ABSTRACT
The Crato Member of the Santana Formation is an important geologic and paleontologic site in Brazil, located at the interior of Northeastern region. This unit is part of the Sedimentary Araripe Basin where the main outcrops are in the Northeast flank.
Litologically, it is composed by horizontal calcareous beds, interfingered to shales, siltstones and sandstones, deposited during the Lower Cretaceous (about 120 m. y.). These calcareous rocks are exploited by the cement and ornamental rocks industries, forming an important mining activity in the country. These rocks are also very rich in fossils, including an abundant and diversified fauna and flora, well preserved. The entomofauna and the flora represent a significant record to the knowledge of the angiosperm development.
The mining activities cause partial fossil and local nature fisiography destruction. An urgent preservation program as the creation of parks and eco-turistic activities is most necessary.

    The Crato Member of the Santana Formation, composed basically of horizontal calcareous beds (Figure  1) is a conspicuous paleontologic and geologic site of the Northeast Brazilian region.

Figure  1 – Simplified stratigraphic scheme for the Aptian-Albian lacustrine system of the E Araripe Sub-basin.

Figure  3 – Location map of the main outcrops of the Crato Member (clay-carbonate rhythmites and laminated limestones) at the E Araripe Sub-basin. The draw was rotationed to obtain a better view of the site localizations.

    The paleontological researches in the Araripe basin began in 1823 when Spix and Martius arrived in Brazil in a scientific mission. This research trip was organized by the King of Baviera Maximiliano Jose I, in order to study the South American natural resources. These researchers registered the first fossiliferous record of the Araripe region, mentioning the occurrence of fishes in calcareous concretions (Romualdo Member) and in limestones (Crato Member).
    From 1836 to 1840 the Gardner travel made incursions to the site. By this time, the first studies about the fossil collections of the Brazilian Geological and Mineralogical Survey were made.
    In 1947, R. S. Santos (a brazilian researcher) described the fish Dastilbe (Figure  4) of this basin and suggested fresh water as depositional environment to the limestones of the Crato Member.
    From 1963 to 1971 K. Beurlen, professor in the Geology School of Recife – Pernambuco, carried out studies of the Mesozoic of the Northeast region and, in 1971, defined the stratigraphical table of the Santana Formation with three members: Crato (lower), Ipubi (intermediate) and Romualdo (upper). He also suggested the first ecological relation. Some authors (Beurlen, 1963; Martill, 1993; Neumann & Cabrera, 1999) suggested to elevate the category of the Crato Member to Formation.
    The insects are very diversified and until now there are 200 species described. To this classification participated A. Costa Lima, I. D. Pinto, I. Purper, R. G. Martins Neto and D. A. Grimaldi.
    In relation to the plants more studies are needed as they are abundant, diversified (woods, leaves, seeds, flowers and fruits) and well preserved.

Figure  4 – Dastilbe elongatus Santos.

LOCALIZATION

    The Araripe Sedimentary Basin is located at the interior of the northeastern Brazil, in the Borborema Structural Province (Brito Neves, 1990), occupying part of Piauí, Pernambuco and Ceará States. It is located between 38⁰30’- 45⁰50’W and 7⁰05’ - 7⁰50’S. This basin was divided by Rand & Manso (1984) in two sub-basins: West (W) and East (E) (Figure  2).
    The Crato Member of the Santana Formation outcrops only at the scarps of the E sub-basin of Araripe. This sub-basin is West limited by the meridian 39⁰45’ (close to Santana do Cariri Town) and at East is limited by the meridian 38⁰30’ (close to Bonito da Santa Fé Town). Its North limit is at the parallel 7⁰05’ (close to Nova Olinda Town) and the South limited at the parallel 7⁰40’(close to Jati Town), totalizing an area of aproximately 5,500 km².

SITE DESCRIPTION

    The Crato Member of the Santana Formation constitute a lacustrine sequence, chiefly carbonated, that was originally named of "calcários de Sant’ana" by Small (1913). The carbonated lacustrine facies associations of this member are mainly composed by six carbonated units (C1 to C6) (Figure  1). These units are constituted of micritic laminated limestones and clay-carbonate rhythmites, with colours varying from light to dark brown and light to dark grey, alternating with shales and fine sandstones. The clay-carbonate rhythmites are always at the base of the carbonated units and are recovered by the laminated limestones. Salt pseudomorphs (halita) and various well preserved fossils: fishes (mainly Dastilbe (Figure  4)), insects and plants, are within the laminated limestones (Figure 5).

Figure  5 – Plants and insects of the Crato Member of the Santana Formation: A. Gimnospermae (Brachyphyllum Brongniart); B. Angiospermae (undetermined flower); C. Angiosperma (undetermined flower); D. Zigoptera; E. Ephemeroptera; F. Blattodea. These specimens belong to the fossil colection of the Federal University of Pernambuco. The bars in each foto correspond to 1 cm.

Figure  6 – Detailed map of location of the three main paleontological and geological sites at the E Araripe Sub-basin.

    The outcrops description, in which the carbonated units are well exposed, are:

    The laminated limestones outcrops in both, left and right sides of the quilometer 5-6 of the road (CE-255) that conect the Towns of Nova Olinda and Santana do Cariri (Figure  7). The limestones are exploited by craftmen and traded to construct walls, tables, houses, etc.
    In this area the units of laminated limestones are 5-10 m thick, and constitute a single, tabular body (carbonated unit 6 = C6, see Figure  1), that extend laterally in all area. This tabular body is limited at the base and at the top by shales.

Figure  7 – Craft exploitation of laminated limestones (carbonated unit C6, Figure  1) of the Crato Member of the Santana Formation. This outcrop is located in km 4-5 of the road CE-255, between Nova Olinda and Santana do Cariri Towns. The photo shows the rejected material, after sorting the best one.

    The Santa Rita and Caldas quarries (Figure  6) belongs to the IBACIP - Barbalha industry of cement, which exploit the units C3, C4 and C5 (Figures 1 and 8).

Figure  8 – Photo of Caldas quarry, showing the exploitation front SW-NE. The Crato Member of the Santana Formation (represented by the cabonated units C3, C4 and C5, Figure 1) is exploited by the cement industry.

    The Crato Member rocks constitute an important calcareous mine that are exploited by the cement and ornamental rock industries (Figures 7 and 8). These mining activities have been responsible by the erosion increase and river packing, causing environmental destruction (Figure  7).
    The fossil trade also contributes to the destruction of the deposits through ilegal exploitation, that mainly occurs at the ornamental rock mines.
    Thus, it is necessary an urgently preservation program of this important site. The creation of parks, for example, would help to preserve some areas. The Araripe plateau region is extremely rich in natural beauty regarding the geomorphology, the mineral water fontains, the vegetation and the nice climate. This region has many activities related to the tourism as the paleontological museum, commerce of crafts, religious parties, recreation clubs, hotels, etc. Each aspect contributes to the increase of the regional economy with eco-touristic activities.

REFERENCES