The described zone is
located in the area called “Chaco-Pampeana Plain”. It consists of a very large
morphologic unit, and covers a great part of South America, from the plains of
Colombia and Venezuela in the North, to the extensive Argentinean Pampas.
Its main characteristic
is the lack of relief. It coincides with a large zone of the crust with a big
stability, of negative tendency where marine and continental sediments have been
accumulated in the geologic past, making wide sediment series, which come from
higher areas in the west continent.
The most modern deposits
have a wind origin made of Pampas loess and chestnut muddy-sandy sediments,
inserted with light sandstones. It is not uncommon to find chalky and gypsum
concretions. The fluvial sediments are only in a few river basins of the zone.
The presence of volcanic ashes as a result of eruptions in the Andes Mountain
Range, make the quality of drinking water not to be optimum because of the
presence of several quantities of arsenic in it.
Junin you can find the North border of what it is called “Basin of Salado”. This
is a negative zone within the Chaco-Pampeana Plain and it extends from the
North-West to the South-East, opening towards the Bay of Samborombon, coinciding
with the basin of the Salado River which has its sources in the Gomez Lake. The
Salado River, the largest in Buenos Aires province rises just 75 meters above
In the south, we can find
the Northern Hills of Buenos Aires or Tandilia System. It is a discontinued
mountain range which faces North-West to South-East and covers 300 km from
Olavarria until Corrientes Cape in the Mar del Plata coast. Its maximum width is
60 km and its height is 524 meters above sea level in “La Juanita”. They are
precambrian rocks made of granite where different sedimentary formations settle
in a discordant way (Metapelites, cuarcita, clays, limestones and Dolomities)
with different development according to the area. Some of them allow commercial
exploitation especially in Olavarria zone.
the north, the plain is interrupted by the presence of the Australes Hills in
the province of Bs.As. or the Ventania System. It is a mountain range which
faces North-West to South-East and it extends 180 km with a maximum width of 60
km. These hills are exclusively made of Precambrian granite. The relief -
rougher than in the system of Tandilia and with heights that reach 1,247 m.a.s.l.
in Tres Picos Hills – stands out in the landscape because of the heights of the
From the geomorphologic point of view, this area is made up of the “Raised
Pampas” - foothill zone which extends
the Pampas Hills to the East, up to the Depressed Pampas - which divides it from
the “Waved Pampas” in the Argentinean river coast as it happens with the “Salada
Basin”. The “Sandbank Pampas” is located in the west and the “intermountain
Pampas” is located in the south.
It is supposed that this higher zone within the Pampas, is influenced by the
greater altitude of the crystal clear basement, broken in sub-southern way
relative to the subsoil of the Depressed Pampas, meanwhile in the south a new
fault has raised the basement generating the Waved Pampas and debility zones
where great rivers flow.
The Raised Pampas
is characterized by the presence of countless basins of wind deflation that
depressions, without communication, bad drainage and currently occupied by
isohyet of 500 mm divides a zone with more humidity, located in the east – which
covers the south of Santa Fe, part of the south of Cordoba and the northwest of
Bs.As.- from a more arid zone to the west – La Pampa, south of Cordoba and San
Luis. These zones are characterized by the presence of lakes in the east and
saltpeter beds, salt marshes and sandbanks in the west.
is lashed by constant floods which cause a great damage to the agriculture and
people who are based in that area. This is a lower zone, flat relief with a
smooth slope to the southeast and a bad drainage.
its undulations have ravines, low lands and fluvial terraces caused by a smooth
slope of the crystal basement and the erosion of the rivers.
ravines of Parana, in the city of Rosario, the flooded areas with elevations
under the Rio de la Plata level (Lujan,
Riachuelo y Reconquista Rivers) and the terraces which decorate the riversides,
in the west of Bs.As. Province is a sandbank flat land without natural gradient
and with waterproof subsoil. These characteristics make the rainwater not to
drain forming an areic basin.
located in the South of Bs.As. is made of Tandilla and Ventania ranges and the
inserted plain. They are not continuous orographic systems; they are a number of
isolated elevations, in the shape of hills or plateau, divided by longitudinal