Late Cretaceous climatic trends and a positive carbon isotope excursion at the Santonian–Campanian boundary in British Columbia, northeastern Pacific

Sedimentary Geology 295 (2013) 77–92

Contents lists available at ScienceDirect

Sedimentary Geology journal homepage: www.elsevier.com/locate/sedgeo

Late Cretaceous climatic trends and a positive carbon isotope excursion at the Santonian–Campanian boundary in British Columbia, northeastern Pacific Yuri D. Zakharov a,⁎, James W. Haggart b, Graham Beard c, Peter P. Safronov a a b c

Far Eastern Geological Institute, Russian Academy of Sciences (Far Eastern Branch), Stoletiya Prospect 159, Vladivostok 690022, Russia Natural Resources Canada, Geological Survey of Canada, 605 Robson Street, Vancouver, V6B 5J3 British Columbia, Canada Qualicum Beach Museum, 151 West Sunningdale Qualicum Beach, V9K 1K7 British Columbia, Canada

a r t i c l e

i n f o

Article history: Received 21 April 2013 Received in revised form 28 July 2013 Accepted 6 August 2013 Available online 14 August 2013 Editor: B. Jones Keywords: Late Cretaceous palaeotemperatures Campanian positive δ13C excursion British Columbia

a b s t r a c t This study presents oxygen and carbon isotope data obtained from well-preserved ammonite and bivalve fossils of the Upper Cretaceous Nanaimo Group of southwestern British Columbia, Canada. Palaeotemperatures for the late Santonian–Campanian of British Columbia, determined on the basis of oxygen isotopic analysis, suggest a õdirect relationship with basic Late Cretaceous climatic trends (e.g. temperature fall toward the cool climates of the Maastrichtian). The coolest Campanian palaeotemperatures were calculated from the ammonite Pachydiscus cf. ootacodensis (Stoliczka) (11.3–26.4 °C) and the bivalve Inoceramus vancouverensis Shumard (about 19.7 °C), from the late Campanian Occidentalis Zone (Northumberland Formation). In contrast, the highest palaeotemperatures were obtained from the shells of presumed earliest Campanian bivalves and varied between 25.1 and 33.7 °C, which we assume to represent the regional expression of the early Campanian warming event. The Santonian–Campanian boundary in British Columbia is associated with a positive δ13C excursion (to 4.2‰) which appears to be contemporaneous with the Santonian–Campanian Boundary Event reported recently from other regions (i.e., Europe, Tunisia, Japan, and Tibet). The lack of organic-rich laminated black shales (indicating strong oxygen depletion in the marine realm) through the Santonian–Campanian of the Nanaimo Group, including the Santonian–Campanian boundary interval, seems to be in agreement with the suggestion that most of the world's oceans were characterised by oxygen-rich deep waters during Coniacian–Campanian time. © 2013 Elsevier B.V. All rights reserved.

1. Introduction The first data on oxygen isotopic composition of Cretaceous mollusc shells from Canada were reported by Tsujita and Westermann (1998) and Zakharov et al. (2006a, 2007), who investigated aragonite preserved from Late Cretaceous ammonites and bivalves from Alberta. Cretaceous carbonate fossils from other areas of North America (South Alaska, South Dakota, Montana, and California) have been isotopically investigated by Cochran et al. (2003) and Zakharov et al. (2006a, 2007, 2011, in press)). According to the oxygen isotope data presented in these papers, mean Late Cretaceous temperature values for the studied areas of North America provided by molluscs (e.g. early Campanian ammonite Submortoniceras, bivalves, and gastropods from California; late Campanian Baculites and Hoploscaphites ammonites from Montana and South Dakota; late Campanian-early Maastrichtian Rhaeboceras, Jeletzkytes, and Baculites ammonites from Alberta; latest Campanian Rhaeboceras from Montana; and latest Campanian Baculites and early Maastrichtian Pachydiscus ammonites from South Alaska) are all within ⁎ Corresponding author. Fax: +7 423 2317847. E-mail address: [email protected] (Y.D. Zakharov). 0037-0738/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.sedgeo.2013.08.004

acceptable ranges and credible, on the assumption of normal salinity and temperature ranges (22.2–26.8 °C). A few Cretaceous molluscs from North America show very light δ18O values, which suggests some fresh-water influence rather than diagenetic alteration, considering their good preservation (Zakharov et al., 2006a, in press) and low 87Sr–86Sr ratio (Cochran et al., 2003). These shells include late Campanian bivalves (Zakharov et al., 2006a, in press) and late Campanian–early Maastrichtian ammonites Baculites and Placenticeras (Tsujita and Westermann, 1998; Zakharov et al., 2007) from Alberta; early Campanian nuculitid bivalves and the ammonite Submortoniceras from California (Zakharov et al., 2007); late/early Maastrichtian bivalves Cymbophora and Tancredia and the ammonites Discoscaphites, Sphenodiscus, and Haploscaphites from South Dakota (Cochran et al., 2003; Zakharov et al., in press); and the latest Campanian ammonite Rhaeboceras halli (Meek) from Montana (Zakharov et al., 2007). δ13C values in some early Campanian (California) and apparently middle Maastrichtian (South Dakota) mollusc shells from North America are 2.6‰ (Zakharov et al., 2007) and 3.1‰ (Cochran et al., 2003), respectively, which are in agreement with some data provided for other regions outside of North America (e.g., Huber et al., 1995;

78

Y.D. Zakharov et al. / Sedimentary Geology 295 (2013) 77–92

Norris et al., 2001; Saltzman and Thomas, 2012; Zakharov et al., 2012). Only limited data on carbon isotopic composition of Cretaceous (late Campanian) fossils from Canada has been presented previously (Zakharov et al., 2007). Unfortunately, oxygen and carbon isotope data from Cretaceous fossils from Canada is very restricted, and such data are completely lacking for the Pacific coast region. Consequently, interpretations of palaeotemperature and oceanographic trends for the northeast Pacfic region are lacking. Given that the Pacific coast of Canada represents the eastern margin of the Late Cretaceous world's largest oceanic body, the proto-Pacific Ocean, it is critical to understand isotopic trends in this region to fully understand global climatic patterns. In this paper, we present an analysis of Late Cretaceous (Santonian–Campanian) palaeotemperatures and carbon anomalies obtained from isotopic compositions of well-preserved mollusc fossils of the Upper Cretaceous Nanaimo Group of southwestern British Columbia (Fig. 1). Understanding the oxygen and carbon isotope composition of late Santonian and Campanian fossils from British Columbia sheds light on some palaeotemperatures trends and peculiarities of bioproductivity of marine basins in the middle latitudes of North America during Late Cretaceous time.

2. Geological setting Upper Cretaceous strata of the Nanaimo Group are exposed widely on southeastern Vancouver Island (Muller and Jeletzky, 1970) and rest on Palaeozoic-Mesozoic sedimentary and volcanic rocks of the Wrangellia terrane, part of the Insular superterrane, which extends discontinuously northward from southern British Columbia into southern Alaska (Jones et al., 1977). The Insular superterrane includes rocks of the Coast Mountains of western British Columbia, Vancouver Island and Haida Gwaii (formerly Queen Charlote Islands), in the region extending from southeastern Alaska to the Wrangell Mountains in northern Alaska. Wrangellia terrane on Vancouver Island and Haida Gwaii consists of middle and upper Palaeozoic arc-related volcanic and sedimentary rocks, latest Devonian plutons, and Triassic plateau basalts overlain by Late Triassic carbonate rocks (Jones et al., 1977; Monger, 2011). Overlying and intruding these Triassic and Palaeozoic rocks is a thick and widespread succession of uppermost Triassic to Middle Jurassic arc-related volcanic and sedimentary rocks and plutons.

The Upper Cretaceous Nanaimo Group on Vancouver Island locally overlies Wrangellia terrane unconformably on the west side of its outcrop belt, the Coast Mountains (Coast belt) on its east side, and is in inferred fault contact with rocks of the San Juan Islands to the southeast (Haggart et al., 2011). Nanaimo Group strata accumulated in an elongate northwest-southeast—trending depocentre during Turonian to Maastrichtian time, although there is no constraint on its original extent to the west or north (Mustard, 1994; Haggart et al., 2003, 2005, 2011). Nanaimo Group strata reflect a wide variety of environmental settings, from coastal swamps and lagoons to beach and shoreface environments of the inner shelf, the biologically rich and diverse mid- to outer-shelf, and submarine-fan environments of the upper slope. The precise latitudinal location of Nanaimo Group deposition is a matter of controversy. Palaeomagnetic data suggest that these rocks accumulated on Wrangellian basement at low latitudes in Late Cretaceous time, at the approximate latitude of the Baja California margin, and then moved northward to approximately their present position during the latest Cretaceous and possibly early Tertiary (e.g., Irving, 1985; Umhoefer, 1987; Irving and Brandon, 1990; Ward et al., 1997; Krijgsman and Tauxe, 2006). This northward displacement is referred to as the “Baja British Columbia (“Baja BC”) hypothesis” and implies large-magnitude northward translations of the Insular superterrane relative to the North American craton since the Late Cretaceous. The hypothesis remains controversial, however, as a large variety of geologic, biogeographic, and detrital zircon provenance data suggest that the Wrangellia terrane was at approximately its present latitudinal position by mid-Cretaceous, possibly even Middle Jurassic, time (see summary and references in Haggart et al., 2009). 2.1. Lithostratigraphy and sedimentology Study of the Cretaceous rocks of Vancouver Island and adjacent islands in the Strait of Georgia, as well as on Haida Gwaii, began in the mid-1800 s, fueled by search for the extensive coal deposits which had been discovered along the Pacific coast. The first palaeontological assessment of the Cretaceous age of these rocks was made by Newberry (1857), on the basis of fossils from Nanaimo, British Columbia, and these and other fossils from the Nanaimo Group succession were subsequently described in several other publications (Meek, 1861; Whiteaves, 1879, 1895, 1901, 1903; White, 1889; Usher, 1952; Muller and Jeletzky, 1970; Ward, 1978a,b; Haggart and Ward, 1989;

Fig. 1. Location map of investigated Cretaceous outcrops in the Vancouver Island region of British Columbia. A — Location of the investigated area in North America; existing isotopic data from neighboring areas: 1 — Alberta (Tsujita and Westermann, 1998; Zakharov et al., 2006a, 2007); 2 — Montana (Zakharov et al., 2006a, 2007); 3 — South Dakota (Zakharov et al., 2006a, 2007, in press-a,b); 4 — California (Zakharov et al., 2006a, 2007), 5 — South Alaska (Zakharov et al., 2006a, 2011). B — Vancouver Island region; locations: 1 — Brannan Lake (upper Santonian siltstone of Haslam Formation); 2 — Stephenson Point, Departure Bay (uppermost Santonian to lowermost Campanian sandstone, conglomerate, and siltstone of Comox Formation); 3 — Buckley Bay area (middle Campanian mudstone and siltstone of Cedar District Formation); 4 — Hornby Island (upper Campanian mudstone and siltstone of Northumberland Formation).

Y.D. Zakharov et al. / Sedimentary Geology 295 (2013) 77–92

Haggart, 1990). The possibility that the succession included the Santonian–Campanian boundary interval was first suggested (Usher, 1952). More recently, strata of the Nanaimo Group have been studied with respect to their petroleum potential (e.g. Bustin, 1990; England and Bustin, 1995). The Nanaimo Group succession is divided into eleven lithostratigraphical units (formations), in ascending stratigraphic order as follows: (1) Comox, (2) Haslam, and (3) Extension formations, corresponding to the Santonian to lower Campanian; (4) Pender and (5) Protection formations (mainly lower Campanian); (6) Cedar District Formation, corresponding to the middle Campanian and to the lowest part of the upper Campanian; (7) De Courcy, and (8) Northumberland formations, corresponding to the upper Campanian and lowest Maastrichtian; and the (9) Geoffrey, (10) Spray, and (11) Gabriola formations, which are poorly fossiliferous by presumably include Maastrichtian and possibly lowermost Tertiary deposits (Usher, 1952; Muller and Jeletzky, 1970; Ward, 1978a; Haggart, 1990; Mustard, 1994; Haggart et al., 2011; Ward et al., 2012). Some units of the Nanaimo Group (e.g. Comox Formation) are time-transgressive. The Santonian–Campanian boundary in British Columbia appears to be approximately coincident with the base of the Pender Formation, and the Campanian–Maastrichtian boundary is located within the upper part of the Northumberland Formation. The well preserved fossils used for our isotopic analyses were collected only from the Comox (level II), Haslam (level I), Cedar District (level III), and Northumberland

79

(level IV) formations (Fig. 2), which are briefly characterised in the following. The Comox Formation (Santonian–lowermost Campanian), includes locally non-marine and shallow marine shore face deposits and typically consists of a basal transgressive facies of conglomerate and sandstone, locally up to several hundred meters in thickness, that typically onlaps basement rocks, mostly Upper Triassic basalts of the Karmutsen Formation (see Mustard et al., 2003). Strata of the Comox Formation fine upwards and the unit is locally time-transgressive, with the oldest deposits of mid-Santonian age. In some areas, however, the Comox Formation strata are dated as early Campanian by ammonites and bivalves, reflecting local variation in the timing of transgression. A 3-m thick richly fossiliferous succession of the Comox Formation sandstone strata was sampled by us (Stephenson Point locality) and contains aragonitic bivalve mollusc shells and shell fragments (i.e., specimens II(1), II-1(2) in our collection — Table 1). Continued subsidence in the Nanaimo Basin resulted in deposition of deeper water shelf deposits of the Haslam Formation (upper Santonian), which conformably overlies the sandstone of the Comox Formation or rests locally upon Upper Triassic pillow basalts or late Paleozoic arc-related volcanic and sedimentary rocks (Haggart et al., 2011). The Haslam Formation (up to 150 m), is interpreted as an outer shelf facies and consists of fossiliferous concretionary mudstone with subordinate amounts of siltstone and interbedded sandstone and basal pebble conglomerate (Haggart et al., 2011). Fossil material in our collections comes from calcareous concretions and includes bivalves (i.e., samples St(1) and St(2)) and ammonites (Ps, Ps(2), and Ps(3) — Tables 1 and 2) with original aragonite. The basal Comox and overlying Haslam Formation of the Nanaimo Group are widespread and comprise a basal transgressive succession. Overlying Nanaimo Group deposits reflect continued basin deepening to outer shelf and slope depths and include a variety of deposits which accumulated in outer shelf to submarine fan environments. These upper units of the Nanaimo Group stratigraphic succession are not as widespread as the basal Comox and Haslam formations. The Cedar District Formation (213–244 m thick) consists of middle Campanian to lowest upper Campanian mudstone and thin-bedded silty shale and siltstone with lesser conglomerate and fine-grained sandstone. Much of the unit is inferred to have been deposited in midto outer shelf environments (Mustard, 1994; Mustard et al., 2003; Haggart et al., 2011). The finer grained facies of the Cedar District Formation typically contain abundant macro- and microfossils, including aragonite-bearing inoceramid bivalves (specimens II(4)-9, II(4)-10, and II(4)-11 — Table 1). The Northumberland Formation (610–823 m thick) includes upper Campanian to ?lowest Maastrichtian recessive-weathering silty mudstone and shale interbedded with thin, fine-grained sandstone and siltstone and minor thicker coarse-grained sandstone. Calcareous concretions are common in the unit and often contain aragonitic ammonite and bivalve shells. The Northumberland Formation is typically interpreted as a slope deposit (see Mustard, 1994; Mustard et al., 2003), although the abundance and diversity of fauna suggests that the unit may include shelf deposits locally. On Hornby Island, the Northumberland Formation yields a well preserved molluscan fauna with aragonitic shells (samples Ph(1) and M — Tables 1 and 2). 2.2. Mollusc record and biostratigraphy

Fig. 2. Stratigraphical position of investigated mollusc-bearing strata (horizons I–IV) within the Nanaimo Group in the Vancouver Island–Hornby Island area.

Biostratigraphic subdivision of the Nanaimo Group has relied mainly on ammonites, inoceramid bivalves, and planktic and benthic foraminifera (McGugan, 1979; Haggart, 1991). The earliest contributions were the late 19th century studies of Whiteaves (1879, 1895, 1901, 1903) and White (1889). Based on new and complementary results from biochronostratigraphic analysis of ammonite fossil-assemblages and magnetostratigraphy, Ward et al. (2012) presented a revised biostratigraphic zonation for late Santonian–Maastrichtian strata of the

80

Species (locality)

Stage (Zone)

Diagenetic stage Aragonite (%)

Admixture (e.g., α-SiO2)

Color

St(1)-1

Sphenoceramus elegans (Vancouver Is., Brannan Lk.) Same shell Same shell Same shell Same shell Same shell Same shell Sphenoceramus elegans (Vancouver Is., Brannan Lk.). Same shell Sphenoceramus elegans (Vancouver Is., Brannan Lk.). Idonearca truncata (Vancouver Is., Brannan Lk.). Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Undetermined bivalve

Upper Santonian (Yokoyamai) 5.0

2nd

90 ± 3

No

Cream

0.02

−2.33

25.50

Same level Same level Same level Same level Same level Same level Same level

7.0 11.3 19.0 31.2 46.0 51.0 30.5

2nd 1st 2nd 3rd 1st 1st 2nd

93 95 93 69 95 97 90

3 3 5 3 3 3 3

No No SiO2 (trace) No No No No

Cream Cream Cream Cream Cream Cream Cream

0.68 1.56 1.24 0.25 1.57 0.30 0.47

−2.55 −2.55 −2.82 −2.39 −2.76 −2.58 −2.28

26.46 26.46 27.63 25.76 27.37 26.59 25.29

Same level Same level

36.2 21.5

2nd 2nd

85 ± 3 85 ± 5

SiO2 (trace) SiO2 (trace)

Cream Cream

−0.21 0.02

−2.52 −2.32

26.33 25.46

Same level

8.0

2nd

77 ± 3

No

White

0.52

−3.01

28.46

Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Lowest Campanian (Yokoyamai)

13.0 17.0 21.0 24.0 26.8 29.0 31.8 34.0 37.0 39.0 40.0 44.0 46.0 49.0 51.5 52.5 55.5 58.5 71.5 Fragment (5 × 8 mm)

2nd 2nd 1st 1st 1st 1st 1st 1st 1st 1st 1st 1st 1st 1st 1st 1st 1st 1st 1st 1st

93 ± 77 ± 96 ± 96 ± 97 ± 100 100 97 ± 100 100 100 100 100 100 97 ± 100 100 100 100 100

No No No No No No No No No No No No No No SiO2 (trace) No No No No No

White White White White White White White White White White White White White White White White White White White White

−0.84 −1.41 0.16 0.01 −1.48 1.47 0.64 −0.12 0.76 0.41 1.17 −0.38 −0.73 −0.17 −0.67 −0.67 −0.37 −0.57 0.17 3.69

−3.26 −3.87 −2.84 −3.07 −3.49 −3.44 −2.78 −3.42 −2.95 −3.33 −3.14 −2.98 −3.21 −0.17 −3.30 −3.06 −3.09 −2.78 −2.62 −3.38

29.54 32.19 27.72 28.72 30.64 30.32 27.46 30.23 28.20 29.84 29.02 28.33 29.32 16.13 29.71 28.67 28.80 27.46 26.76 30.06

St(1)-2 St(1)-3 St(1)-4 St(1)-5 St(1)-6 St(1)-7 St(2)-1 St(2)-2 St(3)-1 Id-1 Id-2 Id-3 Id-4 Id-5 Id-6 Id-7 Id-8 Id-9 Id-10 Id-11 Id-12 Id-13 Id-14 Id-14a Id-15 Id-16 Id-17 Id-18 Id-19 II(1)-1

Location (L, mm)

δ13C (VPDB) (‰) δ18O (VPDB) (‰) ToC

Sample

Diagenetic alteration

± ± ± ± ± ± ±

3 3 3 3 3

3

3

Y.D. Zakharov et al. / Sedimentary Geology 295 (2013) 77–92

Table 1 Carbon and oxygen isotope analyses of bivalve shells from the upper Santonian (Haslam Fm.) and lowermost Campanian (Comox Fm.), mid-Campanian (Cedar District Fm.), and upper Campanian (Northumberland Fm.), British Columbia (L — length).

1st 1st 1st 1st 1st 1st 1st 1st 1st 1st 1st 1st – – 1st 1st – – 1st 1st 1st 1st 1st –

100 95 ± 3 100 100 97 ± 3 100 100 100 100 100 100 100 – – 100 100 – – 100 95 ± 3 100 96 ± 3 100 0 (prismatic layer)

4.74 3.41 3.29 4.53 3.4 3.44 4.54 1.33 3.18 1.91 4.24 4.25 1.28 4.37 1.66 4.25 3.64 2.41 4.23 2.84 1.34 1.86 2.70 2.61

−2.23 −2.77 −3.07 −2.77 −2.95 −3.37 −2.32 −3.38 −3.54 −3.49 −3.29 −3.04 −3.84 −2.33 −3.81 −3.08 −2.77 −3.38 −2.91 −3.60 −4.18 −4.22 −4.20 −3.32

25.07 27.41 28.72 27.41 28.20 30.02 25.46 30.06 30.76 30.54 29.67 28.59 32.06 25.50 31.93 28.76 27.41 30.06 28.02 31.02 33.53 33.71 33.62 26.36

13.0 9.5 16.0

– – –

0 (prismatic layer) No Silvery-white 1.98 0 (prismatic layer) No Silvery-white 1.32 ? Secondary calcite (many), analcime Cream −3.76

−2.42 −3.88 −3.25

22.21 29.08 -

M-2 M-3 M-4 M-5

22.0 38.0 44.6 51.0

– – – 4th

? ? ? 48 ± 5

Cream Cream Cream Cream

−4.52 −4.91 −0.95 −1.98

−4.05 −3.71 −1.64 −1.31

– – – 21.08?

M-6

Same shell

Same level

60.0

3rd

60 ± 3

Cream

−2.93

−1.82

23.29?

M-7 M-8 M-9 M-10

Same shell Same shell Same shell Same shell

Same level Same level Same level Same level

72.0 91.0 97.0 113.0

3rd 3rd 3rd 4th

69 57 55 38

Cream Cream Cream Cream

−4.8 −2.26 1.21 −3.08

−0.98 −1.78 −1.35 −1.87

19.65 23.12? 21.25? 23.51?

Inoceramid bivalve Inoceramid bivalve Inoceramid bivalve Inoceramid bivalve Inoceramid bivalve Inoceramid bivalve Inoceramid bivalve Inoceramid bivalve Inoceramid bivalve Inoceramid bivalve Inoceramid bivalve Sphenoceramus? sp. Inoceramid bivalve Inoceramid bivalve Inoceramid bivalve Inoceramid bivalve Same shell Same shell Same shell Inoceramid bivalve Undetermined bivalve Same shell Same shell Sphenoceramus sp. B

II(4)-10 II(4)-11 M-1

± ± ± ±

3 3 3 3

No No No No No No No No No No No No – – No No – – No No No No No No

Secondary calcite (many), analcime Secondary calcite (many), analcime Secondary calcite (many), analcime Secondary calcite (~52%), analcime (trace), α-SiO2 (trace) Secondary calcite (~40%), analcime (trace), α-SiO2 (trace) Secondary calcite (~31%) Secondary calcite (~43%) Secondary calcite (~45%) Secondary calcite (~62%)

White White Cream White White White White White White White White White White Pinky-white Pinky-white Cream Cream Cream Cream Cream Cream Cream Cream Silvery-white

Y.D. Zakharov et al. / Sedimentary Geology 295 (2013) 77–92

Fragment (9 × 14 mm) Fragment (9 × 15 mm) Fragment (16 × 20 mm) Fragment (9 × 11 mm) Fragment (11 × 15 mm) Fragment (7 × 15 mm) Fragment (11 × 16 mm) Fragment (9 × 14 mm) Fragment (8 × 9 mm) Fragment (6 × 11 mm) Fragment (8 × 11 mm) Fragment (8 × 10 mm) Fragment (5 × 10 mm) Fragment (3 × 3 mm) Fragment (6 × 9 mm) 9.0 29.0 37.0 12.0 7.0 7.0 9.0 13.0 13.0

Sphenoceramus sp. B Sphenoceramus sp. A Inoceramus vancouverensis (Hornby Is.) Same shell Same shell Same shell Same shell

Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Middle Campanian (Vancouverense) Same level Same level Upper Campanian (Occidentalis) Same level Same level Same level Same level

II(1)-2 II(1)-3 II(1)-4 II(1)-5 II(1)-6 II(1)-7 II(1)-8 II(1)-9 II(1)-10 II(1)-11 II(1)-12 II(1)-13 II(1)-14 II(1)-15 II(1)-16 II-1(2)-1 II-1(2)-2 II-1(2)-3 II-1(2)-4 II-1(2)-5 II-1(2)-6 II-1(2)-7 II-1(2)-8 II(4)-9

81

82

δ13C (VPDB), ‰

δ18O (VPDB), ‰

T, oC

Brownish-cream

−3.49

−3.06

28.67

No No

Brownish-cream Brownish-cream

−3.35 −1.12

−3.11 −2.22

28.89 25.03

100

No

Brownish-cream

−2.64

−2.69

27.07

1st

100

No

Cream

−2.19

−2.50

26.24

32.0 32.8 33.0 33.5 34.0 34.5 35.0 35.5 37.5 38.5 19.8

1st 1st 1st 1st 2nd 2nd 2nd 2nd 1st 2nd 1st

100 95 ± 100 100 87 ± 92 ± 89 ± 88 ± 100 94 ± 100

No No No No No No No No No No No

Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream

−1.83 −2.25 −2.06 −1.92 −2.03 −1.31 −2.00 −1.90 −1.96 −1.86 −3.59

−2.71 −2.85 −2.59 −2.76 −2.99 −2.65 −3.09 −2.86 −2.55 −2.66 −2.79

27.15 27.76 26.63 27.37 28.37 26.89 28.80 27.80 26.46 26.94 27.50

Same level Upper Campanian (Occidentalis)

26.0 ~44.0

1st 2nd

100 90 ± 5

No No

Cream Cream

−0.71 −2.43

−2.71 0.32

27.15 14.00

Same level Same level Same level Same level Same level Same level Same level Same level

~45.0 ~47.0 ~50.0 ~52.0 ~55.0 ~58.0 ~61.0 ~63.0

2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd

88 89 92 83 77 77 62 77

No No No No No No No No

Cream Cream Cream Cream Cream Cream Cream Cream

−1.70 −1.98 −2.9 −3.11 −2.34 −2.10 −1.28 −0.95

0.42 0.48 0.22 −0.19 0.45 −0.52 0.08 0.37

13.57 13.31 14.44 16.22 17.35 17.65 15.04 13.79

Sample

Species

Stage (Zone)

Location (H in mm)

Diagenetic stage

Aragonite, %

Admix-ture, % (e.g., SiO2)

Color

Ps-1

Pseudoschloenbachia umbulazi (Vancouver Is., Brannan Lk.) Same shell Pseudoschloenbachia umbulazi (Vancouver Is., Brannan Lk.) Pseudoschloenbachia umbulazi (Vancouver Is., Brannan Lk.) Pseudoschloenbachia umbulazi (Vancouver Is., Brannan Lk.) Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Pseudoschloenbachia umbulazi (Vancouver Is., Brannan Lk.) Same shell Pachydiscus cf ootacodensis (Hornby Is.) Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell

Upper Santonian (Yokoyamai)

28.4

1st

100

No

Same level Upper Santonian (Yokoyamai)

18.2 N49.0

1st 1st

95 ± 5 100

Upper Santonian (Yokoyamai)

N54.0

1st

Upper Santonian (Yokoyamai)

31.0

Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level

Ps-2 Ps-3 Ps-4 Ps(2)-1 Ps(2)-2 Ps(2)-3 Ps(2)-4 Ps(2)-5 Ps(2)-6 Ps(2)-7 Ps(2)-8 Ps(2)-9 Ps(2)-10 Ps(2)-11 Ps(3)-1 Ps(3)-2 Ph(1)-1 Ph(1)-2 Ph(1)-3 Ph(1)-4 Ph(1)-5 Ph(1)-6 Ph(1)-7 Ph(1)-8 Ph(1)-9

Diagenetic alterations

± ± ± ± ± ± ± ±

5

5 5 5 5 5

5 5 5 5 5 5 5 5

Y.D. Zakharov et al. / Sedimentary Geology 295 (2013) 77–92

Table 2 Carbon and oxygen isotope analyses of ammonoid shells from the upper Santonian (Haslam Fm.) and the upper Campanian part of the Northumberland Formation in British Columbia (H — height).

Ph(2)-2 Ph(2)-3

Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Same shell Inner whorl apparently of the same shell (fragment 1) Inner whorl apparently of the same shell (fragment 2) Inner whorl apparently of the same shell (fragment 3)

No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No

Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream Cream

−1.38 −1.39 −1.10 −0.99 −0.96 −1.31 −1.04 −0.12 −1.10 −0.93 −0.48 −0.82 −0.30 −0.99 −0.63 −0.39 0.01 0.37 0.58 0.71 0.57 0.66 0.12 −0.13 −0.38 −0.29 −1.32 −2.22 −3.29 2.61 −4.51

0.11 −0.35 0.43 0.40 0.47 0.42 0.51 0.61 0.42 0.48 0.59 0.51 0.43 0.26 0.42 0.23 0.46 0.44 0.61 0.58 0.60 0.82 0.71 0.79 0.94 0.95 0.72 0.51 −2.50 −1.75 −0.97

14.91 16.91 13.53 13.66 13.35 13.57 13.18 12.74 13.57 13.31 12.83 13.18 13.53 14.26 13.57 14.39 13.40 13.48 12.74 12.87 12.79 11.83 12.31 11.96 11.31 11.27 12.27 17.61 26.24 22.99 19.60

91 ± 3

No

Cream

−2.72

−0.52

17.65

88 ± 3

No

Cream

−2.17

−0.34

16.87

Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level Same level

~64.0 ~65.0 ~66.0 ~67.0 ~68.0 ~69.0 ~70.0 ~71.0 ~72.0 ~73.0 ~74.0 ~75.0 ~76.0 ~77.0 ~78.0 ~79.0 ~80.0 ~81.0 ~82.0 ~83.0 ~89.0 ~90.0 ~91.0 ~92.0 ~94.0 ~96.0 ~97.0 ~100.0 ~105.0 ~110.0 ~19.0–22.0

2nd 2nd 2nd 2nd 1st 1st 2nd 1st 2nd 1st 2nd 2nd 2nd 2nd 2nd 2nd 1st 1st 2nd 2nd 2nd 1st 1st 2nd 1st 2nd 2nd 2nd 2nd 3rd 2nd

91 90 87 86 97 97 93 95 93 95 93 94 91 93 93 94 95 95 93 92 80 96 95 94 96 89 93 93 71 54 87

Same level

~19.0–22.0

2nd

Same level

~19.0–22.0

2nd

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

3 3 5 5 3 3* 3* 3 3 3 3 3* 3 3 3 3 3 3 5 5 5 3 3* 5 3 3 3 3 3 5 3

X-ray powder analyses were carried out mainly using DRON-3 (control analyses for some samples, indicated by asterisk, was made for control, using Mini Flex II).

Y.D. Zakharov et al. / Sedimentary Geology 295 (2013) 77–92

Ph(1)-10 Ph(1)-11 Ph(1)-12 Ph(1)-13 Ph(1)-14 Ph(1)-15 Ph(1)-16 Ph(1)-17 Ph(1)-18 Ph(1)-19 Ph(1)-20 Ph(1)-21 Ph(1)-22 Ph(1)-23 Ph(1)-24 Ph(1)-25 Ph(1)-26 Ph(1)-27 Ph(1)-28 Ph(1)-29 Ph(1)-30 Ph(1)-31 Ph(1)-32 Ph(1)-33 Ph(1)-34 Ph(1)-35 Ph(1)-36 Ph(1)-37 Ph(1)-38 Ph(1)-39 Ph(2)-1

83

84

Y.D. Zakharov et al. / Sedimentary Geology 295 (2013) 77–92

northeast Pacific region, founded in a significant part on the Nanaimo Group succession. The following ammonite faunal zones are recognized within the Santonian–Maastrichtian interval, in ascending stratigraphic order: (1) Eubostrychoceras elongatum; (2) Canadoceras yokoyamai (with common sphenoceramid bivalves); (3) Submortoniceras chicoense (with Baculites chicoensis); (4) Hoplitoplacenticeras vancouverense; (5) Baculites inornatus; (6) Metaplacenticeras cf. pacificum (subzones Baculites rex below and Baculites subanceps above); (7) Didymoceras nebrascense; (8) Nostoceras hornbyense; (9) Baculites occidentalis; and (10) Nostoceras hyatti. Among these, the Yokoyamai, Vancouverense, and Occidentalis zones have a better oxygen and carbon isotope record. 2.2.1. Yokoyamai Zone The late Santonian to early Campanian Canadoceras yokoyamai Zone corresponds to the Haslam and Extension formations of the Nanaimo basin and is marked by the first appearance datum of the ammonite Canadoceras yokoyamai (Jimbo), the zonal index, with associated bivalve species Sphenoceramus elegans (Sokolov), Sphenoceramus sakhalinensis (Sokolov), Sphenoceramus orientalis (Sokolov), and Idonearca truncata (Gabb); the ammonite Pseudoschloenbachia (Pseudoschloenbachia) umbulazi (Baily) is also a common component (Jeletzky, 1970; Haggart et al., 2011). 2.2.2. Vancouverense Zone The latest early Campanian–earliest middle Campanian Hoplitoplacenticeras vancouverense Zone corresponds approximately to lower Cedar District Formation and is characterised by the occurrence of Hoplitoplacenticeras vancouverense (Meek) (zonal index). Other ammonites of the Vancouverense zone are Hoplitoplacenticeras cf. plasticum (Paulcke), Canadoceras newberryanum (Meek), Canadoceras arbucklensis (Anderson), Pachydiscus neevesi Whiteaves, Pachydiscus cf. egertoni (Forbes), Baculites inornatus Meek, and Anapachydiscus sp. aff. subtililobatus (Jimbo) (Jeletzky, 1970; Ward, 1978a,b; Haggart, 1990), associated with inoceramid bivalves (e.g. Inoceramus vancouverensis Shumard, Inoceramus subundatus Meek, Sphenoceramus sp. A, and Sphenoceramus sp. B). 2.2.3. Occidentalis Zone The lower part of the late Campanian Baculites occidentalis Zone corresponds to the upper part of the Northumberland Formation in part and is characterised on Hornby Island by ammonite species such as Phyllopachyceras forbesianum (d'Orbigny), Neophylloceras ramosum (Meek), Neophylloceras lambertense Usher, Pseudophyllites indra (Forbes), Pachydiscus ootacodensis (Stoliczka), Pachydiscus suciaensis (Meek), Diplomoceras notabile Whiteaves, Anisoceras cooperi (Gabb), “Hamites” obstrictus Jimbo, Baculites occidentalis Meek (zonal index), and Nostoceras hornbyense Whiteaves (Usher, 1952; Jeletzky, 1970). Among bivalve molluscs Inoceramus spp. (Usher, 1952) is the most abundant. 3. Material and methods Late Cretaceous (late Santonian, earliest, middle, and late Campanian) mollusc shells were collected for isotope analyses from Vancouver Island and Hornby Island, British Columbia. Original molluscan material used for oxygen and carbon isotope analyses consisted of: (1) aragonitic ammonite and bivalve shells from the late Santonian Haslam Formation of the Brannan Lake area; (2) aragonitic bivalve shells and their fragments from basal beds of the Comox Formation of the Departure Bay area on Vancouver Island, here of early Campanian age; (3) aragonitic bivalve shells from the middle Campanian part of the Cedar District Formation of the Buckley Bay area on Vancouver Island; and (4) aragonitic bivalve and ammonite shells from the late Campanian portion of the Northumberland Formation on Hornby Island. We estimated the degree of preservation of mollusc specimens by using the following criteria: (1) visual signs; (2) percentage of aragonite

in a structure when analyzing shells or their elements originally composed of 100% aragonite, which are predominant in our collection; (3) degree of integrity of microstructure, determined under a scanning electron microscope (SEM); and (4) X-ray powder analyses to identify possible diagenetic admixtures (e.g. α-SiO2). In previous studies, we have recognized four typical stages in diagenic alteration of aragonitic mollusc shells: 1st stage, where secondary calcite is absent (100% aragonite) or represented by a small proportion, not more than 1–5%; 2nd stage, characterised by the appearance of a larger proportion (5–30%) of secondary calcite; 3rd stage, where shell material consists of approximately 30–50% secondary calcite; and 4th stage, characterised by the presence of more than 50% secondary calcite; this stage also exhibits a very pronounced change in isotopic composition (Zakharov et al., 1975, 2006a). However, the shell material from British Columbia we studied exhibits mainly the 1st stage diagenetic alteration and rarely the 2nd stage (with the exception of a single late Campanian bivalve shell showing the 3rd stage). Thus, specimens which have preserved more or less their primary original isotopic composition were used for our isotopic investigation. Microstructure of cephalopod and bivalve molluscs from British Columbia was investigated using SEM (Zeiss EVO 40 XVP) at the Institute of Marine Biology RAS, Vladivostok. Before SEM observation, small fragments of mollusc shells were taken and without etching were coated with gold using an ion coater. The SEM photographs of some investigated ammonite (Pseudoschloenbachia) and bivalve (e.g., Sphenoceramus) shells (Fig. 3) additionally show that these specimens fulfill the diagenetic screening criteria and they were therefore considered suitable for isotopic analyses. X-ray analysis of shells confirmed the lack of secondary admixtures, including α-SiO2. Isotope samples for our investigation were taken from narrow transects along growth striations on the surface of the shell. These transects crossed all shell layers except the innermost. In ammonite shells, for instance, the innermost layer covers the entire living chamber and is therefore inadequate for detailed analyses. Oxygen and carbon isotope measurements were carried out using a Finnigan MAT-252 mass spectrometer at Far Eastern Geological Institute (FEGI), Vladivostok. The laboratory gas standard used in the measurements was calibrated relatively to NBS-19 standard δ13C = 1.93‰ and δ18O = −2.20‰ (Coplen et al., 1983). Reproducibility of replicate standards was always better than 0.1‰. X-ray powder analyses were carried out using difractometers at FEGI (DRON-3 and MiniFlex II), following the method of Davis and Hooper (1963). The following equation (Grosman and Ku, 1986) was used for palaeotemperature calculation:  

18 T C ¼ 20:6–4:34 δ Oaragonite –δw : In this equation T (°C) is the ambient temperature; δ18Oaragonite is the measured oxygen-isotope values of aragonite (versus VPDB), and δw (‰) is the ambient water isotope ratio (versus VSMOW). A δw of −1.0‰ is often assumed to be appropriate for an ice-free world (e.g., Shackleton and Kennett, 1975; Huber et al., 2002; Price and Hart, 2002). 4. Stable isotope results 4.1. Upper Santonian Three shells of the ammonite Pseudoschloenbachia umbulazi from our collection (Ps, Ps(2), Ps(3) characterised by 89–100% aragonite), as well as three shells of the bivalves I. truncata (Id) and S. elegans (St(1), St(2); 85.3–100% aragonite) from the upper Santonian level (Yokoyamai Zone, Haslam Formation), exposed at Brannan Lake, Vancouver Island, were investigated. The results of the stable-isotope analyses are given in Tables 1 and 2. From the I. truncata shell, for

Y.D. Zakharov et al. / Sedimentary Geology 295 (2013) 77–92

85

Fig. 3. SEM photomicrographs of investigated cephalopod and bivalve molluscs: A–B — Pseudoschloenbachia umbulazi (no. Ps(2)), Vancouver Island, upper Santonian; C–D — Sphenoceramus elegans (no. 2(1)), Vancouver Island, upper Santonian; E–F — undetermined bivalve (no. II(1)–8), Vancouver Island, lower Campanian. All scale bars = 2 μm.

example, 19 samples were taken. Aragonitic shell material from the late Santonian ammonite P. umbulazi and bivalves I. truncata and S. elegans produced δ18O values varying from −3.0 to −2.3‰, from −3.9 to −2.6‰, and from −2.8 to −2.3‰, respectively. Only a single sample, taken from the I. truncata specimen, shows an unusually heavy δ18O value (−0.2‰). Thus, oxygen-isotopic analyses suggest that investigated portions of late Santonian ammonite and bivalve shells from British Columbia were secreted in similar temperature/salinity conditions. Late Santonian I. truncata and S. elegans shells are also characterised by similar δ13C values, varying from −1.8 to +0.8‰ and from −0.8 to +1.0‰, respectively (Table 2). However, significantly lighter δ13C values, ranging from −4.3 to −1.2‰, were recorded in all investigated well-preserved shells of the ammonite P. umbulazi. This evidence suggests that these ammonite and bivalve shells were secreted in different depth levels of the shallow water marine basin (Epipelagic Zone). X-ray analysis shows that some ammonite shells from the same stratigraphic level are diagenetically altered to a significant degree and

consist mainly of secondary barite and calcite, with only minor portions of aragonite. Such samples were not used for isotopic investigation.

4.2. Lowest Campanian Fragments of 16 bivalve shells, characterised by 95–100% aragonite, were investigated from the uppermost beds of the Cretaceous succession (Comox Formation) exposed at Stephenson Point, in Departure Bay. Strata underlying these beds have provided sphenoceramid bivalves and a fragment of the ammonite Canadoceras cf. yokoyamai, suggesting that the lower beds are correlative with the Yokoyamai zone (Haggart et al., 2011). The obtained isotopic values are given in Table 2. δ18O and δ13C values for the inoceramid bivalves, as well as several undetermined bivalves, vary between −4.2 and −2.2‰ and between +1.3 and +4.7‰, respectively. All investigated bivalve shells were apparently secreted in similar temperature/salinity conditions.

86

Y.D. Zakharov et al. / Sedimentary Geology 295 (2013) 77–92

Fig. 6. Bivalve Idonearca truncata (no. ID), upper Santonian: isotopic palaeotemperatures.

Fig. 4. Pachydiscus cf. ootacodensis, Hornby Island, upper Campanian: location of investigated samples.

4.3. Middle Campanian The isotopic composition of calcitic prismatic layers of two small Sphenoceramus sp. A shells (sample II(4)–11 — Table 1) and three small Sphenoceramus sp. B shells (samples II(4)–9 and II(4)–10 Table 1) from the early middle Campanian level of the Cedar District Formation (Buckley Bay road-cut) were investigated. δ18O and δ13C values for these samples range between −3.9 and −2.4‰ and +1.3 and +2.6‰, respectively. All investigated bivalve shells are thus inferred to have been secreted in similar temperature/salinity conditions.

(38–69% aragonite in most well preserved places), from the upper Campanian level of the Northumberland Formation of Hornby Island were investigated. From the first shell, 42 samples were taken (Fig. 4). δ18O and δ13C values for this ammonite shell range between −2.5 and +1.0‰ and −4.5 and +2.6‰, respectively, while values for the most well preserved bivalve shell areas range between −1.9 and −1.3‰ and −2.9 and +1.2‰, respectively. Some rare light δ18O values found in the P. cf. ootacodensis shell are accompanied by lower aragonite content (e.g. 72%) and may be caused by some diagenetic alteration. According to X-ray analysis, the earliest ontogenetic stages of I. vancouverensis are represented mainly by secondary calcite and analcime, with only a small portion of original aragonite (Table 1). These samples were excluded from isotopic analyses. 5. Environmental interpretation

4.4. Upper Campanian 5.1. Palaeotemperature trends A single ammonite, Pachydiscus cf. ootacodensis (sample PH(1) — Table 2), represented by 70–97% aragonite, and a single bivalve I. vancouverensis shell. (sample M Table 1), partly diagenetically altered

The Mesozoic–early Cenozoic is considered as a typical greenhouse period, contrary, for instance, to the Late Carboniferous or present

Fig. 5. Mollusc mode of life reconstruction, based on data of isotopic composition of Late Cretaceous fossil shells from the Vancouver Island area, British Columbia. A — late Santonian, B — earliest Campanian, C — middle Campanian, D — late Campanian.

Y.D. Zakharov et al. / Sedimentary Geology 295 (2013) 77–92

Fig. 7. Ammonite Pseudoschloenbachia umbulazi (no. Ps(2)), upper Santhonian: aragonite content, oxygen- and carbon-isotope composition, and palaeotemperatures.

87

icehouse periods. The mid-Cretaceous (from the Albian–Cenomanian boundary to Coniacian time) was marked apparently by one of the major Mesozoic warming peaks (e.g., Norris et al., 2001; Jenkyns et al., 2004) and is characterised by globally averaged sea surface temperature more than 14 °C warmer than those of today, a lack of permanent ice sheets, and ~100–200 m higher sea levels than today (e.g., Takashima et al., 2006). As we have recognised previously (Smyshlyaeva et al., 2002; Moriya et al., 2003; Zakharov et al., 2003, 2005, 2006b, 2007), Cretaceous ammonite shells were most likely secreted near the bottom of shallow marine basins, where the animals spent most of their life. It is therefore considered likely that palaeotemperatures calculated from isotopic composition of Late Cretaceous ammonites from British Columbia, as well as of associated benthic invertebrates, mainly reflect nearbottom environments of the shelf (Fig. 5). To determine sea-surface palaeotemperatures of such shallow-water basins, we have suggested the application of a small correction, about 2.0–2.5 °C, to near-bottom temperatures (Zakharov et al., 2007). Oxygen isotope compositions of the late Santonian bivalves I. truncata and S. elegans and the ammonite P. umbulazi from the Yokoyamai Zone

Fig. 8. Plots of oxygen- and carbon-isotope data for aragonitic mollusc shells from the Cretaceous of the Vancouver Island area, British Columbia.

88

Y.D. Zakharov et al. / Sedimentary Geology 295 (2013) 77–92

(Haslam Formation), show that the investigated portions of their shells were secreted at very similar palaeotemperature intervals, at 23.1– 32.4 °C (on average 28.0 °C), 25.0–27.6 °C (on average 26.8 °C), and 26.4–28.9 °C (on average 27.3 °C), respectively (Figs. 6–8). Similar or somewhat higher palaeotemperatures were obtained from shells of the earliest Campanian bivalve molluscs (inoceramid and unnamed bivalves) from the uppermost Santonian to lowermost Campanian: 25.1–33.7 °C (on average 29.5 °C). The Santonian– Campanian boundary level in British Columbia corresponds apparently to a significant warming interval for this region (Figs. 5, 8). Additionally, similar and somewhat lower palaeotemperatures were calculated from oxygen isotope composition of middle Campanian Inoceramus sp. A (32.3 °C) and Inoceramus sp. B (25.9–29.8 °C) from the Vancouverense Zone (Cedar District Formation) (Fig. 8). In contrast, palaeotemperatures obtained from P. cf. ootacodensis and I. vancouverensis of the late Campanian Occidentalis Zone of the Northumberland Formation are significantly lower (11.3–26.4, on average 13.9 °C, and about 19.7 °C, respectively) (Figs. 8, 9) than those calculated from the fossils of the Haslam, Comox, and Cedar District formations. The existence of latest Campanian climatic optimum, proposed by Zakharov et al. (2007) on the basis of restricted data from Montana (Zakharov et al., 2007), Koryak Upland (Zakharov et al., 2006a), and New Zealand (Stevenson and Clayton, 1971), is not supported by the new data from British Columbia. The new isotopic palaeotemperature data suggest that during late Santonian to middle Campanian time the Vancouver Island region of Canada was located apparently within the tropical–subtropical climatic zone, which was notably reduced at the very end of the Cretaceous. It seems to be connected with the fall of temperature that started in

general during the late Campanian (Occidentalis Zone) of British Columbia (Fig. 10). Isotopic palaeotemperatures during the late Santonian– Campanian, determined on the basis of oxygen isotopic analysis of well-preserved molluscan shells from the studied area, suggest a direct relationship with basic Late Cretaceous climatic trends (tendency for temperature fall to the cool climates of the Maastrichtian) defined by both isotopic (e.g., Pirrie and Marshall, 1990; Barrera, 1994; Huber et al., 1995; Clarke and Jenkyns, 1999; Miller et al., 1999; Huber et al., 2002; Cochran et al., 2003; Zakharov et al., 2007, 2011, in press-a,b) and palaeobotanical data (e.g., Krassilov, 1979; Boyd, 1994; Markevich, 1995; Bugdaeva et al., 2000; Spicer and Herman, 2010; Herman, 2011). It is most indicative by the example of isotopic oceanic bottom palaeotemperature, showing marked temperature reduction during Campanian–Maastrichtian in both the high and middle-low palaeolatitudes (i.e., 11.8 and 11.9 °C have been obtained from middle Campanian benthic foraminifera of the mentioned latitudes, respectively, 10.2 and 9.0 °C from late Campanian benthic foraminifera of the mentioned latitudes, respectively), and 4.0–5.5 and 9.0 °C from Maastrichtian benthic foraminifera of these latitudes, respectively (Boersma and Shackleton, 1981; Huber et al., 2002). This tendency also agrees well with some palaeobotanical evidence. For instance, early Campanian Barykov flora in the high palaeolatitude Koryak Upland in the Russian Far East is characterised by the development of cycadophytes, appearance of rare platanoids, and reduction of fern diversity (Golovneva and German, 1998), which corresponds to thermal warming. The early Campanian Jonker flora and its equivalents in middle paleolatitude Russian Far East are also characterised by the development of heat-loving plants (e.g., Oncolea, laurel-form plants,

Fig. 9. Possible seasonal growth temperatures for the Pachydiscus cf. ootacodensis from the upper Campanian of Hornby Island.

Y.D. Zakharov et al. / Sedimentary Geology 295 (2013) 77–92

89

Fig. 10. Late Santonian through late Campanian temperature trends and Santonian–Campanian boundary positive carbon-isotope anomaly: evidence from British Columbia. Zones: 1 — Elongatum; 2 — Yokoyamai; 3 — Chicoense; 4 — Vancouverense; 5 — Inornatus; 6 — cf. Pacificum; 7 — Nebrascense; 8 — Hornbyense; 9 — Occidentalis; 10 — Hyatti. Abbreviations: M.S. — Middle Santonian, Upper Sant. — Upper Santonian, Low. Ma — Lower Maastrichtian.

cycadophytes) (Krassilov, 1979; Markevich and Bugdaeva, 2001). However, the middle Maastrichtian flora of the lower Tsagayan Formation of the Zeya–Bureya Basin in middle palaeolatitude Russian Far East is characterised by reduction of heat-loving plants (Markevich and Bugdaeva, 2001), and the late Maastrichtian Rarytkin and Augustovka floras of the high- and middle-latitude areas in Far East are characterised by their complete disappearance (Krassilov, 1979; Herman and Lebedev, 1991). 5.2. Positive carbon isotope excursion Isotopic δ13C values derived from shells of molluscs from the upper Santonian Yokoyamai zone range between −3.9 and −2.3%. In contrast, shell carbonate of molluscs from the uppermost part of the Stephenson Point succession, in beds overlying those containing Yokoyamai zone fossils, display the heaviest δ13C values (to 4.2‰). The transition from light to heavy values recorded in the strata is abrupt and significant. Given that the sampled beds at Stephenson Point exhibit isotopic values quite distinct from those of the underlying Yokoyamai zone strata, we suggest that this abrupt isotopic shift reflects the existence of a positive carbon isotope excursion. This is the first suggestion of this event in British Columbia. Noteworthy, this event in British Columbia is associated with high subtropical temperatures, as indicated by the oxygen record (Fig. 10). The above-mentioned excursion appears to correspond to the socalled Santonian–Campanian Boundary Event, previously reported from many European sections (i.e., southern England — Jenkyns et al., 1994; Jarvis et al., 2002, 2006; Belza et al., 2012; Germany — Schönfeld et al., 1991; southern France — Jarvis et al., 2002; Carpathians

— Melinte-Dobrinescu and Bojar, 2010), as well as from southern Tibet (Li et al., 2006), Sakhalin (Hasegawa et al., 2003), Hokkaido (Takashima et al., 2010), USA (Pratt et al., 1993; Gale et al., 2008), and southern high palaeolatitudes (Huber et al., 1995). The most important among these sections for global correlation seems to be the Naiba River section on Sakhalin Island, Russian Far East, with an integrated record of carbon isotopic ratios recorded in terrestrial organic matter from Cenomanian–Maastrichtian successions (Hasegawa et al., 2003) and magnetostratigraphy of the same interval (Kodama et al., 2000, 2002). One of the most prominent δ13C maxima in the Naiba River section, located just below the Santonian–Campanian boundary, is coincident with the base of the chron 33r (Hasegawa et al., 2003), recognized also in British Columbia (Ward et al., 2012). The late Campanian negative carbon isotope excursion in British Columbia, associated with a positive excursion for δ18O, reflects significant cooling and more likely corresponds to the late Campanian event documented in southern England (Jenkyns et al., 1994; Jarvis et al., 2006; Belza et al., 2012), southwestern France (GSSP of the Campanian– Maastrichtian boundary) (Thibault et al., 2012), and the Shatsky Rise of the tropical Pacific (Jung et al., 2012). This latter locality is in turn succeeded by the Campanian–Maastrichtian negative excursion (Jenkyns et al., 1994, 1995; Jarvis et al., 2006; Schovsbo, 2007; Belza et al., 2012; Jung et al., 2012; Zakharov et al., 2012; Nascimento-Silva et al., in press), and coincides apparently with eustatic sea-level fall (Miller et al., 2003). In times of absence of polar ice on the Earth, including most of the Cretaceous period, hydrological conditions probably differed considerably from current patterns both in the poleward transport of large equatorial warm water masses and in the weaker vertical circulation of waters.

90

Y.D. Zakharov et al. / Sedimentary Geology 295 (2013) 77–92

Discovered variations in marine 13C/12C ratios recorded in mollusc carbonate from the Upper Cretaceous of British Columbia seem to be related to variations in different environmental factors, such as carbon budget, upwelling, and primary productivity (Alcala-Herrera et al., 1992). This latter factor was apparently dependent in turn on global changes in solar (Zakharov et al., 2006a) and volcanic activity, provoking volcanic degassing and/or methane bursts and episodic anoxia (Takashima et al., 2006; Weissert, 2012). Jarvis et al. (2006) have drawn attention to the interesting fact that the Late Cretaceous (Cenomanian– Campanian) carbon isotope curve is similar in shape to supposedly eustatic sea-level curves: increasing δ13C values accompanied Cretaceous sea-level rise and transgression, and falling δ13C values characterised sea-level fall and regression. Some negative carbon-isotope excursions have been documented with the duration of several ten thousands to hundred thousands of years (Saltzman and Thomas, 2012). Wagreich (2009, 2012) proposed that the Coniacian–Santonian oceanic anoxic event (OAE 3), the last of the Cretaceous OAEs, was not a global event but a regional one. This event was restricted essentially to the low- to middle-latitudinal parts of the Atlantic Ocean (e.g., Demerara Rise) and some adjacent epicontinental basins such as the Maracaibo Basin and the Western Interior Basin, in contrast to the preceding global OAEs (early Aptian OAE 1a, Aptian–Albian OAE 1, and late Cenomanian OAE 2) (e.g., Naidin, 1984; Weissert and Erba, 2004; Takashima et al., 2006). Taking into account that the Turonian–Campanian interval was the main depositional period of the Cretaceous oceanic red beds (Wang et al., 2005, 2009; Wagreich, 2009, 2012; Hu et al., 2012), it can be concluded (e.g., Wagreich, 2009, 2012) that most of the oceans during that time were characterised by oxygen-rich deep waters. In spite of presence of a positive carbonate δ13C peak N4‰, within the Turonian–Campanian interval in British Columbia (just at the Santonian–Campanian boundary) no organic-rich facies have been found there, which seems to be in agreement with Wagreich's (2009) idea. Many authors (e.g., Jenkyns, 2010; Saltzman and Thomas, 2012) consider that positive δ13C excursions mark all OAEs. However, the basal part of OAE 1a black shales in the Ulyanovsk Basin of the Russian Platform distinctly corresponds to a negative δ13C excursion (Zakharov et al., 2013). The reason for the significant differences of δ13C values of molluscal shells at the Santonian–Campanian boundary in different regions is still unexplainable (it seems to be connected partly with changes in depth of molluscan habitat). 6. Conclusions 1 Major oxygen-isotope fluctuations preserved within mollusc shells from the upper Santonian–upper Campanian interval in British Columbia follow basic Late Cretaceous climatic trends (tendency of temperature fall to the cool climates of the Maastrichtian), previously established from Upper Cretaceous sections in Europe, Pacific, Atlantic and many other regions on the basis of both the isotopic and palaeobotanical data. 2 The Santonian–Campanian boundary interval in the studied section of British Columbia is associated with a negative excursion for δ18O, which corresponds to a climatic optimum and a positive excursion for δ13C, but is characterised by lack of black shales. 3 The positive carbon-isotope excursion newly recognized in British Columbia (uppermost Santonian/lower Campanian Comox Formation) is contemporaneous with the δ13C Santonian–Campanian Boundary Event recognized in many other regions such as Europe, Tunisia, Sakhalin, Hokkaido, USA, Tibet, and possibly in some highlatitude regions of the Southern Hemisphere. Acknowledgements We extend our gratitude to anonymous reviewers for providing valuable editorial comments that substantially improved this paper. For help in finding references, we are indebted to Prof. J. Sha (Nanjing).

We are indebted also to the Far Eastern Branch of Russian Academy of Sciences for a grant 12-III-A-08-024, which has made this work possible. References Alcala-Herrera, J.A., Grossman, E.L., Gartner, S., 1992. Nannofossil diversity and equitability and fine-fraction δ13C across the Cretaceous/Tertiary boundary at Walvis Ridge Leg 74, South Atlantic. Mar. Micropaleontol. 20, 77–88. Barrera, E., 1994. Global environmental changes preceding the Cretaceous–Tertiary boundary: early-late Maastrichtian transition. Geology 22, 877–880. Belza, J., Goderis, S., Keppens, E., Vanhaecke, F., Claeys, P., 2012. An emplacement mechanism for the mega-block zone within the Chicxulub crater (Yucatán, Mexico) based on chemostratigraphy. Meteorit. Planet. Sci. 47 (3), 400–413. Boersma, A., Shackleton, N.J., 1981. Oxygen- and carbon-isotope variations and planktonic-foraminifer depth habitats, Late Cretaceous to Paleocene, central Pacific, Deep Sea Drilling Project Sites 463 and 465. Initial Rep. Deep Sea Drill. Proj. 62, 513–526. Boyd, A., 1994. Some limitations in using leaf physiognomic data as a precise method for determining paleoclimates with an example from the Late Cretaceous Pautût Flora of West Greenland. Palaeogeogr. Palaeoclimatol. Palaeoecol. 112, 261–278. Bugdaeva, E.B., Markevich, V.S., Bolotskiy, Y.L., Sorokin, A.P., 2000. Melovoye vymiraniye dinozavrov: vzglyad paleobotanikov [Cretaceous extinction of dinosaurus: palaeobotanical view]. Vestnik Dalnevostochnogo Otdeleniya Rossijskoy Akademii Nauk, 1, pp. 80–88 (in Russian). Bustin, R.M., 1990. Stratigraphy, sedimentology, and petroleum source rock potential of the Georgia basin, southwest British Columbia and northwest Washington State. Current Research, Part F, Geological Survey of Canada, Paper 90-1F, pp. 103–108. Clarke, L.J., Jenkyns, H.C., 1999. New oxygen isotope evidence for long-term Cretaceous climatic change in the Southern Hemisphere. Geology 27 (8), 699–702. Cochran, J.K., Landman, N.H., Turekian, K.K., Michard, A., Schrag, D.P., 2003. Paleoceanography of the Late Cretaceous (Maastrichtian) Western Interior Seaway of North America: evidence from Sr and O isotopes. Palaeogeogr. Palaeoclimatol. Palaeoecol. 191, 45–64. Coplen, T.B., Kendall, C., Hopple, J., 1983. Comparison of stable isotope reference samples. Nature 302, 236–238. Davis, T.T., Hooper, P.R., 1963. The determination of the calcite: aragonite ratio in mollusc shell by X-ray diffraction. Mineral. Mag. 33 (262), 608–612. England, T.D.J., Bustin, R.M., 1995. Guide to the geology of western Georgia basin, southwestern British Columbia. Geological Association of Canada, Mineralogical Association of Canada, Annual Meeting, May 17–19, 1995, Field Trip Guidebook B3 (59 pp.). Gale, A.S., Hancock, J.M., Kennedy, J.W., Petrizzo, M.R., Lees, J.A., Walaszczyk, I., Wray, D.S., 2008. An integrated study (geochemistry, stable oxygen and carbon isotopes, nannofossils, planktonic foraminifera, inoceramid bivalves, ammonites and crinoids) of the Waxahachie Dam spillway section, north Texas: a possible boundary stratotype for the base of the Campanian Stage. Cretac. Res. 29 (1), 131–167. Golovneva, L.B., German, A.B., 1998. Mechanism of floral evolution at the northwestern Kamchatka area (Penzhina region) during Late Cretaceous. Stratigraphiya i Geologicheskaya Korrelyatsiya, 6 (6), pp. 3–16 (in Russian). Grosman, E.L., Ku, T.-L., 1986. Oxygen and carbon isotope fractionation in biogenic aragonite: temperature effects. Chem. Geol. 59, 59–74. Haggart, J.W., 1990. New and revised ammonites from the Upper Cretaceous Nanaimo Group of British Columbia and Washington State. Contributions to Canadian Paleontology. Geological Survey of Canada, Bulletin, 396, pp. 181–221. Haggart, J.W., 1991. Biostratigraphy of the Upper Cretaceous Nanaimo Group, Gulf Islands, British Columbia. In: Smith, P.L. (Ed.), A Field Guide to the Paleontology of Southwestern Canada. Geological Association of Canada, Vancouver, British Columbia, pp. 222–257. Haggart, J.W., Ward, P.D., 1989. New Nanaimo Group ammonites (Cretaceous, Santonian– Campanian) from British Columbia and Washington State. J. Paleontol. 63, 218–227. Haggart, J.W., Meckert, D., Mustard, P.S., 2003. Coniacian strata of the Nanaimo Group, Courtenay region, Vancouver Island, British Columbia. Fifth British Columbia Paleontological Symposium, Abstracts, p. 12. Haggart, J.W., Ward, P.D., Orr, W., 2005. Turonian (Upper Cretaceous) lithostratigraphy and biochronology, southern Gulf Islands, British Columbia, and northern San Juan Islands, Washington State. Can. J. Earth Sci. 42 (11), 2001–2020. Haggart, J.W., Ward, P.D., Raub, T.D., Carter, E.S., Kirschvink, J.L., 2009. Molluscan biostratigraphy and paleomagnetism of Campanian strata, Queen Charlotte Islands, British Columbia: implications for Pacific coast North America biochronology. Cretac. Res. 30, 939–951. Haggart, J.W., Graham, R., Beard, G., 2011. Field Trip 2. The Upper Cretaceous of the Nanaimo–Courtenay region of Vancouver Island. In: Haggart, J.W., Smith, P.L. (Eds.), Field Trips to Harrison Lake and Vancouver Island, British Columbia. Canadian Paleontology Conference, Field Trip Guidebook No. 16. Geological Association of Canada and University of British Columbia, Vancouver, British Columbia, pp. 31–62. Hasegawa, T., Pratt, L.M., Maeda, H., Shigeta, Y., Okamoto, T., Kase, T., Uemura, K., 2003. Upper Cretaceous stable carbon isotope stratigraphy of terrestrial organic matter from Sakhalin, Russian Far East: a proxy for the isotopic composition of paleoatmospheric CO2. Palaeogeogr. Palaeoclimatol. Palaeoecol. 189, 97–115. Herman, A.B., 2011. Albskasya-paleotsenovaya flora Severnoj Patsifiki [Albian-Paleocene flora of the North Pacific region]. Trudy Geologicheskogo Instituta, 592, pp. 1–280 (in Russian). Herman, A.B., Lebedev, E.L., 1991. Stratigrafiya i flora melovykh otlozhenij severozapadnoj Kamchatki (Stratigraphy and flora of Cretaceous sediments of northwestern Kamchatka). Trudy Geologicheskogo Instituta Rossijskoy Akademii Nauk, 468, pp. 1–189 (in Russian).

Y.D. Zakharov et al. / Sedimentary Geology 295 (2013) 77–92 Hu, X., Scott, R.W., Cai, Y., Wang, C., Melinte-Dobrinescu, M.C., 2012. Cretaceous oceanic red beds (CORBs): different time scales and models of origin. Earth Sci. Rev. 115, 217–248. Huber, B.T., Hodel, D.A., Hamilton, C.P., 1995. Middle–Late Cretaceous climate of the southern high latitudes: stable isotopic evidence for minimal equator-to-pole thermal gradients. Geol. Soc. Am. Bull. 107 (10), 1154–1191. Huber, B.T., Norris, R.D., MacLeod, K.G., 2002. Deep-sea paleotemperature record of extreme warmth during the Cretaceous. Geology 30 (2), 123–126. Irving, E., 1985. Whence British Columbia? Nature 314, 673–674. Irving, E., Brandon, T., 1990. Paleomagnetism of the Flores volcanics, Vancouver Island, in place by Eocene time. Can. J. Earth Sci. 303, 263–299. Jarvis, I., Mabrouk, A., Moody, R.T.J., de Cabrera, S., 2002. Late Cretaceous (Campanian) carbon isotope events, sea-level change and correlation of the Tethys and Boreal realms. Palaeogeogr. Palaeoclimatol. Palaeoecol. 188, 215–248. Jarvis, I., Gale, A.S., Jenkyns, H., Pearce, M.A., 2006. Secular variation in Late Cretaceous carbon isotopes: a new δ13C carbonate reference curve for the Cenomanian–Campanian (99.6–70.6 Ma). Geol. Mag. 143 (5), 561–608. Jeletzky, J.A., 1970. Biochronology. In: Muller, J.E., Jeletzky, J.A. (Eds.), Geology of the Upper Cretaceous Nanaimo Group, Vancouver Island and Gulf Islands, British Columbia. Geological Survey of Canada Paper, 69–25, pp. 35–58. Jenkyns, H.C., 2010. Geochemistry of oceanic anoxic events. Geochem. Geophys. Geosyst. 11, Q03004. http://dx.doi.org/10.1029/2009GC002788. Jenkyns, H.C., Gale, A.S., Corfield, R.M., 1994. Carbon- and oxygen-isotope stratigraphy of the English Chalk and Italian Scaglia and its palaeoclimatic significance. Geol. Mag. 131 (1), 1–34. Jenkyns, H.C., Mutterlose, J., Sliter, W.V., 1995. Upper Cretaceous carbon- and oxygenisotope stratigraphy of deep-water sediments from the north-central Pacific (Site 869, flank of Pikinni-Wodejebato, Marshall Islands). Proc. Ocean Drill. Program Sci. Results 143, 105–108. Jenkyns, H.C., Forster, A., Schouten, S., Sinninghe Damsté, J.S., 2004. High temperatures in the Late Cretaceous Arctic Ocean. Nature 432, 888–892. Jones, D.L., Silberling, N.J., Hillhouse, J., 1977. Wrangellia — a displaced terrane in northwestern North America. Can. J. Earth Sci. 14, 2565–2577. Jung, C., Voigt, S., Friedrich, O., 2012. High-resolution carbon-isotope stratigraphy across the Campanian–Maastrichtian boundary at Shatsky Rise (tropical Pacific). Cretac. Res. 37, 177–185. Kodama, K., Maeda, H., Shigeta, Y., Kase, T., Takeuchi, T., 2000. Magnetostratigraphy of Upper Cretaceous strata in South Sakhalin, Russian Far East. Cretac. Res. 21, 469–478. Kodama, K., Maeda, H., Shigeta, Y., Kase, T., Takeuchi, T., 2002. Integrated biostratigraphy and magnetostratigraphy of the Upper Cretaceous System along the River Naiba in southern Sakhalin, Russia (in Japanese with English abstract). J. Geol. Soc. Jpn. 108, 366–384. Krassilov, V.A., 1979. Melovaya flora Sakhalina [Early Cretaceous flora of Sakhalin]. Nauka, Moscow (184 pp. (in Russian)). Krijgsman, W., Tauxe, L., 2006. E/I corrected paleolatitudes for the sedimentary rocks of the Baja British Columbia hypothesis. Earth Planet. Sci. Lett. 242, 205–216. Li, X., Jenkyns, H.C., Wang, C., Hu, X., Chen, X., Wei, Y., Huang, Y., Cui, J., 2006. Upper Cretaceous carbon- and oxygen-isotope stratigraphy of hemipelagic carbonate facies from southern Tibet, China. J. Geol. Soc. Lond. 163, 375–382. Markevich, V.S., 1995. Melovaya flora severa Vostochnoy Azii [Cretaceous flora of northern part of eastern Asia]. Dalnauka, Vladivostok (200 pp. (in Russian)). Markevich, V.S., Bugdaeva, E.B., 2001. Fossil floras of the Zeya–Bureya Basin. In: Bugdaeva, E.B. (Ed.), Flora i dinozavry na granitse mela i paleogena [Flora and dinosaurs at the Cretaceous-Paleogene boundary of the Zeya–Bureya Basin]. Dalnauka, Vladivostok, pp. 44–71. McGugan, A., 1979. Biostratigraphy and paleoecology of Upper Cretaceous (Campanian and Maestrichtian) foraminifera from the upper Lambert, Northumberland, and Spray formations, Gulf Islands, British Columbia, Canada. Can. J. Earth Sci. 16, 2263–2274. Meek, F.B., 1861. Descriptions of new Cretaceous fossils collected by the North-Western Boundary Commission, on Vancouver and Sucia islands. Proc. Acad. Nat. Sci. Phila. 13, 314–318. Melinte-Dobrinescu, M.C., Bojar, A.-V., 2010. Late Cretaceous carbon- and oxygen isotope stratigraphy, nannofossil events and paleoclimate fluctuations in the Hateg area (SW Romania). Palaeogeogr. Palaeoclimatol. Palaeoecol. 293, 295–305. Miller, K.G., Barrera, E., Olsson, R.K., Sugarman, P.J., Savin, S.M., 1999. Does ice drive early Maastrichtian eustasy? Geology 27 (9), 783–786. Miller, K.G., Sugarman, P.J., Browning, J.V., Kominz, M.A., Hemández, J.C., Olsson, R.K., Wright, J.D., Feigenson, M.D., Van Sikel, W., 2003. Late Cretaceous chronology of large, rapid sea-level changes: glacioeustasy during the greenhouse world. Geology 31 (7), 585–588. Monger, J.W.H., 2011. An overview of the tectonic history of the southern Coast Mountains, British Columbia. In: Haggart, J.W., Smith, P.L. (Eds.), Field Trips to Harrison Lake and Vancouver Island, British Columbia. Canadian Paleontology Conference, Field Trip Guidebook No. 16. Geological Association of Canada and University of British Columbia, Vancouver, British Columbia, pp. 1–11. Moriya, K., Nishi, H., Kawahata, H., Tanabe, K., Takayanagi, Y., 2003. Demersal habitat of Late Cretaceous ammonites: evidence from oxygen isotopes for the Campanian (Late Cretaceous) northwestern Pacific thermal structure. Geology 31 (2), 167–170. Muller, J.E., Jeletzky, J.A., 1970. Geology of the Upper Cretaceous Nanaimo Group, Vancouver Island and Gulf Islands, British Columbia. Geol. Surv. Can. Pap. 69–25 (77 pp.). Mustard, P.S., 1994. The Upper Cretaceous Nanaimo Group, Georgia Basin. In: Monger, J.W.H. (Ed.), Geological Hazards of the Vancouver region, Southwestern British Columbia. Geological Survey of Canada, Bulletin, 481, pp. 27–95. Mustard, P., Haggart, J., Katnick, D., Treptau, K., MacEachern, J., 2003. Sedimentology, paleontology, ichnology and sequence stratigraphy of the Upper Cretaceous Nanaimo

91

Group submarine fan deposits, Denman and Hornby islands, British Columbia. Geological Association of Canada–Mineralogical Association of Canada, Annual Meeting, Field Trip Guidebook, pp. 103–145. Naidin, D.P., 1984. Pozdnemelovaya epokha v istorii okeanov i kontinentov (statja 2) [Late Cretaceous time in oceans and continents history (paper 2)]. Izvestiya Vysshikh Uchebnykh Zavedenij, Geologiya i Razvedka, 3, pp. 3–14 (in Russian). Nascimento-Silva, M.V., Sial, A.N., Ferreira, V.P., Neumann, V.H., Barbosa, J.A., Pimentel, M.M., de Lacerda, L.D., 2013. Cretaceous–Paleogene transition at the Paraiba Basin, northeastern Brazil: carbon-isotope and mercury subsurface stratigraphies. J. S. Am. Earth Sci. (in press). Newberry, J.S., 1857. Report on the geology of the route of Williamson's survey in California and Oregon. U.S. Pac. Railr. Rep. Explor. 2, 5–68. Norris, R.D., Kroon, D., Huber, B.T., Erbacher, J., 2001. Cretaceous–Palaeogene ocean and climate change in the subtropical North Atlantic. In: Kron, D., Norris, R.D. (Eds.), Western North Atlantic Palaeogene and Cretaceous Palaeoceanography. Geological Society, London, Special Publications, 183, pp. 1–22. Pirrie, D., Marshall, J.D., 1990. High-paleolatitude Late Cretaceous paleotemperatures: new data from James Ross Island, Antarctica. Geology 18, 31–34. Pratt, L., Arthur, M.A., Dean, W.E., Scholle, P.A., 1993. Paleoceanographic cycles and events during the Late Cretaceous in the Western Interior Seaway of North America. In: Caldwell, W.G.E., Kaufman, E.G. (Eds.), Cretaceous Evolution of the Western Interior Basin of North America. Geological Association of Canada, Special Papers, 39, pp. 333–353. Price, C.D., Hart, M.B., 2002. Isotopic evidence for Early to mid-Cretaceous ocean temperature variability. Mar. Micropaleontol. 46, 45–58. Saltzman, M.R., Thomas, E., 2012. Carbon isotope stratigraphy. In: Gradstein, F.M., Ogg, J.G., Schmitz, M., Ogg, G. (Eds.), The Geologic Time Scale, pp. 207–232. http:// dx.doi.org/10.1016/B978-0-444-59425-9.00011-1. Schönfeld, J., Sirocko, E., Jorgensen, N.O., 1991. Oxygen isotope composition of Upper Cretaceous chalk at Lägerdorf (NW Germany): its original environmental significance and palaeotemperature interpretation. Cretac. Res. 12, 27–46. Schovsbo, N.H., 2007. High resolution carbon-isotope curve for the Boreal late Campanian– Maastrichtian, Stevns Klint, Denmark. Geophys. Res. Abstr. 9, 01592 (SRef-ID:16077962/gra/EEU2007-1-01592). Shackleton, N.J., Kennett, J.P., 1975. Paleotemperature history of the Cenozoic and the initiation of Antarctic glaciation: oxygen and carbon isotope analyses in DSDP Sites 277, 279, and 281. In: Kennett, J.P., Houtz, R.E., et al. (Eds.), Initial Reports of the Deep Sea Drilling Project, vol. 29. U.S. Government Printing Office, Washington, pp. 743–756. Smyshlyaeva, O.P., Zakharov, Y.D., Shigeta, Y., Tanabe, K., Ignatiev, A.V., Velivetskaya, T.A., Popov, A.M., Afanasyeva, T.B., Moriya, K., 2002. Optimal temperatures of growth in Campanian ammonoids of Sakhaline (Krilon) and Hokkaido: oxygen and carbon isotopic data. Cretaceous Continental Margin of East Asia: Stratigraphy, Sedimentation, and Tectonics. The 4th International Symposium of IGCP 434, Khabarovsk, September 2002, Abstracts, pp. 97–98. Spicer, R.A., Herman, A.B., 2010. The Late Cretaceous environment of the Arctic: a quantitative reassessment based on plant fossils. Palaeogeogr. Palaeoclimatol. Palaeoecol. 295 (3/4), 423–442. Stevenson, G.R., Clayton, R.N., 1971. Oxygen isotope studies on Jurassic and Cretaceous belemnites from New Zealand and their biogeographic significance. N. Z. J. Geol. Geophys. 14, 829–897. Takashima, R., Nishi, H., Huber, B., Leckie, R.M., 2006. Greenhouse world and the Mesozoic ocean. Oceanography 19 (4), 64–74. Takashima, R., Nishi, H., Yamanaka, T., Hayashi, K., Obuse, A., Tomosugi, T., Deguchi, N., Mochizuki, S., 2010. High-resolution terrestrial carbon isotope and planktic foraminiferal records of the Upper Cenomanian to the Lower Campanian in the Northwest Pacific. Earth Planet. Sci. Lett. 289, 570–582. Thibault, N., Harlou, R., Schovsbo, N., Schiøler, P., Minoletti, F., Galbrun, B., Lauridsen, B.W., Sheldon, E., Stemmerik, L., Surlyk, F., 2012. Upper Campanian–Maastrichtian nannofossil biostratigraphy and high-resolution carbon-isotope stratigraphy of the Danish Basin: towards a standard δ13C curve for the Boreal Realm. Cretac. Res. 33, 72–90. Tsujita, C.J., Westermann, G.E.G., 1998. Ammonoid habitats and habits in the Western Interior Seaway: a case study from the Upper Cretaceous Bearpaw Formation of southern Alberta, Canada. Palaeogeogr. Palaeoclimatol. Palaeoecol. 144, 135–160. Umhoefer, P.J., 1987. Northward translation of “Baja British Columbia” along the Late Cretaceous to Paleocene margin of western North America. Tectonics 6, 377–394. Usher, J.L., 1952. Ammonite faunas of the Upper Cretaceous rocks of Vancouver Island, British Columbia. Geol. Surv. Can. Bull. 21, 1–182. Wagreich, M., 2009. Coniacian–Santonian oceanic red beds and their link to Oceanic Anoxic Event 3. In: Hu, X., Wang, Ch., Scott, R.W., Wagreich, M., Jansa, L. (Eds.), Cretaceous Oceanic Red Beds; Stratigraphy, Composition, Origins, and Paleoceanographic and Paleoclimatic Significance. SEPM (Society for Sedimentary Geology), Special Publication, 91, pp. 235–242. Wagreich, M., 2012. “OAE 3” — regional Atlantic organic carbon burial during the Coniacian–Santonian. Clim. Past 8, 1447–1455. Wang, Ch., Hu, X., Sarti, M., Scott, R.W., Li, X., 2005. Upper Cretaceous oceanic red beds in southern Tibet: a major change from anoxic to oxic, deep-sea environments. Cretac. Res. 26, 21–32. Wang, Ch., Hu, X., Huang, Y., Scott, R.W., Wagreich, M., 2009. Overview of Cretaceous oceanic red beds (CORBs): a window on global oceanic and climate change. In: Hu, X., Wang, Ch., Scott, R.W., Wagreich, M., Jansa, L. (Eds.), Cretaceous Oceanic Red Beds; Stratigraphy, Composition, Origins, and Paleoceanographic and Paleoclimatic Significance. SEPM (Society for Sedimentary Geology), Special Publication, 91, pp. 13–33. Ward, P.D., 1978a. Revisions to the stratigraphy and biochronology of the Upper Cretaceous Nanaimo Group, British Columbia and Washington State. Can. J. Earth Sci. 15 (3), 405–423.

92

Y.D. Zakharov et al. / Sedimentary Geology 295 (2013) 77–92

Ward, P.D., 1978b. Baculitids from the Santonian–Maestrichtian Nanaimo Group, British Columbia, Canada and Washington State, USA. J. Paleontol. 52 (5), 1143–1154 (2 pls). Ward, P.D., Hurtado, J.M., Kirschvink, J.L., Verosub, K.L., 1997. Measurements of the Cretaceous paleolatitude of Vancouver Island: consistent with the Baja-British Columbia hypothesis. Science 277, 1642–1645. Ward, P.D., Haggart, J.W., Mitchell, R., Kirschvink, J.L., Tobin, T., 2012. Integration of macrofossil biostratigraphy and magnetostratigraphy for the Pacific coast Upper Cretaceous (Campanian–Maastrichtian) of North America and implications for correlation with the Western Interior and Tethys. Geol. Soc. Am. Bull. 124 (5/6), 957–974. Weissert, H., 2012. Early Cretaceous carbon cycle, climate and oceanography — volcanic, orbital and tectonic forcings. Proceedings of the 34th International Geological Congress. ISBN: 978-0-646-57800-2, p. 3705 (Brisbane, Australia). Weissert, H., Erba, E., 2004. Volcanism, CO2 and palaeoclimate: a Late Jurassic–Early Cretaceous carbon and oxygen isotope record. J. Geol. Soc. Lond. 161, 1–8. White, C.A., 1889. On invertebrate fossils from the Pacific coast. U.S. Geol. Surv. Bull. 51, 433–532. Whiteaves, J.F., 1879. On the fossils of the Cretaceous rocks of Vancouver and adjacent islands in the Strait of Georgia. Geol. Surv. Can. Mesozoic Fossils 1 (2), 93–190. Whiteaves, J.F., 1895. On some fossils from the Nanaimo Group of the Vancouver Cretaceous. Trans. R. Soc. Can. 1 (4), 119–133. Whiteaves, J.F., 1901. Note on a supposed new species of Lytoceras from the Cretaceous rocks at Denman Island, in the Strait of Georgia. Ott. Nat. 15, 31–32. Whiteaves, J.F., 1903. On some additional fossils from the Vancouver Cretaceous, with a revised list of the species therefrom. Geol. Surv. Can. Mesozoic Fossils 1 (5), 309–416. Zakharov, Y.D., Naidin, D.P., Teiss, R.V., 1975. Izotopnyj sostav kisloroda rakovin rannetriasovykh golovonogikh Arkticheskoy Sibiri i solyonost borealnykh basseynov v nachale mezozoya [Oxygen isotope composition of Early Triassic cepalopod shells of Arctic Siberia and salinity of the boreal basins at the beginning of Mesozoic]. Izvestiya Akad. Nauk SSSR, Ser. Geol. 4, 101–113 (in Russian). Zakharov, Y.D., Smyshlyaeva, O.P., Shigeta, Y., Ignatiev, A.V., Velivetskaya, T.A., Popov, A.M., Afanasyeva, T.B., Moriya, K., 2003. Optimalnye temperaqtury rosta kampanskikh ammonoidey Sakhalina i Khokkaido po izotopnym dannym [Optimal temperatures of growth in Campanian ammonites of Sakhalin and Hokkaido]. Byulleten Moskovskogo Obschestva Ispytatelei Prirody. Otd. Geol. 78, 46–56 (in Russian).

Zakharov, Y.D., Smyshlyaeva, O.P., Tanabe, K., Shigeta, Y., Maeda, H., Ignatiev, A.V., Velivetskaya, T.A., Afanasyeva, T.B., Popov, A.M., Golozubov, V.V., Kolyada, A.A., Cherbadzhi, A.K., Moriya, K., 2005. Seasonal temperature fluctuations in the high northern latitudes during the Cretaceous Period: isotopic evidence from Albian and Coniacian shallow-water invertebrates of the Talovka River Basin, Koryak Upland, Russian Far East. Cretac. Res. 26, 113–132. Zakharov, Y.D., Smyshlyaeva, O.P., Popov, A.M., Shigeta, Y., 2006a. Izotopnyj Sostav Pozdnemezozoiskikh Organogennukh karbonatovDalnego Vostoka (Stabilnye Izotopy kisloroda i Ugleroda, Osnovnye Paleoklimaticheskiye Sobytiya i ikh Globalnaya Korrelyatsiya) [Isotopic composition of Late Mesozoic Organogenic Carbonates of Far East (Oxygen and Carbon Stable Isotopes, Major Palaeoclimatic Events and their Global Correlation)]. Dalnauka, Vladivostok (204 pp. (in Russian)). Zakharov, Y.D., Shigeta, Y., Smyshlyaeva, O.P., Popov, A.M., Ignatiev, A.V., 2006b. Relationship between δ13C and δ18O values of the recent Nautilus and brachiopod shells in the wild and the problem of reconstruction of fossil cephalopod habitat. Geosci. J. 10 (30), 331–345. Zakharov, Y.D., Shigeta, Y., Tanabe, T.B., Iba, Y., Smyshlyaeva, O.P., Sokolova, E.A., Popov, A.M., Velivetskaya, T.A., Afanasyeva, T.B., 2007. Campanian climatic change: isotopic evidence from Far East, North America, North Atlantic and Western Europe. Acta Geol. Sin. 81 (6), 1049–1069. Zakharov, Y.D., Shigeta, Y., Smyshlyaeva, O.P., Popov, A.M., Velivetskaya, T.A., Afanasyeva, T.B., 2011. Cretaceous climatic oscillations in the Bering area, Alaska and Koryak Upland: isotope and palaeontological evidence. Sediment. Geol. 235, 122–131. Zakharov, Y.D., Melnikov, M.E., Popov, A.M., Pletnev, S.P., Khudik, V.D., Punina, T.A., 2012. Cephalopod and brachiopod fossils from the Pacific: evidence from the Upper Cretaceous of the Magellan Seamounts. Geobios 45, 145–156. Zakharov, Y.D., Baraboshkin, E.Y., Weissert, H., Michailova, I.A., 2013. Late Barremian– early Aptian climate of the northern middle latitude: stable isotope evidence from bivalve and cephalopod molluscs of the Russian Platform. Cretac. Res. 44, 183–201. Zakharov, Y.D., Tanabe, K., Safronov, P.P., Smyshlyaeva, O.P., 2013. New data on microstructure and isotopic composition of some cephalopods from the Upper Cretaceous of North America and Europe: significance for oxygen isotope palaeotemperature measurements. In: Berning, B. (Ed.), Cephalopods: Present and Past (in press).