Lithologies, ages, and provenance of clasts in the Ordovician Fincastle Conglomerate, Botetourt County, Virginia, USA

Belkin, Harvey E.; Repetski, John E.; Dulong, Frank T.; Hickling, N.L.

doi:10.29041/strat.15.1.1-20

Cited by 2 publications

(1 citation statement)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Much-perhaps most-of the sand and gravel accumulated in proximal to distal shelf environments of the now nearly filled Taconic foredeep (Figure 9K,L), but some of the gravels entered deeper waters along the edge of the shelf where they became the submarine fan deposits of the Fincastle Conglomerate, which is located at the northeasternmost margin of the Blount foredeep [54][55][56]. The red muds and clean quartzose sands did not reach this northernmost edge of the basin as molasse deposits, because the sediment that was transported down the feeder channels of the Fincastle submarine fan system consisted of sands and gravels with lesser non-red mud [66], and to the northeast (present-day) of the Fincastle area, the Taconic foredeep did not fill during the Blountian phase, but instead remained relatively deep in the region of modern West Virginia, Maryland, Pennsylvania, and New York, where much of the Blount-age sequence consists of deep water carbonates, e.g., the Salona Limestone [22,36]. Migrating sand waves produced occasional cross-bedding (Figure 8B-D,H), and episodic reworking by eolian processes produced the distinctive bimodal mature textures [67,68] seen in several samples of the Walker Mountain Sandstone (Figure 9I).…”

Section: Sedimentology Of Ordovician Arenites and Their Stratigraphic...mentioning

confidence: 99%

Testing Tectonostratigraphic Hypotheses of the Blountian Phase of the Taconic Orogeny in the Southern Appalachians through an Integrated Geochronological and Sedimentological Study of Ordovician K-Bentonites and Quartz Arenites

et al. 2023

View full text Add to dashboard Cite

The tectonic setting of the southernmost part of the eastern margin of Laurentia during the Blountian tectophase (~472–452 Ma) of the Ordovician Taconic Orogeny remains unresolved. Tephras produced by explosive volcanism during this early phase of the orogeny are now K-bentonites, and in many locations, they are interbedded with mature to supermature quartz arenites. We conducted U-Pb analyses of detrital zircons from the sandstones, and of zoned magmatic zircons from the K-bentonites, to constrain the tectonostratigraphic setting with more precision. We also used geochemical fingerprinting of apatite phenocrysts to correlate the K-bentonites in these sandstones along the tectonic front, and we then integrated these results with a depositional systems study of the quartz arenites to further constrain and test competing models of the regional tectonomagmatic setting during that time. The general dearth of detrital zircons that have ages contemporaneous with the volcanic activity, coupled with the predominantly Precambrian ages of the zircons in these Lower Paleozoic quartz arenites that otherwise lack volcaniclastic components—such as detrital VRFs or a muddy matrix derived from an eroding volcanic arc—suggests that magmatic zircons from the tephra layers entered the depositional system only occasionally, and that the volcanic centers were separated geographically from where these quartzose sands were being deposited. Our findings support a tectonostratigraphic and tectonomagmatic model analogous to a combination of select modern settings in the western Pacific and Indonesia, specifically (1) New Guinea, where mature quartz arenites occur in the Cenozoic foreland succession, and (2) Sumatra, where the enormous Toba caldera formed in association with subduction beneath the Cretaceous-aged continental crust of Sumatra.

show abstract

Section: Sedimentology Of Ordovician Arenites and Their Stratigraphic...mentioning

confidence: 99%

Testing Tectonostratigraphic Hypotheses of the Blountian Phase of the Taconic Orogeny in the Southern Appalachians through an Integrated Geochronological and Sedimentological Study of Ordovician K-Bentonites and Quartz Arenites

et al. 2023

View full text Add to dashboard Cite

show abstract

Outlier of Trenton Group limestones (Ordovician) and Clinch Sandstone (Silurian) and associated unconformities in the Tellico-Sevier syncline, Blount County, Tennessee, identified on the basis of conodont biostratigraphy

Haynes¹,

Leslie²,

Herrmann³

et al. 2020

The Appalachian Geology of John M. Dennison: Rocks, People, and a Few Good Restaurants Along the Way

View full text Add to dashboard Cite

A laterally discontinuous sandstone at the south end of the Tellico-Sevier syncline in Blount County, Tennessee, was mapped in 1955 by Robert Neuman and in 1965 by Neuman and Willis Nelson of the U.S. Geological Survey as a “quartzite” that they considered to be the uppermost bed of the Bays Formation (Ordovician). On the basis of new mapping and conodont biostratigraphy, lithostratigraphy, and regional K-bentonite correlations, this sandstone, a distinctive quartz arenite, is reassigned to and correlated with the Clinch Sandstone (Silurian). At the Harrison Branch section (HBRA) in Blount County, in an exposure near the confluence of Harrison Branch and the Little Tennessee River, this sandstone underlies the Devonian Chattanooga Shale, and it overlies ~43 m of gray limestones and shales that are themselves above the red clastic and minor carbonate rocks of the Bays Formation. The limestones and shales between the Bays Formation and this sandstone crop out on a wooded hillside and were apparently not observed by Neuman and Nelson during their mapping of the region. We measured the HBRA section, collected 20 samples from the limestone interval, and processed them for conodonts. These limestones contain a definitive Late Ordovician (Katian) conodont fauna that includes Drepanoistodus suberectus, Plectodina tenuis, Panderodus gracilis, and Phragmodus undatus. On the basis of this fauna, the 40+ m of limestone between the youngest red beds of unequivocal Bays Formation (below) and the quartz arenite (above) can be assigned to the Ordovician P. tenuis zone or younger, making them correlative regionally with limestones of the Trenton Group. Using these new biostratigraphic data combined with existing tephrostratigraphic relations of Ordovician K-bentonites, we identify the overlying sandstone at the HBRA section as an erosional outlier of the Silurian Clinch Sandstone, and we correlate the Ordovician-Silurian-Devonian unconformities at these two localities, which are now better constrained, with unconformities A through F in the Silurian and Devonian of this region, as identified and described in detail at several exposures north and northwest of the Tellico-Sevier syncline, most prominently at outcrops near Wytheville, Seven Mile Ford, and Max Meadows in southwest Virginia, where Devonian strata unconformably overlie Ordovician strata.

show abstract

Lithologies, ages, and provenance of clasts in the Ordovician Fincastle Conglomerate, Botetourt County, Virginia, USA

Cited by 2 publications

References 0 publications

Testing Tectonostratigraphic Hypotheses of the Blountian Phase of the Taconic Orogeny in the Southern Appalachians through an Integrated Geochronological and Sedimentological Study of Ordovician K-Bentonites and Quartz Arenites

Testing Tectonostratigraphic Hypotheses of the Blountian Phase of the Taconic Orogeny in the Southern Appalachians through an Integrated Geochronological and Sedimentological Study of Ordovician K-Bentonites and Quartz Arenites

Outlier of Trenton Group limestones (Ordovician) and Clinch Sandstone (Silurian) and associated unconformities in the Tellico-Sevier syncline, Blount County, Tennessee, identified on the basis of conodont biostratigraphy

Contact Info

Product

Resources

About