Skip this page .... Cretaceous Research 30 (2009) 939–951 Contents lists available at ScienceDirect Cretaceous Research journal homepage: www.elsevier.com/locate/CretRes Molluscan biostratigraphy and paleomagnetism of Campanian strata, Queen Charlotte Islands, British Columbia: implications for Pacific coast North America biochronology James W. Haggart a,*, Peter D. Ward b, Timothy D. Raub c, Elizabeth S. Carter d,1, Joseph L. Kirschvink c a Geological Survey of Canada, 625 Robson Street, Vancouver, British Columbia V6B 5J3, Canada b Department of Geological Sciences, University of Washington, Seattle, WA 98195-1310, USA c Division of Geological and Planetary Science, California Institute of Technology 170-25, Pasadena, CA 91125, USA d Department of Geology, Portland State University, Portland, OR 97207-0751, USA article info abstract Article history: A previously uncollected fauna of ammonites, bivalves, and other molluscs, associated with radiolarian Received 9 June 2008 microfossils, has been newly recognized near Lawn Hill on the east coast of central Queen Charlotte Accepted in revised form 13 February 2009 Islands, British Columbia. The regional biostratigraphic zonation indicates that the Lawn Hill fauna is Available online 3 March 2009 correlative with the Nostoceras hornbyense zonule of the Pachydiscus suciaensis ammonite biozone, recognized in the Nanaimo Group of southeast Vancouver Island. The Nostoceras hornbyense Zone (new) Keywords: is herein proposed for strata of Pacific coast Canada containing the zonal index. Several molluscan taxa Campanian present in the Lawn Hill section are new to British Columbia and the ammonite fauna suggests that the Maastrichtian Ammonite Nostoceras hornbyense Zone is late Campanian in age, supported by radiolarian taxa present in the Inoceramid section. Strata sampled in the Lawn Hill section preserve reversed-polarity magnetization, considered Magnetostratigraphy likely correlative with Chron 32r. The presence of the Nostoceras hornbyense Zone on Queen Charlotte Queen Charlotte Islands Islands is the first recognition of this zone in Canada north of central Vancouver Island and represents the youngest Cretaceous known in this region. Campanian radiolarians identified from the Lawn Hill section are also the first recognized from the Pacific coast of Canada. Crown Copyright Ó 2009 Published by Elsevier Ltd. All rights reserved. 1. Introduction several morphogeological provinces of the Canadian Cordilleran region and includes the offshore island systems of western British Cretaceous strata are distributed widely across Queen Charlotte Columbia and Alaska, including the island systems of Queen Islands, British Columbia (Haggart, 1991, 2004), with major outcrop Charlotte Islands and Vancouver Island in British Columbia, and belts found in the Langara Island to White Point region on the parts of the southeastern Alaska archipelago (Fig. 1). northwest coast, and in the Skidegate Inlet and Cumshewa Inlet The principal geological components of the Insular belt are the areas of the central part of the islands (Fig. 1). Cretaceous strata are Wrangellia and Alexander terranes, the former well developed on inferred to be distributed also in the offshore regions adjacent to Queen Charlotte Islands, the latter in southeast Alaska. The Baja Queen Charlotte Islands and collectively, these deposits accumu- British Columbia (‘‘Baja BC’’) hypothesis proposes large-magnitude lated in the Hecate basin (Hunt, 1958; Haggart, 1993; Mossop et al., northward translation of, at minimum, the Wrangellia terrane of 2004), inferred to have developed in a fore-arc setting westward of the Insular belt relative to the North American craton during Late an active magmatic arc (Haggart, 1991, 1993; Higgs, 1991; Thomp- Cretaceous and Early Tertiary time. The hypothesis remains son et al., 1991; Lewis et al., 1991; Lyatsky and Haggart, 1993). controversial (Mahoney et al., 2000; Enkin, 2006) as the paleo- The Hecate basin accumulated on a varied topography of older magnetic data upon which it is based (i.e., Bogue et al., 1995; Ague Mesozoic and Paleozoic(?) sedimentary, volcanic, and plutonic and Brandon,1996; Irving et al.,1996; Ward et al.,1997; Housen and rocks collectively assigned to the Insular belt. This feature is one of Beck, 1999; Enkin et al., 2001, 2003; Haskin et al., 2003; Housen et al., 2003; Bogue and Gromme, 2004; but see Stamatakos et al., 2001 and others) are methodologically sound yet seemingly con- tradicted by numerous geological and paleobiogeographical infer- * Corresponding author. E-mail address: [email protected] (J.W. Haggart). ences (i.e., Mahoney et al., 1999; Butler et al., 2001a,b, 2006; 1 Mailing address: 69745 Old Wagon Road, Sisters Oregon 97759, USA. Kodama and Ward, 2001; but see Miller et al., 2006). 0195-6671/$ – see front matter Crown Copyright Ó 2009 Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.cretres.2009.02.005 940 J.W. Haggart et al. / Cretaceous Research 30 (2009) 939–951 Fig. 1. Location map of Queen Charlotte Islands, British Columbia, showing location of Cretaceous (Campanian) outlier at Lawn Hill. Area of Cretaceous Hecate basin indicated in grey in inset. AT ¼ Alexander terrane, WT ¼ Wrangellia terrane. Note inferred paleo-high separating Cretaceous Hecate and Nanaimo basins of west coast Canada. We present herein new paleontological and paleomagnetic data Columbia, some 650 km south of Queen Charlotte Islands. In from Upper Cretaceous (Campanian to lowermost Maastrichtian?) addition, while the paleomagnetic data are considered of insuffi- strata of Queen Charlotte Islands. The faunal data establish for the cient quality and number to establish a paleolatitude suitable for first time the presence of upper Campanian strata on Queen paleogeographic analysis, recovery of reversed-polarity magneti- Charlotte Islands, with correlatives exposed in southern Alaska and zation in calcareous concretions sampled in the section is consid- on Vancouver Island and associated islands of southwestern British ered most likely correlative with Chron 32r (ca. 71–73 Ma). J.W. Haggart et al. / Cretaceous Research 30 (2009) 939–951 941 2. Regional geological setting accumulation in a stable tectonic setting (Haggart, 1991, 1993; Lewis et al., 1991). Continuous deposition initiated in Valanginian time and Wrangellia terrane hosts sedimentary basins of various ages continued unabated until the Campanian. Cretaceous strata are built on a distinctive and characteristic Upper Triassic massive dominantly shelf-related clastic deposits, with minor, geographically- volcanic succession (basalts of the Karmutsen Formation and restricted shallow-marine to subaerial(?) Upper Cretaceous volcanic equivalents), possibly erupted onto pre-existing oceanic basement rocks and deeper-water, slope turbidite facies (Haggart, 1991). (Jones et al., 1977). On Queen Charlotte Islands, these oceanic Calcareous concretions are found at numerous levels in the strati- basalts are succeeded by fringing reef carbonates and deeper water graphic succession; these often contain well-preserved fossil mate- calcareous clastic facies of the Upper Triassic to lowermost Jurassic rials, especially in Santonian and Campanian deposits. Kunga Group (Fig. 2) (see Lewis et al., 1991). Overlying, Lower Correlation of Cretaceous successions of Queen Charlotte Islands Jurassic clastic-rich sedimentary strata of the Maude Group reflect has relied principally on ammonites and other molluscan fossil deposition at some distance from active volcanic activity. By Middle groups (McLearn, 1972; Jeletzky, 1970a, 1977; Haggart, 1991, 1995; to early Late Jurassic time, the locus of magmatism occupied the Haggart and Higgs, 1989), although recent studies of radiolarian Queen Charlotte Islands region; Yakoun and Moresby groups faunas (Haggart and Carter, 1993; Carter and Haggart, 2006)have preserve extensive active arc volcanic and associated epiclastic demonstrated the correlation potential of this fossil group, espe- rocks, respectively, in geographic and temporal association with cially for poorly-fossiliferous deep-water strata of the islands. widespread plutonism. Middle to Late Jurassic magmatic activity Paleogene plutonic rocks are distributed widely on Queen may reflect the initiation of subduction in the region (Lewis and Charlotte Islands (Haggart, 2004) and may document final amal- Ross, 1989; Thompson et al., 1991; Lewis et al., 1991). gamation of Wrangellia terrane with North America (Lewis et al., The Cretaceous stratigraphic succession of Queen Charlotte 1991), although this is by no means established. Subsequently, the Islands records a prolonged period of basin subsidence and sediment Mio-Pliocene Masset Formation represents widespread volcanic activity that accompanied regional extension, and initiated Queen Charlotte Islands’ modern trans-tensional setting (Hickson, 1991). 3. Lithostratigraphy The stratigraphic succession at Lawn Hill is exposed in a geographically-restricted (w 250 m long) outcrop in the intertidal region on the east coast of Graham Island, Queen Charlotte Islands (Fig. 1; NTS 103G/05: Lawnhill 1:50,000-scale topographic map). The Lawn Hill outcrop is an outlier of Cretaceous rocks on the east side of the Sandspit fault (Fig. 1) and comprises the easternmost outcrop of the informally named Tarundl formation (Haggart, 2002), the youngest unit of the Lower-Upper Cretaceous Queen Charlotte Group (Haggart, 1991) found on Queen Charlotte Islands (Fig. 2). The Tarundl formation has limited geographic distribution