Ripple cross-stratification in swaley cross-stratified sandstones of the Chungo Member, Mount Yamnuska, Alberta

Abstract

Swaley cross-stratified sandstones are exposed in the Late Cretaceous Chungo Member of the Wapiabi Formation at Mount Yamnuska, Alberta. At this site, many of the individual flaggy-weathering, thin beds of sandstones that make up the swaley cross-stratified structure are internally ripple cross-stratified. The association of swaley and ripple cross-stratification has not previously been described and is interpreted to indicate compound cross-stratification generated under combined flow condi tions. Furthermore, this association brings into question the possible genetic relationship between swaley cross-stratification and hummocky cross stratification, a sedimentary structure generated under purely oscillatory conditions.