22 Chignecto Bay Member channel bodies: Two major channel bodies are present in the lower, redbed-dominated Chignecto Bay Member of the Boss Point Formation (Fig. 7). These bodies occur at 23.6 and 56.0 m and are 8.9 and 4.6 m thick, respectively. True width:thickness values could not be calculated for these channel bodies because they are incompletely exposed and the western (seaward) channel margins could not be confidently located on air photos. Channels are bounded by fifth-order surfaces that are flat to concave-up near channel margins.

23 Channel bodies are composed of fine-grained, reddish sandstone that contrasts with the greyish-yellow color of overlying channel bodies. Despite color differences caused by hematite staining, these bodies are composed of lithic arenite sandstone comparable to that in the overlying multistorey bodies. Major internal erosion surfaces are absent and these single-storey channel bodies are filled with stacked sets of cross-beds and ripple cross-laminae (Fig. 7a). Average paleoflow is to the north and northeast (353° and 049°, respectively), although measurements from the lower body are variable and derived from ripple cross-laminae. A poorly-preserved invertebrate trace fossil, Diplichnites cuithensis, was present on a bedding plane at 56 m, near the top of the channel body (Fig. 7b).

24 Ward Point Member channel bodies: Fourteen discrete multistorey bodies are present in the Ward Point Member (Fig. 8). Fuller accounts of the sedimentology of these bodies are provided by Browne and Plint (1994) and Ielpi et al. (2014). Thicknesses range from 4.0 to 126.9 m (44 m average), with the maximum values near the middle of this interval. Multistorey channel bodies are bounded by sixth- or seventh-order bounding surfaces that locally fill valleys with up to 35 m of erosional relief (Plint and Browne 1994). The basal surfaces can be correlated regionally (Plint and Browne 1994) and these composite channel bodies have minimum W:T values in excess of 300 (Ielpi et al. 2014). Internally, these channel bodies have a complex architecture consisting of cross-cutting fifth- and sixth-order erosion surfaces developed at the base of individual channel elements. Individual storeys range from 2 to 10 m thick (5.5 m average). Where fully preserved, individual channel elements range from 1 to 6 m thick (3.5 m average), 5 to 90 m wide (25 m avg.), and have average W:T values of 7.8 (Ielpi et al. 2014).

25 Multistorey channel bodies are largely composed of medium- to coarse-grained sandstone organized into trough cross-beds (Fig. 8a). Climbing-ripple cross-laminae and horizontal laminae are abundant in the upper portion of many channel bodies, with some partially preserved antidune bedforms (Allen et al. 2013). Average paleoflow for these 14 channel bodies is 119° (ranging from 44° to 161°). These lithofacies comprise composite sandy bars and bedforms, laminated sand sheets, downstream-accretion and minor lateral-accretion macroforms. Subordinate cross-bedded gravel barforms up to 2.0 m thick are present locally (Fig. 8b). Allen et al. (2013) noted that upper flow regime sand sheets become increasingly common near the top of the member and display Froude transcritical and supercritical structures. Conglomeratic lags composed of intraformational clasts (mud chips, concentrically laminated caliche nodules, and siderite nodules) with subordinate amounts of extraformational material (fragments of igneous, metamorphic, and sedimentary rock) commonly line erosional surfaces in multistorey channel bodies (Figs. 8c–e). Fragments of blocky, horizontally laminated limestone are relatively common between 91.5 and 310 m (Fig. 8c); an isolated occurrence is present at ~794 m. The cliff exposure at 919 to 924 m consists of red and green mudrocks that contain large rotated slump blocks and have been intensely affected by soft-sediment deformation (Fig. 8g); this mudrock unit pinches out in the intertidal zone. An abraded gastropod (tentatively identified as Strobeus by P. Wagner, personal communication, 2013) was recovered from a limestone-rich lag at ~124 m (Fig. 8d).

26 Transported plant debris in multistorey channels consists largely of logs derived from cordaitalean gymnosperms (Fig. 8h) with minor contributions from lycopsids (Lepidodendron and Lepidophloios), sphenopsids (Calamites), and possible tree ferns and pteridosperms (Ielpi et al. 2014). Falcon-Lang and Scott (2000) documented the presence of charred coniferopsid wood of Dadoxylon-type and noted that permineralized logs consist of pycnoxylic coniferopsid wood that lacked growth rings. Striking examples of large coalified or permineralized cordaitalean logs, many with intact root masses, are particularly common in channel bodies between 110 and 910 m in the section. Channel lags, small channel fills, and barforms with abundant cordaitalean logs make up ~18% of the channel fill in multistorey channel bodies (Ielpi et al. 2014). At a few levels, upright cordaitalean trees with preserved roots are encased in channel deposits.

27 North Reef Member channel bodies: The North Reef (1051.8 m) and South Reef (1125 m) channel bodies are the only major fluvial sandstones in the North Reef Member. They extend the entire width of the outcrop belt and lack exposed channel margins. The North Reef channel body is 10.5 m thick and has a minimum W:T value of 12; the South Reef body is 25.0 m thick and has a minimum W:T value of 9.5. The basal fifth-order erosion surfaces are subhorizontal and have <3 m of erosional relief. The North Reef channel body has two intraformational conglomerate-lined erosional surfaces (fifth-order) that split it into three 5-m-thick storeys. Although the South Reef channel body lacks obvious intraformational lags and is less well exposed, it does appear to have laterally extensive erosional surfaces that split it into at least three storeys (Fielding et al. 2011). The South Reef channel body appears to have east-dipping inclined beds that are cut by reactivation surfaces that extend for tens of metres laterally (Fielding et al. 2011).

28 These channel bodies are largely filled with stacked cosets of trough cross-beds that are bounded by third- and fourth-order surfaces (Fig. 9). Average paleoflow is to the east (84° and 118°, respectively). Low-angle, convex-upward upper flow regime structures are present at multiple levels in both bodies (Fielding et al. 2011; Allen et al. 2013). Individual sets are up to 2 m thick near the base of the bodies and thin to 0.5 m thick near the top. The upper 1–3 m of the channel fill is composed of ripple cross-laminated, horizontally laminated, and/or low-angle cross-laminated sandstone. Additional details of internal architecture are limited because both bodies were extensively quarried in the 1700s and 1800s (Boon and Calder 2007; Falcon-Lang 2009) and crop out only as low-relief, mud-covered mounds in the intertidal zone. Falcon-Lang and Scott (2000) and Falcon- Lang (2000) reported charred coniferopsid wood fragments of Dadoxylon-type from channel bodies from this interval.

29 Chignecto Bay Member channel bodies: The two channel bodies in the Chignecto Bay Member are single-storey deposits whose thickness (6.8 m average) roughly approximates the depth of the active channel. The northerly paleoflow recorded by these two bodies is similar to that of the uppermost Claremont Formation (Hamblin 2001) and, more broadly, the Mabou Group (McLeod 2010; Allen et al. 2013), but nearly perpendicular to the southeasterly trend recorded by the overlying multistorey channel bodies of the Ward Point Member. The northerly trend suggests a source area in the Cobequid Highlands (Ryan and Boehner 1994), short-lived tectonic tilting of the basin floor (Plint and Browne 1994), an origin as tributary systems south of the trunk drainage (Gibling et al. 1992), or some combination of these factors.

30 The sandstone fill is organized into cross-beds and ripple cross-laminae that formed part of downstream accretionary or sandy barforms. Although limited exposure makes more detailed interpretation of fluvial architecture and form difficult, they could represent anastomosed or ephemeral sand-bed rivers (Miall 1996). In terms of style, these deposits likely represent a transition from the arid, strongly seasonal fluvial deposits of the Mabou Group to the perennial braided fluvial deposits of the lower Boss Point Formation (Allen et al. 2013). The presence of Diplichnites (inferred to be the trackway of the large millipede Arthropleura; Briggs et al. 1984) near the top of the channel body at 56 m suggests that the low-lying abandoned channel may have served as a waterhole in an otherwise moisture-stressed environment (sensu Falcon-Lang et al. 2004).

31 Ward Point Member channel bodies: Channel bodies in the Ward Point Member are broad sheets with an erosion-dominated multistorey architecture; individual storeys and abandoned channel fills are rarely preserved. They can be correlated regionally and mark phases of widespread fluvial deposition in the Cumberland Basin (Plint and Browne 1994; Ielpi et al. 2014). Active channels within the system averaged 5.5 m deep and 25 m wide (Ielpi et al. 2014). Although the southeasterly paleoflow recorded by these bodies is comparable to many of the overlying units and consistent with a source in the Caledonia Highlands of New Brunswick or in the Appalachians (Gibling et al. 1992), it is also broadly parallel to the trend of the salt-cored Minudie Anticline and may record paleoflow deflection by the diapir.

32 Browne and Plint (1994) interpreted these channel bodies as the deposits of braided rivers that were filled with sinuous-crested dunes and confined by stable, vegetated banks. This interpretation was confirmed for the lower part of the member by Allen et al. (2013), who interpreted the lack of upper flow regime structures as a hallmark of perennial channels in a relatively humid climate. Overall, the type of deep, perennial braided river (Miall 2006) envisioned by Allen et al. is comparable to the modern South Saskatchewan River (Cant and Walker 1978) and the Brahmaputra River (Bristow 1993). Comparable ancient deposits include the Kayenta Formation (Miall 1988) and the Westwater Canyon Member of the Morrison Formation (Godin 1991). Allen et al. (2013) noted that upper flow regime structures become increasingly more prominent in channel bodies at higher levels in the member, in accord with an increased degree of seasonality.

33 The interpretation of multistorey channel bodies in this part of the Boss Point Formation was further refined by Ielpi et al. (2014), who documented floodplains forested by mature cordaitaleans, vegetated islands within the fluvial system as indicated by the presence of rooted channel deposits with upright trees, and numerous accumulations of woody debris at the base of channel storeys or coring large barforms. Given the profound influence of woody plant debris, Ielpi et al. interpreted the multistorey channel bodies as the deposits of anabranching, island-braided sandbed rivers, with morphodynamics similar to those described for the modern Platte River (Horn et al. 2012), the Tagliamento River and other island-braided, wandering, or sandy anabranching systems (Gurnell et al. 2001, Tockner et al. 2003).

34 Carbonate is present in lags as rounded, concentrically-laminated caliche nodules and as fragments of blocky, laminated limestone. Although the limestone fragments could be intraformational material derived from thin limestones similar to those in the Chignecto Bay Member (see below), a Windsor Group provenance is more likely given the large amount of material, the presence of a large, reworked marine(?) gastropod in a carbonate-rich lag at ~124 m, proximity to the Windsor-cored Minudie Anticline, and the similarity of the Boss Point fragments to Windsor clasts described from the underlying Mabou Group (Hamblin 2001).

35 North Reef Member channel bodies: The uppermost major channel bodies in the North Reef Member are succession-dominated multistorey bodies. These channel bodies were not included in the regional study of Plint and Browne (1994) and their lateral extent is unclear. They may have had an original width of at least a few kilometres and were probably narrow to broad sheets with a distribution comparable to multistorey bodies in the underlying members. Individual storeys are 5–8 m thick and provide a rough approximation of channel depth, an interpretation supported by Fielding et al.’s (2011) hydrodynamic calculations, which suggested bedforms developed in water depths of 4 m. Fielding et al.(2011) and Allen et al. (2013) interpreted the abundance of upper flow regime structures in these bodies as recording a transition from a (sub-)humid to a semi-arid climate with more pronounced seasonality and variability in discharge.

36 Five occurrences of the open water facies association are present in the Ward Point Member (Fig. 10). Open water intervals range from 1.5 to 9.1 m thick (average 4.7 m) with a cumulative thickness of 23.4 m (2% of formation thickness; ~8% of the exposed, non-channelized facies). The open water facies association occurs atop multistorey channel bodies at 101.7 m (Fig. 10a) and 257.8 m and atop the poorly drained facies association at 609.1 m, 788.1 m, and 950.2 m. It is overlain by multistorey channel bodies at 266.9 m and 610.6 m, the poorly drained facies association at 783 m, and the well-drained facies association at 109.8 m and 951.7 m. A sixth occurrence of open water facies occurs interbedded with poorly drained deposits is present between 853.9–875.6 m. Contacts with over- and underlying facies associations range from sharp (generally in association with channel bodies) to gradational over a few tens of centimetres to a few metres.

37 Greyish-black to grey mudrock devoid of carbonate is the most abundant lithofacies in the open water facies association (Figs. 10b–c). Most intervals are laminated and weather to platy fragments. Flattened siderite nodules concentrated along bedding planes are common. The interval between 854 and 875.5 m is composed of interbedded, laminated grey mudrocks and blocky greenish-grey mudrocks, both of which appear to have been overprinted by pedogenic processes. Fossils are relatively rare within mudrocks, although unidentifiable plant fragments (104.5 m, 861 m) and ostracods (104.5) are present locally. Mudrocks may become blockier and contain carbonized roots within a few tens of centimetres of contacts with over- and underlying facies associations (109.5 m, 257.8 m, 266.9 m, 609.1 m). A Stigmaria (lycopsid rhizomorph) with a pyritized rind, which has a δ³⁴S value of 31‰, was recovered from poorly exposed mudrocks in the intertidal zone at ~949 m (Wagner et al. 2013).

38 In addition to laminated mudrocks, the two uppermost open water occurrences (788.2–791.9 m and 950.2–951.7 m) have discrete ~1-m-thick intervals composed of subequal interbeds of limestone and dark-grey shale; individual interbeds range from 0.05–0.27 m thick (Fig. 10b). Mudrocks within these interbedded packages are similar to those described above. Limestones range from light-grey, well-cemented wackestones that stand in prominent relief to greyish-black, organic-rich packstones with a more fissile and papery weathering pattern. Ostracods are present in both types of limestone; the organic-rich packstones have abundant bivalves that partially define bedding planes. Vasey (1984) assigned bivalves of the Boss Point Formation to the genera Carbonicola and Curvirimula. Grey et al. (2012) reported the ostracod Velatomorpha altilis from open water deposits near the top of the Boss Point Formation.

39 A fissile calcareous black shale with abundant bivalves and ostracods is present at 106.9 m. A single, <0.01-m-thick discontinuous coal is present within greyish mudrocks at 610.2 m. The coal sits atop 0.25 m of blocky dark-grey mudrock; no roots were observed.

40 The open water facies association was deposited in calm bodies of water that ranged from fresh to brackish and was generally of sufficient depth to limit plant growth. We consider only intervals with direct evidence of deposition in a relatively long-lived standing body of water to be part of this facies association. This approach contrasts with that of Plint and Browne (1994) and Browne and Plint (1994) who included all relatively fine-grained, non-channelized deposits in their lacustrine facies.

41 We agree with Plint and Browne’s (1994) interpretation that dark-colored laminated mudrocks were deposited in a reducing, organic-rich environment where mud accumulated by suspension deposition. Browne and Kingston (1993) analyzed sphaerosiderite from mudrocks at ~609 m in our section and determined that the body of water must have experienced reducing, stagnant conditions and contained a sufficiently low amount of dissolved sulfate to be considered of freshwater origin.

42 The significance of a thin coal within the open water facies association depends on its origin: given its discontinuous nature and lack of underlying roots, it likely represents organic material (vitrain) resulting from coalification of a transported lycopsid log rather than an in-situ histosol (peat). Plint and Browne (1994) described upright lycopsids entombed in grey platy “lacustrine” mudstones. Unlike mires which have a peat substrate, these clastic swamps developed atop a mineral soil (Gastaldo 1987; Demko and Gastaldo 1992).

43 The ostracod- and bivalve-bearing limestones, part of Plint and Browne’s (1994) abandonment facies, record deposition of carbonate in an environment with very little clastic input. These limestones have striking lithologic and faunal similarities to the “bituminous limestones” of the Joggins Formation (Davies and Gibling 2003; Davies et al. 2005). The low diversity and high abundance of ostracod and bivalve fossils suggests oligotrophic conditions determined by oxygen levels, salinity, or other types of environmental stress (sensu Ielpi 2013). Sulfur isotope values suggest that the pyritized Stigmaria just below the ostracod-bearing open water interval at 950 m most likely formed in a closed system that had considerable amounts of dissolved sulfate — conditions suggestive of brackish water (Wagner et al. 2013). Although a growing body of evidence suggests a marginal marine setting for these deposits (Skilliter 2001; Falcon-Lang 2005; Tibert and Dewey 2006; Grey et al. 2011; Bashforth et al. 2014), much uncertainty exists and further work is needed to fully understand their paleoenvironmental significance (Calder 1998; Falcon-Lang et al. 2006).

44 The terms “lake”, “bay”, or “lagoon” may be applicable to these standing bodies of water depending on the water chemistry at the time of deposition. Regardless of the exact terminology used, they clearly suggest low-energy bodies of water where suspension deposition of mud and/or precipitation of carbonate were the dominant processes. Unlike open-water intervals in the overlying Joggins Formation, the transition to floodplain facies is not marked by a wave- or fluvial-dominated package of sharp-based sandstones (Davies and Gibling 2003). Rather, the bodies of water in the Ward Point Member appear to record a gradual shallowing and a transition to muddy floodplains marked by an increase in blockiness and abundance of carbonized roots. Overall, these bodies of water may have had some sedimentological and ecological similarities to Lake Pontchartrain (Manheim and Hayes 2002). In terms of ancient analogs, these deposits may represent a more humid climate version of the Oligocene deposits of the Calaf Basin (Cabrera and Saez 1987).

45 Seven occurrences of the poorly drained facies association are present in the Ward Point Member between 168 and 950 m in the measured section (Fig. 11). Individual intervals range from 2.0 to 15 m thick (average 7.7 m) with a cumulative thickness of 53.8 m (5% of formation thickness; ~18% of the exposed non-channel facies). Occurrences of poorly drained strata are present atop multistorey channel bodies (168.3 m, 415.8 m, 607.1 m, 780.8 m, and 935.1 m), the open water facies association (791.9), and a covered interval (749.2 m). Contacts with over- and underlying facies associations range from sharp to gradational over a few tens of centimetres (Fig. 11a). A complexly interbedded package of open water and poorly drained deposits is present at 854.0–875.5 m; contacts between constituent facies were overprinted by pedogenic processes and this interval could not be confidently subdivided.

46 Green and grey mudrocks are the most common lithology in the poorly drained facies association (Fig. 11b). Beds are up to 2 m thick and have sharp to gradational contacts with other lithologies. Internally, mudrocks range from platy to blocky with little or no obvious internal stratification. Many contain scattered siderite nodules and vertically oriented carbonized roots. Stigmaria occur in association with mineral paleosols and beneath organic-rich horizons. Plint and Browne (1994) documented Stigmaria at positions equivalent to ~169 m, 754 m, and 854‒874 m and in-situ lycopsid trunks at ~869 m and ~872 m.

47 Dark-grey to greyish-black organic-rich horizons up to 0.02 m thick are common within mudrocks of the poorly drained facies association. They commonly overlie intervals with a blocky fabric, abundant carbonized roots, and limonite staining.

48 Rare <2-m-thick zones of reddish brown mudrock are present locally (171.5 m, 752.5 m, 801.5 m, 948.5 m, and several horizons between 851 and 875 m). Reddened intervals typically have gradational contacts with over- and underlying greenish-grey mudrocks and may contain siderite nodules, carbonized roots, and diffuse organic-rich horizons. A ~1-m-thick blocky red mudrock at 171.5 m contains calcareous nodules. This unit has a gradational contact with underlying greenish-grey mudrocks and a sharp contact with overlying greenish-grey mudrocks with carbonized roots.

49 Two 0.06-m-thick coals are present within poorly drained strata at 174.5 m and the interbedded open water/ poorly drained interval at 870.4 m. The lower coal has several thin shale partings and sits atop a blocky green- grey mudrock with carbonized roots and limonite staining. The upper coal occurs above a blocky greenish-grey shale with siderite rhizoconcretions and below a laminated grey shale. The upper surface of the coal has numerous flattened, coalified lycopsid logs.

50 Sheet sandstones become particularly abundant above 609 m. Together with minor channel bodies, they make up <10% of the thickness of poorly drained occurrences below 780.8 m and up to 60% of their thickness above this level. Individual beds are generally <1 m thick and have sharp contacts with over- and underlying mudrocks. Most sandstones contain ripple cross-laminae (in places climbing ripples) and flattened siderite nodules; horizontal lamination and cross-bedding are present locally. Minor channel sandstones occur locally in association with sandstone-rich intervals. Many sandstones are internally massive; vertical carbonized roots and plant fragments are common. Radiating carbonized roots associated with Stigmaria are present at 608.9 m, 856.3 m, 861.6 m, and 873.9 m. Although lycopsid trunks were not observed during this study, in-situ examples were reported from this section by Plint and Browne (1994) and rare, transported Lepidodendron and Lepidophloios were noted in the channel sandstones described above (Ielpi et al. 2014). Entombed Calamites are common within sandstones above 609 m (Fig. 11c).

51 The poorly drained facies association was deposited in low-lying swampy areas saturated with oxygen-depleted water. Mudrocks record suspension deposition on the floodplain; blocky textures and roots within these beds record the development of immature hydromorphic paleosols and colonization by vegetation. Localized reddish brown mudrocks within poorly drained deposits record relatively modest exposure and drainage, likely due to seasonal lowering of the water table that allowed for oxidation of the substrate. Organic-rich horizons and thin coals represent histic epipedons and short-lived histosols developed in localized, incipient peat-forming or clastic wetlands (Retallack 2008). Although Plint and Browne (1994) did not observe coals in the type section, they documented examples up to 0.7 m thick in other exposures, indicating that longer-lived mires may have existed elsewhere on the Boss Point floodplain.

52 Sheet sandstones represent crevasse-splay deposits formed when floodplain channels overtopped their banks and deposited a veneer of sand across the floodplain. Minor channel bodies within sheet sandstones represent either crevasse-splay feeder channels formed as the main channel was breached, or distributary channels formed where fluvial systems debouched into wetlands. Sandstone-rich intervals with numerous closely spaced interbeds of mudrock may represent avulsion deposits formed in close proximity to the major channels (Kraus and Wells 1999).

53 Additional information about the poorly drained facies association was provided by Ielpi et al. (2014), who documented the general composition of plant material, described several occurrences of in-situ vegetation, and placed this paleobotanical information into an environmental context. Sandstone-rich crevasse-splay deposits were occupied by Calamites, a horsetail-like plant that was well adapted to the colonization of disturbance-prone environments (Gastaldo 1992; Pfefferkorn et al. 2001; Calder et al. 2006). Stigmarian rhizomorphs within clastic paleosols and beneath organic-rich horizons record the former presence of lycopsids in wetland environments, both in clastic swamps and incipient peat-forming mires on the floodplain. The two fossil genera of lycopsids (Lepidodendron and Lepidophloios) had an ecological preference for the most waterlogged and stable (i.e., undisturbed) parts of peat-forming mires or clastic swamps (Phillips and DiMichele 1992; DiMichele and Phillips 1994). Likewise, the wetlands that supported these spore-bearing lycopsids must have been sufficiently persistent for germination and growth of these trees (DiMichele and Phillips 1994).

54 Eight occurrences of the redbed-dominated well drained facies association are present (Fig. 12). Well-drained deposits are the only non-channelized deposits in the Chignecto Bay and North Reef members. Individual occurrences range from 6.2 to 89.5 m thick and the cumulative thickness is 193 m (17% of formation thickness; 66% of exposed, non-channelized facies). Although thick covered intervals are present near the base and top of the section, shifting exposures of mudrock in the intertidal zone appear to be composed almost entirely of redbeds. It is probable that much of the ~160 m of covered section consists of well-drained deposits. In the Ward Point Member, strata of the well drained facies association occur atop the open water facies association (109.8 m and 951.7 m), the poorly drained facies association (176.3 m, 875.5 m), and multistorey channel bodies (393.8 m and 473.8 m). Contacts with other facies associations are generally sharp, although they may be interbedded or gradational over a few tens of centimetres.

55 Reddish brown mudrocks (Munsell rock colors 10R 3/4 to 10R 4/6) are the most abundant lithology in the well drained facies association (Fig. 12d). They comprise >80% of the thickness of well-drained deposits below 875.5 m and 50–60% of its thickness above this level. Grain size ranges from silty claystone to siltstone. Internal fabrics range from platy to blocky and many become progressively blockier upward. A few siltstones contain ripple cross-laminae. Polished pedogenic slickensides were observed in mudrocks at several levels (178.6 m, 189.7 m, and 1027.3 m) and curved vertic structures with up to 0.5 m of vertical extent are present in blocky red mudrocks at 39.5 m. Polygonal desiccation cracks are present locally; those at 1028.8 m are filled with organic-rich material from overlying beds. Redbeds with calcareous nodules are present throughout the formation; nodules are generally scattered (Machette’s 1985 Stage I or II), although a dense, partially coalesced horizon (Machette’s 1985 Stage III) is developed atop a sandstone at 1026.3 m (Fig. 12e). Gardiner (2005) documented the presence of pedogenic mud aggregates in laminated siltstones, mud- chip rip-up clasts, and carbonate rhizoconcretions in an interval that corresponds to the 952–1041 m interval in our measured section. Pedogenic mud aggregates may also be present within a mudrock-filled scour at 184 m (Fig. 12c); this interval contained a calcite-cemented intraformational conglomerate composed of caliche nodules, rip-up clasts, and sand-sized mudrock aggregates. A variety of mud- aggregate morphologies, including dark hematite-stained claystone and silty mudstone, are present in this lag and many have indented contacts.

56 Scattered green horizons (<0.5 m thick) and diffuse, irregular mottles are common within red mudrocks and also occur locally in association with discontinuous organic-rich bands (<0.01 m thick) or isolated plant fragments. Vertical carbonized roots are ubiquitous and many are surrounded by reduction haloes. Vertically oriented, unbranched calcareous rhizoconcretions are present in red mudrocks at 179 m. A sandstone cast of Stigmaria was observed in red mudrock just above greenish-grey bands at 996.8 m (Fig. 12f); Plint and Browne (1994) observed Stigmaria in reddish-grey mudrocks at ~479 m and in-situ lycopsids at ~881 m.

57 Sheet sandstones are common in well-drained intervals (Fig. 12a). Below 875.5 m they are generally <1-m-thick, isolated, and comprise less than 20% of the thickness of this facies association. Above 875.5 m they become thicker (commonly >1-m-thick), occur in groups to form sandstone-rich intervals within well-drained deposits, and comprise 20–50% of the facies association thickness. Ripple cross-laminae and horizontal laminae are common; cross-beds <0.5 m thick are present locally. Many sheet sandstones have vertical carbonized roots and a blocky fabric caused by the destruction of stratification. Minor sandstone-filled channel bodies (<4 m thick) are commonly associated with sandstone-rich intervals in well-drained deposits. A partially mudrock-filled channel body is contained within a sandstone-rich package at ~1027 m (Fig. 12b). Tetrapod trackways are present in thinly bedded siltstone and sandstone beds within the North Reef Member (Brian L. Hebert, personal communication, 2013).

58 Four grey limestones ranging in thickness from 0.06 to 0.15 m are present within reddish-brown mudrocks in the Chignecto Bay Member between 0 and 50 m (Fig. 13). These lime mudstones are separated from the over- and underlying redbeds by sharp contacts. The limestone at 41 m sits atop a <2 cm grey gleyed horizon developed atop a blocky mudrock with well-developed vertic structures. Bedding-plane exposures of this limestone have desiccation cracks that penetrate 1–2 cm down from the top of the bed (Fig. 13a). The limestone is overlain by platy to blocky red mudrocks that are similar to those that encase the overlying limestones. Although body fossils were not observed macroscopically, petrographic analysis of the limestone at 41 m revealed a gastropod fragment, and possible ostracods and sinuous algal or cyanobacterial filaments (Fig. 12c). The overall lack of fossils, light-grey color, and sedimentological context of limestones within the well drained facies association makes them easy to distinguish from the dark-grey, organic-rich limestones of the open water facies association.

59 The well drained facies association was deposited in a floodplain environment where subaerial exposure and drainage conditions caused oxidation of iron and decomposition of organic material. Mudrocks were deposited through suspension deposition and later transformed into paleosols that record a variety of types, maturities, and processes.

60 Platy to blocky redbeds with scattered roots and poorly developed horizons represent entisols and inceptisols. They were buried before well differentiated horizons could form and appear broadly similar to the immature redbed paleosols described from the Joggins and Springhill Mines formations (Davies et al. 2005; Rygel et al. 2014). Scattered organic-rich horizons, green mottles, and rare Stigmaria within redbeds suggests that some of these mudrocks were clastic wetlands where there was sufficient water to allow partial preservation of organics and growth of lycopsids. These former wetland soils developed their reddish-brown color either in response to seasonal water-table fluctuations that caused short-lived oxidizing events within wetland soils (Roberts et al. 1981) or post-depositional reddening associated with early diagenesis (Walker 1967; Retallack 2001).

61 Wetland features within the well drained facies association are relatively rare and most paleosols formed under oxidizing conditions developed in response to regional paleoclimate or on localized paleotopographic highs that afforded good drainage (Roberts et al. 1981; Calder et al. 2005). Browne and Plint (1994) and Plint and Browne (1994) report vertisols and aridisols regionally and interpret them as having formed in a semi-arid climate with pronounced rainfall seasonality. These observations are consistent with ours in the type section, where numerous intervals below 479 m (and at 1026.3 m) have vertic structures and subsurface accumulations of pedogenic carbonate. These paleovertisols probably formed in a tropical environment with a sub-humid to semi-arid climate (180–1520 mm annual precipitation) and pronounced rainfall seasonality (Caudill et al. 1996; Retallack 2001).

62 The interpretation of wet-dry seasonality is reinforced by the presence of pedogenic mud aggregates near the top (Gardiner 2005) and bottom of the formation. Pedogenic mud aggregates are sand-sized particles of mud formed in soils with expandable clays developed under a warm climate with wet-dry seasonality (Gierlowski-Kordesch and Gibling 2002). Although it is certainly possible that some of the larger particles represent intraformational rip-up clasts, the examples described in this study (Fig. 12c) are best interpreted as transported aggregates because: they lack pronounced internal stratification; have variable composition; occur in beds with sharp contacts with underlying units; coexist with reworked carbonate nodules; and have rounded edges (Müller et al. 2004). Although they may also be present in paleosols, pedogenic mud aggregates are best seen in channel deposits such as the one at 184 m where they can be protected from compaction by robust framework grains or by early calcite cement (Fig. 11c; Rust and Nanson 1989; Gierlowski-Kordesch and Gibling 2002). Indented contacts in aggregates suggest that they were semi-consolidated at the time of deposition. Tetrapod trackways provide additional evidence for subaerial exposure and presence of a firm substrate.

63 As in the poorly drained facies association, sheet sandstones and associated minor channels represent crevasse-splay deposits. These rapidly aggrading, disturbance-prone environments were colonized by dense thickets of Calamites, which could colonize disturbed habitats due to their free-sporing strategy and ability to regenerate after burial (Gastaldo 1992; Calder et al. 2006). Although scattered throughout well-drained intervals in the lower part of the formation, sandstone-rich intervals with abundant closely-spaced sandstone interbeds become particularly abundant above 940 m, a trend that Ielpi et al. (2014) interpreted as representing increased seasonality. The sandstone-rich overbank motif is similar to well-drained deposits in the overlying Joggins and Springhill Mines formations (Davies et al. 2005; Rygel et al. 2014).

64 The four limestones present in redbeds of the Chignecto Bay Member were deposited in ephemeral floodplain lakes. Unlike limestones in the open water facies association, they are penetrated by desiccation cracks, contain only a few rare macrofossils, and are not associated with any other obviously open-water features (e.g., laminated mudrocks). Broadly similar limestones within redbed-dominated intervals have been described from the Hastings Formation in western Cape Breton (Hamblin 2001) and the Dunkard Group of the Appalachian Basin (Montañez and Cecil 2013).

65 Interpretation of well-drained floodplains within the Boss Point system was confirmed by Ielpi et al. (2014), who examined transported plant material within multistorey channel bodies. Locally derived cordaitalean gymnosperm material made up the overwhelming majority of the plant fossils. These slow-growing trees, which occupied well-drained riparian areas, floodplains, and basin-margin uplands, preferred the type of stable, seasonally dry conditions recorded by the redbed paleosols described above (Falcon-Lang 2003; Falcon-Lang et al. 2004, 2009; DiMichele et al. 2010; Bashforth et al. 2011, 2014).

76 Detailed examination of the type section reveals that the fine-grained intervals contain considerably more floodplain deposits than suggested by the regional studies of Plint and Browne (1994) and Browne and Plint (1994). Given that the cyclic alternations between thick fluvial sandstones and fine-grained deposits in the Ward Point Member can be correlated regionally, their “lacustrine” flooding interpretation may be valid and the abundance of floodplain deposits a local anomaly. Plint and Browne (1994) interpreted the sharp, nonerosive contact between “lacustrine” and fluvial facies as evidence of rapid flooding caused by several metres of downdrop along basin-bounding faults. Although the formation was deposited during a phase of high-amplitude glacioeustasy and contains “brackish” limestones comparable to those described in younger units (Tibert and Dewey 2006; Rygel et al. 2008; Grey et al. 2011), the overwhelming influence of tectonism in the Cumberland Basin makes it difficult to confidently and unequivocally attribute the observed cyclicity to glacioeustatic fluctuations (Plint and Browne 1994; Calder 1994; Gibling and Rygel 2008).

77 Information about the nature and initiation of overbank and open water sedimentation is recorded by facies transitions within these finer-grained intervals. The following observations from Fig. 5 and Appendix 2 are particularly relevant:

• Megacycles 2, 4, 5, 6, 10, 12, and 16 have well exposed fine-grained floodplain intervals that lack open-water intervals and are composed only of poorly drained and well-drained deposits.
• Open-water intervals at the base of megacycles 1 and 3 sharply overlie multistorey sandstones in a way consistent with the rapid flooding events interpreted by Browne and Plint (1994).
• Open-water intervals in megacycles 10 and 13/14 occur atop floodplain deposits, suggesting more gradual flooding of the basin. Interbedded open-water and poorly drained deposits at the base of megacycle 15 also suggest gradual flooding and fluctuations in water depth.
• Open-water intervals are overlain by both poorly drained (megacycles 13/14) and well-drained deposits (megacycle 1 and 951.7 m). Where open-water deposits are absent, there is no systematic relationship between poorly drained and well-drained deposits (megacycles 2, 3, 4, 5, and 6). These relationships suggest that there is not necessarily a systematic, Walther’s Law-type progression from open-water to poorly drained to well-drained facies associations. These features may indicate an underfilled nature for some of the open-water bodies (Ielpi 2013).
• Relationships between open-water intervals and floodplain deposits cannot be determined where open-water units are erosionally overlain by multistorey sandstones (megacycles 3 and 10).

78 These relationships suggest that, at the type section, only some of the Boss Point megacycles record direct evidence of flooding and that these events could have been either rapid (megacycles 1 and 3) or gradual (megacycles 10, 13/14, and 15). Open-water intervals are overlain by both poorly drained and well-drained deposits, suggesting that there was not always a substantial wetland area flanking the shoreline and that open-water sedimentation ceased by infilling of the lake and progradation of a muddy shoreline.

79 Megacycles with only fine-grained terrestrial deposits may record an updip expression of the open-water flooding events. Because the type section was deposited on the flank of the Minudie Anticline, it may have occupied a subtle paleotopographic high that was inundated only by the largest flooding events or that was syndepositionally uplifted by diapirism as fluvial sediment prograded into the basin (Coleman 1988; Davison et al. 2000). Although it is possible that some poorly drained and well-drained deposits may represent pedogenically modified open water deposits, we consider it unlikely that all evidence of open water conditions would have been routinely and completely destroyed in overbank sediments that commonly contain primary textures, colors, and organic material. As mentioned above, it is unclear whether the difference between poorly drained and well-drained facies records local drainage conditions, paleoclimate, or some combination of the two.

80 Crevasse-splay sandstones make up less than ~10% of the thickness of overbank deposits below 781 m and 30–50% of their thickness above this level. Although this pattern may correspond to increased seasonality (Ielpi et al. 2014), the sandstone-rich overbank motif is also typical of overbank deposits in the Joggins and Springhill Mines formations, which were deposited in a more humid, less seasonal climate (Allen et al. 2013). Given this observation, it is equally probable that sandstone-rich overbank deposits represent “normal” floodplain sedimentation patterns during high subsidence periods.

81 In addition to previously described changes in paleoflow, the North Reef Member represents a transition between the cyclic deposition of the underlying Ward Point Member and the uniform redbeds of the overlying Little River Formation. In terms of fluvial style, the North Reef and South Reef channel bodies represent a midpoint between the thick, abundant, regionally extensive multistorey fluvial sandstones of the Boss Point Formation and the thinner, isolated, more ribbon-like channel bodies of the Little River Formation (Calder et al. 2005; Fielding et al. 2011; Allen et al.2013). Fine-grained deposits in the North Reef member consist only of sandstone-rich well-drained deposits.

82 Calder (1998) noted that this transition could be broadly traced across the Maritimes Basin and attributed it to changes driven by both tectonism and climate. Fielding et al. (2011) and Allen et al. (2013) documented a progressive increase in the abundance of upper flow regime structures in fluvial sandstones of the Boss Point Formation. Both sets of authors interpreted the abundance of these structures as recording a change from a humid to a semi-arid climate. Such a change would have allowed vegetative cover to persist while decreasing runoff and producing an overall decrease in sediment supply and corresponding increase in accommodation/sediment supply (Fielding et al. 2011; Allen et al. 2013). The North Reef and South Reef channel bodies may represent very short term anomalies wherein pulses of sediment were delivered to the basin, perhaps due to periods of marked decrease in vegetative cover caused by fire and/or drought (Falcon-Lang 1998, 1999, 2000).

83 Intensive halokinesis may have begun during deposition of the North Reef Member (Waldron and Rygel 2005; Waldron et al. 2013), a process that would have increased the ratio of accommodation to sediment supply and favored the shift to isolated channel bodies encased in overbank fines (Shanley and McCabe 1994; Banham and Mountney 2014). This transition was probably diachronous across the Cumberland Basin, as the locus of salt withdrawal would have shifted progressively away from basin margin areas as alluvial fans built further into the basin.