Scales Shale

{{Short description|Geologic formation in Illinois and Indiana, United States}}

{{more citations needed|date=October 2017}}

{{Infobox rockunit

| name = Scales Shale

| image =

| caption =

| type = Formation

| age = Ordovician

| period = Ordovician

| prilithology =

| otherlithology =

| namedfor =

| namedby =

| region = Illinois, Indiana

| country = United States

| coordinates =

| unitof = Maquoketa Group

| subunits =

| underlies = Fort Atkinson Limestone

| overlies = Trenton Limestone

| thickness =

| extent =

| area =

| map =

| map_caption =

}}

The Scales Shale is a geologic formation in Illinois. It preserves fossils dating back to the Ordovician period.