Morphology and structure of the spill Arapey formation

The Paraná - Etendeka Province in the northern part of Uruguay is represented by strokes of Arapey Training and intrusive rocks. Fieldwork in this region allowed the identification of three types of stroke: pahoehoe , ' massive a'ae. The type pahoehoe has thicknesses between 10 and 30 m, and eventually lobed shapes with ropes at the top. In spills ' a'a thicknesses ranging from 10 to 20 m and are organized into four distinct levels: one top scummy a vesicular level, a solid core and a escoriaceous basis. The escoriáceos levels are composed of irregular fragments of vesicular basalt associated with quartz and carbonate. In vesicles vesicular level reaches to 7 cm long and are stretched horizontally. The core is a massive basalt and occur in the upper portion geodes filled by chalcedony and amethyst . The lower portion escoriaceous is slightly thicker and when two strokes ' a'a are overlapping merges with the top of the overlying stroke. The massive strokes have thickness of 30 to 50 meters and in general exhibit disjunctions vertical columnar forming irregular blocks . These strokes are similar to the central portion of the province Paraná - Etendeka that have been interpreted as thick pahoehoe . The prevalence of stroke in Uruguay pahoehoe indicates low rate of eruption established in soft paleosurfaces which must have facilitated the movement of lava causing volcanic successions with great lateral extent . Note also that the geodes Artigas occur associated with spills ' a'a bit thick