Tidal circulation in an Early Permian epicontinental sea: Evidence of an amphidromic system

In epicontinental seas, as well as in oceans, amphidromic systems control tidal movement, acting on coastal dynamics and, therefore, influencing the depositional record. Inland seas were common in Pangea during the Permian. However, estimating the conditions that governed the tide in these seas is highly complex. Although Permian marine deposits are well documented on a regional scale, the tidal behavior in the epicontinental sea has not been analyzed yet. In this work, we present a theoretical perspective on the behavior of fides in the epicontinental sea of the Parana Basin during the Early Permian (Guata Sea), covering an area of similar to 1200,000 km(2). Mathematical models were applied to test the existence of amphidromic points in the basin (determined from the Rossby radius of deformation) as well as to verify the possibility of resonance. Since paleodepth is unknown and the basin tectonism is still under discussion, an estimated bathyrnetry from 20 to 500 m was used to cover even some unlikely scenarios. We also tested, using mathematical models, the amplification of the tide inside two paleovalleys. The obtained results were compared to Hudson Bay, considered here to be a modern analog of the Guata Sea. According to the paleogeography, paleolatitude (Southern Hemisphere), and depositional records, the Guata Sea had clockwise-rotation amphidromic systems. However, resonant effects may also have affected circulation, especially at sea depth below 100 m. In the simulated scenarios, the tide amplification in both valleys was variable but concentrated between micro to mesotidal amplitudes. This study presents the first contribution to the understanding of the tidal behavior of the Early Permian epicontinental sea of the Parana Basin in the basinal context of the Gondwanan paleocontinent. Recognition of amphidromic circulation in an inland sea is important because it may help to explain the general behavior of tidal deposits recorded in the basin, which were built and reworked under the influence of this system.