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Arc-To-Craton: Devonian Air-Fall Tephras in the Eastern United States

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Arc-To-Craton: Devonian Air-Fall Tephras in the Eastern United States OLD G The Geological Society of America Special Paper 545 OPEN ACCESS Arc-to-craton: Devonian air-fall tephras in the eastern United States C.A. Ver Straeten* New York State Museum & Geological Survey, 3140 Cultural Education Center, Albany, New York 12230, USA D.J. Over* Department of Geological Sciences, State University of New York–College at Geneseo, Geneseo, New York 14454, USA G.C. Baird* Department of Geosciences, State University of New York–Fredonia, Fredonia, New York 14063, USA ABSTRACT More than 100 air-fall volcanic tephra beds are currently documented from Devonian strata in the eastern United States. These beds act as key sources of vari- ous geological data. These include within-basin to basin-to-basin correlation, glob- ally useful geochronologic age dates, and a relatively detailed, if incomplete, record of Acadian–Neoacadian silicic volcanism. The tephras occur irregularly through the vertical Devonian succession, in clusters of several beds, or scattered as a few to single beds. In this contribution, their vertical and lateral distribution and recent radiometric dates are reviewed. Current unresolved issues include correlation of the classic Eifelian-age (lower Middle Devonian) Tioga tephras and dates related to the age of the Onondaga-Marcellus contact in the Appalachian Basin. Here, we used two approaches to examine the paleovolcanic record of Acadian–Neoacadian silicic magmatism and volcanism. Reexamination of volcanic phenocryst distribution maps from the Tioga tephras indicates not one but four or more volcanic sources along the orogen, between southeastern Pennsylvania and northern North Carolina. Final- ly, radiometric and relative ages of the sedimentary basin tephras are compared and contrasted with current radiometric ages of igneous rocks from New England. Despite data gaps and biases in both records, their comparisons provide insights into Devonian silicic igneous activity in the eastern United States, and into vari- ous issues of recognition, deposition, and preservation of tephras in the sedimentary rock record. *E-mails: [email protected]; [email protected]; [email protected]. Ver Straeten, C.A., Over, D.J., and Baird, G.C., 2020, Arc-to-craton: Devonian air-fall tephras in the eastern United States, in Avary, K.L., Hasson, K.O., and Diecchio, R.J., eds., The Appalachian Geology of John M. Dennison: Rocks, People, and a Few Good Restaurants along the Way: Geological Society of America Special Paper 545, p. 35–53, https://doi.org/10.1130/2020.2545(03). © 2020 The Authors. Gold Open Access: This chapter is published under the terms of the CC-BY license and is available open access on www.gsapubs.org. 35 Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/5177599/spe545-03e.pdf by guest on 26 September 2021 36 Ver Straeten et al. Figure 1. Photographs of Devonian air-fall tephra beds, eastern United States. Outcrop views are Devonian air-fall tephras; red arrows point to less obvious tephra beds in photos. (A) “Rickard’s” tephra, Lower Devonian Bald Hill Tephras cluster, Kalkberg (New Scotland?) Formation, Cherry Valley, New York. (B) Close-up of same tephra bed. Note gray color of clay-dominated “K-bentonite”–type tephra. (C) Multiple air-fall tephras of Lower Devonian Sprout Brook Tephras cluster, near Cobleskill, New York. (D) Coarse-grained “tuff” bed from Middle Devonian Tioga Teph- ras cluster, upper Needmore Formation, Massanutten Mountain, Virginia. Note sedimentary structures, indicative of resedimentation of tephra. (E) Belpre Tephra bed in Upper Devonian Rhinestreet Shale, on Lake Erie shore at Sea Scape, New York. (F) Close-up of a thin “gummy bed” tephra, seen as light-tan bedding plane at level of red arrow, to right of hammer. In lower Angola Shale, Point Breeze, near Angola, New York. (G) Four “gummy” tephra beds in upper Angola and lower Pipe Creek shales, south branch of Eighteen Mile Creek at Old Church Road, near Eden, New York. Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/5177599/spe545-03e.pdf by guest on 26 September 2021 Arc-to-craton: Devonian air-fall tephras in the eastern United States 37 INTRODUCTION Various descriptive names are applied to air-fall volcanic tephras in the sedimentary record and scientific literature. These Air-fall volcanic tephra beds in sedimentary successions are sometimes imply grain size (e.g., tuff); often, they reflect the dia- key sources of varied geological information. A product of explo- genetic history of a tephra (e.g., bentonite, K-bentonite, metaben- sive silicic volcanism, tephra is forcefully ejected from an under- tonite, tonstein), or a generic, common name for such layers (e.g., lying magma chamber, thrust upward into the troposphere or even ash). If shown to be of an air-fall volcanic origin, these layers are, the stratosphere, and transported, settling across all environments independent of applied descriptive terms, tephras, i.e., layers of downwind of the source volcano. Dependent on several factors, extruded igneous materials (ash, pumice, phenocrysts, and rock some tephras are deposited across a significant geographic area. fragments). Following the practice of Cenozoic volcanologists, When preserved in strata, they provide key, distinct marker beds and as recommended to Ver Straeten in discussions with Andrei for local to long-distance correlation, and their radiometric dates Sarna-Wojcicki (2007, personal commun.), the term “tephra” is allow for refinement of the geologic time scale. In addition, they utilized throughout this paper, with the other terms retained as comprise a key source of information for reconstructing a history descriptive modifiers. Images of some eastern U.S. Devonian of paleovolcanism, which is especially crucial adjacent to deeply tephra beds are shown in Figure 1. eroded magmatic/volcanic arcs. During the Devonian, large portions of eastern Laurentia Following the settling and deposition of tephra materials (North America) were at times flooded by shallow seas. Sub- (extruded ash, pumice, phenocrysts, and rock fragments) onto duction and collisional tectonic processes resulted in uplift of an land or through water to the sediment floor, a primary tephra layer orogenic belt extending from east Greenland to the southeastern is exposed to various active environmentally dependent processes United States, with widespread deformation, metamorphism, (Ver Straeten, 2004a). Rapid burial under relatively low-energy magmatism, and flexural downwarping of a retroarc foreland and biologically inactive conditions best preserves a primary basin system. The Appalachian Basin region has been variously air-fall tephra. Low sedimentation rates under quiet conditions interpreted to have been located 25°S–40°S of the equator (van may lead to stacking of multiple eruptive event layers. In most der Voo, 1988; Witzke and Heckel, 1988; Scotese and McKer- settings, a range of physical, biological, and chemical processes row, 1990). In this setting, explosive silicic volcanism resulted act on exposed tephra sediments, mixing them with subsequently in deposition of numerous air-fall volcanic tephras in Devonian deposited tephra and/or background sediments, sometimes lead- strata across the region. ing to complete mixing and obliteration of the eruptive event. In this paper, we review the occurrence of known Devonian Studies on the postdepositional history of tephras include Baird air-fall tephras from the eastern United States (Figs. 2 and 3), et al. (1994), Huff et al. (1999), Königer and Stollhofen (2001), followed by a discussion of correlation issues of various Eif- Ver Straeten (2004a, 2008), Benedict (2004), Ver Straeten et al. elian Stage (lower Middle Devonian) Tioga tephras, and dat- (2005), and Püspöki et al. (2005, 2008). ing of the Eifelian Stage base of Marcellus strata. In addition, Figure 2. Study area map of Devonian tephras, eastern United States. Area within thick dark line denotes region of studied tephra beds for this paper, includ- ing maps from Dennison and Textoris (1987). Abbreviations: DE— Delaware; IA—Iowa; IL— Illinois; IN—Indiana; KY—Kentucky; MD— Maryland; MI— Michigan; MO— Missouri; NC—North Carolina; NJ—New Jersey; NY—New York; OH—Ohio; ONT—Ontario, Cana- da; PA— Pennsylvania; TN— Tennessee; VA—Virginia; WI—Wisconsin; WV— West Virginia. Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/5177599/spe545-03e.pdf by guest on 26 September 2021 38 Ver Straeten et al. Figure 3. Devonian air-fall teph- ra beds, eastern United States. Time-distribution of known and possible volcanic air-fall tephra beds is plotted again Devonian time scale of Becker et al. (2012), with age in Ma. Over 100 indi- vidual air-fall tephra beds are now documented from Lower to Upper Devonian strata. Arrows denote major clusters of eight or more tephras. See key for further info on tephra bed–related sym- bols. Some dated tephras disagree with the time scale (circled num- bers 1–3). Circled 1—In New York, the base of the Esopus, and the position of the Sprout Brook Tephras are interpreted to fall at or close to the base of the Emsian Stage, but no biostratigraphic data are available to delineate this well. Circled 2—A new ra- diometric date for a bed in the Belpre cluster is 375.1 Ma, which is different from the Devonian time scale utilized here (Lanik et al., 2016; this paper). Circled 3—The current best date for the Frasnian-Famennian boundary is 371.9 Ma (M. Schmitz, 2014, personal commun.), which is dif- ferent from the Devonian time
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