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Geological, Paleontological and Archaeological Provincial Reserve Pehuén co - Monte Hermoso

Date de soumission : 17/01/2014
Catégorie : Mixte
Soumis par :
National Commission of Argentina to UNESCO
Etat, province ou région :
Coronel de Marina L. Rosales and Monte Hermoso District - Province of Buenos Aires
Ref.: 5851
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Description

AREA I from 38° 59' 43'' S / 61° 39' 00'' W to 39° 00' 10'' S / 61° 34' 30'' W

AREA II from 39° 00' 13'' S / 61° 32' 30'' W to 38° 59' 23'' S / 61° 27' 30'' W

AREA III from 38° 59' 19'' S / 61° 20' 54'' W to 38° 59' 17'' S / 61° 21' 59'' W

The Provincial Natural Reserve Pehuén co - Monte Hermoso is placed in the districts of Coronel L. Rosales and Monte Hermoso, in the South of the Province of Buenos Aires. It covers an area of approximately 16,2 km2 along the beaches, with an East-West oriented axis, in a very special and well-preserved coastal-sea environment.

In this place, it is preserved, in a section carved by the marine ingression of the Holocene, a geological, paleontological and archeological record of exceptional characteristics. In an extension of about 25 km, different sedimentary formations, whose age decreases from West to East, give us detailed information about the history of life and changes in the landscape over the last 5 million years. Amazingly, although many geographical, climate and biological changes occurred during these years, the conditions enabling the preservation of traces - to a greater or a lesser degree - of the different actors coming and going of that changeable scenery were repeated.

In that limited area, where the oldest visible rocks are continental sediments of the Upper Tertiary, there is an almost unique record that evidences the transformations during the last times of the Cenozoic isolation of South America until the Holocene. For this reason, along some kilometers of beaches, which are enlightened with the rising and the setting of the sun of the Atlantic during summer, rocks evoke very different landscapes formed over time and have been inhabited by species living before and after the Great American Biotic Interchange (GABI). The history written in these strata ends with the last big change of the Quaternary, a process that produced the extinction of dozens of mammals of a South American and North American lineage, the subsequent rising of the sea level as wells as the exploration and the subsequent settlement of old hunter-gatherers who inhabited that place during the early and mid Holocene.

Evidence includes three paleontological sites and two archaeological sites within the limits of Provincial Natural Reserve Pehuén co - Monte Hermoso distributed over three different areas where it is formed. In Area I, the Monte Hermoso Formation and the "Playa del Barco" site; in Area II, the Palaeoichnological  Site of Pehuén co and in the Area III, the archaeological sites of Monte Hermoso 1 and "La Olla" (sectors 1, 2, 3 and 4), respectively.

AREA I: The Area I of the Provincial Natural Reserve, whose limits are the five-metreisobath to the South, the beach crests to the North, meridian 61º 34' 30'' W to the East and meridian 61º 39' W to the West, is the most western unit considered in this proposal, and it is placed in the "Coronel de Marina L. Rosales" District. In this area, outcrops of the Monte Hermoso Formation as well as a big part of the "Playa del Barco" site can be found.

Monte Hermoso Formation: These outcrops of 0.15 km2are located in the Western part of the Area I and they are part of a much more extensive site named "Farola Monte Hermoso", which is extended 5 kilometres to the West beyond the limits of the reserve. This formation is composed off granedsediments of a reddish-brown colour accumulated in different continental environments, mainly of a fluvial origin, which contain rests of vertebrates, especially Pliocene mammals of the autochthonous fauna which inhabited South America before the Great American Biotic Interchange. Remains of freshwater fish, amphibians, reptiles and birds can also be found. The mammal association of this area is highly important and characteristic of a certain evolutionary stage called South American Land Mammal Age (SALMA) Monthermosean. This place is precisely the type locality of this biostratigraphic unit. Even though the majority of the preserved fossil remains here are bones, medium traces that belonged to ground sloths, which are part of the autochthonous South American mammals, can also be found. The first discoveries of mammals of the Monte Hermoso Formation were carried out by Charles Darwin in October, 1932 in the Monte Hermosocliff (now “Farola Monte Hermoso”). These discoveries together with the fossil remains that he found in Punta Alta in September of the same year were powerful elements for the English naturalist ideas about evolution of life. Among these remains, bones of several rodents were found, including one of a cavy.  About this fossil, Eldredge (2009) point south: “With the Monte Hermoso fossil cavy, Darwin had direct evidence of the existence of an extinct species that had been replaced by a close relative still alive today. There can be no way of concluding with certainty that Darwin had by then become a ‘transmutationist’ but it is clear from his notes that he was actively contemplating the possibility as early as late 1832. Thus, I cannot help but think of Bahia Blanca as being as important to the development of Darwin’s thinking as his much more famous visit to the Galapagos Islands three years later! For this reason, the geological strata of Monte Hermoso, with their richly productive fossil remains, deserves to be inscribed on UNESCO’s List of World Heritage sites every bit as much as the Galapagos, which has already been given that important designation”. 

“Playa del Barco”: The site is made up of fine to coarse sediments that become visible on an area of around 0.32 km2, 75% of which are within Area I and they extend over the limits of the reserve. In these sediments, mostly of  fluvial origin, there are fossil bones representative of the extinct fauna of the Pleistocene that shows the existence of a community composed of autochthonous South American mammals such as groundsloths (Megatherium, Scelidotherium, Lestodon, Glossotherium and Mylodon), glyptodonts (Glyptodon, Doedicurus y  Panochthus) and the ungulates Macraucheniaand Toxodon, together with mastodons, horses, sabre-toothed tigers and deers, which belonged to the fauna that came from North America during the Great American Biotic Interchange. In some parts of the site, there are levels with mammal foot prints which have been assigned to mastodons, megatheriids and Macrauchenia. These rocks, due to their ichnological association, their lithology and their relationship with the underlying rocks correlate to the siltstones of the Paleoichnological Site of Pehuén co, which becomes visible to the East in Area II of the reserve.

AREA II: it is placed in "Coronel de Marina L. Rosales" District and it is limited by the five-metreisobath to the South, the beach crest to the North, meridian 61º 27' 30'' W to the East and meridian 61º 32' 30'' W to the West. Within the limits of this area, lies the Paleoichnological Site of Pehuén co.

Paleoichnological Site of Pehuén co 

1,500 m to the East of the town of Pehuén co, beds of clayey rocks have lain there for 12,000 years keeping secrets of a lost world. Those strata extend along the beach for more than 5 km and they cover an area of 0.5 km2. There, the footprints of birds and mammals which lived during the Late Pleistocene are kept. Until now, there is only one 14C dating which comes from organic material found in the medium levels of the sedimentary sequence that contains the tracks of the Pleistocene fauna. This dating showed an age of 12,000 ±110 years, which coincides with the chronological estimates based on the stratigraphic position and the faunal assemblage. However, this is an approximate age owing to the nature of the sample and its peculiarity. Rocks were formed in a moment of the history of the Earth when the climate was cold and dry, and the sea was not where it is today; it had gone back dozens of kilometres towards the South-East of its current position. The former Pehuén co was a great valley of an ancient river and, in its lowest parts, fresh water accumulated during periods of heavy rains that swept along the mud from the nearest ravines. . As a consequence, ponds were formed, that were inhabited by waterfowls, and where pumas, deer, guanacos, bears, horses and strange huge animals that are extent today (Megatherium, Macrauchenia, Stegomastodon) came to drink water.

The tracks of all these creatures were marked on the mud, which after drying and covering with layers of sand and new mud mantles, they were transformed slowly in a succession of semi-consolidated rocks. As time went by, these strata were covered with layers of soils. Later, the rising of the sea level made the coast get closer to its current position, and the erosion of waves and the tides laid bare rocks with their testimonies. Nowadays, the strata formed in those old lagoons are the "site of fossil footprints of Pehuén co", technically called Palaeoichnological Site of Pehuén co, which, since its discovery in 1986, has been studied by scientists of the Universidad Nacional del Sur  (Bahía Blanca)and the Universidad Nacional de La Plata) together with members of the Museo Municipal de Ciencias Naturales "Carlos Darwin" in Punta Alta. Thanks to all this research, it is known that a rich fauna of mammals and birds used to live in this place. Among these species, the most remarkable ones, due to its size and peculiar aspect, were the huge ground sloths - megatheriums - whose footprints of more than 90 cm long can be seen today printed on the rocks of the beach. Until now, 100 trackways, hundreds of isolated ichnites and trampling areas, have been registered, all of which belong to about 24 different species of mammals and birds. Among the present ichnogenerathere are Neomegatherichnumpehuencoensis Aramayo and Manera de Bianco, 1987, Mylodontidichnumrosalensis Aramayo andManera de Bianco, 1987, Eumacrauchenichnuspatachonicus Aramayo andManera de Bianco, 1987, Stegomastodonichnumaustralis Aramayo and Manera de Bianco, 1987, Pumaeichnumbiancoi Aramayo and Manera de Bianco, 1987, Bestiopeda ichsp Vyalov, 1965, Lamaichnumguanicoe Aramayo and Manera de Bianco, 1987, Lamaichnumtulipensis Aramayo and Manera de Bianco, 1987, Phoenicopterichnumpehuencoensis, Aramayo and Manera de Bianco, 1987, Gruipedaichsp, Paninand Avran 1962, among others.

Present studies have also revealed that the number of tracks, the quality of their conservation and the association of fauna make this site a unique one. In 2005, footprints were found, suggesting the presence of human beings on the banks of the temporary lagoons. Until now, two types of signs of human presence have been identified. One of them is formed by two isolated ichnites found on big blocks of clayey sediment which had been removed by the tide. On each of them, there is a human footprint; both belong to the left foot. The other evidence is a trackway of 13 consecutive footprints where right and left ichnites are alternated and correspond to the ones left by the same individual while walking. The attribution of this trace to human beings is based on the angle of the footprints, which is of 160º. Fingers cannot be observed in any of the ichnites. This situation might be the result of a type of footwear or the existence of a sub trace. This occurs when the thinnest pelitic level where the track was produced has been eroded, and only the load deformation on a lower layer can be observed. On the same layer, a trackway of megaterio sub parallel to human traces as well as ichnites of macrauchenia, of artiodactyls and flamingos can be observed. It strati-graphically belongs to the medium levels of the site. The human footprints indicate that grown-up individuals, in reduced groups, might have been on the banks of temporary lagoons, which were usually visited by big mammals. This scenery might have been compatible with hunting events in which a few hunters, usually men, went over places where chances of finding preys were higher. These human marks are temporally related to the oldest evidences of the first settlers of South America. The archaeological traces of the human presence of around 12,000 years old are scarce and weak not only in this region but also throughout America.

This unit tells us, only through footprints, of a paleo community made of a great diversity of species of mammals and birds characteristic of the final Pleistocene that, within a few thousand years, were decimated. Many of these animals became extinct; others do not live in this region any longer, but the testimony of their presence was in the mud that later became rocks. The amount and type of these tracks as well as all the associated information derived from them make this a unique site worldwide.

AREA III: Area III of the Provincial Natural Reserve limits to the South with a 5-metre isobaths, the base of the frontal sand dune to the North, meridian  61º 20’ 54” W to the East and meridian  61º 21’ 59” W to the West. This is the most eastern unit considered in this proposal and it is placed in Monte Hermoso District including the archaeological sites of Monte Hermoso 1 and La Olla (sectors 1, 2, 3 and 4). The archaeological sites of Monte Hermoso 1 (MH1) and La Olla (sectors 1-2-3-4) are placed in the Atlantic coast 6km away from Monte Hermoso seaside resort. They extend 1300 m along the beach; they are stratified deposits with alternated layers of clay and sand formed in shallow water bodies, with more or less marine influence. In the past time, they were part of the border of a complex wetland connected to an estuary and coastal lagoons.

20 radiocarbon datings from samples of wood, of sea lion and guanaco bones and Ruppiasp seeds (a plant that grew in the lagoon) were obtained. The results of these datings show that between 7,900 and 6,600 before the present time, regional hunter-gatherers repeatedly inhabited that varied landscape, which became an exceptional complex of places simultaneously used for different every day activities.

The detailed description of the archaeological evidence of both sites will enable a better comprehension of the relevance and exceptional nature of both places:

Monte Hermoso 1: It has an area of around 88,000 m2 and the rock outcrops extend uninterruptedly over 1100 m along the intertidal zone of the beach. This area is mainly defined by the presence of thousands of children, teenagers, men and women’s footprints. Human remains, which are among the oldest of the Pampas, as well as scarce faunal remains and some wooden and stone tools on the same level as the tracks have also been found.

In this area, the footprints are grouped in two sectors: East and West.

Eastern Sector

438m2 have been systematically analysed and 472 human footprints, 35 bird and 2 artiodactyl tracks have been found. On the basis of statistical analysis, it has been informed that the tracks were produced by children, young people or women wandering along the beach near their residential camp who might have been collecting plants, bird eggs and fishes, around the lagoon.

Western Sector

A whole area of 353 m2 was analysed where human and bird ichnites, bone remains of sea lions, guanacos, black drumes, seashells and rhea eggshells as well as wooden and stone tools, were scarcely found. The footprints belonged to adults walking with a predominant direction SE-NW. This evidence suggests that there was an area out of the camp where people walked along a pathway. Redeposit human remains (skull fragments and parts of appendicular skeleton) were also found on the surface, dated back to 6,606 years and 7,886 years. The analysis of stable isotopes (δ13C media= -13,4%) about human remains shows significantly enriched values, which proves that the basis of their diet was seafood. These findings had great importance because they represent one of the few human remains of the early-mid Holocene in the coastal area of Argentina.

La Olla (1-2-3-4)

The sectors 1,2,3,4 of La Olla are small outcrops discontinuously distributed along 150 m, along an area of around 3000 m2. They are usually covered by sand. They were exposed only five times in the last 20 years but never simultaneously. The archaeological record of each of the sectors is similar and consists of abundant faunal remains and wooden, stone and bone tools.

Two species of sea lions (Arctocephalusaustralis y Otariabyronia), guanaco (Lama guanicoe), deer (Ozotocerosbezoarticus), rhea (Rhea americana) and fish were identified. These two species of sea lions are the most abundant ones. Some of the elements show cut marks and signs of thermal alteration, while others were used to make informal bone tools. Vegetables were also processed especially as raw material to make artefacts. The wooden artefacts are varied: there are wooden points which have been straightened and hardened with fire, a rock axe with a wooden handle. The most surprising artefact is an elongated wooden spatula, decorated on both sides with zig-zag incisions and red paint. It is not possible to know how it was used; due to the type and decor of the instrument, it was probably linked to a ritual activity. The stone artefacts are few, the used rocks are found within a radius of 20 km. There are mainly marginal or unifacial retouched artefacts, to which, with a low work effort, a certain shape was given.

The five areas (MH1 and LO (1-2-3-4) have a unique character because they provide exceptional data for the knowledge of history of the hunters-gatherers in the Pampas and South America. In the first place, the conservation of hundreds of footsteps of children and adults as well as tracks of birds and mammals were printed on the margins of an old water body and are an exceptional record in the continent. Secondly, the remarkable preservation of the wooden artefacts includes the oldest decorated element in the region with this raw material, the only handled tool and plenty of wooden points. These remains are absolutely extraordinary. Finally, it can be observed in these areas a clear sample of the beginnings of the exploitation of marine resources, when there was a rise in the sea-level as a consequence of the warmer conditions that characterized the mid Holocene. This becomes evident in the processing of sea lions and the isotopic information about human bones that shows the importance of these types of resources in their diet. The first evidence of the inclusion of the coastal marine in the seasonal routes of circulation within the area was preserved on the coast of Monte Hermoso. Therefore, a nomadic circuit between the coast and the interior was established; this probably lasted during the whole Holocene.

Justification de la Valeur Universelle Exceptionelle

Criterion (iii): The areas of Monte Hermoso 1 and La Olla (sectors 1,2,3,4) present exceptional evidence of the cultural tradition of the hunters-gatherers of the Early- Mid Holocene in the Pampas. They are characterized by the presence of fossil human ichnitesunique for this environment and chronology, not only for their quantity, but also for the quality of the record. Thousands of men, women, young people and children's footprints are a unique testimony of the cultural tradition of hunters-gatherers, of the organization and activities of these groups, as well as their relationship with their environment and its resources.

Criterion (v): The areas of Monte Hermoso 1 and La Olla (sectors 1, 2, 3,4) give us an exceptional example of a traditional settlement of hunters-gatherers in an estuary and peri coastal lagoon paleo-environment. Around these old bodies of water, places where different activities were carried out can be observed. In Monte Hermoso 1 East, ambulatory activities of children, young people and women strolling and wandering along the coast can be observed. On the other hand, in the Western area, there are pathways where adults were probably heading towards their camp. In La Olla, the process when the sea lions were captured on the coast and taken to that place to be deboned was finished. In these same places, different activities were done to make tools, especially using woods. All these points show the interaction that existed between the human being with marine environment at the beginnings of the mid Holocene. All these testimonies lie in an area where the natural and/or man-made processes developing nowadays are vulnerable to impacts, especially due to the erosion of seawater, wind and human activities on the coast.

Criterion (vi): The Natural Reserve of Pehuén co - Monte Hermoso is a milestone for the ideas and the schools of thought of the Natural and Anthropological Sciences developed since the 20thCentury. This place, where Charles Darwin made his findings in October, 1932, has fossils of mammals upon which he did the first direct connections among living and extinct species. Those inferences about the geological deposits became a worldwide reference in the generation and development of the evolutionary theories of the 19th Century, and, at the same time, this place constantly attracted geological, paleontological and archaeological sciences during the 20thCentury and until today. 

Criterion (viii): The Natural Reserve of Pehuén co-Monte Hermoso is an exceptional sample of geological and paleontological testimonies, which describe the interrelation of the geographic, climate, biological-evolutioary and human aspects through different moments from the Upper Tertiary to the Mid Holecene. Diverse geomorphological processes have allowed a natural geological cross section to be preserved. This geological cross section shows, with fossil traces, the history of life in the region, which is highly connected to the evolution of the Sauce Grande River. This river —the main river system of the south-west of the province of Buenos Aires—, runs through a wide depression with sediments of the Pliocene deposited before the Great American Biotic Interchange. In this valley, there are deposits which have been accumulated during their geological evolution between the Early Pleistocene and Holocene. These include levels with the autochthonous fauna of the Late Pleistocene and they also illustrate the extinction of the mega fauna and the subsequent strengthening of the occupation of that place during the Early and Mid Holocene by old hunters. The common characteristic of all these places is the presence of ichnites as evidence of a series of events that happened in the following order: 1) Existence of a plastic soft substratum which has been deformed due to the weight of the different organisms. 2) The coverage of these animal or human footprints by other sediments.  Nowadays, the marine erosion has been uncovering those old surfaces and, therefore, exposing a type of record that is usually rather ephemeral.

Criterion (ix): The paleontological and archaeological testimonies of the Natural Reserve of Pehuén co–Monte Hermoso are an example of the evolution of the continental ecosystems of the Upper Tertiary and the Pleistocene, turning into a seacoast environment towards the Mid Holecene. This is how, on a timeline, there is much evidence of extinct mammals before and after the Great American Biotic Interchange, subsequent communities of mixtures with current species and, finally, areas where fauna is part of the current environment.

Déclarations d’authenticité et/ou d’intégrité

Authenticity

The beginnings of the geological studies in this area date back to 1832 when Charles Darwin, on the Beagle, went through this point of a great paleontological importance. In 1887, Florentino Ameghino started exploring this place and, from that moment on, a lot of researchers visited the site with the idea of making new discoveries. This is why, today, it has become one of the most emblematic sites of the palaeontology of South American mammals.

Ameghino brothers' explorations in Farola Monte Hermoso (Rovereto, 1914) spread all over adjacent areas. This resulted in the discovery of the “Playa del Barco” Site, which still provides beautiful fossil exemplars of mammals of the Pleistocene. During the past years, layers with tracks of similar characteristics to the ones in the Paleoichnologic Site of Pehuén co have been discovered.

The Palaeoichnologic Site of Pehuén co has been known since October, 1986, when a storm exposed a platform of sedimentary rocks among the sand of the current beach. These sediments appear in the medium and high part of the beach making a series of wide stepped layers. These layers are worn away and the sand covers and uncovers them at random, according to the direction and energy of the prevailing winds. This peculiarity allows us to frequently observe new outcrops that, from time to time, show new discoveries whereas, other times, they are completely covered by sand.

Since the date of the discovery, different studies (Aramayo y Manera de Bianco, 1987, 1996; Manera de Bianco y Aramayo, 2004; Manera de Biancoet al., 2005; Bastianelliet al., 2012) have shown its wealth and its paleontological importance, which stands out due to the presence of plenty of footprints of big quaternary ground sloths of the Megatheirum kind.

The list of the species gathered in that environment probably is still incomplete. After every storm, something new can be discovered. This is how on 3rdFebruary, 2005 two blocks of limolite, which presented the same characteristics as the material of this kind in situ, were found. The blocks were 200 metres away from each other lying in the medium and high part of the beach. Each of them presented a human footprint; in both cases, the left foot. In spite of not being together, this is evidence of the presence of the human being in this paleo-environment, and although this does not allow us to establish his position in the sedimentary succession or his relationship with the local fauna, it opens up new directions for future research. The discovery of a human trackway in the same layer is also of great importance since it contains traces of megaterios, of macrauchenia, of artiodactyla and of flamingos. (Maneraet al. 2005; Aramayo and Manera 2009, Bayón et al. 2011).The study of this site allowed us to infer the environmental conditions in which it was formed.

As a consequence of his researches in Farola Monte Hermoso, F. Ameghino proposed that in that area there were "proofs" to show the evolution of the different types of mammals, including human beings. In 1887, he informed that "...what makes the Site of Monte Hermoso important is the presence of the human being together with a peculiar fauna. This becomes evident due to some roughly flaked stones and bones, the existence of bonfires on different levels of the cliff, set in clayey layers, from which I have been able to take fragments to the Provincial Museum in the city of La Plata." (Ameghino 1887: 5/6).

Between 1906 and 1907, he presented the Tetraprothomoargentinus, an ancestor of the modern human being. The human remains found were a femur and an atlas; the former was collected by Carlos Ameghino, whereas the atlas belonged to the collection of the Museum of La Plata. Finally, in 1910, he published the discovery of the oldest industry: "The Industry of the Broken Stone", to which he assigned an age of the Upper Miocene. In the International Congress of Americanists, the cliffs of Monte Hermoso were visited by Aleš Hrdlička and Bailey Willis, who dismissed the ideas of Ameghino. There was a considerable controversy and the place was visited several times to clarify different aspects such as the stratigraphic or the technological. In 1922 and 1924, Moisés Kantor denied the human manufacture of the lithic fragments of Monte Hermoso and revised the chronology of the stratified sands.

In 1924, a mission integrated by Francisco Aparicio, José Imbelloni and Joaquín Frenguelli went over the coasts of the South Atlantic and, among the visited places, was "La Farola". They proposed a "final explanation" about the polemic discoveries assigned them a recent age and a stratigraphic position connected to the recent sand dune. The revision of the discoveries of the Tetraprothomoargentinus was carried out in 1942 by A. Bordas, who attributed the remains of the human ancestor to a procyonidae. In 1947, Vignati considered the artefacts were the dismissed materials of a workshop and suggested that the layer of stones containing archaeological materials would belong to deposits formed within an alluvial channel. From this moment on, the site was not checked from an archaeological perspective until the 1980s (Bayón y Zavala 1997). However, the topic of the relationship between the settlements of the coast and those in the interior continued being rather controversial. Daino (1979), Politis (1984) and Bonomo (2005) synthesize the different views. 

Paleontological Studies Performed

Paleontological studies of the deposits of the current reserve began with Darwin in 1832 (Darwin, 1839, 1845, Eldredge 2009 a and b, Marshall et al, 1983) in  Monte Hermoso cliff. There thcrop out the Monte Hermoso Formation sediments that are the same  that are present in the West sector of the Area I of the reserve. In the 20thCentury, papers published by Florentino Ameghino since 1908 are highlighted. These papers were continued by, among others, Frenguelli and Kragllievich and they still continue. Since 1987, they have been spreading over Area II with the investigations carried out, among others, by Aramayo, Manera de Bianco and colleagues. From the geological perspective, it is important to mention those studies carried out by Zavala (1993), Zavala and Navarro (1993), Zavala and Quattrocchio (2001) and Schillizziet al. (1992) and also the observations and studies carried out during the actions for the project “Save a unique collection of prehistoric footprints - " (Rolex Awards 2004). In the particular case of the Area II, it is important to mention that it has been included among the Places of Geological Interest of the Republic of Argentina by the SEGEMAR (Argentinian Mining Geological Service) (2008).

Archaeological studies performed

The first archaeological evidence found on Monte Hermoso beach belongs to sector 1 from La Olla site. In December, 1983, Mr. Vicente Di Martino, Director of the local Museum, observed many marine mammals bones and some lithic tools in lake sediments which appeared on the beach. Archaeologist Luis Meo Guzmán - by then Director of Mulazzi Museum, Tres Arroyos City— started a rescue job; after that, the site remained completely covered for 10 years. In 1990, the site Monte Hermoso 1 was discovered; on that occasion, Mr. Rodolfo González, a geology student, noticed the presence of human steps on different exposed paleo-surfaces. From that year on, Dr. Gustavo Politis and archaeologist Cristina Bayón led systematic works and were in charge of successive fieldworks, which provided the information currently available.

In 1993, la Olla 1 site was again exposed for a few days; and, in 1995, La Olla 2 site was discovered. Finally, in 2008, there was an exceptional sand movement, which made possible to work in La Olla — sectors 3 and 4— for several weeks. Over the last year, the site has been exposed three times for short periods, which increased the erosion in the area. Every site in La Olla is usually covered by a thick layer of sand, and they stretch along the lowest tide line. These outcrops can be observed only when the following factors are combined: there shall be a displacement of the sand covering them, and the height of the tides and northern winds must all favour the site exposure. This rarely occurs, and it leaves the outcrop exposed only for a few days; under these conditions, the deposits can be unearthed during low tides for two or three hours.

Monte Hermoso 1 site, it situated in the intertidal zone of the beach, but closest to high tide zone; topographically, it is located three meters above La Olla zone. The works undertaken have included the delimitation of the site, identification of zones, as well as the study of footprints. Two zones were recognized; the first one is formed almost exclusively by footprints, whereas the second, besides the footprints, contained lithic and wooden tools, as well as some bone remains. 438 m2 were mapped in the eastern zone, and 353 m2 in the western zone. 1-meter grids (on each side) were planted, inside which footprints were mapped. Measurements to locate each footprint were taken considering a point at the base of the third finger.

The following is the data reported for each footprint: a) laterality, b) length from the extreme of the first finger to its heel; c) two widths, one at the height of the distal extreme of the metatarsus, and the other at the height of the heel; d) orientation; and e) distance among footprints (in the case of trackways) taking into account the same point for its location in the plan. In the western zone, archaeological remains were recovered, especially sea lions bones, lithic artefacts and snails. 20 radiocarbon dates (appendix 2) on samples of wood, bones of sea lion bones and guanacos and seeds of Ruppiasp (a plant which used to live on lagoon shores). It was established that both sites date back to 7,900-6,600 years.

The paleo-environmental reconstruction was based upon geological, palynological and ostracoda information, and it was performed by Drs. D. Martínez, S. Grill, C. Zavala; A. Blasi, C. Bayón and G. Politis led the research on archaeological evidence. Studies indicate that, seven thousand years ago, there was a body of water with seasonal variations in size, which was temporarily a coastal marsh or a lagoon among the sand dunes next to the sea. The vegetation was that of typical wet inter dunes, with a slight marine influence. On the banks of this old body of water, lie the 5 sites which form the area. 

The archaeological sites of Monte Hermoso 1 and La Olla 1, 2, 3 and 4, both have unique characteristics since they contributed with exceptional data to the understanding of the history of hunter-gatherers from the Pampas. Firstly, it presents hundreds of footprints from children and adults, as well as birds and mammals, all of which have remained printed in the banks of the old lagoon. Different aspects of the traces helped understand how people made use of the landscape in their daily lives. The second one shows the beginning of the exploitation of coastal resources, at the moment the sea water level increased due to warm conditions in the mid-Holocene. This can be clearly seen in the analysis of sea lions and in the isotopic information about human bones. In the third place, it possesses an outstanding preservation of wooden handcraft, including the most ancient decorated instrument done over such raw material, as well as a hafted axe; both objects are considered to be absolutely exceptional. 

Integrity

The Natural Reserve Pehuén co-Monte Hermoso is a true testimony to different moments from the late Tertiary to Early/Mid Holocene, and it is characterized by units of continuous records - geological, paleontological and archaeological -, which indicate and prove the existence of a sequence of evolution and development - 5,000,000 and 6,900 years ago.

On Area I, crops out the Monte Hermoso Formation (Pliocene), which holds remains of typical elements of the autochthonous South American fauna (bones and some footprints), as well as layers of the Pleistocene, with bones and footprints of a mammal community combining the autochthonous fauna of South America with  mammals species from North America.

On Area II, innumerable footprints of birds and mammals depict a fauna typical of the end of the Pleistocene, when big mammals, such as megatherians, big camelids, deer, proboscidea and bears (all of them extinct) lived together with guanacos, foxes and pumas. This scenario full of footprints of great animal diversity is completed with the human footprints in the ichnite site of Pehuén co, which evidence human presence in the area at the end of the ice age. 

Area III: it contains hundreds of footprints - around 7,800 years old - of children, adolescents, men and women associated with footprints from native regional animals along the beaches of an old lagoon. Many of these animals were already present in the area as shown in the near ichnite site of area II.  

Comparaison avec d’autres biens similaires

The Palaeoichnological site of Pehuén co is characterized by the abundance and quality of footprints from extinct mammals and birds; it is undeniable that, among them, the ones corresponding to the walk of giant ground sloths (Xenarthra Tardigrada) are conspicuous and numerous.

The only footprints from ground sloths found in North America are those from the Nevada State Prison, near Carson City. They were discovered during stone quarry works. In 1889, Addison Coffin made a drawing of the footprint distribution, including those of ground sloths, mammoth footprints (extinct elephants), horses, foxes and other carnivorous mammals, such as moose, deer, birds, etc. There are 16 references of Coffin's sketch belonging to the trackways  found. Footprints were printed over sandstone of Pleistocene age. Marché II (1986) estimates that these footprints are similar in age to Rancho La Brea - Los Angeles, USA, since their animal integration bears a great resemblance.

Fossils from Rancho La Brea date back to 33,000-12,000 years. The construction of the prison covered every footprint in situ; only a few original fragments remain unharmed at Keck Earth Science and Mineral Engineering Museum, University of Nevada; and a copy of the four footprints described by Stock (1925) are still preserved at the George Page Museum, in Rancho La Brea, Los Angeles, USA (McDonald, 2007).

 Such association of footprints reflects the faunistic composition from North America after the Great American Biotic Interchange at the end of Pleistocene, with the integration of living and extinct species. Although the latter aspect described coincided with the Palaeoichnological site of Pehuén co, they are both different due to their location - one in North America and the other in South America -, where mammal communities were differently composed at the end of the Pleistocene (e.g.  Macrauchenia is a species exclusively found in South America).

In Argentina, another ichnite site representing an association of mammals and birds can be seen on the Atlantic coast of Río Negro Province, with beaches full of abrasion platforms and big blocks fallen off the coastal cliffs. The ichnites represent an earlier stage of faunistic association —around 4 million years old— formed only by native South American fauna, including ground sloths, South American ungulates, carnivorous marsupials and large carnivorous birds; this stage arose before the arrival of immigrant mammals from North America to South America (Aramayo, 2007).

Other well-known footprints of Xenarthra Tardigradaare:

1)      5 footprints in situ from Miocene-Pliocenefrom Quebrada del Yeso, La Rioja province.

2)      Trackway, 5 footprints, Pliocene, Farola Monte Hermoso.

3)      Trackway - 29 ichnites, early Pliocene, Estancia San José, Patagones district, Buenos Aires province.

In the Pehuénco Palaeoichnological site, 28 trackways of xenarthra tardigrada had been registered until 1996, many of which have been destroyed by passage of vehicles or marine erosion. The impressions taken from 2004 to 2006 revealed the following results:

XENARTHRA: 194 footprints [21 trackways (193 footprints) + 1 isolated footprint].

GLYPTODONTIDAE: 1 isolated footprint

TARDIGRADA: 21 trackways (193 footprints) (Ichnospecies Neomegatherichnumpehuencoensis Aramayo and Manera de Bianco, 1987; Mylodontidichnumrosalensis Aramayo and Manera de Bianco, 1987)

UNGULATES:  175 footprints [22 trackways (173 footprints) + 2 isolated footprints].

LITOPTERNA (Macraucheniapatachonica): 47 footprints [7 tracways (45 footprints) (Ichnospecies Eumacrauchenichnuspatachonicus Aramayo and Manera de Bianco, 1987)

PERISSODACTYLA (Equidae): 1 trackway (2 footprints): 5E2-R01. (Ichnogenus Hippipeda Vialov, 1966).

ARTIODACTYLA (Cervidae-Camelidae): 14 trackways (126 footprints) (Ichnogenus Pecoripeda Vialov 1961 and ichnospecies Lamaichnumguanicoe Aramayo and Manera de Bianco, 1987, Lamaichnumtulipensis Aramayo and Manera de Bianco, 1987)

CARNIVOROUS: 29 footprints (4 trackways).

URSIDAE (Arctodus (Arctotherium) sp.): 2 trackways (5 footprints): 6F1-R01. (Ichnogenus Bestiopeda Vialov, 1965).

CANIDAE: 2 trackways (24 footprints): 6F4-R01 (1 trackways: 20 footprints); 6Ag2-R01 (1 trackway: 4 footprints).

BIRDS: 198 footprints [11 trackways (114 footprints) + 3 tracks (77 footprints) + 7 isolated footprints] (Ichnogena Gruipeda Panin and Avram 1962, Avipeda Vialov 1983, and ichnospecies Phoenicopterichnumpehuencoensis, Aramayo and Manera de Bianco, 1987)

This review shows the importance of Pehuén co site.

Open-air sites with human or Homininae footprints are very rare worldwide. If we take a tour around the above-mentioned sites, we can observe that the archaeological of Monte Hermoso1-La Olla has unique and exceptional characteristics. In order to show the importance of Monte Hermoso1-La Olla sites, we will briefly compare it with other sites of human ichnites.

The first group is composed of those cases related to pre-human forms or old Homo species. In the first group, the most famous site may be Laetoli in Tanzania, which M. Leakey and his team have been working on since 1970. It includes the trackways of two individuals along 27 meters - in total, 70 footprints impressed on volcanic ash. The footprints date back to 3,600,000 years, and they belong to Autralopithecusafarensis, a hominin fossil.

This finding was crucial in the history of paleoanthropology as it provided an insight into the beginning of biped locomotion; it also helped us learn that this type of locomotion had appeared millions of years before humans. 

In Kenya, there are two different sites with footprints of old Homo, Ileret-FWJJ14E site —1,500,000 years old. There are footprints on the different levels of this place; the upper level contains three human trackways: one with seven footprints, whereas the other two have to footprints each; the lower level contains a trackway with two impressions and 1 isolated footprint. The ichnites were attributed to Homo ergaster-Homo erectus species.

The second site is GAJI10, published in 1981; in this place, 7 footprints were recorded, all attributed to the above-mentioned species, which date back to 1,400,000 years.

Finally, in Europe, human footprints have been studied in two open air sites: in Roccamonfina, Italy, 3 trackways with 56 footprint sand hand impressions were discovered; the site known as Devil’s footsteps is 345,000 years old, and the footprints are attributed to Homo heidelbergensis. Finally, there is the isolated footprint found in the lower Paleolithic site of Terra Amata, France.  

All these sites have become of great scientific importance since they have contributed to the understanding and discussion of the characteristics of the evolution, as well as the consolidation of bipedalism; nevertheless, they cannot be compared with the case presented: they belong to very different times - end of Tertiary and mid Pleistocene - and they are different species.

The oldest sites containing footprints from anatomically modern humans have been found in South Africa in old fossil dunes. The oldest one is Nahoon, which possesses three consecutive footprints. The age of the site is controversial: 29,000 to 144,000 years old. The second site, Langebaan Lagoon, is 117,000 years old; as in the above-mentioned case, only three footprints could be found in a fossil dune. These sites cannot be compared with the case in question since both are very dissimilar in scale and chronology.

In Mauritania, El Azrag site has recently been studied. 118 human footprints were found together with impressions of large mammals. The formation process corresponds to the water logging produced 9,000 years ago during wet phases.

In Australia, in 2006, the Willandra Lake site (19,000-23,000 years old) became known. The site has eight trackways and 124 footprints of adults, adolescents and children, as well as kangaroo trackways. In England, Severn Estuary, Formby Point can be found; in South Wales, Mersey and Kenfig estuaries. All of them belong to the Mesolithic and Neolithic.  

All together, the sites around the world where Homo sapiens sapiens footprints have been found provided relevant information; however, if we compare them with the case in question, it can be observed that the size of the site of Buenos Aires coast is considerably bigger, which highlights its exceptional characteristics.

In America, there are only three open air sites which have human footprints. In Chile, South America, a human footprint from the late Pleistocene was found on Monte Verde site. The ichnite was impressed on the clay boundary of an old bonfire. This is not an ichnological site per sei, and it cannot be compared with the case in question.

The layer with footprints found in Toluquilla, Valsequillo, Mexico, presents impressions from human and animal footprints, which remained impressed over volcanic ash near a lake. The age of the ash layer is still highly questioned: the discrepancies range from 40,000 to 1,300,000 years old; therefore, new studies are needed in order to confirm the veracity of the site.

Finally, in Acahualinca, Nicaragua, footprints have been found on a layer of volcanic ash surrounding Lake Managua. The impressions belong to 15 or 16 people walking in a parallel way; they have been recently confirmed to be 2,100 years old. If we compared this site with the coastal sites of Monte Hermoso, we can clearly see that the latter is by far more relevant due to both its abundance and chronology.