SALDAñA FORMATION IN TOLIMA, COLOMBIA: TECTONICS AND STRATIGRAPHY OF MESOZOIC ROCKS

The South America continental´s margin post Triassic- Jurassic periods at the Magdalena River Valley in Tolima region, located at the central area of Colombia are represented by different formations. Saldaña Formation is one of them. The research on the Chicala Member, composed by a sequence of layers of basic volcanic ash intercalated with sedimentary rocks characterized by medium to wide strata, semi compact, very fine grained, violet to purple color, deposited along transitional basin and also, presence of andesitic intrusions up to the middle part of the Saldaña Formation.

Over this sequence is easy to find an unconformity of limestone of Cretaceous with very low dip as the last event during Mesozoic representing a marine transgression with outcrops present along Prado-Dolores drive road. Finally, basic intrusive rocks are cutting the sequence of volcano-sedimentary layers as Upper part of the JurassicAll main Triassic- Jurassic outcrops of Saldaña Formation in Colombia are along both sides of the Upper Magdalena Valley River, which are faulted forming a synrift basin; the inclination of planes are forming a graven. After Jurassic period, several tectonic processes had occurred and this formation was folded. Later, long erosive process shows evidences before Cretaceous limestone. Comparable limestone are present over both Jordan Formation (Santander) and La Quinta Formation (Cesar and La Guajira), which were analyzed previously; It is clear the presence of similar plain limestone also in Venezuela. However, this Mesozoic level of limestone is not present at the Northeastern of the United States.

Apparently, Saldaña, Giron, Jordan, and La Quinta Formations were deposited in a similar transitional environment. In addition, using XR-Fluorescence analysis, they have showed some similarities in values such as Zr, Sr, Ba, Cr and more compared to some samples from New Jersey, US. It is necessary to examine more samples in field and laboratory.