(1) Sonsela Member at Blue Mesa.
The Sonsela Member of the Chinle Formation is one of the most interesting units in the formation.
In addition to having most of the petrified logs in the Park (1) it is also the unit that contains the largest magnitude faunal and floral change in the Chinle. Note log weathering out of slope.
During the evening the night ship (2. 4) saw coring into the Jim Camp Wash Beds of the Sonsela. This interval (2) appears to be the right age to correlative with the giant Manicoagan impact structure (3) based on U-Pb dates. This same interval records the largest faunal and floral change in Chinle Formation.
(2) Prominant red silcrete within transition between the Adamanian and Revueltian in the south park.
(3) Manicoagan impact structure
(Wikipedia Link)
(4) Night drilling