Letter from Guy Hazen to John Reeside detailing the collection of the specimen that would become USNM 18313.
Description of the measured section “St. Johns South” in Figure 2.
Section measured 18 May, 2008 by Appalachian State University Students (A. Ahlström, A. George, J. Mitchell, J. Norman, W. Sautter) under the direction of A.B. Heckert.
|Unit||Petrified Forest Formation
|13||Conglomerate and sandstone; sandstone matrix is ~grayish orange (10YR7/4), medium-coarse grained, moderately poorly sorted, subangular sublitharenite that is weakly calcareous; conglomerate is extraformational chert and quartzite clasts, subrounded to rounded, up to ~ 10 cm diameter; clast-supported; poorly indurated; forms a brown slope across top of hill.||3.6|
|Unconformity (Tr-4 unconformity of Lucas, 1993)/erosional base|
|Blue Mesa Member|
|12||Mudstone; grayish yellow green (5GY7/2) with some dusky blue green (5BG3/2) and grayish red purple (5RP4/2) mottles.||2.35|
|11||Mudstone, grayish purple (5P4/2) with yellowish gray (5Y8/1) mottles; not calcareous; bentonitic; popcorn weathering; forms uppermost purple stripe.||8.0|
|10||Mudstone, grayish red purple (5RP4/2) with mottles of light greenish gray (5GY8/1); weakly calcareous; includes a horizon of brownish gray (5YR8/1) highly calcareous concretions at top of unit.||2.5|
|9||Sandstone; sandstone is light greenish gray (5GY8/1) with grayish purple (5P4/2) mottles; sandstone is fine-medium grained, rounded, moderately sorted litharenite to lithic wacke; includes pebble-sized (~2 mm) rounded mudstone rip-ups, not calcareous. In outcrop forms a green-purple-green sandwich; upper fossiliferous layer (including past excavations)||2.6|
|8||Mudstone; grayish red purple (5RP4/2) with mottles of yellowish green (5GY87/2); slightly silty; includes yellow green (5GY7/2) concretionary layer at top that weathers brown with mottles of grayish red purple. Forms second prominent purple band locally.||2.2|
|7||Mudstone, grayish purple (5P4/2) to very dusky purple (5P2/2) with mottles of grayish yellow green (5GY7/2); bentonitic; calcareous; popcorn weathering; forms lowest prominent purple band.||5.6|
|6||Slightly silty mudstone; medium gray (N5) with bluish white (5B9/1) mottles; not calcareous; popcorn weathering; grades into unit 7; locally has fossiliferous green sandstones||4.6|
|Bluewater Creek Formation|
|5||Slightly silty mudstone; dark reddish brown (10R3/4), weakly calcareous, forms uppermost red band.||3.6|
|4||Slightly silty mudstone, medium gray (N5) with light greenish gray (5GY8/1), very dusky red purple (5RP2/2) and moderate yellowish brown (10YR5/4) mottles; calcareous; forms greenish band with steep slope.||2.45|
|3||Thin sandstone (3A) overlain by mudstone (3B); mudstone is dusky red (5R3/4) with light greenish gray (5G8/1) mottles; silty; not calcareous; forms reddish layer above sandstone; basal sandstone is very pale green 910G8/2) fresh, weathers to dark reddish brown (10R3/4); fine- to medium-grained, subrounded, moderately well sorted micaceous litharenite; very calcareous; some soft-sediment deformation.||2.45--2.75|
|2||Silty mudstone; pale red (5R6/2) with light greenish gray (5GY8/1) mottles, slightly calcareous; forms reddish slope mantled with sandstone debris||3.6|
|1||Sandstone; yellowish gray (5Y8/1) fresh; weathers to pale red (10R6/2) and grayish red (10R4/2); fine- to very-fine grained, rounded, well sorted micaceous litharenite; ripple laminated; locally floors arroyo||2.5+|