Field Notebook: Texas 1957b
Page 29
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Transcription
Collection 8/16/57/11 - From 10' interval of limy beds below iron red Uddenites sandstone horizon in 2nd Terrva block east of geologists' canyon. The lower part of the cyclic beds are exposed to the east of geologists' canyon above the #2 limestone member. There seems to be considerable structure (at least for this area) as the #2 beds take a sudden dip beneath the cyclic beds. The shale interval here is a light gray and is slightly silty. 4 to 5 of these cyclic calcareous sands are present. The bulk of the material is a coarse rubble and includes dark gray limestone pebbles 2-3" diameter and has mottled weathery appearance over all. I don't see how all of the structures here can be attributed to draping over buried reefs although that is still within possibility. The explanation of a SW-NE structure trend is appealing. These beds seem to be faulted in the limestone units and flowage in the shales but no definite such structures were observed. PG. 39 8/17/57 (Section 36, Memior 88) Section 29: Moore Ranch; 200 yards east of last Wolfcamp limestone exposure. 1) Covered, probably siltstones and shales, base of unit under alluvium. 2) Sandstone, light green-gray to brownish-gray to brownish-orange, very fine grain quartz for most part; occasional conglomeratic beds. 4'. 3) Limestone, green-gray, fragmental hash, these are in a limy shale matrix and are similar to the #3 bed, section 23. 27'. 4) Covered, 11'. (same as 3 in stream cut but considerable more clay %) 8/17/57/4. 5) Sandstone, weathers orange-brown; fresh is green-gray: very fine to fine grain quartz; 1/5'. 6) Covered, 15'. 7) Calcarudite; light gray to light brown-gray weathering up to 6" cobbles, very small amounts of chert. (8/17/57/1 - pebbles). 15' to top of ridge, this unit forms dip slope here. PG. 40 50 yards west of section 29; in a stream cut a 9' limestone underlies the calcarudite. Thus it seems the calcarudite has been deposited in a eroded surface of the limestone. 6)A. Limestone, light pink; massive weathered surface has a tinge of brownish- orange. 0' to 9'. 8/17/57/3. 6)B. Limestone, light gray, some yellows; calcarenite 6" to 8" beds, Collection 8/17/57/2; 0' to 20'. These 2 units overlie 6) and underlie 7). {note: illustration followed} I think the Calcarudite is wave reworked material, not much transport, the cherts yes, but most of the limestone have probably been reworked nearly in place. Beds 6A and 6B weather into horizontal wavy "bedding" lines; these I have called debris beds off reef highs and I suppose that would hold here too.