• Member description taken from 2007 Long. Tempestite frequency curves: a key to Late Ordovician and Early Silurian subsidence, sea-level change, and orbital forcing in the Anticosti foreland basin, Quebec, Canada. Can. J. Earth Sci. Vol. 44, 413-431. "The Lavache member is the lowest exposed unit on Anticosti Island. It consists of at least 110 m of interbedded, thin-bedded, flat to wavy laminated micrite and fine to very fine calcarenite, repetitive sets of laminated and thin-bedded nodular argillaceous micrite, and minor laminated calcareous mudstone. Coarse to very coarse grainstones are common. Whereas many of the finer beds appear to be laterally continuous, the calcarenites tend to be discontinuous. Many of the fine to very fine calcarenites are burrowed and have sculptured upper surfaces in the form of pits, trails, and burrows extending down from overlying nodular micrite beds. The base of some of these beds is characterized by thin layers of bioclastic sand, commonly containing well-preserved, disarticulated brachiopods. Hummocky cross-stratification is present locally, with hummocks on the scale of 5 to 10 cm, and separations of 5 to 8 m. These hummocks are best seen in the modern tidal flats as the surface becomes flooded. The upper surfaces of some of these typically sharp-based units contain wrinkle marks (Fig. 3B), probably formed by waveshock-induced fabric collapse (Long 1993c, 1997)."