AN EXAMPLE OF A KINKING MICROFABRIC IN UPPER PLEISTOCENE GLACIOLACUSTRINE DEPOSITS FROM LLAVORSI (CENTRAL SOUTHERN PYRENEES, SPAIN)

Glacially deformed glaciolacustrine rhythmites exposed at Llavorsi in the Central Southern Pyrenees show a well-developed macroscopic crenul ation lineation. Microscopic studies (thin sections and SEM) reveal a crenulation cleavage associated with very small-scale symmetrical fold ing and a banded extinction pattern. Combination of the thin section a nd SEM observations allows the reconstruction of a herringbone-like ar rangement of finegrained particles or kinking microfabric. The occurre nce of this microfabric can be used as a criterion for shearing, also in the absence of macroscopic observations.