ABSTRACT

The Sete Cidades National Park is a magnificent natural monument made of outcrops of Devonian strata of the Parnaiba sedimentary basin. This park is located in the northeastern part of the state of Piauí, almost 200 km far from Teresina, the state capital. It is reached through the BR-216 highway.
This park is named after seven different rock outcrops, each one considered a “city”. The ruinform topography mimics shapes from persons, animals and things, which take several pertinent names, as Dom Pedro I’s head (former Brazilian emperor), indian’s head, camel, tortoise, library, etc.
Apart from the  geological attractions the Sete Cidades Park is internationally known for its rupestrian inscriptions. This inscriptions were dated through the C¹⁴ radiometric method presumably from 6000 years ago and are interpreted to show  different situations, like hunting, as well as  religious concepts.
Sete Cidades is in the proximal portion of a delta lobe, so it presents features of fluvial and deltaic sedimentation. Medium-sand is the dominant grain-size in the area but gravel conglomerate and silt are also found. Several different sedimentary structures can be recognized in the rock outcrops. Trough cross-bedding, sigmoidal bedding, climbing ripples and  plane-parallel stratification, most of them disturbed by water escape structures are the main sedimentary features. The tower-like features are separated by steep vertical walls which clearly depict rain-water and wind carving controlled by jointing planes.
The park is presently run by IBAMA (Instituto Brasileiro de Meio-ambiente e Recursos Naturais Renováveis) which takes care of the conservation policy, signalization and guiding throughout the park. An hotel with lecturing facilities is open  to tourists the year round.

    The Sete Cidades National Park, located in the Piauí State (Figure  1), Brazil, is an impressive collection of natural monuments, made of outcrops of Late Devonian rocks (Fammenian). Rock outcrops  can be assembled together into seven groups, forming seven “cities”. The cities are in the southern end of the so-called Serra Negra (Figure  2).
    The climate is pleasant with a year average of 26^o C, and the seasonal rainy time in the late Spring going to late Fall favors the preservation of sedimentary features. The scarcity of vegetation (cerrado) helps the  depiction of internal structures and vertical successions that allows the interpretation of   fluvial and deltaic environments. Besides, a ruinform topography, carved by wind and pluvial water in sandstones, generates tower-like or domal features in  narrow gorges which suggests shapes of man, animals and objects. These forms have been stimulating the  imagination of several researchers: Ludwig Schwennhagen, an Austrian historian, described it as an ancient Phoenician city built some 3000 years ago; Erich von Däniken, a Swiss journalist, linked it to other monuments that suggested him  the visit of extraterrestrial civilizations in the past.
    In the steep walls of  the rock outcrops, covered by a siliceous patina, iron-oxide inscriptions made by primeval men can be seen. The age of this inscriptions is under dispute. Some researchers point out an age of 6000 years, based on C¹⁴ dating,  whereas Fortes (1996) interpreted them as post-Colombian in age, done probably in the nineteen century.  The inscriptions are interpreted as to figure out hunting procedures and religious themes.
    Several features found in Sete Cidades are common to the Vila Velha National Park, near Ponta Grossa, Paraná. Vila Velha is mostly fluidized by water escape phenomena. Convolute bedding is the most common structure. Liesegang rings and alveolar erosion are also common. Both occurrences seems to be the result of a delta construction under periglacial conditions.
    In this park, typical representatives of the local fauna and flora can be found. It can be named as a “cerrado”, with spots of open fields and ciliary forests. The fauna seems to be richer than the typical “cerrado” one, as a function of the presence of the “caatinga” and the latifoliate forest animals. For example, the veado-mateiro (Mazama americana), a kind of deer of the latifoliate forest, the iguana (Iguana iguana), also an amazonian species, and the mocó (Kerodon rupestris),  a rodent typical from the caatinga, are also found in Sete Cidades.
    Both geological and historical features enables the Sete Cidades National Park as a very interesting site for scientific research.
    In order to protect fauna and to recover degraded areas, 5600 ha of the park area are kept provisionally closed for visitors. Medeiros (1998) proposes an increase in the park area of  5100 ha  in the eastern side in order to include other geological monuments and to get a better integration of  flora and fauna.
    For more information about the geology and other features of the park, the readers are addressed to the book by Fortes (1996), which is plenty of illustrations and contains very good geological interpretations.

LOCATION

    The Sete Cidades National Park is located in the northeastern part of the Piauí State, belonging to the Piracuruca and Piripiri counties among the coordinates 04^o05’ to 04^o15’ S and 41^o30’ to 41^o45’W. The area is 6221 ha.
    It is reached  by the BR-343, Teresina-Parnaíba,  and the BR-222, an extension of the former highway to Fortaleza (Figure  1). Distance from Teresina, the Piaui’s capital, is 217 km and from Fortaleza, Ceará’s capital,  is 422 km. The easiest way to reach Sete Cidades Park is by plane to Teresina or Fortaleza  and after by car following the above mentioned highways. From Teresina, leaving the BR-343 one should enter the BR-222, going 12 km and then reaching the southern park gate by a secondary road, 12 km long. From Fortaleza, just keep in the BR-222, then reach the south park gate by the same secondary road.  The highway signalization is good  and the asphalt pavement was fair at the time of writing this chapter but it can attain  a bad condition after the heavy rain period in Summer.

Figure 1 - Location map of the Sete Cidades National Park and the possible ways to reach it.

Figure 2 - Location of “cities” in the park (numbers in squares). In gray, rock outcrops. In circles: 1) Warm fountain; 2) Cannons; 3) Suspended garden; 4) Arch of Triumph; 5) Library; 6) Belvedere; 7) Castle; 8) Lizards; 9)Inscriptions; 1)) Archette; 11) Inscriptions; 12) Indian’s cave; 13) Witch doctor’s cave; 14) Little church; 15) Gate; 16) Inscriptions (modified from Fortes, 1996).

GEOLOGICAL SETTING

    Geologically, it is located in the Parnaíba Sedimentary Basin, one of the largest Brazilian intracratonic basins, with 600,000 km² in area. This basin encloses a sedimentary pile belonging mainly to the Paleozoic, which starts in the Silurian.
    The Devonian rocks include the Pimenteira, Itaim and Cabeças formations.  According to the sand isolith map of the Cabeças Formation (Figure  3) (Della Fávera, 1990)  , this park is situated in the southern flank of a huge sandy sedimentary wedge coming from northeast, in the top of a section dated as Late Devonian (Famennian). According to Caputo (1985), there was a clear glacial event, recognized from diamictites and striated pavements, in this section and in  the overlying shaly Longá Formation. Therefore,  the park area is presumably covered by a sort of periglacial sediments.
    Vertical successions of facies in the area shows fluvial to deltaic sediments. Most successions are fining upwards, showing basal truncations, as the “library” (second city, figure 5). In this site, the basal portions are made up of coarse to medium sandstone with trough cross-bedding. According to Fortes (1996), the channels run in a southeast to northwest  direction, which is the dominant direction of transportation in the entire basin. In the “canhões” area (first city),  pebble conglomerate in festoons can be seen in the base of a fining upwards succession. Other structures include sigmoidal bedding and climbing ripples as wells as parallel laminated silt.

Figure 3 - Sand isolith map of the Cabeças Formation built after data from wells drilled for oil by Petrobras in the Parnaiba basin. Please note the position of the Sete Cidades National Park in the southern flank of a deltaic lobe in the northeastern portion of the basin (Della Fávera, 1990).

    A dominant feature is the water-escape structure. This kind of deformation affects mainly the sigmoidal lobes. Probably water escape occurred as a function of the large volumes of sediments deposited in short times, which is expected in periglacial areas, with catastrophic flooding.

HISTORY

    The first historical reference to the Sete Cidades site is the communication to the Brazilian Historical and Geographic Institute  made by the Counselor Tristão de Alencar Araripe, called “Petrified Cities and Rock Inscriptions in Brazil”,  in December ninth, 1886. The first description of Sete Cidades was made by the Piracuruca’s County Counsel in a communication to same Institute in 1897.
    In 1928, the Austrian Ludwig Schwennhagen visited Sete Cidades and described them as ruins of a Phoenician city, founded 3 thousand years ago. Erich von Däniken, in his famous book “Were the gods astronauts?”, described Sete Cidades as a  clue to the presence of  extraterrestrial intelligence in Earth, in the 60’s. Afterwards, in 1974,  the French Jacques de Mahieu assumed that the vikings had been settled in Sete Cidades.
    The Piauí researcher Reinaldo Coutinho (Coutinho, 1997) analyses the history of the discovery of Sete Cidades, as well as comments the several theories about the meaning of the cities of stone and its inscriptions.
    The park was officially created by the Federal Decree number 50.744 in June eight 1961.

DESCRIPTION OF THE “CITIES”

    Sete Cidades Park is divided into seven different rock outcrop assemblages, called “cidades”(“cities”)  (Figure  2).

First City

    The First City is characterized by  diagenetic features known as “canhões”(“cannons”), long tubes made of ferrified sandstones (Figure 7). This diagenetic product is also  known as “rolls” or Liesegang rings and consist of a chromatographic-like migration of iron hidroxides into a permeable and isotropic medium,  normally  fluidized sandstones.
    Notably, the cannons are inside fluvial deposits, characterized by a basal truncation and conglomerates with trough cross-bedding in a fining upwards vertical succession. Erosion accentuates these forms, which detach them from the enclosing rocks as cylindrical bodies  (foto 1).

Second City

    This city is characterized by very interesting features. The first feature,  revealing alveolar erosion,  is the so-called “Arch of Triumph”. Alveolar erosion is produced by caving of homogenous sandstone, giving rise to vulva-like features and  lately to natural archs.
    Walking from the “Arch of Triumph”,  inscriptions painted in vivid red colors, painted by a mixture of iron oxide, vegetable oil or animal blood,  can be seem,. They suggest impressions of hands and were painted probably by indians from the tribe Tabajara. According to C¹⁴ radiometric dating,  they would be 6000 years old.
    The “library” (Figure 5) is another interesting feature. It is made up of an erosion surface at the base of medium sandstone channel deposit with trough cross-bedding, which truncates  fine to medium sandstone and siltstone with plane-parallel bedding. This parallel bedding reminds books piled up in a library. In this site, well-sorted sandstone suggests an eolian reworking source to this delta-like sandstones. As seen from the belvedere (Figure 8),  the plane-parallel bedding is the distal portion of climbing ripples sets which in turn are the frontal extension of sigmoidal lobes (Della Fávera, 1984).

Third City

    In this city, several ruinform features can be seem, as the God’s Finger (Figure 9),  the head of Dom Pedro I, former Brazilian emperor,  and the Indian’s head. The Head of Dom Pedro I (Figure 10) is again the erosional contact of a fluvial-like feature, with medium sand over finer sediments.

Fourth City

    The most characteristics features of this city are the “Archette” (Figure 11),  where deformed sigmoidal bedding can be seen, and the Brazil’s map. Both are the result of alveolar erosion giving rise to caves and arching. Convolute bedding and strongly distorted bedding are very common in this site.

Fifth City

    This city is famous by its inscriptions. A drawing interpreted as defining the ritual of hunting and the final destination of man has been used as an icon representing the Sete Cidades National Park  and the neighboring counties. The current interpretation of this inscription is: “the indian follows the trail, chases the animal, kill it and offer it to the god Sun” (Figure  4).

Figure  4 - Inscription in the Fifth City:the indian follows the trail, chases the animal, kill it and offer it to the god sun

Figure 5 - Library. Second City. Truncated basal contact between a fluvial deposited over finer sediments with plane-parallel stratification.

Figure 6 - Tortoise shell.Sixth City. This form is famous by its polygonal features, covered by lichens.

Figure  7 - Cannon. First City. This feature is a product of diagenetic transformations by iron oxide. It is inside fluvial deposits with conglomeratic sandstone and trough cross-bedding.

Figure 8 - Climbing ripples in plane-parallel sets, which pass laterally to sigmoidal lobes. Second City

Figure 9 - God’s Finger. Third City.

Figure 10 - Dom Pedro I’head.. The head is supported by the neck throughout an erosion surface. Third City.

Figure 11 - This cave is a product of alveolar erosion. Fourth City.

Sixth City

    The tortoise (photo 2) and the elephant are the most known features of this city. Both are forms covered by mostly pentagonal polygons which normally puzzles the geologist both in origin as in the formation process.
    Some geologists believe that these polygons are an heritage of former glacial conditions in time of deposition of sand. Fortes (1996) assumes them as contraction cracks, where the running water from rain carved ladder-like polygons. As a matter of fact, polygons are a very common feature in Sete Cidades as well in another ruinform site, the Buriti Alps, near Picos, in the central-eastern part of the Parnaiba Basin.

Seventh City

    In this city, alveolar erosion and polygons features are the main atractions. The Indian’s cave is a good example of alveolar erosion, covered by polygons.

CONSERVATION POLICY

    The main objectives for controlling the area are (Medeiros, 1998):

• to keep an area dominated by the cerrado vegetation, with caatinga and latifoliate forest elements, its ecological diversity, potentialities and genetic resources;
• to keep the representative biotic community that occurred originally in this area;
• to keep geological monuments and the scenic beauties;
• to keep the hydrological  production;
• to keep rupestrian paintings and other objects of the historic-cultural heritage;
• to promote education in order to get public respect to environment;
• to make possible and to promote scientific research and general studies inherent to the park objectives; and
• to promote leisure within the general objectives of the park.

     As all that exists in the park belongs to the community,  visitors are not allowed to dispose any material in trails, roads,  belvederes and picnic places; to  polute and spoil soils and creeks; to mutilate plants; to set fires or lit candles for religious rites out from the proper places for it; to  chase or hunt the park animals, to make excessive noise, as shouting or to keep high volume stereos and radios; and  to pull or to break signalization plates.

BIBLIOGRAPHIC REFERENCES

Caputo,M.V. 1985. Late Evonian Glaciation in South America. Palaeogeography, Palaeoclimatology, Palaeoecology, 51:291-297, 1985.

Coutinho,R. 1997. Enigmas de Sete Cidades. Ideal, Piripiri, 78 p.

Della Fávera, J.C. 1984. Eventos de Sedimentação Episódica nas bacias brasileiras. Uma contribuição para atestar o caráter pontuado do registro sedimentar. In:  XXXIII Congresso Brasileiro de Geologia,33,Rio de Janeiro,1984, SBG. Anais:489-498, .

Della Fávera,J.C. 1990. Tempestitos da Bacia do Parnaíba. Um ensaio holístico. UFRGS, Porto Alegre. Tese de Doutoramento, 243 p..

Fortes,F. 1996. Geologia de Sete Cidades. Fundação Cultural Monsenhor Chaves, Teresina, 142 p.

IBAMA. 1979. Nac– Plano de Manejo – Parque Nacional de Sete Cidades. Brasília, 61 p.

Medeiros,E.S. 1998. Projeto de sinalização do Parque Nacional de Sete Cidades.  IBAMA, Teresina, 43p.

Schwennhagen,L. 1928. História Antiga do Brasil – de 1100 AC a 1500 DC. – Teresina , Imprensa Oficial.