New explorations in the desert of northeastern Zacatecas, in central-northern Mexico, revealed dozens of archaeological and geoarchaeological sites. One of them, Ojo de Agua, contains the remains of a Pleistocene spring-fed hydrographic system located at the southeastern end of a large elongated endorheic basin. The locality yielded a particularly dark, highly organic stratigraphic layer commonly known in the Americas as Black Mat (BM), exposed on the natural profiles of a creek, but not associated with cultural materials. Several radiocarbon assessments confirmed the formation of the Ojo de Agua Black Mat during the Younger Dryas chronozone, with ten calibrated results clustering between 12,700–12,100 cal BP. This multi-proxy study confirmed the peculiarity of the deposit and found similarities and differences with other contexts of Younger Dryas age. The Ojo de Agua Black Mat (stratum C2) is far richer in charcoal specks than the related strata, but lacks phytoliths, diatoms or ostracods. No further biological remains were found in it, except for intrusive capillary roots. Clearly water-lain in a shallow pond, the stratum qualifies as a clayey silt with an acidic-to-neutral pH. Rich in heavy metals and with high contents of titanium, the Ojo de Agua Black Mat yielded significant indicators of intense wildfires during the Younger Dryas, but produced no carbon spherules or nanodiamonds supposedly linked to the impact theory.

Se ofrece una sinopsis de las especies del género Navicula sensu lato identificadas en acuatorios dulciacuícolas de Cuba. En 79 localidades se determinaron 43 taxones, de los cuales 25 se registran en un área mas amplia que la anterior y siete son nuevos registros para el país: N. bicephala, N. concentrica, N. goeppertiana var. dapalis, N. lateropunctata, N. pseudoanglica, N. schadei y N. stroemii. El trabajo incluye además las dimensiones celulares, comentarios taxonómicos, la distribución por localidades e ilustraciones originales de cada taxón. Citación: Toledo, L. & Comas,A. 2008. Especies de agua dulce de Navicula (Bacillariophyceae) de Cuba. Revista Jard. Bot. Nac. Univ. Habana 29: 171-184. Publicado: 3 de marzo de 2010. | In the present paper a sinopsis of the genus Navicula sensu lato inhabiting the Cuban freshwaters is offered. Based on samples collected from 79 localities, 43 taxa are identified, from which: N. bicephala, N. concentrica, N. goeppertiana var. dapalis, N. lateropunctata, N. pseudoanglica, N. schadei y N. stroemii are new reports. In the paper are also included cell dimensions, characteristics of Cuban populations and original drawings for each taxon involved. Citation: Toledo, L. & Comas,A. 2008. Especies de agua dulce de Navicula (Bacillariophyceae) de Cuba. Revista Jard. Bot. Nac. Univ. Habana 29: 171-184. Published: 3 March 2010.