Abstract

Upper Paleozoic marine rocks were recognized in Central America late in the nineteenth century, and their character and distribution were made known in a reconnaissance study by Karl Sapper (1896-1937). They occur in a narrow folded and faulted belt, 20 to 25 mi. wide, extending eastward from Chiapas, Mexico, through Guatemala to British Honduras. In most places, the sequence can be divided into a lower shale division, several thousands of feet thick, called the Santa Rosa formation by most investigators, and an Upper division of 1,000 to 2,000 ft. of limestone and dolomite to which various names have been applied: Grupera, La Vainilla, and Paseo Hondo in Mexico, and Karbonkalk and Chochal in Guatemala. The Upper Paleozoic rocks are thought to overlie, unconformably, older metamorphic rocks, and are overlain, unconformably, by red beds of the Mesozoic Todos Santos formation. Fossil collections obtained from these rocks by various investigators indicate ages ranging from Carboniferous to Permian. The lower part of the Santa Rosa formation usually has been assigned to the upper Pennsylvanian throughout the outcrop belt. Lower and middle Permian fusulinids have been reported from the limestone sequence in Chiapas and Guatemala. In British Honduras, Pennsylvanian brachiopods have been reported from the lower part of the sequence and a middle Permian ammonoid from near the top. The present investigation of the upper Paleozoic sequence in Guatemala has provided new and more comprehensive fusulinid collections. Among them, species of the genera Eoverbeekina, Schubertella, Schwagerina, and Parifusulina are recognized. One species of each of the four genera was recognized previously in Chiapas, Mexico, and 1 species of Parafusulina in Guatemala. Three new species of Parafusulina are described: P. erratosoptata, P. biturbinata, and P. subrectangularis. One identifiable species from the uppermost part of the Santa Rosa formation in Guatemala indicates a Permian age for a few hundred feet of shale near the top of the formation. Similarity of a number of species to forms from the Permian of Texas strongly indicates ages of Wolfcampian, Leonardian, and early Guadalupian for the massive limestone sequence. The Pennsylvanian-Permian boundary, as yet unidentified, evidently lies within the shale section. The upper Paleozoic sequence appears to change facies from W. to E. In Mexico and Guatemala, it consists mainly of shale and limestone with sandstone conspicuously absent, while in British Honduras, sandstones and shales are dominant with only a few thin beds of limestone. A terrigenous source to the E. is suggested.

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