17MB PDF - Association for Mexican Cave Studies

175large horizontal passage about 100 feet above the resurgence ofthe river. The Sotano de Gomez Farias, a deep system of rooms,passages, and interconnected pits, gives evidence of a complexhistory. Not enough work has yet been done in the area south ofCd. Victoria to fully clarify the history of cavern development,but it appears that most of this development has been the vadoseenlargement of poorly integrated phreatic voids. Due to the heavyrainfall and high relief the eastern face of the range is characterizedby the formation of numerous deep pits. Apparently thereis a greater amount of horizontal passage near the present baselevel. This might have been expected from geologic considerations,as the resurgences at the base of the mountains are only a fewhundred feet above sea level and probably have remained at theirpresent level since the end of the uplift of the area associatedwith the Laramide Orogeny. Whether there are other zones of horizontaldevelopment or if water entering the limestone far from theresurgences continues downward to almost the level of the resurgenceare problems only further exploration can answer.Extending from the southeast end of the Sierra de Guatemala isa much lower, relatively narrow cuesta-like range, the Sierra de ElAbra. This range, about 5 miles wide and 70 miles long, extendsfrom north of Cd. Mante, Tamps. to south of Cd. Valles, and containsthe most extensive cavern development so far discovered ineastern Mexico. Several caves exist with an explored length ofover one mile, and the longest, Sotano de la Tinaj~contains overtwo miles of surveyed passage. Exploration has been concentratedin the relatively small Los Sabinos area just north of Cd. Valleswhere 6 large caves are known in an area of less than 10 squaremiles. The southmost cave of this area is S6tano de Montecillos.The cave is located at the end of a normally dry arroyo, and isentered by a vertical drop of 45 feet. At the bottom of this dropthe largest horizontal passage leads 150 feet to a 140 foot dropinto a large passage. Only about 300 feet of this passage havebeen explored, as exploration was halted by deep pools. Anotherpit approximately 1200 feet up the arroyo from Sotano de Montecilloshas been named Sotanito de Montecillos. This pit drops 110feet into a series of horizontal passages averaging about 15 feetin diameter. Over 2000 feet have been explored with no end insight. About a mile north from the Sotanito is located s6tano dela Tinaja. A normally dry arroyo also enters this cave, the slopebeing more gradual, and no equipment is necessary. Exploration inthis cave is more advanced than in any of the others in the area,with over 2 miles of passage surveyed. Most of this cave is composedof large horizontal passages, one of which appears to havereached the water table 445 feet below the cave entrance, which isabout the same level as the nearest ~esurgence. other passagesend in fill or perched siphons, but the cave is not yet completelyexplored. On to the north of S6tano de la Tinaja is s6tano delArroyo, with over one mile of surveyed passage. An arroyo alsoenters this cave, the flood water following the main passage downa series of small drops for about 3/4 mile. Here exploration hasended at a short drop into a pool, with the passage apparentlycontinuing beyond. About 1 1/2 miles north of Sotano del Arroyois S6tano del Tigre, also located at the end of a large arroyo. Aseries of drops descends 300 feet to a short passage that leads toanother drop which has not been descended. Just east of this caveis Cueva de Los Sabinos, the only large cave in the area that doesnot receive flood water. This cave appears to be an essentially