Contrasting styles of fluvial-aeolian interaction at a downwind erg margin: Jurassic Kayenta-Navajo transition, northeastern Arizona, USA

Abstract

Fluvial-aeolian interactions result from both short-term interplay between an ergmargin and adjacent fluvial system, and much longer-term expansion and contraction of the erg in response to climatic, tectonic or eustatic effects.Near Moenkopi, in northeastern Arizona, a zone of intertonguing characterizes the transition between the fluvial Kayenta Formation and the overlying aeolian Navajo Sandstone. Three fluvial to aeolian drying-up cycles form the largest scale interaction and represent the repeated advance of the Navajo erg across the Kayenta alluvial plain, probably in response to an increasingly arid climate. During the aeolian phase of each cycle, small-scale interactions resulted from fore-erg deposition on the alluvial plain, and fluviallyfed interdunal flooding, which both occurred during periods of erg activity.The top of each cycle marked a return to wetter climatic conditions which terminated erg activity, forming a stabilization surface. As a consequence, prograding fluvial systems were able to transgress the denuded surface, covering the area formerly occupied by the erg to form the base of the next drying-up cycle.From a hydrocarbon reservoir viewpoint, the two types of interaction have contrasting geometries. Fluvial deposits of the large-scale cycles have regionally extensive sheet-like geometries and are likely to form widespread barriers to vertical flow. Small-scale interdunal flooding is less significant and forms ribbon-like baffles to flow which extend roughly parallel to the strike of the aeolian cross-strata. The key to differentiating each type of interaction lies in determining whether the fluvial syste coexisted with the active erg, or prograded as a result of erg stabilization.

A classification scheme for fluvial–aeolian system interaction in desert-margin settings

“…Together these factors govern the aeolian sediment state of the system (e.g., McKee et al, 1967;Herries, 1993;Kocuerk, 1999;Kocurek and Lancaster, 1999;Robinson et al, 2007). Short-term or long-term shifts in the positions and form of the boundaries between aeolian and fluvial systems are controlled by the competition between fluvial flood events and sites of aeolian dune construction, which are subject to the external (allogenic) control of climate change (cf.…”

Facies architecture and heterogeneity of the fluvial–aeolian reservoirs of the Sergi formation (Upper Jurassic), Recôncavo Basin, NE Brazil

“…Interbedded massive, horizontally to low-angle laminated and cross-stratified sandstones suggest oscillation between high-and low-flow conditions during channel filling. The occurrences of many internal erosional planes in the sand bodies suggest that channels were filled by multiple floods events (Herries, 1993;George and Berry, 1993). Fine sediments (lithofacies Sr and Fm) at the top of each cycle are common products of decreasing flow velocity or channel abandonment (Smith et al, 1989;Miall, 1996).…”

“…Horizontal strata like these can be ascribed to two diverse depositional settings: (i) interdune areas, located between aeolian dunes and developed under metasaturated depositional conditions (e.g. Herries, 1993;Mountney and Thompson, 2002;Mountney and Russel, 2009;Ulicny, 2004); and (ii) aeolian sand sheets, formed as consequence of limited wind energy or sand availability precluding aeolian dune formation (e.g. Trewin, 1993;Veiga et al, 2002;Biswas, 2005).…”

“…The aeolian horizontal strata of the Sergi Formation make up to 2 m-thick packages but are not associated with intercalated high-angle cross-bedded aeolian dune deposits. Therefore, it is unlikely that they represent interdune deposits, and the aeolian sand sheet hypothesis is favored in this case (Clemmensen and Abrahamsen, 1983;Clemmensen and Dam, 1993;Herries, 1993;Veiga et al, 2002;Biswas, 2005;Scherer and Lavina, 2005;Dias and Scherer, 2008).…”

Alluvial-eolian interaction in a Cambrian rift margin: the Pedra das Torrinhas and Pedra Pintada formations (Guaritas Group, RS)

“…Langford 1989, Langford and Chan 1989, Stanistreet and Stollhofen 2002, Paim and Scherer 2007, with descriptions of the resulting depositional architecture (e.g. Herries 1993, Fischer et al 2007). The quality of the here presented expositions enables a 3D architectural analysis, making it possible to document the spatial variation of the porosity of sedimentary rocks at several scales.…”