scholarly journals Provenance and Paleoenvironmental Studies of Cretaceous African and South American Kaolins: Similarities and Differences

Minerals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1074
Author(s):  
Olaonipekun Oyebanjo ◽  
Nenita Bukalo ◽  
Georges-Ivo Ekosse

The African and South American continents are of great interest in continental drift studies. Hence, this study assesses the possible correlations in the provenance and paleoenvironment of selected Cretaceous Nigerian and Cameroonian (in Africa), and Argentine and Brazilian (in South America) kaolins through an analysis of their mineralogical and geochemical characteristics. On the basis of their mineralogical composition, the Nigerian Lakiri and Brazilian soft Capim River kaolins are predominantly characterised as pure kaolins, whereas the kaolins from Cameroon (except for Yatchika) and Argentina are mainly considered as sandy kaolins. The present study revealed that the Brazilian soft Capim River kaolin had the highest kaolinite structural order, whilst the Argentine Santa Cruz kaolin had the least. The kaolins from Nigeria, Cameroon, and Argentina were dominated by subhedral to anhedral kaolinite crystals relative to the Brazilian kaolin, which possess more euhedral kaolinite crystals. The kaolins were formed by the intense weathering of intermediate to felsic rocks under anoxic conditions, which is consistent with the structural framework of the basins. The average paleotemperatures obtained for the kaolins (except for the one from Santa Cruz) indicates that the paleoweathering took place under tropical climates.

Zootaxa ◽  
2020 ◽  
Vol 4885 (4) ◽  
pp. 487-508
Author(s):  
AFONSO H. LEAL ◽  
ANTONIO J. CREÃO-DUARTE ◽  
GABRIEL MEJDALANI

Scopogonalia is a leafhopper genus with 17 described species, all of them from South America. In this work, a phylogenetic analysis of the genus was conducted based on 59 morphological and colour pattern characters of head, thorax, abdomen, male and female genitalia. Analyses with equal weights resulted in 12 equally most parsimonious trees (length = 137) including a monophyletic Scopogonalia in all of them. An implied weights (k = 15) analysis recovered two trees, one of them equal to the one obtained with a single round successive weighting procedure, which was chosen for discussion. The trees support the existence of three main clades, which are here called Early Green Clade, Late Green Clade, and Yellow-Brown Clade. The origin and diversification of each clade is discussed under available biogeographical knowledge of South America. Little variation was observed in the female genitalia, but their characters were useful to reinforce the monophyly of the Yellow-Brown Clade, which we associate to ecological adaptations. This clade supports a past connection of the Cerrado biome and savannah enclaves in Amazonia and Atlantic Forest. This conclusion highlights the necessity of conserving this open vegetation environment inside the most fragmented portion of the Atlantic Forest, in northeastern Brazil. 


Author(s):  
Javier A. Vadell ◽  
Clarisa Giaccaglia

The roots of Latin American regionalism blend together with the birth of the region’s states, and despite its vicissitudes, the integrationist ideal represents the most ambitious form of regional feeling. It is an ancient process that has undergone continuous ups and downs as a result of domestic and foreign restrictions. In the early 21st century, the deterioration of the “open regionalism” strategy, along with the rise to power of diverse left governments, led to the development of a “physical-structural,” “post-liberal,” “post-neoliberal,” or “post-hegemonic” integration model. In this context, Brazil—governed by Luiz Inácio Lula da Silva—constituted itself as a crucial protagonist and main articulator of the South American integrationist project. From this perspective, in addition to the existing MERCOSUR, UNASUR was created, and it encompassed the whole subcontinent, thus reaffirming the formulation of regional policies regarding the concept of “South America.” At present, however, a new stage of these regionalisms has started. Today, the Latin American and Caribbean dynamics seem to bifurcate, on the one hand, into a reissue of open regionalism—through the Pacific Alliance—and, on the other hand, into a fragmentation process of South America as a geopolitical bloc and regional actor in the global system. Regarding this last point, it is unavoidable to link the regional integration crisis to the critical political and economic situation undergone by Brazil, considered as the leader of the South American process. In short, the withdrawal of the Brazilian leadership in South America, along with the shifts and disorientations that took place in UNASUR and MERCOSUR, have damaged the credibility of the region’s initiatives, as well as the possibility to identify a concerted voice in South America as a distinguishable whole. That regional reality poses an interesting challenge that implies, to a great extent, making a heuristic effort to avoid being enclosed by the concepts and assumptions of the processes of regionalism and integration that were born to explain the origin, evolution, and development of the European Union. From this perspective, the authors claim that the new phase experienced by Latin American regionalisms cannot be understood as a lack of institutionality—as it is held by those perspectives that support the explanations that they “mirror” the European process—but rather it answers chiefly to a self-redefinition process influenced by significant alterations that occurred both in global and national conjunctures and that therefore, have had an impact on the regional logic. Given the regional historical tradition marked by vicissitudes, the authors believe that they can hardly talk about a “Sudamexit” (SouthAmexit in English) process, namely, an effective abandonment of regionalisms. Recognizing the distinctive features of Latin American and Caribbean countries, rather, leads us to think of dynamics that generate a complex and disorganized netting in which the political-institutional course of development of Brazil will have relevant repercussions in the future Latin American and Caribbean process as a whole.


2017 ◽  
Vol 38 (1) ◽  
pp. 15-30 ◽  
Author(s):  
Adriana Albino ◽  
Santiago Brizuela ◽  
Sergio Vizcaíno

Squamates form a substantial part of the present-day South American herpetofauna, and their fossils constitute an indispensable evidence for understanding the origin and evolution of the main taxa. Squamates are relatively common in Miocene localities of Patagonia, especially in levels of the late early Miocene Santa Cruz Formation. In this contribution, remains of the three species of the extinct iguanidErichosaurusAmeghino 1899 (E. diminutus,E. bombimaxillaandE. debilis) are redescribed, and new squamate specimens are reported for first time. The genusErichosaurusis considered invalid.Erichosaurus debilis,E. diminutusand a new specimen are recognized as indeterminate species of the extant polichrotinePristidactylus, whereasE. bombimaxillaremains as an indeterminate iguanid. Snakes are represented by an indeterminate colubrid. All these specimens, together with a tupinambine teiid previously described for the same formation, represent the southernmost fossil record of squamates in South America and indicate the occurrence of the iguanidPristidactylus, the teiidTupinambisand the colubrid snakes south to their present distribution as back as during the early Miocene.


Zootaxa ◽  
2008 ◽  
Vol 1858 (1) ◽  
pp. 37
Author(s):  
MARCELA L. MONNÉ ◽  
MIGUEL A. MONNÉ

A key to the genera of South American Lepturini and keys to the South American species of Cyphonotida, Euryptera, Lycochoriolaus, Megachoriolaus and Strangalia are provided. Megachoriolaus clarkei Monné & Monné new species is described from Brazil (Rondônia) and Bolivia (Santa Cruz). The following new synonymies are proposed: Euryptera latipennis var. virgata Gounelle, 1911 and Euryptera brasiliensis Fuchs, 1956 = Euryptera latipennis Lepeletier & Audinet-Serville, 1828; Euryptera rotundipennis Fuchs, 1956 = Lycochoriolaus angustatus (Melzer, 1935). The following species are transferred from Euryptera: Lycochoriolaus ater (Gounelle, 1911) new combination, Megachoriolaus atripennis (Bates, 1870) new combination, M. bicolor (Gounelle, 1911) new combination and M. venustus (Breme, 1844) new combination. Lectotype designations are proposed for the following species: Euryptera leonina Gounelle, 1911, Euryptera latipennis var. virgata Gounelle, 1911 and Euryptera bicolor Gounelle, 1911.


Zootaxa ◽  
2012 ◽  
Vol 3478 (1) ◽  
pp. 192-200
Author(s):  
MIGUEL A. MONNÉ ◽  
MARCELA L. MONNÉ

New species of South American Acanthocinini are described: Neobaryssinus abbreviatus sp. nov. from French Guianaand Brazil (Amazonas); Baryssinus amoenus sp. nov. from French Guiana; Colobeutrypanus barclayi sp. nov. fromEcuador; Sporetus sticticus sp. nov. from Ecuador, French Guiana and Brazil (Pará); Oxathres simillima sp. nov. fromVenezuela; Oxathres griseostriata sp. nov. from Brazil (Maranhão) and Bolivia (Santa Cruz) and Oedopeza tavakiliani sp. nov. from French Guiana.


2018 ◽  
Vol 285 (1870) ◽  
pp. 20172012 ◽  
Author(s):  
Darin A. Croft ◽  
Russell K. Engelman ◽  
Tatiana Dolgushina ◽  
Gina Wesley

This study investigates whether terrestrial mammalian carnivore guilds of ancient South America, which developed in relative isolation, were similar to those of other continents. We do so through analyses of clade diversification, ecomorphology and guild structure in the Sparassodonta, metatherians that were the predominant mammalian carnivores of pre-Pleistocene South America. Body mass and 16 characters of the dentition are used to quantify morphological diversity (disparity) in sparassodonts and to compare them to extant marsupial and placental carnivores and extinct North American carnivoramorphans. We also compare trophic diversity of the Early Miocene terrestrial carnivore guild of Santa Cruz, Argentina to that of 14 modern and fossil guilds from other continents. We find that sparassodonts had comparatively low ecomorphological disparity throughout their history and that South American carnivore palaeoguilds, as represented by that of Santa Cruz, Argentina, were unlike modern or fossil carnivore guilds of other continents in their lack of mesocarnivores and hypocarnivores. Our results add to a growing body of evidence highlighting non-analogue aspects of extinct South American mammals and illustrate the dramatic effects that historical contingency can have on the evolution of mammalian palaeocommunities.


2008 ◽  
Vol 21 (1) ◽  
pp. 39 ◽  
Author(s):  
Michael Stech ◽  
Tanja Pfeiffer ◽  
Wolfgang Frey

Plastid trnT–F and atpB–rbcL spacer sequences as well as AFLP fingerprints are utilised to infer phylogenetic relationships of Dendroligotrichum and Polytrichadelphus taxa (Polytrichaceae) in the palaeoaustral region. Phylogenies based on DNA sequence data support the monophyly of each genus. Relationships within Dendroligotrichum remain ambiguous owing to low sequence divergence. AFLP fingerprinting, however, allows a clear distinction of all included Dendroligotrichum and Polytrichadelphus taxa at the species level. The morphological, distributional, ecological and molecular differences justify the recognition of the following three species in Dendroligotrichum: D. dendroides (Brid. ex Hedw.) Broth. and D. squamosum (Hook.f. & Wilson) Cardot in southern South America, as well as D. microdendron (Müll. Hal.) G.L.Sm. in New Zealand; and the following two species in Polytrichadelphus: P. magellanicus (Hedw.) Mitt. s.str. in southern South America and P. innovans (Müll. Hal.) A.Jäger in Australia and New Zealand. For Polytrichadelphus, the molecular topologies correspond with a vicariance scenario, with a basic split of taxa in the palaeoaustral region followed by migration of southern South American taxa northwards into the Neotropics. In Dendroligotrichum, substitutions and indels in the trnL intron and atpB–rbcL spacer are ambiguous in supporting either a basic split between the South American species and D. microdendron, similar to the one in Polytrichadelphus, or a trans-oceanic dispersal event between New Zealand and southern South America.


The considerable palaeomagnetic data from the Gondwanic continents, Africa, Antarctica, Australia, India and South America, are critically examined and shown to support the hypothesis of continental drift. Palaeomagnetic latitudes for Australia, traced by Irving and his colleagues from the late Precambrian to Recent times, indicate that Australia was near the equator in the Devonian and close to the Pole during the Permo-Carboniferous. During the Mesozoic and Tertiary it drifted northwards to its present position. Gough and his colleagues in Southern Rhodesia have recently concluded that since the middle of the Mesozoic the palaeomagnetic latitude of Africa has remained appreciably unchanged, but they find evidence of a marked drift northwards to its present latitudes from polar latitudes during the Permian and early Mesozoic. From my own studies of South American rocks I have deduced that there has been little movement of South America relative to the pole since the Triassic-Jurassic, but that a sharp change in magnetic latitude took place during the Lower and Middle Permian. Results from Devonian and Silurian rocks indicate that in those times northeast Brazil was closer to the pole than Tierra del Fuego. The movement of South America relative to the pole during the Permian was thus a continuation of an Upper Palaeozoic polar shift. In the Triassic-Jurassic, basaltic lavas and diabase dykes were extruded and intruded into parts of all the Gondwanic continents. Palaeomagnetic studies have been made on these rocks from all five continents. The palaeolatitudes and palaeoazimuths so deduced are consistent neither with the present positions of these continents, nor with the suggestion that they were then adjacent to one another. A possible reconstruction satisfying the restrictions imposed by the palaeomagnetic data shows these continents occupying positions between those suggested by geologists for the PermoCarboniferous and their present positions, and it is inferred that the continents as we know them today had separated and had started moving towards their present positions when this igneous activity occurred. For the Palaeozoic era reliable palaeomagnetic data have, as yet, been obtained only for the Devonian, Silurian and Cambrian of Australia and South America. There is one not very well established Silurian result for South Africa. The consistency of these data with reconstructions of Gondwanaland based on geology is examined. Both du Toit’s and J. T. Wilson’s reconstructions are considered.


2021 ◽  
Author(s):  
Alexis M. Aranciaga Rolando ◽  
Matias J. Motta ◽  
Federico L. Agnolín ◽  
Makoto Manabe ◽  
Takanobu Tsuihiji ◽  
...  

Abstract Megaraptorans are a theropod clade distributed in former Gondwana landmasses and Asia. Most members of the clade are known from early Cretaceous to Turonian times whereas Maastrichtian megaraptorans are known just from isolated and poorly informative remains. The aim of present contribution is to describe a partial skeleton of a megaraptorid coming from Maastrichtian beds at Santa Cruz province, Argentina. This new taxon constitutes the most informative megaraptoran from post-Turonian beds. Phylogenetic analysis nested the new taxon together with South American megaraptorans in a monophyletic clade, whereas Australian and Asian members constitute successive stem groups. South American forms differ from more basal megaraptorans in several anatomical features and in being much larger and more robustly built. It is possible that the Cenomanian-Turonian extinction of carcharodontosaurids was allowed to megaraptorans to occupy the niche of top predators in South America.


2004 ◽  
Vol 359 (1450) ◽  
pp. 1595-1610 ◽  
Author(s):  
Robyn J. Burnham ◽  
Kirk R. Johnson

Extant neotropical rainforest biomes are characterized by a high diversity and abundance of angiosperm trees and vines, high proportions of entire–margined leaves, high proportions of large leaves (larger than 4500 mm 2 ), high abundance of drip tips and a suite of characteristic dominant families: Sapotaceae, Lauraceae, Leguminosae (Fabaceae), Melastomataceae and Palmae (Arecaceae). Our aim is to define parameters of extant rainforests that will allow their recognition in the fossil record of South America and to evaluate all known South American plant fossil assemblages for first evidence and continued presence of those parameters. We ask when did these critical rainforest characters arise? When did vegetative parameters reach the level of abundance that we see in neotropical forests? Also, when do specific lineages become common in neotropical forests? Our review indicates that evidence of neotropical rainforest is exceedingly rare and equivocal before the Palaeocene. Even in the Palaeocene, the only evidence for tropical rainforest in South America is the appearance of moderately high pollen diversity. By contrast, North American sites provide evidence that rainforest leaf physiognomy was established early in the Palaeocene. By the Eocene in South America, several lines of evidence suggest that neotropical rainforests were diverse, physiognomically recognizable as rainforest and taxonomically allied to modern neotropical rainforests. A mismatch of evidence regarding the age of origin between sites of palaeobotanical high diversity and sites of predicted tropical climates should be reconciled with intensified collecting efforts in South America. We identify several lines of promising research that will help to coalesce previously disparate approaches to the origin, longevity and maintenance of high diversity floras of South America.


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