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74-533: The formation is composed of fluvial- lacustrine deposits , typically sandstones and shales with a saline paleolake carbonate evaporitic sequence of limestone in its lowest Las Chacritas Member. Interbedded with these are volcanic tuffites. It is divided into two members, the Las Chacritas Member, and the overlying Puesto Almada member, but the latter has also been assigned to the overlying Cañadón Calcáreo Formation by other authors. The exact age of

148-420: A Callovian-Oxfordian unit. Following this definition, Tasch & Volkheimer published the main initial faunal review of the strata in 1970, with a clear focus on the spinicaudatan fauna, though it also included the first regional correlations. This work was followed by that of others, such as C. Nakayama in 1972, F. Nullo & C. Proserpio in 1975 and J.M.C. Turner in 1983, all focused on the geological aspects of

222-531: A definitive age constraint of all the biota recovered in this layers to 179.17 ± 0.12 Ma-178.07 ± 0.21 Ma. The Puesto Almada member is in a more complex situation, as seems some or all of its layers can belong on reality to the Cañadón Calcáreo Formation . A separate unit in between the two has been even suggested, the Sierra de la Manea Formation , and this last one can include a great part of

296-631: A formation. Lacustrine deposits can form in every variety of basins found in nature. How each basin originates is where the distinction between lacustrine deposit types stem. Rift graben lakes are formed from crustal stretching also known as rifting. Sediment influx is typically dominated by precipitation runoff and discharge through channels migrating towards the depression. Oxbow lakes form lacustrine deposits from seasonal overbank flooding as well as precipitation runoff which refills these isolated basins with fresh water and new sediments. Glacial lakes form when terminal moraines block water from escaping

370-472: A juvenile individual. Based upon how broad , high and short the adult articulated mandibles of Patagosaurus are, its snout would have been short, high and broad as well, a typical feature of most sauropods. The teeth of Patagosaurus are reminiscent of more derived sauropods. They are similar in morphology to Euhelopus , being concave on one side as well as having crowns with fairly great expansions. They are also similar to Camarasaurus , although

444-419: A microbial belt. The increased amount of algal matter and microbial bioherms suggest highstand levels of the lake, while on layers where mudcracks and pedogenesis occurs shows likely a lowstand of the water level that killed the microbial matter. It has been determined that the main lacustrine body existed in the so-called "Cerro Cóndor Biohermal Belt", while Cañadón Las Chacritas facies show progradations towards

518-416: A paper on early sauropods, finding Patagosaurus as a cetiosaurid again. He found that although earlier works had distinguished two groups, the shunosaurines and cetiosaurines, in the family, but that Shunosaurus and relatives were actually closer to Euhelopus , and cetiosaurines ( Cetiosaurus , Patagosaurus and Amygdalodon ) were the only true cetiosaurids. Upchurch noted, however, that further work on

592-505: A similar genus, by features of the ischium and vertebrae. Another genus also identified as a cetiosaurid by Bonaparte, Volkheimeria , was named in the same paper as Patagosaurus . Features uniting the genera were identified in the pelvic structure and vertebrae, specifically the caudal neural spines and the ilium and ischium. These characteristics show that the genera are more derived than Amygdalodon , yet more primitive than Haplocanthosaurus . Later in 1995, Paul Upchurch published

666-407: A unique taxon. Bonaparte (1986) assigned three specimens other than the holotype PVL 4170, PVL 4076, MACN CH 934 and MACN CH 933 to the genus. While the holotype includes a postcranial skeleton, the others are known from cranial material and a nearly complete juvenile skeleton and skull. MACN CH 933 is directly comparable with the type material of Patagosaurus , which confirms its association with

740-460: A well-developed cnemial crest , and is also short and robust. The surface that would have articulated with the astragalus in life has the anterior half raised, and the posterior half lowered. The pectoral girdle is well known. Both the left and right scapulae and coracoids are known, though incomplete. The scapulae are large and robust, and thicken as they near the glenoids. The scapular blades are flat, although they are both convex along

814-665: Is almost complete, only lacking the proximal ends of each ischium . The ilia of the holotype are well known, and show many distinct features. The pubic peduncle, where the ilium articulates with the pubis, is long and straight and has an expansion on the end, as in many sauropods. The upper edge of the iliac blade is curved and thick, with rugosities (rough spots) for cartilage attachment. The pubic elements are large and robust in adults, more so than in juveniles. They are flat when viewed from in front, and convex when seen from behind. Lapparentosaurus resembles Patagosaurus when comparing their pubes. The ischia are much more gracile than

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888-431: Is complete, although sediment-filled breaks might have altered its original shape. The forelimb of Patagosaurus is much more gracile and different from the robust later sauropods like Camarasaurus and Apatosaurus , and instead resembles more Diplodocus . When originally described, Patagosaurus was identified as a relative of Cetiosaurus in the family Cetiosauridae . It can be distinguished from Cetiosaurus ,

962-420: Is mostly made of two major depositional settings: lacustrine and fluvial deposits, that have intervals of tuffaceous materials, suggesting this environments coevolved with volcanic activity. Palustrine littoral environments levels are seen at Cerro Cóndor and Estancia Fossati, characterized by the presence of lacustrine limestones interbedded with shales, tuffs and sandstones. The lacustrine section has been called

1036-572: Is seen also in the Antarctic Peninsula Sweeney Formation and in the Larsen Basin, that represent a continuation of the same Biozone both Lonco Tapial and Cañadón Asfalto are included. The abundance of organic matter in the lacustrine facies, great presence of microinvertebrate fauna together with the rare presence of mudcracks, low breccia presence and pedogeniclayers suggest that the immediate setting along

1110-465: Is similar to closely related taxa like Cetiosaurus and Volkheimeria , more primitive genera such as Barapasaurus and Amygdalodon , and more derived sauropods like Diplodocus and Camarasaurus . In the 1970s many specimens of a previously unidentified dinosaur were found associated together in the same bed and locality: a pebbly stratum near a route to Cerro Condor . The specimens were first described by José Bonaparte in 1979 . For

1184-835: The Bahía Laura Volcanic Complex ( Deseado Massif ), the Quemado Complex ( Austral Patagonia ) & the Tobífera and Lemaire Formations ( Fuegian Andes ). Other Units include Bajo Pobre , Cañadón Huemules and Roca Blanca Formations in Argentina. Finally in Antarctica the Mapple , Brennecke Formations & Ellsworth Land Volcanic Group and Ellsworth-Whitmore terrane isolated granitoids. The Volcanic-Lacustrine interbeds found in units like

1258-753: The Cañadón Calcáreo Formation , as well the crocodilian genus Almadasuchus , all of this is due to the uncertain difference and limit between both units. Overall climate conditions where similar to the underliying section, yet with a more marked seasonality and a more humid touch. The rocks of the formation preserve a diverse biota, including plants, dinosaurs, invertebrates, mammals and pterosaurs, among others. Notable named dinosaurs include theropods ( Asfaltovenator , Condorraptor , Eoabelisaurus , and Piatnitzkysaurus ), sauropods ( Bagualia , Patagosaurus , and Volkheimeria ), and ornithischians ( Manidens ). Lacustrine deposits Lacustrine deposits are sedimentary rock formations which formed in

1332-878: The Ellsworth Land Volcanic Group of the Antarctic Peninsula are not only coeval with, but also continuations of the biozone seen in the Chacritas member. The study of the Jurassic deposits of the Cañadón Asfalto Basin started with Alejandro Matveievich Piatnitzky in 1936, who studied the zone from the Genoa River to the Chubut River , dividing it into several stratigraphic units. In doing this he described

1406-692: The Magallanes Basin . The type locality of the Formation at Cañadón Asfalto creek records strata accumulated in rift-related, lacustrine-fluvial-alluvial environments intermittently subjected to volcanic input, resembling the same conditions in the modern African Great Rift Valley . Floral composition was made of Lycophytes , Equisetales , Ferns , Conifers , Bennettitales and Peltaspermales , all along abundance of charcoal particles, suggest frequent Wildfires and/or Forest fires . Deep lacutrine bodies show abundance of Charales . This member

1480-823: The Subcordilleran Plutonic Belt and the North Patagonian Batholith , coeval with volcanic activity occurring inland like Chon Aike in the east. Between the Subcordilleran Batholith and Chon Aike lied an elongated shape rifted basin with various small basins and grabens caused by regional faults that undergoed different phases of rifting during the Upper Sinemurian -Lower Pliensbachian , resulting in diverse volcanic phenomena like caldera formation and explosive eruptions due to magma intrusion. Latter in

1554-426: The sacrum possesses many distinct features. The sacrum is well preserved, showing that Patagosaurus possessed five sacral vertebrae. All the vertebrae but the fifth are fused together. All the neural spines are tall, and the centra are occasionally transversely narrow. The neural canal of the vertebrae is unique among sauropods, however. Starting from the very end of the first vertebra, and extending to almost

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1628-799: The "Chacritas Paleolake", and seems to have been a rather saline or even hypersaline hydrologically closed pan lake, shallow in deep, with marginal zones and palustrine subenvironments made of low-energy ramp-like margins. This can be seen on several sections such as the Cañadón Carrizal, where layers that how aerial exposures, and so a regression tendency in a low-energy lake, what changued the biota locally (ex. microbial activity on surfaces). The lacustrine facies can be seen in other locations, as in Quebrada de las Chacritas, where at least 5 types of different facies, with both lacustrine and Stromatolite bioherm origin were described, showing this last ones

1702-551: The African Rift. This chert is indicator of high alkaline settings in shallow lacustrine units, thus temporal increasing of Magadi-like mineralization in the lake may have been possible. An identical type of lake, known as "Carapace Lake", also developed in a rift system was located in the coeval Mawson Formation of Antarctica, what suggest that both, Carapace and Chacritas were likely alkaline lakes that had notorious influence of hydrothermal fluids. This type of lacustrine facies

1776-438: The Antarctic Peninsula area found that the "Chon Aike V1-V2" crops out extensively in northeast Patagonia and the southern Antarctic Peninsula, being both regions narrow belts sub parallel to the proto-Pacific margin of Gondwana. A land bridge between SA and continental Antarctica is expected to be present at the time, as the Larsen Basin records a coeval fully terrestrial block Syn-rift megasequence, correlated and connected with

1850-750: The Cañadón Lahuincó and Cañadón Caracoles sections suggest the presence of fluvial (riparian) and coastal lacustrine floras, along with inland dry settings dominated by Conifers, overall in a similar distribution that the one seen in coaeval layers in Australia , as well the Mawson Formation in Antarctica. Data from local cuticles of Araucariaceous and Cheirolepidicaceous conifers have been put under microscope, what can lead to future deeper interpretations of local climate fluctuation. Initial revisions of Brachyphyllum spp. cuticles has led to know

1924-570: The Estheria unit, as bituminous Shales. He found remains of sauropod dinosaurs and floral remains, which led to the suggestion of a referral of this section to the upper middle Jurassic, constraining its known age. In 1949, the unit was referred to the Sierra de Olte Group by J. Frenguelli, who also described some floral remains. It was the team led by Stipanicic that named the Cañadón Asfalto Formation, referred to back then as

1998-663: The Jurassic ones linked with a mixed mosaic of volcanic (was likely linked to the Chon Aike Silicic Large Igneous Province ) and sedimentary rocks (fluvial and lacustrine). The Jurassic section can be correlated with an extensive tectonic regime for the central units in the basin, with also the presence of "pull-apart" models. This "pull-apart" model evolved based on the combined presence of diverse structural and depositional features that include lake-derived layer associated with vaporite horizons and various types of synsedimentary deformation, all with

2072-694: The Lonco Tapial Formation. In the Cañadón Asfalto Fm is found on thin layers of tuffs produced by distal ash falls within the lacustrine layers of the lower Chacritas Member, with the presence of sectors with scarce pyroclastic flows and basaltic flows. The interdigitation between carbonate and volcaniclastic deposits is clearly evident in the surroundings of Estancia Fossatti and in the Navidad Sector. Other Volcanic sectors nearby that may have influenced this formation include

2146-595: The Lower Pliensbachian-Toarcian local NNW-oriented transpressive phase. The Cañadón Asfalto Formation along with the Lonco Trapial Formation , Bajo Pobre and Cañadón Huemules , Marifil , Garamilla , Bahía Laura Volcanic Complex , Quemado Complex , Tobífera and Lemaire Formations in Argentina, Mapple , Brennecke Formations & Ellsworth Land Volcanic Group & indet granitoids in Antarctic Peninsula, are part of

2220-473: The Paleopacific Ocean flooded the basin hosting benthic macroinvertebrate associations in a carbonate-elastic ramp, however, none of the measured transgressions flooded the Cañadón Asfalto Basin (although it is estimated that in the upper Toarcian the coast was very close to Paso de Indios ), although it was influenced by the volcanic events of the latter, as shown by the traces of volcanic tuffs in

2294-1187: The Puesto Almada layers. The Cañadón Asfalto formation represents a continuous inland sector on lacustrine and terrestrial habitats far from the nearest coast. The closest marine settings where recovered at the west in the Chubut Basin , where, for example the Toarcian Mulanguiñeu Formation recovers a diverse record of marine fauna, including index ammonites ( Dactylioceras and Canavaria ), brachiopods (groups Spiriferinida and Terebratulida ), bivalves (families Nuculidae , Nuculanidae , Polidevciidae and Malletiidae ), gastropods (families Eucyclidae , Trochoidea , Pseudomelanoidea , Cirridae , Procerithiidae , etc. ), calcareous tube annelids ( Serpulidae ), gregarious corals ( Montlivaltia ), decapods ( Mecochirus robbianoi ), crinoids ( Pentacrinites ), spines of Echinoidea , leaf remains ( Elatocladus hallei ; Conifers) and traces of bioturbation (ichnogenera Rhizocorallium and Lapispira ), indicating that at this time

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2368-890: The South African Drakensberg Group (Karoo Volcanic Province). This unit belongs to the Patagonia - Antarctic Peninsula sequence, along with the Marifil , Lonco Trapial & Garamilla Formation in Central-Northern Patagonia. They form part of the wider first-stage event (V1) of the Chon Aike Province, proving connection with both areas in the Early Jurassic, with the closest unit in South America being

2442-609: The Subcordilleran & Cordilleran Patagonian Batholiths in the west. The Age of the sediments of the Cañadón Asfalto Formation has been debated for decades. It was initially Piatnitzky in 1939 who noted the over lain position of this sediments over the basement, and suggested possible Jurassic to Earliest Cretaceous age based on regional correlations. In the description of the Cañadón Asfalto Formation in 1968, Stipanicic et al. defined that both Cañadón Asfalto and Los Adobes where of "Dogger" (=middle Jurassic) age. In 1984, there

2516-776: The Toarcian part of the Paso de Indios formation. Beyond this sector, the Ordovic-Devonian North Patagonian Massif and the Deseado Massif gave a montane influence to the deposition of the formation. This can be seen in the so-called "Navidad district section" recovers similar Pb isotopic compositions to the ores found on this massifs. Back in the Early Jurassic the Patagonian region was marked by distinct geological features, including

2590-499: The U-Pb and Lu-Hf zircon datings, the main focus of ongoing work has been on the discovery of new fossil sites like the "Canela" and "A12" sites, and revision of both floral and faunal discoveries of previously discovered ones, especially on the "Queso rallado" site. The Cañadón Asfalto Basin (whose full name is Somuncurá-Cañadón Asfalto rift basin) represents among the most extensive exposure of Jurassic rocks in South America. It limits to

2664-421: The adult in regions like the mandible , pectoral girdle , pelvis and hindlimb , although overall their anatomy is quite similar. The many known specimens help fill in gaps in the anatomy of the genus, such as the forelimb and skull. Parts of the skeleton, like the pectoral girdle, tibia and pubis are more robust, while others, like the forelimb and ischium , are more gracile. The material of Patagosaurus

2738-572: The anterior edge. Where the scapulae and coracoids articulate, the coracoids are thickest, and they become gradually thinner as they gain distance from the scapulae. The younger specimen of Patagosaurus possesses a slightly different morphology of the pectoral girdle, with slightly differing proportions, such as a slightly smaller scapular blade. The coracoids resemble Barapasaurus in shape, and differ from Camarasaurus , although they cannot be directly compared with those of Cetiosaurus . The forelimbs of Patagosaurus are only based on three bones from

2812-528: The appearance of numerous radiometric datings obtained from outcrops from different depocenters: starting in 2007, where a K/Ar age of 170 ±4.4 Ma was obtain for the Las Chacritas Member, followed in 2010 of a younger 147.1 ± 3.3 Ma for the Puesto Almada Member, that was later reassigned to 161 ± 3 Ma by U/Pb dating on zircons in the locality Estancia La Sin Rumbo. Then, in 2013 Cúneo et al. provided

2886-415: The bones of the three genera and all the vertebrates of Las Charcitas member where deposited in between 179 and 178 million years, that is Middle-Late Toarcian. Patagosaurus is almost completely known with many articulated specimens found covering almost all of the skeleton, including parts of the skull. Over twelve specimens have been referred to the species, although some of the material is probably from

2960-672: The bottom of ancient lakes . A common characteristic of lacustrine deposits is that a river or stream channel has carried sediment into the basin. Lacustrine deposits form in all lake types including rift graben lakes, oxbow lakes , glacial lakes, and crater lakes . Lacustrine environments, like seas, are large bodies of water. They share similar sedimentary deposits which are mainly composed of low-energy particle sizes. Lacustrine deposits are typically very well sorted with highly laminated beds of silts, clays, and occasionally carbonates. In regards to geologic time, lakes are temporary and once they no longer receive water, they dry up and leave

3034-457: The considered most controversial datations to date: Toarcian, 176,15 ± 0,12 and 178,766 ± 0,092 Ma at Cerro Bayo and Cerro Cóndor respectively, yet this was initially contested (with 168.2 ± 2.2 Ma for Chacritas member) and Puesto Almada constrained latter in 2017 to 160.3 ± 1.7-158.3 ± 1.3 Ma (Callovian-Oxfordian). In 2016 a depth evaluation of local basement samples on Sanidine yielded the current oldest age, 182,8 ± 0,8 Ma, Early Toarcian. Yet, it

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3108-548: The discovery of zircons near the location of the discovery of Bagualia , allowing a precise dating of the Las Charcitas Member as Middle-Late Toarcian , 178-179 million years. And a more advanced dating constrained the age of the formation as Middle-Late Toarcian, contemporaneous to the Chon Aike volcanic activity, making it a local equivalent to Antarctica's Mawson Formation (Ferrar Volcanic Province) and

3182-404: The end of the third there is an enlargement of the canal, forming a well-defined cavity. Even though the sacrum itself is distinguishing, its sacral ribs resemble Camarasaurus . The sacral vertebrae have a total length of 540 mm (21 in), with the total sacral length being 920 mm (36 in). The pelvic girdle is well preserved and well studied. In the holotype, the pelvic girdle

3256-536: The first layers that can be included within the Cañadón Asfalto Formation, the so-called "Capas de Estheria", recovered in places like the Cañón de Bagual. This layer is associated with plant remains such as Arthrotaxites , which allowed them to be assigned to the Jurassic interval. His works were followed by several authors, including M.A. Flores, who studied the layers in between Chubut River, Sierra Cuadrada and Valle del Sapo in 1948–1957. Flores defined these layers,

3330-618: The formation has been controversial, with uranium-lead dating of the volcanic tuff beds having given various different ages. Recent work has suggested that the base of the formation was formed around 171 Ma, during the upper Aalenian , with the main age for the Lower Las Chacritas Member being around 168 Ma, during the Bajocian , Bathonian and Callovian , while the overlying Puesto Almada Member seems to be around 158 Ma, or Oxfordian in age. But that changed thanks to

3404-521: The fossil he erected the genus Patagosaurus , as well as its type species P. fariasi . The generic name of Patagosaurus comes from the location of its find in Patagonia, and the fact that it is a reptile. The specific name honours Ricardo Farias, on whose land the initial discovery was made. The genus was originally known from an almost complete postcranial skeleton lacking a skull as the holotype , and many referred specimens; however, in 2003 it

3478-429: The genus. A specimen first referred to Patagosaurus in 2003, MPEF-PV 1670 (which includes just a lower jaw), is also very similar to MACN CH 933, and differences can be associated with age, so therefore, MPEF-PV 1670 presumably represents adult cranial material. However, the teeth of MACN CH 934 are very different from those of both lower jaws (MACN CH 933 and MPEF-PV 1670), so it can be identified as another sauropod from

3552-679: The group might reveal different conclusions. In a 2009 revision of Euhelopus , Jeffrey A. Wilson and Upchurch published a joint analysis on primitive eusauropodan relationships. They found that Patagosaurus was in fact not a sister taxon of Cetiosaurus , but instead more basal than the genus, effectively invalidating Cetiosauridae. Their results are shown below: Barapasaurus Omeisaurus Mamenchisaurus Patagosaurus Cetiosaurus Jobaria Atlasaurus Bellusaurus Diplodocoidea Haplocanthosaurus Camarasaurus Brachiosaurus Cedarosaurus Somphospondyli A 2021 study found Patagosaurus to be

3626-670: The influx of water during the wet season. This action creates a prime combination of organic matter, silts and clays to create oil shales or coal deposits. Patagosaurus Patagosaurus (meaning "Patagonia lizard" ) is an extinct genus of eusauropod dinosaur from the Middle-Late Toarcian of Patagonia , Argentina . It was first found in deposits of the Cañadón Asfalto Formation , which date to around 179 to 177  million years ago . Although originally twelve specimens were assigned to

3700-498: The juvenile specimen, and no manual elements are preserved. The humeri are slender and elongate, lacking great proximal and distal expansions. The incomplete deltoid crest , only shows that it was wide, and likely had a projection below and behind. Like the humeri, the radius is slender, and lacks large expansions on either end. On the edge closest to the ulna , the radius possesses a ridge along its edge, which corresponds to where radioulnar ligaments would have attached. The ulna

3774-417: The juvenile. The adult femora are proportionately different from the juvenile, being mostly straighter and more ovoid in cross-section. The femoral head is well preserved, although lacking the greater trochanter . The distal end is rather symmetrical when viewed from behind, with two similarly sized condylar surfaces. In the juvenile, the fourth trochanter is completely in the proximal end. The tibia has

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3848-475: The lacustrine facies suggest a second water filling locally, where a smaller body of water known as "Almada Paleolake" was developed, creating also several coeval wetlands that are more notorious towards the uppermost section. Tuff intrusions are more scarce than in the underlaying section and seem to be derived from ash directly falling into water. Despite its name, the "Almada Fish Fauna", including genera such as Condorlepis groeberi , has been proven to belong to

3922-526: The lake had between arid and sub-humid conditions. Nearby emerged settings have abundant Classopollis spp. , key genera for thermophilic settings, what can suggest the nearby emerged lands had warm and dry conditions. Other species suggest a warm to warm-temperate climate, with markedly seasonal (monsoonal) characteristics that coincide with the presence of the Seasonally Dry Subtropical Biome . Overall this flora, as recovered in

3996-515: The latter genus has less of a concavity and expansion. The teeth also possess marginal denticles on the crown. Based on histological studies, an individual of Patagosaurus would have replaced a tooth every 58 days, similar to 62 days for Camarasaurus , and 34 days for Diplodocus . Most of the postcranial skeleton is known in Patagosaurus . The cervical , caudal and dorsal vertebrae are generally similar to Camarasaurus , although

4070-492: The lower-middle Pliensbachian a subsequent transpressional phase led to structural changes, influencing the stretching of the continental crust and affecting sedimentation patterns in the adjacent environments of the marine Osta Arena and Cañadón Asfalto formations. Contrarily to the underliying Lonco Trapial volcanic units, the ones from the Cañadón Asfalto preserve the remanence acquired during their formation, part of

4144-613: The main mafic sectors of the Chon Aike-Antarctic Peninsula, being one of the largest rhyolitic provinces in the world, what is seen on the abundance of volcanic intrusions in the otherwise lacustine/terrestrial facies of the formation, what can be seen in the hyaloclastite and peperite facies of the Navidad sector, indicators of interaction of lacustrine waters and magmatic sources, that seem to come mostly from local basement rifts. Recent U-Pb geochronology data from

4218-546: The newly carved valley from glacial erosion. As the glacier melts, the valley fills with melt water that creates a glacial lake. Crater lakes can be meteoritic or of the caldera variety. Crater lakes sediments are provided from precipitation runoff descending their steep slopes. Lacustrine deposits have gained more attention recently due to containing valuable source rocks of oil, coal, and uranium. Lacustrine deposits generally provide productive mining conditions but can prove challenging when underground mines are attempted due to

4292-678: The northwest with the Subcordilleran Patagonian Batholith+ Ñirihuau Basin and to the south with the Alto de Cotricó , a structural element that separates it from the San Jorge Gulf Basin. It was developed over a Paleozoic basement, whose composition is dominated by plutonic and metamorphic rocks, that, along the Tria-Jurassic layers are part of a local succession of three megasequences, being

4366-898: The opening of the Weddell Sea and to the migration towards the south of the Antarctic Peninsula , developed in a similar way to the rift seen in the coeval deposits of the Transantarctic Mountains (Specially the Mawson Formation in the Queen Alexandra Rangue). This basin was later affected by a regional contractional phase during the Early Cretaceous (seen in the deposition of the Chubut Group ). Local vulcanism

4440-442: The poor shear strength of clays and silts as well as the amount of moisture often locked in the layers due to a low permeability characteristic of lacustrine deposits. Ephemeral lakes have recently been found to be especially valuable due to their seasonal wetting and drying out characteristic. Between the wet and the dry seasons, there is a time period when organic matter has the perfect opportunity to generate, only to be submerged by

4514-408: The presence of common environmental stress on local conifers during the deposition of the Chacritas member. This member was originally described as being mostly a fluvial transition where the local lacustrine settings disappeared, yet, locations such as Cerro Bandera show that it hosted lacustrine, palustrine, and pedogenic deposits. Alluvial facies are the main indicators of the sediment supply, while

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4588-510: The presence of intercalations of basaltic strata. In this basin, towards the southern sector three microbasins are defined: Cerro Cóndor, Cañadón Calcáreo and Fossati. The rotation of the Chubut Jurassic blocks is documented, yet the lateral components seem to have been linked to oblique extension. The Chubut Province was in the Jurassic part of a local Rift that was a result of the fragmentation of Gondwana , associated in extension with

4662-400: The pubes, and only have a small distal expansion. While the ilia resemble Barapasaurus , and the pubes resemble Lapparentosaurus , the ischia are most similar to Diplodocus and Apatosaurus . The hindlimbs of Patagosaurus are based on scant material, some femora , a tibia and a few nondescript pedal bones. Two femora come from an adult, with a single additional bone known from

4736-419: The same deposit as Patagosaurus . Thus, the taxon only certainly includes PVL 4170, MACN CH 933 and MPEF-PV 1670. Patagosaurus is a sauropod that possessed a general and unspecialized bauplan of being quadrupedal , having an elongate neck, a small head and a very long tail. Therefore, it is similar to Cetiosaurus and other related genera, who possessed the same morphology . It has been estimated that it

4810-472: The south until it face basaltic materials in southern area of Cerro Cóndor, reflected in the flooding of the belt and increased algal fossils. This lake was clearly influenced by the volcanic activity, as well was likely a product of the rifting that the Cañadón Asfalto basin suffered back in the Toarcian. This can be seen on the abundance of chert like the one recovered in modern Lake Magadi in Kenyan section of

4884-474: The taxon, at least one of them may belong to a different genus. Patagosaurus probably lived alongside genera as Piatnitzkysaurus , Condorraptor and Volkheimeria . Since Patagosaurus is known from many specimens, including at least one juvenile, its anatomy and growth are fairly well understood. Both ages exhibit the typical features of a sauropod, a long neck, small head, a long tail and being quadrupedal . The juvenile exhibits features different from

4958-497: The two actual members in 2005, following his 1990's works, and formally called them the lower and upper member. In 2012, these two were respectively named the Las Chacritas Member and the Puesto Almada Member. Recent works such as Cúneo et al. in 2013 have proven that the formation is older than previously thought, and that some of the sections that form the Puesto Almada member belong to the Cañadón Calcáreo Fm. Beyond

5032-524: The unit. In 1979, Bonaparte published the first description of dinosaurian remains from the location, including the sauropods Patagosaurus and Volkheimeria and the theropod Piatnitzkysaurus . Towards the 90s, the Cañadón Asfalto Formation was subdivided into lower and upper sections, with the lower being equivalent to the Puesto Gilbert Formation and the upper coeval with the Cañadón Calcáreo Formation . E.G. Figari established

5106-418: The weight of Patagosaurus to be 7.89 t (7.8 long tons; 8.7 short tons), a smaller estimate than McIntosh's. The skull of Patagosaurus is not very well known, with a 2003 revision by Oliver Rauhut determining only a few jaws are certainly referrable to it, as opposed to nearly the entire skull. MPEF-PV 1670 shows what the morphology of the adult or subadult skull was like, while MACN CH 933 represents

5180-457: Was a more recent dating, the one that fully constrained the fossiliferous sections of Las Chacritas Member to Middle Toarcian age (179,4 ± 0,059 Ma, 179,4 ± 0,13 Ma & 177,2 ± 0,4 Ma), that was supported with the discovery of zircons of the same range in the Bagualia layers (Cañadón Bagual) and in other outcrops, including detailed age constraint in the uppermost level of the member proving

5254-557: Was a work that correlated the unit with the Ferrarotti successions, finding differences with the Cañadón Asfalto and upper layers lumped initially on it, suggesting there can be an Upper Jurassic or Lower Cretaceous distinctive unit. Based on the Microfossils and flora, Toarcian to Callovian was assigned to Las Chacritas member, while Callovian-Tithonian was assigned to the Puesto Almada member. However, this wasn't followed by

5328-408: Was about 16.5 m (54 ft) long and weighed about 7.88 tonnes (7.8 long tons; 8.7 short tons). An earlier estimate by John S. McIntosh and his colleagues in 1997, found that Patagosaurus was approximately 15 m (49 ft) long, and also 9.44 metric tons (9.3 long tons; 10.4 short tons) in weight, similar to the later estimates by Holtz. A 2006 study by Donald M. Henderson calculated

5402-401: Was found that a dentary was referable to the species, so more specimens are probably this taxon. Its skeleton was found near those of Piatnitzkysaurus and Volkheimeria in the layers originally suggested as Callovian - to Oxfordian -aged Patagonian deposits of the Cañadón Asfalto Formation . These layers have been recently re-dated, finding out thanks to advanced zircon datation that

5476-686: Was linked with the Chon Aike Igneous Province , or Chon Aike-Antarctic Province. The Vulcanism was product of initial rifting, what also led to the Karoo-Ferrar (South Africa And Antarctica), where the Early Jurassic facies in Patagonia and Larsen Basin deposited influenced by the pushing the Wedell Sea basin did over the surrounding plates, as can be seen in the similarities between the Sweeney Formation and

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