Field Notebook: Texas 1957b
Page 51
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Transcription
The low hills south of Leonard Mt. are folded and faulted rocks of the lithology of the "Dugout Mt." series. They are orange-brown sandstone, dark silicified limestone (clastic limestone) and "marls" (very fossiliferous silty clayey zones). Collection 8/24/57/2 is from one of the fossiliferous "marls". (2 bags). The fusulines look like Upper Wolfcamp or Hess ones. This could be terrva block or a fault block. See aerial photos SW corner of Hess property. [Fusulina sp; Desmoines Age]. I frankly don't know what formation the silicified dark limestone represents; it is like those beds Conoly Brooks showed me at the SW corner of his W pasture. I believe the rocks are badly faulted and folded and are part of the large thrust sheet picture. PG. 71 The lower conglomeratic contains rocks of the lithologies which are underlying the areas south of Leonard Mt. The upper conglomeratic is a calcarudite and seems to represent erosion of past lower conglomeratic limestones. Here the history seems to be: 1) Thrusting and folding lifting area above sea; 2) erosion and deposition of chert and quartzite (et al) conglomeratic; 3) Milder folding and uplift. This seems to be after a period of quiet times, deposition of limestone and orange sandstones (see Coll. 8/24/57/1). 4) Deposition of Calcarudite. 5) Gradual subsidence as indicated by Hess-Leonard beds upward. PG. 72 8/26/57 Hess Canyon Horst. Level compass: up a stream gully - Sect.39a. 1) Igneous intrusive; [Syenite] Rhyolitic? (8/26/57/1) 1 2) Metamorphosed shales and limestones, varying dips as a result of intrusion of #1 below 10'. 2 3) Limestone, slightly metamorphosed but with fusulines, very fetid even if it is metamorphosed; 1'; 8/26/57/2; has mud blebs, crinoid stems, productid brachs. 3 4) Covered, 8', mostly shale probably 9/1/58/5. 4 5) Shale, blue-gray, wood fragments, slightly metamorphosed; 8'; 8/26/57/3. [did not breakdown, thrown out]. 5 6) Shale, brown, fairly silty; with 3"-6" calcarenite zones. 3'. 8/26/57/4 - calcarenite zone at base. The beds here are in a little syncline and they come up higher in the stream gully. PG. 73 Sect.39b, east 50 yards, across a fault in which 75' of section is removed (fault isn't there). This removed interval is covered on West side of fault. [ 7) Covered, 75' probably like #6.]