Tidal sedimentation under high-energy influence: physical and biological interactions.

PAN, JERONIMO; CUADRADO D. G.; EDUARDO A. GOMEZ; RANIOLO, L. A.; MAISANO, L.

Puerto Madryn

Conferencia; 9th International Conference on Tidal Sedimentology; 2015

IAS

AbstractThe recognition of signatures in the rock record and the interpretation of associated sedimentary processes is one of the major challenges facing tidal sedimentologists. Detailed observations and quantitative estimates of parameters in modern environments, including time series data, facilitate the comprehension and understanding of the processes lying behind tidalites. In addition, the preser­ vation potential of sedimentary structures plays an important role in the interpretation of the sedi­ mentary rock record. The present investigation deals with tidal processes on a supratidal pan, the inundation of which is primarily controlled by the local wave climate and atmospheric conditions (prevailing direction, duration and intensity of winds) acting in conjunction with specific geomorphological characteristi­ cs of the environment. Of paramount importance is the fact that the supratidal pan under considera­ tion is colonized by microorganisms forming thick microbial mats which generate a smooth and elastic surface, thereby preserving particular sedimentary structures currently experiencing early diagenesis. Based on the interplay between moisture variation and event-controlled high tidal-current shear stress, deformed microbial structures have recently been documented and described at Paso Seco, Argentina (S40º39´-W62º14´; Cuadrado et al., 2015). The zone constitutes a remnant tidal channel/tidal flat which is today choked by a sand spit formed by NE longshore sediment transport. Through successive campaigns, the effects of seawater inundation of the study area during high-energy events were recorded. Figure 1. Study area. a) The area with microbial mat-colonized sediments is delineated. HS is the Hobo station location. b) Detail of the incursion of sea water across the sand spit zone, through a runnel structure. To detect water-level fluctuations in the groundwater and by tidal inundation of the pan, a HOBO water level logger (model U20) was placed 20 cm below the pan surface. The sensor recor­ ded water level and temperature every 10 min over a 5-month period from early autumn to mi­ d-winter 2015. The weather model Global Forecast System (GFS) was used to correlate the contem­ I N D E X 128