Territorialidad mbyá-guaraní en el espacio urbano en la comunidad de Lomba do Pinheiro, Porto Alegre : Una experiencia de investigación en la Tekoá Anhetenguá

El territorio y el espacio son claves para comprender la problemática de los pueblos originarios latinoamericanos, pues involucran varias dimensiones de análisis. De esta manera, podemos articular tanto dimensiones materiales (sociales, económicas, etc.) como simbólicas (políticas, cosmológicas, culturales, etc.) de la apropiación del espacio y la construcción de una determinada territorialidad, atendiendo también a los contextos concretos de tensión que las condicionan. El carácter urbano de muchas comunidades originarias, y las transformaciones que ello supone, pueden ser abordados desde una concepción materialista de la cultura, como el enfoque del control cultural de Guillermo Bonfil Batalla. Este estudio de la Tekoá Anhetenguá, la comunidad mbyá-guaraní de Lomba do Pinheiro, en Porto Alegre (Rio Grande do Sul, Brasil), buscará poner en tensión estos elementos en los espacios de socialización concretos, extra e intracomunitarios, en los que se desenvuelven los miembros de la comunidad. Además, se realizará una reflexión política y metodológica sobre la experiencia del trabajo de campo.

Organic matter preservation in turbidites on the Madeira Abyssal Plain

Oxidized intervals of five organic-rich Madeira Abyssal Plain (MAP) turbidites deposited during the Miocene, Pliocene, and Pleistocene all displayed comparable major loss of total organic carbon (TOC) (84 ± 3.1%) accompanied by a negative isotopic (d13C) shift ranging from -0.3 to -2.9 per mil. Major but significantly lower loss of total nitrogen (Ntot, 61 ± 7.1%) also occurred, leading to a decrease in TOC relative to Ntot (C/Ntot) and a +1.3 to 2.7 per mil Ntot isotopic (d15N) shift. Compound specific isotopic measurements on plant wax n-alkanes indicate the terrestrial organic component in the unoxidized deposits is 13C-enriched owing to significant C4 contribution. Selective preservation of terrestrial relative to marine organic carbon could account for the d13C behavior of TOC upon oxidation but only if a 13C-depleted component of the bulk terrestrial signal is selectively preserved in the process. Although the C/Ntot decrease and positive d15N shift seems inconsistent with selective terrestrial organic preservation, results from analysis of a Modern eolian dust sample collected in the vicinity indicate these observations are compatible. Regardless of the specific explanation for these isotopic observations, however, our findings provide evidence that paleoreconstruction of properties such as pCO2 using the d13C of TOC is a goal fraught with uncertainty whether or not the marine sedimentary record considered is 'contaminated' with significant terrestrial input. Nonetheless, despite major and selective loss of both marine and terrestrial components as a consequence of postdepositional oxidation, intensive organic geochemical proxies such as the alkenone unsaturation index, UK'37, appear resistant to change and thereby retain their paleoceanographic promise.