the Santos and Campos Basins and is composed of western and eastern areas, which have different geological backgrounds. The western area has numerous guyots and seamounts and a basement dated to 80 to 87 million years ago . The eastern area is covered by fracture zones and may represent an abandoned spreading centre. In the western area, volcanic breccia and layers of ash indicate widespread volcanism during
182-501: A ( t − t a ) ] + Δ T 1 1 P 1 1 ( φ ) cos ( τ − τ d ) + ⋯ } {\displaystyle T(\varphi ,\lambda ,t)=T_{\infty }\{1+\Delta T_{2}^{0}P_{2}^{0}(\varphi )+\Delta T_{1}^{0}P_{1}^{0}(\varphi )\cos[\omega _{a}(t-t_{a})]+\Delta T_{1}^{1}P_{1}^{1}(\varphi )\cos(\tau -\tau _{d})+\cdots \}} Here, it
273-610: A rift basin . The rift stage of the basin evolution combined with the arid Aptian climate of the southern latitudes resulted in the deposition of evaporites in the Late Aptian , approximately 112 million years ago. The phase of rifting was followed by a thermal sag phase and drift stage in the widening of the South Atlantic Ocean . This process led to the deposition of a more than 20 kilometres (66,000 ft) thick succession of clastic and carbonate sediments. One of
364-554: A constant mean exospheric temperature (averaged over the sphere), the observed temporal and spatial distribution of the exospheric temperature distribution can be described by a sum of spheric functions: (3) T ( φ , λ , t ) = T ∞ { 1 + Δ T 2 0 P 2 0 ( φ ) + Δ T 1 0 P 1 0 ( φ ) cos [ ω
455-408: A factor of four or more. That solar wind input occurs mainly in the auroral regions during both day and night. Two kinds of large-scale atmospheric waves within the lower atmosphere exist: internal waves with finite vertical wavelengths which can transport wave energy upward, and external waves with infinitely large wavelengths that cannot transport wave energy. Atmospheric gravity waves and most of
546-555: A marine platform setting. The age based on palynomorphs and calcareous nanofossils is Late Cretaceous (Santonian-Maastrichtian). Two new ostracod species were identified in the drilling cuttings of wells drilled into the Santonian-Campanian section, ?Afrocytheridea cretacea and Pelecocythere dinglei . Itamambuca Group is 4,200 metres (13,800 ft) thick and includes four formations, Ponta Aguda, Marambaia , Iguape and Sepetiba . The Ponta Aguda Formation
637-650: A process continuing towards the north later in the Cretaceous. The deposition of the lowermost 600 metres (2,000 ft) of salt in the Aptian would have taken approximately 20,000 to 30,000 years. With the continental break-up of the Santos and Campos Basins from the opposite Namibia and Kwanza Basins , oceanic circulation returned during the post-rift stage. The drift phase since the Late Cretaceous produced
728-433: A scale height inversely proportional to its molecular weight. The lighter constituents atomic oxygen (O), helium (He), and hydrogen (H) successively dominate above an altitude of about 200 kilometres (124 mi) and vary with geographic location, time, and solar activity. The ratio N 2 /O which is a measure of the electron density at the ionospheric F region is highly affected by these variations. These changes follow from
819-774: A sequence of rift basins bordering the present-day South Atlantic. The Pelotas-Namibia spreading commenced in the Hauterivian , around 133 million years ago and reached the Santos Basin to the north in the Barremian . Seafloor spreading continued northwards to the Campos Basin in the Early Albian , at approximately 112 Ma. Five tectonic stages have been identified in the Brazilian basins: The sag phase in
910-420: A solar cycle, and never drops below about 50. Thus, T ∞ varies between about 740 and 1350 K. During very quiet magnetospheric conditions, the still continuously flowing magnetospheric energy input contributes by about 250 K to the residual temperature of 500 K in eq.(2). The rest of 250 K in eq.(2) can be attributed to atmospheric waves generated within the troposphere and dissipated within
1001-438: A thick sequence of clastic and carbonate deposits. Differential thermal regimes and sediment loading of these units produced halokinesis ; salt movement in the subsurface . The resulting salt diapirs , listric and thrust faults and various salt-related structures produced several stratigraphic and combined stratigraphic-structural traps for hydrocarbon accumulation in the Brazilian and southwest African offshore. During
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#17327727845541092-566: A transitional continental and shallow marine environment. The age of this formation has been estimated to be Late Barremian to Aptian. It is correlative with the Macabu Formation in the Campos Basin, as both are typified by laminated microbialites and stromatolites. These limestones are one of the sub-salt reservoirs in the Santos Basin. The Ariri Formation is in the type oil well 581 metres (1,906 ft) thick and may be up to 4,000 metres (13,000 ft) thick in other areas of
1183-499: Is 1,103 metres (3,619 ft) thick and consists of bioclastic calcarenites and calcirudites, containing bryozoa , echinoids , corals , foraminifera, fragmented shells, and algae remains. They are interbedded with grey-greenish clays, siltstones, marls and variegated grey fine-to-medium grained conglomerates. These facies are interbedded with and change laterally to the Marambaia Formation . The depositional environment
1274-674: Is 4,200 metres (13,800 ft) thick and includes four formations, from old to young the Camboriú , Piçarras, Itapema and Barra Velha Formations. The group is equivalent to the Lagoa Feia Group of the Campos Basin. The Camboriú Formation is 40 metres (130 ft) thick and includes the basaltic rocks with a basin–wide distribution. The basalts are dark green to dark grey, holocrystalline, medium grained, with an ophiolitic texture. The main components are plagioclase and augite , usually fresh, non-altered. The Piçarras Formation
1365-508: Is 517 metres (1,696 ft) thick and consists of dark grey shales, silts and light grey marls, ochre-brown calcisilts and subordinated sandstones. These facies change laterally into the coarse clastics of the Florianópolis Formation. Facies analysis indicates a marine environment ranging from sub-littoral (inner neritic) and more rarely to pelagic (outer bathyal) conditions. The age based on planktonic foraminifera and pollen
1456-544: Is 952 metres (3,123 ft) thick and includes a succession of clastics between the coarse facies of the Santos Formation in the west and the fine-grained clastics of the Itajai-Açu Formation in the east. The formation is characterized by dark grey to greenish and brown shales, dark grey siltstones, fine-very fine sandstones and light ochre calcisilts. The depositional environment is thought to be of
1547-452: Is 990 metres (3,250 ft) thick and consists of clastic and carbonate rocks. The formation includes reddish polymictic conglomerates , with clasts of basalt and quartz in a clay-sandy matrix. It also includes white, reddish lacustrine coquinas (shelly limestones) and sandstones, siltstones and shales of stevensite composition. Its age, based on the ostracod assemblages, is Hauterivian to Aptian. The conglomerates and sandstones of
1638-416: Is Early Albian. The Frade Group is 4,000 metres (13,000 ft) thick and includes three formations: Santos , Itajaí-Açu and Juréia . They predominantly comprise turbidites . The Santos Formation is 1,275 metres (4,183 ft) thick and consists of reddish lithic conglomerates and sandstones, interbedded with grey shales and reddish clays. These facies are interbedded and change laterally into
1729-508: Is a good indicator of solar activity, one can apply the empirical formula for quiet magnetospheric conditions. (2) T ∞ ≃ 500 + 3.4 F 0 {\displaystyle T_{\infty }\simeq 500+3.4F_{0}} with T ∞ in K, F o in 10 W m Hz (the Covington index) a value of F averaged over several solar cycles. The Covington index varies typically between 70 and 250 during
1820-687: Is a mostly offshore sedimentary basin across the Tropic of Capricorn , bordering from north to south the Brazilian states of Rio de Janeiro , Sáo Paulo , Paraná and Santa Catarina . The basin covers an area of approximately 352,000 square kilometres (136,000 sq mi), and is bounded in the north by the Cabo Frio High , separating the basin from the Campos Basin and the Florianópolis High and Fracture Zone , separating
1911-439: Is derived from a simple equation of heat conduction. One estimates a total heat input of q o ≃ 0.8 to 1.6 mW/m above z o = 120 km altitude. In order to obtain equilibrium conditions, that heat input q o above z o is lost to the lower atmospheric regions by heat conduction. The exospheric temperature T ∞ is a fair measurement of the solar XUV radiation. Since solar radio emission F at 10.7 cm wavelength
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#17327727845542002-512: Is generated, directed from dawn to dusk. Along the last closed geomagnetic field lines with their footpoints within the auroral zones, field-aligned electric currents can flow into the ionospheric dynamo region where they are closed by electric Pedersen and Hall currents . Ohmic losses of the Pedersen currents heat the lower thermosphere (see e.g., Magnetospheric electric convection field ). Also, penetration of high energetic particles from
2093-744: Is located in the south Atlantic Ocean , some 300 kilometres (190 mi) southeast of Santos , Brazil . The basin is one of the Brazilian basins to have resulted from the break-up of Gondwana since the Early Cretaceous , where a sequence of rift basins formed on both sides of the South Atlantic; the Pelotas, Santos, Campos and Espírito Santo Basins in Brazil, and the Namibia, Kwanza and Congo Basins in southwestern Africa. Santos Basin
2184-455: Is most efficiently excited by solar irradiance is an external wave and plays only a marginal role within the lower and middle atmosphere. However, at thermospheric altitudes, it becomes the predominant wave. It drives the electric Sq-current within the ionospheric dynamo region between about 100 and 200 km height. Heating, predominately by tidal waves, occurs mainly at lower and middle latitudes. The variability of this heating depends on
2275-469: Is regularly replenished by sodium sublimating from incoming meteors. Astronomers have begun using this sodium band to create " guide stars " as part of the optical correction process in producing ultra-sharp ground-based observations. The thermospheric temperature can be determined from density observations as well as from direct satellite measurements. The temperature vs. altitude z in Fig. 1 can be simulated by
2366-416: Is represented by the term P 2 in eq.(3) is reversed. Also, due to the impulsive form of the disturbance, higher-order terms are generated which, however, possess short decay times and thus quickly disappear. The sum of these modes determines the "travel time" of the disturbance to the lower latitudes, and thus the response time of the thermosphere with respect to the magnetospheric disturbance. Important for
2457-800: Is separated from the Campos Basin to the north by the Cabo Frio High and the Pelotas Basin in the south by the Florianópolis High and the northwestern boundary onshore is formed by the Serra Do Mar coastal range. The basin is known for its thick layers of salt that have formed structures in the subsurface due to halokinesis . The basin started forming in the Early Cretaceous on top of the Congo Craton as
2548-497: Is thought to be a marine carbonate platform, influenced by the arrival of alluvial clastics in the most proximal areas. Biostratigraphic data from planktonic foraminifera, calcareous nanofossils and palynomorphs indicate a Tertiary age. The Marambaia Formation is 261 metres (856 ft) thick and consists of grey shales and light grey marls interbedded with fine-grained turbiditic sandstones. This formation in places can be found cropping out at sea bottom. The depositional environment
2639-515: Is thought to be coastal. The stratigraphy following the classifications by Vieira 2007, Kiang Chang 2008 and Contreras 2011 is: 4D Basin analysis of the Santos Basin has revealed insights about the interplay among the elements and processes of the petroleum system to assess source rock potential (vertical and horizontal distribution), thermal evolution of the source rocks, transformation ratio , hydrocarbon generation and charge, timing of migration, oil origin, quality, and volume of petroleum in
2730-459: Is thought to be talus and open marine basin. Biostratigraphic data indicate a Tertiary age. The Sepetiba Formation is the uppermost formation in the Santos Basin. It has a variable thickness due to the proximal erosion of the uppermost part. The formation consists of whitish grey fine to coarse grained carbonitic sands. They are feldspar -rich, glauconitic coquinas consisting of bivalve fragments and foraminifera. The depositional environment
2821-413: Is transported from the poles to the equator. The third term (with P 1 = sin φ) represents heat surplus on the summer hemisphere and is responsible for the transport of excess heat from the summer into the winter hemisphere (Fig. 2b). Its relative amplitude is of the order ΔT 1 ≃ 0.13. The fourth term (with P 1 (φ) = cos φ) is the dominant diurnal wave (the tidal mode (1,−2)). It is responsible for
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2912-432: Is up to 2,200 metres (7,200 ft) thick and consists of conglomerates, coarse to fine-grained sandstones interbedded with siltstones and shales. The dominant facies are coarse to fine-grained quartzitic sandstones. They range from reddish to grey, usually with calcite cements. Intercalated are reddish to light grey claystones and siltstones. They represent a fluvial to shallow marine environment. The Iguape Formation
3003-416: Is up to 6,100 metres (20,000 ft) thick and includes three formations, Florianópolis , Guarujá and Itanhaém . The Florianópolis Formation is 343 metres (1,125 ft) thick in the type oil well, and consists of reddish, fine to coarse-grained sandstones with a clay matrix, reddish micaceous shales and siltstones. These clastic units are thought to represent alluvial environments distributed along
3094-475: Is φ latitude, λ longitude, and t time, ω a the angular frequency of one year, ω d the angular frequency of one solar day, and τ = ω d t + λ the local time. t a = June 21 is the date of northern summer solstice, and τ d = 15:00 is the local time of maximum diurnal temperature. The first term in (3) on the right is the global mean of the exospheric temperature (of the order of 1000 K). The second term [with P 2 = 0.5(3 sin (φ)−1)] represents
3185-524: The Eocene , which coincides with the formation of volcanic rocks onshore. During this period, parts of the western plateau were uplifted over sea level and short-lived volcanic islands formed. When West Gondwana (i.e. South America) broke away from Africa during the Early Cretaceous ( 146 to 100 Ma ), the South Atlantic opened up from its southern to its northern end. In this process,
3276-546: The Neoproterozoic mobile belts composed of less resistant metamorphic rocks . The Precambrian basement of the Santos Basin is exposed as the Araçuaí Belt along the Brazilian coast, most notably in the inselbergs of Rio de Janeiro, of which Sugarloaf Mountain is the most iconic. The ancient rocks consist of a Neoproterozoic to Cambrian high-grade metamorphic core of granites and gneisses , formed during
3367-437: The atmospheric tides generated within the troposphere belong to the internal waves. Their density amplitudes increase exponentially with height so that at the mesopause these waves become turbulent and their energy is dissipated (similar to breaking of ocean waves at the coast), thus contributing to the heating of the thermosphere by about 250 K in eq.(2). On the other hand, the fundamental diurnal tide labeled (1, −2) which
3458-558: The solar constant , the solar XUV radiation is highly variable in time and space. For instance, X-ray bursts associated with solar flares can dramatically increase their intensity over preflare levels by many orders of magnitude over some time of tens of minutes. In the extreme ultraviolet, the Lyman α line at 121.6 nm represents an important source of ionization and dissociation at ionospheric D layer heights. During quiet periods of solar activity , it alone contains more energy than
3549-411: The turbopause at about 90 kilometres (56 mi) to be a mixture of gases that does not change its composition. Its mean molecular weight is 29 g/mol with molecular oxygen (O 2 ) and nitrogen (N 2 ) as the two dominant constituents. Above the turbopause, however, diffusive separation of the various constituents is significant, so that each constituent follows its barometric height structure with
3640-611: The American side. This process resulted in the Tristan-Gough seamount chains on either side of the Tristan-Gough hotspot. A Brazilian-Japanese expedition in 2013 recovered in situ granitic and metamorphic rocks on the Rio Grande Rise. This can possibly indicate that the plateau includes fragments of continental crust — possible remains of micro-continents similar to those found on and around Kerguelen in
3731-772: The Atlantic during the Tertiary ( 66 to 2.58 Ma ). At the beginning of the Maastrichtian, the characteristics of water masses differed north and south of the Rio Grande Rice-Walvis Ridge complex. The disappearance of these differences during the Maastritchtian indicates a reorganisation of oceanic circulation patterns that lead to a global homogenisation of intermediate and deep waters. This process seems to have been triggered by
Rio Grande Rise - Misplaced Pages Continue
3822-553: The Indian Ocean and Jan Mayen in the Arctic Ocean. The existence of such microcontinents is speculative, however, since their remains tend to be covered by younger layers of lava and sediments. Nevertheless, transoceanic dispersals are hinted at by the fossil record of, for example, flightless birds such as Lavocatavis , indicating that several islands between Africa and South America made island hopping possible across
3913-464: The Itajai-Açu and Juréia Formations. The sedimentary environment is thought to be transitional continental to marginal marine, ranging from alluvial to braided rivers and deltas. Biostratigraphic data indicate a Late Cretaceous age (Cenomanian-Maastrichtian). The Itajaí-Açu Formation is 1,545 metres (5,069 ft) thick and comprises a thick interval of dark grey clayey rocks, interbedded with
4004-626: The Itapema Formation is Barremian to Aptian. The Barra Velha Formation is approximately 300 to 350 metres (980 to 1,150 ft) thick. In the proximal sections, the formation comprises limestones of stromatolites and laminated microbialites. In the distal sections, it is composed of shales. Interbedded with the laminated microbialites there are limestones with packstone and grainstone textures made up of algal clasts and bioclasts (fragmented ostracods). The carbonates frequently are partly or completely dolomitized. These facies represent
4095-575: The Rio Grande Rise had been breached by this time, allowing cold, dense water to move north-south through a corridor enhancing the transition from a latitudinal thermospheric circulation to a meridional thermohaline circulation . 31°S 35°W / 31°S 35°W / -31; -35 Santos Basin The Santos Basin ( Portuguese : Bacia de Santos ) is an approximately 352,000 square kilometres (136,000 sq mi) large mostly offshore sedimentary basin . It
4186-529: The Santos Basin from the Pelotas Basin . Along the Brazilian coast, the basin is bounded by the Serra do Mar and stretches from Cabo Frio in the northeast to Florianópolis in the southwest. The city of Rio de Janeiro is located at the coastal edge of the Santos Basin in the northern portion, Santos , Guarujá and the islands of Ilhabela in the central area and Itajaí and Balneário Camboriú in
4277-475: The Santos Basin started in the 1970s. Between 1970 and 1987, 59 dry wells were drilled, with one discovery in Santonian turbidites in 1979, Merluza Field. From 1988 to 1998, 45 wells were drilled in the basin providing small discoveries, with the 30 million barrels (4.8 million cubic metres) of oil equivalent Tubarão Field discovered in 1988. Eighty-one wells were drilled from 1999 to 2005, leading to
4368-456: The Santos Basin was characterised by thermal subsidence and generated restricted depocentres with relatively uniform water depths, ranging from 600 to 950 metres (1,970 to 3,120 ft). The Late Aptian climate was arid with high evaporation rates which triggered hypersaline conditions in these marginal sag basins. This resulted in the accumulation of thick layers of evaporites along the Brazilian and southwestern African continental margins,
4459-544: The Santos Basin. Thermosphere The thermosphere is the layer in the Earth's atmosphere directly above the mesosphere and below the exosphere . Within this layer of the atmosphere, ultraviolet radiation causes photoionization /photodissociation of molecules, creating ions; the thermosphere thus constitutes the larger part of the ionosphere . Taking its name from the Greek θερμός (pronounced thermos ) meaning heat,
4550-475: The alluvial clastics of the Florianópolis Formation. The Guarujá name is restricted to the lowest limestone intercalation, previously named Lower Guarujá by Ojeda and Ahranha in Pereira and Feijó (1994). The microfacies indicate a tidal flat to shallow lagoon and open carbonate platform depositional environment. The age based on planktonic foraminifera and pollen is Early Albian. The Itanhaém Formation
4641-473: The atmospheric particles in this layer to become electrically charged, enabling radio waves to be refracted and thus be received beyond the horizon. In the exosphere, beginning at about 600 km (375 mi) above sea level, the atmosphere turns into space , although, by the judging criteria set for the definition of the Kármán line (100 km), most of the thermosphere is part of space. The border between
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#17327727845544732-400: The average atmospheric scale height ). Eighty percent of that mass is concentrated within the troposphere . The mass of the thermosphere above about 85 kilometres (53 mi) is only 0.002% of the total mass. Therefore, no significant energetic feedback from the thermosphere to the lower atmospheric regions can be expected. Turbulence causes the air within the lower atmospheric regions below
4823-438: The basin. It is predominantly composed of evaporites . The formation is characterized by thick intervals of white halite , associated with white anhydrite , ochre greyish calcilutites, shales and marls . The sedimentary environment probably was restricted marine including mudflat sabkhas , evolving under an arid climate. The ostracod assemblages of this formation indicate a neo-Algoas age (local time scale). The Camburi Group
4914-638: The breaching of the Rio Grande Rise-Walvis Ridge complex and the disappearance of epicontinental seaways such as the Tethys Ocean . The process resulted in the deterioration of rudist -dominated tropical habitats and consequently the extinction of benthic inoceramid bivalves. The origin of modern circulation of cold, deep water — known as the "Big Flush" — is associated with Early Eocene ( 55 to 40 Ma ) geological events; tectonism that resulted in
5005-473: The clastics of the Santos and Juréia Formations. Within this formation, the Ilhabela Member includes the turbiditic sandstones occurring along the section. The sedimentary environment is thought to be marine talus to open basin. Biostratigraphic data from palynomorphs, calcareous nannofossils and planktonic foraminifera indicate a Late Cretaceous age (Cenomanian-Maastrichtian). The Juréia Formation
5096-704: The collision of Gondwana in the Pan-African - Brasiliano orogeny . Basalts similar to the Paraná and Etendeka traps , exposed to the west in the Paraná Basin , have been found underlying the Santos Basin. The Tristan da Cunha hotspot , known as the Tristan hotspot , is considered the driver behind the formation of these flood basalts . During the Early Cretaceous , the former continent Gondwana , as southern part of Pangea , starting to break-up, resulting in
5187-465: The development of an ionospheric storm is the increase of the ratio N 2 /O during a thermospheric storm at middle and higher latitude. An increase of N 2 increases the loss process of the ionospheric plasma and causes therefore a decrease of the electron density within the ionospheric F-layer (negative ionospheric storm). A contraction of the thermosphere has been observed as a possible result in part due to increased carbon dioxide concentrations,
5278-422: The diffusion of the minor constituents through the major gas component during dynamic processes. The thermosphere contains an appreciable concentration of elemental sodium located in a 10-kilometre (6.2 mi) thick band that occurs at the edge of the mesosphere, 80 to 100 kilometres (50 to 62 mi) above Earth's surface. The sodium has an average concentration of 400,000 atoms per cubic centimeter. This band
5369-677: The discovery of the Mexilhão Field. Exploration boomed between 2006 and 2012, with 166 wells and the giant Tupi field (8 BBOE), discovered at the Tupi prospect in 2006. In 2013, the Sagitário Field was discovered in the sub-salt carbonates at a water depth of 1,871 metres (6,138 ft) and a true vertical depth of 6,150 metres (20,180 ft). In 2014, the pre-salt reservoirs of the Santos Basin produced more than 250 thousand barrels per day (40 × 10 ^ m /d). Thanks to
5460-622: The eastern half area is in the main oil window , whereas the western half is in the late oil/wet gas generation window. In terms of transformation ratio, the Barremian and Aptian source rock systems in the area reached 70% to 80% today where the main depocentres are. The charge and accumulation simulation model for the pre-salt province suggests a potential reserve in the Cluster area of Santos Basin much larger than that reported, getting numbers to 60 billion barrels of oil reserves. Exploration in
5551-481: The energy lost by thermal radiation would exceed the energy acquired from the atmospheric gas by direct contact. In the anacoustic zone above 160 kilometres (99 mi), the density is so low that molecular interactions are too infrequent to permit the transmission of sound. The dynamics of the thermosphere are dominated by atmospheric tides , which are driven predominantly by diurnal heating . Atmospheric waves dissipate above this level because of collisions between
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#17327727845545642-433: The equator during equinox . The second source of energy input into the thermosphere is solar wind energy which is transferred to the magnetosphere by mechanisms that are not well understood. One possible way to transfer energy is via a hydrodynamic dynamo process. Solar wind particles penetrate the polar regions of the magnetosphere where the geomagnetic field lines are essentially vertically directed. An electric field
5733-466: The formation are representative of an alluvial environment. The coquinas represent a shallow lacustrine environment . Similar to the Atafona Formation of the Campos Basin, the sandstones, stevensite-bearing siltstones and shales represent an alkaline lacustrine environment affected by volcanic activity. The shales represent deeper lacustrine waters in more distal areas. The alternation of
5824-492: The formation consists of dark organic matter rich shales. In the well 1-RSJ-625, the formation includes 110 metres (360 ft) of radioactive shales interbedded with carbonates. These facies are thought to represent a lacustrine environment. The organic matter-rich shales are one of the main source rocks of the Santos Basin. This formation is correlative with the Coqueiros Formation in the Campos Basin. The age of
5915-412: The ground by geomagnetic variations, show an unpredictable impulsive character, from short periodic disturbances of the order of hours to long-standing giant storms of several days' duration. The reaction of the thermosphere to a large magnetospheric storm is called a thermospheric storm. Since the heat input into the thermosphere occurs at high latitudes (mainly into the auroral regions), the heat transport
6006-496: The heat surplus at lower latitudes and a corresponding heat deficit at higher latitudes (Fig. 2a). A thermal wind system develops with the wind toward the poles in the upper level and winds away from the poles in the lower level. The coefficient ΔT 2 ≈ 0.004 is small because Joule heating in the aurora regions compensates that heat surplus even during quiet magnetospheric conditions. During disturbed conditions, however, that term becomes dominant, changing sign so that now heat surplus
6097-399: The largest Brazilian sedimentary basins, it is the site of several recently (2007 and later) discovered giant oil and gas fields , including the first large pre-salt discovery Tupi (8 billion barrels), Júpiter (1.6 billion barrels and 17 tcf of gas), and Libra , with an estimated 8 to 12 billion barrels of recoverable oil. Main source rocks are the lacustrine shales and carbonates of
6188-410: The lower thermosphere. The solar X-ray and extreme ultraviolet radiation (XUV) at wavelengths < 170 nm is almost completely absorbed within the thermosphere. This radiation causes the various ionospheric layers as well as a temperature increase at these heights (Figure 1). While the solar visible light (380 to 780 nm) is nearly constant with the variability of not more than about 0.1% of
6279-442: The magnetosphere into the auroral regions enhance drastically the electric conductivity, further increasing the electric currents and thus Joule heating . During the quiet magnetospheric activity, the magnetosphere contributes perhaps by a quarter to the thermosphere's energy budget. This is about 250 K of the exospheric temperature in eq.(2). During the very large activity, however, this heat input can increase substantially, by
6370-462: The main reservoirs. In a basin modeling study performed in 2008 and 2009, a detailed facies model from the pre-salt section was built based on well data and conceptual models from seismic interpretation associated with previous knowledge of the tectono-sedimentary sequences of the Santos Basin. The predicted vitrinite map , integrated with all data, indicates that the Coquinas source rock in most of
6461-415: The meteorological conditions within the troposphere and middle atmosphere, and may not exceed about 50%. Within the thermosphere above an altitude of about 150 kilometres (93 mi), all atmospheric waves successively become external waves, and no significant vertical wave structure is visible. The atmospheric wave modes degenerate to the spherical functions P n with m a meridional wave number and n
6552-606: The neutral gas and the ionospheric plasma. The thermosphere is uninhabited with the exception of the International Space Station , which orbits the Earth within the middle of the thermosphere between 408 and 410 kilometres (254 and 255 mi) and the Tiangong space station , which orbits between 340 and 450 kilometres (210 and 280 mi). It is convenient to separate the atmospheric regions according to
6643-760: The onshore stretch of the basin ranges from tropical savanna climate (Aw), tropical monsoon climate (Am) and tropical rainforest climate (Af) to a humid subtropical climate (Cfa). The onshore portion of the Santos Basin is in the Serra do Mar coastal forests ecoregion of the Atlantic Forest biome. On the islands of the Superagüi National Park in the Santos Basin, the endemic critically endangered Superagüi lion tamarin ( Leontopithecus caissara ) has its restricted habitat. The South Atlantic margin developed on Archean stable cratons consisting of hard and resistant rocks and partly on
6734-649: The opening of the north-east Atlantic and fracture zones that developed in the subsiding Rio Grande Rise, which allowed cold water from the Antarctic Weddell Sea to flow northward into the North Atlantic. 40 Ma , the generation of cold bottom water in the Antarctic resulted in the formation of psychrospheric fauna, which today live in temperatures below 10 °C (50 °F), in the Atlantic and Tethys. This global distribution suggests that
6825-542: The phases of halokinesis, dated to the Albian to Paleocene , several areas of the now deep water distal part of the Santos Basin were exposed to subaerial conditions and suffered erosion. The distal parts of the basin were affected by E-W to NW-SE oriented shortening, sub-perpendicular to the Brazilian margin. The basement of the Santos Basin is composed of granites and gneisses of the Araçuarí Belt that formed at
6916-640: The pre-salt Guaratiba Group and the marine shales of the post-salt Itajaí-Açu Formation. Reservoir rocks are formed by the pre-salt Guaratiba sandstones , limestones and microbialites , the Albian limestones of the Guarujá Formation and the Late Cretaceous to Paleogene turbiditic sandstones of the Itanhaém, Juréia, Itajaí-Açu, Florianópolis and Marambaia Formations. The mobile salt of the Ariri Formation forms regional seals , as well as
7007-537: The pre-salt production, compensating for the declining post-salt production, the total oil production of Brazil rose above 2,500 thousand barrels per day (400 × 10 ^ m /d) in April 2016. The Lapa Field, originally named Carioca, was taken in production in December 2016. In 2017, the Santos Basin accounted for 35% of Brazil's oil, with the Campos Basin at 55%. In the same year, 76 blocks were open for bidding in
7098-520: The rest of the XUV spectrum. Quasi-periodic changes of the order of 100% or greater, with periods of 27 days and 11 years, belong to the prominent variations of solar XUV radiation. However, irregular fluctuations over all time scales are present all the time. During the low solar activity, about half of the total energy input into the thermosphere is thought to be solar XUV radiation. That solar XUV energy input occurs only during daytime conditions, maximizing at
7189-414: The shales of the post-salt sedimentary infill. In 2014, the total production of only the sub-salt reservoirs accumulated to more than 250 thousand barrels per day (40 × 10 ^ m /d). In 2017, the Santos Basin accounted for 35% of Brazil's oil, with the northern neighbour Campos Basin at 55%. The Santos Basin is named after the coastal city of Santos in the state of São Paulo . The Santos Basin
7280-574: The so-called Bates profile: (1) T = T ∞ − ( T ∞ − T 0 ) e − s ( z − z 0 ) {\displaystyle T=T_{\infty }-(T_{\infty }-T_{0})e^{-s(z-z_{0})}} with T ∞ the exospheric temperature above about 400 km altitude, T o = 355 K, and z o = 120 km reference temperature and height, and s an empirical parameter depending on T ∞ and decreasing with T ∞ . That formula
7371-471: The south of the basin. Within the basin, several highs are located. The Outer High, in the distal part of the Santos Basin, is the most prominent and extensive intra-basinal high with an approximate area of 12,000 square kilometres (4,600 sq mi). The Outer High is likely a segmented series of rift fault-block shoulders which were uplifted and eroded during the Late Barremian. The climate of
7462-424: The temperature maximum near an altitude of 45 kilometres (28 mi) and causes the ozone layer. The density of the Earth's atmosphere decreases nearly exponentially with altitude. The total mass of the atmosphere is M = ρ A H ≃ 1 kg/cm within a column of one square centimeter above the ground (with ρ A = 1.29 kg/m the atmospheric density on the ground at z = 0 m altitude, and H ≃ 8 km
7553-480: The thermosphere and exosphere is known as the thermopause . The highly attenuated gas in this layer can reach 2,500 °C (4,530 °F). Despite the high temperature, an observer or object will experience low temperatures in the thermosphere, because the extremely low density of the gas (practically a hard vacuum ) is insufficient for the molecules to conduct heat. A normal thermometer will read significantly below 0 °C (32 °F), at least at night, because
7644-432: The thermosphere begins at about 80 km (50 mi) above sea level. At these high altitudes, the residual atmospheric gases sort into strata according to molecular mass (see turbosphere ). Thermospheric temperatures increase with altitude due to absorption of highly energetic solar radiation . Temperatures are highly dependent on solar activity, and can rise to 2,000 °C (3,630 °F) or more. Radiation causes
7735-491: The transport of excess heat from the daytime hemisphere into the nighttime hemisphere (Fig. 2d). Its relative amplitude is ΔT 1 ≃ 0.15, thus on the order of 150 K. Additional terms (e.g., semiannual, semidiurnal terms, and higher-order terms) must be added to eq.(3). However, they are of minor importance. Corresponding sums can be developed for density, pressure, and the various gas constituents. In contrast to solar XUV radiation, magnetospheric disturbances, indicated on
7826-504: The two facies implies a series of alluvial progradation-retractions into the Cretaceous carbonate lakes. The low textural and compositional maturity of conglomerates and sandstones implies the basin was supplied from areas close to the basin margins. The Itapema Formation is several hundreds of metres thick and consists of calcirudites (limestones) and dark shales. The calcirudite limestones consist of fragmented bivalve shells, frequently dolomitized and silicified. In more distal sections,
7917-431: The two temperature minima at an altitude of about 12 kilometres (7.5 mi) (the tropopause ) and at about 85 kilometres (53 mi) (the mesopause ) (Figure 1). The thermosphere (or the upper atmosphere) is the height region above 85 kilometres (53 mi), while the region between the tropopause and the mesopause is the middle atmosphere ( stratosphere and mesosphere ) where absorption of solar UV radiation generates
8008-711: The voluminous Paraná and Etendeka continental flood basalts formed in what is now Brazil and Namibia . This event is linked to the Tristan-Gough hotspot , now located near the Mid-Atlantic Ridge , close to Tristan da Cunha and the Gough Islands . During the Maastrichtian ( 60 Ma ), the orientation of spreading changed, which is still visible on the African side, and volcanism ended on
8099-725: The western Brazilian basin margin, along the Santos Hinge Line. These alluvial environments were gradational towards the east, with the shallow marine carbonates of the Guarujá Formation, and further to the open basin with the siltstones of the Itanhaém Formation. Biostratigraphical data and its relations with the Guarujá Formation point towards an Albian age. The Guarujá Formation is 832 metres (2,730 ft) thick and consists of oolitic calcarenites , which laterally grade to greyish ochre and brownish grey calcilutites and grey marls. These facies are interbedded with
8190-459: The western boundary of the Congo Craton. The erosion resistant metamorphic and magmatic rocks are exposed in the Serra do Mar , forming the edge of the Santos Basin along the Brazilian coast. The total stratigraphic thickness of the sediments in the Santos Basin has been estimated at 23,170 metres (76,020 ft) and has been described in detail by Clemente in 2013. The Guaratiba Group
8281-407: The zonal wave number (m = 0: zonal mean flow; m = 1: diurnal tides; m = 2: semidiurnal tides; etc.). The thermosphere becomes a damped oscillator system with low-pass filter characteristics. This means that smaller-scale waves (greater numbers of (n,m)) and higher frequencies are suppressed in favor of large-scale waves and lower frequencies. If one considers very quiet magnetospheric disturbances and
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