The Flysch of Zumaia and Deba, located on the Basque Coast Geopark, is a remarkable geological formation that offers a unique window into Earth’s history. This impressive sequence of sedimentary rock layers, exposed along the coastline between Zumaia and Deba, provides a continuous record of approximately 60 million years of geological time, spanning the late Cretaceous period and the early Paleogene period.
The term “flysch” refers to a specific type of sedimentary sequence characterized by alternating layers of hard and soft rock, typically sandstone and shale or marl. These layers were deposited in deep marine environments, often at the base of continental slopes, by turbidity currents – underwater flows of sediment-laden water. The distinct layering is a result of these periodic turbidity flows depositing coarser sediments (sandstone) followed by finer sediments (shale or marl) as the current slowed.
The Zumaia Flysch is particularly significant for several reasons:
- Continuous Stratigraphic Record: It represents one of the most complete and continuous stratigraphic records of this period globally, providing valuable data for studying geological events, climate change, and the evolution of life.
- K-Pg Boundary: The flysch contains the famous K-Pg boundary (formerly known as the K-T boundary), a thin layer of clay that marks the boundary between the Cretaceous and Paleogene periods, approximately 66 million years ago. This layer is associated with the mass extinction event that led to the demise of the non-avian dinosaurs. The presence of iridium, an element rare on Earth but abundant in asteroids, within this layer provides strong evidence for an asteroid impact as the primary cause of this extinction.
- Visual Representation of Geological Time: The distinct layers of the flysch provide a tangible and visually striking representation of geological time, allowing visitors to see millions of years of Earth’s history laid out before them.
The Zumaia Flysch is not only a site of great scientific importance but also a visually stunning natural landscape. The dramatic cliffs, exposed rock formations, and the interplay of the sea create a unique and memorable experience. Its accessibility, with clearly marked trails and viewing points, allows visitors to observe and appreciate this remarkable geological treasure.
More information: https://geoparkea.eus/en/
