Elsevier

Geomorphology

Volume 107, Issues 3–4, 15 June 2009, Pages 300-315
Geomorphology

Evaluation of paleohydrologic models for terrestrial inverted channels: Implications for application to martian sinuous ridges

https://doi.org/10.1016/j.geomorph.2008.12.015Get rights and content

Abstract

Fluvial systems can be preserved in inverted relief on both Earth and Mars. Few studies have evaluated the applicability of various paleohydrological models to inverted fluvial systems. The first phase of this investigation focused on an extensive (spanning  12 km) inverted paleochannel system that consists of four sandstone-capped, carbonate-cemented, sinuous ridges within the Early Cretaceous Cedar Mountain Formation located southwest of Green River, Utah. Morphologic and sedimentologic observations of the exhumed paleochannels were used to evaluate multiple numerical models for reconstructing paleofluvial hydrological parameters. Another objective of the study was to determine whether aerial or orbital observations yield model results that are consistent with those constrained by field data. The models yield an envelope of plausible dominant discharge values (100–500 m3/s), reflecting the limitations of the approach, and no single model can be used to reliably estimate paleodischarge. On Mars, landforms with attributes consistent with inverted channels have been identified. In spite of differences in the formation history between these martian landforms and the terrestrial analog described here, including potential differences in cement composition and the erosional agent that was responsible for relief inversion, these numerical models can be applied (with modification) to the martian landforms and yield an envelope of plausible values for dominant discharge.

Introduction

Relief inversion is an aspect of landscape evolution on both terrestrial (Pain and Ollier, 1995) and martian (e.g., Williams and Edgett, 2005, Williams et al., 2005, Pain et al., 2007) denuded surfaces, where materials deposited in topographic lows were or became more resistant to erosion than the surrounding terrain. Exhumation of martian terrains was identified in some of the earliest orbital images (Sharp, 1973, Soderblom et al., 1973) and is now recognized as a widespread process on Mars (Malin and Edgett, 2001). Inverted topography of fluvial landforms results when differential erosion preferentially strips away the less resistant valley or channel walls, leaving the original floor as a local topographic high. (We differentiate channels, the conduit through which water flows, from the larger-scale valley.) Several processes can lead to relief inversion, including cementation of the channel floor, armoring of the channel floor by coarse grains, and infilling by a more resistant material (commonly a lava flow).

Cemented, positive-relief channels are good environments for preservation of fluvial sediments, with exposures in three dimensions and retention of many attributes of the original channel form. The preservation of these sedimentary attributes, including grain size distribution and sedimentary structures, provides a record of the fluvial conditions during active flow and is useful for evaluating paleohydrological models. In contrast, lava-capped inverted valleys are the result of lava infilling of the valley, a process that obscures sedimentary structures in plan view. A lava flow may occupy both a fluvial channel and its surrounding valley floor such that morphometric observations of the inverted topography do not necessarily reflect the channel dimensions and formative discharge.

The motivation for this investigation stems from the recent recognition that fluvial landforms on Mars have a variety of preservation states (Williams and Edgett, 2005). In addition to the negative-relief valley networks first identified in Mariner 9 images (McCauley et al., 1972), some valleys are buried (e.g., Mangold et al., 2004) and others are preserved as ridge forms and positive-relief branching networks. In this report, the nongenetic term “sinuous ridges” will be used to refer to these landforms on Mars, although other terms have been adopted in the literature including “raised curvilinear features” (RCFs) (Burr et al., 2006, Williams, 2007). Over 200 sinuous ridge sites have been identified in meter- and decameter-scale images around the martian globe, covering areas ranging from tens to hundreds of square kilometers (Pain et al., 2007, Williams, 2007). In contrast to valley networks, which are primarily found on the ancient cratered highlands, sinuous ridges are found on terrain with ages that span the entire geological history of the planet, from the Noachian to the Amazonian Periods, expanding the record of past water on Mars (Williams, 2007).

All published studies to date have interpreted martian sinuous ridges as fluvial in origin, but authors have differed on the water source. Based on their curvilinear and bifurcating appearance, continuity relationships with negative-relief valley networks, and similarity to terrestrial fluvial landforms, the sinuous ridges are interpreted to be the remnants of former fluvial channels formed by continually flowing water, now expressed in inverted relief (Moore and Howard, 2005, Williams and Edgett, 2005, Pain et al., 2007). Sedimentary structures that support this interpretation are evident in some of the martian sinuous ridges. For example, scroll bars are present in the putative deltaic deposit defined by cross-cutting sinuous ridges within Eberswalde crater (Malin and Edgett, 2003, Moore et al., 2003, Bhattacharya et al., 2005, Wood, 2006). In addition to precipitation-fed surface runoff (e.g., Moore et al., 2003, Moore and Howard, 2005), other scenarios for generating fluids have been proposed in the formation of these landforms, including impact-generated melt from ground-ice (Jerolmack et al., 2004), glacial meltwater or subglacial streams (eskers) (Howard, 1981, Kargel and Strom, 1992, Nussbaumer et al., 2003, McMenamin and McGill, 2005, Burr et al., 2006). The majority of the sinuous ridges have morphology consistent with open-channel flow, as examined in this study. Very few sinuous ridges, confined to specific regions on Mars (e.g., Argyre Planitia and Aeolis/Zephyria Plana; Kargel and Strom (1992) and Burr et al. (2008), respectively), are interpreted to be eskers primarily because they cross pre-existing topographic divides. Under this interpretation, these sinuous ridges would have formed in a closed and potentially pressured environment that is inconsistent with the terrestrial analog site investigated in this paper.

The diverse suite of sinuous ridges preserved on Mars documents a range of paleofluvial environments and attests to the complex fluvial history of the planet. The channel systems as observed today are the products of combined burial, exhumation, and degradation. Several studies (e.g., Moore et al., 2003, Fassett and Head, 2005, Irwin et al., 2005) have applied hydraulic models derived from the study of active fluvial systems on Earth to one or more of these inferred inverted martian landforms, even though few terrestrial studies have documented the applicability of such models to inverted channels. In this study, we evaluate the applicability of both empirically and theoretically derived paleohydrologic models for modern streams to cemented inverted channels based on analysis of field data for inverted paleochannels in east central Utah. Future phases of this research will investigate other agents of inverted relief in fluvial systems, including lava infilling. Results of this study can be used to assess the magnitude of fluvial activity in inferred inverted channels on Mars.

Section snippets

Study region

Multiple exhumed paleochannels are found in parts of the Colorado Plateau. Following uplift of the region in middle to late Cenozoic time, erosion, dominantly by the Colorado River and its tributaries, stripped away younger strata, revealed Late Jurassic and Early Cretaceous paleochannel sediments at several sites in east central Utah (e.g., Williams et al., 2007). The present-day arid climate has inhibited the development of thick soil horizons and pervasive vegetative cover, leaving these

Measurements

The primary objective of field work was to obtain input parameters for the paleohydrologic models (described in Section 3.2). Secondarily, the suite of field measurements was compared to data derived from aerial photographs, as an appraisal of measurements obtained from remotely sensed data. The following sections describe the methods employed in this study.

The topographic survey obtained direct measurements of the present-day width and slope of inverted channels termed “B” and “D” by Harris

Input parameters

Accurate determination of the paleohydraulic model input parameters, such as flow cross-sectional area, former energy gradients, and maximum particle size, is complicated by multiple geologic processes that have operated on the fluvial deposits since the channels were active. Here we discuss how input values were determined based on field observations. Maizels, 1983, Maizels, 1987 discusses in additional detail the sources of error and problems inherent in reconstruction of paleochannel

Discussion

The approach adopted in this study yields an envelope of discharge values, an indication of the plausible range as verified through field observations. The overall mean discharge value tended toward the maximum value in the micro approach and an intermediate value for the macro approach. When evaluating the paleohydraulics of the system, considering both approaches is desirable and important to mitigate uncertainties in each variable and take full advantage of the available data. None of the

Conclusions

Cemented paleochannel deposits, now exposed as ridge forms because of landscape inversion, preserve key attributes of the former fluvial environment. A record of the fluvial conditions during active flow is preserved, such as original channel shape (preserved in some sections), flow direction, and sediment transport capability. Paleochannel dimensions, slope, and grain size distribution can be used to estimate paleoflow conditions using paleohydraulic models. The 14 paleohydraulic models

Acknowledgements

The authors are grateful to A. Johnston (Smithsonian Institution) for technical advice, T. Chidsey (Utah Geologial Survey) and Brian S. Curie (Miami University-Ohio) for information regarding the study site, and Doug Cox for development of USAPhotoMaps. This manuscript was improved by comments of V. Baker, G. Komatsu, A. Howard and two anonymous reviewers. This research was supported by a NASA Mars Fundamental Research Grant #NNX06AB21G and a research grant from the Becker Endowment from the

References (113)

  • Al-SuwaidiA.H. et al.
  • BathurstJ.C.

    Flow resistance estimation in mountain rivers

    Journal Hydraulic Engineering, American Association of Civil Engineers

    (1985)
  • BellT.E.

    Deposition and diagenesis of the Brushy Basin Member and upper part of the Westwater Canyon Member of the Morrison Formation, San Juan Basin, New Mexico

  • BettessR.

    Flow resistance equations for gravel bed rivers

  • BhattacharyaJ.P. et al.

    Dynamic river channels suggest a long-lived Noachian crater lake on Mars

    Geophysical Research Letters

    (2005)
  • BibringJ.P. et al.

    Mars surface diversity as revealed by the OMEGA/Mars Express observations

    Science

    (2005)
  • BibringJ.P. et al.

    Global mineralogical and aqueous Mars history derived from OMEGA/Mars Express data

    Science

    (2006)
  • BrayD.I.

    Estimating average velocity in gravel-bed rivers

    Journal of the Hydraulic Division, ASCE

    (1979)
  • BridgeJ.S.
  • BurrD.M. et al.

    Multiple, distinct, (glacio?)fluvial paleochannels throughout the western Medusae Fossae Formation, Mars

  • Burr, D.M., Enga, M.T., Williams, R.M.E., Zimbelman, J.R., Howard, A.D., Brennand, T.A., 2008. Pervasive aqueous...
  • CarlstonC.W.

    The relation of free meander geometry to stream discharge and its geomorphic implications

    American Journal of Science

    (1965)
  • ChurchM.

    Palaeohydrological reconstructions from a Holocene valley fill

    Fluvial Sedimentology

    (1978)
  • ChurchM.

    Channel morphology and topology

  • ColbyB.R.

    Discharge of sands and mean–velocity relationships in sand-bed streams

  • ColbyB.R.

    Scour and fill in sand-bed streams

  • ColebrookC.F.

    Turbulent flow in pipes, with particular reference to the transition region between smooth and rough pipe laws

    Journal Institution of Civil Engineers, London

    (1939)
  • ColebrookC.F. et al.

    Experiments with fluid friction in roughened pipes

  • CurrieB.S.

    Sequence stratigraphy of nonmarine Jurassic–Cretaceous rocks, central Cordilleran foreland-basin system

    Geological Society of America Bulletin

    (1997)
  • CurrieB.S.

    Upper Jurassic–Lower Cretaceous Morrison and Cedar Mountain Formation, NE Utah–NW Colorado: relationships between nonmarine deposition and early Cordilleran foreland-basin development

    Journal of Sedimentary Research

    (1998)
  • DavisS.W.

    Erosional history of the Colorado River through Glen and Grand Canyons

  • DoellingH.

    Tufa deposits in western Grand County

    Survey Notes—Utah Geological Survey

    (1994)
  • EthridgeF.G. et al.

    Reconstructing paleochannel morphology and flow characteristics: methodology, limitations, and assessment

  • ElderW.P. et al.

    Cretaceous paleogeography of the Colorado Plateau and adjacent areas

  • FassettC.I. et al.

    Fluvial sedimentary deposits on Mars: ancient deltas in a crater lake in the Nili Fossae region

    Geophysical Research Letters

    (2005)
  • GioiaG. et al.

    Scaling and Similarity in Rough Channel Flows

    Physical Review Letters

    (2002)
  • GriffithsG.A.

    Flow resistance in coarse gravel bed rivers, Proc

    ASCE, Journal of Hydraulic Division

    (1981)
  • HanksT.C.

    The Colorado River and the age of Glen Canyon

  • HarrisD.R.
  • HeyR.D.

    Flow resistance in gravel-bed rivers, Proc. ASCE

    Journal of Hydraulics Division

    (1979)
  • HowardA.D.

    Etched plains and braided ridges of the south polar region of Mars: features produced by basal melting of ground ice?

  • HowardA.D. et al.

    Boulder transport across the Eberswalde delta

  • IrwinR.P. et al.

    Interior channels in Martian valley networks: discharge and runoff production

    Geology

    (2005)
  • IrwinR.P. et al.

    Fluvial valley networks on Mars

  • JarrettR.D.

    Hydraulics of high gradient streams

    Journal of Hydraulic Engineers

    (1984)
  • JerolmackD.J. et al.

    A minimum time for the formation of Holden Northeast fan, Mars

    Geophysics Research Letters

    (2004)
  • JoplingA.V.

    Some procedures and techniques used in reconstructing the hydraulic parameters of a paleoflow regime

    Journal of Sedimentary Petrology

    (1966)
  • KargelJ.S. et al.

    Ancient glaciation on Mars

    Geology

    (1992)
  • KeuleganG.H.

    Laws of turbulent flow in open channels

  • KirklandJ.I. et al.

    Cretaceous dinosaurs of the Colorado Plateau

  • Cited by (0)

    View full text