Sedimentary cycles and facies architecture of aeolian–fluvial strata of the Upper Jurassic Guará Formation, southern Brazil
Version of Record online: 17 NOV 2005
Volume 52, Issue 6, pages 1323–1341, December 2005
How to Cite
SCHERER, C. M. S. and LAVINA, E. L. C. (2005), Sedimentary cycles and facies architecture of aeolian–fluvial strata of the Upper Jurassic Guará Formation, southern Brazil. Sedimentology, 52: 1323–1341. doi: 10.1111/j.1365-3091.2005.00746.x
- Issue online: 17 NOV 2005
- Version of Record online: 17 NOV 2005
- Manuscript received 16 April 2004; revision accepted 1 September 2005.
- Fluvial–aeolian interaction;
- sedimentary cycles;
- southern Paraná Basin;
- Upper Jurassic
The Upper Jurassic Guará Formation comprises an 80–200 m thick continental succession exposed in the western portion of the Rio Grande do Sul State (Brazil). It comprises four distinct facies associations: (i) simple to locally composite crescentic aeolian dune sets, (ii) aeolian sand sheets, (iii) distal floodflows, and (iv) fluvial channels. The vertical stacking of the facies associations defines several 5–14 m thick wetting-upward cycles. Each cycle starts with aeolian dune sets followed by aeolian sand sheets deposits and culminating in either fluvial channels or distal flood strata. Within some cycles, aeolian sand sheets are absent and fluvial deposits rest directly above aeolian dune facies. The transitions from one facies association to another are abrupt and marked by erosive surfaces that delineate distinct episodes of sediment accumulation. The origin of both the wetting-upward cycles and the erosive surfaces was controlled by the ground-water table level, dry sand availability and aeolian and fluvial sediment transport capacity variations, related to climatic fluctuations between relatively arid and humid conditions. Preservation of the fluvial–aeolian deposits reflects an overall relative water table rise driven by subsidence.