GEOCACHING POINT
(nearby)
GC8RN61-#4 PR3-MAC - SOS4 - MEIOS TERRESTRES
Along the trail to the Ribeira do Ameal and in some of its derivations it is possible to observe sets of solid or slightly graded metasilto-pelite benches.
These benches are characterised by their constant and persistent spheroidal shape, giving rise to rounded structures with dimensions that can sometimes reach a few metres in length.
These benches often present a special "onion or scale" type alteration.
Associated with these structures are films or iron crusts, suggesting the presence of abundant iron inside these layers.
These sediments have been interpreted as being deposited in glacial environments. They have resulted from sedimentary processes that would have occurred in sub-glacial watercourses in the transition between the marine and continental environment during the Paleozoic.
In these locations, environmental oxidation conditions would have prevailed, possibly relatively superficial waters, near the Gondwana continent, located at the South Pole, which would have allowed greater precipitation of iron and manganese metals.
Under these circumstances, it is to be expected that at the time of the formation of these units, in times of the Upper Ordovicic, this entire region would be located in the southern hemisphere of the Earth, close to its pole.