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Copyright of Cuaternario y Geomorfología is the property of Cuaternario y Geomorfologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Cuaternario y Geomorfología is the property of Cuaternario y Geomorfologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article presents the first result of absolute chronology for Cuban rock art. It mentions that in 2014, specialists from Eastern Michigan University took samples of rock pigments in several Cuban caves for processing and analysis. The results revealed the presence of Bitumen in some paintings, which generated extremely ancient dates that do not correspond to the human occupation of the Antillean Caribbean. However, other samples obtained in the Cave of the Dead yielded dates related to the archaic period of human occupation in Cuba. The upcoming publication of another article is announced, which will reveal the radiocarbon dates obtained for the rock art in the Cachimba Cave in Matanzas. This collaboration between Cuban specialists and Eastern Michigan University represents an advancement in knowledge about Cuban rock art. [Extracted from the article]

We describe a new species of the fossil genus Laurinoxylon from the El Bosque Formation (Eocene), Chiapas, Mexico. The new species is characterized by: diffuse porous wood with indistinct growth rings; solitary vessels and in radial multiples of two to three vessels per radial multiple; simple perforation plates; alternate intervessel pits: septate and non-septate fibers; round vessel-ray parenchyma pits, horizontally and vertically elongated with reduced borders; axial parenchyma scanty paratracheal, vasicentric, apotracheal diffuse; heterogeneous rays, and oil cells associated to the ray parenchyma and among the fibers. This fossil genus has been described before from the Cretaceous to the Neogene, worldwide. This is the first formal record of Laurinoxylon and the first Eocene macrofossil report of Lauraceae from Mexico. This new species supports the hypothesis that the Lauraceae had a wide distribution during the past and that Mexico may be an important region for the diversification of the family as evidenced by its fossil record dating from the Late Cretaceous and by the high number of genera and species that currently grow in Mexico. [ABSTRACT FROM AUTHOR]

The Xitle volcano is part of the Quaternary Chichinautzin volcanic field, located in the southern portion of the Valley of Mexico. The Xitle lavas were emplaced on the archaeological site of Cuicuilco, one of the first urban settlements of the Preclassic period in Mexico. This eruption had a great impact, since it caused great economic and social changes, favoring the consolidation of Teotihuacan as the dominant city in the Valley of Mexico. Available radiometric studies place the age of the eruption between 4000 to 1500 years BP (before present) and there is evidence that Cuicuilco abandonment was due to an eruption between 200 BC (Before Christ) and 200 AD (Anno Domini/after Christ) without exact definition about the age of this event. Therefore, contributing to the accuracy of the age of the eruption continues to be of great interest. The results of new archaeomagnetic dating of rock samples from a sequence of lava flows from Xitle volcano located within the campus of the University of Mexico (UNAM) campus are presented below. A full geomagnetic vector and the field prediction model SHA.DIF.14K were used for such determinations. Two eruptive periods are identified, the first between 1742 and 1491 BC and the second, related to the eruption of Xitle volcano, between 79 BC and 595 AD. The age of the second period is compatible with the hypothesis of gradual abandonment of Cuicuilco and coincides with the accepted ages for the volcano's most important eruptive period. [ABSTRACT FROM AUTHOR]

The characterization of five lithic raw materials identified in the Doncellas locality (Cochinoca Department, Jujuy) is presented, as well as the results of a comparative petrographic analysis of thin sections from eight rock samples. Five of the samples were taken from the primary sources, while the three others are from the archaeological sites: Doncellas (or Agua Caliente de Rachaite), Sayate and Sorcuyo (or Pueblo Viejo de Tucute). The results indicate that while there are two types of volcanic rocks represented (andesites and basalts), the observed variability allows the discrimination of four different groups based on their petrographic characteristics. Starting from the characterization of primary sources, we seek to understand and explain the variability of the artifact assemblages and the supply of local resources. [ABSTRACT FROM AUTHOR]

It is proposed in this note that the oldest terrigenous rocks cropping out in the Tolimán region in the state of Querétaro belong to two different units: El Chilar complex and the San Juan de la Rosa Formation. The first consists of highly deformed siliciclastic turbidites and the second is a volcano-sedimentary succession deposited in marine conditions. The volcanism of the San Juan de la Rosa Formation is felsic in composition and Late Jurassic-Early Cretaceous in age. We postulate as a working hypothesis that the felsic magmatism of the San Juan de la Rosa Formation are part of the Jurassic volcanic arc in central Mexico that migrated in time and space towards the south.? [ABSTRACT FROM AUTHOR]

A semi-quantitative thermochronological study, combining U-Pb and 40Ar/39Ar geochronology, has allowed assessment of the crystallization and cooling history of the Laramide Sierrita Blanca granite as well as the thermal effects resulting from the intrusion into the Mesoproterozoic host rocks (~1.1 Ga Murrieta granite). The U-Pb zircon age discrepancy between two samples of the Sierrita Blanca granite (72.6 ± 1.2 Ma and 69.7 ± 1.0 Ma) could be explained by a process of faster magma cooling in the contact zone with the host Murrieta granite. However, that the Sierrita Blanca granitic unit was made up of multiple intrusions of similar compositions emplaced relatively close in time cannot be discarded. The 40Ar/39Ar ages of both biotite and K-feldspar for the granite collected close to the contact are also significantly older than the ages for the sample collected in a more internal zone of the intrusion. The initial cooling of the Sierrita Blanca granite was fairly fast and monotonous from the closure temperature of zircon to that of biotite (~36-32°C/Ma). Subsequently, the cooling of these Laramide rocks became relatively slow (~10-9°C/Ma) between the closure temperature of biotite and K-feldspar. These estimated cooling rates are similar, perhaps slightly slower, to the ones estimated for other Laramide granitoids in NW Mexico. Three samples of the host Murrieta granite, collected at different distances from the Laramide intrusion, were dated by U-Pb zircon geochronology at ~1.1 Ga, reiterating that the U-Pb zircon systematics are quite resistant to thermal effects inflicted by intrusions like the one in the Sierrita Blanca. However, close inspection of the U-Pb zircon data suggests the presence of Pb loss for some of the zircons. This Pb-loss phenomenon is most pronounced in the zircons from the sample collected at the contact with the Sierrita Blanca intrusive where heat and/or hydrothermal fluids are released by the Laramide intrusion. It is important to note that away from the intrusion-host contact there is a gradual decrease of such thermal effects in the rocks until samples with zircons that show no effects of resetting as suggested by their total U-Pb zircon concordance. This thermal resetting is more prominent in the 40Ar/39Ar systematics of biotite and K-feldspar, since they are totally reset to Laramide ages, including the sample collected the farthest away from the contact. The estimation of post-resetting cooling of biotite and K-feldspar from the host rocks at ~18-15°C/Ma is, in a sense, coherent with the cooling estimates for the same minerals for the Sierrita Blanca granite. This suggests that the general cooling of the Sierrita Blanca after the Laramide intrusion was, for the most part, coherent for the entire area and ended, as expected, in the more internal zones of the Laramide intrusion. Lastly, it is important to point out that the Miocene magmatic pulse present in the Sierrita Blanca and adjacent areas has not caused any thermal disturbance to the Cretaceous or Mesoproterozoic igneous rocks studied in the area. [ABSTRACT FROM AUTHOR]

The Zona Canteras-Puerto Peñasco area, previously known as Seven Hills, is located ~20 km ENE of the town of Puerto Peñasco in NW Sonora, Mexico. Crystalline basement in this area is key to defining Proterozoic provinces of SW Laurentia and has important implications for Phanerozoic tectonics and formation of the active continental margin of North America. New U-Pb zircon ages (LA-MC-ICPMS) of two banded gneisses in this area yield 207Pb/206Pb ages at 1764 ± 3 Ma and 1725 ± 3 Ma. Zircons from both samples are well-behaved in the U-Pb systematics and present age and compositional homogeneity, suggesting that these rocks are Paleoproterozoic orthogneisses. These crystallization ages combined with whole rock major- and trace-element geochemistry and Sm-Nd in whole rock and Lu-Hf isotopic determinations on zircons by laser ablation suggest that the banded gneisses have affinities with rocks of the Yavapai province as defined in the Quitovac area ~45 km to the east and in the region of Gunnison-Salida, Colorado, USA. Both samples plot in the volcanic arc environment of granite formation (Y vs Nb discrimination diagram) and have epsilon Hf (initial) values between +1.85 and +5.05 with corresponding single-stage Hf model ages (TDM) at 1.98-2.07 Ga and two-stage Hf model ages (TDMC) at 2.07-2.50 Ga. Sm-Nd whole rock isotopic analyses from three Paleoproterozoic gneisses have epsilon Nd (initial) values between +1.86 and -0.57 with corresponding Nd model ages (TDM) at 1.91-2.02 Ga. The magmatic protoliths of these gneisses could have been formed mostly from mantle sources with some degree of crustal contribution, which is similar to rocks from the Yavapai province in SW North America. This petrogenesis contrasts with typical Mojave-province rocks that are characterized by significantly greater crustal contamination (as much as 30-40% in Death Valley). If these Mojave province rocks exist in NW Sonora they must be located to the west of the Zona Canteras-Puerto Peñasco area. [ABSTRACT FROM AUTHOR]

Quaternary coastal environments, including estuaries, are significant to archaeologists, geologists, and palaeoecologists because dramatic changes in geographic settings have strongly affected human land use and adaptation. Estuaries are mainly affected by climate and geologic agents like tectonism, subsidence, and isostatic and eustatic sea level changes. This study of Ballona Lagoon, California, located in the Los Angeles metropolitan area, presents the paleoenvironmental reconstruction of an estuary. Estuaries are characterized by diverse assemblages of fishes, ostracodes, molluscs, foraminifers, siliceous organisms (diatoms and silicoflagellates), and traces of vegetation represented by palynomorphs. Ostracode and pollen analyses were conducted in combination with stratigraphic and geochronometric analyses. A central goal of this study was to delineate the lagoon edge and to document how it migrated through time. The location of the lagoon edge was important in determining how and why prehistoric land-use patterns shifted through time. [ABSTRACT FROM AUTHOR]