Downloaded from gsabulletin.gsapubs.org on May 2, 2014 Geological Society of America Bulletin

Volcanosedimentary paleoenvironments of Ediacaran fossils in Newfoundland

Gregory J. Retallack

Geological Society of America Bulletin 2014;126, no. 5-6;619-638 doi: 10.1130/B30892.1

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Volcanosedimentary paleoenvironments of Ediacaran fossils in Newfoundland

Gregory J. Retallack† Department of Geological Sciences, University of Oregon, Eugene, Oregon 97302, USA

ABSTRACT INTRODUCTION felsic volcanic eruptions (Fisher and Schminke, 1984), but felsic eruptions of the deep sea are A new perspective on paleoenvironments The Ediacaran Conception Group of New- inferred mainly from ancient volcanic rocks of Ediacaran fossils of the upper Concep- foundland (Figs. 1 and 2) is best known because (Cas and Wright, 1987; Busby, 2005; Allen tion Group (Newfoundland) comes from of its diverse assemblage of the earliest known and McPhie, 2009). An important distinction geochemical and sedimentological study of large organisms (Lafl amme et al., 2004, 2007, for volcanosedimentary sequences is between volcanic tuffs and sedimentary rocks. Tuffs 2012a, 2012b; Narbonne et al., 2005; Clapham rocks produced by volcanic eruptions and those in the Conception Group have major- and et al., 2003, 2004; Gehling and Narbonne, 2007; produced by redeposition of older erupted mate- trace-element compositions and U-Pb ages Bamforth et al., 2008; Flude and Narbonne, rial (pyroclastic vs. epiclastic of Fisher and comparable with those of source volcanics 2008; Hofmann et al., 2008; Bamforth and Nar- Schminke, 1984; Cas and Wright, 1987; or pri- on the nearby Burin and Bonavista Penin- bonne, 2009; Liu et al., 2011, 2012). These large mary volcaniclastic vs. sedimentary of White sulas and the islands of St. Pierre and quilted fossils remain evolutionary enigmas and Houghton, 2006). Furthermore, tuff and Miquelon. Loss of silica and alkalies in best assigned to the extinct group Vendobionta sediment geochemistry can be used to constrain some ashes indicates weathering on land, (Seilacher, 1992; Retallack, 2007; Brasier and paleotectonic setting (Bhatia, 1983; Bhatia and not marine diagenesis. Volcanic crystal and Antcliffe, 2009; Erwin et al., 2011). Were they Crook, 1986; Roser and Korsch, 1986; Gorton lapilli tuffs fail to show grading and have la- fungi (Peterson et al., 2003), lichens (Retallack, and Schandl, 2000; Ryan and Williams, 2007). pilli and highly vesicular scoria scattered in 2013a), xenophyophore foraminifera (Seilacher This is the fi rst geochemical and petrographic a fi ne-grained matrix, and so they were de- et al., 2005), sponges (Clapham et al., 2004; study of tuffs and sedimentary rocks of the Con- posited on land, not in water. These as well Sperling et al., 2011), sea pens (Jenkins, 1992), ception Group of Newfoundland. as block-and-ash fl ows, volcanic spindle or anemones (Gehling et al., 2000; Liu et al., A postulated forearc tectonic setting of the bombs, and degassing features are evidence 2010a, 2010b)? Did they live on land (Retal- Conception Group (Hughes and Brückner, of eruptions from nearby subaerial volcanic lack, 2013a), or were they marine organisms 1971; Nance et al., 1991; Barr and Kerr, 1997) edifi ces. (Hofmann et al., 2008; Bamforth and Narbonne, has stimulated volcanosedimentary models The fossiliferous Conception Group accu- 2009; Sperling et al., 2011)? Whether they were of marine burial of vendobiont fossils by non- mulated within a forearc basin, formed on marine or terrestrial organisms is fundamental to erosive volcanic ash (Jenkins, 1992; Seilacher, continental crust, inboard of the Holyrood understanding their biological affi nities, paleo- 1992, 1999). As a forearc sequence, other bed- horst, and uplifted as part of an ancient sub- ecology, and role in the Cambrian explosion of scale models are also worth consideration, duction complex or accreted terrane. Like life (Retallack, 2013a; Erwin et al., 2011). including contourites (Stow, 1979; Stow et al., analogous forearc basins in Oregon-Wash- This study is focused on volcanic tuffs and 1998), tempestites (Seilacher, 1982), seismites ington, southern Chile, and Japan, the Con- tuffaceous sedimentary rocks that host vendo- (Wheeler, 2002; Greb and Dever, 2002; Stewart ception Group includes not only marine bay bionts in order to understand more about their et al., 2002; Agnon et al., 2006), tsunamites turbidites, but also a variety of intertidal paleoenvironment. Preservation by tuff has (Atwater et al., 1992; Atwater and Hemphill- and terrestrial tsunamites, seismites, tem- been considered a distinctive “Conception-style Haley, 1997; Kelsey et al., 2005; Cisternas pestites, and paleosols. Traditional marine taphonomy” of these fossils (Narbonne, 1995), et al., 2005), ash-fall and ash-fl ow tuffs (Sparks turbidite models explain deposition of the which have holdfasts, tiering, and equidistant and Huang, 1980; Cas and Wright, 1987; Allen Mall Bay, lower Drook, and lower Briscal spacing indicating that they lived on the bed- and Cas, 1998), and paleosols (Retallack, 1997, Formations of the Conception Group, but ding planes where they are preserved (Clapham 2012a, 2013a). the Gaskiers, upper Drook, upper Briscal, and Narbonne, 2002; Clapham et al., 2003; Hof- Previous hypotheses of a deep-sea paleoenvi- and Mistaken Point Formations were depos- mann et al., 2008). Volcanic tuffs show a variety ronment for Newfoundland vendobionts have ited in coastal plains and intertidal zones. of features, depending on whether they were been based on interpretation of their substrates Paleoenvironments of vendobiont fossils erupted entirely on land or from, into, or within as turbidites (Anderson and Misra, 1968; Misra, preserved in life position in Newfoundland lakes or oceans (Table 1). Differences between 1971; Gardiner and Hiscott, 1988; Benus, were terrestrial to marginal marine, not volcanic environments can be related to the 1988; Clapham and Narbonne, 2002; Clapham deep sea. higher pressure, heat capacity, bulk density, and et al., 2003; Wood et al., 2003; Narbonne et al., viscosity of water compared with air (White 2005; Ichaso et al., 2007). However, turbidites †E-mail: [email protected]. et al., 2003). Much is known about subaerial may form in lakes, and at all depths of the

GSA Bulletin; May/June 2014; v. 126; no. 5/6; p. 619–638; doi: 10.1130/B30892.1; 12 fi gures; 2 tables; Data Repository item 2014091; published online 13 February 2014.

For permission to copy, contact [email protected] 619 © 2014 Geological Society of America Downloaded from gsabulletin.gsapubs.org on May 2, 2014 G.J. Retallack

geologically younger (Ediacaran-Devonian) GANDER ZONE TECTONIC BREAK 5 - to marine transgression AVALON ZONE 550–540 Ma non-marine, Signal Hill Group and Crown Hill Formation 560–550 Ma marine, St Johns Group BONAVISTA PENINSULA TECTONIC BREAK 4 - to arc-parallel tilting 590–560 Ma coastal-marine, Conception Group Bonavista Bay north 590–560 Ma subaerial volcanics and sediments of Marystown, Musgravetown, Long Harbour, Catalina St Pierre and Belle Rivière Groups 590–560 Ma Harbour Breton granite

EDIACARAN TECTONIC BREAK 3 - to new arc alignment localities 620–590 Ma marine Connecting Point Group fault 620–590 Ma subaerial volcanics of cross Harbour Main and Connaigre Bay Group section 620–590 Ma Holyrood Granite TECTONIC BREAK 2 - to continental arc N48° geologically older (Cryogenian, 670–760 Ma) Trinity Bay AVALON PENINSULA Ackley Granite stitching pluton

Conception

A Bay hns St Jo St GANDER Head Green ZONE Holyrood Horst

AVALON ZONE CONNAIGRE PENINSULA Salmonier B

Fortune Bay + Cambrian stratotype + + N47° Miquelon Placentia Bay

y

St Pierre BURIN PENINSULA Portugal Cove South 0204060 km St Marys Ba Pigeon Cove St Shotts Mistaken Point E56° E54° Bristy Cove

CROSS SECTION AVALON PENINSULA A east B

Holyrood Horst Trinity Bay Synclinorium Conception Bay Anticlinorium Bulls Bay Syncline

Figure 1. Simplifi ed geological map and study sites in the Avalon zone of Newfoundland (after King, 1988; Dec et al., 1992; O’Brien et al., 1996, 2006; O’Brien and King, 2002, 2005; Pisarevsky et al., 2012). ocean (Bouma, 1962; Ludlam, 1974; Talling 1971; Benus, 1988; Dalrymple et al., 1999). These suggestions of varied paleoenvironments et al., 2012). Turbidites have been generated Geochemical indices for the Mistaken Point are here tested with an array of new fi eld, geo- in fl umes as shallow as 0.5 m (Sumner et al., and Gaskiers Formations of the Conception chemical, and petrographic observations. 2009). Previous indications of shallow-marine Group, such as freshwater C/S ratios >2.8 and paleoenvironments for the Conception Group soil ratios <0.2 of highly reactive iron over MATERIALS AND METHODS include frondose shapes and spreading orienta- total iron (Retallack, 2013b), are also incon- tions of vendobionts like those of modern algae sistent with a deep-marine setting. Detrital gar- Measured sections (Fig. 3) of the Mistaken or marine invertebrates with photosymbionts nets in the Gaskiers Formation are evidence of Point Formation were made at four localities in the photic zone (Fischer, 1965; Seilacher, nearby continental, peraluminous, high-grade (Fig. 1): (1) through the famous fossil bed E at 1984, 1989; McMenamin, 1986). Also taken metamorphic source terrains (Gravenor, 1980). Mistaken Point on the southern Avalon Penin- for shallow-marine indicators were hummocky Finally, terrestrial glacial deposits and paleosols sula (Narbonne et al., 2005); (2) in the core of cross-stratifi cation, oscillation ripples, car- have been identifi ed in the Gaskiers Formation an anticline on the rock platform 2 km west of bonate nodules, and purple-red color (Misra, of the Conception Group (Retallack, 2013b). St. Shotts, southern Avalon Peninsula; (3) from

620 Geological Society of America Bulletin, May/June 2014 Downloaded from gsabulletin.gsapubs.org on May 2, 2014 Newfoundland Ediacaran

Narbonne This paper west of Pigeon Cove and east of Portugal Cove Cape Ballard Fm braided stream braided stream South; Briscal Formation on the western cliffs delta plain km Ferryland Head Fm braided stream alluvial soils of Bristy Cove; and Trepassey Formation on 7 Gibbett Hill delta plain braided stream the rock platform west of Portugal Cove South Formation VENDOBIONTA PALEO- alluvial soils (selected taxa) CURRENTS braided stream (King, 1988). Exact global positioning system delta plain Cappahayden Formation GR. HILL SIGNAL alluvial soils (GPS) positions can be provided on request but 6 Renews Head Formation prodelta delta plain are sensitive because these localities are pro- marine bay tected by Newfoundland and Labrador regula- delta front intertidal soils tion 67/11 of the Historic Resources Act (O.C. marine bay Fermeuse intertidal soils 2011-198).

pp. 5 Formation s Oriented rock specimens for analysis are continental marine bay slope from stratigraphic sections measured using ST JOHNS GROUP JOHNS ST level and tape (Fig. 3). Petrographic thin sec- intertidal soils Trepassey Formation prodelta tions were point counted for grain-size frac- 4 Mistaken Point supratidal and 565.0 Ma Formation abyssal plain intertidal soils, tions and mineral content (Data Repository Palaeopascichnus coastal lagoon Tables R1 and R21) with error of ±2% (Mur- Briscal submarine phy, 1983). Bulk density was determined by the 3 Formation fan marine bay clod method using paraffi n (Retallack, 1997). ofusus spp Consumable specimens (R3925–R4079) are 578.8 Ma Fract continental slope intertidal soils curated within the Condon Collection of the Museum of Natural and Cultural History of 2 Drook Bradgatia linfordensis submarine the University of Oregon, Eugene (G.J. Retal- Formation marine bay fan lack, director), and archival polished slabs (G149–G176) are deposited in collections of

Trepassia wardae Trepassia 582.4 Ma Ivesheadia lobata

Charniodiscus spp 1 583.7 Ma Gaskiers GROUP CONCEPTION moraine and The Rooms (provincial museum), St. John’s Formation Aspidella terranovica submarine till coastal soils Thectardis avalonensis estuarine (N. Djan-Chekar, curator). Mall Bay submarine Specimens were also analyzed for major ele- Formation fan and abyssal plain marine bay ments by X-ray fl uorescence of lithium-borate– 0 620.5 Ma

Holyrood Granite Charnia spp and fl uxed glass discs, for organic carbon using a and Harbour Main Leco combustion infrared analyzer, and for fer- Volcanics red color rous iron using Pratt titration by ALS Chemex ripple-mark current direction silt clay trough cross bedding sand of Vancouver, British Columbia, Canada (Data shale gravel general paleocurrent planar cross bedding Repository Table R3 [see footnote 1]). Selected volcanic sandstone ripple marks fossil frond felling direction tuffs were analyzed for both major and trace tillite granitic planar bedding elements using inductively coupled plasma– mass spectroscopy by ALS Chemex, of North Figure 2. Ediacaran geological succession of Newfoundland with revised radiometric ages Vancouver, Canada (Data Repository Table R4 (after Van Kranendonk et al., 2008), ranges of selected fossils (after Narbonne et al., 2005; [see footnote 1]). These data were corrected to a Liu et al., 2012), paleocurrents of frond fossils (gray) and ripple marks (black current roses volatile-free basis for use in discrimination dia- and white arrows), and alternative paleoenvironmental interpretations of Narbonne (1995) grams for tectonic setting and magmatic series and Narbonne et al. (2005), and this paper. (Winchester and Floyd, 1977; Bhatia, 1983; Le Bas et al., 1986; Bhatia and Crook, 1986; Roser the northernmost point south along the eastern were made in the shore platform and littoral and Korsch, 1986; Gorton and Schandl, 2000). shore of Murphys Cove, near Port Union and talus of Goodland Point, near Catalina on the Short descriptions (and archived rock speci- Catalina on the northeastern Bonavista Penin- Bonavista Peninsula (Hofmann et al., 2008) mens) for each of the studied tuffs are listed sula (Hofmann et al., 2008); and (4) through and in isolated blocks of purple-red beds of the 1 fossiliferous surfaces on the north side of Green Mistaken Point Formation in Salmonier Nature GSA Data Repository item 2014091, petro- graphic and geochemical data for the Ediacaran Head, near Spaniards Bay, northeastern Avalon Park (King, 1988), in the interior Avalon Penin- Conception Group, Newfoundland, is available at Peninsula (Narbonne et al., 2009). Additional sula. Other measured sections were made of the http:// www .geosociety.org /pubs /ft2014 .htm or by observations of the Mistaken Point Formation Drook Formation at the tuff and fossil locality request to editing@geosociety .org.

TABLE 1. FEATURES OF LAND, SHALLOW-, AND DEEP-WATER PYROCLASTIC ROCKS Subaerial eruption onto land Subaerial eruption into water Shallow (>1 km) subaqueous eruption Deep (>1 km) subaqueous eruption Spindle, ribbon bombs Spindle, ribbon bombs Hyaloclastite breccia Silicic spatter and glass ecimupdnaetiluciteR ecimuP ecimupdetnemgarf-hcneuQ ecimupdetnemgarf-hcneuQ easyhpohtildeniartS ffutdedarg-evissaM itilreP serutcarfc serutcarfcitilreP ffutdedargnU ffutdedarG ffutdedarG ffutdedarG Block-and-ash fl ow Tuff turbidites Fine-ash–rich ignimbrite Fine-ash–poor ignimbrite Blocky silicic peperite Blocky silicic peperite Blocky silicic peperite Globular silicic peperite Welded ash-fl ow tuff Welded ash-fl ow tuff Welded ash-fl ow tuff Fluidal silicic lava fl ows Note: From Fisher and Schminke (1984), Cas and Wright (1987), White et al. (2003), and Busby (2005).

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A. Catalina B. Mistaken Point C. St Shotts (R4001), 1 cm thick, from the Mistaken Point m. m. m. Formation (4.9 m in Fig. 3B); and (5) graded, light-gray lithic tuff (R4032), 3 cm thick, from t the Briscal Formation at Bristy Cove. v a

a R4024-30 5 50 GEOLOGICAL SETTING

R4046-53 60 R4023 v v a The Conception Group of the Avalon zone a 0 (Fig. 1) consists of 4.2 km of sedimentary 45 rocks, tuffs, and rare basaltic lavas (King, a a 1988; Myrow, 1995), deposited on a base- D. Green Head ment of Holyrood Granite and Harbour Main m. 4 Volcanics (Fig. 2). Conglomerate and tillite of a a v the Conception Group include clasts of gran- v 50 a 2 ite, diorite, granophyre, basalt, basaltic scoria, S-J R4075-9 chert, sandstone, siltstone, and shale derived a S-I 0 from uplands of continental crust (Williams and King, 1979; Carto and Eyles, 2011; Retal- claysilt 35 sand v gravel lack, 2013b).

Ages of Neoproterozoic volcanic rocks 211 R4 KEY a of Newfoundland using the U-Pb method 40 volcanic tuff (Table 2) fall within fi ve distinct groups sepa- a 30 sandstone rated by hiatuses (Krogh et al., 1988; S.J. a S-H O’Brien et al., 1989, 1992, 1994, 1995, 1996, siltstone, claystone 2001, 2006; O’Brien and King, 2002, 2005; Figure 3. Measured sections red claystone breccia Valverde-Vaquero et al., 2006; Van Kranen- of Mistaken Point Formation, grey claystone donk et al., 2008; Skipton et al., 2013). These Newfoundland. 25 breccia volcanic lapilli age groups have been interpreted as successive a a basaltic scoria bomb tectonic stages: (1) an island arc (Burin Group) v 30 a on oceanic crust (Murphy et al., 2008) by early volcanic spindle bomb Cryogenian (770–760 Ma); (2) a volcanic arc 20 a gray color (Cinq-Nerf Gneiss) on intermediate crust by red color a late Cryogenian (680–670 Ma), (3) a separate a brown stained layers v a volcanic arc (Harbour Main, lower Marys- S-G pyrite nodules v town, Love Cove, Connaigre Bay, and Belle v planar bedding Rivière Groups) on continental crust (Nance a flaser bedding 20 v hummocky cross et al., 1991; Barr and Kerr, 1997; Pouclet et al.,

2007) by early Ediacaran (640–600 Ma), (4) a 11-23 R40 stratification aa trough cross bedding geographically extensive bimodal continen- ripple marks tal volcanic arc (Musgravetown and St. Pierre 10 S-F scour-and-fill R3935-53 Groups, and Manuels Volcanics) by mid-Edia- slump bedding caran (590–560 Ma), and (5) arc-parallel tec- a clastic dykes S-E tonic tilting of the forearc (upper Marystown a a discoid fossils R39230-4 Group) to give southerly paleocurrents (Ichaso S-D (Aspidella, Heimalora) 10 et al., 2007; Mason et al., 2013) by the late 5 frond fossils a a v (Fractifusus, Ediacaran (560–550 Ma). Four high-precision Charniodiscus) zircon U-Pb dates within the Conception Group

R3925-9 tilting traces (trails? (Table 2) form a linear regression against strati- a R4002-10 t of Lui et al., 2010a,b) graphic level and so are evidence against large S-E fossil surfaces hiatuses within the Conception Group (Retal- R4209 named by lack, 2013b).

R3886-4001 Benus (1988) The great thickness of sedimentary rocks and tectonic deformation resulted in Cam- brian (ca. 525 Ma) regional metamorphism to here: (1) ungraded, light-green, lithic tuff, Mistaken Point Formation near Catalina (6.1 m prehnite-pumpellyite facies (Papezik, 1974). 30 cm thick, with basal pipe structures (R3980– in Fig. 3A); (3) ungraded purple-gray dust tuff, The upper Conception Group in the Bonavista R3983) from the Drook Formation at Pigeon 40 cm thick, with scattered euhedral sanidine and southern Avalon Peninsulas escaped Cove; (2) ungraded purple-gray dust tuff, 5 cm crystals (R3946–R3947) from the Mistaken this degree of metamorphism, as revealed by thick, with scattered highly vesicular scoria and Point Formation near Catalina (9.6 m in Fig. locally abundant laumontitization of volcanic accretionary lapilli (R3930–R3934) from the 3A); (4) ungraded dark-greenish-gray dust tuff tuffs (Data Repository Table R2 [see foot-

622 Geological Society of America Bulletin, May/June 2014 Downloaded from gsabulletin.gsapubs.org on May 2, 2014 Newfoundland Ediacaran

TABLE 2. U-Pb ZIRCON AGES OF PROTEROZOIC ROCKS OF AVALONIAN NEWFOUNDLAND )aM(egA kcoR ecnerefeR 7–/2+845 enozrednaG,ekidetiroiD )6002(.lateoreuqaV-edrevlaV 2±255 aMreppufoscinacloV puorGnwotsyr )5991(woryM 5–/41+755 enoZrednaG,knabdnaSfoorbbaG )6002(.lateoreuqaV-edrevlaV TECTONIC BREAK 4—to arc-parallel forearc basin tilting 3±565 puorGnoitpecnoC,noitamroFtnioPnekatsiMfoffuT )8891(suneB 5±865 puorGruobraHgnoL,noitamroFyaBelleBfoscinacloV )5991(.lateneirB’O 570 +5/–3 Rhyolite of Rocky Harbour Formation, Musgravetown Group O’Brien et al. (1989) 572 ± 13 Ignimbrite of Anse de Gouvernement Formation, Belle Rivière Group Rabu et al. (1996) 3.2±4.875 xelpmocevoCesroHfoekidetisednA )3102(.latenotpikS 578.8 ± 0.5 Rhyolitic tuff of Pigeon Cove, Drook Formation, Conception Group Van Kranendonk et al. (2008) 0.2±6.085 esroHfoyryhproprapsdleF xelpmocevoC )3102(.latenotpikS 21±185 dnalsIerreiP.tS,etirbmingiuaepahC )6991(.lateubaR 91±185 puorGerreiP.tS,noitamroFeguoRpaCfoetiloyhR )6991(.lateubaR 9.1±7.185 xelpmocevoCesroHfoekidcitiloyhR )3102(.latenotpikS 5.0±4.285 puorGnoitpecnoC,noitamroFkoorDlasabfoffuT )8002(.lateknodnenarKnaV 5.0±7.385 puorGnoitpecnoC,noitamroFsreiksaGelddimfoffuT aV )8002(.lateknodnenarKn 584 ± 2 Ash-fl puorGniaMruobraH,scinacloVsleunaMfoffutwo )1002(.lateneirB’O 6–/7+485 yaBatsivanoB,daeHrevoDtsaEfoetiroidonarG )6002(.lateoreuqaV-edrevlaV 4.2–/4.3+9.585 puorGniaMruobraH,ekidetiloyhR hgorK )8891(.late TECTONIC BREAK 3—to new arc and forearc alignment 608 +20/–7 Ash-fl puorGnwotsyraMrewolfoffutwo )8891(.latehgorK 606 +3.7/–2.9 Ash-fl puorGniaMruobraHfoffutwo latehgorK )8891(. 026–016 puorGtnioPgnitcennoCfosffuT )2991(.lateneirB’O 41±516 nalsInoleuqiM,etimejhdnortcnalBpaC d )6991(.lateubaR 8.1–/1.2+5.026 puorGniaMruobraHgnidurtnietinarGdooryloH )8891(.latehgorK 1±026 yaBatsivanoB,puorGevoCevoLfoscinacloV )2991(.lateceD 3±126 tnisevisurtnikoorBsnommiS puorGyaBergiannoCo )4991(.lateneirB’O 4–/5+126 puorGniaMruobraHfoffutcisleF )1002(.lateneirB’O 0.2–/3.2+6.226 puorGniaMruobraHfoetiloyhrdednab-wolF )8891(.latehgorK 7.1–/9.1+326 puorGruobraHkcoRfoetaremolgnocnistsalcetiloyhR )8891(.latehgorK 4.1±526 xelpmocevoCesroHfoetiroidonarG )3102(.latenotpikS 3±626 yaBergiannoCfoscinacloV puorG )2991(.lateneirB’O 2±236 puorGniaMruobraHfogulpetiloyhrcitiryhproP )8891(.latehgorK 640 ± 2 Monzonite (near Woodfords) intrusion of Harbour Main Group O’Brien et al. (2001) TECTONIC BREAK 2—to continental volcanic arc 3±376 alusninePergiannoC,sevisurtnievoCs’ybruF teneirB’O )2991(.la 11–/21+576 enozrednaG,ssienGfreN-qniC )6002(.lateoreuqaV-edrevlaV 3±186 alusninePergiannoC,noitamroFtnioPelkciT )2991(.lateneirB’O TECTONIC BREAK 1—to oceanic volcanic arc 6.1–/2.2+367 iruB,htrowsdnaWtaorbbagetitamgeP puorGn )8891(.latehgorK 1.2±5.467 puorGniruB,htrowpEtaorbbaG )6002(.lateoreuqaV-edrevlaV note 1]). Laumontite has been observed as a NEW OBSERVATIONS deforms the basal dark part and protrudes from precipitate of hydrothermal springs (Barnes the top to be onlapped by laminae above the ash et al., 1978; McCulloh et al., 1981), but authi- The following paragraphs outline a variety bed, like a volcanic bomb. genic laumontite in the Mistaken Point and of new observations revealing complexity Drook Formation is strata concordant, and not in volcanosedimentary rocks of the Concep- Intraformational Clasts vein fi lling. The laumontite zone of zeolite- tion Group. facies metamorphism (0–3.3 kbar fl uid pres- Several horizons of intraformational breccia sure, 110–330 °C) is transitional to the higher- Volcanic Clasts at St. Shotts (Fig. 4B), and high in the section at grade prehnite-pumpellyite metamorphic zone Mistaken Point (Fig. 5E), are ungraded in grain (Liou, 1971). Both metamorphic facies are One 2.3-m-thick bed in the Mistaken Point size. The horizons at St. Shotts are 55–78 cm well known in New Zealand (Coombs, 1954; Formation near Catalina has blocks of scoria- thick and contain tabular clasts of siltstone up Boles and Coombs, 1977), where the laumon- ceous basalt up to 30 cm long suspended in a to 78 cm long that are chaotically distributed. tite facies is found at burial depths of 5–9 km, matrix of fi ne tuff, like a block-and-ash fl ow The host units maintain a constant thickness lat- comparable with likely burial depth of the Mis- (Fig. 4A). Most of the blocks with long axis erally for at least 30 m in a sea-cliff exposure. taken Point Formation (Fig. 2). nearly concordant to bedding are scoria, with The breccia beds at Mistaken Point have equant Paleomagnetic directions of hematite and fl uidal chilled margins extended to a wisp (Fig. clasts that are not chaotically arrayed but are magnetite in the Conception Group have been 4D). Comparable blocks up to 5 cm long were more or less fi tted, as if brecciated in place. reset by metamorphism (Gravenor et al., 1982; also seen in the Mistaken Point section (Fig. Evans and Raub, 2011). Paleomagnetic direc- 3B). Similar scoria blocks are also common in Pipe Structures tions of Marystown and Musgravetown Vol- the Gaskiers Formation at St. Mary, Newfound- canics of the same geological age (Table 2) were land (Retallack, 2013b). The distinctive 30-cm-thick ash in the Drook less severely affected and have been taken as A clast of basaltic andesite, 11 cm long, at Formation at Pigeon Cove (Fig. 5D) is ungraded evidence of midlatitude locations (34.6 ± 8.0°S, Catalina is notable for its spindle shape and in grain size and composition, but it has a 3 cm 23.6 ± 8.3°S, 19.1 ± 11.1°S, and 24.5 ± 11.9°S orientation at a high angle to the enclosing basal zone darkened by admixture of underly- successively between 570 and 550 Ma: Thomp- ungraded felsic tuff (Fig. 4C). It does not reach ing gray siltstone (Fig. 6G). The light-green son et al., 2012; Pisarevsky et al., 2012). through to the bottom of the ash bed, but it ash above this darkened base has sinuous,

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A B

C D

E F G

Figure 4. Field photographs of sedimentary and volcanic structures: (A) block-and-ash fl ow at 33.7 m, Catalina; (B) seismite brecciated zone, at 6.2 m, St. Shotts; (C) volcanic spindle bomb across white tuff, at 3.3 m, Murphys Cove; (D) scoria bomb, at 9.5 m, Murphys Cove; (E) bimodal-direction ripple drift cross-stratifi cation, 53.5 m at Mistaken Point; (F), hummocky cross-stratifi cation, 8.6 m at Catalina; (G) purple rip-up clasts in green-gray sandstone, at 54.3 m, Mistaken Point. Hammer handles are 25 cm long.

624 Geological Society of America Bulletin, May/June 2014 Downloaded from gsabulletin.gsapubs.org on May 2, 2014 Newfoundland Ediacaran

A C

B

D E

Figure 5. Field photographs of beds: (A–C) tsunamites (sharp tops and bottoms indicated by arrows) covering red- green mottled beds at 51.3 m, 7.3 m, and 22.5 m, respectively, Mistaken Point; (D) white volcanic ash bed on sulfi dic intertidal paleosol in Drook Formation at Pigeon Cove; (E) tempestite sandstone on seismite breccia, at 63.6 m, Mis- taken Point. Hammer handles are 25 cm long. Arrows indicate sharp sedimentary contacts.

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A B C D R4024 R3945

R3930

R4025 R3931

R3946

R3932

R3933

R4026 R3947

1 cm R3934 G R3982 1 cm

H R4031

R4027

1 cm 1 cm R4032 E F

R4033

R3983 1 cm 1 cm 1 cm 1 cm

Figure 6. Polished slabs of beds: (A) graded lithic-pumice tuff and varves in the Oligocene (30 Ma) Mehama Formation in road cut near Goshen, Oregon, U.S.A. (Retallack et al., 2004; McClaughry et al., 2010); (B) siltstone and sandstone of Briscal Formation at Bristy Cove; (C) slump bedding and fl ame structures in tuffaceous sandstone above scattered sanidine crystals in a paleosol at 9.6 m, Catalina; (D) lapilli tuff on paleosol at 8 m, Catalina; (E) volcanic tuff within red siltstone at 2.5 m, Mistaken Point; (F) red claystone clast, at 54.3 m, Mistaken Point; (G) sinuous pipe vesicle in base of tuff of Drook Formation at Pigeon Cove; (H) volcanic ash of Briscal Formation at Bristy Cove. Specimen A is R4163A in the Museum of Natural and Cultural History, University of Oregon, Eugene. Specimen numbers in The Rooms, St. Johns, are NFM G-171 (B), NFM G-153 (C), NFM G-151 and G152 (D), NFM G-165 (E), NFM G-168 (F), NFM G-156 (G), NFM G-170 (H).

626 Geological Society of America Bulletin, May/June 2014 Downloaded from gsabulletin.gsapubs.org on May 2, 2014 Newfoundland Ediacaran near-vertical tubules, 5–7 mm in diameter, as if concentrated along the basal contact, nor are they 1999; Clapham and Narbonne, 2002; Clapham injected upward by escaping fl uids and dark silt- aggregated with grains of similar size, but instead et al., 2003). Tool marks and fl ute casts are con- stone (Fig. 6G). The margins and rounded ends they are scattered in sandy or silty matrix. A fi ne- spicuous by their rarity in the Conception Group of the tubules are opaque with iron-manganese grained tuff from Catalina has euhedral sanidine (Seilacher, 1992, 1999). My fi eld work found no stain (Fig. 7D). The fi ll of the tube does not con- crystals scattered in the matrix (Figs. 6C and basal scour features. tain crystals and is not laumontitized like the 7A). A lapilli tuff from Catalina is remarkable My observations of putative “trails” of Liu rest of this ash bed (Fig. 8F). in showing unsorted crystals, rounded lapilli, et al. (2010a) confi rmed they were a kind of tool and cross sections of scoria (Figs. 6D and 7C). mark called a tilting trace (Wetzel, 1999). These Accretionary Lapilli A 30-cm-thick volcanic ash from the Drook For- distinctive structures have grooves with very mation at Pigeon Cove shows no grain size or marked crescentic cross ridges and lateral ridges Several beds at Catalina have conspicuous compositional grading (Figs. 6G and 8F). These as a hard object bounced up ripple marks (Liu spherical grains suspended in a silty matrix are quite different from Ediacaran (Fig. 6H) or et al., 2010a; Retallack, 2010), but smooth where (Fig. 6D). In thin section, these grains have been Oligocene (Fig. 6A) graded beds. the object slid down the other side into troughs replaced in part by radial laumontite crystals fi lled with dark heavy minerals. Liu et al. (2010b) (Fig. 7C), presumably due to Cambrian zeolite- Silt and Feldspar argued against a tilting trace explanation, because facies metamorphism (Papezik, 1974) of a fi ne- the structures cross one another, meander, and grained tuffaceous precursor. The replacement A distinctive petrographic feature of the Con- coil on themselves, but crossing, meandering, and has disrupted rims and also concentric banding ception Group is dominance of feldspar and silt coiling are characteristic of tilting trails of algal within the grains. This dark-light banding does (Retallack, 2013b). Feldspar is twice as abun- holdfasts or leaves drifting with wind and eddies not surround a central nucleating grain, although dant as quartz in point counts for mineral com- of shallow water (Sainsbury, 1956; Jones, 2006). some silt-size feldspar grains are incorporated position, and most grain-size counts are over within these accretionary lapilli (Fig. 7C). half silt (Fig. 8). This paucity of clay is not due Soft-Sediment Deformation to metamorphism of clay to silt-size illite and Bed Grading chlorite: The abundant silt-size grains are not Convolute lamination in the Mistaken Point phyllosilicates. Clay is rare, but volcanic shards Formation (Fig. 6C) was described by Misra The Mistaken Point Formation is well exposed were not seen, not even the usual devitrifi ed and (1971, their fi g. 7D) as “pseudonodules,” by in coastal outcrops (Figs. 4A–4C), but in order replaced shard forms of vitric tuffs (Coombs, Benus (1988, their fi g. 11A) as “convolute lami- to see fi ne details of grain size, observations 1954; Retallack et al., 2000, 2004). nation,” and by Wood et al. (2003) as “slump- were also made on polished slabs of entire beds ing.” Convolute lamination occurs within sandy Ripple Marks and Hummocks (Fig. 6) and in petrographic thin sections (Fig. 7). beds (Fig. 8C) and does not form at the contact Surprisingly, no examples of beds graded from Ripple marks are common in the Concep- of sand and shale. At one level at Mistaken conglomerate or sand to clay were found in the tion Group, including ripple-drift cross lamina- Point (62.6 m in Fig. 3B), sandstone fi lls wide Mistaken Point Formation, although such graded tion with current directions apparently opposed, fractures down into brecciated clayey siltstone. beds were found in the Mall Bay, lower Drook, though visible in only one plane (Fig. 4E). A Deformation at sand-on-clay contacts was lower Briscal, and Trepassey Formation (Retal- clear co-set of hummocky cross-stratifi cation brittle , not plastic (Fig. 5E). lack, 2013b). In contrast, excellent grain-size was found in a three-dimensional outcrop reveal- grading is shown in polished slabs of the pre- ing domes as well as mounded bedding near Nodules sumed marine Ediacaran Briscal Formation of Catalina (Fig. 4F). Three-dimensional exposure Newfoundland (Fig. 6H) and pumice-lithic vol- is important because it shows that hummocks are Some thick tuffaceous beds have extensive canic ash from the lacustrine, Oligocene (30 Ma) offset from one set of the co-set to another, unlike replacive metamorphic laumontite and convo- Mehama Formation, near Goshen, Oregon the controversial tectonic kink bands at Mistaken lute lamination (Fig. 8C) that weather out as (Fig. 6A; Retallack et al., 2004; McGlaughry Point illustrated by Williams and King (1979, large nodule-like mounds. These may have been et al., 2010). their fi g. 13) as “asymmetrical wave ripples” the nodules of Benus (1988), because laumon- Sandy beds of the central red portion of the (in errata labeled “sinuous vertical fractures”). tite crystals have a color somewhat like carbon- Mistaken Point Formation differ from graded A tectonic kink band explanation is favored ate in thin section, but they lack the cleavage and beds in having a sharp boundary between sand- here because their wavelength corresponds with relief of carbonate (Fig. 7C). Calcareous nod- stone and siltstone, with no bleed-through of spacing of fracture concentrations seen in cliff ules of Benus (1988, their fi g. 11A) were not sand grains above the contact (Figs. 5A–5C and exposures of these surfaces. These undulations found during measurement of the same section 6E). These silty to sandy beds with sharp upper may have been the “oscillation ripples” noted for this study (Fig. 3B). Extensive application of and lower boundaries overlie many of the fossil- by Benus (1988), and the “hummocky cross- dilute hydrochloric acid in the fi eld and exami- iferous surfaces at Mistaken Point (Figs. 5A–5C) stratifi cation” reported in abstract by Dalrymple nation of thin sections during this study failed to and have been regarded as “tuffs” (by Jenkins, et al. (1999), but not in subsequent publications fi nd any carbonate. 1992; Seilacher, 1992, 1999; Narbonne, 1995), (Wood et al., 2003; Ichaso et al., 2007). but no volcanic shards or crystals were seen VOLCANOLOGICAL in slabs (Fig. 6E), nor in thin sections of them Tool Marks INTERPRETATIONS (Fig. 7B). Comparable sharp tops to basal sandy layers were also illustrated by Wood et al. (2003, Most bedding planes below sandstone beds Paleoenvironments of the Mistaken Point their fi g. 6) and Ichaso et al. (2007, their fi g. 4). were stabilized by vendobiont fossils and their Formation can be constrained by interpretations Where large clasts, lapilli, or crystals are pres- associated microbial mats, which remained of the chemical composition, as well as inferred ent in the Mistaken Point Formation, they are not little damaged by scouring (Seilacher, 1992, emplacement mechanisms of its volcanic tuffs.

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A B

5 mm 5 mm

C D

5 mm 5 mm

Figure 7. Petrographic thin sections of tuffs: (A) sanidine tuff in A horizon of Catalina paleosol at 9.6 m, Murphys Cove; (B) ungraded dust tuff at 9.8 m, Mistaken Point; (C) laumontitized accretionary lapilli tuff with scattered high vesicular scoria at 8 m, Murphys Cove; (D) sinuous pipe vesicle in tuff of Drook Formation at Pigeon Cove. All images are in plane light, scanned from slides cut vertical to bedding and oriented with upper side to top. Sample numbers in Museum of Natural and Cultural History of the University of Oregon are R3941 (A), R4006 (B), R3932 (C), and R3982 (D).

628 Geological Society of America Bulletin, May/June 2014 Downloaded from gsabulletin.gsapubs.org on May 2, 2014 Newfoundland Ediacaran

A Mistaken Point (0–1.3 m) Bhatia and Crook (1986) gave weak discrimi- WEST EAST nation. However, silica versus potash/soda 0 ratios of Roser and Korsch (1986) showed a very clear partition of both tuffs and sedimen- tary rocks into the active continental-margin and passive-margin fi eld (Fig. 10B), perhaps because silica and potash depletion were linked 1 (again as for paleosols of the Gaskiers Forma- tion: Retallack, 2013b). Loss of silica and alka-

B Mistaken Point (63.8–64.1 m) Percent composition rock specimens lies is a geochemical signature of weathering cm dark greenish gray (5BG4/1) 4024 on land (Retallack, 1997), and the reverse of 0 greenish gray (5BG5/1) hydrothermal alteration (Abrams et al., 1977) dark greenish gray (5BG4/1) 30 greenish gray (5BG5/1) 4030 and marine diagenesis (Boles and Franks, C Mistaken Point (22.2–23.3 m) 1979; Bjørlykke, 1998). cm dark reddish gray (5R4/1) 4011 4012 Trace elements provide clear discrimination 4013 bluish gray (5B6/1) of active continental-margin and intraplate vol- 4014 canics from the lanthanum versus thorium plot silt dark bluish gray (5B4/1) 4015 (Fig. 10A) of Bhatia (1983) and the thorium/ 4016 bluish gray (5B6/1) tantalum versus ytterbium plot (Fig. 10B) of 4017 dark bluish gray (5B4/1) sand 4018 Gorton and Schandl (2000). These elements 0 clay Figure 8. (A) Field sketch of dark reddish gray (5R4/1) are relatively immobile during metamorphism 4023 paleosol erosion at 0–1.5 m D Mistaken Point (0–1.3 m) feldspar quartz (Winchester and Floyd, 1977). cm 3986 Trace elements also reveal a close match (Fig. 3), Mistaken Point. (B–F) 0 greenish gray (5GY7/1) Grain size and minerals (from dark reddish gray (5R4/1) between 575 and 565 Ma tuffs of the Conception dark greenish gray (5G4/1) point counting) of paleo sols, light greenish gray (5GY7/1) Group (Fig. 11A) and tuffs of the 570–590 Ma St. Pierre and Belle Rivière Groups of the islands tuffs, and tempestites of the Con- 50 dark reddish gray (5R4/1) clay silt 3996 ception Group of Newfoundland. 3997 of St. Pierre and Miquelon (Rabu et al., 1996). 3998 light greenish gray (5GY7/1) One difference is depletion of phos phorus in 3999 100 the Conception Group tuffs, again a feature of 4000 dark reddish gray (5R4/1) 4001 Conception Group paleosols as opposed to fresh E Catalina (9.2–10.3 m) rock fragments mica tuffs (Retallack, 2013b). Plutonic suites ranging cm bluish gray (5B6/1) 3935 0 bluish gray (5B5/1) in age from 570 to 550 Ma in Avalonian terranes weak red (10R4/2) of Newfoundland, New Brunswick, and Nova bluish gray (5B6/1) bluish gray (5B5/1) Scotia represent a continental-margin calc-alka- dark reddish gray (5R4/1) silt 50 reddish gray (5R5/1) line volcanic arc (O’Brien et al., 1996; Barr and dark reddish gray (5R4/1) Kerr, 1997). 3949

sanidine greenish gray (5BG5/1) 3950 Rare earth elements (REE) of Conception 100 greenish gray (5BG5/1) 3951 Group tuffs normalized to mantle values of Sun bluish gray (5B5/1) 3953 and McDonough (1989) show patterns of light F Pigeon Cove cm mica opaque rare earth enrichment and a modest europium greenish gray (5G5/1) anomaly (Fig. 11B), comparable with the 578– very dark gray (5Y3/1) 3978 greenish gray (5G5/1) 582 Ma Horse Cove complex of Newfoundland

light greenish gray (5GY7/1) 3983 (Skipton et al., 2013). Similar REE patterns are 0 3984 also seen in Proterozoic shales (Schieber, 1990), yellowish red (5YR5/6) rind clay 3985 soil developed on till (Öhlander et al., 1996) 20 greenish gray (5G5/1) gravel laumontite accretionary lapilli tuff 8.1 m Catalina 3932 and granite (Aubert et al., 2001), and hydro- dust tuff 4.9 m Mistaken Point 4002 thermally altered igneous rocks (Hopf, 1991). Oceanic-island arcs in contrast have fl atter REE patterns without marked anomalies (Taylor and McLennan, 2009; Skipton et al., 2013). Tectonic Setting chester and Floyd (1977). More mafi c compo- sitions in the classic alkali-silica diagram (Fig. Eruptive Style Bulk chemical compositions of sedimentary 9A) of Le Bas et al. (1986) may refl ect desili- rocks and tuffs in the Mistaken Point, Briscal, cation during ancient soil formation (as found Seilacher (1992) envisaged preservation of and Drook Formations support previous inter- in Gaskiers Formation by Retallack 2013b), fossils at Mistaken Point by gentle, nonerosive, pretations of a calc-alkaline volcanic arc source because there is little evidence in these exten- submarine grain fl ows of volcanic ash, presum- that was continental rather than oceanic (Nance sive coastal exposures of modern weathering ably remobilized after eruptions (epiclastic-sedi- et al., 1991; Barr and Kerr, 1997). The tuffs or hydrothermal alteration. Silica mobility may mentary). However, Jenkins (1992) proposed are primarily dacitic, as revealed by the stable also be the explanation why the alumina/silica that the fossils were covered by gas-buoyed vol- trace-element composition (Fig. 9B) of Win- versus iron and magnesium plot (Fig. 10D) of canic ash fallout from submarine phreatomag-

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14 Phonolite A tuff at Catalina has rounded, concentri- A cally zoned grains comparable with accretion- 12 Tephri- ary lapilli, which are scattered within a fi ne- phonolite Trachyte grained matrix (Figs. 6D and 7C). The rounded 10 outline of some of these spherical grains is Phono- Foidite Trachy- disrupted by partial metamorphic replacement tephrite Trachy- Basaltic andesite by laumontite. Accretionary lapilli, also known 8 dacite Rhyolite as “volcanic hail,” form in subaerial eruptive Basanite andesite trachy- O (weight %) Tephrite columns of Plinian style (Reimer, 1983) and

2 6 Trachy- have been regarded as evidence for subaerial basalt exposure when found in deep-sea cores (Thor-

O + K

2 darson, 2004). With exception of carbonatite 4 Dacite

Na Basalt lapilli (Le Bas, 1977), which are ruled out for Andesite

Basaltic andesite Newfoundland by modest slopes in REE pat- 2 terns (Fig. 11), accretionary lapilli fall apart in

Picro- basalt water (Reimer, 1983). If lapilli remained intact 0 while falling through water, one would expect 30 40 50 60 70 80 90 them to be sorted into layers of similar size like SiO2 (weight %) Oligocene lapilli tuffs (Fig. 6A), not scattered 1 in silty matrix (Fig. 6D). Intact and ungraded B Comendite accretionary lapilli are evidence of deposi- Pantellerite Phonolite tion on land. This same lapilli tuff also includes strongly Rhyolite vesicular fragments of dark scoria (Fig. 7C), Trachyte like those best known from subaerial lava foun- 0.1 tains of Strombolian-style eruptions on the big

(ppm) island of Hawaii (Mangan and Cashman, 1996). Dacite 2 Trachyandesite Highly vesicular scoria has also been observed Andesite from subaqueous Strombolian-style eruptions at Basanite Zr/TiO depths of 210 m (Siebe et al., 1995) to 969 m in 0.01 Andesitic basalt the ocean (Clague et al., 2003), but submersi- Alkali basalt ble observations show them aggregated into thin graded beds (Clague et al., 2003). Highly Subalkaline basalt vesicular grains in the Ediacaran Mistaken Point Formation (Fig. 7C) are not separated from fi ne matrix or rounded lapilli, unlike fi ne ash and 0.01 0.1 1 10 pumice clasts in lapilli tuffs deposited in Oligo- Nb/Y (ppm) cene lakes (Fig. 6A). Euhedral sanidine crystals (Fig. 7A) are Briscal Formation at Bristy Cove also scattered within tuff matrix like pheno- Mistaken Point Formation at Mistaken Point crysts of crystal fallout tuff on land, rather Mistaken Point Formation at Catalina than tuffs falling through a water column to Drook Formation at Pigeon Cove become normally graded (Sparks and Huang, 1980; Allen and Cas, 1998). Sanidine is evi- Figure 9. Ediacaran tuffs of Newfoundland and St. Pierre and Miquelon dent from both petrographic observations, on (A) alkali-silica fi elds of Le Bas et al. (1986) and (B) zirconium/titania vs. and highly sodic compositions (Data Reposi- niobium/yttrium fi elds of Winchester and Floyd (1977). tory Table R3 [see footnote 1]). These sani- dine grains are not authigenic replacements, like those described by Glover and Hosemann matic eruptions (primary volcaniclastic or pyro- fresh ash of Narbonne (1995) is rare at Mistaken (1967, 1970), because they are elongate laths, clastic). Of 48 fossiliferous surfaces observed Point: Most fossiliferous surfaces were covered without sedimentary inclusions or K-feldspar in the fi eld (Figs. 3 and 5D), only three were by andesitic sandstone. It could be argued that cores, and they are readily weathered from observed to be covered by lapilli or crystal tuff shards were destroyed by metamorphism, but outcrop in the modern humid climate of New- at Catalina, only one at Mistaken Point (surface other well-studied forearc sedimentary rocks of foundland. The conversion of microcline to E of Benus, 1988), and one at Pigeon Cove (Fig. comparable laumontite to prehnite-pumpellyite sanidine has not been observed below 525 °C 5D). All the other fossil surfaces (43) were cov- metamorphic grade have clear remnant outlines (Goldsmith and Laves, 1954), i.e., well above ered by redeposited volcanic sedimentary rocks of devitrifi ed shards (Coombs, 1954). Primary likely temperatures of the transition from zeo- (as proposed by Seilacher, 1992) and not pri- lapilli, scoria, and crystals are preserved at other lite to prehnite-pumpellyite metamorphism of mary tuffs (envisaged by Jenkins, 1992). Thus, stratigraphic levels, as outlined in the following these rocks (Papezik, 1974). The lack of grad- the Conception-style preservation by burial in paragraphs. ing in tuffs of the Mistaken Point Formation is

630 Geological Society of America Bulletin, May/June 2014 Downloaded from gsabulletin.gsapubs.org on May 2, 2014 Newfoundland Ediacaran

A120 B 100 passive margin 100 10 80

O (%) 60 2 1 active continental active continental margin 40 O/Na margin

2

La (ppm) 0.1

K oceanic island Figure 10. Ediacaran tuffs and 20 oceanic continental arc margin sedimentary rocks of New- island arc island arc 0.01 foundland on a variety of tec- 0 50 60 70 80 tonic discrimination diagrams: 0102030 SiO (%) (A) La vs. Th plot of Bhatia Th (ppm) 2 C (1983); (B) alkali vs. silica plot 40 D 0.5 of Roser and Korsch (1986); (C) thorium/tantalum vs. 30 oceanic island arc 0.4 ytterbium plot of Gorton and

(%)

Schandl (2000); and (D) alu- 2 0.3 oceanic mina/silica vs. iron and mag- 20 continental island arc nesia plot of Bhatia and Crook /SiO island arc active continental 3

(1986). margin O 0.2

Th/Ta (ppm) 2 active continental 10 margin

Al 0.1 passive within-plate volcanic zone margin 0 0 0102030 Yb (ppm) 02468101214 Fe2O3+MgO (%) x Mistaken Point sediments Briscal Formation tuff at Bristy Cove Mistaken Point Formation tuff at Mistaken Point Drook Formation tuff at Pigeon Cove Mistaken Point Formation tuff at Catalina

evidence that they fell to land, as in Oregon’s thin, strata-concordant, and composed entirely emplaced bombs as large as 15 cm (–3.9Φ) Oligocene, sanidine tuffs (Hay, 1962; Retal- of clayey siltstone clasts (Figs. 4B aand 5E), i.e., are unlikely to be more than 15 km from their lack et al., 2000). nonvolcanic origin. vents, regardless of mechanism of ejection or Pipe structures of a 30-cm-thick tuff in the composition. Large volcanic clasts of any kind Drook Formation (Figs. 6G and 7D) are com- Distance to Vents may be rare at distances of more than 30 km parable with gas-escape structures in ash beds from vents (Ufnar et al., 1995). emplaced by pyroclastic fl ow on land (Fisher, The size of some volcanic clasts is evidence Large (20 cm) blocks of basaltic scoria in 1979, their fi g. 4B; Kano, 1990). Escape of gas- that terrestrial source vents were near Cata- 1.2–2.3-m-thick tuffaceous beds at Catalina entrained sediment from below creates a dark fi ll lina. A spindle-shaped clast oriented erect in (Figs. 3A, 4A, and 4D) do not show evidence that forms blunt-ended enclaves bent into sinu- an ash bed, depressing the basal dark portion of ballistic emplacement, and these jumbles of ous strain markers by subsequent ash deforma- of the ash, and onlapped by subsequent bed- well-spaced blocks were more likely emplaced tion. These blunt ends infl ated by gas pressure ding (Fig. 4C), is comparable with a volcanic by mass fl ow. These distinctive units of large and sinuous deformation distinguish such pyro- bomb (Tsuya, 1939). This could be a dropped blocks of scoriaceous lava in a fi ne tuffaceous clastic features from sedimentary gas- or water cobble from fl oating ice (as noted in the Gas- matrix are most like volcanic block-and-ash escape structures, which strongly defl ect lami- kiers Formation of Newfoundland by Williams fl ows, which do not run out far from the vol- nations (Frey et al., 2009). Such gas or water and King, 1979; Carto and Eyles, 2011; Retal- canic edifi ce (Ui et al., 1999; Schwarzkopf pressures could not be maintained if volcanic lack, 2013b), and its penetration of volcanic et al., 2005). ash fell through a deep column of water (Sei- ash could be a coincidence, but there is no other lacher, 1992, 1999), or came from an explosive evidence for ice rafting in the Mistaken Point SEDIMENTARY INTERPRETATIONS submarine eruption (Jenkins, 1992). Submarine Formation. As a 15-cm-long volcanic bomb, eruptions into the Mistaken Point Formation are this spindle of basalt would have come from a Turbidites and contourites have featured also ruled out by lack of palagonite and hyalo- vent no more than 5 km distant, judging from prominently in past interpretations of the sedi- clastic breccias (Cas and Wright, 1987; Cole sizes of observed volcanic bombs around Japa- mentary paleoenvironment of the Conception and DeCelles 1991; Busby, 2005; Allen and nese volcanoes (Minakami, 1942). In the wider Group (Misra, 1971; Wood et al., 2003; Ichaso McPhie, 2009). Observed breccia beds were data compilation of Walker (1971), ballistically et al., 2007; Mason et al., 2013), but from the

Geological Society of America Bulletin, May/June 2014 631 Downloaded from gsabulletin.gsapubs.org on May 2, 2014 G.J. Retallack perspective of forearc and nonmarine paleo- 10000 environments (Nance et al., 1991; Pouclet et al., A 2007; Retallack, 2013b), this study also con- 1000 siders tempestites, seismites, tsunamites, and 100 paleosols. 10 Rate of Sediment Accumulation 1

Revised dating of the Conception Group 0.1 (Table 1) necessitates a revision of rates of Sr K Rb Ba Th Ta Nb Ce P Zr Hf Sm Ti Y Yb sedimentation, calculated with allowance for 10000 compaction by Retallack (2013b) as 0.16 ± B 0.01 mm yr–1, but now recalculated using the

same method as 0.16 ± 0.08 mm yr–1. This very 1000 Mantle normalized (ppm) normalized Mantle high rate of sediment accumulation is well in excess of pelagic sedimentary rocks of the east- 100 ern equatorial Pacifi c Ocean (0.002–0.009 mm yr–1), the Atlantic abyssal plain (0.005 mm yr–1), 10 and nearby Atlantic distal turbidite fans (0.012– –1 0.026 mm yr ), and it is more like continental 1 forearc sequences such as the Eugene Forma- La Ce Pr Nd Sm Eu Gd Tb Dy Y Ho Er Tm Yb Lu tion of Oregon (0.13 ± 0.009 mm yr–1) and the Ridge Basin of southern California (2.3 mm yr–1; Retallack, 2013b). x St Pierre & Belle Rivière Groups of St Pierre & Miquelon Briscal Formation at Bristy Cove Mistaken Point Formation at Mistaken Point Turbidites Mistaken Point Formation at Catalina Drook Formation at Pigeon Cove Individual beds of the Conception Group Figure 11. Ediacaran tuffs of Newfoundland and St. Pierre and have been interpreted as turbidites of marine Miquelon on (A) spider diagram, and (B) rare earth element (REE) paleoenvironments (Wood et al., 2003, Ichaso plot, both normalized to mantle of Sun and McDonough (1989). et al., 2007; Mason et al., 2013), but exception can be made for red beds of the Gaskiers For- mation (Retallack, 2013b) and now also for red beds of the Mistaken Point Formation. No beds Mistaken Point Formation visible in slabs (Fig. clay vary strongly from the base of the bed to of the Mistaken Point Formation were seen with 6C) and intraclasts (Fig. 6F) can be distinguished the top (Bouma, 1962; Talling et al., 2012), the entire Bouma (1962) sequence: scoured and from surface oxidation rinds (yellowish red whereas red beds of the Mistaken Point Forma- tool-marked lower surface followed by a thin 5YR5/6) on pyritic horizons, which are brassy tion are dominated by silt from top to bottom claystone breccia, then massive to parallel strati- and unoxidized when cut and polished in slabs (Fig. 8). Such loess-like textures may have been fi ed sandstone and cross-bedded fi ne sandstone (Figs. 6B and 6H). In general, fi re-engine-red widespread in Ediacaran and early Paleozoic and siltstone, grading up into laminated shale. to maroon and purple (Munsell hue 5R-10R) is marine rocks offshore from sparsely vegetated The lack of most of these features was noted hematite, brownish red (Munsell 5YR-10YR low land (Dalrymple et al., 1985), but there are by Wood et al. (2003) and Ichaso et al. (2007), chroma) is goethite, and yellowish red (Munsell many silt-poor shaley turbidites of early Paleo- who proposed that the turbidites were distal 5YR-10YR high chroma) is jarosite. The latter zoic (Shanmugam, 1980; N.R. O’Brien et al., fan to abyssal plain deposits (TC–E). Turbidites is derived by pyrite oxidation (Retallack and 1998) and Ediacaran age (Retallack, 2012a). vary in thickness with distance from source and Dilcher, 2012). Hematite usually represents Turbidites may contain fossils entrained by vio- submarine fan lobe migration (Shanmugam, diagenetic-metamorphic dehydration of original lent erosion of the seafl oor, but at Drook, Mis- 1980; Prélat and Hodgson, 2013). However, the iron oxides, whereas goethite and jarosite refl ect taken Point, and Catalina, the fossils remained Mistaken Point Formation has features incom- current weathering regimes (Retallack, 1997). on surfaces where they grew (Seilacher, 1992, patible with deep water: little basal scour and This explanation is confi rmed by observation 1999; Clapham and Narbonne, 2002; Clapham thin upper shale, sandstone-siltstone couplets that dark reddish gray to maroon colors are per- et al., 2003; Hofmann et al., 2008). sharply divided, and intraformational claystone vasive within the rock and extend to below water Within the turbidite model (Wood et al., 2003; clasts, accretionary lapilli, and sanidine crystals level in coastal outcrops of Newfoundland, but Ichaso et al., 2007; Mason et al., 2013), breccia anomalously dispersed and ungraded (Figs. 4G the brownish and yellowish red color is limited beds have been interpreted as submarine debris and 6C–6D). to thin weathering rinds and does not extend to fl ows, which can be distinguished by highly The red color at Mistaken Point and Catalina the intertidal zone or lower. Red color is unusual erosive and uneven bases, and both reverse and was original, not due to outcrop weathering, for turbidites and the associated cherty to clayey normal clast grading. These features were not because red intraformational claystone clasts are sediment-starved deep-sea facies (Grapes et al., seen in breccia beds observed (Fig. 4B), which found within, not at the base of gray sandstones 1990; Wagreich and Krenmayr, 2005). are here interpreted as seismites. Convolutions (Figs. 4G and 6F). The background purple-red Turbidites are graded by settling through and fl ame structures within sandstones of the color (Munsell dark reddish gray 5R4/1) of the water so that the proportions of sand, silt, and Mistaken Point Formation are unlike basal

632 Geological Society of America Bulletin, May/June 2014 Downloaded from gsabulletin.gsapubs.org on May 2, 2014 Newfoundland Ediacaran

foundering of turbidite sands into abyssal clays 19.3 m, 22.6 m, 64.2 m in Fig. 3B). The hum- current accelerated, comparable with tsunami and ooze (Talling et al., 2012). mocky cross-stratifi cation identifi ed at Mistaken thinning and spreading onshore. Apparently Nevertheless, some beds of the Briscal and Point by Dalrymple et al. (1999) is here regarded bidirectional megaripples (Fig. 4E) within basal Trepassey Formations (Figs. 6B and 7H) show as tectonic kink banding (Williams and King, sandstones may also refl ect a turning point of normal grading of grain size compatible with 1979, erratum). However, the Catalina section tsunami infl ow followed by ebbing. formation by turbidites. Plausible turbidites (Fig. 3A) has co-sets of hummocky cross-strati- Most thin gray sandstones in the Mistaken also were seen in the lower Mall Bay and lower fi cation (Fig. 4F). Hummocky cross-stratifi ca- Point Formation are separated by purple-red Drook Formation at St. Mary and Harbour tion is created by storms in very shallow water siltstones (Figs. 5A–5C), comparable with Main, Newfoundland (Retallack, 2013b). Turbi- (Dott and Bourgeois, 1982; Higgs, 2011). coastal plain paleosols alternating with modern dite facies also are widespread in the Concep- tsunamites (Atwater et al., 1992; Cisternas et al., tion Group east of the Holyrood Horst (Fig. 1). Seismites 2005). Also like modern tsunamites, which These turbidite sequences show grading of grain overlie fl attened salt marsh grasses and other size and evidence of basal bed scour, including Seismites are beds deformed during ground coastal vegetation, cover sands of fossiliferous fl ute casts and basal claystone breccia (Misra, shaking by earthquakes, and they include both layers of the Mistaken Point Formation lack 1971; Williams and King, 1979). They were brittle and plastic deformation, as well as load deeply scoured and eroded bases (Seilacher, not the subject of this study because they con- casting, sand volcanoes, and clastic dikes (Greb 1992, 1999). The inland felling directions of tain no fossils and few volcanic tuffs (Retal- and Dever, 2002; Stewart et al., 2002; Takada fossil fronds followed by offshore orientation of lack, 2013b). and Atwater, 2004; Agnon et al., 2006). Sev- succeeding ripple marks in the Mistaken Point eral likely seismite horizons were seen in the Formation (Fig. 2) are also compatible with a Contourites Mistaken Point Formation: including convolute tsunamite explanation. lamination (Fig. 8C) and bed brecciation and Comparable tsunamites of Thailand, Contour currents are deep-sea (>300 m) foundering (Fig. 5E) at Mistaken Point (12.8, Sumatra , and Oregon are stranded in terraces stable geostrophic currents, which create sedi- 22.6, and 63.8 m in Fig. 3); convolute lamina- of uplifted coastal ranges, unlikely to accumu- mentary sequences laminated to mottled by bio- tion at Catalina (Fig. 6C); and three intraforma- late to thicknesses comparable with the Mis- turbation, with iron-manganese micronodules tional breccia beds (Fig. 4B) at St. Shotts (5.7 taken Point Formation (Atwater and Hemphill- and laminae, microbrecciated shale-chip brec- and 6.7 m in Fig. 3C). Each breccia bed was Haley, 1997; Kelsey et al., 2005). Along the Rio cias, and gravel lags (Stow, 1979; Stow et al., thick and strata concordant with abrupt, planar Maullin , Chile, however, tsunamites accumulate 1998). Individual ripple-marked beds of the boundaries—features considered diagnostic of in a subsiding forearc basin behind a horst of Mistaken Point Formation have been interpreted seismites (Wheeler, 2002). Such thick (>30 cm) coastal hills uplifted as part of the subduction by Wood et al. (2003) as contourites of deep- breccias record earthquakes of Richter magni- complex (Atwater et al., 1992; Cisternas et al., ocean paleoenvironments to explain distinctly tude 7 or more, inducing surfi cial liquefaction 2005). The mapped Holyrood horst of the Ava- different paleocurrent directions inferred from and foundering of clasts in a very low-gradient lon Peninsula (King, 1988; O’Brien et al., 1996) ripple marks and from the direction formerly lake or marine basin (Begin et al., 2005; Agnon may have been such a structure. erect fossils have fallen over. In the Trepassey et al., 2006). Seismites from subduction-zone and Fermeuse Formations, fossil-felling direc- earthquakes are to be expected considering Paleosols tions are aligned with presumed contours at right calc-alkaline volcanic tuffs (Figs. 9–11) and the angle to paleoslope inferred from ripple marks, local structure of basins and fault ridges (King, Red siltstones of the Gaskiers Formation but in the Mistaken Point Formation, frond fos- 1988) of a convergent tectonic margin during are interpreted as paleosols, because of their sils fell upslope, as ripples moved downslope accumulation of the Mistaken Point Formation soil structures and geochemical differentiation (Fig. 2). Bioturbation is not a good indication (O’Brien et al., 1996; Ichaso et al., 2007). (Retallack, 2013b). Paleosols have clays formed of contourites in Ediacaran rocks, which predate by hydrolytic weathering of feldspar and other the evolution of burrowing and trail-making ani- Tsunamites minerals, and thus convex grain-size profi les mals (Liu et al., 2010a, 2010b; Retallack, 2010). (Fig. 8), due to limited and surfi cial clay forma- Nevertheless, the other listed criteria for con- Tsunamites are deposits of large sea waves tion before the advent of land plants (Retallack, tourites (Stow, 1979; Stow et al., 1998) were not generated by subduction-zone earthquakes of 2013a, 2013b). The color changes in red silt- seen in any beds of the Drook, Briscal, Mistaken tectonically convergent margins (Atwater and stones of the Mistaken Point Formation are due Point, or Trepassey Formations. Hemphill-Haley, 1997; Kelsey et al., 2005). not so much to changing grain size (Fig. 8) as Coseismic subsidence and rising water spread to destruction of lamination by mottles, cracks, Tempestites coastal sands with plane lamination far inland and fi laments (Figs. 5C and 6C). Red beds of into tidal marshes and estuarine fl oodplains. the Mistaken Point Formation are dominated by Tempestites are sedimentary beds gener- Sandy units with sharp tops and bottoms are silt from top to bottom (Fig. 8). This grain-size ated by storms, and they have multidirectional separated by clayey intertidal shales and paleo- distribution and the petrographic appearance are scour and tool marks. Their multiple sedimen- sols generated during interseismic uplift and characteristic of loess, not marine sedimentary tary layers include hummocky stratifi cation vegetation recovery. Some thick plane-bedded rocks (Retallack, 2012a, 2013a). Finally, the and plane-bed parting lineation in the high- sandstones overlie channelized basal claystone degree of alteration downward from the surface energy basal part followed by wave ripples in breccia (Fig. 8A), like that of waning fl ow of of the beds is related to the density and tiering of the low-energy upper part (Seilacher, 1982). turbidites and submarine debris fl ows (Talling Ediacaran fossils: Little destruction of bedding The Mistaken Point Formation includes several et al., 2012), and tsunami channels (Kelsey was seen under assemblages of discoid fossils suspected tempestites with planar lamination et al., 2005). Other sandstones have isolated (Heimalora and Aspidella) on gray siltstones, and claystone breccias (Fig. 5E; tops at 2.1 m, shale clasts well above the base (Fig. 4G), as if but extensive alteration was seen under diverse

Geological Society of America Bulletin, May/June 2014 633 Downloaded from gsabulletin.gsapubs.org on May 2, 2014 G.J. Retallack communities of Ediacaran fronds (Beothukis, This is a pattern of preservation comparable with the Mistaken Point biota as sessile organisms Charnia, Charniodiscus) in green-red mottled pollen-barren, red, formerly oxidized paleosols, of intertidal to coastal-plain soils is incompati- siltstones. and it is unlike pollen-rich, gray, marine and ble with interpretation of these fossils as algae Surfaces on which the fossils are found have lacustrine beds (Retallack and Dilcher, 2012). (Hofmann et al., 2008), sponges (Clapham et al., the “old elephant skin” texture of Runnegar and Some fossiliferous surfaces and underlying 2004; Sperling et al., 2011), cnidarians (Gehling Fedonkin (1991), which is characterized by siltstone beds are entirely gray, for example, et al., 2000; Liu et al., 2010a; Misra, 2010), or healed cracks, irregular fi ne ridges, and pustu- below subaerially deposited tuff of the Drook sea pens (Jenkins, 1992), which cannot tolerate lose relief of intergrown radial-growth centers Formation in Pigeon Cove (Fig. 5D), and at some such exposed habitats. Such conditions also do (illustrated from the Mistaken Point Formation levels of the Briscal Formation in Bristy Cove. not support interpretation of Mistaken Point fos- by Gehling and Narbonne, 2007, their fi gs. 5 and These fossiliferous beds have surfi cial old ele- sils as suspension-feeding animals (Lafl amme 8A–8B; Hofmann et al., 2008, their fi gs. 7.4, phant skin surfaces and horizons of pyritic nod- et al., 2004, 2007, 2012a; Gehling and Nar- 16.1, and 18.2). Rivularites repertus is a valid ules at depths of 10–20 cm below that surface, bonne, 2007; Flude and Narbonne, 2008; Nar- ichnospecies for “old elephant skin,” character- like soils (Altschuler et al., 1983) and paleosols bonne et al., 2009; Bamforth and Narbonne, istic of terrestrial microbial earths and biological of the intertidal zone (Retallack and Dilcher, 2009). Discoid fossils (Aspidella, Heimalora) soil crusts (Retallack, 2012b). Mat fragments 2012). These paleosols lack redoximorphic may have been microbial colonies (Grazhdankin and rollups characteristic of aquatic microbial mottles of the red paleosols and were presum- and Gerdes, 2007) that dominated drab pyritic mats (Seilacher, 2007) are unknown from the ably inundated regularly by tides of seawater, paleosols of the former intertidal zone (labeled Conception Group. Lafl amme et al. (2012b) which was a source of sulfate for sulfate-reduc- “a” in Fig. 3). Fungal affi nities are likely for illustrated putative rollups, but these show no ing bacteria (Vepraskas and Sprecher, 1997; fronds (Beothukis, Charnia, Charniodiscus) of scrolls comparable with genuine rollups from Altschuler et al., 1983). Although the Ediacaran the Mistaken Point biota, as argued by Peter- modern deserts (Beraldi-Campesi and Garcia- ocean has been considered as low in sulfate as a son et al. (2003) on the basis of sessile habit, Pichel, 2011), and they are more convinc- modern Swiss lake (Canfi eld et al., 2010), C/S lack of mouth, anus, or body cavities, popula- ingly interpreted as partly decayed groups of ratios of the Mistaken Point Formation are evi- tion structure of indeterminate growth, fractal- fronds (Liu et al., 2011). Elephant skin texture dence of near-modern levels of marine sulfur at modular organization, mycelium-like structures, is a surface expression of intimately admixed some stratigraphic levels, as well as freshwater and strong resistance to burial compaction. organisms and minerals extending deeply into at other stratigraphic levels (Retallack, 2013b). Lichenization of these fungi also may explain the soil, and it cannot be transported intact like Observations made during the course of this abundance and limited overlap of these fossils superfi cial microbial mats (Retallack, 2012b). study support the idea that large fossils of the on organic-poor paleosol surfaces (Retallack, Drab bed tops with ragged downward exten- Mistaken Point Formation lived on dry land 2007). Permineralized lichens are known from sions (Figs. 5A–5B and 8D–8E) are another and in the intertidal zone, like better known the early Ediacaran (ca. 600 Ma) of China (Yuan point of similarity of paleosols and red beds Ediacaran fossils from South Australia (Retal- et al., 2005), so that Mistaken Point fossils would of the Mistaken Point Formation. Downward lack, 2013a). Unlike South Australian paleo- not be the most ancient known lichens. Frond- green fi ngers are evidence of deep connection sols of Ediacaran fossils, which are interpreted like and plausibly lichenized Ediacaran fossils between the fossiliferous “elephant skin” sur- as aridland soils because they are sandy with dominate red paleosols of well-drained coastal- faces and their substrate, like microbial earths pseudomorphs of gypsum and nodules of car- plain paleosols, episodically covered by tsunami rather than aquatic microbial mats (Retallack, bonate (Retallack, 2012a), the Newfoundland sands (labeled “v” in Fig. 3). 2012b). Comparable gleization of paleosol tops Ediacaran paleosols are silty, noncalcareous extending raggedly downward along microbial and nonevaporitic. The Newfoundland paleo- CONCLUSIONS fi lament traces have also been documented from sols were covered occasionally by volcanic tuff, Cambrian (Retallack, 2008, 2011a) and Edia- but more often by sands similar to tsunamites The turbidite depositional model has been caran paleosols elsewhere (Retallack, 2011b, of Oregon and Washington, USA (Atwater and widely invoked for the preservational paleo- 2012a, 2013b). Drab bed tops extending down Hemphill-Haley, 1997; Kelsey et al., 2005), environment of Ediacaran fossils of Newfound- as drab haloes around root traces are ubiquitous and Rio Maullin, Chile (Atwater et al., 1992; land (Misra, 1971; Gardiner and Hiscott, 1988; in Devonian and younger paleosols, in which Cisternas et al., 2005). These Holocene tsuna- Benus, 1988; Narbonne, 1995; Clapham and they formed by gleization during burial of rem- mites cover intertidal to supratidal mud fl ats Narbonne, 2002; Clapham et al., 2003; Wood nant organic matter in the top of the profi le submerged by coseismic subsidence, but subse- et al., 2003; Ichaso et al., 2007). This study soon after burial below a water table (Arafi ev quently they are uplifted for soil formation dur- tested this idea by slabbing, polishing, thin sec- and Naugolnykh, 1998; Retallack and Huang, ing interseismic strain accumulation. tioning, and chemically analyzing individual 2011). Spherical drab haloes extending out- The Newfoundland fossils are in growth posi- beds of the Trepassey, Mistaken Point, Briscal, ward into matrix from organic clasts are known tion, because discoid and spindle fossils are and Drook Formations. Turbidite-like beds and in marine sedimentary rocks (Ekdale, 1977), evenly spaced and seldom overlapping. Frond graded tuffs were found in the upper Trepassey, but these are scattered drab spots in shale, not fossils were toppled in consistent directions by upper Briscal (Figs. 6B and 6H), lower Drook, aggregated into a planar bed top with ragged terminating currents, because they were tethered and Mall Bay Formations (Retallack 2013b), but lower extensions like the red beds of the Mis- by rounded holdfasts (Seilacher, 1992, 2007; surprisingly not at the fossil localities: Pigeon taken Point Formation. Clapham and Narbonne, 2002; Clapham et al., Cove locality of the Drook Formation (Fig. 6G), Neither drab tops nor red bases of the paleo- 2003; Hofmann et al., 2008). Furthermore, vari- Mistaken Point and Catalina localities of the sols preserve organic microfossils in the Mis- ous stages of age and preservation of the fossils Mistaken Point Formation (Figs. 6C–6E), Bristy taken Point Formation, although organic micro- are found, as if some were dead and decayed, but Cove fossil locality of the lower Briscal Forma- fossils have been isolated from the gray Drook juveniles and mature individuals lived together tion, and Portugal Cove South fossil locality and Fermeuse Formations (Hofmann, 1979). before burial (Liu et al., 2011). Interpretation of of the lower Trepassey Formation. Study of

634 Geological Society of America Bulletin, May/June 2014 Downloaded from gsabulletin.gsapubs.org on May 2, 2014 Newfoundland Ediacaran polished slabs and sedimentary structures at the by distal submarine fans, as depicted by Ichaso ACKNOWLEDGMENTS fossil localities supports other genetic models, et al. (2007; Fig. 12B). Periodic earthquakes Field work was funded in part by the University of including tempestites (Seilacher, 1982), ter- explain not only strata-concordant zones of Oregon, under permit from Parks and Natural Areas restrial tuffs (Fisher and Schminke, 1984; Cas soft-sediment deformation and brecciation (seis- Division of Newfoundland and Labrador (director, and Wright, 1987), seismites (Greb and Dever, mites), but thin sands within clayey lagoonal Siân French). Richard Thomas was a superb fi eld assistant and guide. Nathalie Djan Chekar curated 2002; Stewart et al., 2002; Wheeler, 2002; and fl oodplain siltstones (tsunamites). Between polished slabs into collections of The Rooms (Provin- Agnon et al., 2006), tsunamites (Atwater et al., tsunamis and coseismic subsidence, soils (now cial Museum), St. Johns. Thanks are due to Nathan 1992; Atwater and Hemphill-Haley, 1997; paleosols) developed in coastal plains and tidal Sheldon, Guy Narbonne, Doug Erwin, Sarah Tweedt, Kelsey et al., 2005), and paleosols (Retallack, fl ats elevated by interseimic uplift. These well- Marc Lafl amme, Sean O’Brien, Harvey Kelsey, Ray 1997; Retallack, 2011a, 2012a). drained red paleosols of coastal lowlands include Weldon, Paul Wallace, Kathy Cashman, Ilya Binde- man, Paul Hoffman, Jim Watkins, and Nora Noffke This study supports the view of Nance et al. diverse frond fossils (labeled “v” in Fig. 3) in the for useful discussion. Also appreciated were careful (1991), Dec et al. (1992), and Barr and Kerr Mistaken Point Formation, whereas other pyritic reviews and helpful suggestions by Robert Rainbird, (1997) that thick sequences of the Concep- gray paleosols of the intertidal zone (labeled “a” George Jenner, and Sorin Barzoi. tion Group formed in a coastal forearc basin in Fig. 3) have mainly discoid fossils, not only in REFERENCES CITED impounded to the east by a shutter ridge of the Mistaken Point Formation, but in parts of the uplifted Holyrood Granite and Harbour Main Drook, Briscal, and Trepassey Formations. 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