Que es el registro fosil yahoo dating

que es el registro fosil yahoo dating

Aires. [email protected]; [email protected]; [email protected] com Los fósiles son improntas y compresiones halladas en litofacies compuestas principalmente por material tobáceo. . Nuevos registros para la flora cretácica descripta por Halle () en el Lago Online publication date: 1- Jul Interpretación paleoambiental empleando el registro fósil: Formación San Juan Raya, cuenca de Zapotitlán, *[email protected] .. Globose, branching and solitary corals have not been taxonomically studied at present date. Campos s/n, Mossoró, , Rio Grande do Norte, Brazil, [email protected] m-jahn.info; Contribución al conocimiento de los mamíferos fósiles de la República Argentina. Megafauna do Pleistoceno Superior de Sergipe, Brasil: registros . Electron Spin Resonance dating of the Late Quaternary megafauna fossils.

This sandstone package grades into a 19 m thick covered interval probably consisting of mudstone. The top of unit 1 reaches a total thickness of 8. It has intercalations of light brown siltstone beds with a clay-rich matrix. Unit 2 has an erosional basal contact overlain by a 0. Scoyenia trace fossils within the sandstone consist of round, vertical tubes mm in diameter Skolithos Haldeman,as well as sinuous, short tubes along bedding planes Planolites Nicholson, The sandstone fines upward into a 1.

This is followed by greenish grey mudstone with dispersed clasts and vertebrate fragments, with a thickness of 9. The total thickness of unit 2 is Unit 3, with a total thickness of The conglomerate fines upward into 1.

This sandstone grades into a 9. Unit 4 starts with a 1. It grades upward into a 3. Locally, a small lens up to 0.

The unit is capped by a 1. Vertebrate fragments are present throughout unit 4, which has a total thickness of Unit 5 is 8. Soft-weathering concretions within this sandstone contain mm-thick, upward-branching traces probably due to hymenopterids.

This sandstone grades into a 4. Unit 6 has an erosional basal contact and a total thickness of 4. It commences with a 0. High-angle planar and trough cross-bedding are prominent. This bed fines upward into a 0. This is cut by a reddish, medium-grained sandstone with scattered clasts up to 0.

It has a thickness of 0. It is overlain with an erosional contact by sub-unit 6c, a very coarse to coarse, poorly sorted, fining-upward sandstone with scattered, subrounded clasts and low-angle planar cross-lamination, with a thickness of 0. Sub-unit 6d is a 0. Sub-unit 6e is a 0. It grades upward into a 0. This mudstone grades into light greyish green mudstone reaching a thickness of 1.

Geología, Topografía y Minas

Unit 8 consists of yellowish, medium- to coarsegrained, poorly sorted sandstone with a clay-rich matrix. It has a preserved thickness of 1. Higher up on Cerro Cono, the Santa Cruz Formation is unconformably overlain by Plio-Pleistocene basalts, which form the watershed and frontier between Chile and Argentina in this area Fig.

Sandstone and conglomerate petrography Two thin sections were made of a conglomerate and pebbly sandstone, from units 1 and 5, respectively.

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Zircons were separated from the same samples for U-Pb dating. The conglomerate sample ZRLF, unit 1 consists of clast-supported, sub- to well-rounded pebbles up to 60 mm in diameter in a coarse to very coarse sandstone matrix. There is very little cement which is composed of Si, where presentso that the sample has a high porosity.

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The pebbles are composed of quartzite with sutured grain contacts, pure quartz apparently derived from a porphyritic rhyolite, and devitrified glass palagonite with a spherulitic texture.

The pebbly sandstone sample ZRLF, unit 5 is very poorly sorted with sub-angular grains, classifying as a lithic arkose. Pebbles are up to 60 mm in diameter, including fine-grained, well-sorted quartz wacke, metamorphic quartzite with sutured contacts, and chert. The medium- to very coarse-grained sand fraction contains quartz, plagioclase with Karlsbad twins, volcanic rock fragments with plagioclase laths, clinopyroxene including titanaugiteand rare, untwinned and slightly weathered K-feldspar.

The fresh appearance of the plagioclase and volcanic fragments, together with the presence of pyroxene, suggest a relatively short distance of transport from a tectonically active source area rich in newly formed basalts. Like the conglomerate, this rock is also very porous, indicating a high-energy environment where finer sediments such as clay could not settle out. Some pores have a lining or are filled with well-developed zeolite crystals, suggesting low-grade metamorphism.

Depositional environment There can be little doubt that the Santa Cruz Formation in this area was deposited in a continental, fluvial environment, as indicated by the abundance of terrestrial vertebrate fragments, Scoyenia including probable hymenopterid traces, multi-coloured often reddishblocky-weathering mudstones Fig.

Typical sedimentary structures in sandstones of the Santa Crus Formation. Although fossil leaves and wood are absent or at least very rare in the Santa Cruz Formation, a fairly large diversity of microfossil remains have been found, amongst others arthropod appendages and butterfly wing scales, as well as fungi and acritarchs.

que es el registro fosil yahoo dating

Normally, pollen and spores are scarce in oxidized deposits Traverse,but in spite of this we have identified a mixture of herbaceous species, shrubs, tree ferns, and trees, including the families Poaceae Barnhart,Asteraceae Berchtold and Presl,Chenopodiaceae Ventenat,Proteaceae De Jussieu,Nothofagaceae Kuprianova,Podocarpaceae Endlicher,Onagraceae De Ju-ssieu,Myrtaceae De Jussieu,and Cyatheaceae KaulfuB, The lenticular nature of the sandstones, their fine to medium grain-size, relatively small-scale fining-upward cycles, and the presence of epsilon cross-lamination in places suggest deposition on point bars in slightly meandering river channels, as supported by the comparatively thick overbank mudstones.

The Skolithos ichnofacies Seilacher, is normally considered to represent shallow marine deposits, but Skolithos is also characteristic of the shore zones of ephemeral lakes and river f loodplains Frey et al.

Paleocurrent directions were recorded wherever possible, using high-angle planar and trough cross-lamination Fig. The measurements were tilt-corrected by rotating the strikes and dips of the containing strata to the horizontal, using the spreadsheet program of Le Roux Vector mean, magnitude and sinuosity values were subsequently calculated according to the methodology of Le Roux Nevertheless, the first and only mention on the occurrence of fossil mammals in the area was made by Marshall and Salinas bbased on a few fragmentary specimens held in the private collection of the late Mr.

Oscar Vidal, at that time the owner of the Estancia La Cumbre. In that contribution, Marshall and Salinas identified and figured the remains of an astrapotheriid ungulate referred to as Astrapotherium magnumand part of the maxillary of a 'notohippine' 'Notohippidae' considered as an unknown ungulate by the authors fossil identified by E. Bostelmann based on figure 13 of Marshall and Salinas, b. During the last two seasons we collected fossil vertebrates in the Santa Cruz Formation on the southern slopes of Cerro Cono, in a small area of about 0.

All the remains were located between the 1, and 1, m altitude line, forming discrete patches in exposed ravines and buttes, of which the most relevant is Morro Bayo Figs.

The materials are mostly composed of isolated pieces bone fragments, teeth, osteoderms, vertebraeand associated cranial and postcranial elements. Most of the bones were collected on surface having been eroded from soft mudstone, thus lacking a precise stratigraphic position, although field work has shown their occurrence in all the exposed sedimentary units within the column units 1 to 8. A few disarticulated but associated elements were also exhumed in situ from units 5 to 8, including maxillary and mandibular fragments, aggregated teeth, and cranial-postcranial portions.

Morro Bayo, one of the most prominent sites with fossil vertebrates in the Santa cruz Formation al Sierra Baguales.

Generally speaking, the bones present two distinct types of preservation. The vast majority show varied grades of integrity, with angular borders and little mechanical attrition and weathering.

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However, both types of preservation were detected in remains assigned to the most commonly recovered species within the column, leading us to suppose that the provenance of all the materials was relatively proximal. So far, more than specimens belonging to 23 vertebrate species have been identified. Almost all of the remains correspond to terrestrial fossil mammals, for which a preliminary taxonomic classification is given below Table 2Figs.

A detailed assessment of all the materials will be published as a separate paper devoted to the taxonomic identification and regional biostratigraphic context of the fauna. The anatomical terminology used for each of the different taxonomic groups follows the proposed nomenclature of the corresponding references. Quotation marks emphasize informal units or non-monophyletic groups. Among the large mammals collected, the most abundant remains belong to a medium-sized astrapotheriid Order Astrapotheria, Lydekker,from which some isolated teeth i.

This species, easily characterized by its dental morphology, features: Our find extends the geographic distribution of this species in the country by almost 1, km to the south, also making this occurrence the southernmost record for the genus Astrapothericulus. A few large upper canines which exceed the normal mean of a typical medium-sized astrapotheriid i.

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While it is very likely that all these remains also belong to Astrapothericulus, the absence of diagnostic dental elements associated with these fragments prevents their specific identification. Given that the size range of the Sierra Baguales specimens of Astrapothericulus iheringi is slightly above the mean for the genus in northern localities Kramarz,we prefer to be conservative and preliminarily recognize the existence of only one medium-sized species in the deposits.

Nevertheless, it should be emphasized that Early Miocene astrapotheriids include a great diversity of taxa ranging from gigantic to small forms, this being the period of greatest known diversity of the order Kramarz and Bond, Selected specimens of large and medium mammals of the Sierra Baguales fauna.

Astrapothericulus iheringi Ameghino C and D belong to the same individual. A second large taxon is represented by isolated and fragmentary molars i. Due to the disproportionate number of named species within this genus, an exhaustive revision of the more abundant and typological Argentinean materials would be necessary before a specific assignment can be made for the Magallanean specimens.

The Baguales material represents one of the earliest occurrences of the genus Nesodon in the fossil record, otherwise restricted to the 'Pinturan' through Colloncuran ages of Argentina and Chile Ameghino, ; Flynn et al. The fragmentary nature of the type material upon which Ameghino created Notohippus toxodontoides prevents any definitive distinction between both entities, so that a complete revision of these genera will be required to demonstrate their taxonomic validity as partially commented on by Ribeiro and Bond, The Sierra Baguales remains represent the first documented occurrence of Neogene notohippids in the Chileanfossil record, and also the southernmost presence of this paraphiletic 'family' in South America.

Isolated teeth and incomplete hemi-mandibles with their dentitions i. As in the case of Nesodon, Adinotherium represents a classic Santacrucian representative ungulate, quite common in the type sections of the Santa Cruz Formation.

Litopterns in the Sierra Baguales fauna include two different members of the family Proterotheriidae Ameghino The smallest is represented by two isolated upper molars and both dentaries of a young animal CPJLO , and ; Fig. Diagnostic characters observed in the Sierra Baguales specimens include on the upper molars: Our record is the first mention of this genus and species outside the limits of Argentina and obviously the first for Chile.

The second taxon is represented exclusively by a mandibular fragment with one well-preserved molar CPJLO It belongs to a form somewhat larger than Paramacrauchenia scamnata, which is easily distinguished because of the shape of its dental cusps. Although the preserved tooth presents clear characters, a formal generic designation is not recommended due to the fragmentary nature of the material. Selected specimens of medium and small mammals of the Sierra Baguales fauna.

Paramacrauchenia scamnata Ameghino Perimys incavatus Ameghino ; C. Adelphomys candidus Ameghino ; D. Isolated osteoderms in dorsal view. The Superorder Xenarthra Copewhich presently includes sloths, anteaters and armadillos, is represented in the Sierra Baguales fauna by at least two different species of ground sloths, two different armadillos, and one glyptodont Fig.

The identified sloth remains include isolated post-cranial bones such as caudal vertebrae, astragalus, metacarpals, some phalanx i.

Unfortunately, this kind of skeletal element tends to be common within the sloth lineage and does not allow a refined taxonomic characterisation for each of the species, although the dentary and astragalus could be tentatively referred to an undetermined Megalonychidae Gervais The Order Cingulata Illiger armadillos, glyptodonts, and relativesis represented by a small eutatine Dasypodidae Bonaparteof which a mandibular and cranial fragment as well as two dozen isolated osteoderms were collected SGO.

While the general morphology of the teeth and the external ornamentation of the osteoderms suggest a direct resemblance with the genus Proeutatus Ameghino b, the extremely small size -similar to the euphractine Paraeutatus distans Scott distinguishes the Sierra Baguales specimens from all previously known Pansantacrucian species of the genus, suggesting the presence of a new species in the Baguales record.

The second armadillo is represented only by isolated osteoderms CPJLOclearly belonging to a large member of the genus Proeutatus. Curiously, so far we have recovered only three isolated osteoderms of the usually abundant members of the glyptodont subfamily Propalaehoplophorinae Ameghino a, a frequent component in all Early Miocene Patagonian faunas. Rodents are mostly represented in our assemblage by maxillary and mandibular remains of the neo-epiblemid Perimys incavatus Ameghino i.

Some diagnostic characters observed in our materials include: Isolated elements characterize the remaining rodents in the Sierra Baguales fauna. An incomplete upper molar is preliminarily referred to an unspecified member of the superfamily Cavioidea. The extended procotone with a wide anteroloph forming a right angle in its anterio-labial side, the prolonged hypoflexus, short labial flexus and loss of the metafossetes at least in the DP4allow us to recognize this specimen as Adelphomys candidus Ameghino ; a well known monotypic Santacrucian 'adelphomyine' Kramarz, Another small rodent is represented by a partial dentary and some pieces of its incisor enamel band.

Although clearly distinguishable, the fragmented nature of the remains prevents any possibility of a more refined taxonomic identification for this specimen. During our field season inremains of at least 3 different bird species were collected from the Santa Cruz Formation in Sierra Baguales. The most notable is represented by a poorly preserved large bone, potentially belonging to a predatory bird CPJLO If this assignment is confirmed by detailed anatomical studies, this will become the first record of 'terror birds' in Chile.

Sin embargo, el mismo libro dice: Aparecieron caracoles, esponjas, estrellamares, animales parecidos a langostas llamados trilobites, y muchas otras criaturas marinas complejas. Stephen Jay Gould dice: Porque en el mundo viviente de hoy no hay nada que apoye tal idea. Hay una enorme laguna entre los humanos y todo animal existente hoy, incluso la familia de los monos antropomorfos, o antropoides.

La revista Science Digest: En se libro Lucy: The Beginning of humanhind Lucy: Los principios de la humanidadDonald Johanson y Maitland Edey escribieron: No se ha hallado ninguno. Debido a eso, la revista New Scientist declara ahora: Hacen eso hoy, y siempre han hecho eso en el pasado.

Cualesquiera criaturas simiescas que vivieran en el pasado eran precisamente eso -antropoides, o monos- no humanos. Ledyard Stebbins,p. Genetics and the Origin of Species, por Theodosius Dobzhanky,p. Stanley, 4 de febrero dep. The Origin of Species, segunda parte, p.

Processes of Organic Evolution, p. New Scientist, 15 de enero dep. A View of Life, por Salvador E.

Luria, Stephen Jay Gould, Sam singer,p. Red Giant and Write Dwarfs, p. Mind in the Universe, por Robert Jastrow,p. A View of Life, pp.