Cerro do Jarau - Hypervelocity Impact Crater

Alternate Names Cerro Jarau
Coordinates 30° 11' 60" S; 56° 31' 48" W
Notes
  1. 25 km N of the town Quarai in the western portion of the Rio Grande do Sul State, near the border of Uruguay (Crosta et al., 2010).
Country Brazil
Region Rio Grande do Sul
Date Confirmed 2018
Notes
  1. Confirmed by quartz grains within a breccia that feature PF, feather features, and PDF gathered from the central part of the structure (Reimold et al., 2018).
Buried? No
Notes
  1. Central elevated peaks from the presumed central uplift are found on an otherwise flat terrain (Reimold et al., 2018).
Drilled? No
Target Type Mixed
Notes
  1. Formed on basaltic flows of the Cretaceous Serra Geral Formation and in sandstones of the Botucatu and Guara Formations (Reimold et al., 2018). The underlying Guará and Botucatu sedimentary formations are uplifted through the Serra Geral basalts. The thickness of Botucatu is given as 0-0.1km across the basin; that of Guará is given as 0.06-0.12km (Giacomini et al., 2017). A drill core (JC457) was made ~1km south of the structure. See Fig. 10 in (Hartmann and Cerva-Alves, 2021)
Sub-Type Basalt, Sandstone
Apparent Crater Diameter (km) 13.5 km
Age (Ma) ≤135
Notes :
  1. A rough age of ≤135 Ma is estimated using stratigraphic constraints and 40Ar/39Ar geochronology (Crósta et al., 2019) (Schmieder and Kring, 2020). Additional age constraints: The youngest stratigraphic unit involved in the impact is the basalts of the Serra Geral Formation. The age of basalts determined by the 40Ar/39Ar method is 132.4 ± 1.1 Ma. This regional age for the Serra Geral Formation provides an approximate maximum age for the impact (Crosta et al., 2010).

Method :
  1. 40Ar/39Ar
Impactor Type Unknown

Advanced Data Fields

Notes

Local Language
N/A
Erosion
5
  1. Rim and ejecta are not preserved and structure suggests significant erosion could be possible (Reimold et al., 2018).
Final Rim Diameter
Unknown
Apparent Rim Diameter
13.5 km
  1. (Reimold et al., 2018)
Rim Reliability Index
2
  1. There is a 4 km wide terrain that is thought to represent a slightly off-centre central uplift, which has peaks rising ~200 m above the surrounding terrain along the northern edge of the central uplift, called the Jarau Hills (Reimold et al., 2018).
Crater Morphology
Complex
Central Uplift Diameter
4 km
Central Uplift Height
200 m
Uplift Reliability Index
2
Structural Uplift
Unknown
Thickness of Seds
≤0.220km
Target Age
Mesozoic
Marine
No
Impactor Type
Unknown
Other Shock Metamorphism
Feather features
  1. Feather features identified in quartz grains from 12 samples (Reimold et al., 2018).
Shatter Cones
No
Planar Fractures
Yes
  1. PFs were found in quartz grains from 19 samples with some displaying multiple sets (Reimold et al., 2018).
Planar Deformation Features
Yes
  1. PDFs were found in quartz grains from 8 samples. Most quartz grains have single sets of PDFs with two or three sets being more rare (Reimold et al., 2018).
Diaplectic Glass
No
Coesite
No
Stisovite
No
Crater Fill
LB
  1. Monomict and polymict breccias identified within the crater. At least one type of breccia is clearly volcanic in origin. Other breccias include monomict basalt breccia, monomict sandstone breccia, and a polymict lithic breccia (Reimold et al., 2018). Possibly melt-bearing breccias, but unclear as the possible melt phases are altered (Crosta et al., 2010) (Reimold et al., 2019).
Proximal Ejecta
Unknown
Distal Ejecta
Unknown
Dykes
Unknown
Volume of Melt
Unknown
Depth of Melting
Unknown

References

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Alvaro P Crósta, F S Lourenço, G H Priebe (2010) Cerro do Jarau, Rio Grande do Sul: A possible new impact structure in southern Brazil, Large Meteorite Impacts and Planetary Evolution IV 465, Roger L Gibson, Wolf Uwe Reimold (ed.), p. 0, Geological Society of America, url, doi:10.1130/2010.2465(12)

R P Philipp, S B A Rolim, C A Sommer, C R de Souza Filho, N A Lisboa (2010) The impact structure of the Cerro do Jarau, Quaraí, RS, southern Brazil [in Portuguese], Revista Brasileira de Geociências 40(4), p. 468-483

B B Giacomini, E P Leite, Alvaro P Crósta (2017) 3D gravimetric investigation of the Cerro do Jarau structure, Rio Grande do Sul, Brazil, Meteoritics & Planetary Science 52(4), url, doi:10.1111/maps.12813

Alvaro P Crósta, W U Reimold, M A R Vasconcelos (2019) Cerro do Jarau and São Miguel do Tapuio: Two newly confirmed, large impact structures in Brazil, 50th Lunar and Planetary Science Conference, p. Abstract 3042, Lunar and Planetary Science Conference, Houston, TX, doi:10.1016/j.chemer

W U Reimold, Alvaro P Crósta, M Hasch, A Kowitz, N Hauser, J P Sanchez, L S A Simões, G J de Oliveira, P T Zaag (2019) Shock deformation confirms the impact origin for the Cerro do Jarau, Rio Grande do Sul, Brazil, structure, Meteoritics & Planetary Science 54(10), p. 2384-2397, University of Arkansas, doi:10.1111/maps.13233