Effect of Holocene sediment redistributions on the relative sea level at present in the Ayeyarwady delta (aka Irrawaddy delta, Myanmar)
Résumé
<p>Under high seasonal monsoon rainfall and active tectonics, the Ayeyarwady delta is a large delta plain characterized by a high sediment supply. Also, the Ayeyarwady river, together with the Sittaung, and the Salween Rivers are bringing ~600 Mt/yr of sediments to the Andaman Sea through the Gulf of Martaban. A recent research effort have allowed characterizing the sedimentation at present and since the mid-Holocene. We here propose to integrate these published observations in a stratigraphic reconstruction and to determine by numerical modelling how much these Holocene massive sediment transfers play on coastal subsidence and relative sea level at present.</p><p>The present average sedimentation rate at the front of Ayeyarwady delta is ~10 cm/yr and the delta may be divided in two sectors: an eastern embayed sector and a western open coast sector. During the mid-Holocene, the aerial part of the delta have experimented fast progradation rate, reaching prograding rate of ~ 30 m/yr. When applying this sedimentation pattern on a preliminary (radial) viscoelastic Earth model, we show that sediment isostasy plays on the regional coastal dynamics and subsidence at present. In addition, the Ayeyarwady delta lies in a complex tectonic setting, bounded to the west by the Indo-Burman collision zone, and to the east by the sub-vertical dextral Sagaing Fault. We are integrating this tectonic setting in an earth model that allows lateral vertical discontinuity for exploring how much this significantly changes the modelling results.</p>