 Walking along the creek to the area at which a foot bridge crosses the creek the Glenwood Shale Formation , a thin layer of grey @-@ green rock probably deposited in deeper @-@ water offshore from the beaches , can be seen where it has been exposed by erosion . Together , the three formations that are visible as one walks from the upper falls to the river represent a sequence of sea @-@ level rise which occurred during the Ordovician period . 
