Geological History

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Quaternary

This is a period of Geological Time divided into two ages: Pleistocene and Holocene.

The Pleistocene, going back 2.5 million years till some 11,700 years, is characterized by the inclusion of a series of glacier cycles and interglacial periods.  A glaciation consists of a phase of cold weather, in which large extensions of the planet are covered by glaciers and snow which causes the descent of sea level due to the freezing of great quantities of water. On the contrary, during the interglacial periods the climate becomes warmer and sea level rises.

The Talamanca mountain range, on the other hand, reached its current emplacement and configuration, and continued its process of intense erosion.  The most important glacier cycles left conspicuous traces on the highest peaks of Chirripó and Kámuk mountains.

The development of the alluvial fans of the Talamanca foothills would reach their peak, especially during the interglacial cycles.

In the Holocene, that is from some 11,700 years ago to the present, the processes of erosion and sedimentation continued, as well as their accumulation, both on the foothills and the coast. The Térraba River was forced to change its course several times.  At the same time, the Diquis delta reached its present configuration, when a balance was established between the ongoing contribution of sediments coming from the continent and the eroding processes in the coast caused by the tides’ action, the swell and marine currents.

The Diquis delta has a thickness of around 80 to 150 meters of sediments, deposited during its dynamic development.  Its foundation is deemed to be formed by rocks from the Térraba Formation. According to the current sedimentation rates and taking into account its density, it may be deduced that the delta’s age is at least of 7,000 years before the Present.

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» Eocene

» Oligocene

» Miocene

» Pliocene