Research Paper THEMED ISSUE: Geologic Evolution of the Alaska Range and Environs

GEOSPHERE The Mystic subterrane (partly) demystified: New data from the Farewell terrane and adjacent rocks, interior Alaska GEOSPHERE; v. 14, no. 4 Julie A. Dumoulin1, James V. Jones III1, Stephen E. Box2, Dwight C. Bradley3,*, Robert A. Ayuso4, and Paul O’Sullivan5 1U.S. Geological Survey, Alaska Science Center, 4210 University Dr., Anchorage, Alaska 99508, USA https://doi.org/10.1130/GES01588.1 2U.S. Geological Survey, Spokane, Washington 99201, USA 3U.S. Geological Survey, Anchorage, Alaska 99508, USA 17 figures; 3 tables; 1 set of supplemental files 4U.S. Geological Survey, Reston, Virginia 20192, USA 5GeoSep Services, 1521 Pine Cone Road, Moscow, Idaho 83843, USA

CORRESPONDENCE: [email protected]

CITATION: Dumoulin, J.A., Jones, J.V., III, Box, ABSTRACT Our findings support previous models suggesting that the Farewell terrane S.E., Bradley, D.C., Ayuso, R.A., and O’Sullivan, P., 2018, The Mystic subterrane (partly) demystified: was proximal to the Alexander-Wrangellia-Peninsular composite terrane New data from the Farewell terrane and adjacent The youngest part of the Farewell terrane in interior Alaska (USA) is the during the late Paleozoic, and further suggest that such proximity continued rocks, interior Alaska: Geosphere, v. 14, no. 4, enigmatic Devonian–Cretaceous Mystic subterrane. New U-Pb detrital zircon, into (or recurred during) the Late Triassic–Early Jurassic. But middle to late p. 1501–1543, https://doi.org/10.1130/GES01588.1. fossil, geochemical, neodymium isotopic, and petrographic data illuminate the Permian detrital zircons in northern Farewell require another source; the origin of the rocks of this subterrane. The Devonian–Permian Sheep Creek For- Yukon-Tanana terrane is one possibility. Science Editor: Raymond M. Russo Guest Associate Editor: Jeff Benowitz mation yielded youngest detrital zircons of Devonian age, major detrital zircon age probability peaks between ca. 460 and 405 Ma, and overall age spectra like Received 24 July 2017 those from the underlying Dillinger subterrane. Samples are sandstones rich INTRODUCTION Revision received 23 February 2018 in sedimentary lithic clasts, and differ from approximately coeval strata to the Accepted 25 April 2018 east that have abundant volcanic lithic clasts and late Paleozoic detrital zircons. The Farewell terrane (Alaska, USA) is a regionally extensive, deformed Published online 30 May 2018 The Permian Mount Dall conglomerate has mainly carbonate and chert clasts continental fragment (Fig. 1) made up of Proterozoic, Paleozoic, and Mesozoic and yielded youngest detrital zircons of latest Pennsylvanian age. Permian rocks; understanding its history is a critical component in unraveling the com- quartz-carbonate sandstone in the northern Farewell terrane yielded abundant plex tectonic story of Alaska. Key questions center around its cratonic origins, middle to late Permian detrital zircons. its separation from and subsequent interactions with other terranes, and its Late Triassic–Early Jurassic mafic igneous rocks occur in the central and eventual incorporation into the Alaskan tectonic collage. Proterozoic and Pa- eastern Mystic subterrane. New whole-rock geochemical and isotopic data leozoic strata that form the core of Farewell are more thoroughly studied than indicate that magmas were rift related and derived from subcontinental mantle. younger parts of this terrane and have well documented ties to multiple ter- Triassic and Jurassic strata have detrital zircon age spectra much like those of ranes including the Arctic Alaska, Livengood, White Mountains, Kilbuck, and the Sheep Creek Formation, with major age populations between ca. 430 and Alexander terranes (Fig. 1; Blodgett et al., 2002; Dumoulin et al., 2002, 2014, 410 Ma. These rocks include conglomerate with clasts of carbonate ± chert and 2018b; Bradley et al., 2014). These ties are supported by diverse data sets in- youngest detrital zircons of Late Triassic age and quartz-carbonate sandstone cluding faunal assemblages, lithologic successions, and detrital zircon ages. OLD G with youngest detrital zircons of Early Jurassic age. Lithofacies indicating Overlying Devonian and younger rocks of the Mystic subterrane represent highly productive oceanographic conditions (upwelling?) bracket the main part the continued evolution of the Farewell terrane and are expected to have re- of the Mystic succession: Upper Devonian bedded barite and phosphatic Upper corded key events and interactions as it was accreted to northwestern North Devonian and Lower Jurassic rocks. America. However, the basic lithostratigraphy, geologic evolution, terrane OPEN ACCESS The youngest part of the Mystic subterrane consists of Lower Cretaceous affinities, and tectonic interactions of the Mystic remain incompletely under- (Valanginian–Aptian) limestone, calcareous sandstone, and related strata. These stood. Recent studies have elucidated specific aspects of Mystic subterrane rocks are partly coeval with the oldest parts of the Kahiltna assemblage, an geology (Malkowski and Hampton, 2014), and available data suggest link- overlap succession exposed along the southern margin of the Farewell terrane. ages between Farewell and insular terranes (i.e., Alexander and Wrangellia) outboard of western North America during the late Paleozoic and possibly later (Beranek et al., 2014; Malkowski and Hampton, 2014). Fossil and detrital This paper is published under the terms of the zircon data also indicate continuing connections between terranes of the Arc- CC‑BY-NC license. *Retired. Current address: 11 Cold Brook Road, Randolph, New Hampshire 03593, USA tic realm and Siberia (Bradley et al., 2003; Colpron and Nelson, 2011) and/or

© 2018 The Authors

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168°W 165°W 162°W 159°W 156°W 153°W 150°W 147°W 144°W1141°W 138°W 135°W 132°W 129°W 126°W23°W 120°W 68°N EXPLANATION 70°N Quaternary N Other rocks Arctic Alaska–Chukotka 66°N terrane 68°N White Mountains terrane Livengood terrane B r o o k s R a n g e Innoko terrane 64°N

66°N Farewell terrane Chulitna terrane Seward CR Peninsula G Kilbuck terrane 62°N 64°N Laurentia Yukon-Tanana terrane Farewell Figure 1. Map of Alaska (USA) showing Wrangellia terrane selected terranes, adapted from Silber- 60°N ling et al. (1994). Detrital zircon sample 62°N Peninsular terrane localities: CR—Cascaden Ridge unit; terrane Alexander terrane G—Globe unit. T—Tikchik terrane.

58°N 60°N T

58°N 56°N

56°N 54°N

200 Kilometers 54°N 162°W 159°W 156°W 153°W 150°W 147°W 144°W 141°W 138°W 135°W 52°N

Baltica (Ershova et al., 2016). In this paper, we use new U-Pb detrital zir- GEOLOGIC SETTING con, fossil, geochemical, neodymium isotopic, and petrographic data from the northern, central, and eastern parts of the Mystic subterrane (Fig. 2) to The Farewell terrane (Decker et al., 1994; Bundtzen et al., 1997; Bradley et illuminate the Devonian and younger evolution of the Farewell terrane as a al., 2003) is made up of a Proterozoic basement complex overlain by younger means of evaluating its tectonic interactions with other Alaskan terranes and, Proterozoic through Mesozoic rocks. Farewell exposures span an area of more ultimately, western North America. than 87,000 km2 in south-central Alaska, and they are cross-cut by and displaced The Livengood and White Mountains terranes (Fig. 1) of Silberling et al. along multiple Cenozoic strike-slip faults (Fig. 2). Rocks of the Farewell terrane (1994) have lithologic and faunal features that suggest ties to the Farewell ter- are broadly grouped into the Nixon Fork, Dillinger, and Mystic subterranes, and rane during the early Paleozoic (Blodgett et al., 2002; Dumoulin et al., 2014). Figure 3 shows the generalized lithostratigraphy and spatial associations of these New detrital zircon data from rocks in these terranes that are coeval with the three subterranes across the six geographic areas outlined in Figure 2. lower part of the Mystic subterrane allow us to test whether these linkages The Nixon Fork subterrane is a Proterozoic through Devonian carbonate extended into the middle Paleozoic. platform that overlies the only observed exposures of Proterozoic basement

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Figure 2. Generalized geologic map of the Farewell terrane and location of some detrital zircon localities discussed in text. See Figure 4 for an enlarged version of areas E and F and key to locality symbols. White areas on map are covered by snow or ice. The western and central parts of the Alaska Range extend through areas E and F.

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Figure 3. Stratigraphy of the Mystic subterrane; data sources are given in text. See Figure 2 for location of areas A–F. Lower–Middle Devonian carbonate strata in areas D–F are faunally and litholog- ically similar to the upper part of the Nixon Fork carbonate platform and are likely depositional or tectonic outliers of that platform. Absolute ages in time scale boundaries and chronostratigraphy are from Walker et al. (2012). Lithic grain abbreviations: Lm—metamorphic; Ls—sedimentary; Lv—volcanic; Qm—monocrystalline quartz; ss—sandstone. Time scale abbreviations: A—Aptian; B/V— Berriasian–Valanginian; C—Cisuralian; Camb.—Cambrian; Cret.—Cretaceous; E—Emsian; Ei—Eifelian; Fa—Famennian; Fr—Frasnian; G—Guadalupian; Gi—Givetian; H/B—Hauterivian–Barremian; L—Lower; Lc—Lochkovian; Lo—Lopingian; Lu—Ludlow; M—Middle; Miss.—Mississippian; Mo—Moscovian; N—Norian; Ord.—Ordovician; P—Pliensbachian; Penn.—Pennsylvanian; Pr—Pragian; S—Sinemurian; Se—Serpukhovian; Sil.—Silurian; T—Tournaisian; U—Upper; V—Visean; W—Wenlock. Stratigraphic column abbreviation: C—central.

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in the Farewell terrane (Fig. 2). The Dillinger subterrane consists of a Cam- oceanographic settings. Rare shallow-water carbonate rocks of Mississippian, brian(?) through Devonian sedimentary succession that is interpreted to be the Pennsylvanian, Permian, and Triassic ages are found chiefly on and adjacent to deep-water equivalent of the Nixon Fork carbonate platform. Rocks of the car- the Nixon Fork platform (areas A through C, western area D; Patton et al., 1980; bonate platform and deep-water successions locally interfinger and grade into McRoberts and Blodgett, 2002; Gilbert, 1981; Bundtzen et al., 1994). each other, and they are interpreted to have formed along a passive margin Siliciclastic strata of middle to late Paleozoic age crop out sparsely in areas (Bradley, 2008). The lithostratigraphy of these two subterranes is discussed in A, D (eastern part), and E, and widely in area F (Figs. 2, 3). These units include detail elsewhere (Decker et al., 1994; Bundtzen et al., 1997; Bradley et al., 2003, unnamed Permian strata in area A (Patton et al., 1980), the upper part of the 2014; Dumoulin et al., 2018b). Devonian–Permian Sheep Creek Formation (Bundtzen et al., 1997) in area E, The Mystic subterrane is an overlap assemblage comprising Devonian and the Permian (and older?) “Mystic assemblage” of Malkowski and Hamp- through Lower Cretaceous rocks that overlie strata of both the Nixon Fork and ton (2014) and the Permian Mount Dall conglomerate (Reed and Nelson, 1980; Dillinger subterranes. We refer to the Mystic as a subterrane of the Farewell Sunderlin, 2008) in area F. Late Triassic–Early Jurassic mafic igneous rocks (ar- terrane in order to be consistent with nomenclature in previous studies (e.g., eas C through F) are intercalated with and overlain by a variety of Triassic and Bundtzen et al., 1997; Malkowski and Hampton, 2014). Rocks included in the Jurassic sedimentary strata (Reed and Nelson, 1980; Gilbert, 1981; Bundtzen Mystic subterrane are widely but sparsely distributed through much of the et al., 1994, 1997). Lower Cretaceous fossiliferous limestone and siliciclastic Farewell terrane but are thickest and most abundant to the southeast in the rocks form the uppermost part of the Mystic in areas A, E, and F (Jones and central and western Alaska Range (Fig. 2). The overall succession is typically Silberling, 1979; Patton et al., 1980; Reed and Nelson, 1980). bounded by unconformities, although the lower contact (Mystic rocks above In contrast with the relatively homogenous and regionally consistent, Nixon Fork or Dillinger strata) locally appears conformable (Decker et al., 1994). predominantly passive margin successions of the underlying Nixon Fork and The upper contact is a major angular unconformity overlain by sedimentary Dillinger subterranes, lithologies of the Mystic subterrane—which include rocks of the Upper Cretaceous Kuskokwim Group in the west and the Upper shallow-water carbonate, diverse siliciclastic, and volcanic rocks—suggest a Jurassic(?)–Upper Cretaceous Kahiltna assemblage to the east (Bundtzen et al., more active tectonic setting (Bundtzen et al., 1997). Upper Paleozoic sedimen- 1997; Wilson et al., 2015). In many areas, both the upper and lower contacts are tary strata of the Mystic have been interpreted as foreland deposits associated faulted. Stratigraphy of the Mystic subterrane varies considerably across its with the late Paleozoic Browns Fork orogen (Bradley et al., 2003). Widespread geographic extent and is discussed below using representative sections from mafic volcanic rocks (Tatina River volcanics and related units) of Late Triassic six map areas (A) central Medfra quadrangle, (B) northern Taylor Mountains and/or Early Jurassic age may have formed in a continental margin rift setting quadrangle, (C) White Mountain area in the southern McGrath quadrangle, (Bundtzen et al., 1997). At least some of the lithologic variation within the Mys- (D) central Lime Hills quadrangle, (E) southeastern McGrath-northeastern Lime tic may reflect topographic irregularities inherited from the underlying Nixon Hills quadrangles, and (F) western Talkeetna quadrangle (areas A through F in Fork–Dillinger passive margin. Figs. 2, 3; all quadrangles are 1:250,000 scale).

SAMPLES AND METHODS STRATIGRAPHY OF THE MYSTIC SUBTERRANE In this paper, we present new fossil, geochemical, isotopic, lithologic, and The oldest rocks assigned to the Mystic subterrane are Lower–Middle U-Pb detrital zircon data from a variety of Mystic subterrane units in areas Devonian limestones (e.g., map unit lDl of Bundtzen et al., 1994, 1997; see also A, E, and F (Figs. 2–4). These data include geochemical, fossil, and lithologic Blodgett et al., 2002; Table 1, sample 11AD201AA) that overlie rocks of the Dil- data from Upper Devonian bedded barite, black shale, and phosphatic chert in linger subterrane in areas D through F (Figs. 2, 3). These rocks are coeval with, areas E and F; detrital zircon, fossil, geochemical, and petrographic data from and lithologically similar to, the youngest strata of the Nixon Fork subterrane upper Paleozoic and Mesozoic strata in areas A, E, and F; and geochemical and in areas A and C, and we suggest that they represent progradational or tec- neodymium isotopic data from Triassic–Jurassic mafic igneous rocks in areas tonic outliers of the Nixon Fork platform. A progradational relationship has E and F. We also discuss new detrital zircon results from Devonian and Missis- been documented elsewhere in the Farewell terrane: the Dyckman Mountain sippian(?) strata in the Livengood and White Mountains terranes, respectively unit (east of area A; Fig. 2) consists of Lower–Middle Devonian platform facies (Livengood 1:250,000-scale quadrangle; Fig. 1). Previously unpublished fossil of the Nixon Fork that overstepped older Dillinger basinal facies (Dumoulin data are presented in Table 1. Chronostratigraphic correlations follow Walker et al., 2000). Upper Devonian carbonate and siliciclastic rocks overlie older et al. (2012). Devonian strata in areas C through F (Reed and Nelson, 1980; Gilbert, 1981; Detrital zircon sample coordinates and descriptions are presented in Bundtzen and Gilbert, 1991; Bundtzen et al., 1994, 1997) and include distinctive Table 2, and summaries of detrital zircon U-Pb age populations are presented minerals such as barite and phosphate that typically form in highly productive together with relevant stratigraphic data and age constraints in Table 3.

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TABLE 1. LOCATIONS AND DESCRIPTIONS OF SAMPLES ANALYZED FOR FOSSILS FROM THE FAREWELL TERRANE, ALASKA

Latitude Sample; (°N); quadrangle (locality longitude Sample description [loc.] no.) (°W) (relevant photographs) Fossils Age and/or depositional setting (CAI) Source and comments Devonian carbonate rocks 11AD201AA 62.5884 Peloid-bioclast packstone- Conodonts: indet. ozarkodinid spp. (2 P Silurian–Middle Devonian (4) J. Repetski, 2017, personal Talkeetna C6 152.8373 grainstone and 3 S elements), Panderodus sp. (3 commun.; strata mapped as unit elements), Dvorakia? sp. (3 elements) Dl by Reed and Nelson (1980) 12AD319M 62.0189 Concretion (9 cm diam); coral Coral: Cystiphylloides sp. Probable Middle Devonian C. Stevens, 2014, personal McGrath A2 (loc. 2) 153.6833 in calcareous radiolarite commun. matrix (Fig. 5G) 77APa507B* 63.6517 Corals in dolomitic matrix, Coral: Sociophyllum sp. cf. S. glomerulatum Late Middle Devonian (Givetian) C. Stevens, 1999, personal Medfra C4 154.5867 brachiopod and (Crickmay), which occurs in Northwest commun. Depositional position of echinoderm fragments Territories, Canada sample uncertain; clast in Permian conglomerate or from strata underlying Permian section Carbonate rocks associated with the late Paleozoic Mystic assemblage (and/or unit Pzus?) 03ADw400A 62.5267 Crinoidal grainstone, foraminifers, Conodonts: Devonian: Icriodus sp.; Late Miss: No older than Pennsylvanian to very Early A. Harris, 2004, personal commun. Talkeetna C6 (loc. 7) 152.6328 bryozoan and brachiopod Gnathodus bilineatus Roundy; Miss or Penn: Permian, with redeposited Devonian (Reed and Nelson, 1980, fragments, minor Ls, chert Cavusgnathus sp. or Adetognathodus sp.; and Late Mississippian conodonts; lag their loc. 16) clasts (Fig. 6G) Penn: gondolellid frag; Idiognathodus sp., deposit (3.5–4) Idiognathoides sp., or Streptognathodus sp. frag; Streptognathodus sp. 03ADw415H 62.6186 Fine dolomitic limestone Conodonts: Oulodus? sp. indet. Silurian–Middle Devonian (5) A. Harris, 2004, personal commun.; Talkeetna C6 (loc. 9) 152.7807 sample erroneously reported as barren by Bradley et al. (2007) Permian Mount Dall conglomerate 00ADw100 62.5944 Clast AD-MD-1, 17 x 13 cm Conodonts: Belodella sp. (1 element), indet. Silurian–Devonian (4–4.5) J. Repetski, 2017, personal commun. Talkeetna C5 (loc. 11) 152.1681 diam, fine carb ozarkodinid S2 element (1), indet. elements (12 frags) 00ADw100H 62.5944 Clast, 20 x 20 cm diam, Foraminifers: Earlandia moderata grp., Late Mississippian(?); typical Northern P. Brenckle, 2016, personal commun.; Talkeetna C5 (loc. 11) 152.1681 bioclastic (crinoidal) Paraarchaediscus sp., indet. endothyrids, Hemisphere taxa (no Tethyan forms); this sample also produced conodonts grainstone (Figs. 9F, 9G) ?Paraarchaediscus koktjubensis, abraded bioclasts and ooids indicate of Early–Middle Penn (early, but not Endothyra prisca, “Nodosarchaediscus” high-energy deposit with probable earliest, Morrowan–Desmoinesian) sp., ?Viseidiscus primaevus , “Priscella” reworking; well size-sorted allochems age (Bradley et al., 2003), so sp. Alga: Stacheoides sp., Epistacheoides suggest winnowing foraminifers may be redeposited sp.; incertae sedis: Diplosphaerina and/or Eotuberitina sp. 00ADw100J 62.5944 Clast, ~20 cm diam, bioclastic Foraminifers: Paraarchaediscus sp., Late Mississippian(?); typical Northern P. Brenckle, 2016, personal commun. Talkeetna C5 (loc. 11) 152.1681 (crinoidal) grainstone indet. endothyrids, “Priscella” sp., Hemisphere taxa (no Tethyan forms); “Nodosarchaediscus” sp., Endothyra aff. abraded bioclasts and ooids indicate E. obsolete, Paraarchaediscus infantis, high-energy deposit with probable Pseudoammodiscus priscus, Archaediscus reworking; well size-sorted allochems sp., ?Paraarchaediscus planus (Bozorgnia), suggest winnowing Paraarchaediscus aff. convexus,; incertae sedis: Diplosphaerina and/or Eotuberitina sp. Permian strata 77APa149* 63.6667 Bryozoan-crinoid-brachiopod Barren of conodonts but yielded phosphatic A. Harris, 1999, personal commun.; Medfra C4 154.5833 grainstone, 10%–20% detrital brachiopod fragments, phosphatized spines, ts has likely shell fragments of quartz spicules, steinkerns Atomodesma Triassic strata 12AD319N 62.0207 Fine carb clast cgl; matrix includes Conodonts: Dvorakia sp. (4 elements), Ordovician(?), Silurian–Devonian J. Repetski, 2017, personal commun.; McGrath A2 (loc. 12) 153.6909 detrital quartz, feldspar, chert ozarkodinid spp. indet. (2 Pb and 4 S (2.5?, 3, 4, 4.5) sample includes clasts and matrix grains elements), coniform elements (6, most likely of Icriodus, Distomodus, and/or Decoriconus spp.), indet. gen. and spp. fragments (~12) (continued)

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TABLE 1. LOCATIONS AND DESCRIPTIONS OF SAMPLES ANALYZED FOR FOSSILS FROM THE FAREWELL TERRANE, ALASKA (continued) Latitude Sample; (°N); quadrangle (locality longitude Sample description [loc.] no.) (°W) (relevant photographs) Fossils Age and/or depositional setting (CAI) Source and comments

11ADw119V 62.3915 Very fine carb clast (22 cm diam) Barren of conodonts J. Repetski, 2011, personal commun. McGrath B1 (loc. 13) 153.0828 Jurassic strata 12AD320H 61.9691 Large cobble of quartz sandstone Bivalves: Gryphaea rockymontana Warren, Early Jurassic (Sinemurian); warm, R. Blodgett, 2014, personal commun. Lime Hills D3 (loc. 21) 153.7843 with bivalve debris (Fig. 13D) Pinna sp., Ostrea sp., possible pectinoid, shallow-water, tropical to subtropical fine-ribbed form inner shelf setting 13AD409AA 61.8044 Bioclastic limestone with smooth Bivalves: Gryphaea rockymontana Warren Early Jurassic (Sinemurian); warm, R. Blodgett, 2014, personal commun. Lime Hills D3 (loc. 17) 154.0484 shell fragments shallow-water, tropical to subtropical inner shelf setting 13SB28F 62.3818 Very fine to fine calcareous Ammonites: arietitid, possibly Coroniceras sp. Early Jurassic (early? Sinemurian); T. Poulton, 2014; personal commun.; McGrath B1 (loc. 20) 153.1349 sandstone (Fig. 13C) (Fig. 13C), specimen from second horizon specimen from second horizon could two fossil horizons ~10 ft could be same form or ?Leptechioceras sp. be same age or late Sinemurian stratigraphically apart 13SB28F 62.3818 Very fine to fine calcareous Ammonites: Paracoronoceras sp. (Fig. Early Jurassic (Sinemurian) J. Haggart, 2014; personal commun. McGrath B1 (loc. 20) 153.1349 sandstone (Fig. 13C) 13C), specimen from second horizon is Megarietites? or Metophioceras?. Bivalve: likely Modiolus sp. 76ANs17C* 62.4983 Limestone with abundant Crinoid: Pentacrinus similar to Pentacrinus Early(?) Jurassic D.L. Jones, 1977, personal commun.; Talkeetna B6 152.6000 echinoderm fragments, partly subangularis alaska Springer field notes and fossil reports (Reed and Nelson, 1980, replaced by chert indicate Jurassic and Cretaceous their loc. 24) strata occur here 75AR38A, 75AR39*; 62.5333 Brown to black, ferruginous, Ammonites (arietitids, Coroniceras Early Jurassic (early Sinemurian) R. Imlay, 1975, 1976, personal 76Dt147 152.8833 calcareous siltstone to sp.), belemnites, bivalves (Entolium commun; Sandy and Blodgett Talkeetna C6 sandstone that underlies sp., ?Eopecten sp., Gryphea cf. G. (2000); field notes and fossil (Reed and Nelson, 1980, Buchia-bearing limestone rockymontana, Oxytoma cf. O. cygnipes, reports indicate Jurassic and their loc. 28) Plagiostoma sp., ?Plicatula sp., Weyla sp.), Cretaceous strata occur here and brachiopods (Liospiriferina rostrata, rhynchonellids) 76AR16, 76AR17* 62.4792 Fossiliferous calcareous sandstone Ammonite (Coroniceras sp.), bivalves Early Jurassic (early Sinemurian) R. Imlay, 1976, personal commun. Talkeetna B6 152.8205 that overlies Dillinger strata (?Eopecten sp., Gryphea cf. G. (Reed and Nelson, 1980, with angular unconformity rockymontana, Pleuromya sp., ?Weyla sp.), their loc. 29) and rhynchonellid brachiopods 76AR13* 62.3417 Shell beds in limy, ferruginous Bivalves (?Entolium sp., ?Grammatodon sp., Early Jurassic R. Imlay, 1976, personal commun.; McGrath B1 153.3028 sandstone, ~25–75 ft above Lima sp., Weyla sp.), brachiopods field notes indicate that strata of base of unit this unit are interbedded with mafic igneous rocks (B. Reed, 1976, personal commun.) 84BT116* 62.3889 No information available Bivalves (?Eopecten sp., Entolium sp.) Probably Jurassic Elder and Miller (1991); latitude and McGrath B1 153.0306 longitude based on T, R, S and elevation data Cretaceous strata 13AD409A 61.8044 Bivalve shell coquina (Figs. 13G, Belemnite guard; bivalves (Buchia sp. shell Early Early Cretaceous (Berriasian– R. Blodgett, 2014, personal commun. Lime Hills D3 (loc. 17) 154.0484 13H) hash) Valanginian, likely Valanginian) 13AD409C, 13AD409J 61.8044 Fine bioclastic limestone (Fig. 13I) Belemnite (13AD409J); bivalves (thick Early Cretaceous, most probably R. Blodgett, 2014, personal commun. Lime Hills D3 (loc. 17) 154.0484 inoceramid shell fragments; 13AD409C, Hauterivian–Berremian 13AD409J) 75AR38C 62.5333 Bivalves in limestone matrix Bivalve: Buchia crassicollis solida Early Early Cretaceous (Valanginian) R. Imlay, 1975, personal commun. Talkeetna C6 152.8833 (Reed and Nelson, 1980, their loc. 28) Note: Localities are shown on Figure 4 except where noted. Lithic grains: Ls—sedimentary. CAI—conodont color alteration index; carb—carbonate; cgl—conglomerate; diam—diameter; frag—fragment; Miss— Mississippian; Penn—Pennsylvanian; T, R, S—township, range, section; ts—thin section. *Latitude and longitude were determined using station location on a field sheet.

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Figure 4. Geology of southeastern McGrath, northeastern Lime Hills, and southwestern Talkeetna quadrangles, showing location of samples. MP— Mystic Pass. Number 2 within sample symbols at localities 12 and 17 indi- cates 2 samples were analyzed.

Table DR1. Detrital zircon U-Pb data and plots

Notes: for all grains, the calculated concordia age (highlighted in green) was used for each grain. The column labeled "Preferred age" is either the 206/238 or 207/206 age. The two coulmns that area lbeeld" Ageco mpasori n"sh ows thec aclualetdc oncordaia gea ndht e preferred age to illustrate that there is generally good agreement between the two. In the U-Pb concordia diagrams shown to the right of each sample, the ellipses are shaded by probabytilo ic foncordance( POCuo)lt lsi ratetht ereo ailntshpbi ewteenht ec acluaeltdP OCa nd concordia for each analysis. Age probability diagrams are kernel density estimates (KDEs) and were generated using the Density Plotter tool of Vermeesch (2012). The horizontal axis is age (in Ga), and the vertical axiss i number of granis for the hstiogramH .siotgramb nisa er all approximately 10 m.y. Analyses shown in strikethrough were not used in age calculations and are not included in the plots because they did not meet the screening crteiria descrbiedn i the mani text. Fore fidls that aree lb tfalnkht ,osed aatw eren ore tpoertdof htr as tpecic fi sample.

Ur anium and Thorium Corrected Isotopic Ratios Concordia age Age comparison Corrected isotopic ages Preferred Isotopic Age Sample Analysis Name Concordia age Concordance Concordia age Pr eferred Age Concordia age 207Pb/235U Age 206Pb/238U Age Pr eferred Age U (ppm)Th (ppm)U/Th 207Pb/235Uc ± (2σ) 206Pb/238U ± (2σ) rho ± (2σ) MSWD POC± (1σ) % error ± (1σ) + (2σ) - (2σ) + (2σ) - (2σ) 207Pb/206Pb Age (Ma) + (2σ) - (2σ) + (2σ) - (2σ) Age Type Concordant Scans Discordant Scans (Ma) (%) (Ma) (Ma) (Ma) (Ma) (Ma) (Ma) 07ADw711A: Sheep Creek Formation 07ADw711A 86908_41 1633 1691 0.97 0.47988 0.01690 0.05960 0.00148 0.05 382.17 7.30 11.88 0.00 3.65 0.96 68.49 382.17 3.65 373.16 382.17 397.99 11.63 11.56 373.16 8.98 8.98 544.85 80.47 78.49 373.16 8.98 8.98 206Pb/238U concordant scans 28 178 07ADw 711A 86908_105185 1511.230.504180.03351 0.066310.00190 0.06 414.01 10.490.000.965.251.2798.99 414.01 5.25 413.89414.01414.53 22.75 22.50 413.8911.50 11.49 418.11 153.77 146.75 413.8911.50 11.49 206Pb/238U concordant scans 58 175 07ADw 711A 86908_86 278175 1.59 0.504930.02069 0.066720.00171 0.02 415.91 8.42 0.02 0.88 4.21 1.01 102.17 415.91 4.21 416.38415.91415.03 14.01 13.91 416.3810.35 10.35 407.55 94.98 92.25416.3810.35 10.35 206Pb/238U concordant scans 107177 07ADw711A86908_53352 6850.510.51548 0.020950.066670.00161 0.01 418.02 8.08 0.51 0.48 4.04 0.97 91.37418.024.04 416.07 418.02 422.13 14.08 13.99416.079.769.75 455.3993.45 90.80 416.079.769.75 206Pb/238U concordant scans 94 178 07ADw711A86908_98494 2312.140.515350.01888 0.067000.00178 0.09 419.67 8.56 0.26 0.61 4.28 1.02 94.14419.674.28 418.03 419.67 422.04 12.69 12.61418.03 10.73 10.72 444.03 83.76 81.63418.0310.73 10.72 206Pb/238U concordant scans 97 175 07ADw711A 86908_100 316296 1.07 0.528070.027460.06690 0.00194 0.09 420.95 10.281.580.215.141.2283.28 420.95 5.14 417.43 420.95430.53 18.33 18.17 417.43 11.70 11.69 501.22118.38 114.15 417.43 11.7011.69 206Pb/238U concordant scans 46 174 07ADw711A 86908_102 403118 3.43 0.514970.019160.06818 0.00180 0.10 423.80 8.71 0.18 0.67 4.36 1.03 105.45 423.80 4.36 425.19 423.80421.79 12.88 12.80 425.19 10.87 10.87 403.22 84.81 82.63425.1910.87 10.87 206Pb/238U concordant scans 117 177 07ADw711A86908_75137 86 1.59 0.53953 0.030210.067780.001790.03 426.13 9.65 1.85 0.17 4.82 1.13 81.39426.134.82 422.80 426.13 438.12 20.03 19.83422.80 10.82 10.81 519.44 127.55 122.65422.8010.82 10.81 206Pb/238U concordant scans 70 178 07ADw711A86908_9 632489 1.29 0.527960.01780 0.068690.001670.14 429.16 8.21 0.09 0.76 4.11 0.96 96.85429.164.11 428.26429.16430.45 11.86 11.79 428.2610.10 10.09 442.19 77.71 75.87428.2610.10 10.09 206Pb/238U concordant scans 106177 07ADw711A86908_33371 1732.150.53817 0.018190.069600.00162 0.02 435.14 7.52 0.19 0.66 3.76 0.86 95.24435.143.76 433.76 435.14 437.21 12.04 11.97433.769.769.76 455.4478.78 76.89 433.769.769.76 206Pb/238U concordant scans 111178 07ADw711A86908_13310 1112.800.539210.02223 0.070210.00184 0.12 437.58 9.35 0.00 0.95 4.67 1.07 99.29437.584.67 437.40 437.58 437.90 14.72 14.61 437.40 11.09 11.08 440.5396.02 93.23 437.40 11.09 11.08 206Pb/238U concordant scans 102178 07ADw711A86908_62 194 1311.480.55488 0.033750.070250.001820.03 439.66 9.96 0.74 0.39 4.98 1.13 87.08439.664.98 437.66 439.66 448.1922.16 21.92437.66 10.9910.98 502.61 138.78 133.00 437.66 10.99 10.98 206Pb/238U concordant scans 54 178 07ADw 711A 86908_59 544 3151.730.54841 0.017770.07081 0.001660.02 442.28 7.52 0.14 0.71 3.76 0.85 96.07442.283.76 441.05442.28443.96 11.69 11.62 441.059.999.98 459.07 74.35 72.66441.059.999.98 206Pb/238U concordant scans 122178 07ADw711A86908_61335 4130.810.58282 0.028200.07072 0.00195 0.06 447.64 10.155.970.015.081.1373.99 447.64 5.08 440.49 447.64466.27 18.17 18.01 440.49 11.73 11.72 595.30109.96 106.29 440.49 11.7311.72 206Pb/238U concordant scans 31 178 07ADw711A86908_7 149632.390.57090 0.030580.07223 0.00179 0.05 451.52 9.70 0.67 0.41 4.85 1.07 89.19451.524.85 449.58 451.52458.60 19.86 19.67 449.58 10.79 10.78 504.05122.82 118.27 449.58 10.7910.78 206Pb/238U concordant scans 85 178 07ADw711A86908_20347 1692.060.56944 0.022450.07200 0.00197 0.12 451.82 9.72 1.15 0.28 4.86 1.08 88.69451.824.86 448.20 451.82 457.65 14.58 14.47448.20 11.83 11.83 505.3891.75 89.19 448.2011.83 11.83 206Pb/238U concordant scans 88 178 07ADw 711A 86908_19 690419 1.65 0.565930.01828 0.072310.00183 0.14 452.47 8.64 0.51 0.48 4.32 0.95 93.28452.474.32 450.03452.47455.38 11.89 11.82 450.0311.01 11.00 482.47 74.91 73.20450.0311.01 11.00 206Pb/238U concordant scans 117 178 07ADw711A86908_70479 1982.420.57453 0.019080.072300.001750.03 454.59 8.15 1.86 0.17 4.08 0.90 87.26454.594.08 450.02 454.59 460.94 12.34 12.27450.02 10.55 10.54 515.7375.00 73.28 450.02 10.55 10.54 206Pb/238U concordant scans 89 178 07ADw711A 86908_73277 1112.490.56487 0.02203 0.07335 0.001820.02 455.72 8.79 0.03 0.86 4.39 0.96 102.19 455.72 4.39 456.31 455.72 454.69 14.35 14.25456.31 10.93 10.92 446.5489.68 87.24 456.31 10.93 10.92 206Pb/238U concordant scans 104177 07ADw711A86908_26374 155 2.42 0.568400.020010.073410.001850.06 456.81 8.68 0.00 0.97 4.34 0.95 99.62456.814.34 456.69 456.81 456.98 13.00 12.91 456.6911.09 11.08 458.45 83.26 81.15456.6911.09 11.08 206Pb/238U concordant scans 110178 07ADw711A86908_851055757 1.39 0.597720.01808 0.073840.00184 0.04 467.12 8.15 4.44 0.04 4.08 0.87 82.53467.124.08 459.23 467.12 475.79 11.52 11.46 459.23 11.08 11.07 556.4367.90 66.49459.2311.08 11.07 206Pb/238U concordant scans 88 178 07ADw711A86908_47132 66 2.02 0.66736 0.095720.07626 0.00270 0.02 476.64 15.732.180.147.871.6565.45 476.64 7.87 473.79 476.64519.11 59.14 57.47 473.79 16.21 16.19 723.87324.86 294.50 473.79 16.2116.19 206Pb/238U concordant scans 16 178 07ADw711A86908_6 240127 1.89 0.72733 0.026690.08807 0.00197 0.07 547.83 9.72 1.32 0.25 4.86 0.89 90.69547.834.86 544.09 547.83 554.99 15.75 15.63544.09 11.69 11.68 599.9482.01 79.94 544.0911.69 11.68 206Pb/238U concordant scans 106177 07ADw711A86908_8 499519.850.723740.02310 0.087910.00226 0.17 547.88 10.37 1.25 0.26 5.18 0.95 91.58547.885.18 543.16 547.88552.8713.65 13.56543.1613.37 13.36 593.10 72.79 71.16 543.16 13.37 13.36 206Pb/238U concordant scans 104 177 07ADw711A 86908_1 414180 2.29 0.836850.02355 0.099810.00204 0.10 615.20 8.40 0.20 0.66 4.20 0.68 96.97615.204.20 613.31 615.20617.41 13.06 12.98 613.31 11.97 11.96 632.4664.55 63.26613.3111.97 11.96 206Pb/238U concordant scans 115178 07ADw711A86908_79571 5081.120.886130.02642 0.103440.00254 0.03 639.59 10.470.930.345.230.8293.50 639.59 5.23 644.29 639.59 644.29 14.28 14.18634.52 14.85 14.83 678.6665.36 64.03 644.29 14.28 14.18 207Pb/235Uc concordant scans 130176 07ADw711A86908_18411 3111.320.951320.03294 0.107390.00271 0.13 667.02 12.383.780.056.190.9387.69 667.02 6.19 657.55 667.02 678.79 17.21 17.07657.55 15.77 15.75 749.8876.16 74.36 657.55 15.77 15.75 206Pb/238U concordant scans 61 177 07ADw711A 86908_37 139423.321.04104 0.240310.115660.007690.04 707.54 42.280.090.7621.14 2.99 90.05707.5421.14 705.51 707.54 724.43123.21 116.16 705.5144.50 44.34 783.46 536.35 458.04 705.51 44.50 44.34 206Pb/238U concordant scans 3 178 07ADw 711A 86908_68 9512833.55 1.085050.02855 0.122550.00286 0.04 745.73 10.410.010.945.210.7099.53 745.73 5.21 746.09 745.73746.0913.95 13.86 745.2216.42 16.40 748.71 57.31 56.28 746.0913.95 13.86207Pb/235Uc concordant scans 151 178 07ADw 711A 86908_44150 2070.731.28808 0.053400.13475 0.003430.05 824.90 15.522.890.097.760.9489.69 824.90 7.76 814.91824.90840.44 23.84 23.56 814.9119.49 19.46 908.53 88.94 86.47814.9119.49 19.46 206Pb/238U concordant scans 59 178 07ADw711A 86908_96208 1651.271.40442 0.416110.13715 0.01680 0.13 839.59 88.760.420.5244.38 5.29 79.00839.5944.38 828.52 839.59 890.80 183.80 168.53828.52 95.62 94.91 1048.78 668.75 549.64 828.52 95.62 94.91 206Pb/238U concordant scans 1 178 07ADw 711A 86908_56 349176 1.98 1.483360.04290 0.151160.00353 0.04 916.41 12.931.420.236.470.7194.31 916.41 6.47 923.60 916.41923.6017.62 17.47 907.4919.79 19.76 962.29 61.94 60.73 923.6017.62 17.47207Pb/235Uc concordant scans 132 178 07ADw 711A 86908_95 372113 3.30 1.497760.04603 0.151280.00382 0.05 920.21 14.542.360.127.270.7992.62 920.21 7.27 929.47920.21929.47 18.80 18.63 908.1321.43 21.39 980.44 64.24 62.93929.4718.80 18.63 207Pb/235Uc concordant scans 123 177 07ADw711A 86908_25 1033201 5.15 1.512240.04147 0.154320.00382 0.15 931.62 14.170.660.427.080.7696.42 931.62 7.08 935.34931.62935.34 16.83 16.69 925.1321.34 21.30 959.49 58.83 57.73935.3416.83 16.69 207Pb/235Uc concordant scans 161 178 07ADw711A 86908_103 8476014.10 1.532530.04435 0.154160.00396 0.11 936.10 14.642.050.157.320.7893.47 936.10 7.32 943.51 936.10 943.5117.86 17.70924.2222.16 22.12 988.82 59.85 58.71 943.51 17.86 17.70207Pb/235Uc concordant scans 145 174 07ADw 711A 86908_89 363566.511.56730 0.047470.156630.003970.05 949.25 14.751.860.177.370.7893.61 949.25 7.37 957.36 949.25 957.3618.86 18.69938.0222.13 22.09 1002.05 63.23 61.96 957.36 18.86 18.69207Pb/235Uc concordant scans 106 178 07ADw 711A 86908_67 111731.521.66310 0.059600.164770.004060.05 988.79 16.450.530.478.230.8396.42 988.79 8.23 994.56 988.79 994.5622.85 22.60983.2122.51 22.47 1019.67 74.94 73.17 994.56 22.85 22.60207Pb/235Uc concordant scans 89 178 07ADw 711A 86908_97 164562.921.68923 0.055560.165130.004290.06 996.00 16.231.560.218.120.8194.12 996.00 8.12 1004.47 996.001004.47 21.0920.87 985.2223.73 23.69 1046.72 68.84 67.341004.47 21.0920.87 207Pb/235Uc concordant scans 112 174 07ADw 711A 86908_84 298115 2.59 1.756200.05088 0.17164 0.004200.02 1026.1514.76 0.32 0.57 7.38 0.72 97.521026.15 7.38 1029.451026.15 1029.4518.83 18.661021.15 23.1323.09 1047.13 59.95 58.811029.45 18.8318.66 207Pb/235Uc concordant scans 157 178 07ADw 711A 86908_4844 1704.981.876210.11067 0.171510.00359 0.01 1030.7317.68 5.46 0.02 8.84 0.86 86.431030.73 8.84 1020.401030.73 1072.73 39.45 38.701020.40 19.7819.75 1180.67120.41 115.87 1020.4019.78 19.75 206Pb/238U concordant scans 82 178 07ADw711A86908_93991 3083.221.77174 0.048700.172810.004300.04 1032.4314.57 0.27 0.60 7.29 0.71 97.751032.43 7.29 1035.16 1032.43 1035.16 17.92 17.76 1027.57 23.68 23.64 1051.2256.48 55.46 1035.1617.92 17.76 207Pb/235Uc concordant scans 166177 07ADw711A86908_21923 1456.381.907130.14925 0.170210.01047 0.38 1034.7846.49 5.75 0.02 23.252.2582.53 1034.7823.25 1083.58 1034.781083.58 52.81 51.47 1013.28 57.79 57.531227.79 155.42 147.911083.58 52.81 51.47 207Pb/235Uc concordant scans 7 178 07ADw 711A 86908_78 189176 1.07 1.799590.05657 0.173290.00426 0.02 1038.7215.66 0.96 0.33 7.83 0.75 95.661038.72 7.83 1045.311038.72 1045.3120.62 20.41 1030.2223.42 23.38 1076.99 65.25 63.90 1045.3120.62 20.41 207Pb/235Uc concordant scans 138 176 07ADw711A 86908_39345 2361.461.79847 0.048940.17495 0.00397 0.09 1042.6313.20 0.14 0.70 6.60 0.63 98.371042.63 6.60 1044.91 1042.63 1044.91 17.84 17.681039.34 21.78 21.74 1056.5658.71 57.62 1044.9117.84 17.68 207Pb/235Uc concordant scans 151 178 07ADw711A86908_74194 2500.781.86946 0.060180.176190.004380.05 1059.6316.46 2.38 0.12 8.23 0.78 93.411059.63 8.23 1070.34 1059.631070.34 21.41 21.181046.15 24.03 23.98 1119.9666.20 64.801070.34 21.41 21.18 207Pb/235Uc concordant scans 81 178 07ADw711A 86908_40115 1111.041.97183 0.11046 0.17781 0.004710.04 1070.1821.89 5.04 0.02 10.951.0287.37 1070.1810.95 1055.00 1070.18 1105.93 38.10 37.40 1055.0025.79 25.73 1207.54 115.04 110.88 1055.0025.79 25.73 206Pb/238U concordant scans 35 178 07ADw711A 86908_10197 1031.921.98745 0.062360.18511 0.00456 0.14 1104.4717.26 1.16 0.28 8.63 0.78 95.751104.47 8.63 1111.26 1104.47 1111.26 21.31 21.091094.86 24.84 24.79 1143.4965.37 64.01 1111.2621.31 21.09 207Pb/235Uc concordant scans 124 178 07ADw711A86908_72309 74 4.21 2.25889 0.108350.190370.005760.12 1156.5224.61 12.130.0012.30 1.06 83.871156.52 12.30 1123.391156.52 1199.56 34.04 33.481123.39 31.24 31.161339.47 97.3894.36 1123.39 31.24 31.16 206Pb/238U concordant scans 23 178 07ADw711A 86908_3 282 190 1.48 2.194970.062500.19629 0.004220.03 1168.8514.82 2.44 0.12 7.41 0.63 94.401168.85 7.41 1179.45 1168.85 1179.45 19.96 19.77 1155.3522.78 22.74 1223.93 59.49 58.36 1179.45 19.96 19.77 207Pb/235Uc concordant scans 88 178 07ADw711A86908_83 280 1681.672.51680 0.071950.217050.005360.04 1273.2217.17 0.38 0.54 8.58 0.67 97.791273.22 8.58 1276.901273.22 1276.90 20.88 20.67 1266.2428.44 28.38 1294.87 57.12 56.07 1276.9020.88 20.67 207Pb/235Uc concordant scans 144178 07ADw711A86908_81190 94 2.03 2.624580.07707 0.220020.00541 0.06 1298.3417.85 2.15 0.14 8.93 0.69 94.981298.34 8.93 1307.55 1298.34 1307.55 21.70 21.481281.99 28.60 28.54 1349.7157.97 56.89 1307.5521.70 21.48 207Pb/235Uc concordant scans 130 178 07ADw711A86908_42213 88 2.43 2.73889 0.110070.22268 0.00575 0.13 1317.4122.90 4.67 0.03 11.450.8792.01 1317.4111.45 1339.08 1317.411339.08 30.12 29.67 1296.02 30.35 30.28 1408.5878.63 76.641339.08 30.12 29.67 207Pb/235Uc concordant scans 30 178 07ADw711A86908_76275 2071.332.756790.07690 0.228110.00561 0.05 1337.5717.47 1.20 0.27 8.73 0.65 96.351337.57 8.73 1343.931337.57 1343.93 20.89 20.681324.61 29.49 29.421374.82 55.1654.17 1343.93 20.89 20.68 207Pb/235Uc concordant scans 143177 07ADw711A86908_101 426 191 2.24 2.936570.08347 0.239710.00616 0.11 1389.5818.79 0.11 0.74 9.39 0.68 98.881389.58 9.39 1391.391389.58 1391.3921.64 21.42 1385.2032.06 31.98 1400.89 55.33 54.34 1391.3921.64 21.42 207Pb/235Uc concordant scans 143 178 07ADw711A 86908_6696129 0.74 3.129980.09840 0.247440.00590 0.01 1434.3119.11 0.58 0.45 9.55 0.67 97.481434.31 9.55 1440.091434.31 1440.09 24.34 24.051425.24 30.5330.46 1462.10 62.07 60.82 1440.0924.34 24.05 207Pb/235Uc concordant scans 137178 07ADw711A86908_91243 1062.293.15150 0.090630.249550.00620 0.03 1442.4018.57 0.23 0.63 9.28 0.64 98.431442.40 9.28 1445.37 1442.40 1445.37 22.29 22.05 1436.14 32.02 31.94 1458.9756.22 55.20 1445.3722.29 22.05 207Pb/235Uc concordant scans 153176 07ADw711A86908_45636 3162.013.341850.08378 0.256460.00576 0.16 1484.4815.17 1.02 0.31 7.59 0.51 96.931484.48 7.59 1490.891484.48 1490.89 19.69 19.501471.69 29.59 29.521518.31 49.8449.03 1490.8919.69 19.50 207Pb/235Uc concordant scans 156 178 07ADw711A 86908_17206 1951.063.41090 0.099770.25734 0.00619 0.10 1496.6519.60 2.69 0.10 9.80 0.65 95.221496.65 9.80 1506.91 1496.651506.91 23.10 22.841476.21 31.80 31.72 1550.34 58.01 56.91 1506.9123.10 22.84 207Pb/235Uc concordant scans 120 178 07ADw711A86908_2714271434 0.99 3.390710.088760.25948 0.00638 0.09 1498.2318.19 0.66 0.42 9.09 0.61 97.611498.23 9.09 1502.25 1498.23 1502.25 20.63 20.42 1487.18 32.69 32.61 1523.5852.80 51.90 1502.2520.63 20.42 207Pb/235Uc concordant scans 159 178 07ADw711A86908_58144 79 1.82 4.04440 0.537220.277660.017150.10 1602.5171.71 0.91 0.34 35.862.2491.54 1602.5135.86 1579.541602.51 1643.17 111.12 105.36 1579.54 86.85 86.26 1725.56 260.76 239.801579.54 86.85 86.26 206Pb/238U concordant scans 3178 07ADw711A86908_55186 2220.843.925490.10615 0.281290.00645 0.05 1612.0917.83 1.10 0.29 8.91 0.55 97.051612.09 8.91 1618.95 1612.091618.95 22.00 21.77 1597.8832.50 32.42 1646.46 52.54 51.64 1618.9522.00 21.77 207Pb/235Uc concordant scans 144178 07ADw711A86908_50395 4440.894.08535 0.122800.27452 0.00700 0.09 1623.1221.40 18.010.0010.70 0.66 88.611623.12 10.70 1651.381623.12 1651.38 24.67 24.371563.71 35.46 35.36 1764.8057.78 56.681651.38 24.67 24.37 207Pb/235Uc concordant scans 30 178 07ADw711A 86908_12165 178 0.93 4.081250.11961 0.28685 0.007360.16 1643.9921.60 1.49 0.22 10.800.6696.64 1643.9910.80 1650.56 1643.99 1650.56 24.04 23.76 1625.7636.94 36.84 1682.28 57.51 56.43 1650.56 24.04 23.76 207Pb/235Uc concordant scans 125178 07ADw 711A 86908_32 279 1721.624.157110.12239 0.286320.00761 0.20 1655.2122.29 4.33 0.04 11.140.6794.39 1655.2111.14 1665.61 1655.211665.61 24.2423.96 1623.1138.20 38.091719.61 56.33 55.281665.61 24.2423.96 207Pb/235Uc concordant scans129 178 07ADw711A86908_99101 72 1.41 4.561770.154910.30432 0.00811 0.11 1732.8624.41 1.61 0.20 12.210.7096.33 1732.8612.21 1742.31 1732.861742.31 28.48 28.091712.71 40.16 40.04 1778.02 63.52 62.19 1742.3128.48 28.09 207Pb/235Uc concordant scans 103 176 07ADw711A86908_80138 1720.804.75065 0.192960.301430.008340.13 1744.4828.44 9.62 0.00 14.220.8290.88 1744.4814.22 1776.221744.48 1776.22 34.36 33.791698.42 41.35 41.22 1868.9375.19 73.331776.22 34.36 33.79 207Pb/235Uc concordant scans 24 178 07ADw711A 86908_15143 1470.974.99021 0.36782 0.31391 0.019050.47 1807.6761.27 1.86 0.17 30.631.6993.39 1807.6730.63 1817.66 1807.67 1817.66 63.33 61.41 1759.9493.79 93.12 1884.48 126.85 121.64 1817.66 63.33 61.41 207Pb/235Uc concordant scans 12 178 07ADw 711A 86908_90 149 74 2.01 4.988160.14344 0.320520.008100.05 1810.5921.34 1.21 0.27 10.670.5997.08 1810.5910.67 1817.321810.59 1817.3224.47 24.18 1792.2539.61 39.49 1846.1753.58 52.631817.32 24.4724.18 207Pb/235Uc concordant scans 136 178 07ADw 711A 86908_54 97 1150.845.073590.15000 0.321690.00750 0.03 1820.5420.56 2.23 0.14 10.280.5696.14 1820.5410.28 1831.701820.54 1831.70 25.23 24.921798.00 36.6336.52 1870.23 55.58 54.55 1831.7025.23 24.92 207Pb/235Uc concordant scans 131178 07ADw711A86908_35131 1580.835.21008 0.145060.322810.007510.03 1838.5119.84 5.23 0.02 9.92 0.54 94.341838.51 9.92 1854.27 1838.51 1854.27 23.86 23.58 1803.46 36.63 36.52 1911.7352.79 51.871854.27 23.8623.58 207Pb/235Uc concordant scans 87 178 07ADw711A86908_1472900.805.28088 0.152900.333120.008240.10 1862.5821.99 0.30 0.58 11.000.5998.62 1862.5811.00 1865.781862.58 1865.78 24.87 24.571853.49 39.90 39.781879.49 56.6555.58 1865.78 24.87 24.57 207Pb/235Uc concordant scans 142176 07ADw711A 86908_36531 144 3.70 5.449800.140220.32765 0.007520.06 1873.7018.64 8.94 0.00 9.32 0.50 92.951873.70 9.32 1892.72 1873.70 1892.72 22.20 21.96 1826.9936.55 36.45 1965.61 48.57 47.78 1892.7222.20 21.96 207Pb/235Uc concordant scans 106 178 07ADw711A86908_92550 5211.065.52110 0.148400.337030.008380.01 1895.9520.25 1.83 0.18 10.130.5396.59 1895.9510.13 1903.89 1895.951903.89 23.24 22.981872.34 40.45 40.32 1938.4449.36 48.551903.89 23.24 22.98 207Pb/235Uc concordant scans 149178 07ADw711A 86908_104 197342 0.58 5.577610.16010 0.34033 0.008840.14 1907.1822.72 1.11 0.29 11.360.6097.37 1907.1811.36 1912.65 1907.18 1912.65 24.87 24.57 1888.2642.59 42.45 1939.20 51.78 50.88 1912.65 24.87 24.57 207Pb/235Uc concordant scans 137173 07ADw711A86908_69 362 59 6.16 5.597900.146510.339950.008000.01 1908.1019.61 1.72 0.19 9.80 0.51 96.861908.10 9.80 1915.78 1908.10 1915.78 22.67 22.42 1886.4438.53 38.41 1947.6848.28 47.50 1915.78 22.67 22.42 207Pb/235Uc concordant scans 142178 07ADw 711A 86908_65 157901.735.694850.15156 0.344250.008050.03 1924.1819.64 1.06 0.30 9.82 0.51 97.501924.18 9.82 1930.59 1924.18 1930.59 23.12 22.861907.08 38.66 38.54 1955.9249.69 48.86 1930.5923.12 22.86 207Pb/235Uc concordant scans 144 177 07ADw711A86908_24975 57 17.115.97774 0.161900.355230.008820.16 1969.9621.99 0.34 0.56 10.990.5698.65 1969.9610.99 1972.611969.96 1972.61 23.70 23.421959.50 42.00 41.861986.38 50.4449.59 1972.61 23.70 23.42 207Pb/235Uc concordant scans 160178 07ADw711A 86908_6455481.156.15918 0.18684 0.357630.00866 0.06 1990.7123.05 1.35 0.25 11.520.5897.21 1990.7111.52 1998.68 1990.71 1998.68 26.67 26.33 1970.9441.18 41.05 2027.48 55.43 54.40 1998.68 26.67 26.33 207Pb/235Uc concordant scans 129178 07ADw711A86908_82 171 83 2.05 9.566590.948060.431800.028650.23 2369.8683.09 1.32 0.25 41.551.7593.95 2369.8641.55 2393.97 2369.86 2393.9793.21 89.12 2313.84 129.65 128.35 2462.87 174.08 164.18 2393.9793.21 89.12 207Pb/235Uc concordant scans 3 178 07ADw 711A 86908_43948 6071.5612.70207 0.310070.49969 0.01122 0.26 2646.8118.66 2.40 0.12 9.33 0.35 97.032646.81 9.33 2657.81 2646.812657.81 23.11 22.852612.45 48.32 48.14 2692.52 42.78 42.15 2657.8123.11 22.85 207Pb/235Uc concordant scans 161 178 07ADw711A86908_57539 8730.6212.65646 0.317600.502300.011540.07 2648.0520.95 1.18 0.28 10.480.4097.97 2648.0510.48 2654.432648.05 2654.43 23.75 23.482623.66 49.61 49.42 2677.9643.12 42.482654.43 23.75 23.48 207Pb/235Uc concordant scans 166177 07ADw711A 86908_38361 1262.86 14.038660.34252 0.51889 0.011460.21 2738.7619.37 3.96 0.05 9.68 0.35 96.402738.76 9.68 2752.32 2738.762752.32 23.26 23.00 2694.4648.73 48.552795.04 42.9342.29 2752.32 23.26 23.00 207Pb/235Uc concordant scans 146177 07ADw711A86908_31 104 80 1.30 14.174810.372630.51662 0.012030.01 2746.1522.87 7.26 0.01 11.440.4295.28 2746.1511.44 2761.47 2746.15 2761.47 25.09 24.78 2684.8451.25 51.05 2817.9745.60 44.88 2761.47 25.09 24.78 207Pb/235Uc concordant scans 122178 07ADw711A86908_87360 3001.2014.29789 0.380240.52100 0.01283 0.01 2757.5723.35 4.90 0.03 11.680.4295.92 2757.5711.68 2769.68 2757.572769.68 25.40 25.08 2703.44 54.49 54.26 2818.3044.65 43.962769.68 25.40 25.08 207Pb/235Uc concordant scans 145178 07ADw711A 86908_88 209 113 1.85 2.73066 0.37467 0.20162 0.01706 0.17 1243.43 75.92 5.68 0.02 37.96 3.05 74.43 1243.43 37.96 1336.84 1243.43 1336.84 104.62 99.50 1184.04 91.84 91.19 1590.71 277.29 253.85 1336.84 104.62 99.50 207Pb/235Uc concordant scans 2 178

09PH160A: Sheep Creek Formation (originally published in Malkowski (2010)) 09PH160A 09PH160A-80 230 3.48 2.24889 4.16841 0.18252 3.61149 0.87 1211.31 57.53 41.91 0.00 28.76 2.37 76.54 1211.31 28.76 1411.96 1211.31 1196.44 29.31 39.83 1411.96 39.83 39.83 1411.96 39.83 39.83 09PH160A 09PH160A-12 93 22 4.19 0.465659.17936 0.069020.76050 0.08 430.126.342.120.153.170.74297.87 430.123.17 430.26430.12388.18 29.62 214.97 144.44 214.97 214.97 430.263.173.17 09PH160A 09PH160A-49201 1741.150.496574.78293 0.069672.437730.51431.21 20.223.180.0710.11 2.34 159.64 431.2110.11 434.14 431.21 409.3716.12 94.36271.95 94.36 94.36434.1410.2310.23 09PH160A 09PH160A-53244 1571.560.51780 5.108190.069882.228690.44434.6518.66 0.54 0.46 9.33 2.15 120.84 434.65 9.33 435.41 434.65 423.68 17.70 103.76 360.32 103.76 103.76 435.419.389.38 09PH160A 09PH160A-73240 89 2.68 0.523673.17352 0.07027 2.30023 0.72 434.8718.97 1.69 0.19 9.49 2.18 117.29 434.87 9.49 437.76 434.87 427.6011.08 49.21 373.21 49.21 49.21 437.769.749.74 09PH160A09PH160A-28356 2381.500.529233.43262 0.070001.717950.50435.7414.40 0.21 0.64 7.20 1.65 107.55 435.74 7.20 436.13435.74431.30 12.06 66.51 405.5266.51 66.51 436.137.247.24 09PH160A 09PH160A-56 216123 1.75 0.531913.69906 0.070552.79654 0.76 437.4223.10 0.53 0.47 11.552.64110.08 437.42 11.55 439.46 437.42433.0813.04 54.27 399.2154.27 54.27 439.4611.8811.88 09PH160A 09PH160A-21223 1411.580.541333.44495 0.070291.76517 0.51 438.03 14.860.020.907.431.7098.08 438.037.43 437.92 438.03 439.3012.29 65.76 446.50 65.76 65.76437.927.477.47 09PH160A 09PH160A-4 7011837.97 0.53934 2.297320.071522.083590.91438.17 16.353.710.058.181.87111.41438.178.18445.31438.17 437.99 8.17 21.68 399.68 21.68 21.68 445.318.978.97 09PH160A 09PH160A-60422 4890.860.53873 2.20886 0.07069 1.47368 0.67 439.8212.36 0.21 0.64 6.18 1.40 104.07 439.82 6.18 440.33 439.82 437.58 7.85 36.73423.12 36.73 36.73 440.33 6.27 6.27 09PH160A 09PH160A-31 573288 1.99 0.559493.90653 0.071512.05409 0.53 445.7017.58 0.24 0.63 8.79 1.97 92.44 445.708.79445.24 445.70451.2014.23 73.44 481.67 73.4473.44 445.248.848.84 09PH160A 09PH160A-71934 1027 0.91 0.553712.48512 0.071032.21935 0.89 446.10 17.871.370.248.942.0093.42 446.108.94 442.36 446.10 447.438.9924.74 473.53 24.74 24.74442.369.499.49 09PH160A 09PH160A-9 233191 1.22 0.54021 2.699550.072520.786890.29450.956.861.930.163.430.76121.26450.953.43 451.31 450.95438.569.6158.14 372.18 58.14 58.14451.313.433.43 09PH160A 09PH160A-10180 1151.560.52793 3.639090.07295 1.19757 0.33 452.93 10.463.850.055.231.15148.11 452.93 5.23 453.93 452.93 430.43 12.7778.30 306.49 78.30 78.30 453.935.255.25 09PH160A09PH160A-36107 84 1.27 0.529775.64625 0.07417 0.94120 0.17 460.918.38 2.34 0.13 4.19 0.91 166.68 460.914.19461.24 460.91431.6619.86 127.57 276.72 127.57127.57 461.244.194.19 09PH160A 09PH160A-6286422.060.573387.85870 0.077913.86414 0.49 480.98 35.570.850.3617.78 3.70 140.26 480.9817.78 483.64 480.98 460.2029.09 154.97344.81154.97154.97483.64 18.00 18.00 09PH160A 09PH160A-65145 1391.040.96036 2.915670.11179 1.79661 0.62 683.19 22.670.000.9711.34 1.66 99.76 683.19 11.34683.11683.19 683.48 14.5049.03 684.75 49.03 49.03 683.11 11.64 11.64 09PH160A 09PH160A-14255 1112.300.96498 2.14999 0.11202 1.41896 0.66 684.8517.83 0.03 0.86 8.91 1.30 99.11 684.85 8.91 684.44 684.85 685.88 10.7234.44 690.60 34.44 34.44 684.449.219.21 09PH160A09PH160A-9786352.460.984952.55345 0.113391.70459 0.67 693.4921.62 0.14 0.71 10.811.5697.76 693.49 10.81692.39693.49696.1412.87 40.43 708.26 40.43 40.43 692.39 11.19 11.19 09PH160A 09PH160A-54 4575 96.581.19227 2.819440.13159 2.59755 0.92 797.05 29.770.000.9914.88 1.87 99.97797.0514.88 796.95797.05797.01 15.57 23.00 797.1723.00 23.00 796.95 19.47 19.47 09PH160A 09PH160A-82 69 32 2.13 1.510342.263730.15732 1.66750 0.74 937.43 26.390.490.4813.20 1.41 102.66 937.43 13.20 917.43937.43934.58 13.83 31.49 917.4331.49 31.49 917.43 31.49 31.49 09PH160A 09PH160A-59 125442.851.58124 3.414950.16190 3.24005 0.95 958.11 35.330.160.6917.66 1.84 101.53 958.11 17.66 952.72958.11962.86 21.24 22.07 952.7222.07 22.07 952.72 22.07 22.07 09PH160A 09PH160A-100262 93 2.81 1.625012.206920.16497 2.01713 0.91 977.20 25.990.300.5812.99 1.33 101.47 977.20 12.99 970.05977.20979.93 13.87 18.25 970.0518.25 18.25 970.05 18.25 18.25 09PH160A 09PH160A-91 279574.871.74349 2.405560.17280 2.13452 0.89 1023.6530.12 0.08 0.78 15.061.47100.851023.65 15.06 1018.831023.65 1024.76 15.52 22.451018.83 22.4522.45 1018.83 22.45 22.45 09PH160A 09PH160A-99205 71 2.89 1.78878 2.888570.175112.643990.921042.17 34.570.010.9217.29 1.66 99.651042.17 17.291043.85 1042.17 1041.38 18.82 23.49 1043.85 23.49 23.49 1043.8523.49 23.49 09PH160A 09PH160A-72280 99 2.82 1.820231.31843 0.176641.00244 0.76 1051.6216.99 0.42 0.52 8.49 0.81 98.78 1051.62 8.49 1061.48 1051.621052.77 8.64 17.24 1061.48 17.24 17.24 1061.4817.24 17.24 09PH160A 09PH160A-46635 1863.411.970241.74954 0.186421.71833 0.98 1110.7612.96 0.30 0.58 6.48 0.58 99.08 1110.76 6.48 1112.18 1110.761105.39 11.78 6.57 1112.186.576.57 1112.186.576.57 09PH160A 09PH160A-7072233.112.02309 2.778670.189681.120900.401120.18 22.510.040.8411.25 1.00 99.06 1120.18 11.251130.33 1120.18 1123.30 18.88 50.66 1130.3350.66 50.66 1130.33 50.66 50.66 09PH160A 09PH160A-85 285117 2.43 2.040631.89044 0.191001.74483 0.92 1130.9822.77 0.09 0.76 11.381.0199.39 1130.9811.38 1133.75 1130.981129.17 12.88 14.471133.75 14.47 14.47 1133.75 14.47 14.47 09PH160A 09PH160A-52295 97 3.03 2.18710 2.195780.201052.096630.951172.44 22.800.190.6611.40 0.97 100.98 1172.44 11.401169.50 1172.441176.94 15.30 12.941169.50 12.94 12.94 1169.5012.9412.94 09PH160A 09PH160A-8870411.692.17917 1.58116 0.19977 1.215390.771174.36 21.900.000.9710.95 0.93 99.92 1174.3610.95 1175.06 1174.361174.41 11.01 20.01 1175.0620.01 20.011175.06 20.0120.01 09PH160A 09PH160A-92 167 77 2.16 2.247672.069920.206491.914210.92 1185.0125.32 2.18 0.14 12.661.07 103.36 1185.01 12.66 1170.791185.01 1196.0614.55 15.61 1170.7915.61 15.61 1170.7915.6115.61 09PH160A 09PH160A-75309 95 3.25 2.212101.80667 0.20173 1.755630.97 1185.2215.94 0.00 0.97 7.97 0.67 99.94 1185.227.971185.371185.22 1184.8812.63 8.41 1185.378.418.41 1185.378.418.41 09PH160A 09PH160A-47154 1071.442.26945 1.85067 0.20470 1.12575 0.61 1201.5222.73 0.04 0.84 11.370.95 99.46 1201.5211.37 1207.02 1201.52 1202.8413.04 28.931207.02 28.93 28.93 1207.02 28.93 28.93 09PH160A 09PH160A-96377 92 4.09 2.33683 1.507810.208541.426100.95 1226.0216.81 0.14 0.71 8.40 0.69 99.44 1226.028.401227.961226.02 1223.5610.72 9.62 1227.969.629.62 1227.969.629.62 09PH160A 09PH160A-1763163.962.48689 2.20384 0.21782 1.15600 0.52 1269.6825.06 0.02 0.88 12.530.99100.46 1269.6812.53 1264.581269.68 1268.2215.96 36.651264.58 36.6536.65 1264.58 36.65 36.65 09PH160A 09PH160A-26104 49 2.12 2.609092.02201 0.223781.74246 0.86 1303.6828.72 0.02 0.90 14.361.1099.73 1303.68 14.36 1305.421303.68 1303.20 14.8419.92 1305.4219.92 19.92 1305.42 19.92 19.92 09PH160A 09PH160A-74 198712.792.77454 1.478130.23425 1.38618 0.94 1341.6317.59 1.08 0.30 8.79 0.66 101.55 1341.638.79 1336.00 1341.63 1348.71 11.03 9.92 1336.009.929.92 1336.009.929.92 09PH160A 09PH160A-23 430185 2.33 2.857891.05715 0.237540.88241 0.83 1370.2415.80 0.23 0.63 7.90 0.58 100.561370.247.901366.181370.24 1370.897.9511.21 1366.1811.21 11.21 1366.18 11.21 11.21 09PH160A 09PH160A-1230 66 3.47 2.833291.639150.23309 1.59315 0.97 1381.0814.35 2.86 0.09 7.18 0.52 97.451381.087.18 1385.96 1381.081364.40 12.30 7.40 1385.967.407.40 1385.967.407.40 09PH160A 09PH160A-51283 1451.962.93874 2.250910.241642.194290.97 1387.8918.84 0.08 0.78 9.42 0.68 100.60 1387.899.421386.891387.89 1391.9517.05 9.63 1386.899.639.63 1386.899.639.63 09PH160A 09PH160A-57138 44 3.13 2.91801 1.852600.238041.623260.88 1391.2626.26 0.94 0.33 13.130.9498.17 1391.2613.13 1402.161391.26 1386.5914.01 17.111402.16 17.1117.11 1402.1617.11 17.11 09PH160A 09PH160A-81202 1391.452.934761.47172 0.235911.39837 0.95 1416.3615.88 11.240.007.940.5695.47 1416.367.941430.261416.36 1390.9211.15 8.76 1430.268.768.76 1430.26 8.76 8.76 09PH160A 09PH160A-43289 1152.523.13481 1.300260.25162 1.14611 0.88 1438.53 18.640.510.479.320.65100.96 1438.539.321433.061438.53 1441.2810.01 11.721433.06 11.7211.72 1433.06 11.7211.72 09PH160A 09PH160A-6856960.583.161882.68080 0.252951.53253 0.57 1451.0235.96 0.09 0.76 17.981.24100.991451.02 17.98 1439.421451.02 1447.90 20.68 41.931439.42 41.9341.93 1439.42 41.93 41.93 09PH160A 09PH160A-6167302.233.21643 3.304720.249122.803050.851470.02 49.131.900.1724.57 1.67 95.54 1470.02 24.571500.83 1470.021461.12 25.6033.09 1500.8333.09 33.09 1500.83 33.09 33.09 09PH160A 09PH160A-692442.063.33117 1.410150.25814 1.25330 0.89 1492.8219.94 0.89 0.34 9.97 0.67 98.691492.829.971499.911492.82 1488.39 11.0112.22 1499.9112.22 12.22 1499.91 12.22 12.22 09PH160A 09PH160A-27 65 39 1.66 3.442851.709680.26539 1.51108 0.88 1512.5924.51 0.08 0.77 12.260.81100.49 1512.59 12.261509.89 1512.591514.24 13.45 15.10 1509.89 15.10 15.10 1509.8915.1015.10 09PH160A 09PH160A-63193 1431.353.617352.88803 0.274442.83573 0.98 1541.5220.79 0.33 0.57 10.390.67 101.52 1541.5210.39 1539.871541.52 1553.35 22.98 10.291539.87 10.29 10.291539.8710.29 10.29 09PH160A 09PH160A-69280 1461.913.55297 1.54755 0.26850 1.484410.961545.04 15.830.400.537.920.51 99.10 1545.047.921547.18 1545.041539.10 12.26 8.22 1547.188.228.22 1547.188.228.22 09PH160A 09PH160A-304248 0.87 3.80166 2.631710.284701.348830.511605.87 34.841.200.2717.42 1.08 103.25 1605.87 17.42 1564.201605.87 1593.1021.16 42.37 1564.2042.37 42.37 1564.20 42.37 42.37 09PH160A 09PH160A-55 39 42 0.93 3.890032.28927 0.286621.68109 0.73 1612.3136.98 0.62 0.43 18.491.15101.881612.31 18.49 1594.66 1612.31 1611.61 18.49 29.021594.66 29.02 29.02 1594.6629.02 29.02 09PH160A 09PH160A-5078531.473.953082.82006 0.287792.61630 0.93 1619.9535.13 0.10 0.75 17.561.08 100.83 1619.9517.56 1617.011619.95 1624.62 22.86 19.601617.01 19.60 19.601617.0119.60 19.60 09PH160A 09PH160A-7661960.634.04170 2.194510.28949 1.487530.681641.80 35.050.050.82 17.53 1.07 99.50 1641.8017.53 1647.26 1641.80 1642.63 17.86 29.92 1647.2629.92 29.92 1647.26 29.92 29.92 09PH160A 09PH160A-9051331.524.130572.72987 0.297932.53865 0.93 1643.9534.04 1.21 0.27 17.021.04102.861643.9517.02 1634.341643.95 1660.3722.32 18.651634.34 18.6518.65 1634.34 18.65 18.65 09PH160A 09PH160A-15 98 1180.834.114982.07224 0.294311.96521 0.95 1652.0823.01 0.17 0.68 11.500.70100.791652.0811.50 1649.98 1652.081657.28 16.93 12.191649.98 12.19 12.191649.98 12.19 12.19 09PH160A 09PH160A-79107 35 3.04 4.01851 2.653360.286692.589540.981652.27 20.920.590.4410.46 0.63 98.21 1652.27 10.461654.63 1652.271637.95 21.58 10.72 1654.63 10.72 10.72 1654.6310.72 10.72 09PH160A 09PH160A-93319 30 10.484.090082.16031 0.291932.13775 0.99 1653.7112.53 0.01 0.93 6.26 0.38 99.84 1653.71 6.26 1653.811653.71 1652.33 17.63 5.77 1653.815.775.77 1653.815.775.77 09PH160A 09PH160A-8664371.704.09720 2.209070.296641.027300.471667.28 27.831.450.2313.91 0.83 102.91 1667.28 13.911627.29 1667.281653.75 18.03 36.371627.29 36.37 36.37 1627.2936.3736.37 09PH160A 09PH160A-78 102651.584.16632 1.237310.294930.955560.77 1667.5220.35 0.02 0.88 10.170.6199.82 1667.5210.17 1669.071667.52 1667.4210.13 14.54 1669.0714.5414.54 1669.07 14.54 14.54 09PH160A 09PH160A-795422.274.32408 1.506060.30280 1.31213 0.87 1694.4622.70 0.44 0.51 11.350.67100.961694.46 11.35 1689.05 1694.46 1697.96 12.42 13.641689.05 13.64 13.64 1689.0513.64 13.64 09PH160A 09PH160A-9880332.464.550751.72444 0.310221.531230.89 1739.4525.00 0.01 0.91 12.500.72 100.19 1739.4512.50 1738.491739.45 1740.30 14.36 14.541738.49 14.54 14.541738.4914.54 14.54 09PH160A 09PH160A-22282 1621.744.71890 1.28257 0.30764 1.212110.951805.54 14.5020.74 0.00 7.25 0.40 95.01 1805.547.25 1819.92 1805.541770.60 10.75 7.61 1819.927.617.61 1819.927.617.61 09PH160A 09PH160A-8 48 49 0.97 4.943082.43736 0.325441.46390 0.60 1811.9838.73 0.11 0.74 19.361.07 100.791811.98 19.36 1802.021811.98 1809.6420.59 35.45 1802.0235.45 35.45 1802.02 35.45 35.45 09PH160A 09PH160A-29 175712.465.03377 1.450520.32997 1.41087 0.97 1812.3713.06 1.43 0.23 6.53 0.36 101.56 1812.376.53 1809.94 1812.37 1825.02 12.29 6.12 1809.946.126.12 1809.946.126.12 09PH160A 09PH160A-94243 87 2.79 5.201851.65002 0.338061.60772 0.97 1829.5414.36 3.57 0.06 7.18 0.39 102.83 1829.547.181825.591829.54 1852.92 14.05 6.73 1825.596.736.73 1825.59 6.73 6.73 09PH160A 09PH160A-6753660.805.079142.00908 0.326371.57872 0.79 1834.6933.67 0.56 0.45 16.830.9298.63 1834.69 16.83 1846.101834.69 1832.6317.05 22.48 1846.1022.48 22.48 1846.10 22.48 22.48 09PH160A 09PH160A-18 102601.695.07659 2.797190.32638 2.65201 0.95 1842.0230.22 0.29 0.59 15.110.8298.68 1842.0215.11 1845.16 1842.02 1832.20 23.73 16.091845.16 16.09 16.09 1845.1616.09 16.09 09PH160A 09PH160A-48128 87 1.48 5.296862.34551 0.336032.27521 0.97 1869.1120.50 0.00 0.97 10.250.5599.91 1869.11 10.25 1869.221869.11 1868.3620.04 10.28 1869.2210.28 10.28 1869.22 10.28 10.28 09PH160A 09PH160A-392481.935.68702 1.674680.35360 1.51014 0.90 1915.6123.76 2.56 0.11 11.880.62102.431915.61 11.881905.46 1915.61 1929.40 14.46 13.00 1905.46 13.00 13.00 1905.4613.00 13.00 09PH160A 09PH160A-8399701.425.765802.18097 0.342402.08588 0.96 1978.6521.46 6.18 0.01 10.730.5495.51 1978.6510.73 1987.551978.65 1941.29 18.87 11.331987.55 11.33 11.331987.55 11.3311.33 09PH160A 09PH160A-4517134 0.13 6.036104.10620 0.361632.55503 0.62 1983.2169.34 0.06 0.80 34.671.75100.921983.21 34.67 1971.84 1983.21 1981.07 35.78 57.30 1971.8457.30 57.30 1971.84 57.30 57.30 09PH160A 09PH160A-4033152.209.12950 1.801170.442041.592410.88 2346.4826.75 0.22 0.64 13.370.57 100.692346.48 13.37 2343.532346.48 2351.07 16.48 14.40 2343.5314.40 14.40 2343.53 14.40 14.40 09PH160A 09PH160A-35 39 26 1.50 9.416711.470380.43994 1.27216 0.87 2393.1822.79 3.70 0.05 11.390.4897.75 2393.1811.39 2404.43 2393.18 2379.46 13.50 12.532404.43 12.53 12.53 2404.4312.53 12.53 09PH160A 09PH160A-44166 187 0.89 13.26461 2.228070.520572.217291.00 2696.529.860.010.924.930.18100.19 2696.52 4.93 2696.45 2696.522698.67 21.04 3.62 2696.453.623.62 2696.453.623.62

11AD2A: Sheep Creek Formation 11AD2A 12212AZ1_97879 4731.860.41767 0.022470.05492 0.00268 0.40 349.613.61.190.28 6.8 3.982.34 349.6 41.2 344.67 349.6 354.38 16.16 16.03 344.6716.41 16.39 418.61128.31 123.38344.6716.41 16.39 206Pb/238U concordant scans 113 171 11AD2A 12212AZ1_4861 6591.310.46785 0.026150.06080 0.00313 0.49 385.516.00.960.33 8.0 4.285.47 385.5 42.7 380.46 385.5 389.70 18.1718.01 380.4619.03 19.01 445.12 123.78 119.18 380.46 19.03 19.01 206Pb/238U concordant scans 108 171 11AD2A 12212AZ1_88353 2061.710.48541 0.030440.06331 0.00336 0.48 398.617.70.330.57 8.9 4.490.59 398.6 45.3 395.75 398.6 401.78 20.9220.70 395.7520.37 20.34 436.87 135.93 130.41 395.75 20.37 20.34 206Pb/238U concordant scans 86 171 11AD2A12212AZ1_62255 74 3.45 0.50239 0.022920.066000.001830.27 412.410.00.020.87 5.0 2.497.86 412.4 48.9 412.02 412.4 413.3215.55 15.43412.02 11.07 11.06421.04 105.87102.50 412.0211.07 11.06 206Pb/238U concordant scans 66 171 11AD2A 12212AZ1_107254 1062.390.50320 0.033250.066400.003180.43 414.217.40.000.96 8.7 4.2100.79414.2 50.4414.42 414.2 413.86 22.5922.34 414.42 19.27 19.24411.16 143.84 137.68 414.42 19.27 19.24 206Pb/238U concordant scans 73 171 11AD2A 12212AZ1_65 276156 1.77 0.510820.030470.06578 0.00326 0.46 414.5 17.2 0.63 0.43 8.6 4.188.20 414.5 44.1 410.66 414.5 419.0020.58 20.38410.6619.71 19.68 465.61 130.16 125.08 410.66 19.71 19.68 206Pb/238U concordant scans 93 171 11AD2A 12212AZ1_9 74 25 3.00 0.51772 0.054590.065830.004530.35 414.625.30.460.50 12.6 6.183.04 414.6 41.5 410.98 414.6 423.63 36.8536.19 410.98 27.42 27.36494.92 237.22 220.84 410.98 27.42 27.36 206Pb/238U concordant scans 63 171 11AD2A 12212AZ1_7 171592.880.50870 0.03851 0.066150.00407 0.37 415.020.90.110.74 10.4 5.092.95 415.0 46.5 412.91 415.0 417.57 26.0825.75 412.91 24.65 24.60 444.22178.42 169.02 412.9124.65 24.60 206Pb/238U concordant scans 80 171 11AD2A 12212AZ1_26 521 1882.770.510500.02811 0.065550.00350 0.52 415.117.40.930.33 8.7 4.286.78 415.1 43.4 409.29 415.1 418.7818.98 18.81 409.29 21.19 21.15 471.67 119.39 115.10 409.29 21.19 21.15 206Pb/238U concordant scans 106171 11AD2A 12212AZ1_91607 2212.740.507300.02345 0.066470.00284 0.32 415.813.40.030.85 6.7 3.297.22 415.8 48.6 414.85 415.8 416.63 15.8615.74 414.85 17.1917.17 426.70 117.69 113.53 414.85 17.19 17.17 206Pb/238U concordant scans 102 171 11AD2A12212AZ1_10527 1393.790.523630.03000 0.067730.00336 0.44 425.117.10.230.63 8.6 4.092.76 425.1 46.4 422.46 425.1 427.57 20.0919.90 422.46 20.2920.26 455.45 128.33 123.39 422.46 20.29 20.26 206Pb/238U concordant scans 86 171 11AD2A 12212AZ1_83459 68 6.73 0.52649 0.032850.068090.003570.50 427.018.80.190.66 9.4 4.493.20 427.0 46.6 424.66 427.0 429.48 21.9721.74 424.66 21.54 21.51455.63 132.09 126.87 424.6621.54 21.51 206Pb/238U concordant scans 94 171 11AD2A 12212AZ1_42 165344.820.53098 0.02841 0.06943 0.00243 0.30 432.713.10.000.98 6.5 3.0100.24432.7 50.1 432.75 432.7 432.46 18.9318.76 432.75 14.63 14.61 431.72 123.96 119.36 432.7514.63 14.61 206Pb/238U concordant scans 89 171 11AD2A12212AZ1_75287 1821.580.551120.03397 0.070710.00382 0.42 443.219.10.190.66 9.5 4.393.02 443.2 46.5 440.44 443.2 445.73 22.3622.12 440.4423.03 22.99 473.50 141.67 135.67 440.44 23.03 22.99 206Pb/238U concordant scans 100 171 11AD2A12212AZ1_46158 49 3.24 0.547550.02934 0.071390.00161 0.15 444.39.1 0.01 0.91 4.6 2.1101.39444.3 50.7 444.50 444.3 443.3919.34 19.16444.509.699.68 438.42 124.74120.08 444.509.699.68 206Pb/238U concordant scans 74 171 11AD2A 12212AZ1_85 128462.790.55988 0.046450.07138 0.00436 0.42 447.123.60.210.65 11.8 5.391.06 447.1 45.5444.44 447.1 451.45 30.4630.01 444.44 26.25 26.20 488.10 180.91 171.23 444.44 26.25 26.20 206Pb/238U concordant scans 80 171 11AD2A 12212AZ1_5 296108 2.75 0.557020.03223 0.07187 0.00380 0.45 448.718.60.040.85 9.3 4.297.03 448.7 48.5 447.42 448.7 449.59 21.1320.91 447.4222.89 22.85 461.13 131.33 126.16 447.42 22.89 22.85 206Pb/238U concordant scans 95 171 11AD2A12212AZ1_32170 36 4.75 0.56372 0.037850.071810.003920.39 450.220.10.270.60 10.0 4.591.28 450.2 45.6 447.05 450.2 453.9424.73 24.43447.05 23.58 23.54489.77 153.44146.42 447.0523.58 23.54 206Pb/238U concordant scans 93 171 11AD2A 12212AZ1_102312 1043.010.56843 0.032670.072690.003620.47 454.818.40.180.67 9.2 4.094.08 454.8 47.0452.34 454.8 457.00 21.2621.04 452.34 21.80 21.77480.79 125.39 120.66 452.34 21.80 21.77 206Pb/238U concordant scans 86 171 11AD2A 12212AZ1_14 165334.990.57424 0.03966 0.072840.00345 0.36 455.818.70.320.57 9.4 4.190.79 455.8 45.4 453.24 455.8 460.75 25.7425.42 453.24 20.76 20.72 499.20153.98 146.90 453.2420.76 20.72 206Pb/238U concordant scans 101 171 11AD2A 12212AZ1_59 480203 2.36 0.567310.02248 0.073330.00160 0.26 456.28.9 0.00 0.99 4.4 1.999.84 456.2 49.9 456.19 456.2 456.27 14.6214.51 456.19 9.59 9.59 456.93 90.12 87.66 456.199.599.59 206Pb/238U concordant scans 66 171 11AD2A12212AZ1_344485.55 0.591490.07438 0.074920.00423 0.21 466.724.10.060.80 12.0 5.292.30 466.7 46.2 465.72 466.7 471.8248.02 46.91465.72 25.39 25.34504.57 291.84267.41 465.7225.39 25.34 206Pb/238U concordant scans 57 171 11AD2A 12212AZ1_28 182513.570.59341 0.045380.07471 0.00450 0.42 468.223.50.320.57 11.8 5.090.11 468.2 45.1464.48 468.2 473.04 29.1228.71 464.48 27.03 26.97 515.49 169.08 160.57 464.48 27.03 26.97 206Pb/238U concordant scans 93 171 11AD2A 12212AZ1_35 76 15 5.17 0.589370.05802 0.075470.00468 0.32 469.525.50.010.94 12.7 5.497.90 469.5 48.9 469.05 469.5 470.4637.41 36.73 469.05 28.09 28.03 479.12 224.42 209.72 469.0528.09 28.03 206Pb/238U concordant scans 81 171 11AD2A 12212AZ1_69164 55 3.01 0.592870.03621 0.075990.00314 0.36 472.316.90.000.96 8.4 3.699.15 472.3 49.6 472.13 472.3 472.7023.21 22.95472.1318.81 18.79 476.19 136.07 130.52 472.13 18.81 18.79 206Pb/238U concordant scans 81 171 11AD2A 12212AZ1_33307 78 3.95 0.59664 0.035580.075710.003450.33 472.517.60.130.71 8.8 3.794.51 472.5 47.3 470.49 472.5 475.10 22.7522.50 470.49 20.67 20.64497.83 139.55 133.71 470.49 20.67 20.64 206Pb/238U concordant scans 84 171 11AD2A 12212AZ1_30 88 24 3.69 0.614900.05387 0.07727 0.004430.31 482.023.70.140.70 11.9 4.992.18 482.0 46.1 479.80 482.0 486.64 34.1633.59 479.80 26.52 26.47 520.51200.83 188.94 479.8026.52 26.47 206Pb/238U concordant scans 73 171 11AD2A 12212AZ1_43 299156 1.92 0.621250.03314 0.079150.00329 0.40 490.916.90.000.97 8.4 3.4100.42490.9 50.2 491.07 490.9 490.6320.87 20.65 491.0719.69 19.66 489.01 118.94 114.67491.0719.69 19.66 206Pb/238U concordant scans 86 171 11AD2A 12212AZ1_951553.22 0.696910.17489 0.081050.00716 0.15 505.741.40.410.52 20.7 8.272.49 505.7 36.2 502.38 505.7 536.94107.44 102.04 502.3842.79 42.65 693.02 591.75 498.25 502.38 42.79 42.65 206Pb/238U concordant scans 42 171 11AD2A12212AZ1_41274 1312.090.759490.03687 0.092980.00363 0.37 573.417.70.000.96 8.9 3.199.45 573.4 49.7 573.16 573.4 573.7121.39 21.17573.1621.42 21.39 576.36 109.70 106.04 573.16 21.42 21.39 206Pb/238U concordant scans 85 171 11AD2A 12212AZ1_84 451124 3.63 0.76186 0.039380.094060.004600.49 576.521.10.120.73 10.5 3.7103.89576.5 51.9 579.52 576.5 575.0822.82 22.57579.52 27.11 27.05557.84 112.81108.95 579.5227.11 27.05 206Pb/238U concordant scans 106 171 11AD2A 12212AZ1_39 415314 1.32 0.80484 0.032980.096670.003560.48 597.716.90.210.64 8.4 2.896.33 597.7 48.2 594.89 597.7 599.56 18.6418.47 594.8920.95 20.92 617.56 87.18 84.85 594.8920.95 20.92 206Pb/238U concordant scans 94 171 11AD2A12212AZ1_1559282.070.815120.08042 0.097950.00584 0.28 603.330.70.010.90 15.3 5.197.39 603.3 48.7 602.41 603.3 605.3245.49 44.50602.4134.32 34.23 618.53 223.32208.63 602.4134.32 34.23 206Pb/238U concordant scans 68 171 11AD2A 12212AZ1_27 65 1170.560.82581 0.073150.09736 0.00639 0.43 604.133.10.350.55 16.5 5.590.82 604.1 45.4598.91 604.1 611.29 41.0940.28 598.91 37.58 37.47 659.41 186.40 176.03 598.91 37.58 37.47 206Pb/238U concordant scans 81 171 11AD2A 12212AZ1_16 202395.120.816720.04635 0.098120.00477 0.48 605.023.10.040.84 11.5 3.897.73 605.0 48.9 603.40 605.0 606.22 26.07 25.74 603.40 28.02 27.95 617.43 119.54 115.20 603.4028.02 27.95 206Pb/238U concordant scans 102171 11AD2A 12212AZ1_17 215356.070.827940.05016 0.098910.004790.38 610.323.20.080.78 11.6 3.896.58 610.3 48.3 608.03 610.3 612.4728.06 27.67608.03 28.13 28.07629.54 135.74130.17 608.0328.13 28.07 206Pb/238U concordant scans 100 171 11AD2A 12212AZ1_86 143102 1.41 0.84237 0.053950.099310.004900.33 615.123.80.350.55 11.9 3.992.72 615.1 46.4 610.34 615.1 620.4529.95 29.52610.34 28.75 28.68658.24 146.61140.12 610.3428.75 28.68 206Pb/238U concordant scans 105 171 11AD2A 12212AZ1_13 276803.460.84086 0.043140.099850.004730.36 617.321.00.170.68 10.5 3.495.50 617.3 47.7 613.52 617.3 619.62 23.9423.66 613.52 27.77 27.71642.44 123.00 118.41 613.52 27.77 27.71 206Pb/238U concordant scans 101 171 11AD2A 12212AZ1_61 252127 1.98 0.83717 0.031910.100790.002420.27 618.512.40.020.88 6.2 2.0101.04618.5 50.5 619.05 618.5 617.58 17.7117.56 619.05 14.19 14.18612.67 85.66 83.41 619.0514.19 14.18 206Pb/238U concordant scans 92 171 11AD2A 12212AZ1_52199 1131.770.83863 0.038600.10132 0.002740.28 621.014.40.110.74 7.2 2.3102.78621.0 51.4 622.14 621.0 618.39 21.4321.21 622.1416.03 16.01 605.30 101.8098.64 622.14 16.03 16.01 206Pb/238U concordant scans 79 171 11AD2A12212AZ1_100252 1152.190.854910.05288 0.099670.00582 0.43 621.926.30.770.38 13.2 4.289.84 621.9 44.9 612.46 621.9 627.3429.15 28.74612.4634.15 34.06 681.74 140.33 134.36 612.46 34.15 34.06 206Pb/238U concordant scans 108 171 11AD2A12212AZ1_37481 1603.000.892120.03977 0.105030.00428 0.48 646.219.70.100.76 9.8 3.097.46 646.2 48.7 643.83 646.2 647.5121.45 21.23643.8325.02 24.97 660.60 94.83 92.07 643.83 25.02 24.97 206Pb/238U concordant scans 98 171 11AD2A12212AZ1_72127 277.79 0.930330.05734 0.106030.00507 0.40 658.325.01.210.27 12.5 3.888.95 658.3 44.5 649.67 658.3 667.81 30.3929.94 649.67 29.5929.52 730.36 132.53 127.18 649.67 29.59 29.52 206Pb/238U concordant scans 94 171 11AD2A 12212AZ1_29398 2191.810.946690.04811 0.108710.00495 0.44 672.122.60.590.44 11.3 3.493.20 672.1 46.6 665.27 672.1 676.3825.25 24.94665.27 28.82 28.75713.84 111.09107.32 665.2728.82 28.75 206Pb/238U concordant scans 118 171 11AD2A 12212AZ1_23151 57 2.63 0.98916 0.069360.112910.007000.47 695.032.30.200.66 16.1 4.694.83 695.0 47.4 689.61 695.0 698.29 35.7235.10 689.61 40.60 40.47727.21 148.10141.45 689.6140.60 40.47 206Pb/238U concordant scans 99 171 11AD2A 12212AZ1_57 96 73 1.31 1.278920.06769 0.13842 0.00411 0.22 835.920.30.000.97 10.2 2.499.37 835.9 49.7835.69 835.9 836.37 30.3929.94 835.69 23.31 23.27 840.95115.80 111.67 835.6923.31 23.27 206Pb/238U concordant scans 76 171 11AD2A 12212AZ1_20 139224 0.62 1.443730.08343 0.148630.00751 0.42 902.531.80.450.50 15.9 3.594.79 902.5 47.4 893.28 902.5 907.2734.96 34.37893.28 42.19 42.05942.39 122.35117.72 893.2842.19 42.05 206Pb/238U concordant scans 95 171 11AD2A 12212AZ1_2 208593.551.47844 0.089720.15210 0.00870 0.50 919.535.30.160.69 17.7 3.896.73 919.5 48.4912.70 919.5 921.59 37.0936.43 912.70 48.77 48.59 943.54123.52 118.80 912.70 48.77 48.59 206Pb/238U concordant scans 111 171 11AD2A 12212AZ1_8 3653311.03 1.482030.071290.15153 0.00692 0.57 920.428.50.690.41 14.3 3.195.14 920.4 47.6909.51 920.4 923.06 29.3828.96 909.51 38.78 38.67 955.93 90.33 87.78 909.51 38.78 38.67 206Pb/238U concordant scans 110 171 11AD2A 12212AZ1_19 2081711.98 1.48733 0.081890.152360.006960.41 921.030.00.310.58 15.0 3.396.00 921.0 48.0 914.17 921.0 925.23 33.7133.16 914.17 38.98 38.86952.29 115.55 111.41 914.17 38.98 38.86 206Pb/238U concordant scans 119 171 11AD2A12212AZ1_92107 33 3.25 1.52335 0.092900.155460.007350.37 936.332.40.140.71 16.2 3.597.01 936.3 48.5 931.52 936.3 939.8337.73 37.04931.52 41.04 40.91960.23 128.45123.35 931.5241.04 40.91 206Pb/238U concordant scans 97 171 11AD2A 12212AZ1_67 242524.671.54080 0.066510.15616 0.00552 0.41 942.523.90.530.47 12.0 2.596.05 942.5 48.0935.41 942.5 946.82 26.7626.41 935.41 30.81 30.74 973.89 88.90 86.43 935.41 30.81 30.74 206Pb/238U concordant scans 113 171 11AD2A 12212AZ1_22 143393.651.56153 0.097480.15751 0.00876 0.32 951.034.70.220.64 17.4 3.795.82 951.0 47.9942.91 951.0 955.08 39.0138.28 942.91 48.89 48.70 984.09143.49 137.15 942.91 48.89 48.70 206Pb/238U concordant scans 111 171 11AD2A 12212AZ1_82 422279 1.51 1.683020.084310.16557 0.00821 0.50 999.431.10.510.47 15.6 3.195.50 999.4 47.8987.65 999.4 1002.1332.16 31.66 987.6545.49 45.33 1034.17 102.7699.46 987.65 45.49 45.33 206Pb/238U concordant scans 120 171 11AD2A12212AZ1_44102 25 4.04 1.687020.08358 0.168250.00639 0.41 1003.1 27.9 0.00 0.95 14.0 2.899.51 1003.1 49.81002.44 1003.1 1003.64 31.83 31.341002.44 35.3235.22 1007.40 99.76 96.65 1002.4435.32 35.22 206Pb/238U concordant scans 93 171 11AD2A 12212AZ1_60 100244.231.74445 0.069940.17136 0.00350 0.21 1021.4 17.0 0.14 0.70 8.5 1.798.23 1021.4 49.1 1019.62 1021.4 1025.11 26.04 25.71 1019.62 19.30 19.27 1037.9583.95 81.73 1019.6219.30 19.27 206Pb/238U concordant scans 74 171 11AD2A 12212AZ1_11 4253910.91 1.806860.08536 0.175160.00754 0.45 1046.1 29.4 0.15 0.70 14.7 2.897.81 1046.1 48.9 1040.49 1046.1 1047.94 31.12 30.65 1040.49 41.41 41.281063.80 96.9794.02 1040.49 41.41 41.28 206Pb/238U concordant scans 116171 11AD2A 12212AZ1_71 258 70 3.70 1.881650.088680.178490.007670.42 1070.4 29.5 0.62 0.43 14.7 2.895.60 1070.4 47.8 1058.72 1070.4 1074.6431.49 31.01 1058.7242.00 41.86 1107.49 98.95 95.871058.72 42.0041.86 206Pb/238U concordant scans 103 171 11AD2A 12212AZ1_7480451.771.89885 0.110080.18149 0.00866 0.44 1078.9 35.6 0.06 0.81 17.8 3.398.33 1078.9 49.2 1075.08 1078.9 1080.69 38.93 38.201075.08 47.32 47.15 1093.29 115.12110.97 1075.0847.32 47.15 206Pb/238U concordant scans 112171 11AD2A 12212AZ1_56 14 13 1.10 1.908920.17786 0.182020.005940.12 1079.1 30.1 0.03 0.85 15.0 2.897.60 1079.1 48.8 1077.98 1079.1 1084.21 63.05 61.151077.98 32.43 32.351104.43 195.99 184.271077.98 32.43 32.35 206Pb/238U concordant scans 64 171 11AD2A 12212AZ1_76264 47 5.63 1.903120.08895 0.18079 0.008360.53 1080.6 30.7 0.30 0.58 15.3 2.896.99 1080.6 48.5 1071.31 1080.6 1082.18 31.35 30.87 1071.3145.74 45.58 1104.51 91.77 89.12 1071.31 45.74 45.58 206Pb/238U concordant scans 113171 11AD2A12212AZ1_4849212.291.90270 0.095970.183640.005170.20 1085.0 23.6 0.06 0.81 11.8 2.2101.131085.0 50.6 1086.85 1085.0 1082.0333.85 33.291086.85 28.1828.12 1074.71 107.33 103.721086.85 28.1828.12 206Pb/238U concordant scans 84 171 11AD2A12212AZ1_78299 29 10.271.957900.08573 0.185210.00774 0.49 1100.1 28.7 0.09 0.76 14.3 2.698.42 1100.1 49.2 1095.38 1100.1 1101.16 29.64 29.221095.38 42.19 42.05 1112.9487.64 85.21 1095.3842.19 42.05 206Pb/238U concordant scans 123171 11AD2A 12212AZ1_79 180593.042.13471 0.107720.194780.008630.48 1157.0 33.5 0.37 0.54 16.7 2.996.82 1157.0 48.4 1147.20 1157.0 1160.11 35.20 34.601147.20 46.63 46.461184.86 97.2894.29 1147.20 46.63 46.46 206Pb/238U concordant scans 116171 11AD2A 12212AZ1_6 97 21 4.65 2.162470.12060 0.19703 0.009810.46 1166.8 37.0 0.15 0.69 18.5 3.297.56 1166.8 48.81159.36 1166.8 1169.07 39.09 38.36 1159.3652.97 52.75 1188.37 111.21 107.32 1159.36 52.97 52.75 206Pb/238U concordant scans 98 171 11AD2A 12212AZ1_40254 86 2.93 2.20281 0.087080.200450.006710.41 1180.7 25.8 0.06 0.81 12.9 2.298.96 1180.7 49.5 1177.71 1180.7 1181.9427.79 27.42 1177.7136.10 36.00 1190.13 79.97 77.941177.71 36.1036.00 206Pb/238U concordant scans 105 171 11AD2A 12212AZ1_73 238317.732.26391 0.115600.19660 0.00874 0.46 1188.9 34.3 3.97 0.05 17.1 2.990.27 1188.9 45.1 1157.01 1188.9 1201.12 36.28 35.65 1157.01 47.15 46.98 1281.7799.07 95.95 1157.0147.15 46.98 206Pb/238U concordant scans 83 171 11AD2A 12212AZ1_87 4881338.02 2.301870.09748 0.203890.00908 0.51 1211.4 29.8 0.63 0.43 14.9 2.596.24 1211.4 48.1 1196.17 1211.4 1212.86 30.20 29.761196.17 48.72 48.531242.89 85.2682.95 1196.17 48.72 48.53 206Pb/238U concordant scans 101171 11AD2A 12212AZ1_24 104 54 1.93 2.298500.127840.20651 0.010020.51 1211.5 38.1 0.00 0.95 19.0 3.199.53 1211.5 49.8 1210.20 1211.5 1211.8339.74 38.98 1210.2053.65 53.43 1215.89 104.07 100.651210.20 53.6553.43 206Pb/238U concordant scans 99 171 11AD2A 12212AZ1_31317 90 3.52 2.365880.11943 0.206570.01011 0.53 1229.6 35.7 0.89 0.35 17.8 2.995.23 1229.6 47.6 1210.52 1229.6 1232.36 36.35 35.711210.52 54.14 53.91 1271.13 95.60 92.70 1210.5254.14 53.91 206Pb/238U concordant scans 110 171 11AD2A 12212AZ1_53 299953.142.50737 0.067670.217140.004630.42 1271.8 18.1 0.37 0.54 9.1 1.498.42 1271.8 49.2 1266.74 1271.8 1274.17 19.69 19.501266.74 24.56 24.51 1287.0852.05 51.171266.74 24.56 24.51 206Pb/238U concordant scans 74 171 11AD2A 12212AZ1_81248 72 3.46 2.510190.12554 0.217440.01007 0.55 1274.1 35.9 0.09 0.77 18.0 2.898.58 1274.1 49.3 1268.35 1274.1 1274.99 36.64 35.99 1268.3553.41 53.19 1286.57 90.60 87.99 1268.35 53.41 53.19 206Pb/238U concordant scans 114171 11AD2A 12212AZ1_10464262.482.59245 0.135480.220980.008920.35 1294.5 34.4 0.22 0.64 17.2 2.797.59 1294.5 48.8 1287.04 1294.5 1298.5138.66 37.931287.04 47.2047.03 1318.83 106.25 102.671287.04 47.20 47.03 206Pb/238U concordant scans 99 171 11AD2A12212AZ1_25450 6120.742.626250.14409 0.218600.01134 0.48 1302.4 39.6 1.55 0.21 19.8 3.093.46 1302.4 46.7 1274.49 1302.4 1308.02 40.75 39.951274.49 60.12 59.85 1363.68106.80 103.18 1274.4960.12 59.85 206Pb/238U concordant scans 101 171 11AD2A 12212AZ1_64 181563.252.78179 0.094050.233720.006270.37 1351.7 23.2 0.04 0.84 11.6 1.7100.591351.7 50.3 1353.95 1351.7 1350.66 25.41 25.10 1353.95 32.78 32.70 1346.0267.56 66.091353.95 32.78 32.70 206Pb/238U concordant scans 99 171 11AD2A 12212AZ1_54 215693.112.794200.08082 0.233500.00545 0.50 1353.7 20.8 0.01 0.93 10.4 1.599.74 1353.7 49.9 1352.80 1353.7 1353.99 21.74 21.511352.80 28.54 28.481356.35 51.9251.05 1352.80 28.54 28.48 206Pb/238U concordant scans 92 171 11AD2A 12212AZ1_109139 49 2.85 2.871870.13302 0.23341 0.01024 0.53 1372.1 34.6 0.94 0.33 17.3 2.595.93 1372.1 48.0 1352.37 1372.1 1374.5635.19 34.591352.37 53.6453.42 1409.80 84.72 82.42 1352.37 53.64 53.42 206Pb/238U concordant scans 100 171 11AD2A 12212AZ1_90373 93 4.01 2.925480.12970 0.236780.01055 0.53 1387.2 33.5 0.63 0.43 16.7 2.496.65 1387.2 48.3 1369.96 1387.2 1388.52 33.83 33.271369.96 55.12 54.88 1417.41 83.61 81.37 1369.9655.12 54.88 206Pb/238U concordant scans 100 171 11AD2A 12212AZ1_3 165692.392.95650 0.169540.237140.013050.45 1392.8 42.7 0.63 0.43 21.3 3.195.59 1392.8 47.8 1371.82 1392.8 1396.52 43.98 43.05 1371.82 68.18 67.82 1435.17 114.94 110.741371.82 68.18 67.82 206Pb/238U concordant scans 110171 11AD2A 12212AZ1_58 232115 2.02 2.95294 0.070470.241120.004180.44 1394.5 16.6 0.08 0.77 8.3 1.299.41 1394.5 49.7 1392.54 1394.5 1395.6018.18 18.021392.54 21.7421.70 1400.74 43.39 42.77 1392.54 21.74 21.70 206Pb/238U concordant scans 73 171

1Supplemental Materials. Description of detrital zircon U-Pb analytical methods (text document). Table S1: Complete detrital zircon U-Pb data and plots. Table S2: Detrital zircon age summary of samples from the Mystic subterrane of the Fare- well terrane, the Livengood terrane, and the White Mountains terrane. Table S3: Statistical compari- sons of all detrital zircon data. Table S4: Geochemi- cal data for phosphatic concretions. Table S5: Geo- chemical and isotopic data for mafic igneous rocks. Detrital zircon U-Pb age determinations were done by Apatite to Zircon, Inc. ington State University (GeoAnalytical Lab, Pullman, Washington, USA). The Please visit https://doi.org/10.1130/GES01588.S1 1 or the full-text article on www.gsapubs.org to view (now GeoSep Services; Moscow, Idaho, USA), using laser ablation–induc- Supplemental Materials contain a detailed description of analytical methods, the Supplemental Materials. tively coupled plasma–mass spectrometry (LA-ICP-MS) techniques at Wash- complete data tables including U-Pb concordia diagrams for all samples (Table

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TABLE 2. LOCATIONS AND DESCRIPTIONS OF DETRITAL ZIRCON SAMPLES ANALYZED FROM THE FAREWELL, LIVENGOOD, AND WHITE MOUNTAINS TERRANES, ALASKA

Quadrangle (locality [loc.] Latitude Longitude Description Sample Unit no.) (°N) (°W) (relevant photographs) Comments Farewell terrane 07ADw711ASheep Creek Fm.McGrath A2 62.0126153.7116 Medium sandstone, chert, quartz, plag, carb, Lv Strata contain possible plant fossils 09PH160A Sheep Creek Fm.McGrath B2 62.4794 153.8853 Chert clast conglomerate (Fig. 6F)DZ data first presented by Malkowski (2010) Strata interbedded with lithologies like those of 11AD2A Sheep Creek Fm. Lime Hills D4 61.7595 154.3250 Medium sandstone, quartz, chert, carb, plag sample 11AD3A Lime Hills D4 Bed contains brachiopods of prob Penn–Perm 11AD3A Sheep Creek Fm. 61.7605 154.3174 Bioclastic siltstone, carb > quartz (loc. 5) age (Gilbert et al., 1990) 11AD4A* Sheep Creek Fm. Lime Hills D4 61.8639 154.4222Very fine sandstone, quartz, plag, carb, chert 11AD6B Sheep Creek Fm.McGrath B2 62.4046 153.9333 Graded very coarse to medium sandstone, chert, carb, quartz, plag McGrath B2 Bed contains Late Penn (or Perm) fusulinids 11AD7B Sheep Creek Fm. 62. 2677 153.9566 Bioclastic very fine to fine sandstone, carb, quartz, chert (Figs. 6A–6D) (loc. 4) (Bundtzen et al., 1997) 12AD320G Sheep Creek Fm. Lime Hills D3 61.9657 153.7864Fine sandstone, quartz, chert, carb 12AJJ16A Sheep Creek Fm. Lime Hills D3 61.8281 152.9000Pebble conglomerate, carb, quartz, Ls (sandstone) (Fig. 6E) 12SB120B Sheep Creek Fm. Lime Hills D3 61.7874154.0769 Medium sandstone, quartz, plag, carb, Lv, Lm Talkeetna B6 76AR16C* Sheep Creek Fm.(?) 62.4792 152.8205Fine sandstone, >80% quartz, chert, plag, carb (loc. 6) Lower Mystic Talkeetna C6 11AD202C 62.5710152.7575 Medium to pebbly sandstone, chert, Ls, Lv, quartz (Figs. 6H–6K) assemblage (loc. 10) Lower Mystic Talkeetna C5 Medium to coarse metasandstone, altered lithic clasts include Lv, Lm, 03ADw407D* 62.7139 152.3931 DZ data presented by Bradley et al. (2007) assemblage (loc. 8) minor quartz, plag Lower Mystic Talkeetna C6 03ADw415C 62.6186 152.7807 Granule conglomerate, Lv, Ls, chertDZ data presented by Bradley et al. (2007) assemblage (loc. 9) 00ADw100B, 00ADw100E, 00ADw100AA: pebble conglomerate; DZ sample is composite of 00ADw100B, Mount Dall Talkeetna C5 00ADw100 62.5944 152.1681 00ADw100BB: medium sandstone; for all, chert > carb and/or Ls, rare 00ADw100E, 00ADw100AA, and conglomerate (loc. 11) Lv, quartz (Figs. 9A–9E) 00ADw100BB Medfra C3 97ADw122A: quartz siltstone; 97ADw122B-97ADw122F, silty to pebbly DZ sample is composite of 97ADw122A- 97ADw122 Permian strata 63.6145 154.1877 (loc. 1, Fig. 2) bioclastic limestone, 5%–30% quartz (Figs. 9H–9J) 97ADw122F DZ sample is composite of 97ADw119B, Medfra C3 97ADw119B, 97ADw119C, and 97ADw119E: carbonate pebble 97ADw119 Permian strata(?) 63.6595 154.1870 97ADw119C, and 97ADw119E; strata mapped (loc. 2, Fig. 2) conglomerate (Figs. 9K–9L) as unit Ksu by Patton et al. (1980) McGrath B1 11ADw119ATriassic strata 62.3915153.0828Very fine to fine sandstone, chert , quartz, carb, wm (Figs. 10D–10F) (loc. 13) McGrath A2 Strata mapped by Bundtzen et al. (1997) as 12AJJ20ATriassic strata 62.0207 153.6909Carb pebble conglomerate, quartz, plag, kspar (Figs. 10A–10C) (loc. 12) Sheep Creek Formation McGrath A2 Strata mapped by Bundtzen et al. (1997) as 12AJJ20BTriassic strata 62.0226 153.6915Carb pebble conglomerate, quartz, plag, Lp (Figs. 10A–10C) (loc. 12) Sheep Creek Formation Talkeetna C6 Pebbly volcaniclastic sandstone, andesitic clasts, altered glass shards 11AD203C Tr iassic–Jurassic strata 62.5722 152.8295 (loc. 16) (Fig. 10K) McGrath B1 Very fine sandstone, 80% quartz, carb, Ls, plag, chert, chl, wm (Figs. 13A, 11SB112AJurassic strata 62.3765 153.1224 (loc. 19) 13B) McGrath B1 12SB107C Jurassic strata 62.3333 153.2960Very fine sandstone, quartz, carb, plag, wm (Fig. 10L) (loc. 15) Lime Hills D3 Very fine to fine quartz-carb sandstone with coarse bivalve fragments 12AD320H Jurassic strata 61.9691 153.7843 (loc. 21) (Fig. 13D) Lime Hills D3 13AD409D Jurassic strata 61.8044 154.0484Very fine to fine sandstone, quartz, chert, phosphate (Figs. 13E, 13F) (loc. 17) McGrath B1 13SB28FJurassic strata 62.3818153.1349 Very fine to fine sandstone, carb > quartz, wm, chl (Fig. 13C) (loc. 20) 98ADw212A: fine sandstone, chert > quartz, Ls, Lm, plag, wm; DZ sample is composite of 98ADw212A, Medfra B3 98ADw212 Cretaceous strata 63.4517154.2200 98ADw212C: pebble to granule conglomerate, chert > Ls > Qp 98ADw212C; strata mapped as unit Ksu by (loc. 3, Fig. 2) (Fig. 13J) Patton et al. (1980) (continued)

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TABLE 2. LOCATIONS AND DESCRIPTIONS OF DETRITAL ZIRCON SAMPLES ANALYZED FROM THE FAREWELL, LIVENGOOD, AND WHITE MOUNTAINS TERRANES, ALASKA (continued)

Quadrangle (locality [loc.] Latitude Longitude Description Sample Unit no.) (°N) (°W) (relevant photographs) Comments Farewell terrane (continued) Talkeetna C6 Very fine to medium sandstone, quartz, plag, kspar, Ls, Lm, Lv, Lp, wm, 11AD203D Cretaceous strata 62.5722 152.8295 (loc. 16) biotite, chl (Fig. 13K) Livengood terrane Livengood B3 07ADw703A Cascaden Ridge unit 65.4895 148.4703 Fine to medium sandstone, carb, quartz, chert (CR, Fig. 1) White Mountains terrane Livengood B3 07ADw702A Globe unit 65.3016 148.2008 Fine sandstone, 80%–90% quartz, minor chert, Ls, tourmaline (G, Fig. 1) Note: Localities are shown on Figure 4 except where noted. Lithic grains: Lm—metamorphic; Lp—plutonic; Ls—sedimentary; Lv—volcanic. carb—carbonate; chl—chlorite; DZ—detrital zircon; kspar—potassium feldspar; Penn—Pennsylvanian; Perm—Permian; plag—plagioclase feldspar; prob—probably; Qp—polycrystalline quartz; wm—white mica. *Latitude and longitude were determined using station location on a field sheet.

S1), and a summary of calculated age populations for each sample (Table S2). contributing to the population. The youngest age population is also labeled Raw, uninterpreted U-Pb data were also published as a U.S. Geological Sur- in each of the KDE plots for our individual samples. Other notable age popu- vey (USGS) Data Release (Dumoulin et al., 2018a). We calculated a concordia lations determined using the AgePick macro are also labeled in the KDE plots age (including decay constant error) for each analysis and used this value as where applicable and discussed in the text below. the preferred age of the associated detrital zircon grain instead of using either After screening all of the data, we used the DZstats tool (version 2.2) of the 206Pb/238U or 207Pb/206Pb age (Ludwig, 1998; Nemchin and Cawood, 2005). Saylor and Sundell (2016) to plot the cumulative distribution function for dif- The concordia age makes optimum use of both decay schemes and obviates ferent sample sets and to calculate a variety of comparative metrics including the need to choose an arbitrary age threshold for selecting the 206Pb/238U or Kolmogorov-Smirnoff (K-S) and Kuiper tests and cross-correlation, likeness, 207Pb/206Pb age as the “preferred age” for an individual grain (Ludwig, 1998). and similarity coefficients of probability density plots (PDPs) for all samples. Additionally, the concordia age calculation gives probability of concordance The results of the statistical comparisons for all samples are shown in the Sup- (POC) for each analysis, which provides a useful means of assessing concor- plemental Materials (Table S3 [footnote 1]), and select results are discussed in dance for all grains regardless of age. After calculating the concordia age and the text below. We also applied multi-dimensional scaling (MDS) using the R associated statistics for each analysis, we screened the data for uncertainty code of Vermeesch et al. (2016) as another means of assessing the similarity and probability of concordance. Analyses with >10% age uncertainty (at 1σ) between our samples and other published data. The MDS plots of the U-Pb were excluded or “filtered” from plots and statistical treatments. Grains with data sets use the K-S effect size as a dissimilarity measure. MDS is a statisti- a POC <0.1 were also excluded unless the grain was older than 1000 Ma and cal technique that uses pairwise calculated dissimilarities between samples had a calculated concordance (comparison of 206Pb/238U or 207Pb/206Pb ages) be- to produce a map of points on which similar samples cluster more closely tween 80% and 105%. Data that were excluded are reported in Table S1 (foot- together and dissimilar samples plot farther apart (Vermeesch, 2013). note 1) but are crossed out to indicate that they were not considered further. The Supplemental Materials (footnote 1) also contain geochemical data for Age probability diagrams were generated using the kernel density estimation two phosphatic concretions described below (Table S4) as well as geochemical (KDE) method of Vermeesch (2012), and all KDE diagrams were generated us- and isotopic data for mafic igneous rocks (Table S5) that are discussed and ing adaptive KDE wherein the bandwidth varies depending on data density summarized in plots below. (Vermeesch, 2012). Histogram bins, where shown, generally represent ~25 m.y. Age populations were identified by using the AgePick macro for Micro- soft Excel (Gehrels, 2009), and results for all samples are shown in Table S2 MIDDLE–UPPER DEVONIAN STRATA (footnote 1). The maximum depositional age for each sample was determined using the youngest age population made up of three or more grains with ages Deep-water Middle and Upper Devonian rocks occur at or near the base of that overlap within 2σ uncertainty and define a distinct population with a mean the Mystic subterrane in areas E and F (Fig. 3). These strata make up map units square of weighted deviates (MSWD) of 2 or less. The maximum depositional Ds and Dcs in the northern Lime Hills quadrangle (Gilbert et al., 1990; Bundtzen age as determined from our detrital zircon data for each sample is listed in and Gilbert, 1991), part of the lower Sheep Creek Formation in the McGrath Table S2 (footnote 1) together with 2σ uncertainty and the number of grains quadrangle (Bundtzen et al., 1997), and an interval in the lower part of map unit

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TABLE 3. UPPER PALEOZOIC CLASTIC UNITS OF THE FAREWELL TERRANE, ALASKA

Age Detrital zircon data (Ma) Unit Location constraint Youngest Major peaks Composition Comments Upper Sheep Creek Area E (locs. Penn–Perm 435 ± 10 to 459–405 Heterolithic sl, ss, cgl; subordinate chert- Sheep Creek(?) strata at locality 6 have Formation (B) 4, 5, 6?) fossils 368 ± 7 clast cgl and calcareous sandstone to >80% quartz; youngest DZs 368 ± 7 Ma silty lms Lower Mystic Area F (locs. Miss–Penn 316 ± 5 to 340 445–424, Lv-rich ss, sl, cgl DZ data set includes two samples from assemblage (M) 7–10) fossils ± 5 347–335 Malkowski and Hampton (2014) Upper Mystic Areas E?, F Middle Perm 267 ± 6 ca. 425, ca. 298 Lv-rich ss, sl, cgl Data from Malkowski and Hampton assemblage (M) DZs (2014); probable outlier of this unit in area E has youngest DZs 282 ± 5 Ma Mount Dall Area E (loc. 11) Early Perm 304 ± 6 ca. 1840, 349 Chert- and/or carbonate-clast cgl, ss, sl conglomerate (R) fossils Permian clastic Area A (loc. 1, Middle Perm 256 ± 4 256 Quartz-rich to calcareous ss, sl strata (P) Fig. 2) fossils Permian(?) Area A (loc. 2, Late Dev DZs 369 ± 5 369 Carbonate-clast cgl Strata mapped as unit Ksu by Patton conglomerate (P) Fig. 2) et al. (1980) but considered Perm by others Note: Units defined by: B—Bundtzen et al. (1997); M—Malkowski and Hampton (2014); P—Patton et al. (1980); R—Reed and Nelson (1980). Areas are as in Figure 2; localities (locs.) are as in Figure 4 except where noted. “Youngest” is youngest detrital zircon age population as defined in text, with 2σ uncertainty. cgl—conglomerate; Dev—Devonian; DZs—detrital zircons; lms—limestone; Lv—lithic volcanic clast; Miss—Mississippian; Penn—Pennsylvanian; Perm—Permian; sl—siltstone; ss—sandstone.

Pzus in the Talkeetna quadrangle (Reed and Nelson, 1980). Lithologies include laminated calcareous radiolarite (Fig. 5G; Table 1, sample 12AD319M). Other dark gray to black shale, siltstone, and varicolored chert. concretions from this interval yielded the late Middle Devonian coral Dendro­ Black shale in unit Ds (locality [loc.] 1, Fig. 4) includes an interval of bed- strella sp. and Frasnian conodonts (Bundtzen et al., 1997). Thin-section textural ded barite ~50 m thick (Gagaryah deposit; Bundtzen and Gilbert, 1991). Barite analysis of this unit indicates that corals and other shallow-water biota were textures range from massive to laminated to nodular (Figs. 5A–5D). Frasnian redeposited into a deeper-water, off-shelf setting. (early Late Devonian) brachiopods have been identified in silty sandstone Reed and Nelson (1980) described an interval of unknown thickness in 50–60 m stratigraphically above the deposit (Gilbert et al., 1990; Bundtzen and their unit Pzus (loc. 3, Fig. 4) made up of black shale and phosphatic chert Gilbert, 1991). bearing distinctive fluorapatite concretions (”blackballs”); they presented no New isotopic and geochemical data were reported for the origin of the petrographic or geochemical documentation of these strata. The concretions, Gagaryah barite by Johnson et al. (2016). Total organic carbon in the barite 3–4 cm in diameter (Fig. 5H), contain a well-preserved Famennian radiolarian layers has δ13C values that are consistent with a marine origin for the organic fauna (Reed and Nelson, 1980). Our thin-section studies found abundant ra- matter. The δ34S values for both laminated and nodular barite are notably diolarians in a matrix of dark brown phosphate intergrown with pale quartz, higher than the 23‰ value that has been inferred for Middle–Late Devonian calcite, and minor barite (Figs. 5I, 5J). Geochemical analysis (inductively cou- marine sulfate from time-averaged data for evaporites and carbonate-asso- pled plasma–mass spectrometry) of two concretions (combined) found 14.4% 34 ciated sulfate (Kampschulte and Strauss, 2004). The high δ S values could P (32.6% P2O5; Table S4 [footnote 1]). reflect local effects such as restriction of the depositional basin, methane Bedded barite, black shale, calcareous radiolarite, and phosphorite typi- involvement in sulfur redox cycling, or remobilization of 34S-rich sulfur from cally form in environments characterized by high productivity, such as coastal underlying strata (Johnson et al., 2016). Alternatively, the high values could areas affected by upwelling currents (e.g., Dumoulin et al., 2004). Implications reflect formation of the deposits at a time when the global ocean experienced of these Mystic lithofacies are discussed further below. a brief enrichment in 34S. Independent evidence for such enrichment in lower Frasnian and Frasnian-Famennian boundary strata was reported by Holser (1977) and Chen et al. (2013). DEVONIAN–PERMIAN UPPER SHEEP CREEK FORMATION In the southeastern McGrath quadrangle (loc. 2, Fig. 4), black shale in the lower part of the Sheep Creek Formation (Bundtzen et al., 1997) contains nu- Lithologies and Fossil Data merous limy concretions up to 12 cm in diameter (Figs. 5E, 5F). The concre- tions consist of lime mudstone with locally abundant calcitized radiolarians The Sheep Creek Formation (Devonian–Permian) consists chiefly of fine- (Fig. 5G). One concretion contained the coral Cystiphylloides sp. of probable to coarse-grained siliciclastic strata exposed in the central part of the Mystic Middle Devonian age (C. Stevens, 2014, personal commun.) in a matrix of subterrane (areas D, E). The unit was proposed by Bundtzen et al. (1997) to

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encompass rocks in the eastern McGrath quadrangle, and extended (T. Bundt- 09PH160A, 11AD6B, 11AD7B) were collected from sections in the southeast zen, 1998, personal commun.) to include strata in the Lime Hills quadrangle McGrath quadrangle that were mapped as Sheep Creek (subunit PDs) by (e.g., map units PDs of Bundtzen et al. [1994] and uPzs of Gilbert et al. [1990]). Bundtzen et al. (1997); one of these (11AD7B; loc. 4, Fig. 4) is from a bioclas- As described by these authors, the uppermost subunit of the Sheep Creek is tic sandstone layer near the stratigraphic midpoint of the subunit that pro- mainly sandstone that is distinguished from sandstone in the underlying Dil- duced fusulinid foraminifers of Late Pennsylvanian to possibly Permian age linger subterrane by containing less matrix, little or no white mica, more chert (R.C. Douglas in Bundtzen et al., 1997). Three samples (11AD2A, 11AD3A, and clasts, and local plant fragments. Graded bedding, common rip-up clasts, and 11AD4A) are from the map unit uPzs in the Lime Hills D-4 1:63,360-scale quad- partial Bouma sequences indicate a turbidite origin for Sheep Creek sandstone, rangle (north-central part of the Lime Hills 1:250,000-scale quadrangle; Gilbert and rare spiriferid brachiopods and fusulinid foraminifers in this lithofacies are et al., 1990); one of these (11AD3A; loc. 5, Fig. 4) is from a calcareous siltstone of probable Pennsylvanian–Permian age (Gilbert et al., 1990; Bundtzen et al., bed containing spiriferid and rhynchonellid brachiopods of probable Pennsyl- 1997). The lower part of the Sheep Creek (Bundtzen et al., 1997) comprises vanian or Permian age according to these authors. Three samples (12AD320G, black shale with carbonate concretions bearing the Middle and Late Devonian 12AJJ16A, 12SB120B) come from the Lime Hills D-3 1:63,360-scale quadran- corals and conodonts discussed above, overlying “massive, Amphipora-bear- gle, have similarities in lithology and stratigraphic position to the upper Sheep ing algal limestone” (Bundtzen et al., 1997, p. 5) and dolostone equivalent in Creek Formation in the McGrath quadrangle, and have been included in the age and lithofacies to the upper part of the Nixon Fork subterrane. A thickness Sheep Creek during recent mapping (Box et al., 2015a). of ~535–725 m was estimated for the Sheep Creek Formation in the southeast- Our final sample is from the west-central Talkeetna quadrangle (76AR16C, ern McGrath quadrangle (Bundtzen et al., 1997). Table 2; loc. 6, Fig. 4), from vertically bedded, fine-grained sandstone that A distinctive carbonate conglomerate interval considered by Bundtzen et is unconformably overlain (B. Reed, 1976, personal commun.) by sandy al. (1997) to be part of the Sheep Creek Formation produced a Triassic detrital limestone containing Jurassic fossils (sample 76AR13, Table 1). The sample zircon population (samples 12AJJ20A, 12AJJ20B [Table 2]). These strata are consists of >80% angular to rounded monocrystalline quartz, with minor pla- herein excluded from the Sheep Creek and are discussed further below. gioclase feldspar, chert clasts, and carbonate. Petrographically, this sample Sheep Creek Formation sections that we studied (Figs. 4, 6A–6F; Table 2) is unlike any other upper Sheep Creek sample examined for this study, but consist of siltstone, fine- to medium-grained sandstone, and minor conglom- resembles instead Jurassic strata discussed below. Its stratigraphic position erate, and comprise three main lithofacies. Heterolithic siltstone to sandstone suggests inclusion in the upper Sheep Creek, however, and we provisionally predominates and is typically made up of 20%–30% monocrystalline quartz, consider it to be part of that unit, although a single young (Triassic) zircon 10%–40% chert clasts, and subordinate carbonate (as cement and/or clasts) obtained from this sample (and discussed below) could provide support for and plagioclase feldspar (Figs. 6B, 6E). Rare clasts of mafic volcanic rocks a younger age. and micaceous sandstone occur in a few samples, and one sample contains Detrital zircon spectra from our ten Sheep Creek samples—including a pseudopunctate brachiopod fragment. Metamorphic lithic clasts and mica the two from beds with late Paleozoic fossils—all have Devonian and older grains are generally very rare or absent. age populations (Fig. 7). Calculated ages of the youngest age populations, Two additional lithofacies occur as subordinate interbeds in some Sheep and hence maximum depositional ages, range from 435 ± 10 to 374 ± 9 Ma Creek sections (Table 2). The first is chert conglomerate (Fig. 6F), which forms (Silurian to early Late Devonian). One sample (11AD3A) contains a single grain layers ≤2 m thick at several localities. Clasts reach 8 cm in length but are of Permian age (ca. 258 Ma) and a grain of latest Pennsylvanian age (ca. 300 typically ≤1–3 cm. More than 80% of clasts are pale to dark gray chert (many Ma; Table S1 [footnote 1]). The calculated maximum depositional age of the with radiolarians, some with sponge spicules or quartz veins); other clast quartzose sandstone from the Talkeetna quadrangle (sample 76AR16C; loc. 6, types are limestone and micaceous sandstone. The second lithofacies—cal- Fig. 4) is slightly younger at 368 ± 7 Ma (late Late Devonian), and this sample careous fine-grained to pebbly sandstone grading to silty wackestone (Figs. also contains a single grain of Triassic age (ca. 232 Ma; Table S1). All eleven 6C, 6D)—occurs as thin beds at three localities (Table 2). Fossils are locally samples have dominant age probability peaks with maxima between ca. 460 abundant and include brachiopods, bryozoans, echinoderms, foraminifers, and 405 Ma and a wide array of older, mainly Proterozoic, grains. and ostracodes. Quantitative metrics show some variation in the similarity of the Sheep Creek samples, as PDP cross-correlation coefficients range from 0.43 to 0.93 for all inter-sample comparisons (Table S3 [footnote 1]; Saylor and Sundell, Detrital Zircon Data 2016). Sample 09PH160A produces the lowest values among all samples and also plots farthest from all other samples on the MDS diagram (Fig. 7C). More Detrital zircon U-Pb ages were determined for ten samples here considered than half of the inter-sample comparisons have PDP cross-correlation coef- to be from the upper Sheep Creek Formation, as well as an additional sample ficients >0.75 (Table S3). Similarity coefficients are >0.77 for all Sheep Creek that may belong to this unit (Table 2; Figs. 4, 7). Four samples (07ADw711A, comparisons, and likeness coefficients range from 0.52 to 0.81 (Table S3).

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Figure 7. Detrital zircon kernel density esti- mate (KDE) diagrams (A), cumulative distribu- tion function plot (B), and multi-dimensional scaling (MDS) plot (C) for samples from the Sheep Creek Formation; samples in A marked with * come from beds with late Paleozoic fossils. See Table 2 and Figure 4 for sample descriptions and locations. KDEs were gen- erated using adaptive kernel density esti- mation (Vermeesch, 2012); each histogram bin represents ~25 m.y. The vertical band in panel A approximately indicates the Silurian period (ca. 444–419 Ma). Solid lines between symbols in the MDS plot represent near- est neighbors, and dashed lines represent next-nearest neighbors. Short sample labels in parentheses in A are keyed to symbols in the MDS plot, and stress value is indicated by “S” (Vermeesch, 2013).

PALEOZOIC STRATA (MAP UNIT Pzus) ally complex” assemblage of diverse rock types, but “flyschoid sedimentary rocks” (graywacke, mudrock, grit, chert pebble conglomerate) and various Lithologies and Fossil Data types of volcanogenic rocks (including pillow basalt) predominate (Reed and Nelson, 1980, p. 7). Reed and Nelson (1980) recognized as part of unit Pzus a Rocks at least partly coeval with the Sheep Creek Formation make up map graywacke-dominated sequence that grades downward into sparse beds of unit Pzus (undivided sedimentary rocks) of Reed and Nelson (1980) in the Tal­ Upper Mississippian and Middle Pennsylvanian echinoderm-pellet limestone keetna quadrangle (area F, Figs. 2, 3). This unit is a “depositionally and structur- and upward into massive chert-limestone conglomerate that is at least in part

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terrestrial. The conglomerate in turn grades upward into the Permian Mount conglomerate at one end of the section contains conodonts of Silurian–Middle Dall conglomerate (Reed and Nelson, 1980; Sunderlin, 2008), suggesting a Devonian age (Table 1). Coarse grained, pebbly sandstone in contact with the Carboniferous–Permian age for the graywacke sequence. Older lithologies tuff consists chiefly of volcanic lithic clasts. Pebble elongation layering in this encompassed in unit Pzus include the Upper Devonian shale and phosphatic sandstone is at a high angle to the contact, implying a structural or uncon- chert discussed above as well as Middle and Upper Devonian redbeds and formable relation between the two lithologies. Granule conglomerate a few reefoid limestone (Reed and Nelson, 1980). tens of meters topographically above the tuff (sample 03ADw415C) has clasts New conodont (Table 1) and lithologic data from one of the limy layers in (to 4 mm) made up in subequal amounts of volcanic rocks, sedimentary lithic the graywacke sequence (loc. 7, Fig. 4; Reed and Nelson, 1980, their loc. 16) grains, and chert (some with radiolarians ± siliceous sponge spicules). support a late Paleozoic age for this layer and indicate that it formed as a size- We studied another unit Pzus section southwest of Mystic Pass (loc. 10; sorted lag deposit. The layer is crinoidal grainstone with foraminifers, bryo- Fig. 4). Rocks here are very thin- to medium-bedded argillite, limy siltstone, zoan and brachiopod fragments (some of which are bored), lime peloids, and sandstone, and granule conglomerate (Figs. 6H–6K). Beds are graded and con- ~10% non-carbonate clasts (mainly siliceous mudstone and radiolarian chert) tain locally abundant shale rip-up clasts. Sandstone and conglomerate consist up to 4 mm in diameter (Fig. 6G). The conodont assemblage contains elements mainly of sedimentary lithic clasts and chert grains (most radiolarian bear- no older than Pennsylvanian (possibly Permian?), as well as reworked Devo- ing) with 5%–15% mafic volcanic lithic clasts (Figs. 6J, 6K). Calcite cement is nian and Late Mississippian elements (A. Harris, 2004, personal commun.). common, and several limy layers contain abundant bioclasts, including echi- The most likely age of the conodont assemblage is consistent with the Middle noderm and bryozoan debris, ostracodes, and agglutinated and calcareous Pennsylvanian age based on foraminifers reported by A. Armstrong (in Reed foraminifers. and Nelson, 1980). The assemblage has been winnowed; all fine-grained ma- Thus, siliciclastic beds in unit Pzus examined for this study and described terial has been removed. Numerous small, pink to clear, subhedral to rounded by Malkowski and Hampton (2014) contain notably more volcanic lithic clasts zircons were found in the heavy mineral residue that remained after process- and less monocrystalline quartz than do those in the Sheep Creek Formation. ing for conodonts. Both units contain abundant chert grains and rare limy, fossiliferous beds. Reed and Nelson (1980) provided no petrographic details for the upper Pa- leozoic graywacke sequence in unit Pzus. Recent studies, and our new data, indicate that this sequence encompasses several compositional variants. Detrital Zircon Data Malkowski and Hampton (2014) described rocks of unit Pzus in the area of Mystic Pass (Fig. 4), the type locality of their “Mystic assemblage.” Strata in Our sample from locality 10 (11AD202C; Fig. 4; Table 2) yielded a detrital the Mystic Pass area are sandstone, siltstone, mudstone, and subordinate con- zircon age spectrum much like those of our Sheep Creek Formation samples, glomerate, interpreted as low- to high-density sediment gravity flow deposits but with a Mississippian (Visean) youngest age population of 340 ± 5 Ma that formed in a submarine fan environment. Sandstones are uniformly rich (Fig. 8A; Table S2 [footnote 1]) and a single grain of early Permian age (ca. 288 in mafic to intermediate volcanic lithic grains (average 66% of all grains and Ma; Table S1). Detrital zircon data from two localities in unit Pzus published by >80% of lithic grains) with subordinate chert and sedimentary clasts, and only Bradley et al. (2007) yielded age spectra that were broadly similar to that from a few percent each of monocrystalline quartz and feldspar. Conglomerate lay- locality 10 but include more abundant Mississippian age populations and have ers, 1–4.5 m thick, contain rounded clasts ≤10 cm in diameter that are mainly mid-Mississippian youngest age populations of ca. 347 and 335 Ma (samples volcanic rocks and chert. 03ADw415C and 03ADw407D; Table 2; Fig. 8A). The MDS plot (Fig. 8C) shows Bradley et al. (2007) briefly described strata at two localities within map that these three samples, herein called “lower Mystic assemblage” on the unit Pzus that are west and northeast of Mystic Pass (Fig. 4), for which we basis of lithologic and detrital zircon similarities with strata so designated by provide additional petrographic and fossil data. Deformed turbidites at sample Malkowski and Hampton (2014), are all generally similar but do show some site 03ADw407 (loc. 8, Fig. 4) consist chiefly of altered lithic clasts, some of separation in MDS space. We attribute the variation to differences in the pro- which are mafic volcanic grains with lathwork textures. Carbonate alteration portion of Devonian and Mississippian grains that otherwise define statistical and replacement are pervasive. Discrete grains of monocrystalline quartz and populations with similar ages. feldspar are rare. Strata at sample site 03ADw415 (loc. 9, Fig. 4) include slate, Quantitative metrics show some variation in the similarity of our three granule conglomerate, sandstone, rare micritic limestone, and a 1-m-thick ash- “lower Mystic assemblage” samples (Table S3 [footnote 1]; Saylor and fall tuff with a U-Pb zircon age (Bradley et al., 2007) of ca. 223 Ma. Bradley Sundell, 2016). PDP cross-correlation coefficients range from 0.46 to 0.80 et al. (2007) interpreted the tuff and associated sandstone and conglomerate and are lowest for sample 03ADw407D. This sample also plots farthest from section as Triassic, but additional data indicate a more complex picture, with the other two in the MDS plot (Fig. 8C). The maxima in the KDE diagram rocks of several ages present and stratigraphic relations between the litholo- for this sample is slightly younger than for the other two, and it does not gies uncertain. A fine crystalline dolomitic limestone layer interbedded with contain as many Silurian grains (Fig. 8A). Similarity coefficients are >0.79 for

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Figure 8. Detrital zircon kernel density estimate (KDE) diagrams (A), cumulative distribution function plot (B), and multi-dimensional scaling (MDS) plot (C) for samples from the Mystic assemblage, Mount Dall conglomerate, and unnamed Permian (and older?) strata in the Medfra quadrangle together with the composite age spectrum for the Sheep Creek Formation. See Table 2 and Figures 2 and 4 for sample descriptions and locations. KDEs were generated using adaptive kernel density estimation (Vermeesch, 2012); each histogram bin represents ~25 m.y. The purple vertical band in panel A approximately indicates the Silurian period (ca. 444-419 Ma) and the blue vertical band approximately indicates the Mississippian and Pennsylvanian periods (ca. 359–299 Ma). The inset for sample 97ADw122 shows the KDE for the youngest age population with 5 m.y. histogram bins; the single unshaded bin was excluded from the weighted average calculation (see text for details). Y-axis on inset figure is number of grains. Solid lines between symbols in the MDS plot represent nearest neighbors, and dashed lines represent next-nearest neighbors. Short sample labels in parentheses in A are keyed to symbols in the MDS plot, and stress value is indicated by “S” (Vermeesch, 2013).

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all three sample comparisons, and likeness coefficients range from 0.52 to 0.69 grains with a subordinate probability peak at ca. 1840 Ma (sample 00ADw100, (Table S3). Fig. 8A). The youngest age population is latest Pennsylvanian (304 ± 6 Ma; Table S2 [footnote 1]).

PERMIAN MOUNT DALL CONGLOMERATE PERMIAN (AND OLDER?) STRATA IN THE MEDFRA Lithologies and Fossil Data QUADRANGLE

The Mount Dall conglomerate (Reed and Nelson, 1980) is an interval of con- Lithologies and Fossil Data glomerate, sandstone, siltstone, and mudstone ~1500 m thick that is widely exposed in area F. A flora of ferns, cyclopteroids, and cordaitaleans and local Permian strata in area A (Medfra quadrangle; Figs. 2, 3, 9H–9J) consist rhynchonellid and strophomenid brachiopods indicate a probable early Perm- chiefly of yellowish orange–weathering sandstone, sandy limestone, siltstone, ian age (Mamay and Reed, 1984; Sunderlin 2008). The unit is characterized by and conglomerate that contain middle Permian (Guadalupian) brachiopods fining-upward sequences tens of meters thick and likely formed in a coastal (Patton et al., 1980, 1994). Other fossils include bryozoans and a new species braidplain setting (Sunderlin, 2008). Bradley et al. (2003) interpreted the Mount of trilobite (Hahn and Hahn, 1993). The unit (map unit Ps of Patton et al. [1980]) Dall as a foreland basin succession deposited during the early Permian Browns is 60–120 m thick and is bounded above and below by unconformities or dis- Fork orogeny. Clasts in the Mount Dall are mainly diverse carbonate rocks and conformities (Patton et al., 1977, 1980; Andrews and Rishel, 1982). New petro- chert, and carbonate clasts have yielded faunas of both middle and late Paleo- graphic, paleontologic, and detrital zircon data illuminate the depositional set- zoic age. Reed and Nelson (1980) reported Middle Devonian(?) megafossils, ting and provenance of this unit. and a large clast of fine-grained carbonate produced Silurian–Devonian cono- Sandstone (e.g., loc. 1, Fig. 2) is thin to medium bedded with local small- donts (Table 1). Three large clasts of skeletal packstone to grainstone yielded scale ripples and cross-laminae, millimeter-scale cylindrical burrows, larger Pennsylvanian conodonts (one fauna could be as young as earliest Permian; trace fossils such as Zoophycos, plant fragments, and woody debris. Samples Bradley et al., 2003). Foraminifers in one of these clasts and in an additional are fine to coarse grained and cemented by silica and/or calcite; grains are clast of similar lithology are of Late Mississippian(?) age and may have been angular to rounded. Composition ranges from relatively clean quartz arenite redeposited; the fauna consists of typical Northern Hemisphere taxa and to calcarenite to lithic arenite rich in mica and metamorphic rock fragments includes no Tethyan forms (P. Brenckle, 2016, personal commun.; Table 1). (Patton et al., 1980). Feldspar, tourmaline, phosphate, glauconite, and dolomite We examined the Mount Dall conglomerate (Figs. 9A–9G) at several local- are minor components of some samples. Skeletal fragments are locally abun- ities within the middle 500 m of its stratigraphic extent—the interval studied dant and may be partly or completely replaced by silica. in detail by Sunderlin (2008). Sand grains and coarser clasts in our samples Limy layers are chiefly skeletal supportstone with common non-carbonate are mainly chert (many with rare to abundant radiolarians) and fine-grained grains. Echinoderm, brachiopod, and diverse bryozoan bioclasts predominate, carbonate lithologies consistent with a deep-water setting such as calcareous with lesser pelecypod, cephalopod, gastropod, and rugose coral debris (Fig. radiolarite, muddy spiculite, and tentaculitid limestone (Figs. 9D, 9E). Bioclastic 9J). Many skeletal grains are abraded, and some are bored. A few samples wackestone to grainstone, containing crinoids, bryozoans, foraminifers, algae, consist almost exclusively of calcareous prisms that are likely shell fragments and local ooids and likely derived from a shallow-water environment, occurs of the Permian prismatonacreous bivalve genus Atomodesma (Fig. 9I). The mainly as boulders (20–30 cm in diameter; Figs. 9F, 9G). Other subordinate prisms are slightly curved, 10–40 µm thick, and as much as 1.5 mm long; some clast types include intraformational conglomerate (Fig. 9B), and sandstone to display dark and light bands from tens to hundreds of microns thick that are siltstone made up of mostly of monocrystalline quartz, carbonate, and feld- probable growth bands. The curvature and slenderness of these prisms differ- spar. Volcanic lithic clasts (Fig. 9D) are rare components of some samples, and entiate them from those of Cretaceous inoceramid bivalve shells (Kauffman distinctive grains of phosphatic radiolarian chert occur in several. As noted by and Runnegar, 1975). Bradley et al. (2003), metamorphic lithic clasts are absent. Several compositionally distinct types of chiefly clast-supported conglom- erate and pebbly sandstone have been included in the Permian unit. The first type overlies Proterozoic calcareous and pelitic schist and consists of pebbles Detrital Zircon Data and granules of calcschist, quartz-mica schist, and chloritic schist in a limy, sandy matrix that contains Permian brachiopods (Patton and Dutro, 1979; Pat- A composite sample of pebble conglomerate and interbedded sandstone ton et al., 1980) as well as fragments of bryozoans, echinoderms, and pris­ at locality 11 (Fig. 4; Table 2) produced abundant Devonian and Carbonifer- matonacreous bivalves. Non-carbonate grains are 20%–50% of the matrix and ous detrital zircon grains and an array of older Paleozoic and Precambrian include quartz, albite, white mica, chlorite, and biotite. A sample of this matrix

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processed for conodonts yielded only phosphatic brachiopod fragments and this sample is distinct from all other samples described herein, yielding PDP phosphatized spines, spicules, and bryozoan zoecial steinkerns (Table 1). cross-correlation coefficients ranging from 0.00 to 0.09 (Table S3 [footnote 1]; A second compositional variant is massive limestone conglomerate (Figs. Saylor and Sundell, 2016). 9H, K, L) ~50 m thick that overlies Devonian carbonate strata at locality 2 (Fig. The age spectrum for the limestone conglomerate (sample 97ADw119) is 2). Patton et al. (1980) tentatively assigned a Cretaceous age to this section, distinct from that of the fossiliferous sandstone. It has some statistical simi- but noted that it could be as old as Permian. Cretaceous rocks in the Med- larity to samples 11AD2A (Sheep Creek Formation; Fig. 7A) and 03ADw415C fra quadrangle are typically dominated by clasts of quartz and chert (Patton (lower Mystic assemblage; Fig. 8A), producing PDP cross-correlation coeffi- et al., 1980), leading Andrews and Rishel (1982) and Bradley et al. (2003) to cients of 0.51 and 0.58, respectively (Table S3 [footnote 1]; Saylor and Sundell, favor a Permian age for the strata at locality 2. Beds are 20 cm to 2 m thick; 2016). Otherwise, this sample does not appear to be similar to any of the other meter-thick cross-beds occur locally. Imbricate clasts indicate that current samples considered herein. transport was toward the southeast (Bradley et al., 2003). Beds are clast sup- ported and contain rounded pebbles and cobbles up to 9 cm in diameter in a matrix of fine- to very coarse-grained sandstone; 40%–90% of the sand-sized Depositional Setting and coarser clasts in samples we examined are carbonate. Dominant clast types are peloid (± bioclast) grainstone with ≤20% quartz and feldspar silt, Faunal and sedimentologic data indicate that the Permian succession in fine crystalline dolostone, lime mudstone, slightly to strongly recrystallized the Medfra quadrangle accumulated primarily in a shallow-marine setting metalimestone, and medium- to coarse-crystalline calcitic marble (Fig. 9L). with a temperate paleoclimate. Most of the sandstones and conglomerates Non-carbonate clasts are mainly metamorphic and sedimentary lithic frag- contain marine fossils and probably represent strandline deposits. Atom­ ments, quartz, mica, and chert. odesma is an epifaunal to semi-infaunal bivalve that occupied a variety of inner sublittoral habitats (Kauffman and Runnegar, 1975). Intervals such as the massive limestone conglomerate at locality 2 (Fig. 2) that lack indigenous Detrital Zircon Data fossils could have formed in a fluvial environment. The echinoderm- and bryozoan-dominated fauna (e.g., James, 1997) and Our samples were collected from limy, micaceous quartz siltstone and the presence of atomodesmid bivalves (Kauffman and Runnegar, 1975) sug- sandstone containing Permian fossils at locality 1 and limestone conglomerate gest a temperate paleoclimate during deposition of the Permian succession. at locality 2 (Fig. 2; Table 2). The limestone conglomerate (sample 97ADw119) Prismatic debris derived from Atomodesma and related forms has been contained a broad array of Paleozoic and Proterozoic grains, and the young- identified elsewhere in Alaska, chiefly from areas with mid-paleolatitude est age population is 369 ± 5 Ma (Famennian). In contrast, the fossiliferous settings during the Permo-Triassic (Silberling et al., 1997): the Arctic Alaska– sandstone sample (97ADw122) yielded abundant Permian and Early Triassic Chukotka terrane (Dover et al., 2004, their loc. 98), the Rampart Group in the detrital zircon (28% of all grains analyzed) together with minor Late Devonian Livengood area (Brosgé et al., 1969), the Tahkandit Limestone in east-cen- (Famennian), mid-Silurian, Neoproterozoic, and Paleoproterozoic age popula- tral Alaska (Laurentian margin; Brabb and Grant, 1971), and the Goodnews tions (Fig. 8A). The youngest single grain analyzed was Late Triassic (ca. 229 terrane in southwestern Alaska (Kauffman and Runnegar, 1975). The trilo- Ma), but it does not overlap with any of the other analyses. The next-youngest bite identified by Hahn and Hahn (1993) from Permian strata in the Medfra grains (n = 20) range in age from ca. 271 to 239 Ma, and they all overlap within quadrangle also suggests a temperate to cool-water setting, as it belongs to 2σ uncertainty and have a weighted average age of 256 ± 4 Ma with a MSWD of a genus known only from Upper Carboniferous and Lower Permian rocks 1.4 (see inset in Fig. 8A; Table S2 [footnote 1]). Thus, we interpret these grains of the Arctic (Yukon Territory, Canada; Ellesmere Island, Nunavut, Canada; to make up a single population and define an earliest late Permian depositional Spitsbergen, Norway). age for this sample—an age compatible (within uncertainty) with the fossil age reported by Patton et al. (1994). The presence of one Late Triassic and five Early Triassic grains in this sample raises the possibility of a Triassic depositional UPPER TRIASSIC CONGLOMERATES age, and there are Triassic strata mapped nearby in the same area. However, the Triassic rocks are lithologically very different from the rocks collected for Upper Triassic sedimentary rocks occur widely but sparsely throughout the this study that also contain Permian fossils (Patton et al., 1977, 1980). Mystic subterrane (Fig. 3). In the north and west (areas A and B), they consist The fossiliferous sandstone (sample 97ADw122) is quite dissimilar from all of shallow-water carbonate successions that deepen upward into chert and other samples described so far because of the prominent Permian age prob- mudstone (Silberling et al., 1997; McRoberts and Blodgett, 2002); elsewhere ability peak, and the MDS plot shows that it is separated from all of the other (areas C through F; Bundtzen et al., 1997), strata of this age include shale, chert, samples it is compared with (Fig. 8C). Quantitative metrics also show that conglomerate, and volcaniclastic sandstone interlayered with and intruded by

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mafic igneous rocks that are further discussed below. New detrital zircon data contain common carbonate clasts, including lime mudstone, dolostone, sparry described below indicate that two intervals of carbonate- and chert-clast con- calcite, and calcareous spiculite. Monocrystalline quartz grains are notable in glomerate in area E are of likely Late Triassic age. These strata have some the sandy layers; feldspar grains are minor. Rare clast types include dark mud- lithologic similarities to Triassic rocks in the Medfra quadrangle (area A), as stone, granular phosphate, quartz-carbonate sandstone with echinoderm de- well as to the Permian Mount Dall conglomerate in area F. bris, and bivalve shell fragments made of prismatic calcite. A 20-cm-diameter clast of fine-grained carbonate processed for conodonts was barren (Table 1). Bundtzen et al. (1997) described chert-cobble pebble conglomerate as a part of Southeastern McGrath Quadrangle subunit lJs (Lower Jurassic) of their Tatina River volcanics, but detrital zircon data (discussed below) suggest a Triassic age for this lithology. Rocks at locality 12 (Figs. 4, 10A–10C) were originally included in the Sheep Creek Formation and tentatively correlated with the Permian Mount Dall con- glomerate by Bundtzen et al. (1997). The section consists of >100 m of mas- Detrital Zircon Data sive, mainly clast-supported conglomerate with a maximum clast diameter of ~8 cm (average ~2–3 cm; Fig. 10B). Strata we examined lacked sedimentary Detrital zircon data (Fig. 11) come from two samples of feldspathic sandy structures; Bundtzen et al. (1987) reported local pebble imbrication suggestive matrix of the carbonate clast conglomerate at locality 12, and a sample of of crude channel configurations. Rounded pebbles of fine-grained limestone fine-grained sandstone with abundant cherty clasts at locality 13 (Fig. 4; Table predominate (Fig. 10C); some limy clasts contain minor amounts of quartz silt, 2). The three spectra have youngest grain population ages of 208 ± 3 to 218 ± dolomite rhombs, and/or micritic peloids. Bioclasts are rare, and none could 3 Ma (Late Triassic; Norian), and all samples have prominent age probability be specifically identified. The conglomerate has a sandy matrix of carbonate peaks at ca. 420 Ma and few Precambrian grains. The sample from locality clasts with subordinate grains of monocrystalline quartz, locally abundant feld- 13 also contains a few Permo-Carboniferous grains that define a minor age spar, and rare chert. population at ca. 267 Ma (n = 3; Table S2 [footnote 1]) and a single Juras- A composite sample of clasts and matrix yielded conodont elements of sic grain (ca. 186 Ma). The MDS plot in Figure 11C illustrates the similarity Ordovician(?) and Silurian–Devonian age that had been variously heated and between the two carbonate clast conglomerate samples (UT1 and UT2 in deformed (J. Repetski, 2017, personal commun.; Table 1). Conodont color alter- Fig. 11C) and their separation from the fine-grained sandstone (UT3). The ation index values of individual elements are 2.5(?), 3, 4, and 4.5 and indicate detrital zircon age spectrum for the fine-grained sandstone is more similar to that host rocks reached temperatures ranging from ~100 to 300 °C (Epstein et those of the Lower Jurassic sedimentary samples (see below) and the Sheep al., 1977). Some conodont elements are texturally “pristine” whereas others Creek composite data because it has a broader array of Paleozoic grains and are severely fractured. These findings imply that the conglomerate at locality a larger (though still minor) proportion of Precambrian ages. Quantitative 12 was derived from rocks that experienced a range of thermal and deforma- metrics show broad similarity among the three Triassic samples, with PDP tional histories prior to their Triassic redeposition. cross-correlation coefficients ranging from 0.74 to 0.81 (Table S3; Saylor and Although the conglomerate at locality 12 is grossly similar to carbonate Sundell, 2016). clast–rich parts of the Mount Dall conglomerate, the two units differ in some petrographic details. Carbonate clast types are more diverse in the Mount Dall, and fossiliferous limy clasts are more abundant. The feldspathic sandy matrix TRIASSIC–JURASSIC MAFIC IGNEOUS AND ASSOCIATED locally prominent at locality 12 has no counterpart in the parts of the Mount SEDIMENTARY ROCKS Dall section that we studied. Mafic igneous rocks (basalt, diabase, and gabbro) of Late Triassic and/or Early Jurassic age occur in areas C through F of the Mystic subterrane and East-Central McGrath Quadrangle have been called the Tatina River volcanics in area E by Bundtzen et al. (1997) (Figs. 2, 3). Late Triassic (Norian) ammonites and halobid and monotid bivalves Strata at locality 13 (Fig. 4) occur within the Triassic–Jurassic Tatina River occur in shale that is interlayered with basalt and agglomerate in areas D and volcanics as mapped by Bundtzen et al. (1997). About 15 m of fine-grained to E (Bundtzen et al., 1994, 1997), and Triassic(?) radiolarians are found in chert pebbly sandstone and clast-supported conglomerate (Figs. 10D–10F) overlie interbedded with basalt in area C (Gilbert, 1981). However, B.L. Reed (1976, more than 20 m of dark-weathering siltstone. Maximum clast size is ~10 × 20 personal commun.) suggested that some mafic igneous rocks in the eastern cm; most clasts are 0.5–6 cm in diameter. McGrath quadrangle (area E) were Jurassic, on the basis of field relations with Chert clasts predominate in sandstone and conglomerate, and include ar- sedimentary strata containing Early Jurassic fossils (Table 1, sample 76AR13). gillaceous, dolomitic, and radiolarian-rich variants (Figs. 10E, 10F). Pebbly beds New geochemical and isotopic data (Table S5 [footnote 1]) from mafic igneous

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Figure 11. Detrital zircon kernel density estimate (KDE) diagrams (A), cumulative distribution function plot (B), and multi-dimensional scaling (MDS) plot (C) for samples of Triassic, Jurassic, and Cretaceous strata. See Table 2 and Figure 4 for sample descriptions and locations. KDEs were generated using adaptive kernel density estimation (Vermeesch, 2012); each histogram bin represents ~25 m.y. The vertical bands in panel A approximately represent the following time periods: purple = Silurian (ca. 444–419 Ma); blue = Mississippian and Pennsylvanian (ca. 359–299 Ma); pink = Triassic (ca. 252–201 Ma); green = Jurassic (ca. 201–145 Ma). Solid lines between symbols in the MDS plot represent nearest neighbors, and dashed lines represent next-nearest neighbors. Short sample labels in parentheses in A are keyed to symbols in the MDS plot (“SCcomp” in panel C refers to the Sheep Creek Formation composite data set shown in Figure 7), and stress value is indicated by “S” (Vermeesch, 2013). Note that sample 11AD203C is not included in the Upper Triassic composite data set.

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rocks in area E (Figs. 2, 12) and detrital zircon data from correlative strata in Detrital Zircon Data area F (Figs. 2, 11) help us to better understand these rocks. Map unit Pzbs in the Talkeetna quadrangle map of Reed and Nelson (1980) consists of pillow basalt, pyroxene gabbro, agglomerate, tuff, and associ- Geochemical and Isotopic Data ated sedimentary strata that may correlate with the rocks described above. At locality 16 (Figs. 4, 10J, 10K), we collected one sample of volcaniclas- Most outcrops we examined in area E are diabase, but at locality 14 (Fig. tic tuffaceous sandstone that contains abundant andesitic lithic clasts and 4), altered vesicular basalt (sample 11AD20A; Fig. 10I) is interlayered with lime- glassy shards altered to chlorite. These strata differ from the Upper Triassic stone containing poorly preserved corals (Figs. 10G, 10H). Overall, mafic igne- conglomerates and the Lower Jurassic sedimentary rocks described above ous rocks typically have diabasic textures of jackstraw plagioclase and intersti- and below, respectively, because they are directly associated with volcanic tial clinopyroxene, with strong but variable static replacement by greenschist rocks and contain substantial volcanic detritus. The sample (11AD203C, Table facies minerals (dominantly chlorite, epidote, and calcite). Major elements 2) yielded a small number of detrital zircons (n = 21) with the youngest age (Table S5 [footnote 1]) were affected by low-grade metamorphism, but some population at ca. 226 Ma (n = 3; Fig. 11A; Table S2 [footnote 1]), which is con- generalizations can be made about them. The rocks are all tholeiitic basalts sistent with a Triassic depositional age. However, the sample also contained

(based on high FeOtotal/MgO) ranging from 46% to 53% SiO2. Titanium (as TiO2) a single grain of Jurassic age (ca. 196 Ma; Table S1). Other grains are of Pa- averages 2.1%, but ranges from 0.8% to 3.4%. leozoic and Precambrian age, with a minor age population at ca. 1045 Ma (n Trace element data (Fig. 12; Table S5 [footnote 1]) are consistent with for- = 4; Fig. 11; Table S2). Quantitative metrics show that this sample has some mation in a continental rift setting as previously suggested by Bundtzen et al. similarity to sample 97ADw119 (Medfra Permian(?) sample in Fig. 8), with a (1997). On a plot of the immobile elements Hf-Th-Ta (Fig. 12A; Wood et al., PDP cross-correlation coefficient of 0.58 (Table S3; Saylor and Sundell, 2016), 1979), most of the samples are in the field representing enriched or plume- although both of these samples yielded relatively small numbers of detrital type mid-ocean ridge basalt (E-MORB), continental rift basalts, and/or conti- zircon. Comparisons with all other samples yielded PDP cross-correlation co- nental flood basalts. Two samples plot separately in the subduction-related arc efficients of 0.29–0.03 (Table S3). magma field. On multi-elemental plots (spidergrams) normalized to normal mid-ocean ridge basalt (Fig. 12B; Sun and McDonough, 1989), most samples are similar to E-MORB and ocean island basalt (OIB), with the exception of LOWER JURASSIC SEDIMENTARY ROCKS the two samples that plotted anomalously in Figure 12A. These samples show evidence for depletion of Nb and Ta relative to the light rare earth elements (i.e., La) which we attribute to subduction processes. Field occurrence and sec- Lithologies and Fossil Data ondary mineral suites of these two samples are similar to those of our other samples. We infer they are part of the Late Triassic–Early Jurassic suite and Jurassic sedimentary rocks are widely but sparsely distributed in the suspect that their distinct geochemical characteristics were inherited from Mystic subterrane (Fig. 3). We describe here lithologies, fossil assemblages, their magma sources. and detrital zircon data from five newly recognized localities in area E that Neodymium isotopic data (Table S5 [footnote 1]) were obtained for a sub- contain Lower Jurassic strata. Four are along the southeastern boundary of set of the mafic igneous samples, including the two apparently subduction-re- the Farewell terrane and on trend with Early Jurassic fossil localities previ-

lated samples. All samples yielded ƐNd values ranging between +1.2 and +4.9. ously documented in area F (Talkeetna quadrangle; e.g., Reed and Nelson,

The ƐNd values do not correlate with SiO2, MgO, or Sm/Nd; such a correlation is 1980), but locality 17 (Fig. 4) is within a large expanse previously mapped as expected when older crust is assimilated during fractionation. Instead, we inter- Dillinger subterrane. pret the isotopic values to reflect the composition of the magma source materi- Lower Jurassic strata in the northwestern Talkeetna quadrangle were als. Depleted mantle model ages calculated from these data range from 1.0 to included in the Kahiltna assemblage by Reed and Nelson (1980; their map 0.6 Ga, indicating that the mafic rocks most likely derived from partial melting of ca. unit KJs) but were described by these authors as a lithologically and fau- 1.0 Ga subcontinental mantle lithosphere beneath the Farewell terrane. The mag- nally distinctive subunit of reddish-brown weathering sandstone and dark mas were not derived by direct partial melting of the asthenosphere or oceanic gray shale that contains ammonites, brachiopods, and pelecypods. Jurassic mantle. Mafic magmatism is a common feature in rift-related tectonic environ- rocks form small outcrops that overlie strata of the Dillinger subterrane, and ments, and we tentatively interpret these mafic igneous rocks to represent a Late they are isolated from the main mass of Kahiltna flysch. Their contact with Triassic and/or Early Jurassic rifting or extensional event in or around the Fare- Dillinger strata is generally a fault but locally was interpreted as an angular well terrane. However, independent structural or sedimentologic evidence for unconformity (Jones and Silberling, 1979; Reed and Nelson, 1980). Jones and rift-related tectonism during this time period has not yet been identified. Silberling (1979) noted that Jurassic strata, which they considered part of

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Figure 12. Geochemical plots for Late Triassic–Early Juras- sic mafic igneous rocks from the Mystic subterrane (sam- ples colored the same in each plot; see Table S5 [footnote 1] for data). (A) Hf-Th-Ta plot of Wood et al. (1979) show- ing Mystic subterrane samples with fields for oceanic and continental igneous rocks generated in different tectonic environments; most Mystic samples fall in the field of enriched mid-ocean ridge basalt (E-MORB), continental rift, and continental flood basalts; two samples fall in the subduction-related (crustal contamination) magma field. N-MORB—normal mid-ocean ridge basalt; OIB—ocean island basalt. (B) Multi-element plots (“spidergrams”) of Mystic subterrane igneous samples normalized to N-MORB compositions (after Sun and McDonough, 1989); examples are also given (from Sun and McDonough, 1989) of E-MORB and OIB, oceanic arc (Kermadec arc: Smith et al., 1997), and continental arc (Chilean Andes: Turner et al., 2016). Shaded gray box shows position in spidergrams of Nb and Ta, elements relatively depleted in arc-related igneous rocks. Most Mystic sample compositions range between those of typical E-MORB and OIB (also charac- teristic of continental rift or flood basalts). Two samples (shown by dashed lines) have arc-like compositions, al- though with less prominently depleted Nb-Ta.

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their Dillinger terrane, are a few tens of meters thick, include limy and phos- Detrital Zircon Data phatic layers, and are directly overlain by Lower Cretaceous rocks in some areas, as described below. The fauna of the Jurassic rocks is quite diverse and We obtained detrital zircon data from strata containing Jurassic fossils at includes belemnites and crinoids in addition to forms listed above; the most three localities (locs. 17, 20, and 21, Fig. 4), from quartzose sandstone intruded precisely dated fossils indicate an age of early Early Jurassic (early Sinemu- by diabase (loc. 15, Fig. 4), and from a similar sandstone ~10 km to the north- rian; Table 1). east (loc. 19, Figs. 4, 11; Table 2). All five samples produced age spectra that Thin sections from Jurassic limestone at locality 18 (Fig. 4; Reed and are broadly similar, with prominent, and in four samples dominant, age popu- Nelson, 1980, their loc. 28) that were examined for this study consist of cri- lations between ca. 427 and 409 Ma and a diverse range of Precambrian ages noidal grainstone with fragments of pelecypods, brachiopods, bryozoans, (Fig. 11). Both sandstone samples and two of the fossiliferous samples con- and possible red algae. Some bioclasts are bored, and some have micritic tained Early Jurassic age populations ranging from ca. 195 to 184 Ma (Fig. 11). rims. Scattered non-carbonate grains (≤5%–10%) are mainly notably rounded The third fossiliferous sample (13AD409D, loc. 17)—the most compositionally monocrystalline quartz, with subordinate clasts of chert, siltstone, phosphate, and texturally mature—yielded an Early Devonian youngest age population and volcanic rocks. (409 ± 10 Ma; Table S2 [footnote 1]), two Permian grains (ca. 267 and 257 Ma), In the eastern McGrath quadrangle, rocks with Jurassic fossils (Table 1) oc- and a single earliest Cretaceous grain (ca. 144 Ma; Table S1). This sample also cur along trend from the Talkeetna Jurassic localities. According to Reed and contained the largest number of Precambrian grains. The MDS plot (Fig. 11C) Nelson (1980), Jurassic strata in the McGrath quadrangle are intercalated with shows clustering of all of the Jurassic samples except the one noted outlier pillow basalt and volcanic flows. However, Bundtzen et al. (1997) interpreted (LJ4, sample 13AD409D). All of the Lower Jurassic samples and one of the Up- pillow basalt in this area as part of a Triassic map unit (Trab) overlain by a per Triassic samples (UT3, sample 11ADw119A) also cluster together with the 45-m-thick section (their map unit lJs) that contains Jurassic bivalves (Table Sheep Creek Formation composite data set (SC comp in Fig. 11C), indicating 1; Elder and Miller, 1991); unit lJs comprises bluish-white phosphatic shale, notable similarity among them. Quantitative metrics show variable similarity volcaniclastic sandstone, and chert-clast conglomerate. among the Jurassic samples, with PDP cross-correlation coefficients ranging Our findings support a Jurassic age for some mafic igneous rocks in the from 0.84 to 0.01 (Table S3; Saylor and Sundell, 2016). McGrath quadrangle, and indicate the occurrence of several distinct Jurassic lithologies in the McGrath and Lime Hills quadrangles (Fig. 4). Strata on trend to the southwest of unit lJs, but mapped as part of the Kahiltna assemblage Depositional Setting by Bundtzen et al. (1997), include very fine-grained quartz-carbonate sand- stone (locs. 15, 19, and 20, Fig. 4; Figs. 13A–13C) that is unlike any petrofacies Lithologic and faunal data from our new samples and previous collections described from the Kahiltna (e.g., Karl et al., 2013, 2015). Carbonate (as grains constrain the depositional setting of Lower Jurassic strata in areas E and F. The and cement) makes up 15% to >80% of our samples; non-carbonate grains non-carbonate component in our samples is compositionally mature (quartz are mainly monocrystalline quartz (Fig. 13B), with lesser plagioclase feldspar, dominated) and locally texturally mature (predominantly rounded grains). chert, sedimentary lithic clasts, chlorite, and white mica. A carbonate-rich ver- These features, in addition to the presence of phosphate and bored bioclasts, sion of this lithology at locality 20 (Table 1) produced Early Jurassic (Sinemu- are consistent with condensed sedimentation forming winnowed lag deposits rian) ammonites (Fig. 13C) similar to those found in the Talkeetna quadrangle. on a shelf. The spiriferid brachiopod species identified by Sandy and Blodgett A more quartz-rich sandstone is intruded by diabase at locality 15 (Fig. 10L). (2000) at locality 28 of Reed and Nelson (1980) suggests a temperate or low-lat- Sandy coquinoid limestone in the Lime Hills quadrangle (locs. 17 and 21, itude setting. Mesozoic spiriferids generally preferred deeper-water shelf en- Fig. 4; Fig. 13D) yielded bivalves of Sinemurian age, including a distinctive vironments, but the ecologic niche of the Talkeetna species has not yet been oyster species also found in the Talkeetna faunas (R. Blodgett, 2014, personal determined (Sandy and Blodgett, 2000). Oyster coquinas at our localities 17 commun.; Table 1). Monocrystalline quartz grains are a minor but ubiquitous and 21 probably accumulated in relatively shallow- and warm-water (tropical component of limy beds at both localities. Bivalve coquinas at locality 21 also to subtropical) settings (R. Blodgett, 2014, personal commun.). contain foraminifers, gastropods, and crinoid fragments. Those at locality 17 are associated with distinctive, very fine- to medium-grained sandstone sim- ilar in composition to the quartz-rich sandstone at localities 15 and 19, but CRETACEOUS STRATA containing notably more rounded quartz grains as well as clasts and patches of phosphate (Figs. 13E, 13F). X-ray diffraction (XRD) analysis of a sample of Lower Cretaceous (pre-Albian) strata—the youngest part of the Farewell this sandstone confirms the presence of ~10% phosphate (apatite group), in terrane (Decker et al., 1994)—are most thoroughly documented in the Med- addition to 64% quartz, 15% plagioclase (anorthitite), and 12% illite (A. Boehlke, fra quadrangle (Patton et al., 1977, 1980). Here we provide new petrographic 2014, personal commun.). information on the Medfra quadrangle rocks, describe a newly discovered

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and partly coeval succession in area E, and identify additional occurrences Albian (or Younger?) Strata of correlative strata in area F (Figs. 2, 3). We also present detrital zircon evi- dence for the existence of siliciclastic strata of Albian or younger age that are Lithologies in contact with rocks of the Farewell terrane in areas A and F. Two sections of sedimentary rocks intimately associated with strata of the Mystic subterrane appear, on the basis of calculated minimum ages of detri- Aptian and Older Strata tal zircon populations, to be Albian (late Early Cretaceous) or younger. The first is in the Medfra quadrangle (loc. 3, Fig. 2) and consists of unfossiliferous In the Medfra quadrangle (Figs. 2, 3), Lower Cretaceous rocks that depo- siliciclastic strata that overlie Devonian shallow-water carbonate rocks of the sitionally overlie Triassic (to Jurassic?) strata comprise three subunits, each Nixon Fork subterrane. Patton et al. (1980) suggested a Cretaceous age for the bounded by an unconformity (Patton et al., 1977, 1980). Sandy, fossiliferous siliciclastic section, but Andrews and Rishel (1982) considered it to be Perm- limestone makes up the lowest subunit, which is 20 m thick. Fossils include ian because it is locally overlain by coquinoid limestone bearing a diverse as- belemnites and pelecypods (Buchia sublaevis, Buchia crassicollis) that indi- semblage of Permian fossils. The siliciclastic rocks are fine-grained sandstone cate a Valanginian age. These rocks are overlain by 90 m of Hauterivian and interbedded with pebbly sandstone and conglomerate with subangular to sub- Barremian siltstone, sandstone, and conglomerate that contain the belem- rounded pebbles to 1 cm in diameter. Gray, black, and green chert makes up nite Acroteuthis sp. as well as inoceramid bivalves. Coarser layers consist 40%–60% of clasts in both fine- and coarse-grained strata; many chert grains mostly of quartz, calcareous bioclasts, chert, and metamorphic lithic clasts in contain abundant radiolarians and/or siliceous sponge spicules (Fig. 13J). Sub- various proportions; bioclasts are mainly relatively equant inoceramid shell ordinate clast types include monocrystalline quartz, brown mudstone, phyllite, prisms (100–140 µm thick). The uppermost subunit is 210 m of dark mudstone quartz-mica schist, and plagioclase feldspar. with sparse, rounded granules and pebbles of chert and rare cephalopods The second locality is in the Talkeetna quadrangle (loc. 16, Fig. 4). Here ~5– including Tropaeum sp. of Aptian age. Fauna and lithology indicate that the 10 m of micaceous sandstone, siltstone, and dark argillite with possible plant Lower Cretaceous succession accumulated in a deepening-upward marine fragments and/or mud chips topographically underlie altered tuffaceous(?) environment. and volcaniclastic rocks that we include in the Triassic–Jurassic mafic igneous Lower Cretaceous limestones approximately coeval with the lower two rock unit discussed above. Sandstone is very fine to medium grained, poorly Cretaceous subunits in the Medfra quadrangle were found immediately above sorted, and heterogeneous, with grains of monocrystalline and polycrystalline Lower Jurassic strata at locality 17 in the Lime Hills quadrangle (Figs. 4, 13E). quartz, plagioclase and potassium feldspar, white mica, biotite, and chlorite, The Mesozoic section here is highly condensed (<10 m thick), folded, and as well as chert (some with radiolarians), and an array of other sedimentary, locally intruded by felsic dikes. Cretaceous rocks weather brown to tan to red- volcanic, metamorphic, and plutonic lithic clasts (Fig. 13K). dish orange and form irregular beds 5–30 cm thick (Figs. 13E, 13G). Two faunally distinct lithofacies are recognized (R. Blodgett, 2014, personal commun.; Table 1). The older is closely to moderately packed bivalve shell coquina of early Early Detrital Zircon Data Cretaceous (Berriasian–Valanginian, most likely Valanginian) age. It consists mainly of thin (0.7 mm to ≤100 µm thick) disarticulated valves and fragments Detrital zircon samples from both localities have youngest grain popula- of Buchia sp. with minor quartz silt and rare belemnite fragments in a matrix tions of ca. 105 Ma (late Albian; Fig. 11A) along with prominent Early Juras- of argillaceous micrite (Figs. 13G, 13H). The younger is fine-grained limestone sic age populations at ca. 193 Ma and an array of Paleozoic and Precambrian of middle Early Cretaceous (Hauterivian–Barremian) age made up chiefly of the grains. These spectra are similar to those from parts of the Cretaceous Kahiltna prismatic elements of inoceramid bivalves, with rare larger shell fragments (Fig. assemblage, which is an overlap succession exposed south and east of the 13I), a few belemnite rostrums, and locally abundant foraminifers, calcispheres, southeastern margin of the Farewell terrane (Ridgway et al., 2002; Kalbas et and radiolarians. al., 2007; Hults et al., 2013). Several meters of Lower Cretaceous limestone, interbedded with chert and siltstone, overlie Lower Jurassic strata in area F (west-central Talkeetna quad- rangle; Jones and Silberling, 1979; Reed and Nelson, 1980, their locs. 24 and 28; LIVENGOOD AND WHITE MOUNTAINS TERRANES Table 1). Valanginian pelecypods (Buchia crassicollis solida; R. Imlay, 1975, per- sonal commun.) are found in these rocks, which in thin section consist mostly of Middle Paleozoic siliciclastic rocks that are partly coeval with the lower disaggregated inoceramid shell prisms, minor rounded to subangular monocrys- part of the Mystic succession include the Devonian Cascaden Ridge unit in talline quartz sand, rare mudstone clasts, and traces of other bioclasts including the Livengood terrane and the Mississippian(?) Globe unit in the White Moun- ostracodes and foraminifers. tains terrane (Fig. 1). New detrital zircon data from these units allow us to test

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proposed linkages between Livengood-area strata and the Farewell terrane The MDS plot in Figure 14C shows that the Globe and Cascaden Ridge that were based on faunal and lithologic correlations (e.g., Blodgett et al., 2002; samples are distinct from one another despite the overlap in the youngest Dumoulin et al., 2014). age populations. The Globe quartzite sample is most similar to the Sheep Creek Formation composite data set (SC comp in Fig. 14C) and other strata that cluster in the same region of the plot. The Cascaden Ridge sample plots Lithologies and Fossil Data closer to the composite data set for our “lower Mystic assemblage” (LM comp in Fig. 14C) and has the strongest similarity to the composite data set The Cascaden Ridge unit (Weber et al., 1992) consists mainly of interbed- for Upper Triassic strata described above (UTr comp in Fig. 14C). The MDS ded shale, siltstone, and graywacke, with subordinate polymictic conglomer- plot shows that the detrital zircon spectra for the Globe unit and the Keno Hill ate and limestone, and a locally recognized (Twelker et al., 2016) layer of peral- quartzite of Beranek et al. (2010) cluster closer together relative to other sam- kaline rhyolite. Cascaden Ridge limestone contains a diverse Middle Devonian ples and sample composites, but the PDP cross-correlation coefficient of 0.17 biota of brachiopods, bryozoans, calcareous algae, conodonts, rugose and suggests a low degree of similarity (Table S3 [footnote 1]). Faunal features of tabulate corals, echinoderms, gastropods, orthoconic nautiloids, ostra­codes, strata associated with the Globe unit and Keno Hill quartzite suggest different pelecypods, plant fragments, scaphopods, stromatoporoids, tentaculitids, and regions of origin for these two units, and comparison of their detrital zircon trilobites (Weber et al., 1994). Gastropods are most like those from coeval Fare- age spectra is consistent with this interpretation. well terrane units to the southwest and have Siberian paleogeographic affin- ities (Blodgett et al., 2002), but trilobites resemble species from the Canadian Arctic Islands (Weber et al., 1994). Conglomerate clasts include chert, mud- CORRELATIONS AND POTENTIAL CLASTIC SOURCES WITHIN stone, sandstone, and felsic to intermediate igneous rocks (Athey and Craw, THE FAREWELL TERRANE 2004). Petrographic analysis of graywacke suggests a collision orogen source, with some local input from the underlying Ordovician Livengood Dome Chert Devonian and younger strata discussed above have similarities and differ- (Gergen et al., 1988). ences with coeval rocks elsewhere in the Farewell terrane that illuminate the The Globe unit (Weber et al., 1992; Wilson et al., 2015) consists of gray, fine- overall evolution and history of this crustal fragment. Petrographic and detrital to medium-grained, partly bimodal quartzite that is massive to thinly interbed- zircon data indicate that Paleozoic and Mesozoic clastic strata of the Mystic ded with slate, phyllite, or claystone and intruded by Triassic mafic igneous subterrane were likely derived at least in part—though not exclusively—from rocks. The unit is unfossiliferous and largely fault bounded; the Mississippian erosion of older parts of the Farewell terrane. age is based on lithologic correlation with the Keno Hill quartzite in the Yukon Territory (Weber et al., 1992). As noted above, however, lower Paleozoic rocks in the White Mountains terrane have faunal features that suggest non-Lauren- Devonian Strata tian affinities and argue against correlation of White Mountains terrane strata with coeval units in western Canada (e.g., Dumoulin et al., 2014). Lithofacies like the bedded barite, concretion-bearing black shale, and phosphatic chert described above have not been reported from correlative strata in other parts of the Mystic subterrane. At least four small barite occur- Detrital Zircon Data rences have been found in the central Lime Hills quadrangle (area D, Fig. 2); like the Gagaryah deposit described above, they may have formed as sedimen- Our sample of the Cascaden Ridge unit (loc. CR, Fig. 1) is fine- to medi- tary-exhalative deposits (Bundtzen et al., 1994). However, occurrences in the um-grained sandstone with subequal amounts of carbonate clasts (including central Lime Hills quadrangle are a few meters or less thick and consist chiefly crinoid fragments), monocrystalline quartz, and chert. It has a prominent age of massive beds, lesser veins, breccias, and nodules that are hosted by carbon- population at 410 ± 4 Ma that indicates an Early Devonian maximum deposi- ate rocks of the Barren Ridge Limestone (uppermost unit of the Dillinger sub- tional age, along with a scattering of older Paleozoic and Proterozoic grains terrane; likely Early Devonian age). The central Lime Hills quadrangle barites (sample 07ADw703A, Fig. 14). Our sample from the Globe unit (loc. G, Fig. 1) are thus smaller and older (if they are indeed syngenetic) than the Gagaryah is fine grained and made up of ~80%–90% subangular to rounded grains of deposit, and are not associated with organic-rich black shale. monocrystalline quartz and minor amounts of chert, sedimentary lithic clasts, Fossil data suggest that strata equivalent to Devonian coral-bearing shale and tourmaline. The detrital zircon spectrum (sample 07ADw702A, Fig. 14) is in the southern Mystic subterrane may also occur to the north. Corals found somewhat similar to that from the Cascaden Ridge unit, with a nearly coeval in float near Permian strata in the Medfra quadrangle (Table 1) are coeval with Early Devonian maximum depositional age (408 ± 5 Ma) but a considerably corals found as concretions in black shale in the McGrath quadrangle, but smaller proportion of Devonian grains. the depositional position of the Medfra corals is uncertain (W. Patton, 1999,

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Figure 14. Detrital zircon age kernel density estimate (KDE) diagrams (A), cumulative distribution func- tion plot (B), and multi-dimensional scaling (MDS) plot (C) for samples in the White Mountains and Livengood terranes, published data from the Keno Hill quartzite (Beranek et al., 2010), and composite spectra from Mystic subterrane strata; see Table 2 and Figure 1 for sample descriptions and locations. KDEs were generat- ed using adaptive kernel density estimation (Vermeesch, 2012); each histogram bin represents ~25 m.y. The relative probability curves for the Lower Mystic assemblage com- posite and the Lower Jurassic com- posite data sets are vertically exag- gerated five times and two times, respectively. Solid lines between symbols in the MDS plot represent nearest neighbors, and dashed lines represent next nearest neighbors. Short sample labels in parentheses in A are keyed to symbols in the MDS plot, and stress value is indi- cated by “S” (Vermeesch, 2013).

personal commun.). The Medfra form (Sociophyllum sp. cf. S. glomerulatum) Upper Sheep Creek Formation is of Givetian (late Middle Devonian) age and compares most closely with a species found in northern Laurentia (Northwest Territories, Canada). The Med- Siliciclastic turbidites that compose the upper part of the Sheep Creek For- fra corals could have come from clasts in Permian conglomerate, or from con- mation differ from turbidites of the underlying Dillinger subterrane in overall cretions in a poorly exposed (shaly?) interval below the Permian strata. If the lithologic sequence and petrography. Carbonate interbeds are generally rare latter interpretation is correct, their depositional setting could be analogous to or absent in Sheep Creek turbidite sections, in contrast to the Devonian Barren that of redeposited Middle Devonian corals in the McGrath quadrangle. Addi- Ridge Limestone, which is dominantly a carbonate unit, and the Silurian Terra tional study of field relations is needed to understand the significance of the Cotta Mountains Sandstone, which contains abundant interbeds of pure lime- Medfra Givetian corals. stone (e.g., calcareous radiolarite) and calcareous sandstone and conglomerates

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made up chiefly of carbonate clasts (e.g., Bundtzen et al., 1997). The Sheep Creek has plant debris not found in the Dillinger units and locally abundant late Paleo- zoic fossils. Lastly, Sheep Creek sandstones typically contain more chert clasts and less mica and metamorphic lithic clasts than do the Silurian–Devonian Dil- linger turbidites. Petrography of Sheep Creek turbidites also differs from that of the partly coeval “Mystic assemblage” of Malkowski and Hampton (2014), which contains abundant mafic volcanic clasts. Comparison of detrital zircon spectra of our Sheep Creek Formation sam- ples with composite plots for Silurian–Devonian Dillinger subterrane turbidites (Barren Ridge Limestone and Terra Cotta Mountains Sandstone) shows strong similarity between the three units (Fig. 15). The MDS plot in Figure 16 shows that the three composite data sets cluster together, with the Sheep Creek (SC) and Barren Ridge (BR) points essentially overlapping. Quantitative metrics for comparison of the three composite data sets also indicate strong similarity, with PDP cross-correlation coefficients of 0.76 for the comparisons (Table S3 [footnote 1]; Saylor and Sundell, 2016). Many Sheep Creek turbidite sections lack precise age control, and our detrital zircon results are consistent with the interpretation that much of this lithofacies is of Devonian age and contains a detrital zircon population largely to entirely derived through recycling of un- derlying Dillinger strata. However, even our samples from beds bearing late Paleozoic fossils (locs. 4 and 5, Fig. 4) contained only two grains of late Paleo- zoic age (ca. 258 and 300 Ma in sample 11AD3A; Fig. 7). Our findings thus sug- gest that although the Sheep Creek Formation and the Mystic assemblage may be at least partly coeval, the source(s) of late Paleozoic zircons and volcanic clasts that supplied Mystic assemblage turbidites did not obviously contribute sediment to the Sheep Creek Formation.

Other Upper Paleozoic Strata

Our findings, combined with those of Malkowski and Hampton (2014), indicate that at least five upper Paleozoic lithofacies can be distinguished in the Mystic subterrane on the basis of petrography and detrital zircon age spectra (Table 3). The first, described above, is the upper Paleozoic part of the Sheep Creek Formation, which generally lacks volcanic clasts and detrital zircon age populations younger than Devonian. The second is typified by our three samples from map unit Pzus (Reed and Nelson, 1980), which contain Figure 15. Detrital zircon kernel density estimate (KDE) plots for composite sample sets from notable volcanic lithic clasts and Mississippian detrital zircons. Despite some this study together with published data for the Nixon Fork and Dillinger subterranes (Brad- ley et al., 2014; Dumoulin et al., 2018b), Keno Hill quartzite (Beranek et al., 2010), lower and subtle variation in detrital zircon age populations between our three sam- upper Mystic assemblage of Malkowski and Hampton (2014), and selected samples from the ples, the composite detrital zircon age spectrum (denoted by Pzus in Fig. 15) Alexander terrane (Beranek et al., 2014; Tochilin et al., 2014). KDEs were generated using adap- compares favorably with the composite spectrum from the “lower Mystic as- tive kernel density estimation (Vermeesch, 2012). Medfra indicates samples from the Medfra 1:250,000-scale quadrangle; Pzus is map unit of Reed and Nelson (1980); MH denotes data from semblage” of Malkowski and Hampton (2014) (Fig. 15). The composites also Malkowski and Hampton (2014). Number in parentheses for each sample indicates the number cluster together on the MDS plot in Figure 16 (LM and LMA, respectively) and of grains represented by the age probability curve. The blue bar highlights the approximate have a PDP cross-correlation coefficient of 0.60 (Table S3 [footnote 1]). Thus, age range of the Devonian (ca. 419–359 Ma), and the brown bar highlights the age range of we provisionally include all five samples in the “lower Mystic assemblage.” distinctive Proterozoic detrital populations (ca. 2000–1800 Ma) identified by Bradley et al. (2014) in Nixon Fork subterrane strata. NA—North America. The lower Permian Mount Dall conglomerate has a detrital zircon spec- trum quite similar to that of the “lower Mystic assemblage” (Figs. 15, 16) but

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rhythmically interbedded siltstone and fine-grained sandstone in tabular beds 2–15 cm thick, intercalated with bedded chert, siliceous to tuffaceous mudstone, tuff, and mafic volcanic rocks in layers 20 cm to 15 m thick (Malkowski, 2010). Beds of chert and volcanic rocks do not occur in any of the Sheep Creek sections we studied and are not mentioned in the definition of the formation by Bundtzen et al. (1997). The two samples grouped in the “upper Mystic assemblage” by Malkowski and Hampton (2014) yielded a bimodal Paleozoic age distribution with prominent Silurian and Permian age populations. The composite age spectrum is shown in Figure 15, and it is notably different from other spectra described so far. If youngest detrital zircon age populations from “Mystic assemblage” samples represent depositional ages, then the succession was deposited in at least two pulses during Carboniferous to Permian time. If so, only the younger Permian pulse appears to have reached the McGrath quadrangle. The MDS plot in Figure 16 shows that the upper Mystic assemblage (UMA) is more similar to other Perm- ian successions than to the lower Mystic assemblage, suggesting the presence of diverse sediment sources during the late Paleozoic within the Mystic subterrane. Both petrographic and detrital zircon data from Permian strata in the Medfra quadrangle differ from those of upper Paleozoic strata in the Mystic assemblage. Figure 16. Non-metric multi-dimensional scaling (MDS) plots after Vermeesch (2013) of detrital zircon samples from our study compared with those from other areas of Alaska and western The Permian age population of the Medfra sample is considerably younger than Canada. See text for explanation of samples. Short sample labels are explained in the table those of the two upper Mystic assemblage samples of Malkowski and Hampton to the right. Solid line denotes nearest neighbor in dissimilarity space; dashed line denotes (2014). Abundant metamorphic lithic clasts and micas in the Medfra strata—ab- next-nearest neighbor; stress value is indicated by “S” (Vermeesch, 2013). References for data shown on the plot are given in text; Medfra indicates samples from the Medfra 1:250,000-scale sent from the Mystic assemblage—could have been derived from the metamor- quadrangle; MH denotes Mystic assemblage (ass.) data of Malkowski and Hampton (2014). phic basement of the Nixon Fork subterrane that locally underlies the Permian rocks (Patton et al., 1980). Neoproterozoic age populations in the detrital zircon age spectra from both Medfra samples could reflect input from Nixon Fork base- differs from these strata in composition and depositional setting. Chert clasts are ment rocks and/or Neoproterozoic siliciclastic strata like those at the base of the abundant in both successions, but volcanic detritus is rare in the Mount Dall. Nixon Fork succession at Lone Mountain (Figs. 2, 15; Bradley et al., 2014). Clasts Carbonate clasts are more numerous in the Mount Dall and include a distinc- in the limestone conglomerate resemble various parts of the Nixon Fork carbon- tive component of Carboniferous crinoidal-bryozoan limestone. Dillinger subter- ate succession; clasts of peloidal grainstone with abundant quartz and feldspar rane units are a plausible source for the chert and deep-water carbonate clasts silt correspond particularly well to a common lithofacies of the Ordovician Novi that predominate in the Mount Dall (Bradley et al., 2003). Other detritus may be Mountain Formation (Dumoulin et al., 2002). derived from unit Pzus, such as the Devonian limestone clasts ascribed to this Limy beds in the Medfra quadrangle Permian section contain a fauna of source by Reed and Nelson (1980). Younger carbonate layers in unit Pzus (e.g., brachiopods, bryozoans, pelecypods, corals, trilobites, and echinoderms that is loc. 7, Table 1) are a possible source for the Carboniferous crinoidal limestone grossly comparable to that of coeval or slightly older rocks at White Mountain boulders, whose large size implies a nearby provenance. The limestones in both (area C, Figs. 2, 3; J.T. Dutro, 1982, personal commun.; Hahn et al., 1985; Hahn the layers and the boulders have similar faunas and likely formed as well-win- and Hahn, 1985) and Lime Lakes (area D, Figs. 2, 3; J.T. Dutro, 1982, 1983, personal nowed lag deposits. Distinctive pebbles of phosphatic radiolarian chert in the communs.; C. Stevens, 1985, 2016, personal communs.; Hahn and Hahn, 1985). A Mount Dall are texturally identical to the “blackball” chert in unit Pzus (Reed and detailed comparison of the faunas from these three localities, and an analysis of Nelson, 1980). their biogeographic implications, would be very useful. The “upper Mystic assemblage” of Malkowski and Hampton (2014) includes two samples. One sample from unit Pzus has a volcanic clast–rich composition that is similar to that of their “lower Mystic assemblage.” The other sample (FSC- Triassic Conglomerate 02 of Malkowski and Hampton, 2014) comes from rocks mapped by Bundtzen et al. (1997) as Sheep Creek Formation in the central McGrath quadrangle (Fig. Detrital zircon, fossil, and petrographic data suggest that carbonate- and 4). The sample consists of fine- to medium-grained sandstone for which no pet­ chert-clast conglomerate in the east-central and southeastern McGrath quad- rographic details are available (B. Hampton, 2014, personal commun.). It was rangle was derived in part from older rocks of the Farewell terrane. Detrital taken 12 m below the top of a 160-m-thick measured section made up mostly of zircon spectra are generally similar to those from the Sheep Creek Formation,

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Barren Ridge Limestone, and Terra Cotta Mountains Sandstone (Fig. 15), and CORRELATIONS AND POTENTIAL CLASTIC SOURCES OUTSIDE the MDS plot shows spatial clustering of the composite data sets for all of THE FAREWELL TERRANE these units (Fig. 16). Lime mudstone is a common lithology in both the Barren Ridge Limestone and Terra Cotta Mountains Sandstone, and a subordinate part Detrital zircon and petrographic data imply that sources outside the Fare- of the underlying Post River Formation. Conodont ages from the composite well terrane must have contributed detritus to most of the Mystic subterrane sample at locality 12 (Table 1) are consistent with a Dillinger subterrane source. units described above. In particular, sources are needed for zircons of Late Chert (including radiolarian chert) is present in Dillinger units and in Devonian Devonian, Carboniferous, Permian, Late Triassic, and Early Jurassic age. Mal- strata of the Mystic subterrane. Although Triassic zircons could conceivably kowski and Hampton (2014) proposed that during Carboniferous–early Perm- have been derived from Triassic igneous rocks of the Mystic subterrane, the ian time, the Farewell terrane was situated in the Panthalassic Ocean, along predominantly mafic composition of these rocks suggests that a source out- the western margin of the Slide Mountain Ocean (Fig. 17B), receiving mate- side the Farewell terrane is more likely; possible sources are discussed below. rial from arc and recycled orogen sources of the Alexander and Wrangellia Upper Triassic strata in the Medfra quadrangle (area A) include intervals insular terranes. In their reconstruction, and those of Nelson et al. (2013) and of carbonate-clast conglomerate and intraclastic breccia (Patton et al., 1980; Beranek et al. (2014), the Yukon-Tanana and related peri-Laurentian terranes Silberling et al., 1997) that have some similarities to the McGrath quadrangle are also positioned along the western margin of the Slide Mountain Ocean conglomerates of presumed Triassic age. Clasts in the Medfra samples that at this time. In this section, we summarize potential magmatic sources in in- we examined are mostly fine-grained carbonate, and many are dolomitic and/ sular and peri-Laurentian terranes, as well as oceanic terranes to the west, that could have contributed detrital zircons to Mystic units. We also consider or phosphatic. Less-common coarser-grained lithologies include peloid and potential correlations between the uppermost part of the Farewell terrane and ooid-bioclast grainstones that are strikingly similar to, and may have been de- the Kahiltna assemblage, and between Farewell and the White Mountains and rived from, lower Paleozoic limestones of the Nixon Fork subterrane. Non-car- Livengood terranes. bonate clasts include monocrystalline quartz, chert, and dark brown mud- stone. The presence of dolomitic and phosphatic clasts in the Medfra section provides an intriguing compositional link with the McGrath conglomerate at Alexander-Wrangellia-Peninsular Composite Terrane locality 13 (Fig. 4).

The Alexander terrane in southeastern Alaska and western Canada (Fig. 1) is a Neoproterozoic–Jurassic crustal fragment made up of the Craig, Jurassic and Cretaceous Strata Admiralty, and northern Alexander subterranes (Nelson et al., 2013; Beranek et al., 2014). Wrangellia extends from southcentral Alaska (Fig. 1) and the Yukon Lower Jurassic sections in areas E and F sampled for this study are mainly to at least Vancouver Island (Canada) and is characterized by Triassic flood quartz-carbonate sandstone and sandy fossiliferous limestone. Partly(?) coeval basalts (Jones et al., 1977). The Peninsular terrane (Fig. 1) underlies the Alas- rocks elsewhere in the Mystic subterrane are fine-grained siliceous strata that kan Peninsula and consists chiefly of Triassic–Jurassic magmatic rocks (e.g., gradationally overlie Upper Triassic carbonate successions in the Medfra and Rioux et al., 2010). Both Wrangellia and the Peninsular terrane have Paleozoic Taylor Mountains quadrangles, and overlie Triassic mafic igneous rocks in the basement complexes that include late Paleozoic igneous rocks (Beranek et al., central Lime Hills quadrangle (areas A–C, Figs. 2, 3; Patton et al., 1980; Reed et 2014). Beranek et al. (2014) proposed that assembly of the Alexander-Wrangel- al., 1985; Silberling et al., 1997; LePain et al., 2000; Karl et al., 2011). Radiolarian lia-Peninsular composite terrane began in the Middle–Late Pennsylvanian and ± spiculitic chert is the main lithology in all three areas, interbedded with silt- was completed by the early–middle Permian. stone, sandstone, and—in the Lime Hills section—tuff. Early Jurassic belem- Silurian–Middle Devonian faunas in the Craig subterrane have some sim- noid cephalopods and bivalves occur in the Taylor Mountains strata (McRob- ilarities to those of Farewell (e.g., Blodgett et al., 2002; although cf. Antosh- erts and Blodgett, 2002; Karl et al., 2011), and Pliensbachian (middle Early kina and Soja, 2016), and detrital zircon spectra from lower Paleozoic rocks Jurassic) radiolarians are found in the central Lime Hills quadrangle (Reed et in the two areas are also similar (Dumoulin et al., 2018b). Silurian–Lower al., 1985). Lithofacies and faunas of the Jurassic sections in areas A–C indicate Devonian turbidites in the Dillinger subterrane of Farewell contain abun- a deeper-water setting than correlative rocks in areas E and F, but phosphate dant Silurian and Early Devonian detrital zircons that have no known local nodules reported from area B (Karl et al., 2011) provide a link with phosphate (within Farewell) source but that may have been derived from the Alexander occurrences in areas E and F. terrane and/or from a common Caledonide source (Dumoulin et al., 2018b), Cretaceous strata have not been identified within the Farewell terrane out- suggesting relative proximity of the two terranes during the early Paleozoic. side of the strata discussed above in areas A, E, and F. These rocks have poten- Recent work suggests that this proximity may have continued into (or re- tial correlatives in other parts of Alaska that are discussed below. curred during) the late Paleozoic. Malkowski and Hampton (2014) argued that

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Figure 17. Paleogeographic setting of Cordilleran exotic terranes of “Arctic” affinities. (A) Late Devonian–Missis- sippian. (B) Pennsylvanian–Early Permian. (C) Late Triassic. (D) Early Jurassic. Diagrams are adapted from Nelson et al. (2013) and are modified to show our preferred alterna- tive positions of the Farewell (FW) terrane (solid outline) with respect to the Arctic Alaska, Alexander, and related terranes; modification in B follows that of Malkowski and Hampton (2014). Blue brick pattern denotes platforms, continental margins, and(or) inactive arcs signified by car- bonate or siliciclastic strata. Terranes with “Arctic” affinity are shown in yellow. Terranes with Laurentian or Siberian affinity are shown in blue and purple, respectively. Late Paleozoic terranes formed on the western side of the Slide Mountain ocean are shown in green (McCloud belt of Col- pron and Nelson, 2011). Gray arrows, where present, show inferred direction of plate motion. Continent abbrevia- tions: AFR—Africa; ARB—Arabia; BAL—Baltica; IND—In- dia; KAZ—Kazhakstania; LAU—Laurentia; MEX—Mexico; SAM—South America; SEU—southern Europe; SIB—Sibe- ria. Terrane abbreviations: AA—Arctic Alaska; AX—Alex- ander; EK—Eastern Klamaths; FW—Farewell; Ku—Kutcho; NS—Northern Sierras; OK—Okanagan subterrane; OM— Omulevka; PE—Pearya; PN—Peninsular; QN—Quesnellia; RB—Ruby; ST—Stikinia; WR—Wrangellia; YR—Yreka; YT—Yukon-Tanana.

detrital zircon U-Pb and Hf isotope analyses from their Mystic assemblage As noted above, Mesozoic igneous rocks are widespread in the Alex- matched most closely with magmatic source areas of the Alexander terrane ander-Wrangellia-Peninsular composite terrane. Triassic flood basalts in and Wrangellia. Igneous rocks of Late Devonian, Mississippian, and Early– Wrangellia (middle Ladinian to Norian; ca. 239–225 Ma) are partly coeval Middle Pennsylvanian age, summarized by Beranek et al. (2014), are found with Norian rifting in the Alexander terrane (Nelson et al., 2013). A magmatic mainly in Wrangellia, although Late Devonian gabbro (363 Ma) occurs in the arc of Late Triassic–Middle Jurassic age was then established in southern northern Alexander, and Tochilin et al. (2014) reported an orthogneiss of lat- Wrangellia, roughly correlative with the ca. 212–153 Ma Talkeetna arc in the est Devonian age (359 Ma) in their Banks Island assemblage, which may be Peninsular terrane (Rioux et al., 2010; Nelson et al., 2013). part of the Alexander terrane. Plutonic suites of Late Pennsylvanian–Permian Detrital zircon data from upper Paleozoic–Triassic strata of the Alexander age are documented in both Wrangellia and Alexander: the Skolai arc and terrane may be compared with Mystic subterrane age spectra (Figs. 15, 16). related rocks (320–285 Ma) in the former (Malkowski and Hampton, 2014), Pebbly sandstone from the Permian Halleck Formation in southern Alexan- and the Barnard Glacier suite (307–301 Ma) and Donjek Glacier suite (291–284 der (Craig subterrane) and possibly coeval metasedimentary rocks from the Ma) in the northern Alexander terrane (Beranek et al., 2014). Banks Island assemblage (Tochilin et al., 2014) yielded age spectra (Fig. 15)

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with similarities to those from the upper Mystic assemblage (Malkowski and strata that form part of the Tikchik terrane. Late Triassic and Early Jurassic arc Hampton, 2014) and the Mount Dall conglomerate (Fig. 16). Early Permian, volcanic and plutonic rocks occur in the Togiak terrane, interpreted to deposi- Late Devonian (Famennian), and Silurian detrital zircon age populations oc- tionally overlie the Tikchik terrane, and Triassic and Jurassic detrital zircons cur in the Halleck spectra, and Late Pennsylvanian, Famennian, and Early occur in Upper Triassic and Lower Jurassic strata of that overlapping terrane. Devonian age peaks occur in the Permian(?) Banks Island composite spec- trum (Fig. 15). Spectra reported from other upper Paleozoic–Triassic rocks in the Alexander terrane are less similar to those of coeval Farewell samples. Kahiltna Assemblage Unpublished data from five samples of the uppermost Cannery Formation (Upper Devonian–Permian) in the Admiralty subterrane yielded a single age Aptian and older Cretaceous strata in the Farewell terrane are at least partly cluster ranging from 350 to 300 Ma and no older grains (Ward et al., 2014). coeval with the older portion of the Kahiltna assemblage (Ridgway et al., 2002), The Triassic Nehenta Formation produced a single peak age of Early Devo- which is exposed along the southern margin of the Farewell terrane through- nian (417 Ma) and no other grains (Fig. 15; Tochilin et al., 2014). Unpublished out the central and western Alaska Range. Parts of the Kahiltna and correlative data from two samples of the Triassic Burnt Island Conglomerate yielded a strata contain sparse fossils of Late Jurassic–early Early Cretaceous (Kimme- 220–250 Ma population with older grains ranging from 295 to 370 Ma (Ward ridgian to Valanginian) age (Wallace et al., 1989; Ridgway et al., 2002) and yield et al., 2014). youngest detrital zircon age populations ranging from Late Jurassic to early Late Cretaceous (Kalbas et al., 2007; Hampton et al., 2010; Hults et al.,, 2013). The Kahiltna consists mainly of siliciclastic flysch; limestone is rare and found Yukon-Tanana Terrane by Kalbas et al. (2007) only north of the Denali fault in the northwestern Tal- keetna quadrangle, chiefly near the base of their section EF1, where graded The Yukon-Tanana terrane of east-central Alaska (Fig. 1) includes overlap- fossil hash grainstone, fossiliferous siltstone, and micrite contained belem- ping arc successions of Late Devonian to middle Permian age that developed nites and inoceramid bivalves. Blodgett and Clautice (2000) documented above a pre-Devonian metasedimentary basement of probable western Lau- similar lenses of shell-rich Valanginian limestone in the Kahiltna in the Healy rentian affinity (Colpron et al., 2015). Two main pulses of felsic magmatism at quadrangle to the northeast. Valanginian limestones of the Mystic subterrane 365–330 Ma and 264–252 Ma are documented (Nelson et al., 2006; Beranek and resemble the shelly limestones in the Kahiltna, but are not interbedded with Mortensen, 2011), and the terrane was intruded by Late Triassic–Early Jurassic siliciclastic turbidites. plutons (ca. 220–178 Ma; Colpron et al., 2015). These igneous ages overlap the Hauterivian–Barremian inoceramid limestone in the Lime Hills quad- ages of Late Devonian–Jurassic detrital zircons in many of the Mystic subter- rangle may be coeval with Kahiltna assemblage strata in the McGrath A-2 rane units discussed above. 1:63,360-scale quadrangle (southeastern part of the McGrath 1:250,000-scale quadrangle) that contain Inoceramus sp. of possible Hauterivian age (Bundt- zen et al., 1987, their fossil loc. 32). Lime Hills inoceramid limestone is fau- Tikchik-Togiak Terranes nally and lithologically similar to coeval units in the Peninsular terrane such as the Nelchina Limestone and the Herendeen Formation (e.g., Nokleberg et The Tikchik and Togiak terranes of southwestern Alaska (Decker et al., al., 1994). Rocks of this age in the Medfra quadrangle are richer in siliciclastics 1994) are potential sources of detrital zircons of Late Devonian, Carbonifer- than the Lime Hills strata, but limier than most of the Kahiltna. No lithologic ous, Permian, Late Triassic, and Early Jurassic age, although rocks composing and faunal match for the Aptian mudstone unit in the Medfra quadrangle has these terranes have only been mapped and studied at a reconnaissance level. been identified in adjacent Alaskan terranes. An arc volcanic sequence in the Tikchik terrane has interbedded carbonates As noted above, the Albian or younger strata found within the Farewell ter- that yielded Late Devonian–Early Mississippian conodonts (Box et al., 1993). A rane at localities 3 (Fig. 2) and 16 (Fig. 4) are lithologically similar to part of the dacite from higher in that sequence yielded an unpublished U-Pb zircon age of Kahiltna assemblage, and may represent outliers of that unit or related rocks. ca. 318 Ma (Carboniferous) with an oceanic neodymium isotopic composition The petrographic composition and detrital zircon spectra of sandstone at both (Box et al., 2015b). This arc is interpreted to have collided with the present Farewell localities match well with those of Kahiltna strata from the north side southwestern edge of the Farewell terrane in Pennsylvanian–Early Permian of the basin that were largely derived from older, northern source terranes time, and much of the Tikchik terrane is composed of a structural complex of such as Farewell and Yukon-Tanana (Hults et al., 2013; Karl et al., 2013). Silici- boudinaged rocks that include sandstones with Silurian and older detrital zir- clastic flysch of the Cretaceous Kuskokwim Group, which is broadly similar to con signatures (Box et al., 2007; Karl et al., 2007) similar to those from strata of and partly correlative with the Kahiltna assemblage, crops out along the north- the Dillinger subterrane of the Farewell terrane (Dumoulin et al., 2018b). Perm- western boundary of the Farewell terrane in the Medfra quadrangle (Wilson et ian detrital zircons are abundant in Permian and Triassic post-collisional basin al., 2015). No detailed petrographic or detrital zircon data have been published

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from the Kuskokwim in this area, but it is reasonable to assume that the Albian adjoined northern Laurentia and the Alexander terrane moved from the pa- or younger rocks at locality 3 (Fig. 2) may be a fault sliver of this unit. leo-Arctic into the paleo-Pacific. Recent studies (Beranek et al., 2014; Malkowski and Hampton, 2014) have proposed that Farewell was proximal to the Alexan- der-Wrangellia-Peninsular composite terrane by the late Paleozoic. Our new Livengood and White Mountains Terranes data from Mystic subterrane strata illuminate the Devonian through Mesozoic evolution of the Farewell terrane, suggest connections with other Alaskan ter- Detrital zircon data from mid-Paleozoic strata in the Livengood and White ranes, and raise questions for further research. Mountains terranes have similarities with spectra from coeval (and younger?) rocks in the Mystic subterrane and argue against a previously proposed cor- relation with rocks in the Yukon. Spectra from the Cascaden Ridge and Globe Devonian units have similar detrital zircon age populations despite the much greater number of Early Devonian grains in the Cascaden Ridge. Spectra from these Devonian rocks in the Mystic subterrane include shallow-water carbonate two samples also have some similarities with many of our Mystic subterrane and siliciclastic strata and a variety of deep-water lithologies (Fig. 3). Fossilifer- spectra (Fig. 15). The MDS plot in Figure 16 shows that the Globe unit is more ous limestones of Early to Middle Devonian age that overlie deep-water rocks similar to the composite Sheep Creek Formation data set (and most similar to of the Dillinger subterrane in areas D–F are coeval with, and likely depositional the Terra Cotta Mountains Sandstone data set), whereas the Cascaden Ridge or tectonic outliers of, the youngest part of the Nixon Fork platform. Post–Mid- sample is more similar to the Mystic assemblage data sets described above. dle Devonian shallow-water carbonate rocks in the Farewell terrane are limited The Cascaden Ridge sample is most similar to the Upper Triassic composite in spatial and temporal extent (Fig. 3). If they were ever part of a carbonate data set (Fig. 16), reflecting similarly high proportions of Early Devonian– and platform comparable in size to the Nixon Fork platform, most of this edifice has Silurian-age grains in both spectra. Comparative detrital zircon data (Table been removed by erosion. Alternatively, their widely dispersed distribution is S3 [footnote 1]) from the Globe unit and the Keno Hill quartzite in the Yukon consistent with deposition on a series of islands that were only periodically (Beranek et al., 2010) argue against the proposed correlation of these two within the photic zone and habitable by neritic fauna. units by Weber et al. (1992), as do faunal data that suggest a non-Laurentian Shallow-water fossiliferous limestone of Frasnian age is the thickest (up to origin for lower Paleozoic strata of the White Mountains terrane (Dumoulin 500 m; Bundtzen et al., 1994) and most widespread (areas C, D, and F, Figs. 2, et al., 2014). 3) Mystic carbonate unit. It contains a diverse biota that includes corals, bra- Upper Paleozoic and lower Mesozoic rocks in the Livengood and White chiopods, pelecypods, and gastropods, as well as algae and foraminifers, most Mountains terranes are limited in extent, but several units could profitably be similar to coeval biotas from western Canada (Alberta) and Eurasia (Russian targeted for future research to clarify the affinities of these terranes. Permian platform and the Urals; Mamet and Plafker, 1982; Bundtzen et al., 1994, 1997). rocks in the Livengood terrane (map unit Ps of Weber et al., 1992, 1994) in- Faunal and lithologic data suggest a very shallow, open marine environment clude sandstone and quartz and chert granule to pebble conglomerate that with local patch reefs (Mamet and Plafker, 1982). contain brachiopods, foraminifers, and conodonts; detrital zircon data and de- Mystic siliciclastic strata known to be Devonian are scarce. An interval ~100 tailed faunal analyses from these strata would be very useful. Geochemistry m thick of siltstone and shale in area E contains a Frasnian fauna and flora of Late Triassic (Carnian?) mafic igneous rocks (map unit Trm of Weber et al., suggestive of a shallow-water, nearshore setting (Blodgett and Gilbert, 1992). 1992) that intrude the Globe unit could be compared to that of Triassic–Jurassic Turbidites of the Sheep Creek Formation (areas D, E) could be, in part, of Fras- mafic igneous rocks in Farewell. nian or Famennian age (based on constraints from underlying strata), but they have produced no Devonian fossils. Thick, Lower Devonian arkosic redbeds like those typical of the Alexander terrane (Gehrels and Saleeby, 1987; Bazard IMPLICATIONS FOR TECTONIC EVOLUTION OF THE FAREWELL et al., 1995; Soja and White, 2016) and extensive Upper Devonian quartz-rich TERRANE fluvial strata like those widespread in Arctic Alaska (e.g., Moore and Nilsen, 1984) have no equivalents in the Farewell terrane. U-Pb zircon, fossil, and lithofacies data suggest that the Farewell, Arctic The most distinctive Devonian lithofacies in the Mystic subterrane are Alaska-Chukotka, and Alexander terranes had a shared early Paleozoic his- deep-water strata (barite and black shale, calcareous radiolarite, chert with tory in a paleo-Arctic setting (Blodgett et al., 2002; Dumoulin et al., 2002, 2014, phosphorite nodules) in areas E and F. These lithologies typically form in highly 2018b; Nelson et al., 2013). By the Devonian, connections between the three productive oceanographic environments such as coastal zones with upwelling terranes had weakened and their histories diverge. In the tectonic scenario currents—for example, in Carboniferous strata that host the Red Dog deposit of Nelson et al. (2013), Farewell remained near Siberia at a latitude of ~60° in Arctic Alaska (Dumoulin et al., 2004). Barite or phosphorite deposits of Late during middle through late Paleozoic time, whereas Arctic Alaska–Chukotka Devonian age are unknown in any other Alaskan terrane. They are ~25–35 m.y.

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older than Middle Mississippian phosphorites in Arctic Alaska (Dumoulin et and early Permian detrital zircons. Early Paleozoic and Proterozoic zircons al., 2004, 2011). Barite deposits similar to and approximately coeval with the in the southern Farewell units could be derived from older parts of the Alex- Gagaryah deposit have been found in the Selwyn Basin of western Laurentia ander terrane, or could be reworked from older parts of Farewell (e.g., Dil- (Goodfellow and Jonasson, 1984). linger subterrane). Matches between Dillinger lithofacies and specific Mystic Thus, available paleontologic and lithologic data provide no clear links be- clast lithologies described above support the latter conclusion. Virtually all of tween Farewell and other Alaskan terranes during the Late Devonian. Paleo- the Sheep Creek could have had such a recycled Dillinger provenance. The zoic faunal similarities between Farewell and Alexander are not documented data outlined above support a late Paleozoic position for the Farewell terrane in strata younger than early Middle Devonian (Eifelian; Blodgett et al., 2002). proximal to parts of the Alexander and Wrangellia terranes, as suggested Lithofacies indicative of high-productivity conditions may constrain Farewell’s by Malkowski and Hampton (2014), rather than a locality along the Siberian Devonian location. Phosphorites commonly form within 40° of the equator margin, as proposed by Nelson et al. (2013) (Fig. 17B). (e.g., Cook and McElhinney, 1979), implying a mid- or low-latitude setting for But the early late Permian (ca. 256 Ma) peak age of detrital zircons in Farewell during Late Devonian time. We suggest that a Late Devonian position rocks of the Medfra quadrangle (Fig. 8) is younger by >25 m.y. than peak for Farewell on the southern (Laurentian) side of the Uralian Sea is more con- zircon ages of the upper Mystic assemblage (ca. 282–298 Ma; Malkowski sistent with these constraints than is the more northerly location, adjacent to and Hampton, 2014), metamorphic ages in northern Farewell (284–285 Ma; Siberia, that was previously proposed (e.g., Nelson et al., 2013; Antoshkina and Bradley et al., 2003), and the latest documented ages of Permian igneous Soja, 2016) (Fig. 17A). Our preferred position for the Farewell terrane is also in activity in Alexander and Wrangellia (ca. 284–285 Ma; Beranek et al., 2014). agreement with faunal and lithologic data that indicate ties to Arctic Alaska This implies that Permian strata in northern Farewell were not deposited as and Alexander during early Paleozoic time. part of the Browns Fork orogeny and that their middle to late Permian zircons were not derived from Alexander or Wrangellia. The Medfra peak zircon age coincides instead with the 264–252 Ma pulse of magmatism in the Yukon-Ta- Carboniferous–Permian nana terrane (Nelson et al., 2006). Abundant Late Devonian detrital zircons in both of our Medfra samples (Fig. 8) could also have been sourced by Yu- Early Permian (284–285 Ma) metamorphic ages in northern Farewell have kon-Tanana. Parts of the Tikchik terrane (Box et al., 2015b) contain detrital been interpreted as dating a collisional event—the Browns Fork orogeny— zircons of ca. 260–255 Ma, but the depositional age of these strata (at least between Farewell and an unknown object (Bradley et al., 2003). Possible col- latest Permian and younger; S.E. Box, unpublished data) suggest that they lisional “objects” include the Innoko terrane northwest of Farewell (Bradley may be too young to have been a source for the middle to early late Permian et al., 2003) and an arc in the Tikchik terrane southwest of Farewell (Box et al., Medfra rocks. 2015b) (Fig. 1). Alexander and/or Wrangellia may also (or alternatively) have As noted above, recent paleogeographic reconstructions (Nelson et al., been involved in this collision (Beranek et al., 2014; Malkowski and Hampton, 2013; Beranek et al., 2014) have positioned both insular terranes (Alexander, 2014). Mystic rocks of late Paleozoic age are chiefly siliciclastic strata (Fig. 3), Wrangellia) and peri-Laurentian terranes (Yukon-Tanana) along the western and U-Pb detrital zircon data from these rocks suggest connections with sev- margin of the Slide Mountain Ocean during late Paleozoic time. If, as pro- eral Alaskan terranes during late Paleozoic time. These data shed new light posed by Malkowski and Hampton (2014), Farewell was near (colliding with?) on which sedimentary strata in the Farewell terrane may have accumulated the insular terranes by the early Permian, subsequent (middle to late Perm- during the Browns Fork orogeny, but raise additional questions as well. ian) interaction between Farewell and Yukon-Tanana is possible. Our data from upper Paleozoic units of southern Farewell are consistent Questions remain concerning Farewell’s late Paleozoic sedimentary re- with those of Malkowski and Hampton (2014) in implicating the Alexan- cord and history. How much of unit Pzus (Mystic assemblage)—and the der-Wrangellia-Peninsular composite terrane as a potential source of detri- Sheep Creek Formation—accumulated in the early Carboniferous? Youngest tus for some Mystic units and as a possible causative collisional agent for zircon age populations in the lower Mystic assemblage (Fig. 8) are consistent the Browns Fork orogeny. In particular, Late Devonian, Carboniferous, and with a Mississippian to Early Pennsylvanian depositional age, which in turn early Permian detrital zircons that are found in parts of the Sheep Creek For- might suggest proximity of Farewell to Alexander and/or Wrangellia (or Yu- mation, the Mystic assemblage, and the Mount Dall conglomerate, as well kon-Tanana?) during early to middle Carboniferous time. Alternatively, if the as the abundant mafic volcanic clasts in the Mystic assemblage, may have lower Mystic and much of the Sheep Creek were deposited along with the this provenance. Igneous rocks of the Yukon-Tanana terrane are an alternate upper Mystic and Mount Dall conglomerate as part of the Browns Fork orog- source for Late Devonian and Mississippian zircons but not for the Pennsyl- eny, then a variety of sediment sources with several different detrital zircon vanian–early Permian zircons found in the upper Mystic assemblage (Mal- profiles were being eroded during this orogeny. Unit Pzus was thought (Reed kowski and Hampton, 2014) and the Mount Dall (Fig. 8). The Tikchik terrane and Nelson, 1980) to depositionally underlie the Mount Dall, but detrital zir- (Box et al., 2015b) could also have supplied Late Devonian, Carboniferous, con data (Malkowski and Hampton, 2014; Figs. 3, 8) suggest that the two units

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are at least partly coeval. Further study may reveal why their detrital zircon affinities to low-latitude biotas of the Alexander terrane and Chulitna (Fig. 1; spectra are similar (Fig. 8) but their clast compositions are not. McRoberts and Blodgett, 2002), a small terrane southeast of Farewell that Upper Paleozoic carbonate strata occur in areas A and C–F (Figs. 2, 3) as includes Triassic limestone and pillow basalt (Silberling et al., 1994). Layers isolated outcrops or thin layers within siliciclastic sequences. Biotas in these of coralline limestone intercalated with altered vesicular basalt at locality 14 strata have generally not been described in detail or closely compared to (Fig. 4) provide a tie between the carbonate successions in areas A and B each other or to coeval assemblages in other Alaskan terranes. Trilobites are and coeval mafic igneous rocks of areas C–F (Fig. 2). Although ammonites, an exception. Specimens of latest Pennsylvanian–Permian age from areas halobid and monotid bivalves, and radiolarians are found in shale and chert A, C, and D were documented by Hahn and Hahn (1985, 1993); the area C interlayered with basalt in areas C–E (Gilbert, 1981; Bundtzen et al., 1994, fauna is the most diverse and has affinities with coeval assemblages from 1997), biogeographic affinities have not been determined for these faunas. Wrangellia (Rainbow Mountain area) as well as the Yukon, Spitsbergen, and Phosphate occurs in both Triassic and Jurassic strata in Farewell, as dis- Slovenia. As noted above, preliminary studies suggest a temperate climate cussed above, but is particularly notable in Lower Jurassic rocks in areas during deposition of Permian rocks in area A and of Pennsylvanian–Permian E and F, where it is associated at several localities with Sinemurian fossils. strata in area D (C. Stevens, 2016, personal commun.) Tethyan (warm-water) Lower Jurassic phosphatic rocks are unknown in other Alaskan terranes, but foraminifers, which occur in Carboniferous rocks of the Alexander terrane phosphate occurs in Sinemurian strata in southeastern British Columbia and (Mamet et al., 1993) and Permian strata of Wrangellia and peri-Laurentian adjacent Alberta, Canada (Poulton and Aitken, 1989), and in northern Yukon terranes such as Stikinia (e.g., Beranek et al., 2014), have not been found in (Poulton, 1997). No faunal or other features are known to link Farewell to Farewell. Paleofloral assemblages from the Mount Dall conglomerate have western Laurentian strata in Canada during the Jurassic, so the coeval phos- mixed phytogeographic affinities that suggest a mid-latitude setting (Sun- phates may reflect similar oceanographic settings rather than proximity. As derlin, 2008). Limestone and siliciclastic strata of the Tikchik terrane yielded was suggested for Devonian phosphatic strata of the Mystic, Lower Jurassic middle Permian faunas, including brachiopods and fusulinid foraminifers phosphatic rocks in Farewell likely formed in middle or lower paleolatitudes. (Karl et al., 2011), that are approximately coeval with some Mystic faunas, but Detrital zircon spectra from Upper Triassic(?) and Lower Jurassic rocks in no detailed information is available on the Tikchik fossils. Additional study areas E and F are generally similar to those from older Farewell strata such as of the biogeographic affinities of Paleozoic Mystic biotas should clarify ties the Sheep Creek Formation and Silurian–Devonian units of the Dillinger sub- between Farewell and other terranes during the late Paleozoic. terrane, with Early Devonian–Silurian probability peaks and an array of Prot­ erozoic grains (Fig. 15). Early Paleozoic and older grains could be reworked from underlying older units. Few zircons of Carboniferous–Permian age were Mesozoic found in our Mesozoic samples, although one Triassic(?) spectra (sample 11ADw119A) has a small Permian probability peak. In the paleogeographic reconstruction of Nelson et al. (2013), Farewell Norian (226–208 Ma) detrital zircon age populations in four samples was an isolated crustal fragment that moved from the paleo-Arctic into the and Early Jurassic (195–184 Ma) grains in four others were likely derived paleo-Pacific during late Permian to Jurassic time (Figs. 17C, 17D). However, from outside the Farewell terrane, as Mystic mafic igneous rocks of this the detrital zircon data outlined above suggest that Farewell was already in age contain little zircon. Late Triassic–Early Jurassic arc rocks in the Alex- the paleo-Pacific by the late Paleozoic and was receiving detritus from Alex- ander-Wrangellia-Peninsular composite terrane, similar arc rocks in the Tik- ander, Wrangellia, and, perhaps, the Yukon-Tanana terrane. Zircon data—and chik-Togiak terrane, and partly coeval plutons in the Yukon-Tanana terrane other lines of evidence—indicate continued interaction between Farewell and are all potential sources for the Mesozoic zircons in our samples, but sev- one or more of these terranes during the Mesozoic. eral lines of evidence lead us to favor Mesozoic proximity between Farewell Definitively uppermost Permian–Middle Triassic rocks have not been and the Alexander-Wrangellia-Peninsular composite terrane (Figs. 17C, 17D). found in the Farewell terrane, so Upper Triassic sedimentary strata and Triassic faunal ties between Farewell and Alexander were noted above. Ju- mafic igneous rocks of Late Triassic–Early Jurassic age provide the earliest rassic faunas in Farewell suggest a relatively warm-water, low- to mid-lat- constraints on Farewell’s Mesozoic history. Upper Triassic (Norian) neritic itude setting, compatible with the Jurassic position proposed for the Alex- carbonate rocks occur in areas A and B. Successions in both areas deepen ander-Wrangellia-Peninsular terrane at this time (e.g., Nelson et al., 2013). In upward, but strata in area B are thicker, have a more diverse fauna, and addition, Yukon-Tanana was affected by Jurassic and Early Cretaceous met- were deposited in somewhat shallower and/or warmer water (Silberling et amorphic events that have no counterparts in Farewell (Bradley et al., 2003). al., 1997; McRoberts and Blodgett, 2002). The association of temperate-water Late Triassic to Early Jurassic mafic igneous rocks in the Mystic sub- monotid species with the tropical to subtropical hydrozoan Heterastridium in terrane have chemical compositions characteristic of a rift setting and are area A suggests a low- to mid-latitude setting (Silberling et al., 1997; Mackay broadly similar to Late Triassic basalts in the Chulitna region to the southeast et al., 2003). Diverse corals, bivalves, and gastropods in area B have closest (Clautice et al., 2001; Gilman et al., 2009). Extensive Late Triassic basalts of

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Wrangellia are geochemically similar as well (Lassiter et al., 1995; Greene et al., nian–Permian and Triassic–Jurassic clastic strata of the Mystic were derived

2008), but the Wrangellia basalts have more primitive (i.e., higher) ƐNd values at least in part from older Farewell rocks, but sources outside Farewell are (+5.3 to +7.4) and are interlayered with a lower section of subduction-related igne- needed for zircons of Late Devonian, Carboniferous, Permian, Late Triassic, ous rocks. Middle and Late Triassic mafic rocks in the Alexander terrane of south- and Early Jurassic age. Potential sources for zircons of these ages include the eastern Alaska are considered to be rift related (Taylor et al., 2008; Steeves et al., Alexander-Wrangellia-Peninsular composite terrane, the Yukon-Tanana ter-

2016), but they also have more primitive ƐNd values (+4 to +9.5) and are associated rane, and the Tikchik and Togiak terranes. with rhyolitic rocks. Late Triassic basalts are known from the Togiak terrane to the Available data fit best with paleogeographic models in which the Farewell southwest (Box et al., 1993), but these rocks have subduction-related geochem- and Alexander terranes were in relative proximity through much of Paleozoic istry. Late Triassic and Early Jurassic basalts from the Angayucham and Tozitna and early Mesozoic time (Fig. 17). The presence of phosphorite nodules in terranes in northern Alaska are generally similar to Mystic mafic igneous rocks Upper Devonian strata of the Mystic subterrane imply a setting within 40° of (Barker et al., 1988; Pallister et al., 1989), but are interbedded with radiolarian the paleoequator, and support a middle Paleozoic position for Farewell on the chert, suggesting an oceanic plate seamount setting. In summary, the Late Trias- southern (Laurentian) side of the Uralian Sea, rather than the northern (Si- sic–Early Jurassic mafic igneous rocks of the Mystic sequence are geochemically berian) side as was previously proposed (Fig. 17A). The Alexander-Wrangel- similar to mafic rocks of comparable age in other Alaskan terranes, but they differ lia-Peninsular composite terrane is a likely source for Late Devonian, Carbon- in detail from most of these by their more “continental” isotopic composition or iferous, early Permian, and early Mesozoic zircons found in clastic units of by their association with more continentally derived sedimentary rocks. the southern Farewell terrane (Figs. 17B–17D). Middle to late Permian zircons The presence of similar Late Triassic rift-type mafic rocks in the Farewell, in northern Farewell may have a provenance in the Yukon-Tanana terrane. Wrangellia, and Alexander terranes, with differences outlined above attributed to Late Triassic to Early Jurassic mafic igneous rocks in the Mystic subterrane local contrasts in their crustal underpinnings, may indicate these terranes shared are similar to broadly coeval igneous rocks in the Wrangellia and Alexander a Late Triassic rift event and became separated at that time (Fig. 17C). Although terranes, and are possible evidence of a shared rifting event during the early the composite Wrangellia-Peninsular-Alexander terrane was clearly separated Mesozoic (Fig. 17C). Faunal data and the presence of phosphatic strata suggest from the Farewell terrane during Cretaceous sedimentation in the Kahiltna basin a relatively warm-water, low- to mid-latitude setting for Farewell in the Early (Ridgway et al., 2002; Hampton et al., 2010; Hults et al., 2013), it might have been Jurassic (Fig. 17D). Lower Cretaceous limestones and related strata that crop adjacent to the Farewell terrane in late Paleozoic time as suggested by our detrital out sparsely but widely in the Mystic subterrane may be marginal facies that zircon data and the data of Malkowski and Hampton (2014) discussed above. formed early in the development of the Kahiltna overlap assemblage. The Lower Cretaceous limestones that unconformably overlie Lower Jurassic rocks in northern and southeastern Farewell are partly coeval with older parts of the Kahiltna assemblage, an overlap succession that covers the inferred suture ACKNOWLEDGMENTS zone between Wrangellia and Farewell. Faunal and lithologic data suggest that We thank the Mineral Resources Program (USGS) for financial support of this study. Tom Bundt- zen, of Pacific Rim Geological Consulting, Inc., graciously provided helicopter and logistical sup- Cretaceous strata in the Farewell terrane could represent shallower-water, mar- port and guidance to key outcrops in the McGrath and Lime Hills quadrangles. Thanks also go to ginal facies of the northern Kahiltna basin. These strata are also partly coeval Paul Brenckle, Robert Blodgett, Jim Haggart, Terry Poulton, John Repetski, and Cal Stevens for with volcaniclastic rocks (e.g., Koksetna River sequence of Wallace et al. [1989]) fossil identifications, Sue Karl for point count data, Adam Boehlke for XRD data, members of the deposited on the southern side of the Kahiltna basin along the margin of the USGS Western Alaska Range Project for helpful discussions, and Constance Soja, an anonymous reviewer, and Jeff Benowitz for constructive comments on an earlier version of the manuscript. Peninsula-Wrangellia-Alexander composite terrane. Lower Cretaceous marginal Any use of trade, firm, or product names is for descriptive purposes only and does not imply components of the Kahiltna succession give way to thicker, more widespread endorsement by the U.S. Government. Upper Cretaceous strata toward the center of the basin. These younger strata indicate increased rates of subsidence and sediment accumulation and changing REFERENCES CITED sediment provenance (e.g., Kalbas et al., 2007; Hults et al., 2013) during the final Andrews, T., and Rishel, J., 1982, 1981 Annual report—Reef Ridge I–XIII project areas, Kuskokwim accretion of the Peninsula-Wrangellia-Alexander composite terrane along the Block, Volume 1 of 3: Anchorage, Alaska, Patino Inc., unpublished report, 40 p. southern Alaska margin. 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