Juana Lopez Member

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Juana Lopez Member
Stratigraphic range: Turonian
Unit ofCarlile Formation
UnderliesNiobrara Formation
OverliesCodel Sandstone member of the Carlile
Thickness0–6 feet (0.0–1.8 m)
PrimarySandstone with abundant carbonate fossil grains
OtherGravel, Codel fragments
Country United States
Type section
Named forMesita Juana Lopez Grant, six miles northwest of Los Cerrillos, New Mexico
Named byRankin
Year defined1944

Juana Lopez refers to both the uppermost member of the Carlile Shale formation and to the environment that cause it to form. This unit is calcareous sandstone of Turonian age, Upper/Late Cretaceous series in the southern and western Colorado and northern and central New Mexico.[1]

Where present, the Juana Lopez is "the most enigmatic" member of the Carlile Shale. It consists of sand with a large content of indistinguishable grains of fragmented coral, shells (especially inoceramid prisms), sharks teeth, bone, etc. It smells of sulfur when freshly broken. It formed on wide, shallow marine shelf, with strong wave action, but with little sediment coming in from land. It was exposed on the land surface between the retreat of the Greenhorn cycle and the advance of the Niobrara cycle of the Western Interior Seaway.[1]


  1. ^ a b Russell K. Lewis, Stratigraphy and depositional environments of the Late Cretaceous (Late Turonian) Codell sandstone and Juana Lopez members of the Carlile shale, southeast Colorado, 2013 - Mines Theses & Dissertations, retrieved 2018-08-14