Dutch Flat Terrane - Feldspathic sandstone, shale, and turbiditic limestone

The Dutch Flat terrane is the Late Devonian Harmony Formation. It consists of coarse-graded feldspathic sandstone and siltstone with rare quartzose turbiditic limestone interbeds that have yielded sparse, reworked Late Devonian and post-Ordovician conodonts and conodont fragments (Jones, 1997a; Ketner, Crafford, and others, 2005). The age of the Harmony has never been well constrained. It was originally interpreted as Mississippian(?) because of its position unconformably beneath Pennsylvanian conglomerate at Battle Mountain (Ferguson, Roberts, and Muller, 1952; Roberts, 1951). Cambrian fossils were later found in close proximity to the unusual feldspathic sandstone and became the most commonly assumed age (Hotz and Willden, 1964), although the Cambrian fossils have since been recognized to be part of a structurally disrupted upper Paleozoic section (Jones, 1991b; Jones, Wrucke, and others, 1978; McCollum and McCollum, 1991). Ordovician microfossils from the Harmony Formation in the Sonoma Range (Madden-McGuire, Hutter, and Suczek, 1991) turned out to be unreliable as well. In 1994, a single Late Devonian Palmatolepis sp. conodont was recovered from a calcareous turbidite interbedded with the feldspathic sandstone in the Hot Springs Range (Jones, 1997a), and has remained the most convincing lower-age constraint thus far. Subsequent post-Ordovician conodont fragments also recovered from the Hot Springs Range have confirmed that the unit is clearly post-Ordovician in age (Ketner, Crafford, and others, 2005). The Dutch Flat terrane crops out in Humboldt, Lander, and Pershing Counties. In the Hot Springs Range, it is structurally bounded to the northwest by the Golconda terrane and on the southeast by unit DCs of the Basin assemblage. In the Osgood Mountains, it has been structurally dismembered into mélange blocks that are part of an upper Paleozoic matrix of argillite and shale associated with the Golconda terrane (Jones, 1991b). In the Sonoma and East Ranges, much of it is mélange-like in character and has additionally been folded and faulted with Triassic and Ordovician rocks (Silberling, 1975). At Battle Mountain (Doebrich, 1994; Theodore, Murchey, and others, 1994), it is interpreted as faulted over adjacent rocks of the Basin assemblage (DCs), and is also unconformably overlain by the Pennsylvanian rocks of the Siliciclastic overlap assemblage, providing a critical constraint on the timing of its accretion to adjacent rocks. Because it is structurally bounded everywhere, its stratigraphic relation to other units in Nevada remains uncertain, although it has lithologic features in common with rocks of the Golconda terrane and the lower Paleozoic Basin assemblage (Ketner, Crafford, and others, 2005). In places it has west vergent folding throughout (Jones, 1993; Stahl, 1987), while in other places the formation is characterized by east vergent folding (Evans and Theodore, 1978). Interpretations of the origin of the rocks of the Harmony Formation and its tectonic history (Gehrels, Dickinson, and others, 2000; Ketner, Crafford, and others, 2005; Smith and Gehrels, 1994) have yet to fully explain its significant role in the mid-Paleozoic tectonism that affected Nevada. Its varied structural characteristics and enigmatic lithology suggest that this terrane is far traveled and has had a complex history of interaction with other Paleozoic rocks in Nevada.
State Nevada
Name Dutch Flat Terrane - Feldspathic sandstone, shale, and turbiditic limestone
Geologic age Upper Devonian
Lithologic constituents
Sedimentary > Clastic > Siltstone (Bed, Melange)
Sedimentary > Clastic > Mudstone > Shale (Bed, Melange)
Sedimentary > Clastic > Sandstone (Bed, Melange)feldspathic sandstone
Sedimentary > Carbonate > Limestone (Bed, Melange)rare quartzose turbiditic limestone interbeds
NGMDB product
Counties Humboldt - Lander - Pershing