Talk with Luismi Agirrezabala at the Basque Summer University

1990/11/01 Tapia, Xipitri Iturria: Elhuyar aldizkaria

• Geologia
• Unibertsitateak

In the events organized by the UEU in July in Pamplona, he met geologist Luismi Agirrezabala, who informed us of the events carried out the previous day. Although the conversation was short, what Agirrezabala told us seemed very interesting and we started the booth. This is what he told us:

In the morning we have been in Olatz. The valley in which it is located is interesting from the biological and geological point of view. The direct relationship between vegetation and land has been analyzed. In the surrounding mountains are mainly holm oaks. This type of tree requires basic soil, and if we analyze the soil it will look basic. At the bottom of the valley there is a oak grove. For the cultivation of the oak, acid soil is required, and if the soil is analyzed, it is observed to be acidic.

On the other hand, the valley is very closed. This characteristic indicates that karstification has occurred, that is, this valley has been originated by aqueous dissolution. In the beginning, the dissolution only gave rise to a few small holes that, as karstification increases, became increasingly larger. In this way, a closed valley was created in which the water transported fillings were deposited at the bottom of the valley. For this reason, the ground has a high degree of acidity, while the slopes are basic.

In the afternoon session we analyzed the old turbiditic fan of Ondarroa. First, we explained what the turbiditic fan is. The turbiditic fan is a set of formed submarine deposits. These sets of deposits are usually mainly at the foot of jumps or slopes. At the top of the slope are usually channels cut by water and as the channels go down are more separated and their depth decreases until disappearing. The turbiditic fan of Ondarroa has some characteristics. We analyze a fan channel and its filling. It was totally conglomeric and the limestone rocks of the conglomerate were very hard. This fan is Saturraran, along with Ondarroa. Next, we analyzed the conglomerate of the Larruskain area, observing the tendency of grain crumbling. The grains of the filling were much thinner and the layers thinner.