Ferron Stratigraphy Descriptions Part 1

Ferron Sandstone is recognized as a member of the Mancos Shale. No type section has been designated. The name is derived from the town of Ferron, Utah, but it is clear from Lupton’s work that he would have chosen the outcrops farther south, east, and south of the town of Emery, as representative of the member where it is most typically developed. The name Ferron Sandstone is presently used on outcrops around the San Rafael Swell, in the Henry Mountains basin, and beneath Castle Valley and the Wasatch Plateau. Controversy exists about whether “Ferron” or “Juana Lopez” is a more appropriate designation for thinly interbedded sandstones and shales of Ferron age on the east side of the San Rafael Swell near the town of Green River and eastward into Colorado.

The Clawson unit of the Ferron extends from the northern part of San Rafael Swell southward along its western flank, through Molen Reef, finally feathering out westward toward Muddy Canyon in the “Molen Amphitheatre.” The Clawson and overlying Washboard units of the Ferron together constitute the “lower Ferron” of Ryer and McPhillips (1983), and the lower part of the “Hyatti sequence” of Gardner (1994). They are shelf sandstones with a northern source. Lowering of sea level during middle Turonian time facilitated southward transport of very-fine and fine-grained sand onto a shoal area that marks the eastern hinge of the foredeep developed in front of the Sevier Orogenic belt. The shoal may represent a peripheral bulge. In addition to feathering out southward, both the Clawson and Washboard units lose sand content and disappear toward the west in the area stretching from the “Molen Amphitheatre” southward to Mesa Butte and westward to the “Tri-Canyon” area and “Cowboy Mesa.” A gentle structural flexure has been recognized in this area, suggesting the presence of a down-to-the-west basement fault. The fact that Cretaceous rocks were flexed but not broken by movement on the proposed fault (unlike the younger faults associated with Tertiary extension) suggests that this fault moved during Cretaceous time in response to thrust loading. The westward loss of sand in the Clawson and Washboard units suggest that it was active during lower Ferron deposition. Facies content of shoreline unit: shelf sand body.

The Washboard unit extends from the northern part of San Rafael Swell southward to Mesa Butte, slightly farther than does the underlying Clawson unit. Same origin as Clawson unit; same comments apply. Facies content of shoreline unit: shelf sand body.

The type section of the Last Chance unit of the Ferron is at Last Chance Creek, where the shoreline unit, together with overlying Kf-1-Ls, forms vertical cliffs approximately 200 feet high. Kf-Last Chance displays inclined bedsets that appear to onlap, or possibly downlap against a surface that may represent a paleotopographic high, resulting in very rapid seaward thinning to a feather edge. The high may represent the upthrown side of a down-to-the-west fault that was active during Ferron deposition. (A problem with this interpretation is that the thick section represented by Kf-LC can be mapped as having a northwest-southeast trend based on limited subsurface data, whereas faults that formed along the eastern hinge of the foredeep would be expected to have a north-south orientation). No contemporaneous channel deposits have yet been identified. Kf-Last Chance corresponds to the upper part of the “Hyatti sequence” of Gardner (1994). Type section: Limestone Cliffs at Last Chance, NW1/4 section 9, T. 25 S., R. 5 E., Salt Lake Base Line. Landward limit: not known; may be covered by basalt of Fish Lake Plateau. Seaward limit: Limestone Cliffs, approximately NE1/4 section 3, T. 25 S., R. 5 E., Salt Lake Base Line. Facies content of shoreline unit: wave-modified coast, possibly strand plain.

Kf-1 extends from outcrops south of Last Chance Creek to the southeastern side of “Cowboy Mesa” in the southern part of the Coal Cliffs. Its landward limit has not been accurately defined. Seven parasequence are presently recognized. The sub-A coal zone belongs to Kf-1. Only minor amounts of coal are contained in it, most of the coal occurring in the Last Chance area. The seaward limit of coal is present at the mouth of the canyon of Quitchupah Creek.

Kf-1 Limestone Cliffs is defined in the southern part of the Limestone Cliffs, at present only on the basis of oblique air photos. (Kf-1-Ls) extends from Last Chance Creek northward into the Limestone Cliffs. It is probably the youngest parasequence of Kf-1, although relationships south of Last Chance Creek have not been worked out. Proposed type section: southern part of Limestone Cliffs, somewhere in section 3, T. 25 S., R. 5 E., Salt Lake Base Line. Landward limit: south of Last Chance Creek, position not determined. Seaward limit: Limestone Cliffs, approximately SE1/4 section 34, T. 24 S., R. 5 E., Salt Lake Base Line. Facies content of shoreline unit: not yet determined; wave-modified coast judging by photos.

Kf-1-Indian Canyon-a is defined in the southern part of Indian Canyon, where the Kf/Ktnk contact reaches the canyon bottom. Only the seaward part of (Kf-1-IC-a) is exposed in Indian Canyon. Both seaward and landward limits have been tentatively identified in the Limestone Cliffs on the basis of photomosaics and oblique air photos. Although the Limestone Cliffs exposures would constitute a better type section, Indian Canyon was chosen because of ease of access and because the relationships between units Kf-1-IC-a,b,c, and d are quite clear there. A shortcoming of using Indian Canyon as a type area for (Kf-1-IC-a) is that the unit lacks upper shoreface/foreshore facies in Indian Canyon. A thick, extensively burrowed middle shoreface indicates that it was deposited on a wave-modified coastline. The seaward feather edge can be projected from the Limestone Cliffs through the subsurface to Indian Canyon and trends generally northwestward. The top of (Kf-1-IC-a) may be cut by meanderbelts belonging to (Kf-1-IC-d) locally in the Limestone Cliffs exposures. Type section: Indian Canyon, NE1/4NW1/4 section 26, T. 24 S., R. 5 E., Salt Lake Base Line. Landward limit: Limestone Cliffs, approximately SE1/4 section 34, T. 24 S., R. 5 E., Salt Lake Base Line. Seaward limit: Indian Canyon, SW1/4SW1/4SW1/4 section 24, T. 24 S., R. 5 E., Salt Lake Base Line; Limestone Cliffs, approximately NW1/4SE1/4 section 25, T. 24 S., R. 5 E., Salt Lake Base Line. Facies content of shoreline unit: wave-modified coast, probably strand plain.

Kf-1-Indian Canyon-b is defined in Indian Canyon at the south end of the canyon and referred to as “The Wall.” Landward and seaward limits of (Kf-1-IC-b) are tentatively defined in the Limestone Cliffs utilizing photomosaics and oblique air photos. The landward pinch-out is not exposed in Indian Canyon; the seaward feather edge is poorly defined in northern part of Indian Canyon owing to similarity of facies content of (Kf-1-IC-b) and overlying (Kf-1-IC-c). The landwardmost part of the transgressive surface of erosion between these two is a remarkably steep surface, well exposed on the east side of Indian Canyon, opposite the south end of “The Wall.” Type section: Indian Canyon, east side, just beneath landward pinch-out of the overlying (Kf-1-IC-c), SW1/4SW1/4 section 24, T. 24 S., R. 5 E., Salt Lake Base Line. Landward limit: Limestone Cliffs, approximately NW1/4SE1/4 section 25, T. 24 S., R. 5 E., Salt Lake Base Line. Seaward limit: Indian Canyon, CSW1/4 section 24, T. 24 S., R. 5 E., Salt Lake Base Line; Limestone Cliffs, approximately CNE1/4 section 25, T. 24 S., R. 5 E., Salt Lake Base Line. Facies content of shoreline unit: wave-modified coast, probably strand plain.

Defined on the west side of Indian Canyon, (Kf-1-IC-c) is responsible for forming “The Wall.” It extends from south end of “The Wall” in Indian Canyon northward into Willow Springs Wash, feathering out gradually in the Coyote Basin- “Swell Point” area. Because the unit feathers out seaward so gradually, choosing an exact point on the map for its seaward limit is difficult and arbitrary. The landward pinch-out is fairly well exposed on the east side of Indian Canyon, but has been cut out by a channel on the west side. A substantial bay or lagoon existed behind the shoreline unit, as made evident by mudstones bearing oyster shells. A channel mouth or tidal inlet deposit that cuts (Kf-1-IC-c) locally very near its landward pinch-out probably connected this body of water with the sea. (Kf-1-IC-c) is very much a wave-modified unit. Its top is cut locally by meanderbelt deposits that belong to the younger Kf-1-IC-d. Type section: “The Wall” along the west side of Indian Canyon, SW1/4, SW1/4 section 24, T. 24 S., R. 5 E., Salt Lake Base Line. Landward limit: Limestone Cliffs, approximately CNE1/4 section 25, T. 24 S., R. 5 E., Salt Lake Base Line. Seaward limit: South of Coyote Basin, approximately SW1/4NE1/4 section 18, T. 24 S., R. 5 E., Salt Lake Base Line. Facies content of shoreline unit: wave-modified coast, probably strand plain.

(Kf-1-IC-d) is recognized in the North Fork of Indian Canyon and the northernmost part of “The Wall” in Indian Canyon. It is also present, though difficult to distinguish with certainty, on the cliffs east of the mouth of Indian Canyon (“Boot Point”). Although clearly definable in the field, the boundary between Kf-1-IC-c and Kf-1-IC-d is not a transgressive or “marine-flooding” surface. But the two shoreline sandstone bodies are distinct and have been given different names. (Kf-1-IC-d0 prograded toward the northwest and represents a river-dominated delta front deposited in a low-wave-energy setting. The change in depositional style marked by the contact between (Kf-1-IC-d) and underlying (Kf-1-IC-c) is the result of avulsion of a river system into the area and transformation of the wave-modified, straight coastline into a protected bay into which a delta lobe subsequently prograded. The “County Line Channel” studied so extensively by Mobil appears to belong to this unit, as determined by correlation of carbonaceous shales and a thin bed of coal within the sub-A coal zone. (Note: J. Garrison, personal communication, has come to a different conclusion on the basis of his work: that the “County Line Channel” fed (Kf-1-RC)). Type locality: mouth of the North Fork of Indian Canyon, north side, NW1/4NE1/4 section 24, T. 24 S., R. 5 E., Salt Lake Base Line. Landward limit: well defined on west wall of Indian Canyon, SE1/4NW1/4 section 24, T. 24 S., R. 5 E., Salt Lake Base Line and in North Fork of Indian Canyon, NW1/4NW1/4 section 24, T. 24 S., R. 5 E., Salt Lake Base Line. Seaward limit: “Swell Point”, SE1/4 section 8, T. 24 S., R. 6 E., Salt Lake Base Line. Facies content of shoreline unit: river-dominated delta, specifically a delta lobe that built into a bay that was well protected from fair-weather waves.

Kf-1-Rock Canyon is defined on the cliffs south of Rock Canyon area. Outcrops of Kf-1-Rock Canyon in this area are only fair, being partially covered with debris, but become better in the cliffs to east, on the south side of “Overhand Point.” (Kf-1-RC) has a well defined landward pinch-out on the south-facing cliffs east of Coyote Basin, on the south side of “Swell Point.” There, it splits the sub-A coal zone, one split of carbonaceous mudstone passing below the transgressive surface, and the other passing onto the root-penetrated top of (Kf-1-RC). A tidal channel deposit rich in oysters, some of which are in growth position, cuts (Kf-1-RC) near its pinch-out. The seaward limit of (Kf-1-RC) has not yet been determined, but it appears that it extends all the way to Ivie Creek. If so, its seaward feather edge is present near the northern end of Blue Trail Canyon, where strata of (Kf-1-Iv-a) onlap it from the north. The landward part of (Kf-1-RC) is strongly wave modified, and this may well be true for the entire unit. Type section: south side of “Swell Point”, CSE1/4 section 8, T. 24 S., T. 6 E., Salt Lake Base Line. Landward limit: south side of “Swell Point”, NW1/4SE1/4 section 8, T. 24 S., R. 6 E., Salt Lake Base Line. Facies content of shoreline unit: wave-modified coast; proximal part probably strand plain; distal part may include deltaic deposits.

Kf-1-Ivie Creek is localized in the Ivie Creek-Quitchupah Creek Canyon area. It has been referred to as Kf-1-Ivie Creek-a in our detailed analysis of the Ivie Creek case-study site. Unit (Kf-1-Iv-b) may be been dropped, however, because it probably represents no more than a phase of slow sedimentation following abandonment of the delta represented by the former (Kf-1-Iv-a). Thus, it does not warrant parasequence designation. Without the -b unit, the -a designation will be dropped. (Kf-1-IV) is characterized by distinctive, steeply-sloping clinoform surfaces in the younger of its two recognizable parts. This active deltaic deposit has an arcuate shape, having prograded toward the south at the mouth of Blue Trail Canyon, toward the west in the amphitheatre north of Ivie Creek, and toward the north in the southern part of Quitchupah Canyon. It disappears to the east, across the mouth of Quitchupah Canyon, but exactly how it does this and its relationship to (Kf-1-QC) are not yet clear. It is possible that the odd characteristics of (Kf-1-Iv) can be attributed to its location at the flexure described for the Clawson unit. If this flexure marks the hinge of the foredeep, flexure of strata caused by movement of a basement fault may have brought about the deep-water bay into which (Kf-1-Iv) prograded, the meanderbelt from which its feeder channel came having been situated on the high side of the flexure. Type section: amphitheatre north of Ivie Creek, SW1/4NE1/4 section 16, T. 23 S., R. 6 E., Salt Lake Base Line. Landward limit: not yet determined; relationships to strata on Cowboy Mesa remain unclear. Seaward limit: west side of Quitchupah Canyon, SW1/4SW1/4 section 16, T. 23 S., R. 6 E., Salt Lake Base Line.

Kf-1-Quitchupah Canyon is defined in Quitchupah Creek Canyon. It is best developed in the area where Kf-1 approaches and dives beneath the alluvium at the canyon floor. It may include the beds previously included in Kf-1-Ivie Creek-c. Relationships on the west side of Quitchupah remain somewhat unclear, despite a great deal of study. If more than one parasequence is ultimately distinguished, (Kf-1-QC-a) and (Kf-1-QC-b) are possible names for them. Relationships between units recognized in Quitchupah Canyon and those on Cowboy Mesa also remain unclear owing to very complicated stratigraphy. (Kf-1-QC) may be the youngest parasequence of Kf-1, in which case it includes the strata that feathers out seaward on the southeast side of “Cowboy Mesa.” Type section: Quitchupah Creek Canyon, SE1/4 section 4, T. 23 S., R. 6 E., Salt Lake Base Line. Landward limit: not presently defined. Beds of apparent shallow-marine origin exposed above (Kf-1-Iv) in the amphitheatre north of Ivie Creek (attributed earlier to (Kf-1-Iv-d)) may belong to (Kf-1-QC). Pronounced thickening is present along the walls of Quitchupah Creek Canyon.

Kf-2 is characterized by very complicated stratigraphy at the parasequence level. The transgressive surface that marks the boundary between (Kf-2-MC-a) and (Kf-2-MC-b) is extensive enough that it might be justifiable to divide Kf-2 into two parasequence sets (Kf-2-early and Kf-2-late?) utilizing this surface. The associated A-coal zone contains thick coal beds south of Willow Springs Wash and in the Quitchupah Creek Canyon area. Much of the thickness of the C-coal bed, originally assigned to Kf-3, has recently been determined to belong to the youngest part of Kf-2. The seaward limit of C-coal deposition is in the Dry Wash area, the lower split of the coal (previously referred to as A-coal) extending somewhat farther than the upper split, which is present in Kf-3. Considering the widespread distribution and substantial thickness of the main A- and C-coal seams, Kf-2 probably ranks as the most important coal-bearing parasequence set (or sets) of the Ferron. Old, abandoned mines that produced coal for local consumption are numerous and range from Willow Springs Wash on the south to “Grassy Valley” on the north. The “Reefer 3” mineral claim and adit on the south side of Dry Wash are on carbonaceous mudstones of the lower split of the C-coal zone.

Kf-2-Willow Springs is defined on the north side of Willow Spring Wash, at its mouth. The landward edge of (Kf-2-WS) is present in the same area, a short distance west of the mouth. Thickening of the unit toward the northeast onto the point that lies north of the mouth of the wash occurs rapidly, surprisingly so since the amount of overall climbing of Kf-2 from here to where it passes beyond the seaward edge of Kf-1 is relatively small. The landward pinch-out is cut by a shale-filled channel, possibly of tidal origin. The seaward extent of (Kf-2-WS) has not yet been determined, but probably is present in the vicinity of “Swell Point.” Along the east-facing cliffs south of Coyote Basin, the tip of (Kf-2-WS) has been eroded and replaced by predominantly fine-grained deposits, some of which include “inclined heterolithics” indicative of channel deposition. This scour may be related to the areally more restricted scour that is present near the pinch-out. Relationships here require more study. A younger erosional surface that cuts (Kf-2-RC-a and b) in Coyote Basin area reaches the top of (Kf-1-WS) locally. Type locality: mouth of Dry Wash, north side, CSE1/4 section 18, T. 24 S., R. 6 E., Salt Lake Base Line. Landward limit: mouth of Dry Wash, north side, CSW1/4 section 18, T. 24 S., R. 6 E., Salt Lake Base Line. Seaward limit: not known accurately, approximately at “Swell Point”, SE1/4 section 18, T. 24 S., R. 6 E., Salt Lake Base Line. Facies content of shoreline unit: wave-modified coast, probably strand plain.

Kf-2-Rock Canyon-a is distinguished on the south side of “Swell Point.” There, Kf-2 thickens dramatically toward the east with addition of first (Kf-2-RC-a) and then (Kf-2-RC-b) over a short distance. (Kf-2-RC-a) and (Kf-2-RC-b) are readily distinguished only near their landward pinch-outs. There, on the south side of “Swell Point”, a lenticular channel deposit that cuts into the top of (Kf-2-RC-a) is in turn bevelled off by the transgressive surface of erosion at the base of (Kf-2-RC-b). Elsewhere, the two shoreline units lie one above the other, sharing a contact that places middle shoreface on middle shoreface, making them essentially indistinguishable. For this reason, it will be difficult or impossible to determine the seaward extent of (Kf-2-RC-a). The landward pinch-outs of both units were eroded and replaced by sandy, fluvial strata, so their exact locations are not known. Type section: south side of “Swell Point”, SW1/4SW1/4 section 8, T. 24 S., R. 6 E., Salt Lake Base Line. Landward limit: south side of “Swell Point”, approximately SW1/4SW1/4 section 8, T. 24 S., R. 6 E., Salt Lake Base Line. Seaward limit: not known; possibly near or north of Rock Canyon. Facies content of shoreline unit: not determined, probably wave-modified delta.

See discussion of (Kf-2-RC-a). (Kf-2-RC-b) appears to extend northward a great distance, perhaps all the way to Ivie Creek. If this proves to be so, (Kf-2-RC-b) and (Kf-2-Iv-a) may be equivalents. Type section: south side of “Swell Point”, SW1/4SW1/4 section 8, T. 24 S., R. 6 E., Salt Lake Base Line. Landward limit: south side of “Swell Point”, approximately SW1/4SW1/4 section 8, T. 24 S., R. 6 E., Salt Lake Base Line. Seaward limit: not known; may extend to Ivie Creek. Facies content of shoreline unit: not determined, probably wave-modified delta.

(Kf-2-Iv-a) is distinguished in the amphitheatre north of Ivie Creek. It is separated from overlying (Kf-2-Iv-b) by a surface that was initially interpreted to be a “marine-flooding surface” because it appeared to separate two vaguely upward-coarsening depositional sequences. Truncation of channel deposits in the lower part of Ivie Creek Canyon has subsequently been recognized at the top of (Kf-2-Iv-a), firming up the initial interpretation. (Kf-2-Iv-a) appears to be a wave-modified unit. Its relationship to (Kf-2-RC-b) is unclear and it is possible that these two units are equivalents. Suggested type section: near mouth of Ivie Creek Canyon, NE1/4SE1/4 section 17, T. 23 S., R. 6 E., Salt Lake Base Line. Landward limit: not yet determined. Seaward limit: not yet determined. Facies content of shoreline unit: not determined, probably wave-modified delta.

Kf-2-Iv-b. See comments for (Kf-2-Iv-a). Suggested type section: Same location as (Kf-1-Iv-a), near mouth of Ivie Creek Canyon, NE1/4SE1/4 section 17, T. 23 S., R. 6 E., Salt Lake Base Line. Landward limit: not yet determined. Seaward limit: not yet determined. Facies content of shoreline unit: not determined, probably strand plain and wave-modified delta.