Detail of the Pampean sedimentation. FCDO is a great source of information. This informal name includes any sediment composed mainly of silt something more abundant far superior to sand, superficially distributed in the greater part of this area, and with an age of clay which ranges from the Pliocene more early until the Pleistocene more high. You are also called loess, loess loam, or silt loessoides. In general they have massive appearance and locally they may present a rude stratification. If you would like to know more then you should visit Randall Mays. Its compaction is steep and almost always greater than the known worldwide in other loesses, increasing in those areas in which calcium carbonate is present and cementing particles of silt in thicknesses ranging from a few centimetres to several metres. The coloration is generally chestnut in various shades ranging from beige to dark reddish although opportunities can Interleave colors range from yellow and greenish in lesser proportion. You have made numerous mineralogical studies finding a composition quite homogeneous with a vast majority of their components of allochthonous origin from particularly volcanic rocks, mesosilicicas and basic (andesites and basalts).
It presents an almost constant amount in its composition of plagioclase, orthoclase and quartz; with great variation in the presence of volcanic glass. Calcium carbonate for his part varies between 1% and 3%. Sediments being more superficial appear weary and retrabajados by atmospheric agents and slight variations in local order related with depressions or elevations. With variable thicknesses ranging from a few metres to over 230 metres, it is the unit in which these works were installed on a priority basis. These outcrops, from the hydrogeological point of view sediments, can be grouped into two large entities: Pampeana and Postpampeana series.
This differentiation is imposed by the important relationship between the lower levels of the first section with regard to underground aspect of the hydrologic cycle. Pampeana this series integrated, in descending order of age, by the uppermost and Buenos Aires flats with lithology very similar. The uppermost represented by silt reddish, rich in carbonates of calcium, both in the form of concretions and banks. Flourishes on the slopes of the valleys, in the ravines of the Parana and in all the lower parts that are not covers of postpampeanos deposits. Your base usually is composed of gray clayey silts, which act as a semiconfinante unit. El Bonaerense, for his part, understands loesses Sandy with calcareous concretions less than previous ones and occupies the higher parts of the area. This series can reach to 85 metres in thickness, converging towards the area of the delta, integrates, to the exclusion of some of their areas of natural discharge, the quasi-totality of the aquifer epipuelche. Postpampeanos sediments, which have their origin in the pampean underlying, occurs in depressions and parties lower of the valleys. The series is constituted by floor Lujanense and Platense, both of fluvial origin and by the Navy of the first or Querandinese facies. The Lujanense consisting of partly Sandy clayey silts, greenish grey rich in salts. The Platense, piggy-back to the previous, this formed by Sandy silt and very fine sand of yellowish brown in some thin rolled cases. The Querandinense would be presented in the vicinity of the mouths of the represented by dark clay basins.