18 resultados para intercalated clays
Resumo:
A new species of terrestrial gastropod - Anadromus penai sp. nov. (Fam. Anadromidae) - is described from a set of composite moulds collected in reddish silts and clays of Campanian-Maastrichtian age, found in the lower pan of the Taveiro Formation (Taveiro, Coimbra, West Central Portugal). The known occurrences of this new species are restricted to the type locality. The main differences from other contemporaneous Anadromidae are the profuse spiral sculpture of the body-whorl, with 20-22 sub-equal, close, and regular ribs.
Resumo:
In the aim of the project "Recognition of the Miocene of the distal region of the Lower Tagus Basin through a borehole with continuous sampling", Temperature, Natural Gamma Ray, Neutron (almost in all the borehole), Sonic, SP and SPR (in two small sections in upper and lower parts of the Miocene Series) geophysical logs were carried on. Interpretation of those logs and comparison with chronological, lithostratigraphical, micropaleontological and clay mineraIs data; helped in the definition of depositional sequences and to obtain paleoenvironmental reconstructions that could lead to a better understanding of the evolution of the Setúbal Península and Lisboa regions Miocene gulf. Log data agree with the lithologic succession observed in the Belverde borehole, essentially silty sandstones/sandy siltstones (with variable clay content) to clays, often with marly intercalations. Sonic logs (and Neutron logs, in general) reflect the sediments porosity. The higher acoustic velocities are often related to compact/massive layers as claystones and/or limestones and rather fossiliferous marly layers. Lower values are obtained for porous, silty sandstones (fossiliferous and with scarce clay content) and bio-calcareous sandstones. As indicative, we obtained the mean values of 2500-3000m/s for the higher velocities and 1300-1600m/s for the lowest ones. ln Natural Gamma Ray log, the radiation peaks can be correlated to often fossiliferous marly micaceous layers. Radioactive micas are present. It seems that the gamma peaks and the depositional sequences previously defined for the Lower Tagus Basin (see Antunes et al., 1999, 2000; Pais et al., 2002) can be correlated, taking also into account the whole available micropaleontological, palynological and isotopic evidence.
Resumo:
Mesoamerican cultures had a strong tradition of written and pictorial manuscripts, called the codices. In studies already performed it was found the use of Maya Blue, made from a mixture of indigo and a clay called palygorskite, forming an incredibly stable material where the dye is trapped inside the nanotubes of the clay, after heating. However, a bigger challenge lies in the study of the yellows used, for these civilizations might have used this clay-dye mixture to produce their yellow colorants. As a first step, it was possible to provide identification, by non-invasive methods, of two colorants (a flavonoid and a carotenoid). While the flavonoid absorbed between 368-379 nm, the carotenoid would absorb around 455 nm. A temperature study also conducted allowed to set 140ºC as the desirable temperature to heat the samples without degrading them. FT-IR, conventional Raman and SERS allowed us to understand the existence of a reaction between the dyes and the clays (palygorskite and kaolinite), however it is difficult to understand it in a molecular point of view. As a second step, five species of Mexican dyes were selected on the basis of historical sources. The Maya yellow samples were produced adapting the recipe proposed by Reyes-Valerio, supporting the yellow dyes extracted from the dried plants on the clays, with addition of water, and then heated at 140ºC. It was found that the addition of water in palygorskite would increase the pH, hence deprotonating the molecules having a clear negative effect in the color. A second recipe was developed, without the addition of water; however, it was found that the use of water based binders would still alter the color of the samples with palygorskite. In this case, kaolinite without heating yield better results as a Maya yellow hybrid. It was found that the Maya chemistry might not have been the same for all the colors. The Mesoamericans might have found that different dyes could work better to their desires if matched with different clays. It was noticeable that for a clear distinction between flavonoids and carotenoids the reflectance and emission studies suffice, but when clay is added, Raman techniques will perform better. For this reason, conventional Raman and SERS were employed in order to create a database for the Mesoamerican dyestuffs for a future identification.