scholarly journals South American-Antarctic plate motion over the past 50 Myr, and the evolution of the South American-Antarctic ridge

1988 ◽  
Vol 94 (3) ◽  
pp. 377-386 ◽  
Author(s):  
P. F. Barker ◽  
L. A. Lawver
Keyword(s):  
Plate Motion ◽  
South American ◽  
The South ◽  
The Past

scholarly journals A review of the South American genera of Cimbicidae (Insecta, Hymenoptera)

2018 ◽  
Author(s):  
Lars Vilhelmsen ◽  
David R. Smith ◽  
Leonardo A. Malagòn-Aldana
Keyword(s):  
Host Plant ◽  
Human Activity ◽  
Habitat Degradation ◽  
The Other ◽  
Phylogenetic Position ◽  
South American ◽  
Morphological Divergence ◽  
The South ◽  
The Past ◽  
Past Half

The South American genera of the Cimbicidae are reviewed. Five genera and nine species are recognized. Redescriptions of all genera and an identification key to all species are provided. All species are illustrated, including both sexes and aberrant specimens when relevant. The South American Cimbicidae are grouped in the subfamily Pachylostictinae, but there is substantial morphological divergence at the genus level. This and the isolated geographic and phylogenetic position relative to the other subfamilies of Cimbicidae indicates that the Pachylostictinae have evolved in isolation for a substantial amount of time. Host plant records are known for only one species, Pseudopachylosticta subflavata, which is mainly found in the Chacoan subregion. The distribution of the remaining species falls almost exclusively within the range of the Parana subregion forest provinces, a biome that has been much reduced by human activity in the past half millennium. It is likely that these rarely collected wasps are threatened by habitat degradation.

Floristics of the South American Páramo Moss Flora

1990 ◽  
Vol 2 (1) ◽  
pp. 127-132
Author(s):  
Dana Griffin III
Keyword(s):  
South America ◽  
Southern Hemisphere ◽  
Cloud Forest ◽  
South American ◽  
Long Distance Dispersal ◽  
The South ◽  
Long Distance ◽  
Late Pliocene ◽  
Northern Andes ◽  
The Past

The South American paramos appeared in Pliocene times and persist to the present day. The moss flora of this habitat consists of an estimated 400 species that comprise 8 floristic groups. In Venezuela these groups and their percent representation are as follows: neotropical 37%, Andean 26%, cosmopolitan 18%, Andean-African 8%, neotropical-Asiatic 3%, neotropical-Australasian 2%, temperate Southern Hemisphere 2% and northern boreal-temperate 2%. Acrocarpous taxa outnumber pleurocarps by nearly 3:1. The neotropical and Andean floristic stocks likely were present prior to late Pliocene orogenies that elevated the cordillera above climatic timberlines. These species may have existed in open, marshy areas (paramillos) or may have evolved from cloud forest ancestors. Taxa of northern boreal- temperate affinities, including those with Asiatic distributions, probably arrived in the paramos during the Pleistocene, a period which may also have seen the establishment in the Northern Andes of some cosmopolitan elements. Species with temperate Southern Hemisphere and Australasian affinities likely spread first to austral South America thence migrated northward during a cool, moist interval sometime over the past 2.5-3 million years or may have become established in the paramos as a result of long- distance dispersal.

scholarly journals Unenlagiinae revisited: dromaeosaurid theropods from South América

2011 ◽  
Vol 83 (1) ◽  
pp. 163-195 ◽  
Author(s):  
Federico A. Gianechini ◽  
Sebastian Apesteguia
Keyword(s):  
South America ◽  
South American ◽  
The South ◽  
Important Data ◽  
The Past

Over the past two decades, the record of South American unenlagiine dromaeosaurids was substantially increased both in quantity as well as in quality of specimens. Here is presented a summary review of the South American record for these theropods.Unenlagia comahuensis, Unenlagia paynemili, and Neuquenraptor argentinus come from the Portezuelo Formation, the former genus being the most complete and with putative avian features. Neuquenraptor is more incomplete and exhibits pedal features resembling those of Unenlagia. The earliest and most complete South American dromaeosaurid is Buitreraptor gonzalezoru, whose preserved cranial remains, provides important data in the characterization of unenlagiines. The most recently described,Austroraptor cabazai also with cranial remains, allows further comparisons with Laurasian lineages and a better characterization of unenlagiines. The possible synonymy between nenlagia and Neuquenraptor is discussed. Additional evidences from Brazil and Colombia show that dinosaurs with similar dentition to that of unenlagiines were present in the whole South America. However, it is not possible to discart that these remains may belong to other unknown maniraptoran lineages, considering the increasing number of taxa of this group found in South America.

scholarly journals Subduction initiation in the Scotia Sea region and opening of the Drake Passage: when and why?

2021 ◽  
Author(s):  
Suzanna van de Lagemaat ◽  
Merel Swart ◽  
Bram Vaes ◽  
Martha Kosters ◽  
Lydian Boschman ◽  
...  
Keyword(s):  
South America ◽  
Subduction Zone ◽  
Continental Crust ◽  
Drake Passage ◽  
Plate Motion ◽  
South American ◽  
The South ◽  
South American Plate ◽  
Scotia Sea ◽  
The Antarctic

<p>During evolution of the South Sandwich subduction zone, which has consumed South American plate oceanic lithosphere, somehow continental crust of both the South American and Antarctic plates have become incorporated into its upper plate. Continental fragments of both plates are currently separated by small oceanic basins in the upper plate above the South Sandwich subduction zone, in the Scotia Sea region, but how fragments of both continents became incorporated in the same upper plate remains enigmatic. Here we present an updated kinematic reconstruction of the Scotia Sea region using the latest published marine magnetic anomaly constraints, and place this in a South America-Africa-Antarctica plate circuit in which we take intracontinental deformation into account. We show that a change in fracture zone orientation in the Weddell Sea requires that previously inferred initiation of subduction of South American oceanic crust of the northern Weddell below the eastern margin of South Orkney Islands continental crust, then still attached to the Antarctic Peninsula, already occurred around 80 Ma. We propose that subsequently, between ~71-50 Ma, the trench propagated northwards into South America by delamination of South American lithosphere: this resulted in the transfer of delaminated South American continental crust to the overriding plate of the South Sandwich subduction zone. We show continental delamination may have been facilitated by absolute southward motion of South America that was resisted by South Sandwich slab dragging. Pre-drift extension preceding the oceanic Scotia Sea basins led around 50 Ma to opening of the Drake Passage, preconditioning the southern ocean for the Antarctic Circumpolar Current. This 50 Ma extension was concurrent with a strong change in absolute plate motion of the South American Plate that changed from S to WNW, leading to upper plate retreat relative to the more or less mantle stationary South Sandwich Trench that did not partake in the absolute plate motion change. While subduction continued, this mantle-stationary trench setting lasted until ~30 Ma, after which rollback started to contribute to back-arc extension. We find that roll-back and upper plate retreat have contributed more or less equally to the total amount of ~2000 km of extension accommodated in the Scotia Sea basins. We highlight that viewing tectonic motions in a context of absolute plate motion is key for identifying slab motion (e.g. rollback, trench-parallel slab dragging) and consequently mantle-forcing of geological processes.</p>

scholarly journals A review of the South American monsoon history as recorded in stable isotopic proxies over the past two millennia

2012 ◽  
Vol 8 (4) ◽  
pp. 1309-1321 ◽  
Author(s):  
M. Vuille ◽  
S. J. Burns ◽  
B. L. Taylor ◽  
F. W. Cruz ◽  
B. W. Bird ◽  
...  
Keyword(s):  
Time Scales ◽  
North Atlantic ◽  
Large Scale ◽  
Ice Cores ◽  
Ice Age ◽  
South American ◽  
The South ◽  
The Past ◽  
Se Brazil ◽  
Isotopic Proxies

Abstract. We review the history of the South American summer monsoon (SASM) over the past ~2000 yr based on high-resolution stable isotope proxies from speleothems, ice cores and lake sediments. Our review is complemented by an analysis of an isotope-enabled atmospheric general circulation model (GCM) for the past 130 yr. Proxy records from the monsoon belt in the tropical Andes and SE Brazil show a very coherent behavior over the past 2 millennia with significant decadal to multidecadal variability superimposed on large excursions during three key periods: the Medieval Climate Anomaly (MCA), the Little Ice Age (LIA) and the current warm period (CWP). We interpret these three periods as times when the SASM's mean state was significantly weakened (MCA and CWP) and strengthened (LIA), respectively. During the LIA each of the proxy archives considered contains the most negative δ18O values recorded during the entire record length. On the other hand, the monsoon strength is currently rather weak in a 2000-yr historical perspective, rivaled only by the low intensity during the MCA. Our climatic interpretation of these archives is consistent with our isotope-based GCM analysis, which suggests that these sites are sensitive recorders of large-scale monsoon variations. We hypothesize that these centennial-scale climate anomalies were at least partially driven by temperature changes in the Northern Hemisphere and in particular over the North Atlantic, leading to a latitudinal displacement of the ITCZ and a change in monsoon intensity (amount of rainfall upstream over the Amazon Basin). This interpretation is supported by several independent records from different proxy archives and modeling studies. Although ENSO is the main forcing for δ18O variability over tropical South America on interannual time scales, our results suggest that its influence may be significantly modulated by North Atlantic climate variability on longer time scales. Finally, our analyses indicate that isotopic proxies, because of their ability to integrate climatic information on large spatial scales, could complement more traditional proxies such as tree rings or documentary evidence. Future climate reconstruction efforts could potentially benefit from including isotopic proxies as large-scale predictors in order to better constrain past changes in the atmospheric circulation.

scholarly journals A review of the South American Monsoon history as recorded in stable isotopic proxies over the past two millennia

2012 ◽  
Vol 8 (1) ◽  
pp. 637-668 ◽  
Author(s):  
M. Vuille ◽  
S. J. Burns ◽  
B. L. Taylor ◽  
F. W. Cruz ◽  
B. W. Bird ◽  
...  
Keyword(s):  
Time Scales ◽  
North Atlantic ◽  
Large Scale ◽  
Ice Cores ◽  
Ice Age ◽  
South American ◽  
The South ◽  
The Past ◽  
Se Brazil ◽  
Isotopic Proxies

Abstract. We review the history of the South American summer monsoon (SASM) over the past ~2000 yr based on high-resolution stable isotope proxies from speleothems, ice cores and lake sediments. Our review is complemented by an analysis of an isotope-enabled atmospheric General Circulation Model (GCM) for the past 130 yr. Proxy records from the monsoon belt in the tropical Andes and SE Brazil show a very coherent behavior over the past 2 millennia with significant decadal to multidecadal variability superimposed on large excursions during three key periods, the Medieval Climate Anomaly (MCA), the Little Ice Age (LIA) and the Current Warm Period (CWP). We interpret these three periods as times when the SASM's mean state was significantly weakened (MCA and CWP) and strengthened (LIA), respectively. During the LIA each of the proxy archives considered contains the most negative δ18O values recorded during the entire record length. On the other hand the monsoon strength is currently rather weak in a 2000-yr historical perspective, rivaled only by the low intensity during the MCA. Our climatic interpretation of these archives is consistent with our isotope-based GCM analysis, which suggests that these sites are sensitive recorders of large-scale monsoon variations. We hypothesize that these centennial-scale climate anomalies were at least partially driven by temperature changes in the Northern Hemisphere and in particular over the North Atlantic, leading to a latitudinal displacement of the ITCZ and a change in monsoon intensity over the tropical continent. This interpretation is supported by several independent proxy archives and modeling studies. Although ENSO is the main forcing for δ18O variability over tropical South America on interannual time scales, our results suggest that its influence may be significantly modulated by North Atlantic climate variability on longer time scales. Finally our analyses indicate that isotopic proxies, because of their ability to integrate climatic information on large spatial scales, could complement more traditional proxies such as tree rings or historical archives. Future climate reconstruction efforts could potentially benefit from including isotopic proxies as large-scale predictors in order to better constrain past changes in the atmospheric circulation.

scholarly journals The South American Monsoon Variability over the Last Millennium in CMIP5/PMIP3 simulations

2015 ◽  
Vol 11 (6) ◽  
pp. 5651-5681 ◽  
Author(s):  
M. Rojas ◽  
P. A. Arias ◽  
V. Flores-Aqueveque ◽  
A. Seth ◽  
M. Vuille
Keyword(s):  
South America ◽  
Large Scale ◽  
Model Simulation ◽  
Ice Age ◽  
South American ◽  
Last Millennium ◽  
The South ◽  
South American Monsoon ◽  
The Past ◽  
Intercomparison Project

Abstract. In this paper we assess South American Monsoon System (SAMS) variability throughout the Last Millennium as depicted by the Coupled Modelling Intercomparison Project version 5/Paleo Modelling Intercomparison Project version 3 (CMIP5/PMIP3) simulations. High-resolution proxy records for the South American monsoon over this period show a coherent regional picture of a weak monsoon during the Medieval Climate Anomaly period and a stronger monsoon during the Little Ice Age (LIA). Due to the small forcing during the past 1000 years, CMIP5/PMIP3 model simulations do not show very strong temperature anomalies over these two specific periods, which in turn do not translate into clear precipitation anomalies, as suggested by rainfall reconstructions in South America. However, with an ad-hoc definition of these two periods for each model simulation, several coherent large-scale atmospheric circulation anomalies were identified. The models feature a stronger Monsoon during the LIA associated with: (i) an enhancement of the rising motion in the SAMS domain in austral summer, (ii) a stronger monsoon-related upper-troposphere anticyclone, (iii) activation of the South American dipole, which results to a certain extent in a poleward shift in the South Atlantic Convergence Zone and (iv) a weaker upper-level sub tropical jet over South America, this providing important insights into the mechanisms of these climate anomalies over South America during the past millennium.

scholarly journals FROM PORTUGAL TO THE COLONIES: CHARACTERISTICS OF PORTUGUESE EXILES AT THE END OF THE 18TH CENTURY.

2021 ◽  
pp. 54-71
Author(s):  
Liliana Andreia Valente Neves
Keyword(s):  
Comparative Study ◽  
Marital Status ◽  
Social Status ◽  
18Th Century ◽  
Research Work ◽  
South American ◽  
Place Of Birth ◽  
The South ◽  
The Past ◽  
The Times

The exile penalty has been widely used by the portuguese justice over the past centuries. The exiled were forced to cross the Atlantic in the direction of Brazil, Africa and Asia, where they fulfilled the punishment. The constant sending of large human contingents to colonial territories demonstrates the interests that the Crown had in removing the criminals from the metropolis. However, it can be an indicator of other objectives, such as the population and effective possession of the places where they were destined. This reality caused variations in the fate of the exiles according to the times and the needs that the Crown had in different periods. Thus, several authors agree that the sending of exiles to the colonies was aimed at occupation, defence, settlement and contribution to miscegenation in these territories. Through this research work, we seek to carry out a comparative study where we highlight the differences between the sending of exiles to the South American and African colonial territories. We also seek to get to know these individuals seeking to know their social status, profession, crime, age, marital status, place of birth, destination of exile and time of sentence. It was also our intention to analyze how the process of sending these individuals overseas was carried out, the time between the condemnation and their departure, how they were shipped, who was in charge of taking them to their destination and who guaranteed their survival during the trip.

La Violencia in Colombia

1967 ◽  
Vol 9 (4) ◽  
pp. 561-575 ◽  
Author(s):  
Norman A. Bailey
Keyword(s):  
Atlantic Coast ◽  
South American ◽  
Social Phenomenon ◽  
The South ◽  
The Past ◽  
Entire Country

For the past twenty years the South American republic of Colombia has suffered from a social phenomenon of such magnitude that it has defied not only the contemporary jargon of sociologists and political scientists but even the time-honored terminology of insurrection, rebellion, riot and revolution. Perhaps because the only element of this phenomenon that all observers can agree upon is the fact that it is and has been eminently violent, it has come to be called simply “la violencia,” or “The Violence.”The phenomenon known as la violencia never has been completely absent from Colombia since 1946, but it has had two periods of particular virulence, the first between 1948 and 1953 affecting the departments of Tolima, Boyacá, Cundinamarca, Antioquia, Valle, Caldas, Cauca, Santander del Sur, Arauca, Huila, Chocó, Caquetá, Meta, Casanare, Vichada and Bolívar, that is, the entire country with the exception of parts of the Atlantic coast and the southernmost department of Nariño.

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