| Popis: |
New 207 such as the Serra Surucucus, Araca ´, and Neblina units, do not belong to the supergroup. Rocks of the Roraima Supergroup and post-Roraima sandstones were deposited in two separate but overlapping basins, each ;1,200,000 km2 in area. The Roraima Su- pergroup represents fill in a foreland basin that was derived mostly from the Trans- Amazon orogenic belt to the north and northeast, whereas the fill in the post- Roraima Neblina successor foreland basin was derived from both the Trans-Amazon and Tapajos-Parima orogenic belts to the east and northeast. Although most of both basins are largely flat lying or gently de- formed, some of the westernmost outliers of the post-Roraima sandstones were de- formed by the far-field effects of the Sunsas (Grenvillian) orogen at 1.33 Ga (Ar-Ar in muscovite). These results are based on U-Pb deter- minations of nine samples, Ar-Ar step- heating plateau age of one muscovite sam- ple, and a complete review of many earlier Rb-Sr and K-Ar earlier dates. |
