Geology of the Southeastern Region of Mexico
For the description of the region of southeastern Mexico, the following limits have been selected: on the west, the Isthmus of Tehuantepec; to the north, the shores of the Gulf of Mexico; and to the south, the Pacific coast. The region includes the physiographic provinces of the Chiapas Mountains, the Central American Cordillera, the Yucatán Peninsula and the eastern extreme of the coastal plain of the southern Gulf (see Figure 1.1).
The climate of this region varies from temperate and semi-arid in the high parts of the Sierra de Soconusco and Sierra de Chiapas to hot in the coastal plain of the Gulf and Pacific as well as in the central depression of Chiapas. In this last area the climates are subhumid and different from the coastal plains where they are generally humid. In the Yucatán Peninsula the climate is typically hot and subhumid. In all places in southeastern Mexico the rainy season is in the summer except in some areas of the Gulf Coastal Plain where rains occur all year.
In the region that includes the states of Chiapas and Tabasco, a great sequence of Mesozoic and Cenozoic rocks crops out. It consists principally of marine sedimentary rocks that are folded and faulted.
This sequence rests discordantly on a crystalline basement of Precambrian and Paleozoic rocks that crops out to the southwest of the region, where the crystalline rocks of these Eras form an outlying metamor-phic and plutonic complex constituting the nucleus of the Sierra de Soconusco.
Figures & Tables
Available knowledge concerning the origin and geologic structure of mexico is still incomplete. Each day scientific discoveries, advances in mapping, and new techniques of exploration offer more information toward the development of tour understanding. Nevertheless, it is still difficult to achieve a complete description of the geologic character of the territory of the nation, as well as to work out functional models to explain the origin of its geologic structure. Along with the development of geologic studies that science has made in mexico, there have been a few attempts to formulate general works covering the many aspects of geology that the country presents. Nevertheless, one must recognize that the lack of information about certain periods in the geological history of the national territory, and the numerous unexplored areas, have constituted some principal obstacles toward achieving a finished work of this type.
Inreviewing past information, it is worth indicating that in 1896 a somewhat unsettled entitled A Sketch of the Geology of Mexico formulated by Jose Guadalupe Aguilera and Ezequiel Ordonez of the Geologic Institute of Mexico, a descriptive work that constituted an important complement to and summary for the Geologic Map of Mexico, which had benn published earlier. Nevertheless, it was not until 1949 that V. Garfias and T.C. Chapin published the work entitled Geology of Mexico, in during the geological history of the republic are included.
A more recent work is The Geology of Mexico, whose author was Ing. Manuel Alvarez, Jr., and which the Faculty of Engineering of UNAM printed as notes