Field Notebook: Texas 1957a
Page 254
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Transcription
PG. 129 7/22/57 5) Limestone, with 30-40% chert (and quartzite) pebbles - gray to gray-brown weathering; a few limestone pebbles. 3' beds, from about middle of unit upwards, large limestone cobbles appear, a few horizons are nearly sandy (coarse); 46'. It should be noted that the upper 2/3 of this unit could probably best be called a conglomerate. The limestone is nearly completely lacking except as cobbles in the upper half. About 5% of less of the upper rock unit is limestone cement. 6) Covered for most part, exposures are conglomerate, chert and quartzite, limestone cement. One big limestone block at 38' (Collection 7/22/57/2) 145' - I'm separating this as a unit only because of the weathering characteristics. 7) Conglomerate, poorly sorted to no sorting, chert, quartzite, limestone pebbles; some small cobbles - lime cement. Mass, cliff forming. Become coarser (small to medium boulders) upwards. 84', 1' to 20' beds. 8) Covered - 65' this is probably the extension to the west of the green-gray shale and calcarenite tongue. PG. 130 9) Conglomerate, brown and gray weathering. Limestone, chert and quartzite pebbles, brown sands, not sorted; base is covered. 3' or more (7/22/57/3). 10) Calcarenite, dark brown weathering. Zones of pebble (10%) in calcarenite. 2" to 2' beds very irregular channelling in top of bed 10. 22'; has a flat top, siliceous clastics are dominant. 11) Conglomerate, chert, quartzite and limestone; limestone locally dominates to make this a calcarudite but chert and quartzite dominate elsewhere (with 5' horizontally). (7/22/57/4) 35' up predominantly limestone in the upper 10' (>50%) has brachs, bryozoans, crinoid stems and coral, besides the fusulines. I think it could be called near biohermal both in formation and position during Pm. 49'. Brown and dark to medium gray weathering. Has blocks and small lenses of light brown silty which weathers out leaving vuggy appearance. PG. 131 {note: illustration: bed 6: 7/22/57/2 bed 9: 7/22/57/3 bed 11: 7/22/57/4; 7/22/57/5 bed 12: 7/22/57/6 bed 19: 7/22/57/7 bed 21: 7/22/57/9 bed 24: 7/22/57/8} 12) Calcarenite, medium gray weathering; has granule size organic fragments, 6'. Collection 7/22/57/6, 2' beds. 13) Partly covered - apparently alterations of brown silt and sandstone and calcarenites. 3 cycles - 6'; 6" to 1' limestone.