The marine conditions of Aralar 120 million years ago, in sight
The great geological changes that occurred on Earth in Baja Aptiense (120 million years ago) had a clear reflection in Aralar, then submerged in the sea. This was deduced by geologist María Isabel Millán in her doctoral thesis presented at the UPV. In addition, it has found an atypical sediment record for the study of this time: in other places of the world, the research layers of the Lower Aptiense are 20 meters thick, while in Aralar they have been found up to 1,000 meters.
In the Low Age Aptiense there was a sharp decrease in the oxygen of the seabed, known as oae1a. This was one of the major global marine changes. Millán has proven that this phenomenon also occurred in Aralar, since he has found stones that indicate this among the sediments. In addition, it has identified a similar oxygen reduction, somewhat later than DBO1, which for the time being has not been found elsewhere in Aralar.
The biocalcification crisis is another indicator of the changes in the Lower Aptiense and Millán has discovered in Aralar the reflection of this phenomenon. In Madoz, southeast of Aralar, there was a reef platform that could be equivalent to the one currently in Australia. At the same time that the OAE1 occurred, the author of the thesis observed a sudden change in the carbonate structure of the platform, reflecting the biocalcification crisis.
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