Northern Central America; The Maya and Chortis blockse
Northern (nuclear) Central America is conveniently divided into the Maya (sometimes called YucatÃ¡n) and Chortis blocks (Fig. 1). The division between the two blocks is the Motagua suture zone, which follows the Motagua River in east and central Guatemala, but whose western extension is buried beneath Tertiary volcanic cover in western Guatemala. The Maya block includes Guatemala north of the Motagua suture zone, Belize, the YucatÃ¡n Peninsula, and Mexico west to the Isthmus of Tehuantepec. The Chortis block consists of southern Guatemala, El Salvador, Honduras, an indeterminate part of northern Nicaragua, and the water-covered Nicaraguan Rise. The boundary between these blocks along the Motagua suture zone of central Guatemala marks the locus of interblock suturing in latest Cretaceous time.
This chapter emphasizes the older geologic history of northern Central America. Certain geologic topics relevant to this area will appear in other chapters of this volume, especially seismicity, neotectonics, magmatism, volcanism, paleomagnetism, mineral deposits, and energy.
Our discussion of the Maya block is limited to Belize and Guatemala north of the Motagua Valley; adjacent Mexican portions will be described in volumes of the Geology of North America covering Mexico and the Gulf of Mexico. Some Mexican rock occurrences which are especially pertinent to the interpretation of Guatemalan units are, however, included here. The Motagua suture zone between the Maya and Chortis blocks is discussed in this subchapter.
The Chortis block subchapter emphasizes the geology of Honduras, where most of the older rocks of this block occur. The Nicaraguan Rise is discussed