Estancias of South America

Estancias of South America

Introduction

Estancia is a Spanish and Brazilian Portuguese term describing a large rural estate with similarities to the English term ranch. The term is used in Argentina, Uruguay and southern Chile. The equivalent in other Latin American countries would be hacienda, or fazenda (only in Brazil). Unlike an hacienda, which could be any type of agricultural venture, producing grain, coffee, vegetable, beef, etc., an estancia, most typically located in the southern South American grasslands, the pampas, has historically always been a livestock (cattle or sheep) estate.

During the first centuries of Spanish colonial rule, cattle introduced by the Spanish roamed free and man undertook raids to catch and slaughter them. In the 19th century stationary ranching ventures started to form in the pampas, with permanent buildings and marked livestock with clearly defined ownership. They were called estancias, the term indicating the stationary, permanent character. The Estancia Valley, a closed topographic and structural basin, contains a lacustrine' sedimentary and paleontologic sequence which reflects changes in the climatic regimen to the Southwest. The geologic section within the valley is uniquely exposed in a series of wind-excavated playas. The stratigraphie and bio-stratigraphic control afforded by the arrangement of the playas is conducive to an interdisciplinary approach to the study of this large area.

Discussion

The geologic history of the Estancia Valley has been synthesized over a period of almost 70 years following Keyes' (1903) observation that the valley contained 1I ••• evidences of the existence of old lakes. O.E. Neinzer (1911), with knowledge of Keyes' observations published a thorough, description of the geology and water resources of the Estancia basin and associated Wells and Encino basins. His pioneer descriptions and analysis of the Quaternary geology is the area stand today as the m03t significant contribution to the understanding of the Estancia Valley history.

A climatic analysis was done by Leopold (1951) in which he attempted to calculate conditions necessary for the maintenance of a large pluvial lake within the Estancia Valley. He concluded that maintenance of such a lake at the 1,891 m (6,200 ft) level would require an increase in precipitation on the order of 18 cm (7 in) a year above that of the present and decrease in mean July temperature of about 90 C(16° F). Working on similar assumptions as Leopold, Antevs (1954) concluded that maintenance of the lake would necessitate an increase in annual precipitation 23 cm (9 in) and a June-September temperature decrease to about 5.50 C (100 F) lower than the present. He also concluded that the same temperature lowering and precipitation increase were responSible for the maintenance of glaciers in many of the mountains.

R.E. Smith (1957) completed a report on the geology and ground-water resources of Torrance County. This report encompasses all but the northern portion of the Estancia Valley. Smith was concerned mainly with water resources for domestic consumption and irrigation projects; however, some of his observations on the Quaternary geology of the valley are significant. He correlated the lower valley fill ...