A microfacies analysis of arid continental carbonates from the Cedar Mesa Sandstone Formation, Utah, USA

Ross P Pettigrew,Stuart M Clarke,Steven L Rogers

doi:10.1002/dep2.99

Abstract

AbstractArid continental environments are typically dominated by siliciclastic aeolian, alluvial and fluvial deposits. Despite their common recognition within these environments, carbonate deposits are often overlooked, yet they can provide vital insight into the depositional history, climate and tectonic controls of a sedimentary basin. This work presents a detailed microfacies analysis of the carbonates found within the Cedar Mesa Sandstone Formation of the Western USA. The Cedar Mesa Sandstone Formation is an early Permian, predominantly aeolian succession, exposed across much of the Colorado Plateau of southern Utah and northern Arizona. The formation is dominantly clastic erg deposits, that grade into a mixed carbonate/clastic sedimentary succession interbedded with carbonate and evaporitic units, interpreted to represent sabkha or sabkha‐like deposits. While many authors have worked within the aeolian dominated facies and have proposed various facies schemes for the siliciclastic components, comparatively little attention has been paid to the mixed evaporitic/clastic/carbonate aeolian‐sabkha transition zone. In this work the microfacies of the carbonates present within the Cedar Mesa Sandstone are analysed, in order to: (a) develop a record of, and interpret carbonate components, (b) propose depositional mechanisms and (c) identify evolutionary trends that stand alongside the formation's clastic depositional story. Six microfacies are presented: (MF1) Clastic Influenced Carbonate Wackestone; (MF2) Laminated Carbonate Wackestone/Packstone; (MF3) Microbial Laminated Fenestral Bindstone; (MF4) Rounded Mudclast Wackestone; (MF5) Laminated Bioclastic‐Ostracod‐Carbonate Wackestone and (MF6) Microcrystalline Quartz. The microfacies have been interpreted to document the development of carbonate interdune, lacustrine and continental sabkha environments influenced by localized fault control juxtaposed across a wetting and drying climate cycle and provide useful comparisons for other mixed evaporite/carbonate and clastic sequences.

Highlights

Introduction & Geological SettingCarbonates, less common than aeolian, alluvial and fluvial deposits, feature in many arid continental settings, and have been recognised widely within both modern and ancient (Dorney et al, 2017; Sanz et al, 1995) deposits
Carbonate deposits within arid continental basins are rarely studied in detail (Mountney & Jagger, 2004; Langford & Chan, 1988, 1989; Moutney, 2012)
The predominantly aeolian successions of the Cedar Mesa Sandstone Formation are exposed across much of the Colorado Plateau of southern Utah and northern Arizona, and they represent an early Permian, northeast-southwest trending desert system bounded by a palaeoshoreline to the northwest (Blakey, 1988; Blakey et al, 1988; Huntoon et al, 2000, Fig. 1)

Summary

Introduction

Carbonates, less common than aeolian, alluvial and fluvial deposits, feature in many arid continental settings, and have been recognised widely within both modern and ancient (Dorney et al, 2017; Sanz et al, 1995) deposits. They form through complex interactions between ground waters and soils (Spötl & Wright, 1992) within interdune or desert-lacustrine settings (Platt, 1989; Driese, 1985; Seard et al, 2013; Parrish et al, 2017), springs and tufa mounds (Dorney et al, 2017), or from marine incursions (Jordan & Mountney, 2010, 2012). In the southeast corner of present day Utah, the Cedar Mesa erg deposits grade into mixed evaporite/carbonate and clastic sediments that are interpreted as sabkha deposits of an erg-marginal transition zone (Huntoon et al, 2000; Condon, 1997: Blakey, 1988)

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