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Sierra de las Quijadas National Park

Date of Submission: 24/02/2005
Criteria: (vii)(viii)(ix)
Category: Natural
Submitted by:
Delegacion Permanente de la Republica Argentina ante la UNESCO
Coordinates: S 32°25' and 32°44'W 67°17' and 66°58'
Ref.: 2021

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3.1.1. Geological description

The Mesowic basins of the central western part of Argentina (Ischigualasto, Talampaya, Marayes, Guayaguas, Quijadas, among others) constituted depocentres that worked from the Triassic to the Cretaceous, generating the accumulation of continental sedimentary sequences under arid to semiarid climatic conditions. These sedimentary basins extend from the foothills of the Andes in La Rioja and Sierra de Valle Fertit in San Juan towards the south up to the Serranias Occidentales de San Luis and underground up to the Beazley Basin (Figure 3). All of them exhibit a rift structure of the hemigrabene type, characterized by an asymmetrical geometry with an active margin on the west and a passive margin on the east. They constitute the outcome of the extensive processes undergone by the South American plate during the Mesozoic, which led to the final collapse of the Gondwana supercontinent and the opening of the Atlantic Ocean. The lshigualasto and Talampaya basins exhibit a series of geological formations that portray the sedimentation of the entire Triassic Period. This can be inferred from the fossiliferous content of these layers as well as from radimetric dating of the volcanic rocks. However, the absence of fossiliferous sediments of the Jurassic and Cretaceous is remarkable, which would document the continuity of the environmental and biological evolution of the Upper Mesozoic. Geological formations of the Jurassic and Crztaceous Periods are found in different and distant areas of Argentina, including La Rioja, San Juan, San Luis, Mendoza and Neuqukn, and a sequence of basins located in the northwest and south of Argentina. The sedimentary outcrops in Sierra de las Quijadas are part of a chain of geological units the detailed study of which has enabled to complement part of the geohistorical and paleobiological information of the Upper Mesozoic in Argentina, which extends over 120 million years (the entire Jurassic and Cretaceous Periods) Sierra de las Quqadas is part of the Serranias Occiderniales Range in the northwest of the Province of San Luis and southwest of San Juan, which extends in the NNW-SSE direction along over 300 km, in discontinuous outcrops. This range exhibits a several-hundred meters-long sequence of sedimentary rocks of the red bed type, which includes several geological units of continental origin. These are known as Quehrada del Barn Formation, Los Riscos Formation, El Jume Formation, L a Cantera Formation, El Toscal Formation, La C m Formation (which includes volcanic rocks) and Largarcito Formation (Figure 4). As a whole, these units form the exposed stratigraphic column of the Mesozoic in San Luis province. From the paleoenvironmental point of view, these units represent a wide range of continental environments, including landslide, alluvial-fluvial, aeolian and lake deposits.

The paleontological records of macro and microfossils, as well as the radimetric dating of the volcanic rocks, indicate that these units represent a time interval that includes the upper portion of the Triassic period, most of the Lower Cretaceous and perhaps part of The Jurassic.

Some of the geological units in the stratigraphic column of the Mesowic in the Province of San Luis deserve special attention. Such is the case of the El Jume Formation, which constitutes a unique, outstanding example due to its sedimentary paleoenvironment. The hundreds of meters of claystone and sandstone intercalated in the cliffs of Potrero de la Aguada, which extends over 4,000 hectares, represent a model of a mud column of huge dimensions, the largest ever recorded in fossilized environments. This paleolake presents cyclic intercalations of strata of aeolian origin. Cases such as this are virtually unknown in the specialized scientific literature. Another unit that deserves special attention is the Lagarcito Formation, which constitutes a 100-million-year-old freshwater lake paleoenvironment. Here, the physico-chemical conditions led to the formation of a paleontological deposit of exceptional characteristics, in which very delicate biological structures have been preserved, such as skulls and teeth of pterosaurs and vegetal imprints, among others. These fossil reservoirs are known as Konsew Lugersfute.

3.1.2 Paleontological description

Different types of fossils belonging to the following groups have been found in the area:

  • Vertebrates: two and three-dimensional fossilized bone remains, both isolated and partially or completely articulated. Isolated and associated fossil footprints.
  • Invertebrates: remains of millimetric arthropod shells, in the form of imprints, as well as traces of the activity of soft body invertebrates.
  • Flora: imprints of leaves and stems, and fragments of petrified trunks.

Footprints of different groups of vertebrates have been reported, which can only be identified by their size, shape and general characteristics, the larger ones probably corresponding to sauropod dinosaurs. Irregularly shaped footprints that may belong to ornithischia have been also found. Recently, small footprints with four and five toes have been reported, which, although not yet investigated in detail yet, could belong to nondinosauroid reptiles such as crocodiles.

La Cruz Formation

There is only one fossil record of this formation, consisting of isolated bone fragments from a pterosaur, referred to as Punianipterun globosus.

Lagarcito Formation

This is the unit with the geatest amount and variety of fossils. In a single deposit of the Sierra de las Quijadas, fossil remains of some of the largest flying reptiles in Argentina (pterosaurs) have been found in a remarkable state of preservation. Many articulated specimens and non-articulated remains of the pterosaur Plerodauvtro giñazui have been found. The skull characteristics of Pterodaustro giñazui are unique within its type, due to the presence of hundreds of thin flexible teeth that were used for straining food from the lake (Figure 5). It has been shown that the characteristics of the Pterodaustro teeth are exceptional and unique in the animal world. A great amount of complete and incomplete skeletons of fishes belonging to the Families Semionotidae (1Veosemionotus puntanus and N. cuyanos) and Pleurofolidae have been found (Figure 6). Among the invertebrates, bivalve arthropods belonging to Conchostraca (Cycicus) and to Ostracoda (Darwinula, among others) have been identified. The latter are of microscopic size but very useful for the determination of the environmental characteristics of the water bodies in which they lived. Fossil traces (left by organisms in the substrate) of the Treptichnus and Gulielmifes types have also been found. Among plant remains, imprints of delicate flower structures have been identified, which according to their age, belong to the angiosperm group (flowering plants), one of the most ancient and primitive known in the world.

The collection of pterosaur fossil remains recovered from the Lagarcito Formation is in the Laboratory of Fossil Processing of the Department of Geology of San Luis National University and undoubtedly constitutes the most important collection at world level for this pterosaur species. It was collected over three paleontological fieldworks performed thanks to an institutional cooperation agreement between San Luis National University and the North American Museum of Natural History of New York. Along 45 days of work, 200 m3 of rock were removed and almost 1.000 specimens of fossil remains were collected, most of them belonging to the above mentioned pterosaur species. Hundreds of bones of different size have been recovered, including pterosaur juveniles and remains of up to 4 meters of wingspread. All this material has permitted to perform studies of anatomical growth (ontogenics) of this species, which is not usual in the research of extinct species. The funds that permitted to carry out this collection campaign were obtained by the National Geographic Society and the McKenna foundation, the National Council for Scientific and Technical Investigation (CONICET) of Argentina, and the Secretary of Science and Technology of the San Luis National University.

Finally, this deposit is of great potential with regard to the possibilities of future findings, considering that the explored area constitutes only a very small portion of the fossiliferous outcroppings in the Sierra de las Quijadas National Park.

The Lower Cretaceous is an extremely important time period in the evolutionary history of living beings such as invertebrates, flower plants and insects, since it was during this period that diversification and the appearance of several groups of organisms, some of which have remained to the present, took place. Its rocks outcrop in very few sedimentary basins in South America and the rest of the world. Therefore, the fossiliferous content of the Lagarcito Formation represents a unique opportunity for knowing the flora and fauna of central Argentina during the Lower Cretaceous. Thus, cunent research on these deposits is considered of great relevance and constitutes an important contribution for paleoenvironmental, evolutionary and philogenetic studies carried on in other parts of the world.

3.2 Biological Diversity


The Sierra de las Quijadas National Park undoubtedly constitutes a "sanctuary" of the flora and fauna of the Province of San Luis and of the west-central part of Argentina, since its environment constitutes a transition strip or "ecotone" between the biogeographical provinces of Chaco and Monte. Furthermore, this National Park is the only protected area for the preservation of this type of ecosystem, The Chaco province is characterized by thick profuse forests with outstanding high size species such as Prosopis flexuosa and Aspidoderma quebrucho-blanco and the Monte province exhibits sparse and low xerophilous forests, with predominance of the Larrea genus, especially cunefilia.

The land is never completely covered and the large saline areas include halophytic vegetation with jume as the predominant species. In the shrub areas (shrub steppe) there are many formations typical of the Monte biogeographical province, such as communities of zampa (Atriplex lampu), jarilla (Larrea divaricata, Larrea cunei$oZia) and high shrublands of lata (Mimo~ganthucsa rmatiis). The arboreal stratum includes open forests of quebracho blanco (Aspidospermu quehracho-blanco) along with black or sweet algarrobo (Frosopis flexuosa), albaricoque (Ximenu americana), retamo (Bulnesia retama), brea (Cercidium precoxj and chaiiar (Geofloea decorticunsj. Shrub species include atamisque (Capparis emarginataj, pichana (Cassia uphyla), matorral (Prosopis sericantha), retortufio (Prosopis strombuli$eraj, cardoncito (Cereus aethiops) and penca {Opunfia sulphureaj. On the western slope of the hills, a semixerophilous forest extends on the canyons, with tala (Celtzs fala), white algarrobo (Prosopis chiienszs), romerillo (Aloysia gratissima) and cabello de angel (Clematis denticulata). On the edges of Poirero de La Aguada, erosion prevents rooting of the plants. On the marginal areas it is possible to find isolated specimens of verdolaga (Halophfln arneghinozi and an amaranth variety with semicircular cushion, Gomphrem colosacana vur. andersonii, only identified in this area. Chica (Ramironoa girolae) grows on the natural balconies of Potrero de la Aguada, while on the southern edge of the Potrero the vegetation is of the sierra type (sierra-type thicket) with disperse sweet algarrobo (Prosopis flexuosa) and quebracho (Aspidosperma quebracho blanco). Shrub strata of jarilta and garabato are predominant here. Cactaceae are particularly abundant in this region, among them, huevo del indio (Tepkrocactus articulntus var. articuIahcs) and puqui con bigotes (Tephrocactus urticulafus var. papirocanthw;i. Chaguar del llano (Bromelia uribianum) forms large patches on the sandy soil and two types of clavel del aire (Tillandsia aizoides and Tillandsia xiphioides) grow as epiphytes. In the past, this area was covered by the Guanacache lagoon system, formed by the overflow of River Desaguadero, where rush (Scirpus calfornicus) used to grow. The lakes have drained leaving only salty barren extensions, covered with rests of totora (Typha sp.) that grow during unfavorable periods, and large dry extensions with isolated plants of vidriera (Allenrolfea vagjnala).

Surrounding this area, there is a strip of land with new shoots of tamarisco (Tamarix gulltcu), an exotic wildened species. The vascular flora is formed by 206 specific and infraspecific taxons, distributed into 45 families, Ptedirophytes and Pinophytes resent only 3 taxons, while liliopsida, with 45 taxons, and Magnoliopsidae, with 158 taxons, are the main families. The best-represented families are Poaceae, Asteraceae, Fabaceae and Soianaceae. The regional endemisms detected are 62 taxons representing 30% of the total, along with 3 species new for science, Sclerophylux dfulvioi, A~iplaquizadensis and Senecio hualfaranensis. Thus, the park can be considered an important genetic reservoir of the west-central flora of Argentina.

3.2.2 Fauna

The fauna of sierra de las Quijadas corresponds to the Neotropical zoogeographical region, Andean-Palagonian subregion, Central Domain. It is mainly of the Brasilic type and Subtropical and Chaco filiation, selected under rigorous ecological conditions, but with a marked Patagonian influence.

In the protected area the fauna is varied, since it has become a refuge for many species that used to wander around a wide region of central-western Argentina:

Reptiles: the presence of 40 species in the National Park, three of which are in seriously endangered, has been reported.

Ampihibians: the area corresponds to the Chaco batrachfauna of the Monte or Temperate district. Of the 14 species identified, one is in CITES 11, one is vulnerable and one is endangered.

Birds: Some authors have reported approximately 140 species in the area, 80 of which belong to non-passeriforms and the remaining ones to passeriforms. However, 189 species have already been identified the National Park, two of which are endemic and ten are under some degree of endangerment.

Mammals: the Sierra de las Quiadas National Park belongs to the mastozoogeographical region of the Neotropical Region, Chilean Subregion, Andean Domain, SubAndean Province. Eighteen species have been reported, with approximately 47 species remaining to be confirmed. Among the confirmed species, 11 exhibit some degree of endangerment. The most highly endangered species, which are already protected by national and international laws and agreements, are Chlumydophoms truncatus (Appendix I in CITES, EN at international level), Chelomidis chilensis (Appendix II in CITES, VU at international level), Falco peregrinus (Appendix I in CITES), Gubernatriz cristata (EN at international level; Appendix I1 of CITES) and Harphyoliaetus coronatus (Appendix II in CITES, VU at international level).

3.3. Anthropology

The World Heritage resources of the Sierra de las Quijadas, National Parks are of great archaeological, prehistorically and ethnographic value and evidence a close relationship and regional integration with the Ischigualasto and Tamlampaya National Parks. This would permit to establish a cultural chain with similar anthropological patterns in the mentioned geographical area central region of Argentina known in the world. In this respect, the provinces of San Luis, San Juan and La Rioja have undertaken a Program of Regional Integration, signed by their governmental authorities on February 26, 2003. Finally, the recognition of Parque Sierra de las Quijadas as a natural property of outstanding value for humanity and its regional integration with the Talampaya and Ischigualasto Parks will increase knowledge and constitute an invaluable pedagogic and cultural tool, since these parks contain the geohistorical record of the Mesozoic.