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Open accessJournal ArticleDOI: 10.7203/SJP.20.1.20547

Estudios palinológicos del grupo Baqueró (Cretácico inferior), provincia de Santa Cruz, Argentina. IX Polen bisacado de podocarpaceae

02 Mar 2021-Vol. 20, Iss: 1, pp 37-56
Abstract: Se describen nueve especies de granos bisacados pertenecientes a la Familia Podocarpaceae, de las cuales tres son especies conocidas, cuatro son nuevas y otras dos quedan sin determinacion especifica por poseer pocos ejemplares. El material analizado pertenece a los generos Podocarpidites Cookson 1947 y Gamerroites Archangelsky 1988 y fue hallado en varias localidades y horizontes estratigraficos de la Formacion Anfi teatro de Tico, Grupo Baquero, Cretacico Inferior (Aptiano) de la provincia de Santa Cruz, Argentina. Se realizo un detallado estudio de los caracteres morfologicos mas destacados del cuerpo y los sacos con el fi n de establecer especies representativas y de facil identificacion taxonomica. Se agregaron comparaciones con ejemplares dispersos de otras procedencias geograficas y estratigraficas. Tambien se comparo con polen hallado en fructificaciones de la Mmisma Formacion. La variedad de material microscopico y megascopico presente en el Aptiano de Patagonia sugiere que la familia Podocarpaceae estuvo mas diversificada, que en la epoca actual. Ello sugiere que Patagonia pudo haber sido uno de los centros de dispersion y diversificacion de la familia en el ambito gondwanico.

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Journal ArticleDOI: 10.1016/J.JSAMES.2013.08.005
Abstract: The Baquero 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 U–Pb zircon age of 118.23 ± 0.09 Ma for a tuff interlayered with fossiliferous rocks of the Anfiteatro de Tico Formation (lower part of the Baquero Group) is reported. This age constrains the duration of deposition of the Baquero 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 Baquero Group allows a better comparison between the paleofloras from this southernmost region.

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Topics: Aptian (55%)

40 Citations


Journal ArticleDOI: 10.1016/J.CRETRES.2012.10.006
Abstract: Variations in the sedimentary organic matter were documented throughout the Agua de la Mula Member (late Hauterivian) of the Agrio Formation, at a combined section in the type area of the Agrio Formation; the base at Agrio del Medio and the middle to top at Bajada del Agrio. A main organic-rich interval was identified in the basal Agua de la Mula Member, dominated by marine-derived Amorphous Organic Matter (AOM), coinciding with the highest Total Organic Carbon (TOC) content, between 1.4 and 3.8 wt.%, suggesting dysoxic conditions. The rest of the Member is predominantly characterized by terrestrially-derived organic matter, mainly phytoclasts, with low TOC values, around 1% or lower, indicating predominantly oxic depositional settings. By integrating stacking pattern and shell beds analysis, four depositional sequences SQ1–SQ4 were recognized. The organic-rich, finely laminated bituminous black shales of the Spitidiscus riccardii zone constitute a mayor and rapid inundation defining a Transgressive System tract (TST), related to a third order asymmetrical mesosequence dominated by a thick High System Tract (HST). It represents the most widespread and important flooding episode within the Neuquen Basin during the late Hauterivian. Inside sequences of higher frequency (SQ1, SQ2, SQ3, SQ4) of probably fourth order were recognized and analysed including several ammonids zones (Spitidiscus riccardii, Crioceratites schlagintweiti, C. diamantensis and Paraspiticeras groeberi). With the exception of the oxygen-controlled, basinal and outer ramp settings indicated for the TST1, which is equivalent to the TST of a lower order sequence, and the lower TST2, respectively, the prevalence of well oxygenated, inner to middle ramp depositional environments, is suggested for the rest of the sedimentary succession and emphasized in HST of SQ2, SQ3 and SQ4. Thus, a shallowing-upward trend with improved oxygenation is recorded through the Agua de la Mula Member, reflected by decreasing TOC, AOM content and preservation state of the organic matter. Based on the whole rock fluorescence analysis of the two selected organic-rich intervals from the Spitidiscus riccardii and the lowermost Crioceratites diamantensis zones, the presence of hydrocarbons suggests a very early in situ generation.

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29 Citations


Journal ArticleDOI: 10.1016/J.CRETRES.2015.11.004
Abstract: The revision of the stratigraphy of the Cerro Bayo in the Bajo Grande area (Argentinean Patagonia) and the new 206Pb/238U age of 116.85 ± 0.26 Ma constrain the dating of the Baquero flora, one of the most abundant Aptian floras of southern Gondwana. This flora, preserved in the Baquero Group, represents an extinct biome that flourished ca. 118 Ma ago and was affected by increasing regional volcanism during the subsequent four millions years. The outcrops of the Cerro Bayo are characterized by fluvio-lacustrine deposits divided into three facies associations that include nine lithofacies. The first palynological record for the locality confirms the correlation of the lower part of the outcrops with the Anfiteatro de Tico Formation (the oldest unit of the Baquero Group). The new radiometric age and stratigraphy support recognition of the Bajo Tigre Formation (the middle unit of the Baquero Group) in the area and date the earliest stage in angiosperm diversification in southern South America. Stratigraphic relationships among the Baquero, Chubut and Divisadero groups are briefly discussed.

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Topics: Aptian (53%)

17 Citations


Open accessJournal Article
08 Aug 2009-Ameghiniana
Abstract: Se determinaron 18 especies de granos de polen de gimnospermas dispersos de la Formacion Kachaike, Cretacico Inferior de la cuenca Austral, provincia de Santa Cruz Las principales familias representadas son las Cheirolepidaceae, Podocarpaceae, Araucariaceae y Ephedraceae Se analizan distintas caracteristicas observadas en los generos Callialasporites Dev y Cyclusphaera Elsik Finalmente se realizan algunas conclusiones generales sobre las diferentes familias de gimnospermas halladas en la Formacion Kachaike

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12 Citations


Journal ArticleDOI: 10.5710/AMGH.31.12.2011.438
19 Dec 2012-Ameghiniana
Abstract: . PALYNOLOGY OF THE GRAN BAJO MEMBER, SAN JULIAN FORMATION (LATE OLIGOCENE) IN ITS TYPE LOCALITY, SANTA CRUZ, ARGENTINA: PALEOENVIRONMENTAL CONSIDERATIONS. The aim of this paper is to present the palynological results from the Gran Bajo Member of the San Julian Formation in its type area (Gran Bajo de San Julian). The studied section crops out in the eastern Santa Cruz Province and has been assigned to the late Oligocene based on 87Sr/86Sr data. The sedimentological analysis suggests a shallow marine environment close to the coast barely influenced by ocean waters at the lower part of the section, which evolved toward a foreshore-shoreface environment at the middle part of the section and to a shoreface-offshore towards the upper part of the section. The palynological assemblages from Gran Bajo section are primarily conformed by terrestrial elements with high preservation stage. A detailed palynological study allowed reconstructing the structure and composition of the forest in relation to deposit...

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10 Citations


References
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20 results found


Open accessBook
01 Jan 1953-
Topics: Pollen (53%)

363 Citations


Open accessBook
01 Jan 1961-
Topics: Cretaceous (52%)

157 Citations




Open accessJournal Article
01 Jan 2002-Ameghiniana
Abstract: The stratigraphy of early Cretaceous strata in the central area of Santa Cruz Province has been a matter of study since the time when E.W. Berry published his first paleobotanical descriptions in 1924. Detailed sedimentological a nd petrographica 1investiga tions performed d uring recent years in the area of Meseta Baquero, Bajo Tigre and Anfiteatro de Tico localities have been added to the available paleontological information. It is now possible to present a new strabgraphic interpretabon of the sequence that has been previously referred to the Baquero Forrnation. This unit is now considered at a higher rank, Baquero Croup, that includes, from bottom to top the fol1owing forrnations: Anfiteatro de Tico, Bajo Tigre and Punta del Barco. The stratotypes for each unit are located and the main lithofacies are described and interpreted. Fossil plant assemblages are placed in this new stratigraphic context and related to paleoenvironments that were strongly influenced by recurrent volcanic ash fal\. A model of paleoenvironmental development and changing geographic sceneries is also discussed. On the basis of paleobotanical and palynological data, a Barremian to Aptian age was previously suggested for the Baquero Group. Recent isotopic datings confirm an Aptian age.

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Topics: Aptian (52%)

50 Citations


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