Botucatu Formation
| Wiki Write-Off Entry | |
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| Student Chapter | Federal University of Rio Grande do Sul |
| Competition | June 2015 |
The Botucatu Formation is an aeolian sandstone deposit in the Paraná basin, which displays large-scale sets of cross strata (1-30 m; Figure 1), formed in a desert environment similar to today’s Sahara Desert, during the Jurassic to Cretaceous on the Gondwana supercontinent, with an area of approximately 1,500,000 km².[1]
Figure 1 Large-scale of cross strata structure in the Botucatu Formation in Uruguay.
Figure 2 Inverse grading in the Botucatu Formation in Uruguay.
Its thickness can reach 400 m, the base is made of conglomerates and gravelly sandstones and coarse-grained sandstones, representing ephemeral streams and aeolian sand sheet deposits. It consists mainly of fine to medium-grained quartz sandstones, of red, pink or pale yellow color, well sorted, texturally mature, may contain altered feldspar cemented by silica or iron oxide, which gives it the reddish color and also shows inverse grading.[2](Figure 2.)
Its morphologic reconstruction shows simple to compound aeolian dunes and complex linear draas. Its preservation is due to the fragmentation of the Gondwana Supercontinent when lava flows from the Serra Geral Formation covered this erg.[3]
The paleowind regimes show a monsoonal pattern during the Jurassic and Cretaceous, the main winds blew to the NE during the Southern Hemisphere winter and to the SE during the Southern Hemisphere summer[2].
One of the largest aquifer system, the Guarani Aquifer, is located in the Paraná Basin and the Botucatu Formation is part of it as a very permeable sandstone sealed by the lava flows from the Serra Geral Formation.[4]
References
- ↑ Milani, E. J., J. H. G. Melo, P. A. Souza, L. A. Fernandes, and A. B. França, 2007, Do Paraná: Cartas Estratigráficas--Boletim de Geociências da Petrobras, Rio de Janeiro, v. 15, n.2, p. 265-287
- ↑ 2.0 2.1 Scherer, C. M. S., and K. Goldberg, 2007, Palaeowind patterns during the latest Jurassic–earliest Crateceous in Gondwana: Evidence from aeolian cross-strata of the Botucatu Formation, Brazil: Palaeogeography, Palaeoclimatology, Palaeoecology v. 250, p. 89-100.
- ↑ Scherer, C. M. S., U F. Faccini, and E. L. Lavina, 2000, Arcaboucoestratigráfico do Mesozóico da Bacia do Paraná, in M. Holz, C. M. S. Scherer, and K. Goldberg, Palaeogeography, Palaeoclimatology, Palaeoecology, pp. 335–354.
- ↑ Scherer, C. M. S., 2002, Preservation of aeolian genetic units by lava flow in the Lower Cretaceous of the Paraná Basin, southern Brazil: Sedimentology, v. 49, p. 97–116.