20b<strong>ut</strong> the handholds are unstable requ~r~ng that the drop should be rigged(75' rope) <strong>for</strong> safety. This is followed by a 35-foot chimney, aID-footclimbdown, a 40-foot, offsetting drop ( 50' rope), and a 20-foot drop(3D' rope). More climbdowns and a short, narrow passage soon encounter atight slot which opens into a l4-foot climbdown where the FloodwaterRo<strong>ut</strong>e is joined. The Crystal Room Ro<strong>ut</strong>e is the one normally rigged. Althoughthe Floodwater Ro<strong>ut</strong>e is more direct, it requires rigging longerdrops through razor-sharp passages. From the junction of the two ro<strong>ut</strong>es,a climbdown and a short passage lead to the top of a 30-foot drop. Thisdrop can be rigged, b<strong>ut</strong> it is usually bypassed by doing an exposed traversealong the left wall to a 25-foot chimney. Below this drop, thepassage splits where the water takes two parallel ro<strong>ut</strong>es. On the left aclimbable, small-diameter tube drops 40 feet be<strong>for</strong>e it becomes too tightand jagged <strong>for</strong> com<strong>for</strong>t (it could be pushed, however). On the right side,a tube 10 feet in diameter drops 100 feet vertically, via a series ofclimbdowns , to a 25-foot-long crawlway. This crawl leads to a hole whichopens into the top of a fissure. It is possible to slip through the holedown to a ledge which provides a rigging point. Below is an BO-foot dropto a partition, and although it is "climbable," it is better to rig itwith a ISO-foot rope which will reach past the partition to the bottomof the fissure. On the left side of the partition (unmapped), the fissuredrops abo<strong>ut</strong> 20 feet to a lake where exploration was stopped by a constricted,razor-edged crawl. On the right side of the partition, the 3foot-wide fissure drops 15 feet to a window. Through the window, the fissuredrops 25 feet to a ledge and then 15 feet to the present deep point inDiamante, 907 feet below the entrance and 373 feet above the estimatedbase level. Here the fissure is 1.5 feet wide and 5 feet long. It continues4 inches wide at one end and drops through an 8-inch-wide hole at the otherend. Rocks dropped through this hole can be heard to rattle downward <strong>for</strong> ashort distance. This hole could only be enlarged by explosives, and eventhis would be a difficult task.Observations on Cueva de Diamante and the Mine AreaDiamante is a complex <strong>cave</strong> with an interesting history. The entrancepassage appears to be an old phreatic tube which intersected a zone ofintensely shattered bedrock in the Frog Falls area. The Shatter Zonepassages exhibit angular limestone blocks of great size range which havebeen recemented together. Resol<strong>ut</strong>ion of the zone has produced razor-sharppassages which demand that explorers wear gloves and carry rope pads. TheShatter Zone passages lie directly beneath the dolina, which supports thetheory that faults and shattered bedrock have localized the <strong>for</strong>mation ofthe large sinkholes found along the crest of the Sierra de El Abra. Incontrast, the Canyonland Section is <strong>for</strong>med along joints and is basicallyhorizontal, extending completely under the Dolina to the north be<strong>for</strong>e dipping60 eastward along a vertical joint. Such a dip in this location wouldsupport the theory that the EI Abra's eastern scarp is an anticlinal feature.Canyonland appears to be the oldest section of the <strong>cave</strong>. The floor isdeeply entrenched in places. Pleistocene mammal remains (horse, bison, andmammoth) were discovered in an eroding gravel bank in one area, however,most of the Canyonland is scoured clean. Canyonland still takes some floodwater,b<strong>ut</strong> most of the water is now pirated by the Fracture Zone passages,all of which are actively developing except <strong>for</strong> the abandoned Crystal RoomRo<strong>ut</strong>e. In the lower level of tbe Fracture Zone (once referred to as HandburgerHill), the water becomes divided among three passages which all pinchdown to razor-sharp crawls, ending exploration.
21In March 1975, a trip was made to continue exploration in Diamante.An approximate depth of 900 feet was reached via Crystal Room ro<strong>ut</strong>e. Therewas a minor accident below the Crystal Room when a handhold broke loosecausing a <strong>cave</strong>r to fall 15 feet. The miners also showed this group a newpit (Casi Mil) between the Diamond entrance and the mining camp (See AMCSAct. News. 2:7).In June, a two-man team returned to the mine and explored the newpit. They estimated the depth at 735 feet and thus named it Casi Mil(almost 1000 feet), reported in AMCS Act. News. 3:5.Mid-July saw a special trip to the area with the purpose of locatingthe elusive black hole. This group rediscovered Cuesta by using a "ParrotBearing" 'as recorded in AMCS Act. News. 3:8,9 (Air-recon. has finallydetermined the non-existence of any black holes near Cuesta).The most recent trip to the area was during Christmas 1975. Diamondwas extensively explored and surveyed to a depth of 907 feet. Casi Milwas re-surveyed to a depth of 495 feet and re-named Casi Media Mil. Finally,a surface survey was made which connected the four <strong>cave</strong>s near the mine. Theblock diagram with this article combines all of the survey work which hasbeen done in this area to date (See Trip Reports in this issue and in D.C.Speleograph, April 76:3-5). .Geologic SettingThe east face of the El Abra drops steeply down to the coastal plainproviding a spectacular view from abo~e the Otates Mine. John Fish haspostulated that the east face is a fault scarp, while William Russell hasargued that it is a steeply diPRing anticline. The block diagram depictsit as an anticline which sinks beneath the shale <strong>for</strong>mations of the coastalplain. Also shown on the diagram are the two facies of El Abra limestonewhich have been described from other locations in the Sierra. The massive,unbedded reef facies <strong>for</strong>ms a narrow band along the eastern margin of therange. while the back-reef facies is thick-bedded and dips gently to thewest <strong>for</strong>ming the plateau surface. Many <strong>cave</strong>s (most with phreatic origins)have developed in areas of faulting and intense fracturing which resultedwhen the range was folded. All drainage on the El Abra is internal. Baselevel <strong>for</strong> the mine area is the Nacimiento de Rio Tantoan, a large springat the base of the range. This gives <strong>cave</strong>s on the plateau a maximum verticalpotential of abo<strong>ut</strong> 1500 feet. Cave elevations on the diagram are elevationsabove this projected base level.Sotano de Otates and the Mine ValleyThe 125 foot entrance pit (150' rope) to Sotano de Otates is locatedon the £1 Abra's east face just below the Otates Mine. In fact, the mineis currently dumping its tailings into the Otates entrance, and the <strong>cave</strong> mayeventually be plugged. At the bottom of the entrance drop is a large room,from which a water channel follows a steeply sloping passage east severalhundred feet to a handline drop (40' rope). This is immediately followed bya narrow 600-foot shaft (625' rope) which divides several hundred feet fromthe bottom. Exploration of this drop has been difficult, and both ro<strong>ut</strong>escurrently end in sumps. The lower sump is 800 feet below the entrance.John Fish (1975) has typed many of the <strong>cave</strong>s on the El Abra's eastface as "paleo-phreatic resurgences" -- <strong>cave</strong>s which were springs' when baselevel <strong>for</strong> the area was at a much higher level than today. Otates would fitthis category quite well. It is of phreatic origin, and the deep verticaltubes or shafts would have served to circulate water up from great depths.
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ASSCCIATION FOR MEXICAN CAVE STUDIE
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3So the large-entranced sotano whic
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5MINA OTATES, T&~.: DSC. 25, 1974,
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MERIDA, YUC.: OCT. 1974, David McKe
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AMCSMEMBERSHIP ACTIVITIES LETTEREdi
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3Michael Schulte has been working o
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5To the right of the partition in t
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7Diamond Cave RevisitedAndy Grubbs,
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9CHE~-VEN-SIL-MUTSYSTEM\+--1000 ft.
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Cave Map Symbols11On the following
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13I NATIONAL SPELEOLOGICAL ISOCIETY
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ASSOCIATION FOR MEXIC&~ CAVE STUDIE
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17Discussion of Map Symbolsby Bill
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19in a 90 meter pit could collect d
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AMCSACTIVITIES LETTEREdited by Bill
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3After leaving Valladolid we went t
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- Page 41 and 42: June 97Dear AMCSRE:Diamond CaveAfte
- Page 43 and 44: Anyways we speleo-boppedEstrella an
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- Page 47 and 48: 13Sotano Hondo de Pina1itoBy Steven
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- Page 77 and 78: 11First Exploration of NogalThursda
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- Page 83 and 84: 15Trip Report, Christmas-New Years
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- Page 133 and 134: The Fissure t..as located by T.P.
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16NEW YEAR'S DAY IN SAN AGUSTINan t
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1'1later Jim and I began the long c
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20Our group of six intended on rapp
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22here and poked around for leads.
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24and myself about trash and abando
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line didn't cross; nylon against ny
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...'"1IIc.21II .._1II~(,),-• c..'
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30Medical Report On The April 1977
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'32One caver alInost lost her voice
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34considered normal. The diabetic d
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36Jim Smit~ Has followinp, Blake Ha
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3~the spot would make a smaU slip.
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AMCSACTIVITIeSNewsLe TTe Rno. 7
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'International NewsTHE SIERRA DE GU
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International Newsin the entrance a
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The Ten Deepest Caves in Mexicoby B
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to a drop. t returned and dropped a
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to the entrance. From San Andres we
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stove in a semi-catatonic state. He
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above the roaring cascades. At time
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With two leads 'beckoning we began
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Chaining a passage in Cueva de Infi
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the cave. We pulled our rope down b
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increased the cave's depth to -197
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series of parallel ascending (+30 0
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La Sistema Purificacidn: a theory a
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Between the Cold and the" GlorybyTe
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Back tothe Bird PitsbyBill StoneSum
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'Getting Down in Peiiaby Bill Stone
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CUEVADELAPENAPROFI LEmetersoRanc ho