Sotano de las Golondrinas

Description

BULLETIN 2 of the Association for Mexican Cave Studies

EDlTED BY

TERRY W. RAINES

Austin, Texas, U. S. A.

August 1968 Copyright ([) 1968 by Association for Mexican Cave Studies

PDF reprint from scans of the original, February 2011. The text in this PDF has been “read” by Adobe Acrobat and is searchable to the extent that the OCR was successful. This bulletin has been largely superseded by AMCS bulletin 10, Caves of the Golondrinas Area, by Peter Sprouse and Jerry Fant, 2002, but it, especially the color photographs, remains of historical interest. INTRODUCTION

Sotano del a s Golondrinas is s eparat e envelope. A two-color presently the deepest known free­ cave map is also included with this fall pit in the world. Unlike other Bulletin to further illustrate Sotano "free-fall" record holders, the drop de las Golondrinas. in Golondrinas is completely free. Many people contributed to the There are no ledges or climbing successful publication of this Bulle­ against a wall. The pit was fir st tin. Of greatest assistance were entered during April of 1967 and the officials and residents of the later surveyed during June of that Aquismon area who granted per­ year. Previously, the greatest drop mission and aided our explorations. that had been descended by cavers John Fish and Bill Russell donated in the Western Hemisphere was their tim e and knowledge to the slightly over 500 feet. The 1094 writing of two sections of this Bul­ foot drop in Golondrinas more than letin. John wrote the Cave Descrip­ doubled this old record and thus be­ tion and Speleogenesis and Bill not came a real challenge to equipment only wrote the Regional Geology but and technique. Using methods of also donated mor e time to the as­ rappel and prusik previously em­ s ern b 1 i n g of the Bulletin. Carl ployed in other Mexican sotanos, Kunath, aided by John on the cave Golondrinas was succes sfully ex­ map, is responsible for drafting all plored without difficulty. the illustrations. Bill Deane fur­ In the following pages of text, nished Figures 4 and 5 of the photo­ the sotano itself is described, as graphs and Carol Russell offered well as the area in which it is locat­ her skill as proofreader. Other ed and the early explorations. A people serving in helpful capacities short section is also included which were Gill Ediger, Michael A. San­ describes the climbing equipment born, and members of the Univer­ and techniques that have been us ed. sity of Texas Speleological Society. At the very end of this booklet ar e To all of the above people I am descriptions of the eight full-color deeply indebted. photographs that are contained in a TWR

TABLE OF CONTENTS

LOCATION ••••• • • • • 1

CAVE DESCRIPTION and SPELEOGENESIS • 3

REGIONAL GEOLOGY. . 6

HISTORY.. •• •• •• 16

EQUIPMENT and TECHNIQUES •• 18

PHOTOGRAPHIC DESCRIPTIONS. • • 19

1 LOCATION

Sotano de las Golondrinas is lo­ las Golondrinas must be obtained cated in the east-central portion of in writing in the form of a letter of Mexico in the southeast corner of introduction from the Presidente of the state of San Luis Potos{ (lat 21 0 the Municipio de Aquismon, whose 36'N.; long 990 06'W.). This un­ office is located in the building on usual pit has forrned deep in the the nor t h side of the square in heart of the Sierra Madre Oriental, Aquismon. Identification indicating a rugged range of mountains extend­ affiliation with a university or other ing north into the Big Bend area of institution of higher learning usual­ Texas, U. S. A. and south, far into ly expedites matters. After an in­ the state of Veracruz. To the east troductory letter is secured, a low coastal plain contrasts sharp­ arrangements for the hi k e west ly with the high mountains, while to must be made. In the past cavers the west the Central Plateau is only have customarily carried their per­ 3000 feet lower than the 9000 foot sonalgear and hired a local guide to high peaks of the range. carry the climbing ropes. Fifteen The only town in the Golondrinas pesos a day is considered a fair area that is accessible by motor ve­ wage for this service. Mules may hicle is Aquismon (see Geology sec­ also be hired to carry equipment. tion, page fig. 2). It is located They rent for 20 pesos each per day at the eastern base of the Sierra and a guide who cares for them is Madre, 51 km by road south of Ciu­ normally paid 15 pesos per day. dad Valles, S. L. p. Aquismon, the The main trail to all points west commercial and political center of begins its steep climb immediately the area, is reached by a short at the edge of Aquismon. Following paved road leading west from High­ this trail one must surmount two way 85, the Inter-American Highway. mountain ranges, cross two valleys, All travel west of Aquismon is by and partially ascend a third range. foot or horseback on a network of At this point the village of Tamapatz trails that interconnect all inhabited is reached, approximately 11 km places. These trails are often steep from Aquismon. It is absolutely es­ and rocky, though all main trails sential that all cavers go directly to are traveled by pack animals. Lack Tamapatz where they must present of dependable surface water limits the letter of introduction to the Juez settlements to a few areas. In these Auxiliar. Official permission to ex­ areas fields are cleared by cutting plore caves in the area will be ac­ and burning; corn is then planted on knowledged, and any aid or direc­ what soil may be found. Coffee is tions the caver may need will be en­ grown extensively, and there are thusiastically given. From Tama­ small fields of sugar cane. The patz it is a 4 km hike northwest to western part of the Golondrinas area Golondrinas. The entrance is some­ is highe r and drier, with hardwoods, what obscured by dense tropical ve­ and at higher elevations, pines; in getation, but the people of the area the lower, more humid area to the are very helpful in giving directions. east the vegetation is more varied Before entering the Golondrinas and tropical. area, the caver should be aware of Permis s ion to enter Sotano de some of the conditions that exist. 2

Hiking is very exhausting for those without saying that all cavers ITIust not accustoITIed to it. The teITIper­ respect the local custOITIS and al­ ature is frequently above 90 degrees ways r eITIain courteous and polite. and high hUITIidity prevails. A hat The caving potential of the ar ea is and salt are necessary. When cav­ too great to allow avoidable inci­ ing between June and SepteITIber (the dents to jeopardize public relations. rainy season) heavy daily showers In order to keep Mexican caving on should be expected. CaITIping is a firITI basis and to insure that your pos sible in unus ed fields and occa­ group will have the latest informa­ sionally in shelters. PerITIis sion tion on the caves of an area, contact ITIust always be obtained. It goes the AMCS when planning a trip. CAVE DESCRIPTION and SPELEOGENESIS 3

Sotano de las Golondrinas (Pit When one looks over the edge, of the Swallows) lies near the east­ the shape of the pit presents an op­ ern base of the Sierra de Union (see tical illusion such that the walls Geology section, page 8, fig. 2) at look nearly vertical and the floor an elevation of about 2400 feet (740 seems not much larger than the en­ meters). The local people applied trance ar ea. Only when one has rap­ this name because of the tens of pelled several hundred feet does the thousands of swallows that inhabit pit corne into its proper perspective. the pit. Seeing the swallows and Reaching the bottom is like entering the beautiful green parrots slowly another world. The nearest wall is circling as much as a thousand feet 200 feet away. After heavy rains below the entrance is a breathtaking small waterfalls pour from openings sight. a thousand feet above. During the The nearly circular entrance is day no artificial light is necessary on a steep mountainside and has 109 because of the large amount of sun­ feet (33.2 m) of relief. It measures light that enter s the pit. Becaus e 205 feet (62.5 m) by 160 feet (48.8 m) Golondrinas is located south of the and is surrounded on three sides by Tropic of Cancer, a beam of sunlight trees and dense undergrowth. The shines directly on the floor for sev­ lowest side is a barren ar ea of kar­ eral hours a day during the summer ren cris scrossed by many narrow months, causing a curious phenom­ fis sures up to 15 feet deep. Only on enon. Sunlight warms up the guano­ the low side is it convenient to rig covered floor and a cloud several the pit. hundred feet high forms, slowlyos­ In1967 when Sotano de las Golon­ cillating up and down (see Photo­ drinas was explor ed and mapped, it graphs, fig. 6). The floor has an was (and perhaps still is) the deepest area of about 6 acres, a little more free-fall pit and the largest shaft than the average city block, and is known in the world. Because of the 1000 feet (304.8 m) long by 440 (134.1 importance of the pit, a plane table m) wide. Weathered guano and scat­ and telescopic alidade were used for tered breakdown co v e r the entire surveying and a wire with negligible floor. In places the guano (from the stretch employed for measuring the swallows) is several feet thick. The vertical drop. The walls of the pit bottom has 246 feet (75.0 m) of re­ bell out rapidly, giving a free drop lief, with several hills ofbreakdown, at any point around the entrance. As intermittent streams, and a deep may be seen on the map, the short­ trough along the south wall. The est pos sible drop is 1091 feet (332. 5 lowest point in the cave lies in the m) free-fall. The usual rigging trough and is 1306 feet (398.1 m) be­ point is 1094 feet (333.5 m) above the low the entrance. floor and the maximum drop is 1235 The origin of Sotano de las Go­ feet (376.4m) free-fall. These mea­ londrinas is not yet fully understood. surements have a little more mean­ The factor s controlling the localiza­ ing when one realizes that the Empire tion of the pit and their r elative im­ State Building would easily fit into portance cannot be evaluated without this sotano and its top would be about m 0 r e information. A n extremely level with the high side of the ent­ large quantity of unsaturated water rance. had to be supplied to produce such 4

an imITlens e chamber. Considering ably the top 800 feet or more of the the shaft as a truncated elliptic cone, pit has been forITled by collapse as the volume 0 f the pres ent void is indicated by the shape of the pit and about 200 million cubic feet (6 million the lack of solutional featur es. cubic meter s), or five times the vol­ Pre sen t day modifications of urn e of the well-known Gruta del Golondrinas are proceeding slowly. Palmito (Bustamante, Nuevo Leon). Surface drainage does not directly Golondrinas, Hoya de Guaguas, and enter the pit and was not a factor in Sotano de Cepilla--the largest known its formation. Guano, ITlinor quan­ pits of the area--are all developed tities of flowstone, and sITlall pieces along prominent fractures. Golon­ of breakdown below the entrance drinas is elongated parallel to a set (from plant root wedging) are being of northwest-trending fractures that added to the cave, but the rate of may be related to the thrust fault accumulation is very slow. A sITlall and fold west of the pit (see Regional waterfall issues froITl the lower pas­ Geology). The straightnes s of the sage on the west wall and usually south wall in plan view and the 500 sinks quickly in the breakdown after foot sheer wall in section B-B' of depositing some calcite. Following the cave map are controlled by these heavy rains water runs across the joints. Two passages of section floor and sinks in gravel and ITlud in A_A' in the west wall are developed the deep trough along the south wall. along the most prominent fractures o the r s ITlall strearn channels ar e and ar e unexplored. found in the cave, which indicates Evidently, Sotano de las Golori­ that at t i ITl e s small s prings pour drinas was formed by: 1) develop­ into the cave and SOITle erosion oc­ ment of a large phreatic rOOITl, and curs . The floor of the alcove in the 2) collapse of ceiling and wall rock. west wall has been eroded by water The floor of the shaft is composed flowing into a tiny hole, leaving a entirely of breakdown and guano, and prominent ridge in the breakdown is 225 to 275 meters above the near­ and guano. It is quite likely that the est resurgences, 15 km away. It is pit is being deepened by subsurface likely that the bedrock floor of the solution of breakdown and gradual phreatic chamber is two or three subsidence 0 r slumping. ReITloval hundred feet or more below the low­ has apparently bee n concentrated est point in the cave, and the walls along the south wall, producing the may have extended upward to the large trough and a 60 foot cliff of present breakdown surface or even recemented breakdown. For sub­ above it. Collapse of wall and ceil­ surface solution of breakdown to be ing rock began when the roof became imp 0 r tant, a 1 a r g e quantity of unstable, and proceeded slowly until groundwater w 0 u 1 d be required to the surface was intersected. The flow through the old phreatic cham­ major joint set and per col at i n g ber, sin c e the waterfalls provide g r 0 un d water undoubtedly greatly only a minor amount of water. assisted the collapse process. The Sotano de Cepilla, near Tama­ fragmented limestone that collected patz, presents a history siITlilar to at the bottom could readily be dis­ that hypothesized for Golondrinas. solved if the water chemistry was The walls recede sharply froITl the appropriate, because of the increas e small entrance to for m a pit 300 in limestone surface area. Prob- feet in diameter and nearly 500 feet 5 deep at the lowest point. One wall large, deep phreatic chamber and ofthe pit is composed of recemented s top i n g of ceiling and wall rock. breakdown, which is now collapsing. When there has been extensive solu­ About one-third of the floor is cov­ t ion 0 f the breakdown by ground­ ered by active flowstone deposited water a deep pit has formed. Prob­ from waterfalls, and calcite is form­ ably the same fractures that domi­ ing in a I a k e at the bottom. The nate the shape of the pits also con­ rest ofthe floor is covered by break­ trolled the groundwater flow through down and conglomerate (from the the deep phreatic rooms when they wall of conglomerate). In a low por­ were formed. Although the detailed tion of the floor much of the break­ sol uti 0 n chemistry and hydrology down is "rotten" becaus e of solution have not been worked out. it appears and the floor appears to be subsid­ that Golondrinas may be deepening ing due to subsurface solution. becaus e of solution of the breakdown Thus, the 1 a r g e pit s in the by w ate r flowing through the old Golondrinas area have had a history phreatic chamber and causing sub­ characterized by development of a s equent subsidence. 6 REGIONAL GEOLOGY

INTRODUCTION STRATIGRAPHY

Sotano de las Golondrinas lies in Regional Relations one of the largest and best developed }vlexican karst regions. In an area The stratigraphy of the Golon­ of over 500 square kilometer s from drinas ar ea is dominated by the Xilitla north to the RIO Santa Marfa, t hie k accumulation of Cretaceous solutional processes have shaped limestones. Thes e rocks were de­ the landscape and surface drainage posited in lagoons that border ed the is absent. The southern part of the sea during Cretaceous time, where area is a high mountainous plateau the deposition of sediment kept pace with peaks extending to elevations of with subsidence to form s eve r a 1 over 2900 meters. This high area thousand feet of limestone. Most of is separated from the lower ranges this sediment was deposited as lime to the north by an east-west solu­ mud in relatively deep water, but in tional valley. shallow areas, sediment was deriv­ The Golondrinas region of this ed directly from shell reefs. These report lie sin the topographically reefs were not large solid bodies, lower northern area and extends but were unconsolidated shell from Aquismon on the east to the mounds, the individual shell "reefs" San Luis Potosl-Queretaro border being only a few hundred meters on the we s t, and from Tampaxal long. Together with the much lar­ north to Tansosob (fig. 2). This ger volume of inter-reef sediment, ar ea, while mountainous, is lower they formed large calcareous banks, and less rugged than the high area several of which have been named. to the south. Elevations range from To the northeast of the Golondrinas less than lOOmeters above sea level area was the ElAbra Bank that bor­ in the lowlands east of Aquismon to der ed the dee p water to the east. over 1100 meter s at Cerro el Mira­ This bank had a relatively large dor 10 km to the southwest. Three amount of reef material and now subparallel ranges cross the area: forms the £1 Abra Formation that The S i err a de Aquismon and the is exposed along the eastern edge of Sierra de Linja in the east, and the the Sierra Madre Oriental. South­ Sierra de Union in the west. 1 Sepa­ west of this bank and very similar rating these ranges are relatively to it were the Jacala and Sierra flat sinkhole-pitted lowlands. The Ladron banks. These two banks, entire drainage of the area west of tog e the r with numerous smaller the Sierra de Aquismon is under­ banks, now form the £1 Doctor For­ ground, and wit h the exception of mation that extends throughout the small local areas, there is no evi­ Sierra Madre from Cd. Victoria to dence of any mechanical erosion-­ Pachuca. During late Cretaceous even short gullies are abs ent.

1 The Sierra de Linja is also known as the Sierra de Manja, and in the south as the Sierra de Eureka; the name Sierra de Union is us ed principal­ 1 yin the vicinity of the barrio of Union, and locally the range is also called the Sierra de Tamapatz, the Sierra de Mirador, and the Sierra de San Rafael. 7 time large amounts of clastic sed'­ Cretaceous System ments, carried into the area from the west, killed and buried the reefs. The base of the Cretaceous is These sediments now form the Agua not exposed in the Golondrinas area, Nueva, San Felipe, and Mendez For­ but lower Cretaceous limestone of mations. The relation between the the Lower Tamaulipas and Otates formations is indicated in Figure 1, Formations probably underlie much a generalized east-west cross sec­ of the area. These formations are tion showing the formations as they not present to the west where the El existed at the close of the Creta­ Doctor lies dir ectly on the Jurassic, ceous. but they are exposed south of Xilitla and north near Cd. Victoria.

Jurassic System El Doctor Limestone. The El Doc­ tor is the oldest formation exposed Rocks of Jurassic age are not in the area and is by far the most exposed in the Golondrinas area, but widely occurring rock unit. In the are exposed to the south and west Golondrinas area the El Doctor is and probably un de r li e the Creta­ probably 600 to 700 meter s thick, ceous in the area. Thirty kilome­ thinning to the south but thickening ters to the west, near Jalpan, the to the southwest toward the Jacala thin-bedded impure limestone and Bank. The base of the forITlation is black shale 0 f the upper Jurassic not exposed and it is not possible to Las Trancas Formation directly un­ determine accuratelythe local thick­ derlies the El Doctor Limestone ness of this ur:it. Segerstrom (1961) (Segerstrom, 1961). To the south in has estimated this formation to be the canyon of the Rfo Moctezuma, almost 1000 meter s thick in the Ja­ rocks of the bame nature grade up­ cala Bank 30 km southwest of Go­ ward into cherty thin-bedded lime­ londrinas. Heim (1940) gives the stone that underlies the Cretaceous thickness of the El Doctor at Xilitla massive limestones (Heim, 1940). as at least 400 metersand thicken-

------M~E~N~DE=Z--~SlIl.tJRlt.FA&C<.t.E------___ ------::::::;:::::::;;s=::::::::::----- _ ____ ~EXCA~ ------....:..-----7""" SAN FELIPE AGUA NUEVA SOYATAL XlliTLA --- AGUA NUEVA EL DOCTOR

TAMAULIPAS

OTATES

LOWER TAMAULIPAS

GOLONDRINAS WEST AREA EAST

Figure 1. East-west eros s section showing the formations of the Golondrinas area and their equivalents at the close of the Cretaceous. --,

a 2:3 4 ! ! I KILOMETERS Contour Interval 100 meters TopoQrophic Bo.e, Volle. Sheel, 140-e(2), Mexico LlOO,OOO GEOLOGIC MAP OF THE GOLONDRINAS AREA SAN LUIS POTOSI. MEXICO

EXPLANATION

Administrative Cobecero SEDIMENTARY ROCKS Cenler

Town Pueblo ~ Mendez Formation • • Ranch,do en 0 Hamlet Barrio 6 ~ San Felipe Formation W U thrust sheet

1000 1000

til 750-1 Ked 750 a:: ILl .... SIERRA DE LINJA SIERRA DE AQUISMON ILl ~ La ~ 500 500 z Q Ii Ked ILl "...J .... ILl 250 " 250 ...... "';''' "J

Vertical EXac;)1l8ration 3.3 x 0 I SOUTHWEST NORTHEAST

A KILOMETERS A o I 2 3 4 5 4' ;";; I

CROSS SECTION FROM AQUISMON SOUTHWEST THROUGH EL MIRADOR Figure 3 10

ing to the north. Over 500 meters Nueva Formation. In this area the of undisturbed El Doctor is exposed contact is gradational, with the thin­ in the canyon of the Rlo Santa Marla bedded upper El Doctor grading up­ 12 km north of Sotano de las Golon­ ward through a zone of about 10 me­ drinas. Within the Golondrinas re­ ters into a flaggy, more argilla­ gion, the thickest expos ed section is ceous limestone with shale and silt­ in and above Sotano de las Golondri­ stone interbeds that forms the lower nas, where over 500 meters of the Agua Nueva Formation. Approxi­ El Doctor is present. mately 300 meters 0 f the A g u a The El Doctor Limestone of the Nueva are exposed in the vicinity of Golondrinas area is a thick-bedded, Tamapatz. Near Tamapatz the thin­ light gray limestone, with beds us­ bedded flaggy gray limestones and ually from 1 to 2 meter s thick, al­ interbedded marls of the basal Agua though in several places there are Nueva grade upward into a more zones where beds range from 10 to terrigenous unit about 2 00 meter s 30 centimeters thick. A prominent thick. This is overlain by about 50 zone of thin-bedded flaggy limestone meter s of light gray medium-bedded with beds averaging about 15 centi­ limestone with numerous thin no­ meter s thick is expos ed from south dules of black chert. The Agua of Tamapatz to north of Tansosob Nueva is exposed in a belt extending and forms the uppermost 50 meter s from 3 km south of Tamapatz to of the El Doctor. The thick-bedded north beyond Tansosob and out of zones tend to form extensive areas the area investigated. This narrow of lapies, with pinnacles 1 to 3 me­ belt averages about 800 meters in ters in height, and frequently cross­ width and is over 10 km long. The ed by deep, solutionally wid e ned up per Agua Nueva, if present, is joints. covered by an overthrust block 0 f The El Doctor Lim est 0 n e is El Doctor Limestone. compos ed of several different facies The Agua Nueva Formation has that interfinger in a complex rela­ had an important effect on the s et­ tionship. Near reef cores the bed­ tlement of the Golondrinas area, ding is commonly indistinct, while since it is an aquifer from which the thin-bedded zones generally re­ n u mer 0 us springs rise. These present inter-reef areas. Because springs provide permanent w ate r the reefs themselves are only a few for a line of settlements along the hundred meters in length and a few outcrop from Tamapatz to Tanso­ tens of meter s t hie k, the type of sob. In addition the concentrated limestone and the bedding can vary runoff from the Agua Nueva has also greatly over a short distance. As formed several large caves where yet it is not known if solution favors it reaches the soluble El Doctor one facies or type of limestone, but Limestone. it appear s that in the Golondrinas area, fracturing plays a more im­ San Felipe Formation. The San Fe­ portant role in cavern development lipe Formation is exposed in a nar­ than variations in the primary po­ row band along the eastern slope of rosity. the Sierra de Aquismon. In the vi­ cinity of Aquismon the formation is Agua Nueva Formation. Overlying overturned and the lower part cov­ the El Doctor in the western part of ered by an overthrust block of El the Golondrinas area is the Agua Doctor Limestone. The upper San 11

Felipe in the AquisIllon ar ea is a in the cast-west TaIllpaxal Valley thin-bedded, yellow-brown argilla­ that is probably forllled along a Illa­ ceous liIllestonc with generally thin­ jor strike-slip (tear) fault dividing ner interbeds of yellow shales. The the structures of the Golondrinas boundary between the San Felipe and area frolll those of the Xilitla area the overlying Mendez Forlllation is to the south. Evidence for the fault drawn where the flaggy liIllestones is indir ect: the anticlines Clnd thrust replace the obscurely bedded Illarly sheets south of the valley do not shales 0 f the Mendez ForIllation. Illatch thos e to the north, and the The contact is gradational through a southern end of the structures to zone of about 15 Illeter s. According the north of the valley are curved to to HeiIll (1940) this formation over­ the we s t, probably by drag. The lies the El Doctor in the AquisIllon geologic Illap of HeiIll (1940) shows area, the Agua Nueva being absent four closely spaced thrust faults in (fig. 1). the valley near TaIllpaxal, indicat­ ing that this area is structurally Mendez ForIllation. Stratigraphi­ cOlllplex. cally above the San Felipe is the North of the Golondrinas area Mendez ForIllation. In the Aquis­ are two sets of anticlines, the Illain Illon area it is generally a gr eenish, set following the priIllary north­ shaley Illarl with indistinct bedding. south alignlllent of the Sierra Only a slllall part of the thick Men­ Madre, and the other for Illing a dez Forlllation is exposed in the secondary set of northwest-trending Golondrinas area, where this rela­ ranges. These two sets of struc­ tively soft forlllation forllls the low­ tur e sintersect in the Golondrinas lands east of AquisIllon along the ar ea. The tectcnic stres s introduc­ Inter-AIllerican Highway. ed by the LaraIllide Orogeny at the close of the Cretaceous, cOlllbined with the ]Jl.stic nature of the Men­ STRUCTURE dez Forlllation, resulted in the overturned folds and thrust sheets Regional Structure present in the Golondrinas area.

The structur e of the Golondrinas Sierra de Aquis:mon area is dOlllinated by three Illajor elelllents: tl:e overt] rust and asso­ In the vicinity of AquisIllon the ciated overturned anticline forllling :rest of this range is forrned by an the Sierra de Aqu ~ Lion along the overtLr'lst block of El Doctor LiIlle­ east edge of the areCI.; the cOlllplex st.one. The cast edge of the lillle­ anticline that fJrr:"1s the Sierra de stone forllls a prolllinent cJ i ff stand­ Linja; and the overthrust forllling ing above the relatively ~oft liIlle­ the Sierra de Union just west of s6­ stcnes and Inarls of the ~'an Felipe tano de las Golondrinas (fig. 3). All Forrr,2tion. The San Felipe is over­ of these strt'c~ures a:-" roughly pa­ ~urned and dips 20 to 40 cegrees to rallel. They trend to the north in the west under the El Doct,w. The the southern ~art of the area and rocks exposed along the e as t ern then curve to the northwest in a slope of tr.e Sierra de AquisIllC:l. a:;'e broad arc. These structures end the east liIllb of an anticline over­ just to the south of the area Illapped, turned to the east. To the south. the 12.

overthrusting and folding diminish, To the south the range merges with and in the southern part of the area the Sierra de Aquismon to form a the Sierra de Aquismon is an anti­ broad anticline. cline with a steepened east face, the El Doctor dipping steeply to the east Sierra de Union under the San Felipe. Nor t h of Aquismon the range continues as an The Sierra de Union is the most overthrust beyond the mapped area. prominent range in the area and ex­ tends as an unbroken cliff from Ta­ Sierra de Linja mapatz north to San Rafael. This cliff is the east edge of an over­ This range is a complex asym­ thrust block of limestone and stands metric anticline that roughly paral­ over a narrow, frequently talus­ lels the Sierra de Aquismon to the covered outcrop of the west-dipping west. Like many other anticlines Agua Nueva Formation. The over­ of the southern Sierra Madre, it has thrust continues north of Tansosob a steep east face and a gentler west but has little topographic expres­ slope. The range is composed of sion. From just north of Tamapatz several distinct smaller anticlines and continuing south for about 2 km that plunge sharply to form narrow is a vall e y developed along the passes in the range. In the pass strike of the Agua Nueva. This val­ traversed by the Aquismon-Tama­ ley drains to the west into c a v e s patz trail the axis of the anticline to and sinkholes in the El Doctor (fig. the south plunges north at 30 de­ 4). One of the larger of the s e grees and the anticline to the north caves, Cueva de Oxtalja, just west plunges to the south at 70 degrees. of Tamapatz, has developed along The sharp break where these struc­ the plane of the overthrust. This tures meet forms a narrow east­ large cave has a ceiling of mas sive west valley. A sequence of similar El Doctor Limestone and the floor steeply plunging 10 cal anticlines and walls ar e in most places devel­ continues to wher e the range dies oped on the crumpled and contorted out just north of the mapped area. thin-bedded Agua Nueva beneath the

WEST EAST

Figure 4. Section B-B' through valley north of Tamapatz. 13 thrust sheet. The cave follows the GEOMORPHOLOGY plane ofthe overthrust for about one kiloITleter to the west; thus, the EI Doctor in this area ITlust have been Corrasional LandforITls thrust at least this far to the east. The dip of the plane of overthrust Although ITlost of the Golondrinas was ITleasured in several places. In ar ea is underlain by fractured liITle­ the cave, Cueva de Oxtalja, the dip stone, and solution is the dOITlinant averaged 23 degrees to the west, process in shaping the landscape, and one-half kiloITleter north of Ta­ there are a few areas where solu­ ITlapatz the dip was about 25 de­ tion is not iITlportant. East of grees. In an excellent exposure in AquisITlon in the wide valley follow­ the valley just to the west of Tanso­ ed by the Inter-AITlerican Highway, sob the dip was ITleasured to be 22 the soft Mendez ITlarl has been re­ degrees. In both the S i err a de duced to a ITlature topography with AquisITlon and the Sierra de Union only a few rounded hills breaking the beds in the EI Doctor dip steep­ the gentle slopes. The steep out­ ly to the west near the east edge of crop of the San Felipe along the east the overthrusts, but within a few face of the Sierra de AquisITlon is hundred ITleters dip only gently to deeply gullied by erosion that is un­ the west. West of the Sierra de derITlining the cliff of El Doctor that Union ar e several nor t h - sou t h stands above the outcrop. The band structural trends that ITl a y repre­ of Agua Nueva along the east side of sent additional thrust faults, but as the Sierra de Union is s i ITl i 1 a r, only the ITlassive EI Doctor LiITle­ though 1 e s s gullied. The closed stone is involved, the exact rela­ valley along the strike of the Agua tions are difficult to deterITline. Nueva west of TaITlapatz was pro­ duced by corrasion; the erosion by Minor Structures ITlechanical ITleans of the soft Agua Nueva is apparently ITlore rapid than Associated with these larger the solution of the surrounding El structures are nUITlerous sITlall Doctor. folds. Several very tight folds are ex po sed northwest of AquisITlon, Karst where beds of the San Felipe are bent back upon theITlselves in less Solution of the El Doctor LiITle­ than a foot. CruITlpling and chevron stone in the Golondrinas area has folding are also present in the thin­ produced a wide variety of land­ bedded upper unit of the El Doctor forITls. The effect of solution is south of TaITlapatz. The thin-bedded controlled by local conditions, pri­ Agua Nueva is cOITlplexly folded and ITlarily the natur e of the liITlestone, cruITlpled beneath the overthrust El rainfall, and local relief, all of Doctor. This drag folding is expos­ which vary widely acros s the area. ed in Cueva de Oxtalja as well as in In the valley to the west of the Si­ the hills capped by EI Doctor just erra de AquisITlon there is little ef­ north of TaITlapatz (fig. 4). fective local relief. Here the sink­ holes are shallow and poorly drain­ ed. After eight days of rain during SepteITlber of 1967 sinkholes in this 14

area were filled with water to and channels for the descending depths of over 10 meters. Water water so plentiful that the entire completely blocked the m a i n trail surface has been reduced by solu­ to Tamapatz and required several tion. It appears that some mecha­ days to infiltrate into the limestone. nism is needed to concentrate the T his entir e valley i s a pparently water to have rapid development of being lowered by solution. Solu­ large caves. No caves are known in tional re sidue collects in the lower the poorly drained lowlands imme­ depressions and the local relief is diately to the west of the Sier ra de not enough to maintain open drain­ Aquismon. In the wide valley to the age channels. The valley to the west of the Sierra de Linja two west of the Sierra de Linja is simi­ caves are known. Satano de las lar, though sinkholes are somewhat Quilas is a circular pit about 100 better developed and there is more meters deep and 80 meters in dia­ local relief. However, the ar ea is meter. Cueva del Camino, 5 me­ still comparatively flat, with the ters off the La Laja-Tamapatz trail, sinkholes covering only a small is alarge passage about 100 meters portion of the surface. long with attractive formations. In the higher ar eas west of the Several large caves exist along Sierra de Union and south and west the margin of the Agua Nueva out­ of Tamapatz, a much more spectac­ crop. To the south is Satano de ular type of k a r s t has developed. Muhaut, a cave about 100 meters Her e there is much greater local long, and Cueva de Muhaut, which relief, and large elliptical sinkholes has been explor ed for about 300 me­ frequently 0 vel' half a kilometer ters and continues. Near Tamapatz long and one to two hundred meter s is the large Cueva de Oxtalja that deep cover the entire sur fa c e. receives the drainage from an ex­ These sinkholes are separated by tensive area. This cave is about sharp narrow divides a~1.d there is 1 km long and 200 meters dee p, little level land. Karren is common though only two drops, one of 25 and haystack hills have developed in meters and the other of 6 meters, the more fractured areas. Further require rope. North of this cave is to the west the sinkholes tend to be­ Cueva de San Nicolas, explored for come larger and more elongate, one-half kilometer to a 30 meter with flat floors thinly covered with drop. North of San Rafael an unex­ red clay. The largest of these is plored cave receives the runoff the La Parada valley, just to the from a long arroyo. west of the Golondrinas area. This The most promising area for flat-floor ed solution valley is 10 km caves appear s to be in the well-de­ long, 1 km wide, and up to 300 me­ veloped karst southwest of Tama­ ters deep. patz. Several promising caves have been entered in this area, but none Caves and Pits of these have been explored for more than a few meters. Considering the amount of rain­ fall and limestone in the Golondri­ nas area, caves and pits are not nu­ HYDROLOGY merous. Apparently in much of the area, solution has been so general It is not known where the large 15

amount of water that falls on the ento) at the end of an isolated lime­ Golondrinas area reappears. The stone hill about 2 km long. Mo st of Golondrinas area is about equidis­ this water must flow under the in­ tant between the series of large tervening basin from the mountains springs that forms the Rfo Huichi­ to the west. The m 0 s t 1 ike 1 y huayan and the Nacimiento del Rfo groundwater divide is the Tampaxal Coy. The headwaters of the Rfo valley, just to the south of the Go­ Huichihuayan ar e located about 15 londrinas ar ea. If this is the divide km to the south of the area, and the then the Golondrinas area rainfall Nacimiento del Rfo Coy is about 15 reappear s at the Nacimiento del Rfo km to the northeast. The Rfo Coy Coy, 15 km away, at an elevation of rises from a large spring (nacimi- about 50 meters.

SELECTED REFERENCES

Bodenlos, A. F., and Bonet,. , F., 1956, Notas sobr e la geologfa de la Si- erra Madre en la seCClon Zimapan-Tamazunchale: In International Geol. Conf., 2 Oth, Mexico. Excursions A-14 and C-6, p. 293-309.

Bonet, Federico, 1953, Cuevas de la Sierra Madre en la region de Xilitla: Bol. Univ. Nac. Aut. Mex. Inst. Geol., 57, 96p.

, 1953, Biostratigraphic notes on the Cretaceous of East------ern Mexico: In Corpus Christi Geological Society Eleventh Annual Field Trip, May 23-26, 1963, p. 36-48.

Corpus Christi Geological Society, 1963, Eleventh Annual Field Trip (Guidebook), Geology of Peregrina Canyon and Sierra de El Abra, May 23-26, 1963, 90 p.

Cserna, Zoltan de, 1961, Tectonic map of Mexico; Geol. Soc. America.

Heim, Arnold, 1940, The front ranges of the Sierra Madre Oriental, Mex­ ico, from Ciudad Victoria to Tamazunchale: Ec10gae Geologicae, vol. 33, no. 2, p. 313-352.

Russell, William. H. and Raines, Terry W., 1967, Caves of the Inter­ American Highway--Nuevo Laredo, Tamps. to Tamazunchale, S. L. P.: Asoc. Mex. Cave Studies, Bull. I, 126 p.

Segerstrom, Kenneth, 1956, Estratigraffa y tectonica del Cenozoico entre Mexico, D. F. Y Zimapan, Hidalgo: In Internat. Geol. Cong., 20th, Mexico, Excursions A-3 and C-l, p. 11-12.

, 1961, Geology of the Bernal-Jalpan area, Queretaro, --~------Mexico: U. S. Geol. Survey Bull. 1l04-B, 86 p.

Wilson, B. W.; Hernandez M., J. p. and Meave T., Edgardo, 1955, Un arrecife Cretacico en la parte oriental del Estado de Queretaro: Soc. Geol. Mex. Bol., vol. 18, p. 1-10. 16 HISTORY

For at least 3000 yea r s the onds. From this they calculated a Huastecans, the original settler s of depth of at least 800 feet. the region, had k now n of the pit. Only three months passed before They called it Xol Oclif. To these T. R. had organized a group to re­ Indians the large entrance and the turn during the first week of April immediate surrounding area was of 1967. Accompanying him were Jon no practical us e. It provided no Morse, Sid West, and Bob Hugill place to cultivate a field and fur­ from Ft. Detrick, Maryland; Bill the r m 0 reconstituted a hazard, Cuddington, John and Sandy Cole, something to be avoided. T h us, and Dan Hale from Huntsville, Al­ little importance was given to this abama; and Squire Lewis, Nancy pit or the manyothers located in the Walters, and Bill Deane from Aus­ area. tin, Texas. This time, possessing When the Spanish fir st viewed it, sufficient equipment, they succeed­ they too attached little importance ed in descending and exploring So­ to this natural feature. To them it tano de las Golondrinas. Initially a was known as Sotano de las Golon­ single rope was rigged and T. R. drinas. The only interest either commenced what was to be a 30 group showed was for the swallows minute rappel. Later, three short­ that inhabited the pit, and from er ropes wer e joined to provide a which the name was derived. They line for prusiking. Using thes e two found great sport in attempting to routes, eight member s of the expe­ spear or shoot the birds. dition descended and returned to the Knowledge of Sotano de las Go­ surface during the two day s the londrinas by organized exploration group was at the sotano. Three of groups has not corne about until re­ them spent the intervening night on cently. The people of Tamapatz re­ the bottom. Most of the prusiking port that a group of six French and was done the second day, the aver­ Mexican mountain climbers went to age time on the rope being 2 to the entrance but did not descend. 2 1/2 hours. The length of a nylon This was in 1957. rope hanging from the rigging point Then, during December of 1966, to the floor was noted and calcula­ T. R. Evans, Charles Borland, and tions were made to allow for the Ranald Stearns, members of the amount of stretch. The resulting AMCS and FTA (Fredrick Troglo­ depth of the drop (at the rigging phyllic As sociation), were guided to point) was 1070 feet. Cons equently, Golondrinas. Lacking the proper Golondrinas bee arne the deepest caving equipment, they were unable known free-fall pit in the world by to descend and had to satisfy their a substantial margin. curiosity by timing the fall of rocks The depth measurements obtain­ and estimating the depth. At first ed from the April expedition were glance the drop appeared to be be­ admittedly not extremely accurate tween 300 and 400 feet deep. By due to several variables. But two measuring the time that elapsed be­ months later, during June, John tween the dropping of a rock and the Fish, Ed Al e x a nd e r, Jonathan sound of it hitting the bottom, they Davis, Dick Mitchell, and Ted Pe­ obtained a figure of 10 1/2 to 11 sec- ter s returned with the purpose of 17 cOll1pleting an accurate survey of of 1094 feet was ll1easured at the the entire cave. To accoll1plish this rigging point. The total depth of the they us ed a plane table and tele­ cave is 1306 feet. Now, certainly, scopic alidade to survey the area the authenticity of the new world I s surrounding the entrance and the record could not be questioned. floor of the pit, while the actual Since these early explorations, drop was ll1easured with a steel a large nUll1ber and variety of wire 0 f little and known stretch. groups have visited t his aweSOll1e The surface survey, the rigging of sotano. The ll1ass pilgrill1age has the drop, and the ll1easur ell1ent with so aroused the interest and suspi­ the wir e r equired one day to COll1­ cion of the local residents that SOll1e plete, while another day was spent bel i eve the strangers COll1e in on the bottoll1 finishing the second search of gold, oil, or other valu­ phase of the survey. The new fig­ able objects. Fortunately, the situ­ ures obtained were sOll1ewhat higher ation has eased and as responsible than those of earlier date. The caver s continue to visit the are a, longest free-fall drop is 1235 feet, public r elations will be established the shortest is 1091 feet, and a drop on a really first class level. 18 EQUIPMENT Jnd TECHNIQUES

As is to be expected, caving is generated will severely damage equipment and techniques vary from the rope. Care should be taken not one individual to another. Virtually to exceed a rate of 40 feet per min­ all methods for ascending and des­ ute or stop at anyone point along cending a drop have been tried and the rope. A rappel of this magni­ tested during the past six years of tude not only affects the equipment Mexican caving. Through an evolu­ but also the explorer. Having a tionary process, the more undesir­ second person pull up the climbing able means have been abandoned, rope a few feet to produce enough until now one system predominates slack to allow the rappel device to ••• rappel and prusik. be attached is very helpful. Once Of primary importance to the on the rope, it is advisable to move succes sful negotiation of a sotano is the legs as much as possible be­ the climbing rope. It is of nylon, cause during the 30 minute rappel varying in diameter from 3/8 inch the seat sling restricts blood circu­ to 1/2 inch. Either 7/16 inch or 1/2 lation. inch have been most widely us ed In addition to a s eat sling, the becaus e of the distasteful amount of prusik method requires only a set stretch and general weakness of 3/8 of two or three loops, depending on inch rope. These ropes are either whether one 0 r two feet are used. laid or braided. In the cas e of Go­ If Jumar Ascenders are used, the londrinas, braided rope was once s eat sling loop is attached too n e thought superior due to the absence Jumar and either one 0 r two foot of spin while climbing. This was loops are attached to the 0 the r disproven when Goldline laid rope Jumar. The length of the drop to be was us ed and only negligible spin ascended does not affect the prusik­ noted. No matter what brand of ing equipment, as it does the gear rope is used, great care should be used in rappelling. The only limi­ taken to protect it against damage tation to the distance that it is pos­ from sharp rocks. sible to prusik is the human energy The amount of equipment neces­ factor. In Golondrinas the average sary for the rappel is not gr eat. A time required to prusik out is 2 to seat sling with a locking carabiner 2 1/2 hours. On the other hand, the is us ed in conjunction with either a distance that it is possible to rap­ set of two oval carabiner s· and break pel is limited to the ability of the bars, or a rappel rack as described rappel device to deal with the weight in the NSS NEWS,v. 24, n. 6, June of the climbing rope. As it appear s 1964. Both methods work well, the now, some new innovation or im­ advantage of the rappel rack being provement of the existing equipment that less feeding is necessary at the will be needed when it becomes ne­ beginning of the rappel. If the rate cessary to descend a drop of more of rappel is too rapid, the heat that than 2000 feet. 19 PHOTOGRAPHIC DESCRIPTIONS

Figure 1. Aerial view of Aquismon, S. L. P. and surrounding mountains. This photograph was taken looking south down the valley followed by the Inter-American Highway. The right side of the photo shows the eastern edge of the Golondrinas area, which is separated by the Tampaxal Valley from the higher mountains (peaks over 2900 meters) in the background. The trail to Tamapatz begins its as­ cent at the north edge of Aquismon and crosses the first range in a pas s just out of the lower right corner of the photo. The geologic for mations are: valley floor - Mendez Formation; slope above Aquismon - San Felipe Formation; and scarps and ridges to the west - El Doctor Limestone.

Figure 2. Westward aerial view of Satano de las Golondrinas. The entrance is located near the base of the Sierra de Union and is quite promi­ nent from the air. The main trail eros sing the center of the photo connects Tamapatz and Tansosob. The 4 km hike from Tamapatz to the pit requires about 1 1/2 hours. The trail leading out of the lower left corner returns to La Laja and Aquisman. Just to the lower right of center three tro:tils meet at Pozo de Guadalupe, the water supply of the local area. The geologic formations o:tre: Pozo de Guadalupe and below - El Doctor Limestone; center cultivated slope - Agua Nueva Formation; and upper cliffs - El Doctor thrust front.

Figure 3. The entrance of Satano de las Golondrinas. This wide angle photo­ graph shows the cornplete entrance with dense tropical vegetation surrounding it on three sides. The surveyed high point of the en­ trance :~s in the upper center above the cliff face, while the usual rigging point is in the middle of the group of people. When pre­ paring the equipment prior to des cent, the rope must be unbraided on the rough karren in upper for eground.

Figure 4. First exploration group. During April of 1967 the pit was first en­ entered. Using 1/2 inch Samson 2 in 1 nylon rope (well padded), an explorer begins the 30 minute, 1094 foot free rappel to the bot­ tom. The man with the white hard hat, closest to the rappeller, uses a walkie-talkie to communicate with an explorer already on the bottom. Extreme caution must be taken when approaching the entrance dne to the uneven, deeply fissured karren.

Figure 5. Descending into the pit. Although only about one-sixth of the way to the bottom, the explorer is already approximately 150 to 200 feet below the camera and the lip of the pit.

Figure 6. The entrance shaft. A small waterfall near the entrance shines white in the sunlight while the climbing rope (center) appears dark. The beam of light warms the moist walls and floor, produc- 20

ing a cloud which oscillates up and down in the pit. The broken appearence of the wall rock and absence of solutional features in­ dicate that Satano de las Golondrinas was formed by stoping of ceiling and wall rock into a large solutional chamber.

Figure 7. Lengthwise view of bottom. The floor of Golondrinas is composed of medium to small weathered breakdown, deep guano, and some silt. It measures 440 feet by 1000 feet and has an area of about 6 acres. In this eastward view a person is standing in the center of the photo for scale. Halfway between him and the left edge the climbing rope is barely visible. The 40 foot long log in left center is in the middle of the projected entrance area (see cave map). This area is lighter in color due to broken rock pieces. The trough in Figure 8 is down and to the right of this photo.

Figure 8. The trough. The lowest point in Golondrinas (1306 feet below the entrance) is located in the trough, seen here in this photo. It is in the shallow arroyo slightly back and to the left of the person standing in lower center. The left wall of the trough is formed by the pit wall, which is sheer for 500 feet. Steep slopes and a 60 foot high cliff of breakdown with silt and guano matrix form the right wall. The cave at lower left extends only 15 feet and ends. In the upper right corner is a somewhat larger alcove (see cave map). Sotano de las Golondrinas

Color Photographs Figures 1 through 8

PHOTOGRAPHY BY

TERRY w. RAINES and BILL DEANE

Figure 2

Figur 4 Figure 5 Figure 6

Figure 8