Preservation of autogenic processes and allogenic forcings within set-scale aeolian architecture II: the scour-and-fill dominated Jurassic Page Sandstone, Arizona, USA

Abstract

The stratigraphic architecture of aeolian sandstones is thought to record signals originating from both autogenic dune behavior and allogenic environmental boundary conditions within which the dune field evolves. Mapping of outcrop-scale surfaces and sets of cross-strata between these surfaces for the Jurassic Page Sandstone near Page, Arizona, USA, demonstrates that the stratigraphic signature of autogenic behavior is captured by variable scour depths and subsequent fillings, whereas the dominant signatures of allogenic boundary conditions are associated with antecedent surface topography and variable water-table elevations. At the study area, the Page Sandstone is ~ 60 m thick and is separated from the underlying Navajo Sandstone by the J-2 regional unconformity with meters of relief. Thin, climbing sets of cross-strata of the basal Page representing early dune-field accumulations fill J-2 depressions. In contrast, the overlying lower and middle Page consist of cross-strata that are one to a few meters thick, and packaged between outcrop-scale bounding surfaces. These bounding surfaces have been previously correlated to high stand deposits of the adjacent Carmel sea and at this site possess meters of erosional relief produced by dune scour. Notably absent within packages of cross-strata bounded by these outcrop-scale surfaces are strata of early dune-field accumulations, any interdune deposits, and climbing-dune strata. Instead, these packages preserve a scour-and-fill architecture created by large migrating dunes migrating within a dry, mature, dune field undergoing negligible bed aggradation. Any record of early phases of dune-field construction for the lower and middle Page are interpreted to have been cannibalized by the deepest scours of later, large dunes. Interpretations are independently supported by the relatively large coefficients of variation in lower and middle Page set thicknesses, which are consistent with set production by successive deepest trough scours, and the relatively low coefficient of variation for the depression-filling basal Page sets consistent with a significant component of bed aggradation. Numerical modeling presented here and more completely in the companion paper demonstrates how this cannibalization of early-phase stratigraphy is an expected outcome of autogenic dune-growth processes, and that early-phase strata can be preserved within antecedent depressions. Relative rise of the inland water table from basin subsidence and Carmel sea level forced preservation of multiple stacked packages composed of scour-and-fill architecture. Without these allogenic forcings, the Page would be little more than an erosional surface.

The Effect of Remote Sensing Resolution Limits on Aeolian Sandstone Measurements and the Reconstruction of Ancient Dune Fields on Mars: Numerical Experiment Using the Page Sandstone, Earth

“…The distributions of cross‐set thicknesses are characterized using statistical moments (mean, standard deviation, and products thereof), distribution shapes, and the number of detected sets. The ancient environment and dune‐field dynamics recorded by the Page Sandstone are well characterized (Cardenas et al, ; Swanson et al, ), and we compare these true characterizations to reinterpretations based on the experimental, resolution‐limited distributions. To judge the significance of these altered interpretations, we compare the experimental results to data from the Jurassic Entrada Sandstone, which represents an opposite end‐member wet dune‐field accumulation to the dry Page dune fields.…”

“…The thickness distributions of aeolian cross sets are among the easiest stratigraphic data to collect, and the shape of the distribution, as well as its statistical moments, records the aggradation, migration, and the size of dunes in a field (Bridge, ; Bridge & Best, ; Cardenas et al, ; Jerolmack & Mohrig, ; Paola & Borgman, ; Rubin & Hunter, ; Swanson et al, ). Wind is the dominant driver of sediment transport on modern Mars (Ewing et al, ; Fenton & Hayward, ; Silvestro et al, ; Silvestro et al, ; Chojnacki et al, ; Day & Kocurek, ; Lapotre et al, ; Cornwall et al, and Cornwall et al, ; Chojnacki et al, ) and has likely been significant throughout the planet's history (e.g., Anderson et al, ; Banham et al, ; Day & Catling, ; Day & Catling, ; Grotzinger et al, ; Kite et al, ; Lewis et al, ; Lewis et al, ; Milliken et al, ).…”

“…Wind is the dominant driver of sediment transport on modern Mars (Ewing et al, ; Fenton & Hayward, ; Silvestro et al, ; Silvestro et al, ; Chojnacki et al, ; Day & Kocurek, ; Lapotre et al, ; Cornwall et al, and Cornwall et al, ; Chojnacki et al, ) and has likely been significant throughout the planet's history (e.g., Anderson et al, ; Banham et al, ; Day & Catling, ; Day & Catling, ; Grotzinger et al, ; Kite et al, ; Lewis et al, ; Lewis et al, ; Milliken et al, ). On Earth, the aeolian rock record dates back at least as far as the Archean (3.2 Ga, Rodríguez‐López et al, ) and often records complex interactions of dunes with changing winds, topography, groundwater, tectonics, other dunes, and even life (e.g., Blakey et al, ; Brothers et al, ; Cardenas et al, ; Day & Kocurek, ; Havholm et al, ; Kocurek & Day, ; Loope, ). Therefore, aeolian strata are likely to provide a rich source of information about conditions at the ancient surface of Mars.…”

“…Therefore, aeolian strata are likely to provide a rich source of information about conditions at the ancient surface of Mars. This information is encoded particularly well into cross‐set thicknesses (Cardenas et al, ; Jerolmack & Mohrig, ; Paola & Borgman, ; Swanson et al, ). Aeolian cross sets are observable on Mars from remote sensing images and digital elevation models (DEMs; e.g., Milliken et al, ; Anderson et al, ; Day & Catling, ), but we hypothesize that resolution limits could lead to remotely measured thickness distributions that are not representative of the true distribution.…”

“…Here we perform a numerical experiment using a field‐acquired distribution of aeolian cross‐set thicknesses from the Jurassic middle Page Sandstone, Arizona, USA (Cardenas et al, ) to determine how changes in satellite resolution affect the interpretation of the dune field. The detectability of a set is based on its thickness, outcrop dip, the size of a remote sensing image pixel, and the number of pixels needed to identify a unique set of cross strata.…”