Geology
The geological formations in the Loire River basin has been dictated by two sets of formations namely, the basement domain and the domain of sedimentary formations; the former domain primarily consists of metamorphic and siliceous fragmented rocks with ground water in fissures, and the latter formation of sedimentary rocks consists of limestone and carbonaceous rocks rich in ground water aquifers. Rock outcrops of granites or basalts are also seen exposed in the river bed in several stretches.
The middle stretches of the river has many limestone caves which were inhabited in the prehistoric era; the caves are several types of limestone formations, namely tuffeau (a porous type of chalk, not to be confused with tufa) and Falun (formed 12 million years ago). The coastal zone shows hard dark stones, granite, schists and thick soil mantle.
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