CHEMICAL PHENOMENA AS UNFAMILIAR IN GIRóN FORMATION IN SANTANDER, COLOMBIA: FAR FROM RHETORIC, CLOSER TO REALITY

Three short strata of rock along the road near to Zapatoca, Santander, Colombia show chert’s typical conchoidal fracture. This sample have a high clay content and in the outcrop look at first glance like shale, but it is greater hardness gives it away.

It is a sedimentary rock that consisting almost entirely of silica SiO₂, a fine grained microcrystalline rock that may contain small fossils. It varies in color from gray, grayish brown to light green. This color looks like an expression of trace elements present in the rock. In this case, green color is most often related to traces of reduced iron.

Also, this sample is tough and a compact rock with low porosity. It is composed mainly of microcrystalline quartz. The texture is non-clastic, grain size is microcrystalline, hardness correspond to a hard rock, do not show clasts. Other features like smooth to touch, conchoidal fracture and glassy

It is not common among the sediments of the Girón Formation along Bucaramanga-Zapatoca, Santander road, where evidence of fluctuating transitional environment appears in a big outcrop. Neither, this kind of chemical sediments are usual in Saldagna, La Quinta, Guatapuri, and Jordan Formations in Triassic-Jurassic.

This chemical activity in a paleo-channel occurred when imperceptible water levels rise and fall almost during a part of the Triassic-Jurassic. This activity is represented by millimeter bands of very thin material layers a few centimeters thick, whitish to greenish highlighting the distance contracting with the generic violet red of this important geological formation in Colombia, which is being investigated in the stratigraphic correlation with the Newark Supergroup (Martínez -Sacristán, H. 2012-2015 in GSA.)