Editing Geology of the Alps (section)

===Eo-Alpine phase in the Cretaceous===
The [[Divergent boundary|divergent]] movement of the European and African plates was relatively short-lived. When the Atlantic Ocean formed between Africa and South America (about 100&nbsp;[[annum|Ma]]) Africa began moving northeast.

As a result of this process, the soft layers of [[ocean sediment]] in the Alpine Tethys Oceans were compressed and folded as they were slowly thrust upwards. Caught in the middle of the merging continents, the area of the Tethys Sea between Africa and Eurasia began to shrink as oceanic crust subducted beneath the Adriatic plate. The tremendous forces at work in the lower continental foundation caused the European base to bend downward into the hot mantle and soften. The southern (African) landmass then continued its northward movement over some 1,000&nbsp;km (600&nbsp;mi). The slow folding and pleating of the sediments as they rose up from the depths is believed to have initially formed a series of long east–west volcanic [[island arc]]s. [[Volcanic rock]]s produced in these island arcs are found among the ophiolites of the Penninic nappes.

In the [[late Cretaceous]] the first [[continental collision]] took place as the northern part of the Adriatic subplate collided with Europe. This is called the [[Eo-Alpine orogeny|Eo-Alpine phase]], and is sometimes regarded as the first phase of the formation of the Alps. The part of the Adriatic plate that was deformed in this phase is the material that would later form the Austroalpine nappes and the Southern Alps. In some fragments of the Piemont-Liguria Ocean now in the Penninic nappes an Eo-Alpine deformation phase can also be recognized.

Apart from the Eo-Alpine fold and thrust belt other regions were still in the marine domain during the Cretaceous. On the southern margins of the European continent shallow seas formed limestone deposits, that would later be (in the Alps) incorporated into the Helvetic nappes. At the same time sedimentation of [[Anoxic sea water|anoxic]] [[clay]] took place in the deep-marine realms of the Piemont-Liguria and Valais Oceans. This clay would later become the [[Bündner slate]]s from the Penninic nappes.