The Carrizal Formation, exposed in the Marayes-El Carrizal Basin (western Argentina), has been th... more The Carrizal Formation, exposed in the Marayes-El Carrizal Basin (western Argentina), has been the focus of palaeobotanical studies since the late 1800s. The recent finding of well-preserved palynological assemblages provides the first detailed studies about its palynofloras. In this paper, the 63 taxa identified in the unit are illustrated and discussed, as well as their stratigraphic distribution in equivalent palynological assemblages of Argentina. Some spore species are revised: Uvaesporites hammenii (Herbst) Césari, comb. nov., Retusotriletes wielandii (Jain) Césari, comb. nov. and Lundbladispora stellae (Herbst) Césari, comb. nov. The recognition of Cadargasporites baculatus de Jersey & Paten emend. Reiser & Williams, Craterisporites rotundus de Jersey, Enzonalasporites vigens Leschik, Leptolepidites argenteaeformis (Bolkhovitina) Morbey, Protodiploxypinus americus Dunay & Fisher and Rugulatisporites permixtus Playford, among others, appears to be useful for local and interc...
Fossil woods are described and assigned to Cuyoxylon multipunctatus gen. et sp. nov. The woods we... more Fossil woods are described and assigned to Cuyoxylon multipunctatus gen. et sp. nov. The woods were deposited in shales from an interglacial period, and are the first to be described in detail from the Carboniferous glaciation of western Gondwana. They have the primitive characters of Early Carboniferous woods, such as mesarch protoxylem and numerous contiguous pits in an alternate arrangement. They are the oldest fossil woods to have been described from South America. The growth ring characteristics are consistent with a seasonal cool climate.
The palynological analysis of five samples from three levels in cores of the Mallorquin-1 well (P... more The palynological analysis of five samples from three levels in cores of the Mallorquin-1 well (Parana Basin, eastern Paraguay) is presented here. The borehole penetrated the San Miguel Formation, the basal lithostratigraphic unit of the Independencia Group. This palynoflora represents the westernmost palynological record reported from Upper Paleozoic sequences along this basin margin at this latitude. This diverse spore-pollen flora includes several age marker taxa, viz. Verrucosisporites insuetus, Lueckisporites spp., Lunatisporites variesectus, Striatosporites heyleri, Weylandites lucifer, and Tornopollenites toreutos, as well as Reduviasporonites chalastus. The assemblages from the Mallorquin-1 well are assignable to the Lueckisporites virkkiae Zone from the Brazilian sector of the Parana Basin, thus suggesting a Late Cisuralian-Guadalupian age for the section studied and its correlation with the Brazilian Palermo and Irati Formations. Moreover, palynostratigraphic regional corr...
Specimens of a new Iycopod were collected in the Pallero Member of the late Carboniferous- early ... more Specimens of a new Iycopod were collected in the Pallero Member of the late Carboniferous- early Permian Bajo de Veliz Fonnation at the Bajo de Veliz locality (San Luis province). They are undecorticated stems differentiated into sterile and fertile zones, and densely covered by helically disposed microphyles that produced false scars after shedding. Strobilar structures teminally attached to the stems have also been found. Based on these morphological features a possible relationship of this southem Iycopod to the northern family Chaloneriaceae is suggested. This new finding enlarges our knowledge on Gondwana Iycopods, a group scarcely represented in the southern hemisphere.
1 Sección Paleobotánica, Museo Argentino de Ciencias Naturales "Bernardino Rivadavia&... more 1 Sección Paleobotánica, Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", Av. Angel Gallardo 470, C1470DJR Buenos Aires, Argentina. [email protected]. ... 2 Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales, Universidad de ...
A new species ofthe acritarch genus Deusilites is described (D. tenuistriatus). This species, tha... more A new species ofthe acritarch genus Deusilites is described (D. tenuistriatus). This species, that characterizes Lower Permian strata of the Chacoparanense Basin in Argentina and Parana Basin of Brazil, is found in assernblages dominated by continental palynomorphs. lts association with other acritarchs suggests a nearshore marine environment. A taxonomic discussion about similar genera is also presented.
donde han sido reconocidas tres unidades estratigráficas. La basal corresponde a la Formación Cer... more donde han sido reconocidas tres unidades estratigráficas. La basal corresponde a la Formación Cerro Agua Negra (Carbonífero tardío-Pérmico temprano?), formada por areniscas y pelitas depositadas en ambiente marino de plataforma somera y litoral. Sobre ella se dispone la Formación San Ignacio, compuesta por sedimentitas silicoclásticas (desde conglomerados hasta pelitas), calizas estromatolíticas-microbiales, rocas volcánicas, en su mayoría de composición mesosilícica y ácida, y depósitos volcanoclásticos. Estas últimas rocas, probablemente depositadas hacia fines del Carbonífero tardío o en el Pérmico más temprano, cubren en discordancia angular a las de
Lower Carboniferous to Permian palynological zones are described from sections in central-western... more Lower Carboniferous to Permian palynological zones are described from sections in central-western Argentina. In ascending stratigraphic order these zones are: (1) the Cordylosporites-Verrucosisporites (CV) Assemblage Biozone (spanning the Malimán and Cortaderas formations); (2) the Raistrickia densa-Convolutispora muriornata (DM) Assemblage Biozone (which is subdivided into: Sub-biozone A in the Guandacol and equivalent formations, Sub-biozone B in the Tupe Formation and equivalents, and Sub-biozone C in the upper part of the Santa Máxima and El Imperial formations); (3) the Fusacolpites fusus-Vittatina subsaccata (FS) Interval Biozone in the Bajo de Véliz and Tasa Cuna formations and equivalents, and (4) the Lueckisporites-Weylandites (LW) Assemblage Biozone in the De La Cuesta and Yacimiento Los Reyunos formations. The oldest biozone (CV) is assigned to the Early Carboniferous and the overlying DM Biozone to the Late Carboniferous. The uppermost FS and LW biozones are Permian in age. Palynological records show the impact of the Early-to-Late Carboniferous glacial event, which caused significant changes in the composition of the assemblages from this interval. Further studies are necessary to calibrate a regional geological time scale in Gondwana, which is essential for precise correlation.
The continental deposits of the Baqueró Group preserve one of the most abundant Aptian floras on ... more The continental deposits of the Baqueró Group preserve one of the most abundant Aptian floras on the southern margins of Gondwana. These floras represent an extinct biome that was subject to increasing regional volcanism. In combination with the presence of shallow water bodies, this biome provided suitable environments for the preservation of imprints and compressions of foliage together with permineralized trunks and palynofloras. Eight facies associations were identified in nine sections, characterizing the evolution of lacustrine and fluvial environments under intense volcanic activity. In addition, three depositional sequences were defined, with the purpose of establishing a chronostratigraphic framework to which the positions of the fossiliferous levels identified in the different sections can be referred. A 206 Pb/ 238 U age of 114.67± 0.18 Ma from the upper depositional sequence constrains the succession as no younger than the late Aptian and probably represents an interval of 4-5 Myr, during which the vegetation was affected by increasing biotic stress conditions. A qualitative analysis of the palynological assemblages and plant remains allowed a reconstruction of the dynamics of the vegetation developed during the deposition of the Baqueró Group. Volcanic activity appears to have had relatively moderate effects on the biota, at least at the Order level. Nevertheless, low species richness is observed toward the top of the Baqueró Group, reflecting an increase in adverse environmental conditions. The possible interpretations of the assemblages identified as biozones or, in contrast, biofacies related to changeable environmental conditions are discussed herein.
ABSTRACT An anatomical and ecological study of a Late Pennsylvanian–early Permian assemblage of s... more ABSTRACT An anatomical and ecological study of a Late Pennsylvanian–early Permian assemblage of silicified trunks from the San Ignacio Formation of southern Andean Cordillera is detailed. This stratigraphic unit has been divided in three facies associations. The silicified trunks are abundant in the middle part of the facies association C (limestones, shales and volcanics) forming a persistent forested stratigraphic level. Anatomical information integrated with sedimentological data, has allowed reconstruction of a plant community that grew on the westernmost margin of Gondwana. The paleoforest grew in wetland environments, where a taphocoenosis of only permineralized trunks and stumps has been preserved. Based on characters of the stem and roots the trees are cordaitaleans, though distinct from other members of this group. Vascular traces exhibit tracheids arranged in circular patterns indicating auxin regulation of axial growth and probably the presence of epicormic shoots. These fossil trees also preserve anatomical evidence of plant–arthropod interactions and rootlets invading the decaying wood. Indistinct growth rings as well as additional indirect evidence indicate that this ecosystem experienced an overall humid, warm climatic regime.
... presence of a large body of water of brackish to normal marine salinity under glacial conditi... more ... presence of a large body of water of brackish to normal marine salinity under glacial conditions. ... 9. Nonpalinspastic paleogeographic reconstruction of west central Argentina for the Permian (modified from Ldpez Gamundi et al., 1989). ...
ABSTRACT The Baqueró Group is one of the most relevant units regarding the study of the early div... more ABSTRACT The Baqueró Group is one of the most relevant units regarding the study of the early diversification of angiosperms in South America. Whereas the age of the upper part of the Group, namely the Punta del Barco Formation, has been recently dated at 114.67 � 0.18 Ma, the rest of the unit still lacks precise dating. In this contribution a CA-TIMS UePb zircon age of 118.23 � 0.09 Ma for a tuff interlayered with fossiliferous rocks of the Anfiteatro de Ticó Formation (lower part of the Baqueró Group) is reported. This age constrains the duration of deposition of the Baqueró Group to approximately 4 Ma and provides new evidence for the age interpretation of the previously described angiosperm flora and associated pollen assemblages from this unit, until now interpreted as early Aptian or possibly Barremian in age. The Aptian age of the Baqueró Group allows a better comparison between the paleofloras from this southernmost region.
Abstract The Baqueró Group holds a rich fossil flora including macrofloristic and palynological r... more Abstract The Baqueró Group holds a rich fossil flora including macrofloristic and palynological remains that characterize the Early Cretaceous vegetation of Argentina. The age of the upper part of the Group, known as Punta del Barco Formation, has been a topic of several discussions in the past. The type locality of this stratigraphic unit exposes fossiliferous tuffs together with muddy tuffs and tuffaceous sandstones beds. However, there have been no reliable age constraints for the fossil assemblages. 206 Pb/238 U analyses ...
... Abstract. This paper completes the taxonomic description of the recently discovered Permian ... more ... Abstract. This paper completes the taxonomic description of the recently discovered Permian Glossopteristaphofloras from Carapacha Basin and compares its entire paleofloristic assemblage with other known Permian plant associations from Argentina. ...
Plant remains from the Byers Peninsula, South Shetlands Islands, are described. These are leaves ... more Plant remains from the Byers Peninsula, South Shetlands Islands, are described. These are leaves referred to Taeniopteris sp. and female fructi®cations referred to Carnoconites llambiasii Ce Âsari sp. nov. They are considered to belong to the Pentoxylales, originally described from India, Australia and New Zealand. This is the ®rst record of this group of gymnosperms from Antarctica. The occurrence contributes to further differentiation between ¯oras of this part of Gondwana and Laurasia.
Abstract. UPPER PALEOZOIC FROM ARGENTINA: Acomplete FOSSILIFEROUS RECORD IN WESTERN GONDWANA. Thi... more Abstract. UPPER PALEOZOIC FROM ARGENTINA: Acomplete FOSSILIFEROUS RECORD IN WESTERN GONDWANA. Thick Lower Carboniferous up to Permian sequences are recognized in the extensive Argentinian basins. These strata contain varied and abundant ...
60°54'14"-61°13'07"O) - ASPA Nº126 - se encuentra en el extremo occidental de... more 60°54'14"-61°13'07"O) - ASPA Nº126 - se encuentra en el extremo occidental de la isla Livingston en el archipiélago de las islas ... Shetland del Sur. Esta península constituye uno de los lugares más extensos libres de hielo en toda la Antártida. ... (CRETÁCICO) EN ISLA ...
ABSTRACT A new locality where Carboniferous glacial diamictite appears confined to paleovalleys i... more ABSTRACT A new locality where Carboniferous glacial diamictite appears confined to paleovalleys is described in the north of the Argentinian Precordillera. The glacial deposits of the lower part of the Carboniferous Quebrada Larga Formation are divided in three stratigraphic intervals, all of them confined to a paleovalley carved into the granitic and high-grade metamorphic basement. The lower section is composed of different types of massive and stratified diamictite interpreted to record reworking of previously deposited poorly sorted glacial sediments. The middle section comprises shale with dropstones, lenticular beds of diamictite and large-scale cross-bedded sets of sandstone and conglomerate. These rocks represent a more advanced stage of deglaciation that comprises the following succeeding steps: 1) amelioration of the climatic conditions, melting of glaciers, fluvial erosion, 2) the formation of a water body (onset of the fjord system) and 3) a later progradation of Gilbert-type deltas. Diamictite is missing in the upper section, which is chiefly formed by cross-bedded sandstone and conglomerate deposited in braided fluvial plains. A quantitative analysis of palynological assemblages through the sequence allowed a reconstruction of the dynamics of the vegetation developed during the filling of the paleovalley. The presence of monosaccate pollen grains supports an age not older than Serpukhovian and the recognition of the characteristic species of the Raistrickia densa–Convolutispora muriornata Biozone reinforces a late Serpukhovian–Bashkirian age for the assemblages.
The Carrizal Formation, exposed in the Marayes-El Carrizal Basin (western Argentina), has been th... more The Carrizal Formation, exposed in the Marayes-El Carrizal Basin (western Argentina), has been the focus of palaeobotanical studies since the late 1800s. The recent finding of well-preserved palynological assemblages provides the first detailed studies about its palynofloras. In this paper, the 63 taxa identified in the unit are illustrated and discussed, as well as their stratigraphic distribution in equivalent palynological assemblages of Argentina. Some spore species are revised: Uvaesporites hammenii (Herbst) Césari, comb. nov., Retusotriletes wielandii (Jain) Césari, comb. nov. and Lundbladispora stellae (Herbst) Césari, comb. nov. The recognition of Cadargasporites baculatus de Jersey & Paten emend. Reiser & Williams, Craterisporites rotundus de Jersey, Enzonalasporites vigens Leschik, Leptolepidites argenteaeformis (Bolkhovitina) Morbey, Protodiploxypinus americus Dunay & Fisher and Rugulatisporites permixtus Playford, among others, appears to be useful for local and interc...
Fossil woods are described and assigned to Cuyoxylon multipunctatus gen. et sp. nov. The woods we... more Fossil woods are described and assigned to Cuyoxylon multipunctatus gen. et sp. nov. The woods were deposited in shales from an interglacial period, and are the first to be described in detail from the Carboniferous glaciation of western Gondwana. They have the primitive characters of Early Carboniferous woods, such as mesarch protoxylem and numerous contiguous pits in an alternate arrangement. They are the oldest fossil woods to have been described from South America. The growth ring characteristics are consistent with a seasonal cool climate.
The palynological analysis of five samples from three levels in cores of the Mallorquin-1 well (P... more The palynological analysis of five samples from three levels in cores of the Mallorquin-1 well (Parana Basin, eastern Paraguay) is presented here. The borehole penetrated the San Miguel Formation, the basal lithostratigraphic unit of the Independencia Group. This palynoflora represents the westernmost palynological record reported from Upper Paleozoic sequences along this basin margin at this latitude. This diverse spore-pollen flora includes several age marker taxa, viz. Verrucosisporites insuetus, Lueckisporites spp., Lunatisporites variesectus, Striatosporites heyleri, Weylandites lucifer, and Tornopollenites toreutos, as well as Reduviasporonites chalastus. The assemblages from the Mallorquin-1 well are assignable to the Lueckisporites virkkiae Zone from the Brazilian sector of the Parana Basin, thus suggesting a Late Cisuralian-Guadalupian age for the section studied and its correlation with the Brazilian Palermo and Irati Formations. Moreover, palynostratigraphic regional corr...
Specimens of a new Iycopod were collected in the Pallero Member of the late Carboniferous- early ... more Specimens of a new Iycopod were collected in the Pallero Member of the late Carboniferous- early Permian Bajo de Veliz Fonnation at the Bajo de Veliz locality (San Luis province). They are undecorticated stems differentiated into sterile and fertile zones, and densely covered by helically disposed microphyles that produced false scars after shedding. Strobilar structures teminally attached to the stems have also been found. Based on these morphological features a possible relationship of this southem Iycopod to the northern family Chaloneriaceae is suggested. This new finding enlarges our knowledge on Gondwana Iycopods, a group scarcely represented in the southern hemisphere.
1 Sección Paleobotánica, Museo Argentino de Ciencias Naturales "Bernardino Rivadavia&... more 1 Sección Paleobotánica, Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", Av. Angel Gallardo 470, C1470DJR Buenos Aires, Argentina. [email protected]. ... 2 Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales, Universidad de ...
A new species ofthe acritarch genus Deusilites is described (D. tenuistriatus). This species, tha... more A new species ofthe acritarch genus Deusilites is described (D. tenuistriatus). This species, that characterizes Lower Permian strata of the Chacoparanense Basin in Argentina and Parana Basin of Brazil, is found in assernblages dominated by continental palynomorphs. lts association with other acritarchs suggests a nearshore marine environment. A taxonomic discussion about similar genera is also presented.
donde han sido reconocidas tres unidades estratigráficas. La basal corresponde a la Formación Cer... more donde han sido reconocidas tres unidades estratigráficas. La basal corresponde a la Formación Cerro Agua Negra (Carbonífero tardío-Pérmico temprano?), formada por areniscas y pelitas depositadas en ambiente marino de plataforma somera y litoral. Sobre ella se dispone la Formación San Ignacio, compuesta por sedimentitas silicoclásticas (desde conglomerados hasta pelitas), calizas estromatolíticas-microbiales, rocas volcánicas, en su mayoría de composición mesosilícica y ácida, y depósitos volcanoclásticos. Estas últimas rocas, probablemente depositadas hacia fines del Carbonífero tardío o en el Pérmico más temprano, cubren en discordancia angular a las de
Lower Carboniferous to Permian palynological zones are described from sections in central-western... more Lower Carboniferous to Permian palynological zones are described from sections in central-western Argentina. In ascending stratigraphic order these zones are: (1) the Cordylosporites-Verrucosisporites (CV) Assemblage Biozone (spanning the Malimán and Cortaderas formations); (2) the Raistrickia densa-Convolutispora muriornata (DM) Assemblage Biozone (which is subdivided into: Sub-biozone A in the Guandacol and equivalent formations, Sub-biozone B in the Tupe Formation and equivalents, and Sub-biozone C in the upper part of the Santa Máxima and El Imperial formations); (3) the Fusacolpites fusus-Vittatina subsaccata (FS) Interval Biozone in the Bajo de Véliz and Tasa Cuna formations and equivalents, and (4) the Lueckisporites-Weylandites (LW) Assemblage Biozone in the De La Cuesta and Yacimiento Los Reyunos formations. The oldest biozone (CV) is assigned to the Early Carboniferous and the overlying DM Biozone to the Late Carboniferous. The uppermost FS and LW biozones are Permian in age. Palynological records show the impact of the Early-to-Late Carboniferous glacial event, which caused significant changes in the composition of the assemblages from this interval. Further studies are necessary to calibrate a regional geological time scale in Gondwana, which is essential for precise correlation.
The continental deposits of the Baqueró Group preserve one of the most abundant Aptian floras on ... more The continental deposits of the Baqueró Group preserve one of the most abundant Aptian floras on the southern margins of Gondwana. These floras represent an extinct biome that was subject to increasing regional volcanism. In combination with the presence of shallow water bodies, this biome provided suitable environments for the preservation of imprints and compressions of foliage together with permineralized trunks and palynofloras. Eight facies associations were identified in nine sections, characterizing the evolution of lacustrine and fluvial environments under intense volcanic activity. In addition, three depositional sequences were defined, with the purpose of establishing a chronostratigraphic framework to which the positions of the fossiliferous levels identified in the different sections can be referred. A 206 Pb/ 238 U age of 114.67± 0.18 Ma from the upper depositional sequence constrains the succession as no younger than the late Aptian and probably represents an interval of 4-5 Myr, during which the vegetation was affected by increasing biotic stress conditions. A qualitative analysis of the palynological assemblages and plant remains allowed a reconstruction of the dynamics of the vegetation developed during the deposition of the Baqueró Group. Volcanic activity appears to have had relatively moderate effects on the biota, at least at the Order level. Nevertheless, low species richness is observed toward the top of the Baqueró Group, reflecting an increase in adverse environmental conditions. The possible interpretations of the assemblages identified as biozones or, in contrast, biofacies related to changeable environmental conditions are discussed herein.
ABSTRACT An anatomical and ecological study of a Late Pennsylvanian–early Permian assemblage of s... more ABSTRACT An anatomical and ecological study of a Late Pennsylvanian–early Permian assemblage of silicified trunks from the San Ignacio Formation of southern Andean Cordillera is detailed. This stratigraphic unit has been divided in three facies associations. The silicified trunks are abundant in the middle part of the facies association C (limestones, shales and volcanics) forming a persistent forested stratigraphic level. Anatomical information integrated with sedimentological data, has allowed reconstruction of a plant community that grew on the westernmost margin of Gondwana. The paleoforest grew in wetland environments, where a taphocoenosis of only permineralized trunks and stumps has been preserved. Based on characters of the stem and roots the trees are cordaitaleans, though distinct from other members of this group. Vascular traces exhibit tracheids arranged in circular patterns indicating auxin regulation of axial growth and probably the presence of epicormic shoots. These fossil trees also preserve anatomical evidence of plant–arthropod interactions and rootlets invading the decaying wood. Indistinct growth rings as well as additional indirect evidence indicate that this ecosystem experienced an overall humid, warm climatic regime.
... presence of a large body of water of brackish to normal marine salinity under glacial conditi... more ... presence of a large body of water of brackish to normal marine salinity under glacial conditions. ... 9. Nonpalinspastic paleogeographic reconstruction of west central Argentina for the Permian (modified from Ldpez Gamundi et al., 1989). ...
ABSTRACT The Baqueró Group is one of the most relevant units regarding the study of the early div... more ABSTRACT The Baqueró Group is one of the most relevant units regarding the study of the early diversification of angiosperms in South America. Whereas the age of the upper part of the Group, namely the Punta del Barco Formation, has been recently dated at 114.67 � 0.18 Ma, the rest of the unit still lacks precise dating. In this contribution a CA-TIMS UePb zircon age of 118.23 � 0.09 Ma for a tuff interlayered with fossiliferous rocks of the Anfiteatro de Ticó Formation (lower part of the Baqueró Group) is reported. This age constrains the duration of deposition of the Baqueró Group to approximately 4 Ma and provides new evidence for the age interpretation of the previously described angiosperm flora and associated pollen assemblages from this unit, until now interpreted as early Aptian or possibly Barremian in age. The Aptian age of the Baqueró Group allows a better comparison between the paleofloras from this southernmost region.
Abstract The Baqueró Group holds a rich fossil flora including macrofloristic and palynological r... more Abstract The Baqueró Group holds a rich fossil flora including macrofloristic and palynological remains that characterize the Early Cretaceous vegetation of Argentina. The age of the upper part of the Group, known as Punta del Barco Formation, has been a topic of several discussions in the past. The type locality of this stratigraphic unit exposes fossiliferous tuffs together with muddy tuffs and tuffaceous sandstones beds. However, there have been no reliable age constraints for the fossil assemblages. 206 Pb/238 U analyses ...
... Abstract. This paper completes the taxonomic description of the recently discovered Permian ... more ... Abstract. This paper completes the taxonomic description of the recently discovered Permian Glossopteristaphofloras from Carapacha Basin and compares its entire paleofloristic assemblage with other known Permian plant associations from Argentina. ...
Plant remains from the Byers Peninsula, South Shetlands Islands, are described. These are leaves ... more Plant remains from the Byers Peninsula, South Shetlands Islands, are described. These are leaves referred to Taeniopteris sp. and female fructi®cations referred to Carnoconites llambiasii Ce Âsari sp. nov. They are considered to belong to the Pentoxylales, originally described from India, Australia and New Zealand. This is the ®rst record of this group of gymnosperms from Antarctica. The occurrence contributes to further differentiation between ¯oras of this part of Gondwana and Laurasia.
Abstract. UPPER PALEOZOIC FROM ARGENTINA: Acomplete FOSSILIFEROUS RECORD IN WESTERN GONDWANA. Thi... more Abstract. UPPER PALEOZOIC FROM ARGENTINA: Acomplete FOSSILIFEROUS RECORD IN WESTERN GONDWANA. Thick Lower Carboniferous up to Permian sequences are recognized in the extensive Argentinian basins. These strata contain varied and abundant ...
60°54'14"-61°13'07"O) - ASPA Nº126 - se encuentra en el extremo occidental de... more 60°54'14"-61°13'07"O) - ASPA Nº126 - se encuentra en el extremo occidental de la isla Livingston en el archipiélago de las islas ... Shetland del Sur. Esta península constituye uno de los lugares más extensos libres de hielo en toda la Antártida. ... (CRETÁCICO) EN ISLA ...
ABSTRACT A new locality where Carboniferous glacial diamictite appears confined to paleovalleys i... more ABSTRACT A new locality where Carboniferous glacial diamictite appears confined to paleovalleys is described in the north of the Argentinian Precordillera. The glacial deposits of the lower part of the Carboniferous Quebrada Larga Formation are divided in three stratigraphic intervals, all of them confined to a paleovalley carved into the granitic and high-grade metamorphic basement. The lower section is composed of different types of massive and stratified diamictite interpreted to record reworking of previously deposited poorly sorted glacial sediments. The middle section comprises shale with dropstones, lenticular beds of diamictite and large-scale cross-bedded sets of sandstone and conglomerate. These rocks represent a more advanced stage of deglaciation that comprises the following succeeding steps: 1) amelioration of the climatic conditions, melting of glaciers, fluvial erosion, 2) the formation of a water body (onset of the fjord system) and 3) a later progradation of Gilbert-type deltas. Diamictite is missing in the upper section, which is chiefly formed by cross-bedded sandstone and conglomerate deposited in braided fluvial plains. A quantitative analysis of palynological assemblages through the sequence allowed a reconstruction of the dynamics of the vegetation developed during the filling of the paleovalley. The presence of monosaccate pollen grains supports an age not older than Serpukhovian and the recognition of the characteristic species of the Raistrickia densa–Convolutispora muriornata Biozone reinforces a late Serpukhovian–Bashkirian age for the assemblages.
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