La periode glaciaire dans l'ouest des Pyrenees centrales franco-espagnoles

Abstract

Abstract Small glaciers of the true alpine type formed on the lower slopes of the northern Pyrenees. The morainic arcs left by these tongues are in contact with the diffluences of the principal glacier, indicating that these small glaciers descended before the main glacier reached the valley. The major valleys of the northern slope were occupied by tongues with multiple diffluences of the present Himalayan type. The larger glaciers, similar to the Alaskan type, extended in lobes onto the piedmont. The external moraines of these glaciers are Rissian as indicated by their relationship with the principal fluvioglacial terrace. The erratics on the slopes above and in front of the frontal moraine are related to an expansion phase of the Rissian glacier rather than to a separate advance because their morphoscopic and petrographic characteristics do not differ from the frontal morainic deposits. The internal moraines, by comparison with the Alps, can be attributed to the Wuerm. The volume of these deposits is less than the Rissian glaciers due to reduced morphologic activity in the Wuerm--especially on the southern slopes--and to the general retreat of glaciers prior to a long interglacial period.