Mesozoic Stratigraphy of Central Honduras

Abstract

Geologic mapping near Lake Yojoa in central Honduras has shown the need to modify the published Mesozoic stratigraphic column. The Ilama Formation is not a useful unit for regional mapping inasmuch as Ilama-type strata are discontinuous and in various stratigraphic positions. The formal name Ilama Formation should be abandoned. A new formal name, the Jaitique Formation, is introduced to designate a major Cenomanian limestone unit that is stratigraphically about midway in the Valle de Angeles Group in the Santa Barbara-Lake Yojoa region. The Jaitique Formation consists of up to 140 m of shallow-marine strata that can be divided into two members: (1) a lower member of thick-bedded shelf carbonate strata, and (2) a distinctive upper member of thin-bedded, laminated, nonfossiliferous limestone which may represent a shallow, possibly hypersaline, lagoon or intertidal mud-flat environment. Because the lower member of this Cenomanian limestone was formerly misidentified as the Atima Formation of the Yojoa Group, the upper, thin-bedded member was originally defined as the Guare Formation of the Yojoa Group. The name Guare is retained, but the unit is downgraded to the Guare Member of the newly defined Jaitique Formation within the Valle de Angeles Group. Although the Jaitique Formation is similar in stratigraphic position and age to the Esquias Formation in the Minas de Oro area on the east, it is lithologically distinct, and probably slightly older. The two units are not thought to be lithostratigraphically contiguous. Recognition of major Cenomanian limestone units within the Valle de Angeles Group has led to reappraisal of the hydrocarbon potential of certain structural zones in Honduras.