O programa binacional de Mapeamento Geológico e da Geodiversidade na fronteira Brasil-Güiana possibilitou a revisão e integração da nomenclatura estratigráfica do Supergrupo Roraima ao longo do Bloco Pacaraima nas regiões extremo norte brasileira e ocidental guianense. A área corresponde a um buffer de aproximados 25 quilômetros a partir da fronteira, em um trecho definido pelo Monte Roraima (região de tríplice fronteira) e vizinhanças da vila Mutum, no Brasil, e serra Monkey, na Guiana, ao longo do rio Maú ou Ireng. O flanco sul da bacia assenta exclusivamente em rochas efusivas e vulcanoclásticas dos correlatos grupos Surumu e Burro-Burro.

PALAVRAS-CHAVE:
Supergrupo Roraima; Fronteira Brasil-Guiana; estratigrafia

Autoria

Nelson Joaquim Reis ^**Corresponding author.

Serviço Geológico do Brasil - Superintendência Regional de Manaus - Manaus (AM), Brazil. E-mails: nelson.reis@cprm.gov.br; leda.fraga@cprm.gov.br; leandro.betiollo@cprm.gov.br; telma.faraco@cprm.gov.brSuperintendência Regional de ManausBrazilManaus, AM, BrazilServiço Geológico do Brasil - Superintendência Regional de Manaus - Manaus (AM), Brazil. E-mails: nelson.reis@cprm.gov.br; leda.fraga@cprm.gov.br; leandro.betiollo@cprm.gov.br; telma.faraco@cprm.gov.br

Serge Nadeau

Guyana Geology and Mines Commission (GGMC) - Georgetown, Guiana. E-mails: goldenserge@hotmail.com; jimmy@ggmc.gov.gy; deokumar_lachhman@yahoo.com; randy_alt07@yahoo.comGuyana Geology and Mines CommissionGuianaGeorgetown, GuianaGuyana Geology and Mines Commission (GGMC) - Georgetown, Guiana. E-mails: goldenserge@hotmail.com; jimmy@ggmc.gov.gy; deokumar_lachhman@yahoo.com; randy_alt07@yahoo.com

Leda Maria Fraga

Leandro Menezes Betiollo

Maria Telma Lins Faraco

Jimmy Reece

Deokumar Lachhman

Randy Ault

*Corresponding author.

SCIMAGO INSTITUTIONS RANKINGS

Figuras | Tabelas

Figuras (16)
Tabelas (2)

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Figure 1:
The PSB along the Venezuela, Brazil and Guyana border and the regional geological setting of the Guiana Shield.

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Figure 2:
Simplified geological map of the Pakaraima Sedimentary Block along the Brazil and Guyana border and the location of the Guiana Shield, north of the Amazon Craton.

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Figure 3:
Schematic sedimentary section of the Roraima Supergroup along the Venezuela and Brazil border as proposed by Reis and Yánez (2001Reis N.J. , Yánez G. 2001. O Supergrupo Roraima ao longo da Faixa Fronteiriça entre Brasil e Venezuela (Santa Elena de Uairén - Monte Roraima). In: Reis N.J. , Monteiro M.A.S. (Eds.). Contribuições à Geologia da Amazônia. Manaus: SBG/Núcleo Norte. v.2. p.115-147.): UF) Uiramutã Formation; VF) Verde Formation; PF) Pauré Formation; CF) Cuquenán Formation; QF) Quinô Formation.

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Figure 4:
Paiuá Creek. (A) Layer of volcanogenic ferruginous sandstones with small cross-stratifications covered by pyroclastic flows and cineritic deposits (B); (C) and (D) Ignimbrite with pumice fragments.

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Figure 5:
The PSB along the Brazil and Guyana border near Monkey Mountain. In this aerial view, along the southern border of the basin the Iwokrama volcanics are directly correlated with the Surumu volcanics as well as the lower sedimentary rocks of the Arai Formation of the Roraima Supergroup extends continously in both countries.

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Figure 6:
Rebenque Creek in the vicinity of Mutum Village. Limbs of a tight fold dipping to the north (A) and to the south (B) with shear zones occuring parallel to the east-west striking axial plane of the fold. (C) Lilás (Purple) Mountain. Open fold with limbs striking to the north and south; (D) At the foot of Lilás Mountain outcrops of pyroclastic rocks of the Surumu Group as in the Paiuá Creek are mainly composed of lapilli tuffs. The contact between the pyroclastic and terrigenous rocks seems to be gradational and the first 50 meters is mainly of quartz sandstones.

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Figure 7:
Gravel road to Mutum Village. Shear zones cutting the pyroclastic rocks of the Surumu Group resulted in the formation of pinnacles with prominent foliation striking E-W with down-dip lineation.

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Figure 8:
Gravel road to Uiramutã Village. (A) Symmetrical ripple-marks (lower flow regime) at the top of sets of compact and reddish mudstones interpreted as playa-lake deposits associated with the aeolian sandstones of the Arai Formation; (B) Cross-cutting and rythmites intercalation of alternating mudstones and siltstones.

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Figure 9:
Gravel road to Uiramutã Village (dunes field). (A) Fine and friable pinkish arkosic sandstones interpreted as aeolian dunes; (B) Reactivation surface between sets of large-scale trough cross-stratifications; (C) View of a major trough displaying cross-stratification with palaeocurrent flow direction to the NE; (D) Grain fall and grain flow structures present in the arkosic sandstones, very common in aeolian settings by grain avalanches on the slip faces of sand dunes (see arrows and coin for scale).

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Figure 10:
Paiuá Creek. (A) Rib-and-Furrow sedimentary structures in quartz sandstone of the Arai Formation (see hammer for scale); (B) sets of large-scale trough cross-stratifications with palaeocurrent flows direction to the SW. Parting-step lineations are common and plane-bed reflects an upper-flow regime transport of grains; (C) pebbly sandstone with well-rounded quartz pebbles; (D) cosets of trough cross-stratifications corresponding to fluvial conditions of sedimentation of the Arai Formation.

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Figure 11:
Arai Formation paleocurrents measurement numbers (n) and associated azimuth (vector of paleoflow mean direction): A,B,C from Pinheiro et al. (1990Pinheiro S.S., Reis N.J. , Costi H.T. 1990. Programa Levantamentos Geológicos Básicos do Brasil. Geologia da Região de Caburaí, Nordeste de Roraima. Escala 1:100.000. Estado de Roraima. DNPM/CPRM. Superintendência Regional de Manaus, 1v., il. 91p.); D,E from Keats (1973Keats W. 1973. The Roraima Formation Project. 1971-1973 Final Report. Geological Surveys and Mines Dept., Georgetown, Guyana, Report WK 1/73. 68p.) and F,G from Ghosh (1981Ghosh S.K. 1981. Geology of the Roraima Group and its Implications. In: Simposium Amazonico, 1., Puerto Ayacucho, Venezuela. Memoria…, p.22-30.).

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Figure 12:
Cross Hill, Uiramutã Village. (A) West of Cross Hill including the four formations of the Suapi Group named Uiramutã, Verde, Pauré and Cuquenán (bottom to top and left to right); (B) fine-laminated reddish siltstones of the Verde Formation; (C) arkosic sandstones to pebbly sandstones with trough cross-stratifications present within the Pauré Formation.

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Figure 13:
Aerial view of the Guyanese side where broad hills predominate and altered pyroclasts of the Uaimapué Formation have a characteristic pinkish colour.

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Figure 14:
Aerial view of the natural border represented by the Maú-Ireng River between Brazil and Guyana. The area displayed is of the Uaimapué Formation composed mainly of reddish tuffaceous rocks. The aerial photo was taken a few meters south of Orinduik Falls.

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Figure 15:
Orinduik Falls, Maú/Ireng River at the border between Brazil and Guyana.

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Figure 16:
View of the Cuquenán and Mount Roraima Tepuy (from left to right). Both mountains are composed of sedimentary rocks of the Matauí Formation along the triple border junction between Venezuela, Brazil and Guyana.

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Table 1:
Stratigraphy of Roraima Supergroup proposed by Reis and Yánez (2001Reis N.J. , Yánez G. 2001. O Supergrupo Roraima ao longo da Faixa Fronteiriça entre Brasil e Venezuela (Santa Elena de Uairén - Monte Roraima). In: Reis N.J. , Monteiro M.A.S. (Eds.). Contribuições à Geologia da Amazônia. Manaus: SBG/Núcleo Norte. v.2. p.115-147.) along the Brazil - Venezuela border and it extension to Guyana. Compilation of ages of the volcanic rocks underlying the Roraima Supergroup along the border between Brazil and Guyana (Surumu Group and Iwokrama Formation), of a pyroclastic rock unit of the Uaimapué Formation in Brazil and of intruding sills of the Avanavero Dolerite in Brazil.

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Table 2:
Stratigraphy of the Roraima Supergroup in Brazil and in Venezuela through time as proposed by various authors: 1) Bouman (1959Bouman Q.C. 1959. The Roraima Formation, Northern of Territorio do Rio Branco. Belém, Petrobras/Renor, Relatório Interno 350-A. 17p.); 2) Yánez (1972Yánez G. A. 1972. Geología del Área de Santa Elena de Uairén (Mapa de Interpretación de 12.000 km2 en escala 1:250.000). In: Conferencia Geologica Inter-Guayanas, 9., Ciudad Guayana, Venezuela. Memoria… p.660-667., 1977Yánez G. A. 1977. Província Geológica de Roraima, Geología Estructural e Geomorfologia de su parte Suroriental, Venezuela. In: Congresso de Geologia, 5., Caracas, Venezuela. Memoria… p.845-854.); 3) Reid (1972Reid A.R. 1972. Stratigraphy of Type Area of the Roraima Group, Venezuela. In: Interguiana Conference Geological, 9., Georgetown, Guyana. Memoria..., p.343-353.); 4) Reis et al. (1985Reis N.J. , Pinheiro S.S. , Carvalho J.E. 1985. Subdivisão litoestratigráfica da Formação Suapi - Grupo Roraima, Território Federal de Roraima. In: Simpósio de Geologia da Amazônia, 2., Belém, Pará. Anais... SBG, p.408-420.); 5) Santos (1985Santos J.O.S. 1985. A Subdivisão Estratigráfica do Grupo Roraima. In: Simpósio de Geologia da Amazônia, 2., Belém, PA. Anais... SBG. p.421-431.); 6) Reis et al. (1988Reis N.J. , Pinheiro S.S. ; Costi H.T. , Souza Cruz C.E. 1988. A Subdivisão do Grupo Suapi no Contexto do Supergrupo Roraima, Porção Setentrional do T.F. de Roraima. In: Congresso Latino-Americano, 7., Belém, Pará. Anais... SBG, p.389-398., 1990Reis N.J. , Pinheiro S.S. , Costi H.T. , Costa J.B.S. 1990. A Cobertura Sedimentar Proterozóica Média do Supergrupo Roraima no Norte do Estado de Roraima, Brasil: Atribuições aos seus Sistemas Deposicionais e Esquema Evolutivo da sua Borda Meridional. In: Congresso Brasileiro de Geologia, 36., Natal. Anais... SBG, p.66-81.); 7) Reis and Yánez (2001Reis N.J. , Yánez G. 2001. O Supergrupo Roraima ao longo da Faixa Fronteiriça entre Brasil e Venezuela (Santa Elena de Uairén - Monte Roraima). In: Reis N.J. , Monteiro M.A.S. (Eds.). Contribuições à Geologia da Amazônia. Manaus: SBG/Núcleo Norte. v.2. p.115-147.); 8) Keats (1973Keats W. 1973. The Roraima Formation Project. 1971-1973 Final Report. Geological Surveys and Mines Dept., Georgetown, Guyana, Report WK 1/73. 68p.). The correlation between the stratigraphy of the Roraima Supergroup in Brazil and Venezuela with the unit subdivisions in Guyana are shown in the last two columns to the right (this work).

Figure 1: The PSB along the Venezuela, Brazil and Guyana border and the regional geological setting of the Guiana Shield.

Figure 2: Simplified geological map of the Pakaraima Sedimentary Block along the Brazil and Guyana border and the location of the Guiana Shield, north of the Amazon Craton.

Figure 3: Schematic sedimentary section of the Roraima Supergroup along the Venezuela and Brazil border as proposed by Reis and Yánez (2001Reis N.J. , Yánez G. 2001. O Supergrupo Roraima ao longo da Faixa Fronteiriça entre Brasil e Venezuela (Santa Elena de Uairén - Monte Roraima). In: Reis N.J. , Monteiro M.A.S. (Eds.). Contribuições à Geologia da Amazônia. Manaus: SBG/Núcleo Norte. v.2. p.115-147.): UF) Uiramutã Formation; VF) Verde Formation; PF) Pauré Formation; CF) Cuquenán Formation; QF) Quinô Formation.

Figure 4: Paiuá Creek. (A) Layer of volcanogenic ferruginous sandstones with small cross-stratifications covered by pyroclastic flows and cineritic deposits (B); (C) and (D) Ignimbrite with pumice fragments.

Figure 5: The PSB along the Brazil and Guyana border near Monkey Mountain. In this aerial view, along the southern border of the basin the Iwokrama volcanics are directly correlated with the Surumu volcanics as well as the lower sedimentary rocks of the Arai Formation of the Roraima Supergroup extends continously in both countries.

Figure 6: Rebenque Creek in the vicinity of Mutum Village. Limbs of a tight fold dipping to the north (A) and to the south (B) with shear zones occuring parallel to the east-west striking axial plane of the fold. (C) Lilás (Purple) Mountain. Open fold with limbs striking to the north and south; (D) At the foot of Lilás Mountain outcrops of pyroclastic rocks of the Surumu Group as in the Paiuá Creek are mainly composed of lapilli tuffs. The contact between the pyroclastic and terrigenous rocks seems to be gradational and the first 50 meters is mainly of quartz sandstones.

Figure 7: Gravel road to Mutum Village. Shear zones cutting the pyroclastic rocks of the Surumu Group resulted in the formation of pinnacles with prominent foliation striking E-W with down-dip lineation.

Figure 8: Gravel road to Uiramutã Village. (A) Symmetrical ripple-marks (lower flow regime) at the top of sets of compact and reddish mudstones interpreted as playa-lake deposits associated with the aeolian sandstones of the Arai Formation; (B) Cross-cutting and rythmites intercalation of alternating mudstones and siltstones.

Figure 9: Gravel road to Uiramutã Village (dunes field). (A) Fine and friable pinkish arkosic sandstones interpreted as aeolian dunes; (B) Reactivation surface between sets of large-scale trough cross-stratifications; (C) View of a major trough displaying cross-stratification with palaeocurrent flow direction to the NE; (D) Grain fall and grain flow structures present in the arkosic sandstones, very common in aeolian settings by grain avalanches on the slip faces of sand dunes (see arrows and coin for scale).

Figure 10: Paiuá Creek. (A) Rib-and-Furrow sedimentary structures in quartz sandstone of the Arai Formation (see hammer for scale); (B) sets of large-scale trough cross-stratifications with palaeocurrent flows direction to the SW. Parting-step lineations are common and plane-bed reflects an upper-flow regime transport of grains; (C) pebbly sandstone with well-rounded quartz pebbles; (D) cosets of trough cross-stratifications corresponding to fluvial conditions of sedimentation of the Arai Formation.

Figure 11: Arai Formation paleocurrents measurement numbers (n) and associated azimuth (vector of paleoflow mean direction): A,B,C from Pinheiro et al. (1990Pinheiro S.S., Reis N.J. , Costi H.T. 1990. Programa Levantamentos Geológicos Básicos do Brasil. Geologia da Região de Caburaí, Nordeste de Roraima. Escala 1:100.000. Estado de Roraima. DNPM/CPRM. Superintendência Regional de Manaus, 1v., il. 91p.); D,E from Keats (1973Keats W. 1973. The Roraima Formation Project. 1971-1973 Final Report. Geological Surveys and Mines Dept., Georgetown, Guyana, Report WK 1/73. 68p.) and F,G from Ghosh (1981Ghosh S.K. 1981. Geology of the Roraima Group and its Implications. In: Simposium Amazonico, 1., Puerto Ayacucho, Venezuela. Memoria…, p.22-30.).

Figure 12: Cross Hill, Uiramutã Village. (A) West of Cross Hill including the four formations of the Suapi Group named Uiramutã, Verde, Pauré and Cuquenán (bottom to top and left to right); (B) fine-laminated reddish siltstones of the Verde Formation; (C) arkosic sandstones to pebbly sandstones with trough cross-stratifications present within the Pauré Formation.

Figure 13: Aerial view of the Guyanese side where broad hills predominate and altered pyroclasts of the Uaimapué Formation have a characteristic pinkish colour.

Figure 14: Aerial view of the natural border represented by the Maú-Ireng River between Brazil and Guyana. The area displayed is of the Uaimapué Formation composed mainly of reddish tuffaceous rocks. The aerial photo was taken a few meters south of Orinduik Falls.

Figure 15: Orinduik Falls, Maú/Ireng River at the border between Brazil and Guyana.

Figure 16: View of the Cuquenán and Mount Roraima Tepuy (from left to right). Both mountains are composed of sedimentary rocks of the Matauí Formation along the triple border junction between Venezuela, Brazil and Guyana.

Table 1: Stratigraphy of Roraima Supergroup proposed by Reis and Yánez (2001Reis N.J. , Yánez G. 2001. O Supergrupo Roraima ao longo da Faixa Fronteiriça entre Brasil e Venezuela (Santa Elena de Uairén - Monte Roraima). In: Reis N.J. , Monteiro M.A.S. (Eds.). Contribuições à Geologia da Amazônia. Manaus: SBG/Núcleo Norte. v.2. p.115-147.) along the Brazil - Venezuela border and it extension to Guyana. Compilation of ages of the volcanic rocks underlying the Roraima Supergroup along the border between Brazil and Guyana (Surumu Group and Iwokrama Formation), of a pyroclastic rock unit of the Uaimapué Formation in Brazil and of intruding sills of the Avanavero Dolerite in Brazil.

References: ¹Santos et al. (2003Santos J.O.S. , Potter P.E., Reis N.J. , Hartmann L.A, Fletcher I. R., McNaughton N.J. 2003. Age, source and Regional Stratigraphy of the Roraima Supergroup and Roraima-like Sequences in Northern South América, based on U-Pb Geochronology. Geological Society of America Bulletin, 115(3):331-348.); ²Reis et al. (2013Reis N.J. , Teixeira W., Hamilton M.A., Bispo-Santos F., Almeida M.E., D’Agrella-Filho M.S. 2013. Avanavero Mafic Magmatism, a Late Paleoproterozoic LIP in the Guiana Shield, Amazonian Craton: U-Pb ID-TIMS baddeleyite, Geochemical and Paleomagnetic Evidence. Lithos, 174:175-195.); ³Nadeau (not publ.); ⁴CPRM (2016CPRM. 2016. Programa Geologia do Brasil. Programa Cartografia da Amazônia. Geologia e Recursos Minerais da Folha Ilha de Maracá, NA.20-X-A. Escala 1:250.000. Estado de Roraima. In: Reis N.J. , Ramos M.N. (Orgs.). Superintendência Regional de Manaus. Nota Explicativa, 31p. (in press).) in press; ⁵CPRM (2010). (bd) baddeleyite; (zr) zircon

Table 2: Stratigraphy of the Roraima Supergroup in Brazil and in Venezuela through time as proposed by various authors: 1) Bouman (1959Bouman Q.C. 1959. The Roraima Formation, Northern of Territorio do Rio Branco. Belém, Petrobras/Renor, Relatório Interno 350-A. 17p.); 2) Yánez (1972Yánez G. A. 1972. Geología del Área de Santa Elena de Uairén (Mapa de Interpretación de 12.000 km2 en escala 1:250.000). In: Conferencia Geologica Inter-Guayanas, 9., Ciudad Guayana, Venezuela. Memoria… p.660-667., 1977Yánez G. A. 1977. Província Geológica de Roraima, Geología Estructural e Geomorfologia de su parte Suroriental, Venezuela. In: Congresso de Geologia, 5., Caracas, Venezuela. Memoria… p.845-854.); 3) Reid (1972Reid A.R. 1972. Stratigraphy of Type Area of the Roraima Group, Venezuela. In: Interguiana Conference Geological, 9., Georgetown, Guyana. Memoria..., p.343-353.); 4) Reis et al. (1985Reis N.J. , Pinheiro S.S. , Carvalho J.E. 1985. Subdivisão litoestratigráfica da Formação Suapi - Grupo Roraima, Território Federal de Roraima. In: Simpósio de Geologia da Amazônia, 2., Belém, Pará. Anais... SBG, p.408-420.); 5) Santos (1985Santos J.O.S. 1985. A Subdivisão Estratigráfica do Grupo Roraima. In: Simpósio de Geologia da Amazônia, 2., Belém, PA. Anais... SBG. p.421-431.); 6) Reis et al. (1988Reis N.J. , Pinheiro S.S. ; Costi H.T. , Souza Cruz C.E. 1988. A Subdivisão do Grupo Suapi no Contexto do Supergrupo Roraima, Porção Setentrional do T.F. de Roraima. In: Congresso Latino-Americano, 7., Belém, Pará. Anais... SBG, p.389-398., 1990Reis N.J. , Pinheiro S.S. , Costi H.T. , Costa J.B.S. 1990. A Cobertura Sedimentar Proterozóica Média do Supergrupo Roraima no Norte do Estado de Roraima, Brasil: Atribuições aos seus Sistemas Deposicionais e Esquema Evolutivo da sua Borda Meridional. In: Congresso Brasileiro de Geologia, 36., Natal. Anais... SBG, p.66-81.); 7) Reis and Yánez (2001Reis N.J. , Yánez G. 2001. O Supergrupo Roraima ao longo da Faixa Fronteiriça entre Brasil e Venezuela (Santa Elena de Uairén - Monte Roraima). In: Reis N.J. , Monteiro M.A.S. (Eds.). Contribuições à Geologia da Amazônia. Manaus: SBG/Núcleo Norte. v.2. p.115-147.); 8) Keats (1973Keats W. 1973. The Roraima Formation Project. 1971-1973 Final Report. Geological Surveys and Mines Dept., Georgetown, Guyana, Report WK 1/73. 68p.). The correlation between the stratigraphy of the Roraima Supergroup in Brazil and Venezuela with the unit subdivisions in Guyana are shown in the last two columns to the right (this work).

Br - Brazil; Vz - Venezuela; Gu - Guyana

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[1] *Corresponding author.