Tullock Member

{{Short description|Geologic formation in Montana}}

{{Infobox rockunit

| name = Tullock Member

| image =

| caption =

| type = Member

| age = Early Paleocene (Puercan)

| period = Danian

| prilithology =

| otherlithology =

| namedfor = Tullock Creek

| namedby = Rogers and Lee (1923)

| region = Montana, Wyoming

| country = United States

| coordinates =

| unitof = Fort Union Formation

| subunits =

| underlies = Lebo Member

| overlies = Hell Creek Formation (MT), Lance Formation (WY)

| thickness = 90–400 m (Powder River Basin)

| extent =

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}}

File:Coal_Stratigraphy_Powder_River_Basin.png

The Tullock Member is a geologic member in Montana and Wyoming, forming the lowermost part of the Fort Union Formation. It is also known less commonly as the Tullock Formation, forming part of the Fort Union Group.{{Cite web |title=Geologic Unit: Tullock |url=https://ngmdb.usgs.gov/Geolex/Units/Tullock_10976.html |access-date=2025-06-01 |website=National Geologic Map Database |publisher=United States Geological Survey}}. It preserves fossils dating back to the Paleogene period.