Lithological correlation of Texcoco lake subsoil

Abstract

Background. Originally, there was a single lake in the Mexico Basin known as Texcoco Lake, which was separated by an levee constructed by the Aztecs to prevent salt water from the north from mixing with fresh water of Tenochtitlan. Goals. The objective of this work was to determine if the absence of the brine productive layer in the southern zone of Lake Texcoco is caused by faults or changes in facies. A study of lithological correlation was carried out using cores with continuous recovery of sediments. Methods. Five cores were made with a rotary machine in order to define the lithology in an N-S cross section along the Lake of Texcoco, by means of a detailed lithological description. Results. We determined that the brine productive hard layer was not affected by faults, but rather changed in the meridional lake zone due to muddy facies. The presence of volcanic ash, sometimes pumitic, was useful for the lithological correlation. Sediments are corrosive due to their salinity concentrations. Reducing greenish muds and oxidant red muds were found with frequent ostracods intercalations. There is a non-homogeneous medium with depths from 37 m to 60 m. The muds may amplify seismic waves. Conclusions. Lacustrine sediments in the subsoil of Texcoco Lake are a heterogeneous media and the subsoil is highly corrosive due to its salinity levels. The first hard layer was successfully defined and a second hard layer was found under the first hard layer. There are diverse lithological facies with interbedded volcanic ashes.