Downstream-migrating fluvial point bars in the rock record

A 3D forward stratigraphic model of fluvial meander-bend evolution for prediction of point-bar lithofacies architecture

“…Upstream-bar deposits of the expansional point bar, by comparison, are for the most part well preserved, especially for higher sinuosity meanderbend deposits that occur further away from the axis of the channel belt. This is consistent with field observations reporting that translating point bars exhibit systematic erosion and sediment bypass (Ghinassi and Ielpi, 2015;Ghinassi et al, 2016;Ghinassi et al, 2014;Ielpi and Ghinassi, 2014;Smith et al, 2011;Smith et al, 2009). …”

“…11B & Fig. 12B) from the earlier outcrop-based studies (Ghinassi and Ielpi, 2015;Ghinassi et al, 2016;Ielpi and Ghinassi, 2014). The Lateral accretion beds dip towards the abandoned channel fill at 5 to 15 (average is 10).…”

“…Previous studies have demonstrated how counter-point bars may develop when the apex of a meander bend migrates in the down-valley direction, and associated bar forms undertake growth via downstream translation (Burge and Smith, 2009;Ghinassi and Ielpi, 2015;Ghinassi et al, 2016;Jackson, 1976;Nicoll and Hickin, 2010). Notably, this is known to occur in response to the following situations: (1) confinement of a fluvial system within a valley (Ghinassi and Ielpi, 2015); (2) confinement by the presence of deposits that are themselves resistant to erosion, such as mud-prone abandoned channel fills (Labrecque et al, 2011;Smith et al, 2009); and (3) confinement or redirection of a fluvial path by the action of local tectonics .…”

“…Recently, a depositional model has been proposed that establishes a linkage between bedding geometries, 3D facies distribution, and meander-bend transformation behaviours (Ghinassi and Ielpi, 2015;Ghinassi et al, 2016). The exhumed meander plain of the Scalby Formation comprises two storeys of meander-belt deposits as the fill of a valley system (Ielpi and Ghinassi, 2014, Fig.…”

“…Mud drapes in both examples are limited to the top of inclined bar surfaces ( Fig. 11 and 12), akin to field observations in the Scalby Formation (Ghinassi et al, 2016;Ghinassi et al, 2014;Ielpi and Ghinassi, 2014). (dark blue to dark red) scheme is used to differentiate meander positions at different times.…”