17MB PDF - Association for Mexican Cave Studies

161Past the first large room (approximately 70 feet high, 125 feetwide, and 470 feet long) which is located just inside the entrance,we descended a fissure with several drops before quitting for theday. The greatest pitch was surveyed to be 74 feet while the totalof the four was 142 feet. (The cave was explored last June to apoint about half way down these drops. For a trip report and de&­cription of S6tano de San Agustin see AMCS Newsletter, v. II, n. 3,p. 57.) Our survey showed that we had explored to a depth of 691feet. At this lowest point was a short pit with a promising pa&­sage leading from the bottom. Also noted was a strong wind blowinginto the cave. It was impossible to keep a carbide lamp litin the narrower sections of the passage. We decided to leave allequipment and ropes in place so that our farthest surveyed pointcould be reached quickly the next morning and exploration continued.While the four of us spent the day in S6tano de San Agustin,Bill Russell located several caves in the San Miguel Do1ina. Thislarge do1ina is located just to the north of the town of San Miguel.(See location map in AMCS Newsletter, v. II, no. 3, p. 61.) At thesoutheast end of the do1ina a steep arroyo leads from below thechurch and enters a steeply sloping cave. This cave was exploreddownward for about 100 feet, With the passage about 20 feet highand 15 feet wide. Floodwater enters the cave and it appears tobe promising. Northward from the cave below the church a fieldslopes toward several dirt sinks at the base of a cliff, none ofwhich appear promising. From the field a narrow pass leads northeastto a circular, flat area at the bottom of the do1ina. On theeast side a small sink leads to a possible cave, and on the westis a large cave entrance by an almost isolated block of limestone.This entrance leads to a series of parallel fissures extendingback toward the dirt sinks. There is a 15 or 20 foot drop at themain entrance but the cave can be entered without equipment througha second entrance, a gully sink around the corner to the west ofthe main entrance. The main fissure extends about 300 feet fromthe entrance as a passage about 25 feet wide and 50 feet high.Before it ends, a window opens into a parallel fissure whose flooris about 40 feet below the window. This lower fissure can beeasily reached by following a small passage downward from the endof the main entrance fissure. A small stream flows over a largef10wstone bank, across one end of the lower fissure, and into asmall muddy craw1waY. North of this fissure cave a gully from thesteep mountainside enters a shallow sink at the edge of a field.From this sink, which is about 5 feet deep, a low, horizontal,elliptical passage extends for about 200 feet to a 40 foot pit.This passage gradually enlarges and is walking-size before the pit.Due to the lack of equipment this pit was not explored but estimatedto be 60 feet deep.29 December We hurriedly entered S6tano de San Agustin in orderto escape the dense fog and lOW-lying clouds that are so characteristicof the rainy season of the summer months. Once inside ittook less than one hour to reach the -691 foot depth of the daybefore. With Ed running the Brunton, Tom and Tommy handling thechain, and I sketching, we proceeded down the next drop. The 48foot rappel brought us to the beginning of another section of horizontalpassages. This was evidently one of the main routes floodwater took because the walls were scoured clean and the floor wascovered with rounded stones up to 8 inches in diameter. A "Tit intersectionwas encountered 237 feet from the drop at a depth of