Red marble from Ereño and Baztán
2005/07/01 Andonegi Beristain, Garazi - Elhuyar Zientziaren Komunikazioa Iturria: Elhuyar aldizkaria
These marbles are characterized by their color, red, but
also by their hardness and durability.
Cretaceous and Rudists
The marbles of Baztán and Ere emerged in the Cretaceous, that is, from 120 million years to 65 million years. In these fossilized rocks are the bivalves that inhabit the sea: the rudists. The white shapes or circles seen in the red marble of Oko and Baztán are precisely the fossils of the Rudists.
The rudists were bivalves in the form of a cucurucho or cup that lived among corals and, from the geocronological point of view, disappeared in harmony with the dinosaurs. That is why they are so interesting because they can make known the events and climatic characteristics of the time.
Discovering the history of Marble
Bombing the fossils of these rudists with electrons, the researchers make appear the proportion of elements of marble. They define the mineralogical and geochemical composition of marble. Thus, geological processes can know which elements were added to fossils. In fact, calcium, strontium and sodium can be considered rudist components, but the rest, such as manganese and iron, are usually added externally.
In addition to these studies, Leioa geologists use catodoluminescence. By means of catodoluminescence, elements that in their origin were not of the shell are revealed, since the shells of the bivalves do not emit luminescence by themselves. Thus, in the marbles cut into thin sheets, in view of the location of luminescence, it is observed where strange elements were scattered in the stone.
In addition, quantifying the number of layers of the fossilized rudist shell, measuring the distances between layers and conducting studies with stable isotopes, obtain other data: the amount of life of the rudists, the variation of the temperature of the sea, the influence of brackish or sweet waters, their sinking in the subsoil, their extension, etc.
But there is something they have not yet clarified. Where does the red color of the marbles of Baztan and Ere oko come from? This is what researchers would like to study from now on and see if the spill came from an iron layer below and when it happened.
These research aims to create the identity card of the red marbles of Equally Oko and Baztán, since the stone market also abounds counterfeits. For this it is necessary to know all the secrets that enclose these marbles.
