Geology and Mineral Resources of Paraguay A Reconnaissance

SEDIMENTARY ROCKS 73Records of wells drilled by Union Oil Company in the Gran Chaco,western Paraguay, 1944 to 1949, inclusive ContinuedOrihuela well B-l Continued(fee?) SSSand, muddy, 1.5 ft, red, fine- to mediumgrained;1.5 ft red siltstone and shale,with some quartz pebbles._____________ 10Sand, fine-grained, silty, and sandy siltstone-_ ______________________________ 10Sand, soft, micaceous, brilliant red, finegrained______________________________40Sand, soft, friable, red, fine-grained_ _ -____ 110Shale, red____________________________ 40Siltstone, sandy, light-red; fairly hard attop, grading downward to softer andsandier material____________________-_ 70Sand, soft, friable, silty, brilliant-red-__-__ 60Siltstone, sandy, soft fine sand, and thinlayers of clay, all bright red; a little hardDepth(feet)3,8903,9003,9404,0504,0904, 1604,220limy sandstone 10 to 20 ft above base___ 240 4,460Sand, silty, bright-red, fine- to mediumgrained____________________________770 5,230Sandstone, hard, fine-grained, light-red-___ 10 5, 240Sand, soft, friable, silty, bright-red, micaceousnear base_____--__-_---__-__--__ 50 5,290Siltstone, sandy, hard, red; with black stainsof an unknown mineral._______________10Sand, silty, bright-red___________________ 150Sandstone, hard, fine-grained, light-red-___ 10Sand, silty, soft, red; with laminae of clay__ 50Siltstone, sandy, bright-red; with laminaeof clay ______________________________Sand, soft, friable, silty, fine-grained;with a few laminae of clay_____________ 170Shale, dark-red_________________________ 10Sandstone, fine- to medium-grained, reddish-gray.- __ _________________________Sand, soft, friable, silty, fine-grained, lightred_______-__________________46Siltstone and shale, bright-red.___________ 94Sand, soft, friable, red, fine- to mediumgrained-_____________________________ 180Siltstone, sandy, bright-red; with abundantanhydrite and pebbles of quartz ________ 150Sand, soft, silty, fine-grained, red; withangular pebbles of quartz______________ 60Siltstone, sandy; with laminae of red shaleand abundant pebbles of quartz ________ 465,3005,4505,4605,51010 5, 5205,6905,70010 5, 7105,7565,8506,0306, 1806,2406,286Records of wells drilled by Union Oil Company in the Gran Chaco,western Paraguay, 1944 to 1949, inclusive ContinuedOrihuela well B-l Continued(fee()Quartz, white, and quartzitic sandstone,with fragments of red siltstone and ofpale-green shale. __ ___________________ 255Sandstone, quartzitic, fine-grained; withstains of iron oxide____________________ 174FOSSILSDepth(feet)6,715The following record of fossils recovered from thePicuiba well was given to the writer by Dr. Horacio J.Harrington and is published with his permission.Fossils from Picuiba wellMetersDepthsFeetTop of Devonian_-___________________ 1,187 3,893Plant remains, indet-_________________ 1,207 3,959Calamitean stems and wormburrows__ _ 1, 273- 4, 175-4, 1791,274Cyclostigma sp______________________ 1,290 4,231Palaeoneilo sp________________________ 1,333 4,372Crinoid stems (very similar to thosedescribed by Steinmann from the lowerDevonian of Bolivia)________ 1, 394-1, 398 4, 572-4, 585Wormburrows and very small Cruzianaliketrails______________________ 1,490 4,887Brachiopod indet. and plant remainsindet__________________________ 1,502 4,926Crinoid stems, like those of level 1,394__ 1, 509 4, 949Hadrorhachus australis (Clarke)_______ 1, 561 5, 120Crinoid stems, like those of level 1,394__ 1, 628 5, 340Tentaculites crotalinus Salter and Australostrophiamesembria (Clarke)____ 2, 020-2, 022 6, 625-6, 632This record indicates that the Lower Devonian bedsextend downward at least as deep as the 2,022-meterlevel and Harrington writes that he "would not besurprised to learn that the lowermost 500 meters of thewell are also lower Devonian." The following tableshows that there is also a very thick section of LowerDevonian beds in the Santa Rosa well. This recordis taken from a report made to the Union Oil Companyby Harrington and made available to the presentauthor by the Paraguayan government.