Cosquer Cave, 30 years of research

The Cosquer cave is located in the municipality of Marseille, on the coast of the Calanques National Park, between the cities of Marseille in the northwest, Aubagne in the northeast and Cassis in the east. It grows in the limestone massif of Cap Morgiou, between Mount Puget (563 m) and the Monts de Marseilleveyre (432 m), at the point of the Pointe de la Voile.

Cape Morgiou forms a long rocky outcrop covered with a rare garrigue. Overlooking the sea on three sides and separating the creeks of Sormiou and Morgiou, this area of steep cliffs plunging into the sea is full of emergent or underwater cavities. The entrance to the cave is a narrow passage that opens at the foot of one of these steep cliffs 37 m deep. The cave is partly in the public maritime domain and develops under parcels belonging to the State which is the sole owner.

The discovery
In July 1991, Henri Cosquer discovered the first works without declaring them (Cosquer 1993). On 1 September 1991, three divers accompanied by a local instructor entered the access trap. Only the instructor will survive this tragic dive. He will be sentenced to three years in prison for manslaughter. The bodies of the victims were recovered on 2 September. On September 3, Henri Cosquer, constrained by these dramatic events, declared the cave that would bear his name. This triple fatal accident demonstrated the difficulties and risks associated with access to underground diving and the compelling need for the owner state to secure the site, which will be done as soon as the discovery is declared.

The archaeological part of the cave concerns only the still exonerated fraction of a vast cavity mostly invaded by the sea. This remains, consisting of two rooms, is the highest and most remote part of the original cave. It therefore does not reflect the topographical reality of the site frequented by prehistoric men. Indeed, during the last glaciation, the site was made up of a vast network of volumes in which prehistoric men could easily circulate. The current access is through a submerged gallery forming siphon whose entrance is 37 m deep. This rising underwater gallery leads into room 1 at sea level 0. During the last glaciation, this route, then open air, was the one used by prehistoric men.

An impassable upper network ensures, through a narrow siphon, the natural atmospheric pressure of the cave. The injection of air, propelled by the swell, is done by following this long corridor more or less narrow which establishes a junction with the top of the Grand Well located 30 m above the water level. Since 1995, this crossing has been partly adapted for technical purposes. The Great Well, with perfectly vertical walls, as well as the upper network were never frequented during prehistoric times and have no archaeological remains. The entire upper network remains inaccessible.
The cave having developed through a stratum joint in the Barrémian limestone layers, the general topography of the site follows the dip of the strata which is about 30% in a southeasterly direction.
- Room I is a large area of about 50 m by side. The sea covers more than half of the surface on the ground. The depth of the water varies, depending on the sinking of the soil, from a few centimetres to several metres. Only sectors 105, 107 and 115, invaded by collapsed blocks detached from the ceiling, have a passable ground but extremely chaotic. To the north
from Room I, two narrow passageways, the "Porthole" and the "Bison Gate", reach Room II.
- Room II has smaller dimensions: about 15 m wide and 48 m long. The ground is subhorizontal. The entire eastern part of Room II (area 205) is occupied by a large body of water corresponding to a vertical well rising more than 40 m above the sea and diving more than 20 m underwater. The upper part of the well was never used by prehistoric man. The underwater part was not studied.
To facilitate the study, these two rooms were divided into 20 work areas: 101 to 126 for room 1 and 201 to 205 for room 2.

During the last glaciation
A little before 32,500 BP cal, during the glaciation of the Würm which then rages and which already lasts for more than 82,000 years, a human group (Aurignacian or Gravettien ancient?), probably recently arrived in the Calanques and probably coming from the north of present-day Italy, discovers the existence of this cave and decides to enter it. During their visits, these men engrave on the walls, by the light of torches, more or less stylized animals, deer, horses, ibex, etc. Their small works are the first expressions left by humans in the cave. Unfortunately, as these are engravings, it is impossible for us to date them.
Some time later (it is difficult to quantify the duration that separates the two episodes), these same men or others, again enter the cavity and leave representations of black negative hands made with coal which, in turn, will be dated to 32,500 cal BP. We have observed that the charcoal pigment of some of these hands covers previously engraved animals, which allows us to establish a relative chronology: the engravings are older than the hands.
The men who made these representations in coal are part of a culture called Gravettien (eponymous site: La Gravette, in Bayac in the Dordogne) which covers a vast pan-European area stretching from the Cantabrian peninsula to Eastern Europe.
 

At this point, the climate is still colder and drier (the Würmian glaciation will continue for at least 14,000 years). The general level of the oceans (and the Mediterranean Sea) is 130 m lower than the current one. In the Calanques of Marseille, the lowering of the level means that the shoreline is about 10 km away from the current cliffs. Three biotopes stand out in this Mediterranean margin: a coastal biotope with its fisheries and hunting resources (fish, shells) as well as seals and penguins; a biotope of steppic plains (which corresponds to the part of the continental shelf released by the lowering of the sea level) where grass favorable to the large herbivores (horses, bison, aurochs, megaceras, red deer); finally a mountainous zone (Monts de Marseilleveyre and Puget, Cap Canaille, Riou islands) which is a suitable biotope for ibex and chamois in particular. The fauna of these three ecosystems with rich and perennial resources is the one depicted in the bestiary of the Cosquer cave, a cave that is distinguished above all by the representations of marine animals. Apart from animals, most of the drawings and engravings are made up of abstract signs, negative hands and digital traces.
Around the age of 26,500, the cold reached its peak during the Last Glacial Maximum. This extreme cold makes the sea level even lower and is 135 m below the current level. During this extremely difficult period for prehistoric men, we notice the decrease in the number of datable representations. This could indicate possible cold depopulation. These violent climatic events disrupt the existing Gravette culture and create a split into two distinct groups along an axis formed by the Rhône and the Massif des Alpes. The human groups located in the West are now turning towards a solutreman and then magdalenian evolution while the groups in the Southeast (Mediterranean, Central and Eastern Europe) will keep a cultural stability, moving towards an epigravettian evolution that will preserve, gradually making them evolve, some of the most characteristic technical elements of the Gravettian culture. From a geographical point of view, this culture extends from the west to the Rhône and from the east to the Dnieper. The Italics and Balkan peninsulas are at the heart of this geographical space. In Provence and more widely on the Italic peninsula, the Mediterranean Epigravettian replaces the local Gravetine culture.

Man has frequented the cave for thousands of years. The most recent date corresponding to his last passage is approximately 19,000 Cal BP.

From the end of the glaciation,
The climate is warming and the sea level is starting to rise. The entrance to the cave is submerged around 10,000 years ago. From that moment no man entered the cave, the entrance of the long gut being flooded. Gradually, the rising water level, the layer of mondmilch lining the walls disintegrated. Mondmilch deposited as white sediment on the gallery floor. It is this sediment that gets suspended in the water at the slightest wrong movement by totally obscuring the visibility.

Late 20th century
Thanks to the improved techniques of underground diving, man again enters the cave. The vast cavity is partly flooded, only a third of its volumes remains exonerated. It is thus by following in diving the 137 m long siphon that a diver discovered, without knowledge of prehistory and unconscious of the ground he was treading, animals drawn on the walls, negative hands and archaeological remains that littered the ground.

Since 1991
Research led by the Ministry of Culture has made it possible to build a corpus of works, to establish dates and to identify the visible anthropogenic remains. Currently, the work in the cave is intended to obtain a three-dimensional survey of the entire cavity. These surveys, which represent a considerable commitment, will allow to better understand the development of the cave in the massif of Cap Morgiou, to carry out studies on the anthropogenic remains still preserved and finally to have a better understanding of the particularities of the internal climate and its direct impact on the conditions of conservation. Bathymetric surveys conducted by the DRASM (Department of Underwater Archaeological Research) will allow to visualize by means of a numerical model the vast space, now engulfed, in which evolved the peoples of prehistory.
The Ministry of Culture will continue its work by setting up research teams for the interdisciplinary study of the cave.

The Ministry of Culture will continue its work by setting up research teams for the interdisciplinary study of the cave.

Following the declaration of discovery on September 3, 1991, an expertise operation was organized by the DRASM (Department of Underwater Archaeological Research) and conducted by Jean Courtin (National Centre for Scientific Research), from September 19 to 21, 1991, at the request of the Ministry of Culture (Architecture and Heritage Directorate). This operation authenticated the figures and, through charcoal sampling, established an initial date of 18,440 +/- 400 BP, or 23,421 – 21,251 BP cal.

The cave was classified as a Historical Monument by order of 2 September 1992. Surveys and studies were carried out in 1992 and 1994 under the scientific responsibility of Jean Courtin with the support of DRASM and his ship L'Archéonaute. The work accomplished and the results obtained during these two campaigns are remarkable and founders of the knowledge of the cave. A first chronology is then proposed in a work published by Le Seuil in 1993: "La grotte Cosquer, Peintures et gravures de la caverne engloutie" by Jean Clottes and Jean Courtin.

This first chronology reveals:
- an Aurignaco-Gravettian phase 1 from 27,500 – 26,500 to 29,000 - 24,000 BP: digital and negative hand plots.
- a hiatus between phases 1 and 2, initially of “at least 8,000 years”, reduced to 4,300 years, (between 19,700 and 24,000 BP). During this interval the «chaos» (collapse of large blocks of sector 107 and, simultaneously, the calcite layer which currently covers a large part of the ground of the cave is formed.
- a phase 2 solution located between 19,700 and 18,000 BP: drawing and engraving of all animal representations.

From 1995, a team formed by Luc Vanrell (IMMADRAS) was appointed by the Ministry’s services to implement a set of archaeological monitoring interventions and works (prospection-inventory of wall art, security, preservation, data collection and maintenance of the measuring devices placed in the cave), from 1995 to 2000 under the control of DRASSM (formerly DRASM, which became the Department of Underwater and Underwater Archaeological Research), then of the Regional Directorate of Cultural Affairs of Provence-Alpes-Côte d'Azur (DRAC-SRA PACA, Ministry of Culture), from 2001.
From 2001 to 2005, five planned archaeological research operations to continue collecting archaeological information on the site are organized under the scientific responsibility of Luc Vanrell.

From 2010 to 2015, five planned archaeological research operations are organized under the scientific responsibility of Luc Vanrell in collaboration with Michel Olive (DRAC PACA SRA). During these campaigns, the inventory of the works and the knowledge of the cave were enriched by many discoveries.
In 2010, following powerful climatic and seismic events and their visible impacts in the cave, risk monitoring visits and systematic damage measurements were implemented. At the same time, a study is being conducted at the initiative of the DRAC PACA in order to carry out a three-dimensional numerical survey of the entire cave. This work made it possible to implant on site patterns that constitute the backbone of all the surveys and to carry out a three-dimensional test survey of the Horses panel and the drapery of the «Jellyfish».
A collection campaign ¹⁴It is organized by the SRA. The laboratory tests, available in 2015, make it possible to better understand the human use of the cave and to show that this use of the site is almost uninterrupted during a period between 32,500 years Cal BP and 19,000 years Cal BP.

From 2017, the DRAC (Regional Conservation of Historical Monuments and Regional Service of Archaeology) conducts conservation operations and studies of the hydro-climatic context particular to the Cosquer cave in collaboration with the CEREGE (Centre de Recherches et d'Enseignement de Géosciences de l'Environnement) and the LRMH (Laboratoire de Recherche des Monuments Historiques).

Since 2017, several high-precision three-dimensional surveys have been organized to record a memory of the remains and to offer researchers the opportunity to discover them without having to move around the cave. These survey operations are long, tedious and depend on weather conditions so this work is not yet finalized. Eventually, they will also offer the general public the opportunity to discover the cave via digital models or anamorphoses (project of the Region in progress within the Mediterranean villa).

Several specificities make this cave unique among the ornate caves.
Its main singularity is due to its location on the Mediterranean coast, in the south-east of France. It is on the fringe of both the ornate caves of southwestern France, the Spanish Cantabrian coast and the Ligurian-Provençal context. The presence of marine animals in the corpus of representations is also an originality.

Another peculiarity of the Cosquer cave is the density of the traces left by men. It seems to sign an abundant attendance over a very long period (Gravettien ancien – Epigravettien ancien) that could be consistent with the quality of the place and the variety of its resources (three biotopes with perennial resources) This will allow hunters and gatherers to settle and thus increase regional crop stability.

The cave presents, in places not yet invaded by water, many traces of human activities:
- arrangements for concretions;
- traces of fixed or mobile lighting;
- fireplaces with many coals;
- some engravings on the ground;
- footprints of children’s hands;
- voluntary caving breaks (concretions - karstics such as stalagmites, stalactites, fistula, etc.);
- some flint tools.

The high number of graphic entities makes it possible to affirm that the Cosquer cave was one of the great sites of European parietal art, like Lascaux, Altamira or Chauvet. We only have a small part of the panels in Cosquer because most of the walls are now underwater, completely corroded and invaded by marine concretions. Since all the surfaces currently accessible (even with difficulty) in the outer part have been used and there are engravings, digital traces and drawings everywhere, it is legitimate to assume that the same was true in the areas that are submerged.

The Cosquer Cave bestiary is representative of animals that prehistoric man could observe and even hunt. These animals are among the three biotopes that characterize the site (marine coastline, grass plain and mountains). This explains the large number of species represented. Exceptional in parietal art, man drew marine animals.

The results ¹⁴C obtained from the samples taken in 2010 make it possible to better understand the human use of the cave and to reinterpret the previous dates. The distribution of dates confirms the long duration of visits to the site, at least 32,500 Cal BP to 19,000 Cal BP, a minimum duration of 13,500 years.

However, an atypical but coherent graphic set, which had been named by Jean Courtin together with the «Small engraved animals» (designation that we have kept by habit to designate this particular art) had been highlighted by 1992. It concerns several panels of animal engravings more or less realistic, incised very finely in the wall. Of homogeneous size, but significantly small in comparison with the rest of the corpus painted or engraved, this set stands out frankly from the rest, especially by the technique of realization, by the dimensions, by the way of representing the members and sometimes by the unrealism or distortion of the subject. Special attention was paid to highlighting, in two places, the overlapping of these engravings by the halo of the nearby black negative hands. This demonstrates the anteriority of the realization of «small animals» (without being able to date them) with negative black hands which are among the oldest dated.

The Cosquer cave is the only cavity to have an extremely difficult access that is reserved only for speakers, archaeologists or specialists, in possession of a solid training in underground diving and having a regular activity (to maintain operational capacity) and in compliance with professional regulations related to underwater interventions.

The process of following the siphon is complex and risky. The entrance is made in scuba diving under ceiling following a hose of which some parts are narrow.

The weather is a decisive factor on the interventions: a too strong wind, a too present swell can lead to cancel a mission long prepared.

In addition to the difficulties of access for people and equipment, we must keep in mind the isolation of the site and therefore the difficulty of intervention for the rescue. The movements in the cave must also be considered dangerous: the slightest accident, even a minor one, can lead to an extremely complex rescue chain. The presence of a corrosive marine environment and an atmosphere charged with more than 90% humidity can be disastrous for high-tech equipment. The great fragility of the archaeological site, the walls, the cavers and the remains still present on the ground, a particularly rugged ground, areas with a low ceiling that require to crouch or even crawl, require constant concentration and attention during all gestures, movements and movements.

The maximum number of persons attending the cave at the same time shall not exceed five persons per day for five hours. This rule has been defined both to protect the particular environment of the cavity and to preserve the physical capabilities of the responders and thereby their safety. Working in the Cosquer Cave requires excellent physical fitness because the personal commitment is very trying, even exhausting (weight loss of three kilos per day and per worker on average).

Before any mission, and depending on the type of work, the equipment taken (computer, camera, measuring devices, etc.) must be packed in waterproof and balanced containers for diving. This conditioning will have to be repeated for the exit because we forbid ourselves, for the good conservation of the cave and the devices, to leave anything in the cave.

The environmental regulations established by the Natural Park of Calanques must also be respected.

The most worrying threat is the acceleration of the rise in global ocean levels, linked to global warming. The gradual loss of what remains of this major site will certainly be the logical consequence of this phenomenon. At present, several works, visible in 1991, have almost completely disappeared or are in the process of disappearing. This degradation, which has been accelerating since 2011, is mainly due to the rise of the sea level in the cave. It is amplified by an internal phenomenon that induces a strong variation of the water level.

The marine pollution introduced into the cave by the waves is variable depending on the periods of the year: more discreet during the winter, this pollution can be strengthened in spring and become extremely present during the summer periods. Until now, it has not affected the works but continuous monitoring has made it possible to highlight the presence of microplastics that are deposited on the works and that are likely to be permanently embedded.

The consequences of the regional seismic activity and the geological evolution of the cave are visible in several places, concretions are cracked and draperies are fractured.

In addition to the documentation acquired since 1992, the photogrammetric cover (currently being developed) will make it possible to have a reference state of the decorated walls and then to carry out a dynamic monitoring of theselected witnesses in collaboration with the teams of the Historical Monuments Research Laboratory to evaluate microbiological and alteration evolution. Water and air sampling campaigns as well as the installation of motion controls are continuing and will make it possible to understand the evolution of alterations.

In addition to the current monitoring of the DRAC teams, an assessment of the condition of the walls of the cave and especially of the areas subject to marine fluctuations will allow a better analysis of the processes of alteration and loss of works. This state finding, carried out by conservation specialists and restaurateurs will be a basis for the elaboration of a safeguard plan that will necessarily take several years.

Faced with the irremediable disappearance of important heritage works, the Ministry of Culture has decided to carry out a three-dimensional survey of the cave as accurate as possible. A first trial was conducted in 2013. He confined himself to tests on certain areas of room I directly threatened by water and reflecting the diversity of the cave. These first results allowed the development of a more adapted method (taking into account the omnipresence of water, the extremely complex morphology of the supports, the absence of all communication networks, etc.). A campaign to survey the entire cavity (aerial and underwater parts) began in 2017.

A group of companies specialized in the field (FUGRO/IMMADRAS) have been entrusted with the realization of this survey which is broken down into several phases:
- a millimeter reading by laser scanner;
- a photogrammetric survey which, together with the laser scanner, will make it possible to achieve a sufficient precision for the study of works in the laboratory;
- an underwater laser survey and a bathymetric survey carried out in collaboration with DRASSM will supplement the data required for archaeological and conservatory studies.

An ornate cave poses complex problems both for its conservation and for its study. These two complementary approaches involve the intervention of a large number of specialists in scientific disciplines that must work in synergy: archaeology, geology, climatology, microbiology, entomology, specialities related to the conservation of heritage materials, etc.

Currently the state owns the Cosquer cave and its surrounding environment. He is in charge of the future of the cave and the actions that must be undertaken there. The Regional Cultural Affairs Directorate of Provence-Alpes-Côte d'Azur manages the site and ensures the consistency of the actions undertaken.