This field trip will give the participants an overview of the Quaternary deposits and late Cenozoic faulting which have shaped the Helena valley The Helena valley is a NWtrending graben surrounded by bedrock highlands Most of the western half of the valley is a young alluvial plain formed of coalescing alluvial outwash fans issuing from drainages flowing towards Lake Helena The western valley is ringed by older pediment surfaces sloping gently down from the valley margins The eastern half of the valley is underlain primarily by later Tertiary silts sands and gravels uplifted and segmented by normal faulting Atop these Tertiary deposits along the southern valley margin early Quaternary alluvial deposits are preserved as hilltop remnants of a formerly much larger deposit Late Cenozoic faulting shaped the Helena valley creating the modern topography and influencing sedimentation patterns; however only a few faults show evidence of late Quaternary offsets