November 9, 2013: Day 4, Through Black Forest Bed

Core of lower_bfb_composite
(1) Cores of lowest Black Forest Bed. Base is at the small segments in the middle.

The The late PM saw coring though the Black Forest Bed of the upper Petrified Forest Member (1,2). This unit is a very laterally continuous, volacnoclastic sandstone and carbonate pellet bed with characteristic black silicified logs (3: Morgan Schaller for scale), which give the unit its name. This very important marker bed (2) produced the first zircon U-Pb date from the Chinle Formation (Gehrels and Dickinson, 1995; Riggs et al., 1996), a date that his been much refined by recent work to 209.926 0.072 Ma by Ramezani et al. (2011). The latter samples were recovered from Chinde Point, right below our drilling site.

At near by Nizhoni Point, the upper Petrified Forest Member and overlying Neogene Bidahochi Formation can be seen. The upper dark gray unit is Bidahoch basalt underlain by the olive to pink lake strata of the  same formation. This is underlain by basal  purple and red Owl Rock Member and uppermost red Petrifiued Forest Member red beds (4, 5). The white bed and underlying thin brown bed are the tuffaceous sandstones and carbonate-pellet bed, resepctively of the Black Forest Bed. This is underlain by more Petrified Forest Member.

Upper pfm_nizhoni_point
(2)  View of Black Forest Bed and adjacent section from the Nizhoni Point look out
Silicified tree in Black Forest Bed (Morgan Shaller for scale)
(3) Silicified tree in Black Forest Bed (BFB)
Core recovery upper pfm
(4) Painted Desert Member above BFB
Reduction spot in Painted Desert Member
(5) Reduction spot in Painted Desert Member
Next (11-10-13)