Abstract The Ferron Sandstone has, at least by North American standards, a long and rich history of study. Early interest in the Ferron was based on the fact that it contains substantial amounts of mineable coal, the presence of which was noted in the geological literature as early as 1874. A comprehensive documentation of the many coal seams of the Ferron was published in 1916. Several studies published in the late 1800s and early 1900s established basic correlations between the Ferron outcrops in Castle Valley and equivalent strata in other areas. Initial correlations were done entirely on the basis of similarity of sections — by means of what is commonly called “jump correlation.” This approach led to some errors that were subsequently corrected as the role of biostratigraphy in stratigraphic correlation became increasingly important. Early attempts to interpret the paleogeographic setting of the Ferron led to interesting but erroneous results. A model of Ferron deposition published in the 1920s evoked southward transport of clastics to form a large, elongated sand-rich body or “plume” centered on Castle Valley. The interpretation was incorrect, stemming from a miscorrelation between Castle Valley and scattered outcrops on the western side of the Wasatch Plateau, but it heralded a theme that would be recurrent in the interpretation of the Ferron. Discovery of a significant accumulation of natural gas in the Ferron Sandstone at Clear Creek field on the Wasatch Plateau in 1951 accelerated the pace of Ferron study. The Ferron was described in much greater detail, but a correct interpretation of Ferron paleogeography remained elusive. The concept that Ferron strata were deposited by prograding deltas and on adjacent strand plains became firmly established in the 1970s and was substantiated in the literature by well documented sedimentological data. Cyclicity was recognized and the issue of whether the cycles resulted from auto- or allocylic processes was raised. The basic stratigraphic framework of the Ferron, as we know it today, was constructed in the late 1970s and early 1980s. Recent studies have addressed the details and the numerous Ferron studies completed during the last 20 years, taken in their entirety, represent one of the most detailed stratigraphic and architectural frameworks available for any clastic unit in the world. Many recent studies make use of the detailed stratigraphic framework to focus on the petroleum reservoir properties of the various facies recognized in the Ferron, which provides a wealth of well exposed and well understood analogs for petroleum reservoirs elsewhere. At the same time, the Ferron has become an important producer of coalbed methane from the northern part of Castle Valley.

Abstract The Upper Cretaceous Ferron Sandstone represents a spectrum of depositional environments and facies spanning offshore marine to alluvial plain. Because they are very well exposed, are readily accessible, and have been extensively studied, these deposits serve as excellent analogs for many oil and gas reservoirs. Sediment was delivered to the Ferron depositional system by eastward- to northward-flowing rivers represented by sandy channelbelts. The rivers were generally meandering, although some were lower-sinuosity streams. Flood basins adjacent to the channelbelts accumulated predominantly muddy sediment, sandy crevasse-splay deposits, and, locally, peat. Peat accumulated in belts that roughly correspond to the lower part of the coastal plain and generally paralleled the shoreline. The geometries of individual, thick bodies of coal vary greatly. The dynamics of peat accumulation was controlled primarily by the rate of relative sea level rise. The balance between sediment supply and wave energy was such that most Ferron shorelines were characterized by wave-dominated, cuspate deltas that graded laterally into strandplains. During the early part of Ferron deposition, however, the supply of sediment was great enough that fluvial processes predominated locally. Lobate deltas with numerous distributaries and interdistributary bays were well represented. Shoreface and delta-front deposits graded seaward into offshore marine mud. Sandy Ferron shoreline strata interfinger extensively with marine shale. Elongated sand bodies or sand plumes accumulated on a shallow-shelf area that lay east and northeast of the Ferron shoreline during early Ferron deposition. Barrier islands developed during transgressions and are preserved, along with the lagoons that lay landward of them, at the “turnaround” points where episodes of transgression ended and shoreface progradation began. Landward pinchouts of the shoreface sandstone bodies are a key element for deciphering the transgressive-regressive history of the Ferron Sandstone. Tidal inlets and associated flood-tidal deltas are present locally in the vicinities of the landward pinchouts.

Abstract The Ferron Sandstone Member of the Mancos Shale is divided informally into upper and lower units. The upper Ferron has been divided by earlier workers into seven or eight delta-front units. These units correspond to parasequence sets. We suggest one additional delta-front or parasequence set, bringing the total to nine for the upper Ferron. The opportunity to study many of these stratal units in detail on outcrop has led to the further division into numerous parasequences. These parasequences often contain distinct, mappable genetically related packages of beds which are clearly not bounded by marine-flooding surfaces and have hence been labeled bedsets. Nineteen parasequences and four bedsets are named and described along with several undivided parasequence sets. The landward and seaward pinchouts of the nearshore marine facies of most of these units are mapped, enhancing our ability to predict geometries of associated reservoir facies. Parasequences tend to follow an evolution of delta types from initial regression to maximum regression. This evolution begins with a wave-dominated shoreline, passing through a transitional wave-modified shoreline, and typically ending with a fluvial-dominated shoreline. Parasequences in seaward-stepping parasequence sets have an average dip length of nearshore marine facies of 4.3 mi (6.9 km) and average maximum thickness of 55 ft (17 m). Although less detailed information was gathered on the aggradational parasequences, their average dip length of nearshore marine facies is 6 mi (10 km) and average maximum thickness of 56 ft (17 m). The best reservoir facies are found in the wave-dominated deltas and distributary channels. Wave dominated delta facies are consistently found in the initial regression of each parasequence, and range in shoreline strike orientation from N60W to N5E. Ambiguities in the definitions of sequence stratigraphic units and differing application of those definitions have lead to a variety of stratigraphic schemes from different workers on the same Ferron outcrops.

Abstract The Ferron Sandstone of east-central Utah has world-class outcrops of dominantly fluvial-deltaic, Turonian-Coniacian-aged strata deposited along the margins of the rapidly subsiding Cretaceous foreland basin. The Ferron consists of a series of stacked, transgressive-regressive cycles which form an eastward-thinning wedge. The Ivie Creek area contains abrupt facies changes in two of these cycles referred to as Kf-1 and Kf-2. Kf-1 consists of unusual river-dominated delta deposits that prograde southeast to northwest across the Ivie Creek area. Progradation is parallel or onshore to the regional shoreline trend. Distinctive, steeply inclined bedsets or clinoforms, defined by bounding surfaces are classified into four facies: proximal, medial, distal, and cap. Clinoform facies are based on grain size, sedimentary structures, bedding thickness, inclination angle, and stratigraphic position. These deposits accumulated on an arcuate delta lobe which was prograding into a deeper water, fully marine bay. The main delta, which we interpret to have been located to the east and northeast, created a protected embayment in the northwest part of the Ivie Creek area. The Kf-1 clinoforms represent deposition into the embayment fed by river channels from the southeast. Kf-2 is represented by wave-modified deltaic deposits that generally coarsen east to west, and consist of shoreface and distributary complex facies. These relatively clean, sand-rich deposits accumulated along a local north-south shoreline trend defined by a landward pinchout of marine shoreface facies, as opposed to the more common regional northwest-southeast shoreline trend recognized in other Ferron cycles above and below Kf-2. In the western part of the Ivie Creek area, eastto northeast-flowing distributary channels deposited large amounts of sand in north-south-trending distributary-mouth bars. Shallow- to moderate-depth marine conditions existed in the eastern part of the area. An uncommon transition from shoreface, to bay, to coastal plain/swamp occurred during the late stage of Kf-2 deposition. As a reservoir analog, the Ferron Sandstone in the Ivie Creek area displays variations in sedimentary structures and lithofacies that influence both its compartmentalization and permeability. Bounding layers like those observed on outcrop were identified from core and geophysical well-log data. These features can be incorporated into reservoir models and simulations for oil field development and secondary or enhanced oil recovery programs.