Ribeira do Iguape Basin Morph genesis and the Environmental Systems

 

Prof. Dr. Jurandyr Luciano Sanches Ross

DEPTO.GEOGRAFIA FFLCH/USP

E-mail: juraross@usp.br

 

Abstract: The Ribeira do Iguape river basin’s relief, shows very different geomorphologic macro-compartments that are related to the regional top hills surface, the strongly dissected hills from Sea mountain intermediate levels, the tectonic depression lands of low Ribeira and the sea and fluvial coastal plain. This relief genesis suffered Precambrian tectonic influences, in the brasiliano cycle phases, accompanied by bending of regional metamorphisms, magmatism underlying sintectonic, flawing complexity and fractures, phases of middle-Cenozoic tectonic reactivation, shared with the past and nowadays climatic activities, as well as with the oceanic ones. The tectonic and waters mechanics and chemical processes conjugation along millions of years define the current relief morphologies and these basin environmental systems.

 

Key Words: systems, morphogenesis, tectonic, chemical erosion, relief.

 

Introduction

 

The Ribeira do Iguape Basin geomorphologic analysis, embracing lands of Sao Paulo and Paraná States was developed having the geomorphologic mapping as technician-scientific support starting from radar and satellite images in the 1:250.000 scale, as well as the topographical letters use, geological and pedologic, concerning to promote the integrated analysis of natural components, aiming to supply subsidies for environmental systems units definition and its later cartographic reports.

 

 

 

 

 

 

 

Objectives and Justifications

 

The Ribeira do Iguape basin geomorphologic research, has been developed with an initial concern of settling down an understanding of the hydrographical basin group relief macro-compartments, as well as formulating the regional morphogenesis interpretation in the hydrographical basin interest ambit. The other concern is focused on the geomorphologic research applicable in the environmental systems units definition context looking to the territorial administration stepped in the environmental planning politics and based in the sustainability development concept. This basin integrated knowledge, in the economical and social development perspective on a side and the other side, the concern to the conservation, preservation, and environmental recovery is important challenge for an area whose physical-natural and historical-economical characteristics are extremely complicated and challenging in the finding durable alternatives to elevate the level of income and life quality to populations that inhabit the area. The social problems complexity and the partial delay and economical stagnation the area has been going thought, beside and in almost in confrontation to the interests not less important related: preservation/conservation/recuperation environmental, turn this hydrographical basin a significant focus of multiple interests that frequently conflict to each other, but that can perfectly have an equation inside an integrated development plan.

 

Methodological Hypotheses

 

The used methodology in the geomorphologic research has taken as referential the three levels of relief investigation proposed by Ab´Saber (1969), associated to what Ross (1992) establishes for the making cartographic reports, identifying and mapping of the geomorphologic facts, following the taxonomic levels then defined.

 

The Ab´Saber (op cit) geomorphologic investigation three levels are first, the topographical compartments, second, the landscape superficial structure understanding, and third, the landscape physiology. This way, the first level establishes the relief division in compartments and it is elaborated the most precisely as possible the description in the relief ways; the second, referring to the landscape superficial structure understanding is concerned to analytically describe and to establish correlations of the observed facts in field concerning the relationship among the relief elements forms, the pedologic covering, the colluviums deposits, alluvial, Soil characteristics as well as the litology and its structural arrangement, besides the correlations to the vegetable covering and the current climatic characteristics and paleoclimate indicative elements. In this level, Ab´Saber (1969) defines that the concern is the landscape superficial structure static understanding that comes from a dynamic manifestation of the same along the recent geological time. The third level, the one of the landscape physiology, is centered in the current dynamics gauging that builds along the time the relief forms and develops the soils types, as well as “natural landscape” functionality as a whole. About mutual dependence among the nature several components, the physiology or functionality or dynamics that act in the relief forms is synergistically influencing all the geographical stratum other components, in a mutual and permanent interaction process, meantime intensity varying along time and physical-territorial space.

 

The geomorphologic charting, following the Ross taxonomic levels (1992) favors and completes the theoretical-methodological application of Ab´Saber’s (op cit) approach because Ross (op cit) when defining that the relief can be charted in six taxonomy, he helps to identify, to describe and to explain the most varied sizes and genesis forms existence. So he defines that the relief six different taxonomy are: the morphostructure, the morphosculpture, the forms physiognomic types or patterns, the forms individually, the sections or elements of the forms or slopes, and last the current forms of the current processes that grow in the slopes, that can also be from man induction, as cuts, embankments, sliding scars, recent deposits, ravines, furrows, gullies among others. To the analysis made at Ribeira do Iguape basin, the Ab´Saber’s third level was treated starting from the field observations and some essays with the pocket “penetration” tool and the relief smaller dimensions taxonomy, such as the slopes elements and the forms produced by the current processes, because of the scale they were not able to be charted.

 

Relief and Interactions: Geotectonic Context

 

The Ribeira do Iguape basin geomorphologic systematic charting made possible to identify, starting from the analysis made in the 1:250.000 scale seven units or relief macro-compartments, being four in high lands and three in low lands. Those units were organized under two great morphostructures: a denominated of Atlantic Ocean Bending Strip Morphostructure where it can identify three Morphosculptural  Units denominated Paranapiacaba Plateau and Mountain Chain, Sea Mountain Chain, and Coastal Hills, Guapiara Plateau and Alto Ribeira-Turvo Plateau. The other morphostructural unit, that involves the low lands was called Low Ribeira Tectonic Depression Morphostruture Unity where we can identify three morphosculpture units, which are: Tectonic Depression of the Low Ribeira, Coastal Plain Cananéia-Iguape and Low Ribeira Plains and Fluvial Terraces (vide geomorphologic map).

 

The called Atlantic Ocean Orogenic Belt strip, where Ribeira do Iguape basin belongs to, shows a high litologic-structural complexity, result from long and regional magnitude intense tectonic activities that happened in the medium and superior Precambrian, reactivating tectogenics of epirogenetic character in the Jura-Cretaceous and Cenozoic, associated to the what Almeida (1967) denominated Wealdeniana reactivating. Gontijo (1999), leaning on in Barbosa (1934), Lamego (1936), Leonardos (1940), Ebert (1956/68/71), Almeida et alii (1973/76), Almeida (1977), Hasui et alii (1976/78), Almeida & Hasui (1986), Cordani et alii (1986), Schobbenhaus & Campos (1986), I Break Neves (1990), Hasui & Sadowski (1976), IPT (1981/82), Santoro (1991), Almeida (1986), Riccomini (1989), among others, elaborates a synthesis where informs that “the Precambrian more prominent structures in the Brazilian southeast are the great bunches of ductile dissension with general direction ENE to NE, of dextral movement and EW to NW of sinister character. These structures have sinuous geometry separating prolonged portions or sigmoid, printing a pattern of almond blocks. They show width in kilometers, lengths even hundreds of kilometers and expressive strips of milonit, ultramilonit, and associated blastomilonit. On glide structures, they stand out in the Precambrian rocks the band compositional together to the schistose and the milonitic foliation. The band together is characterized by the alternation of bands mafic with felsic quartz-feldspatic. The schistose with minerals plaque or prismatic and joined minerals in form of lens, resultants of the dynamic conditions associated to the regional metamorphism. The milonitic foliation is formed as product of the flow plastic in form of blade imposed by simple dissension along the dissension zones. The most important lineal structures are the mineral lineal and the line of associated stretching the milonitic rocks that coincide “to the axis of larger deformation stretching.”

 

Following the synthesis presented by Gontijo (1999), “the Precambrian structural picture was changed by the middle-Cenozoic tectonic, that generated flawing of elapse character, normal and locally inverse, along the main dissension zones and of foliation plans, generating scarps of flaws and basins.” Some of these fail delimit borders of sedimentary Cenozoic basins as well as the Sea Mountains scarps, Mantiqueira, Paranapiacaba among others. “The exposed carry on exhibits varied metamorphism degree and granitites associated to Precambrian term-tectonic events, which determine the fundamental litho-structural lines of South American platform.”

 

The flawing elapses system, normal and inverse, characterizes the strip of the Atlantic Ocean Orogenic Belt define a continental rifts system of Brazilian southeast strip, according to Hasui (1978), IPT (1981), Almeida (1976), Riccomini (1989). These are willing mostly in the ENE direction and frequently they contain in the Cenozoic sedimentation (Oligocene-Miocene) continental tectonic depressed areas basins, where on the lacustrine sediments happen detritus deposits in alluvial fans form. Still in agreement to Riccomini (op cit), the completion of those continental basins is characterized by sintectonic sedimentation, with its borders flaws influence. This way they are the Cenozoic sedimentary basins of São Paulo, Taubaté, Rezende, Curitiba, and Baixo Ribeira among others.

 

The Ribeira do Iguape basin area, as Vitte describes (1998), “is composed of pre-Cambrians rocks belonging to the bending Ribeira strip, defined by Almeida et alii (1973) or Bending of Southeast Area, according to Almeida et alii (1976), direction ENE-WSW parallel to the coast line. In this basin Precambrian geological framework, following from the coast to interior we will find as dominant litology, in agreement to IPT- (1981) and MINEROPAR (1989), the Inferior Arquean-Proterozoic – migmatit strips of different structures with pyroxene granulites, and granulites quartz-feldspatic intrusions occupying the mountainous coastal strip, immediately in the strip to the interior associated to the inferior and medium Proterozoic, prominent to Turvo-Cajati Compound, they occur mica-schist, claytons, metassilt, quartz-schist and homogeneous migmatite.

 

Subsequent we can find out the superior Proterozoic rocks– Açungui and Pilar Complex, with dominance of pelitic rocks, where they stand out metamorphic rock made by mica, metassiltite, carbonate, quartzite micas and feldspatic, marbles and dolomites calcite, and wide occurrences of intrusive masses of sintectonic granites and restricted alkaline intrusion of pyroxene in Cajati proximities. In the low lands Coastal prevails the not consolidate sandy sediments from sea origin and in the interior plains the recent fluvial deposits and alluvial and colluviums-alluvial deposits Pleistocene not selected from Pariquera-açu and Sete Barra formations, that sustain higher levels of terraces and tops from some lower hills positioned close to the Ribeira fluvial axis.

 

 

 

 

Relief Configuration and Regional Morphogenesis

 

The macromorphology arrangement, as the own basin configuration, constituted by the Ribeira do Iguape river and more or less complemented to north by its principal basin flowing from the left margin, the Juquiá river, define a high regional geological-structural subordination, which is ENE-SSW, that is in agreement with the Brazilian Orogenic Belt direction of Atlantic Ocean in the south-southeast of Brazil. That space arrangement, in that area, is also in agreement with the coastal strip of Brazil cutting, what impose us to admit the significant influence of geotectonic characteristics in relief construction process of this area. The São Paulo State geomorphologic map, made by Ross & Moroz (1997) already revealed, above all in the east strip or Atlantic strip of the State, how much litologic-structural arrangement and geotectonic interfered and still interfere in the space organization and genesis as of macrophorms of regional relief as in the smaller forms that use to characterize the dominant modeled, called by Professor Aziz Nacib Ab´Saber of “Sea of hills” (Mares do Morros) from Atlantic Tropical Brazil.”

 

In that area, where in spite of the tops and slopes forms be mostly convex or as the renowned Professor Ab´Saber calls, “in breast” forms, came from the current humid tropical morph climate processes and from paleoclimate arid and semi-arid atmospheres from past interferences, they keep, however, marks from tectonic effects and structural-structural influence in the space arrangements of their superior orders valleys, in the preferential slopes of main valleys disposition, in alignment to the main ridges tops, in the alignment to hills systems, in the net distribution of small alveoli plains, as well as the great tectonic depressions belonging to the “rifts system” with the scarps produced by the normal and elapses flaws, products of Superior's Mesozoic  and Cenozoic reactivation, that are frequently structured in agreement to the regional lining ENE-SSW structural directions.

 

The rocky masses, whatever they are, products from different regional metamorphism degrees, or even from magmatism, came from underlying sintectonic masses intrusions of the Medium and Superior Precambrian, are willing structurally in that preferential direction and this imposes to the relief sculptural processes significant interferences. Because of that, the main fluvial arteries as the medium and high Ribeira do Iguape, its principal left margin flowing, the Juquiá river, the high Tietê river basin, the Paraíba do Sul river medium and high basin, as well as its makers the Paraibuna and Paraitinga rivers basins obey as a rule the regional direction ENE-SSW.

 

The strong dissection that the hills modeled present in Brazilian Atlantic strip - above all southeast-south, outstand to a group of factors, among which stand out the dense flaws and inherited net existent fractures from old orogenic phases, later reactivated/enhanced by the Cenozoic tectogenesis, that besides promoting the widespread and unequal South- American crust platform upping, placed in significant topographical projection, what we call today Sea mountain scarps, Mantiqueira, Paranapiacaba among others. Complementing the flaws and fractures net, the litologic junctions or contacts are also important inductors to the waters concentration processes with narrow and deep valley development that is frequent in the area. The schistose/foliation-lineaments-band together plans by minerals concentration in a same rocky mass also contribute to pluvial-fluvial valley incision. The low porosity and permeability of crystalline rocks and crystalofilian in humid tropical climate atmospheres induces the physical-chemistry performance and mainly pluvial waters chemistry and they penetrate the underground through the weakness lines (fractures, flaws, committees, lineaments, foliation, banding), that with outstanding topographical gradients differences between springs and base levels local or regional contribute to the dissection.

 

The rocks meteorization through a continuous and invisible process of chemical reaction between the waters and the minerals constituent, at the same time produces a voluminous mass of altered products progressively residual that come from primary minerals chemical transformation secondary minerals and the losses for the chemistry/lixiviation that also contribute to the valley deepening, it sculpts the slopes and it generates a modeled mostly by slopes and convex tops promoting in its group the relief dissection in hills and hills with high drainage channels density, very carved valley and slopes with strong steepness.

 

 

The Ribeira do Iguape basin, in its own group, is framed in the conditions geological-geomorphologic, above described, considering the peculiarities of each area evidently. So, the regional relief evolution, it can be taken as referential to defined morphologic surface according to Maack (1953) of First Paranaense Plateau whose Bigarella (1954), called as surface kept crystalline rocks by cut from a “Paleozoic Paleoplan” or “Peneplan pre-Devonian”, and later as “Surface Alto Iguaçu” or still Almeida (1964) in the State of São Paulo, identifies as “Itaguá Surface of pre-Devonian age”, starting from the one which, after the epirogenesis Cenozoic effects that placed it in low lands position for progressive and slow position of high lands, the erosive processes come along the more recent geological times lowering the regional relief and placing in projection the structures rocky sustained specially for granites, quartzite, gneisses granites and even calcareous and marbles, and lowering the relief in less resistant litology as the mica-schist, metamorphic rock made by micas and migmatite strongly band together, failed and highly addressed ENE-SSW.

 

Almeida (op cit), when characterizing and interpreting what he denominated “Western Crystalline Plateau” morphogenesis, the same as later IPT (1981), followed for Ross & Moroz (1997) baptized of “Plateau de Guapiara”, points out that the Itaguá Superficies determines the largest roof of that plateau area that is sustained by porfiritic granites in its largest extension. He considers that the highest areas, witch configure water and relief divisors usually in crests form among 1050 to 1150 m positioned belong to the Japi Superficies maintained by the granites, quartzite and eventually calcareous and marbles in the area of Apiaí and Ribeirão Branco, going to State of Paraná. Bigarella (1954), observed that the Alto Iguaçu Surface, pre-Devonian is defined from the First Planalto Parananense, meeting, in the north portion, more specifically in the area drained by the Ribeira do Iguape basin discharge with different characteristics, because there such surface is “carved in Açungui Series bent rocks (metamorphic rock made by micas, quartzite, calcareous, and dolomites) and in the intrusive granites”, going ahead, describes that “quartzite strips and rocks more resistant calcareous to the erosion, rise from the First Plateau as heads of strata, constituting long chains of arduous elevations. They deserve special reference the lines of mountains constituted by quartzite, more resistant rock to the intemperism and mechanic desegregation. Between them we have the mountain of Ouro Fino (1025 to 1150 m) and Bocaina (1200 to 1300 m).”

 

Maack (1961) brings a significant contribution, when he writes  “from the end of Cretaceous to the tertiary, the granites sinorogenic (sintectonic) nuclei fragmented by flaws through the tensions caused by the Andean orogenesis.” What we can conclude from Almeida's (op cit), Maack (op cit) and Bigarella (op cit) contributions, is that the lands more discharges of Ribeira do Iguape basin are leveled by an extensive pre-Devonian morphologic surface, whose tops are leveled among 850-950 meters, with extremely dissected relief in form of hills with very carved valley and very tilted slopes and that they are sculpted mostly in the metamorphic rock made by micas, micaschists, calcareous, dolomites, granites, quartzite, gneisses granites rocks types and they come form this level of residual mountains top sustained by granites, quartzite or even for calcareous more resistant to erosion, whose tops are generally among 1050 to 1150m, where it stands out the Paranapiacaba and Bocaina mountains in São Paulo and Ouro Fino mountain in Paraná. Starting from that regional top surface, the Ribeira basin progressively loses altitude in its ending direction, always defining very dissected relief in steep hills form sculpted in metassedimentary rocks less resistant to the physical-chemists waste of water processes, with prominence for the metamorphic rock made by micas, micaschists and calcareous, and leaving as higher lands the quartzite, granites, gneisses granites and eventually calcareous and more resistant marbles.

 

Almeida (1964) writes about that: “... in Paranapiacaba Mountain sub zone, the geological structure participation in the drainage net configuration and in topographical ways comes out. Granites or gneisses granites support the principal mountains, in the largest water divisors. They are for example, the one of Bananal, Prainha and Itatins, this one reaching about 1300m, ... ... Paranapiacaba mountain sharp front larger part is granite constituted. Quartzes are some salient crests, where calcareous also sustain high relief, granites are largely the waters divisor of Juqueri-guaçu and São Lourenço rivers, to amount Miracatu, as well as several high mountains in the discharge basin of Jacupiranga river.” He goes on the description affirming, “Naturally, it belongs to filets and schist areas to configure low relief and to shelter the principal subsequent rivers.” Keeping the São Paulo state south-southeast area morphogenetic interpretation, Almeida (op cit) manifests that “the principal Sea and Paranapiacaba mountain scarps are in habitually established in resistant rocks, be granites or gneisses granites, while subsequent valley are opening for remounting erosion, in the less resistant to erosion strips rocks.” Following he says “.... from Santos area to SW, more the aspects of the Sea mountain are diversified, always in consequence of litologic impositions to the erosive processes.” “... .The gneisses porfiroblastic strip with associated granites go on to Ribeira River, behind it, showing important schist rocks strip from Grupo São Roque. In that conditions, for simple differential erosion starting from the Ribeira River, settled down important subsequent drainage, tributary of Juquiá River.” “... .A ridge of Itatins and its extensions to west, the Bananal mountains, Pouso Alto and Pouso das Onças stay almost entirely due to the gneissic constitution, with local granites, surrounded as they are, to north and west, for less resistant schist areas of São Roque series.”

 

In São Paulo-Paraná boundary, “... it resurges as granite-gneissic front turned to the ocean.” Ab´Saber (1972), when talking about the tectonic and paleoclimate effects in Brazilian relief compartment definition, he states “... we want to refer to the presence of tectonic areas as zones or preferential strips to depressions intermountain flat formation... in fact, while the pediplans had larger possibilities to extend inside the subsequent outlying depressions, the pediments walked above all in the less resistant litologys strips and in the strips subject to very dense diaclasament (plane that keep or tends to keep two rocky parts separated), in intermountain type zones...”, further on, he affirms “... the low Ribeira own basin, in São Paulo south sub sea zone, constitutes a significant case of a embayment form penetration in the pediplanation, among long big Appalachia feasts of regional mountains.” In this morphogenetic conception elaborated by Ab´Saber (op cit) it is fundamental to understand his affirmation that “.... we are serious reasons to think that the maximum phases of sinuous line in the bottom of the valley erosion pronouncing again the traverse sections of subsequent and consequent valleys, have been the ones of driest climates transition to the most humid, while the pedimentation maximum phases or even pediplanation would have made it in the humid climates to the dry or semi-arid moderate ones transition.” Silveira (1952), had already placed as important, besides the regressive and differential erosion effect in Ribeira do Iguape basin relief elaboration, the tectogenesis signs saying that “... following several cuts in Pananapiacaba mountain and just considering geomorphic elements, they suggested us the hypothesis of flaws assigned in that mountain and so south-north aligned”, it continues and he affirms “... the Itatins solid... studied with aerial pictures help and surrounded observed, in low flight, causes us the impression of block raised by flaw.”

 

However, the emphasis morphogenetic presented by Silveira (op cit), is much more to Davisian evolutionary model that interprets the “Baixada do Ribeira” (Ribeira Slope) as a “peneplan” and therefore come from normal erosion (fluvial) combined to sea level variations caused by the continental platform ups and downs, above all in Pleistocene, how we can notice by the following transcription: “.... in sea platform situation looking to the sculpture in the Baixada interior area, there was gravel deposition in the bottom of rivers, that rising 25 to 30 meters altitude, made unfeasible the first sea terraces appearance...”, “...afterward the coast suffered new rising, with sea and fluvial terraces levels already existent being up. The valleys are carved again, sculpturing new terraces...” and he concludes“... the coast downhill in small width took to the valley drowning and swamps and widespread alleviating creation...”, and he concludes considering that it is from that drowning that the plains and current sea sandbanks build up.

To Bigarella, Mousinho & Silva (1965), in the Ribeira Valley “...happened a leveling surface, Pd1designated, whose correlative deposit would be the Formation Pariquera-Açu plio-Pleistocene, with remainders found in even hills of 100 meters altitude...” This sculpture was related to “...climatic changes that conditioned the lateral degradation processes alternation and lineal erosion, which were really important to the Pariquera-Açu's Formation genesis sediments.” So, as Ab`Saber (op cit), Bigarella, Mousinho & Silva (1965), consider that the Ribeira do Iguape basin and mainly the Low Ribeira, relief is above all a product of the dry climates (mechanical morphogenesis) alternations with humid climates (chemical alteration and fluvial transport). We must, however, to point out that as Ab´Saber & Bigarella (1964), as Bigarella & Andrade (1965) consider that the dry x humid events have happened especially in the Pleistocene, but Ab´Saber (1972), would prefer to date them in Neocene or starting from Miocene and extending in Pliocene and Pleistocene, or in the Superior Tertiary and Quaternary.

 

Face to the facts, until now exposed, considering important the regional litology structural arrangement and the Ribeira basin rocks different resistance to waste role, the tectonic factor also deserves prominence, especially concerning the established altimeter differences between the Ribeira do Iguape basin low lands and high lands around it. This way, Lima, Melo & Coimbra (1991), talk about the Cenozoic sediments like this, “... the discontinuous areas occurrence filled out by Cenozoic continental sediments and coastal is an outstanding feature in São Paulo State east part geology. The factors associated to such accumulation genesis are, actually, superior since they affected the whole southeast area and a part of country south area.” It continues further on and they affirm “... the principal factor associated to the sedimentation is, undoubtedly, tectonic... They present grabens form and semigrabens with continental sediments completion...”, specifically referring to low Ribeira tell “the case of the Sete Barras formations (Paleocene) and Pariquera-açu (Neocene) and deposits related to them, in the Ribeira do Iguape low valley present as main factor tertiary tectonic rupture phases associated.” About the coastal plains they say, “the most important associated factor “the sedimentation refers to the quaternary glacial-eustatic variations. The deposits are represented by Cananéia (Pleistocene) Formation and younger coastal strings.”

 

Bearing in mind the exposed considerations, and also following the Ross & Moroz (1997), interpretations when elaborating São Paulo State geomorphologic map, the low Ribeira area is genetically constituted related to the tectogenetic Cenozoic processes that, at the same time that they originated Sea and Paranapiacaba mountain steps, they produced closed tectonic depressions or not, that received continental fluvial transport sediments with alternate rainy phases to more balanced phases associated or not to dry and humid climates alternations. What seems clear for us, it is that Pariquera-Açu's Formation deposits, that show in gravels heterometers form and mostly symbolized by quartzite and quartz, come out covering again partially some tops and low hills slopes without defining continuous strata, because frequently they appear associated to fine and medium debris discontinuous and seemingly defining what have been considered alostractgrafic deposits.

 

On the other hand, we cannot also confuse such continental deposits, with what frequently happens in almost all the low Ribeira hills tops and slopes, where it is observed dense migmatite and mica-schist alteration mantles with abundant quartz in veins that when suffering pedogenesis they develop angular pebbles in outline layers wrapped up in clay or clay-silts soils mass. The fine material, as the quartzes gross, suffer along the time in humid tropical environment, lateral and vertical migration for gravity and for mineralogical constitution difference, where density differences are included, specific weight, plasticity, cohesion, and attrition, that progressively separate concentrating the angular quartz pebbles on discontinuous layers, that accompany in subsurface the external silhouette morphology and topography from each one of the hills. So, on large part of the Low Ribeira Tectonic Depression hills, what is observed in outline in the highways cuts are alteration materials produced by water physical-chemical activities and tracing natural processes that make possible the development in the Soil- hillside soil come from higher levels recent materials slopes.

 

These Soil-hillside soil come from higher level pedologic coverings, are rich in angular quartzes gravels that figure in form of layers (stones lines) irregular and discontinuous that accompany in subsurface the hills convex morphology. That material is not able, therefore, to be confused to the fluvial deposits also irregular, discontinuous and heterometer, but with rolled pebbles, that recover the hills partially and which are identified by Pariquera-Açu Formation, and that doesn't seem to have as regional expressiveness as it was previously considered.

 

The most recent research work developed in low Ribeira, in Juquiá municipal district, by Vitte (1998), where he tried to understand the morphogenetic evolution, promoting intense analysis among the litostructures, tectonic, relief-soil forms, coming to the soils micromorphology analysis. The researcher can conclude that the relief origin and evolution comes from long processes that involve the tectonic activities as with old and recent effects, structural and mineralogical influences of rocks as well as the paleoclimate effects of alternate dry climates to humid, as well as the current pedogenesis. That complex evolution, along the time and space, it is known by etchplanation, and Vitte (op cit), considers starting from his research, that the low Ribeira, with its complex evolution, can be understood through the “etchplanation that has climate and tectonic control in a certain time, once, that they command the intemperism front deep, losing gradually fine and solutes in superficial horizons.” He places in prominence that “... the deep of alteration front intensifies in the failed areas and in those that present fractures, and in these last ones the pattern of fractures defines the existence of a zone of lumps in subsurface, while in the superficial horizons the organic matter intense action, associated the macro porosity, makes possible on a side the iron oxidation, while it allows the sheet suspended subsurface performance, that conjugated allow the oxides lessivage and iron and aluminum ox-hydroxides, in direction as to the alteration front as sidelong. They create like this conditions to the rich superficial horizons in skeleton quartzes development.” Further on he concludes, “... in this dynamic etchplanation process it interferes the quartz veins role, because when the aloalterit soil genesis happens transforming micas and feldspars, the iron and aluminum ox-hydroxides promote the pH increase and the consequent quartz veins dissolution and gradually of its individuals, preparing them for the planning process when they will constitute crushed rock and jointly to the materials they will form complex outlines.”

 

Vitte contribution (1998) on the Low Ribeira morphogenetic processes comes to the gather to Ross (1987, 1991). He concludes analyzing the Mato Grosso Mountainous Province relief evolution. In this area, it can be noticed that the altimeters variations and the morphologic configurations are associated to the processes complexity that involve the Precambrian tectonic, the meso-Cenozoic tectonic reactivation, the sedimentary strata structural-structural arrangements, old levels of erosion surfaces dismantled by the tectonic activities, and old erosion surfaces exhumed by the Cenozoic erosive processes.

 

Besides, it was verified that the existence of several levels morphologic/topographic are currently associated to sculptural processes not only the dry paleoclimate phases, but in particular the waters chemical activity influence promoting reactions and unequal wastes among the different litologies that have the sandstone, calcareous, dolomites, arkoses, foil clay rock, and clays prominence in the area. In the São Paulo State Geomorphologic Map construction process, Ross & Moroz (1997), and later Ross (1998), deepening the analytic work on the subject could establish some considerations that are also meet that previously identified conception.

 

The Ross & Moroz (op cit) and Ross (op cit) verification that different morphologic/topographic levels found at the plateaus on east São Paulo are related the a complexity of morphogenetical processes whose demonstrate in space and time and they are involved in different times and geneses of tectonic activities, as debarments, metamorphisms, magmatism, old filaments, flaws reactivation in Cenozoic, with old erosion surfaces evidences, as in the top of the Japi Mountain where the quartzite mass is leveled/planed in disagreement to the band together plans and pseudo-strata dive.

 

It called the attention, however, the different morphologic/topographic levels whose are observed among the rocky structures represented by the granites masses as the ones of Itapeti, Cantareira, Itaqui, São Francisco, São Roque, Paranapiacaba Mountains and many others, which have their altimeter levels tops among 850, 900 to 1000 meters, beside the rocky quartzite masses sculpted relief, as Pico do Jaraguá (Jaraguá Pick) Serra do Japi (Japi Saws), Montanha de Voturana (Voturuna Mountain), whose tops are between 1100 and 1200 meters. In the region of those prominent relief, there is a vast surface whose tops are leveled about 800m altitude that are specially sculpted in particular in metamorphic rocks migmatite and gneisses intermixed by extensive micaschists strips and filets that for their time are frequently in lower topographic positions.

 

These facts have taken Ross (1998) to consider to the São Paulo State Atlantic strip plateaus (Planaltos da Faixa Atlântica), that:

 

- “The area relief evolution has in the Cenozoic tectonic processes, important role as starter of vigorous sculptural processes, as in the Sea and Mantiqueira Mountains scarps as in the top of plateaus surfaces...”;

- “those sculptural processes had already been presented in the pre-Cenozoic and they have created significant differences altimeters because of the litologic variations and structural arrangements of them, not being obligatorily surfaces of different erosion, but unequal lowering of land surfaces.”

- “the Cenozoic fine deposits (clay) being little expressive in extension and volume front the areas extensively with strongly dissected relief, it suggests waste processes (erosion and transport) predominance for primary minerals chemical dissolution, being deposited or just staying in situ  only the chemical and mechanics processes “residues”.”

- “the higher relief presence sustained by solid igneous rocks (granites) and metamorphic rocks (quartzite) surrounded by lower relief sculpted in metamorphic rocks with larger lines of weakness density also suggest the chemical processes of erosion and transport prevailing to the mechanics.

 

It is considered that the primary rocks/minerals meteorization process and their transformation in secondary minerals, that compose the pedologic covering and the Cenozoic deposits is a significant sculptural process, where the dissolved minerals are transported by the oceanic waters, remaining on the continents the quartz sandy residues and more restricted fine deposits (clay, silt).”

 

So, although it has had scanty testimonies that last times there were drier climates whose have contributed to the regional relief sculptural processes, the humid atmospheres and specially hot chemical activities are the ones which establish on a side the definitive mark in the morphosculptural processes in the mountains and hills relief forms and other the morphotectonic processes and morphostructural arrangements with the resistances to the wastes differences the different rock families that establish the regional morphogenesis understanding parameters, as well the Ribeira do Iguape basin.

 

The Sea Plain, that is in the Ribeira do Iguape basin coastal strip and that correspond to one of the basin Geomorphologic Unity, identified and mapped as Cananéia-Iguape Coastal Plain grew starting from the sea levels variations in the last 120 thousand years through the sea transgressions and regressions, thoroughly studied and published by Suguio & Martin (1976), Martin & Suguio (1978a), Suguio & Tessler (1984). About this, Suguio & Tessler (op cit) consider that in Brazil coastal plains formation main factors are four. They are: - sands sources; coastal drift currents; traps for sediments retention; and the sea level variations. Having those elements as formation factors, Suguio & Tessler (1992), present in the Trips Routes volume of the 37th Brazilian Congress of Geology, on the Cananéia-Iguape (SP)Coastal Plain Quaternary Deposits, the evolutionary model of this relief unit formation, establishing so:

“First stadium - during Cananéia's Transgression  maximum (120.000 years AP.), the sea must have reached the Sea mountain base, when the transitional clays and navies of the Cananéia Formation have been deposited, covering again the Pariquera-Açu Formation;

Second stadium - with the regressive phase coming, seas crests deposits were sediment in the Cananéia's Formation  sandy deposits top;

Third stadium - during this phase the sea level was lower than today (110m below the current level concerning 18.000 years AP), when the rivers that drained the coastal plain should have s deeply eroded the Cananéia's Formation  deposits;

Fourth stadium - in the beginning of the last transgress event the sea level arose quickly, having surpassed the current level between 6000 and 7000 years AP.

This way the sea have invaded the lowered by the erosion areas, forming an extensive plane land.” Certainly, it is because of those last two erosive phases followed by the Santos transgress that, as it marks Ross & Moroz (1997), “the drainage, in this relief unit demonstrates a dendrite pattern having straight sections indicating to important fracturing directions with physically powerful influence. A net drainage largely happens on fluvial plains of plane bottoms, demonstrating that they are fluvial drowned valleys.”

 

The Low Ribeira Fluvial Plains are morphologic and genetically articulate to the Coastal Plain, and both are strongly related to the Ribeira Tectonic Depression genesis. That plain is characterized by a densely ramification fluvial plains that present great difference among the places from Registro in Ribeira river and Juquiá and Jacupiranga rivers basins. While in the city of Registro, plain spaces and narrower prevail terraces, constituted specially by clay-sandy deposits and gravels, prevailing the main river channel more carved with longitudinal profile with a little more accentuated steepness.

 

In the spaces up river, the plains are wider, originated mainly from drowned valley by the sea sedimentation, with very low topographical gradient, where the waters have great difficulty to be drained by the sea. In this inferior space of Ribeira do Iguape river, a big sinuosity creek prevails and the floods water time of permanence is larger. In that section, the plains are sandier and more humid presenting water sheet very close to the surface and frequently surfacing in the same and forming extensive swamps.

 

- Ribeira do Iguape Basin Environmental System Unit

 

The Environmental System Units, received geomorphologic denominations, above all because of the relief macro compartment extreme significant in the area. However, it was also very important the analysis and charting of the Use of land in the Hydrographic Basin, besides of course other variables as the Units of Conservation, socioeconomic aspects and hydroclimate behavior. So, the units that have been identified and defined belonging to the basin, in the 1:250.000 scales are:

 

I- Cananéia-Iguape Coastal Plain system (Conservation Unit Zones);

II- Ribeira Plains and Fluvial Terraces system;

III- Low Ribeira Tectonic Depression Hills and Little Mount system;

IV- Hills and Scarps of Sea and Paranapiacaba Mountains system  (Conservation Unit Zones);

V - Ribeira's High Hills and Top of Plateaus Surfaces System.

 

 

Among the Environmental Systems of five big units identified, some have more man presence and another is in better environmental conservation. The identified Units received the following denominations, that can be accompanied by the Ribeira do Iguape Basin Environmental Unit Systems Map:

 

I- Cananéia-Iguape Coastal Plain System.

 

This unit differs from the others not only for its physical-natural characteristics, but also above all because of its morphogenesis and the biodiversity aspects. It is part of an important estuarine area of big biophysical complexity, where swamp ecosystems happen beside the plains and sea sandy strings, cut out by fluvial plains where marine sediments are reworked for the rivers and added with other sediments coming from the interior of continent. It recovers the sandy lands there deposited by the sea transgression/regression phases (Cananéia and Santos transgressions) a dense medium load Forest vegetable covering, largely preserved, accompanied by Swamp vegetation banges that occupy the interstitial plains (Swamp plains). They grow in those plane lands and hydromorphed family sandy soils specially, since the non consolidate sandy sediments store great water volume, resulting in extremely shallow water sheet. This way, texture Podzol Hydromorphic soils where prevail sandy, Soils Organic tiomorphic, above all in the coastal plain interior areas, where it can also be found xenomorphic vegetation.

 

In the climatic aspect, a hot and humid environment, where the registered average of maxim temperatures vary from 22 to 29 Celsius degrees and the low ones oscillate between 15 and 22 Celsius degrees. Rains are abundant and frequent, happening 1500 mm/a variation in the less rainy years to 3500 mm/a in the rainiest years, being the months of June, July and August the less rainy months. That unit is the one from São Paulo coast that is preserved, although there is relative demographic concentration in specific areas as Iguape and Cananéia and lineal strips of occupation in the Ilha Comprida in the coastline of open to the ocean beaches. Besides the occupations related to a summer and second residence recent urbanization, they extend for the Cananéia channels margins and Ilha Comprida riverine villas of traditional populations which are devoted above all to the fishing activities.

 

Because being an immense natural fragility unit to the urban occupation processes, thanks to the plane relief characteristics, sandy soils and not consolidate, water sheet close to the surface, to be rich in biodiversity and nursery for countless animal species reproduction, the area is practically all delimited by Environmental Conservation Units and under looking federal and state organs environmental managers vigilant. It is, therefore, an environmental unit of absolute interest to preservation and environmental conservation.

 

II- Ribeira do Iguape Plains and Fluvial Terraces system.

 

That unit involves the plane lands that border the fluvial courses in the Low Ribeira or in the Ribeira Tectonic Depression area. A fluvial plains of dense ramification that presents significant differentiation among the amount Registro spaces, in the Ribeira river, and in the Juquiá and Jacupiranga rivers basins characterizes it. In these areas, although the plains go by intense and frequent floods in the rain picks, the water time of permanence is smaller than in the up stream spaces, where the floods, also frequent, maintain the plains for a very long time under the waters.

 

This fact is related to the materials genetic differences and that compose those plains. While in the spaces near springs plains and more narrow terraces prevail and with the main more carved river channel and with steepness longitudinal profile a little more accentuated, than to the up stream spaces, the plains are wider, originated predominantly from drowned valley by the sea sedimentation, with very low topographical gradient and, consequently, the waters have more difficulties to drain to the sea direction. Because of this, they tend to disperse for the low and plane margins, where, at the same time that they deposit new transported sediments from the interior  continent, replacing sea sediments previously deposited.

 

The plains in those more spaces up stream are sandier and with sheet very close water to the surface hindering the economical activities, above all the banana's agriculture. Whereas near the spring , the sediments are loamier, with the sheet a little deeper, the soils better drained, facilitating the agricultural activities, and for that they are almost totally areas occupied with banana plantations.

 

So, the plainer soils up stream are particularly of  Hydromorphic organic type, standing out Gleys Tiomorphic and Organic Tiomorphic, while in the spaces near the spring loamy alluvial soils prevail standing out eutrophic Cambisoils above all. Being an unit with characteristics differentiated morphogenetic, significant differences are also observed in the natural vegetable covering, because while in the areas up stream prevail hydrophilic vegetation associated to herbaceous pioneering formations and drier spaces with forest gallery, today turned into pastures, in the spaces near the spring forests galleries prevailed, almost totally substituted by extensive banana plantations.

 

Although fluvial plains every extension is in extremely vulnerable area to the erosion/deposition processes, thanks to the frequent catastrophic floods episodes, the spaces up stream are more problematic than those near the spring, because of the extension and flood waters permanence time.

 

The cities of Registro, Eldorado, and Sete Barras are totally or partially inside the Fluvial Plain in the space near the spring, where the flood time is smaller, but the problems are more important when these happen. Besides the material damages that the floods cause to the farmers, with total or partial losses of their productions, in the cities, the material damage is added to the great damages to the health, above all the most lacking populations than they reside in precarious houses and risk areas. In spite of the origin mistake, with cities implantation so to river-edge, whose plains are periodically flooded, it is almost impossible to promote the re-urbanization, with periodically reached populations reallocation, due to the high economical and social cost. For this, those plains areas will be only able to suffer smaller floods impacts with intervention in the flowing out fluvial regularization system, lessening the floods picks.

 

III - Low Ribeira Tectonic Depression Hills and Little Mounts Unit System.

 

It encircles low hills of convex tops and short slopes, with medium inclinations oscillating between 10 and 20% altitudes to the sea level between 30 and 50m, belonging to Dc14, Dc15 kind. These in hill forms, grow on low metamorphism rocks, above all mica-schist and filets. It is sculpted on the same siltic-loamy pedologic covering thickens with discontinuous layers and composed thickness for quartz angular pebbles and heterometers, constituting the called stone lines. That material recovers the hills surfaces continually and it accompanies the convex morphology of the same ones. It is, therefore, Soil and hillside soil come from higher levels material flowed directly from underlying mica-schist pedogenesis.

 

Tests with pocket “penetrating” tool in the horizon B (loamy) demonstrated that is a quite united material and that it offers reasonable resistance to the penetration, reaching values among 3.0 to 4.0 Kgf/cm2, for a scale that varies from 0 to 4.5 in the used equipment. In the cuts with soil profile exhibiting the horizon C, the tests were applied with the “penetrating” tool, obtaining results that used to oscillate between 2.0 and 3.0 Kgf/cm2, demonstrating that this horizon, owing to the low metamorphism rocks alteration as metamorphic rock made by micas and mainly mica-schist are very full of silt with smaller cohesion among the particles, offering smaller resistance to the penetration. They are, therefore, more fragile to the erosive processes when exposed in surface by cuts, embankments and filling in and leveling services.

 

In the borders of the unit sections it comes out small hills (little mounts) with above 100-150m altitudes, little longer slopes and more tilted, usually between 20 and 40% and sculpted on larger metamorphism degree rocks, usually migmatit and gneisses. While on the hills the soils that it develops correspond to Red-yellows alic Podzolic of loamy to very loamy texture, on the little mounts the shallowest soils of the Cambissoils alic type associated to Latossoil and Podzolic prevail, also with loamy textures. In the hills and in the little mounts the soils present gravels (pebbles of quartz) concentration usually coming out among the horizons B and C limits.

 

In this unit climatic conditions are also hot and humid, with medium temperatures from maxims varying between 24 and 32 Celsius degrees and the medium from low temperatures oscillating between 14 and 21 Celsius degrees. Along the rainiest years they happen up to 2500mm/yr and in the least rainy ones the values oscillate about of 1200 mm/yr., enrolling as less rainy months of June and July. The natural vegetable covering, that can still be found at deprived reservations residual forests, it is the Atlantic Tropical Forest. There are lots of areas with vegetation in solemnity-regeneration process, appearing cleared soils and secondary forests in discontinuous forests. However, the unit is practically occupied with agricultural activities, standing out the banana's cultivation firstly, secondarily the tea and the extensive milk and livestock production. The natural fragility to the erosive processes and land natural movements is low, and it could happen  soil profiles not stability when these ones reach the more full of silt horizon C.

 

IV - Hills and Scarps of Sea and Paranapiacaba Mountains Unit System (Units of Conservation Zones).

 

The area that this unit takes, as the Unity I, is quite preserved of man influences, in spite of human occupation progresses pressure as in the Ribeira discharge basin area as in the low part. That unit extends for the Sea, Paranapiacaba Mountains and thought the Ribeira do Iguape river medium valley mountainous strip, mainly embracing São Paulo State lands along the Ribeira do Iguape tributary medium and high courses, as Juquiá, Turvo, Jacupiranga, Pilões, Betari rivers basins, among countless smaller ones.

 

In this unit is included, Paraná State small spaces, in the areas whose involve the Turvo river basin mountainous lands, especially Adrianópolis municipal district fraction. As the own denomination indicates, a vigorous mountainous and sharp relief represents the unit, where the hills present long slopes, very tilted, with deep and relatively narrow valley.

 

The altimeter levels vary in the low parts where it arrive at the Low Ribeira Tectonic Depression, around 100-200 m, but it reaches up to 1000-1100 m in the highest sections, mainly of Paranapiacaba Mountain Chain, prevailing in the high sections, altitudes among 700-900m. The São Paulo State geomorphologic map marks strongly for that unit standard in relief forms dissected, of the Da54, Da34, Da44, Da33, Da24, Dc33, Dc34 type, what indicates very carved valley, usually above 80m, but it could surpass the 160m, and slopes with inclinations measured in field among 40 - 60%, but with sections that arrive to 70-80%.

 

The unit presents great litologic diversity and with significant structural complexity. It is inserted in the Ribeira bending strip presenting in the center-south part, through where it goes to Ribeira river valley, larger low metamorphism rocks concentration, above all the metamorphic rock made by micas, quartz-metamorphic rock made by micas, as well as calcareous, and higher degree metamorphic as the quartzite, marbles by dolomite and, in the most parts to north and south, outstanding presence of varied structures migmatite and granites sintectonic extensive occurrences.

 

Because of its geological, geomorphologic, and climatic characteristics, the area presents a soils types very accentuated complexity. Although the shallow soils prevail, the rocky blooming is more evident in the quartzite and granite occurrences. However, they are found with reasonable frequency very thick soils, altering in the slopes sections, given the inclination differences through more shallow soils. So, dominantly, we have the Cambisoils alic and Cambisoils dystrophic that associate to Podzolic Red-Yellow and Latosoil Red-Yellow, especially of loamy to very loamy textures, being not frequent Litolic and the Rocky Blooming, in spite of mountainous character of the area.

 

From the climatic point of view, it is extremely humid, with pluvial annual indexes varying among 1000 mm/yr. to 3000mm/yr for the less and rainier years respectively. The rains happen the whole year because, on a side, of the orografic effect and to the other side the frequent entrances of cold fronts and the less rainy months are June, July, and August. The temperatures are little lower, especially because of the altitudes and latitudes, indicating annual medium values for the averages of low among 11 to 20 Celsius degrees and averages of maxims among 22 to 32 Celsius degrees.

 

In this mountainous and rainy environment, it grows the dense, high continuous and extremely rich in biodiversity Atlantic Tropical Forest. Sections frequently comes out, in particular close to the highways and to Ribeira do Iguape river, to deforested areas with agriculture and subsistence livestock, beside abandoned lands with clared soils and extensive forests of secondary forests in high self-recovery.

 

The human occupation is, in its major part, incipient, mainly in São Paulo State, where prevails the traditional population called cabocla, who inhabits rural houses small agglomerates or even separately, practicing besides the agriculture and subsistence livestock, medicinal extractives incipient, alimentary vegetable and ornamental species. Those populations usually occupy relief sections less tilted as small plains and fluvial terraces whose are susceptive to the periodic floods, or in the low slopes hills close to the bottom of the valley. In the small space that embraces the Paraná State, it prevails deforested areas with extensive sections with clared soil and forests secondary come from the relative abandonment of lands, face to the cultivation difficulties that the natural conditions impose, beside extensive cattle activities of low productivity.

 

In São Paulo State, where the preservation conditions are very larger, the area is almost totally delimited by State Environmental Conservation Units, as Parks, APAs, Reserves, Wild Life Zones and Natural Patrimony protection. In the fragility ambit, it is a sensitive area not only in the biodiversity aspects, but also in the geomorphologic processes ambit, because it is seen from extremely favorable atmosphere to all the types of erosive processes unchain, as well as highly susceptive to the mass movements or land sliding and block rolling.

 

In the field risings, it can be seen in the highways cuts and even out of them many sliding, mainly in the crossed structures metamorphic rock made by mica, mica-schist, calcareous and migmatite alteration mantles. Some measured with pocket “penetration” tool indicated penetration indexes oscillating among 2.5 to 3.5 for scale from 0 to 4.5 Kgf/cm2, demonstrating to be relatively big the those land fragility potential.

 

V - High Ribeira Hills System in Top Surface Unit.

 

The High Ribeira Plateaus constitute a mountainous environment with level tops in the main divisors around 900 m, finding higher sections whose reach 1000-1100 m, usually maintained by more resistant metamorphic rocks as the quartzite, presenting morphology of prolonged and continuous crests or granites masses intrusive, that extend for large areas.

 

Alternating to those prolonged and higher relief, it prevails forms at hills of convex tops with relatively narrow and deep valley with slopes very tilted, usually varying among 30 to 60%. That morphology, with extremely dissected relief Dc24, Dc33, Da33, Da32, Da43, and secondarily Dc22, Dc14 of type, is sculpted in a great rocky formations diversity with prominence for the metamorphic rock made by micas, quartz-metamorphic rock made by micas, ortogneisses, paragneisses, quartzite, calcareous and marbles dolomites, granites porphiridic and granites sintectonic, aligned structurally in the regional NE-SW direction.

 

The lowest relief sections are predominantly maintained by the metamorphic rock made by mica and calcareous like what happens in the unit IV. In that structural-structural complexity, that leads to the development of very vigorous relief pattern, also grows a great soils diversity, with Cambisoils alic, Cambisoils dystrophic prevalence associated to Litolic and rocky blooming, that only happen in the slopes very tilted and in the quartzite domain areas. The soils Podzolic Red-Yellow and Latosoil Yellow and Latosoil Red-yellows alic type of loamy texture already tend to happen in the less tilted sections of the hills slopes, in association with Cambisoils, but above all in continuous stains, in the areas of headboards of Ribeira tributary in the Regional Top Surface (level of the 900m), where the relief come about in form of mountains and low hills with less carved valley and less tilted slopes.

 

In the bottoms of valley Ribeira and its larger tributaries rivers, restricted narrow and little prolonged fluvial plains occurrences are frequent, positioned in the concave sections of the fluvial bed sinuosity and, because they come from fluvial origin, they are susceptive to periodic floods. Some cities as Ribeira, Itaóca, Adrianópolis and Cerro Azul, besides farms headquarters and small rural towns settled at those ranches. They are terrestrial low and imbedded in the middle of hills with alluvial soils and risks due to annual periodic floods

 

In the climatic aspect, it is a little colder area, however quite humid. The pluvial indexes annual vary from 1000 mm/yr. to the less rainy years being able to, in isolated points, to get to 4000 mm/yr. for the rainiest years. The rains happen the whole year, being the months less rainy June, July and August. The average temperatures of annual low oscillate from year by year between 11 and 20 Celsius degrees, while the averages of annual maxims vary from year by year between 22 and 32 Celsius degrees.

 

It used to grow in that area the Atlantic Tropical Forest, with transition areas to the Araucaria Forest, found residually in the coldest and highest sections of the area. It is an area totally occupied by the agricultural activities with prominence for temporary cultures and orange culture in Cerro Azul and surroundings, prevailing, however, for the unit group, pastures with bovine creation, extensive and dominant extensive areas of pinus forestation gone back to the woods industry and resins production, although it is not continuous extensive areas of clared soils in abandoned pastures, forests of secondary forest in high solemnity-regeneration apprenticeship, as well as very restricted and isolated forests of araucaria and secondary of bracatinga.

 

Besides those activities, we can find as in São Paulo State, as around in Apiaí, as in the Paraná State, in the Rio Branco do Sul and Abapã neighborhoods, close to Castro, intense miner activity gone back to the granite extraction, used as by the Cement industry (Rio Branco do Sul and Apiaí) as for Whitewash and soils corrective production. There is, still, the granite exploration for ornamental stones and breaks in isolated points.

 

In the fragility aspect, the relief characteristics indicate that the area is very susceptible to the erosive processes, above all produced them by the superficial rainwaters drainage whose are abundant. The relief characteristic, associated to the rainy climate and increased to the conventional agricultural activities, with a net of unpaved highways, without an appropriate maintenance for pluvial waters drainage control, they generate a lot of erosive activity. The sliding of lands, although they have been observed in some points along the highways cuts; they are much less frequent than in the area hill/mountain of the unit IV. Although the Unit is practically deforested, great areas have been used with pinus reforestation.

 

From the environmental point of view, that is preferable to the pastures or, mainly, to the highly predatory conventional agricultures for the characteristics of the area. The natural potentiality of the area is mostly for forestation and limestone mining, granite and other mineral resources, and, secondarily, for livestock activities and, in very restricted sections, for technique agriculture of large scale.

 

4. BIBLIOGRAPHY