Sedimentological Evidence for Rotation of the Early Permian Nambucca Block (Eastern Australia)

Sedimentological evidence for rotation of the Early Permian Nambucca block (eastern Australia)

Christopher R. Fielding1,*, Uri Shaanan2, and Gideon Rosenbaum2 1DEPARTMENT OF EARTH AND ATMOSPHERIC SCIENCES, 214 BESSEY HALL, UNIVERSITY OF NEBRASKA-LINCOLN, NEBRASKA 68588-0340, USA 2SCHOOL OF EARTH SCIENCES, UNIVERSITY OF QUEENSLAND, ST LUCIA, QUEENSLAND 4072, AUSTRALIA

ABSTRACT

The Early Permian tectonic history of eastern Australia led to the formation of several orogenic curvatures termed the New England oroclines. How these oroclines formed is a controversial issue that is crucial for understanding the paleo-Pacific subduction dynamics at the Gondwanan margin and the formation of curved orogenic belts in general. Here we present new constraints on the role of vertical-axis block rotations in the New England oroclines using paleocurrent indicators from the core of the oroclinal structure (the Nambucca block). Focusing on the lower sedimentary succession within the Nambucca block (Kempsey beds), we recognize two facies associations. Facies association A comprises conglomerate and gravelly sandstone with minor sandstone, collectively interpreted as the deposits of coastal to subaqueous marine fans. Facies association B is made of heterolithic intervals of sandstone and mudrock that are interpreted as the products of deposition on a marine continental slope. Younging directions suggest that facies association A represents the basal part of the succession that is overlain by the more heterolithic association. The paleogeographic position of the Nambucca block, in conjunction with its stratigraphy and geochronological provenance, suggests that it formed as part of a large, deep-marine backarc basin. Paleocurrent and paleoslope directions are north to northeast, inconsistent with the present understanding of the Permian paleogeography that involved an approximately north- south–oriented continental margin (in present coordinates) and an eastward-deepening marine surface. This supports previous paleomagnetic interpretations of counterclockwise rotations of adjacent blocks. In conjunction with recently published structural, paleomagnetic, and geochronological constraints, our data suggest that counterclockwise rotations occurred between 285 and 275 Ma in the course of the formation of the southern segment of the New England oroclines (Manning orocline). The rotation incorporated both continental and marine plate margin segments of eastern Gondwana, thereby deforming the deep backarc basin that is partially represented by the Nambucca block. Our data thus provide constraints both on the kinematics and on the timing of the much-debated southern segment of the New England oroclines.

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INTRODUCTION constrained to the Early Permian (299–272 Ma; Shaanan et al., 2015a, and references therein), and based on the available structural, geochro- The New England Orogen is the youngest and easternmost component nological, and paleomagnetic evidence, it has recently been hypothesized of the Tasmanides in eastern Australia (Fig. 1A; Glen, 2005; Cawood, that, similar to modern examples of oroclinal bending (e.g., Rosenbaum, 2005). The structural grain of the southern New England Orogen consti- 2014), the New England oroclines formed in a backarc region associated tutes a set of orogenic curvatures (oroclines) that includes the Texas, Coffs with a retreating subduction zone (Shaanan et al., 2015b). Harbour, Manning, and Nambucca oroclines (Figs. 1B–1E). The major The Manning orocline, which is located at the southernmost part of evidence for the oroclinal structure includes (1) a curved aeromagnetic the oroclinal structure, is particularly controversial (e.g., Lennox et al., anomaly (Fig. 1C); (2) a curved distribution of Devonian–Carboniferous 2013; Li and Rosenbaum, 2014, 2015; Offler et al., 2015; White et al., forearc and accretionary complex rock units (Fig. 1B) (Korsch and Har- 2016). This orogenic curvature appears to be structurally more complex rington, 1987; Rosenbaum, 2012); (3) a contorted belt of Early Permian (Li and Rosenbaum, 2014; White et al., 2016) and its recognition is there- S-type granitoids (Fig. 1D) (Rosenbaum et al., 2012); and (4) curved fore somewhat more ambiguous (Figs. 1C, 1E). Nonetheless, a number structural and magnetic fabrics (Fig. 1E) (Korsch and Harrington, 1987; of independent lines of evidence, such as the curved shape of the Early Aubourg et al., 2004; Li et al., 2012; Li and Rosenbaum, 2014; Mochales Permian granitoid belt (Fig. 1D; Rosenbaum et al., 2012), support the et al., 2014). The existence of the orogenic curvature is well established; existence of the orocline. The role of vertical-axis block rotations, how- however, interpretations of paleomagnetic data are more ambiguous ever, is yet to be tested. (Schmidt et al., 1994; Geeve et al., 2002; Cawood et al., 2011b; Shaanan et Paleomagnetic results from Devonian–Carboniferous forearc blocks al., 2015a; Pisarevsky et al., 2016), thus leading to uncertainties in regard (Rouchel, Gresford, and Myall; Fig. 1B) are generally consistent with to the process of oroclinal bending. The timing of oroclinal bending is counterclockwise block rotations by as much as 120° (Geeve et al., 2002) prior to the Middle Permian (Shaanan et al., 2015a). However, the *[email protected] link between apparent block rotations and oroclinal bending remains

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27°S A B Bowen Basin

Brisbane rocline s O xa e T 28°S Texas AL New region Queensland e England TB in SS Precambrian L Orogen PK an New South BB sm Ta Wales 29°S Tasmanides AS Co s Harbour Orocline

Sydney, Gunnedah, B.-E. 30°S and Bowen Dy basins CH Tamworth Belt

Nambucca 500 km PMFS Block 31°S City Hastings Nambucca Fault ( Dextral Thrust) We F. Orocline Gunnedah Oroclinal structure Basin Mesozoic - Cenozoic Early-mid Permian basins Rouchel 32°S Permian magmatic rocks Gresford Manning Orocline and Manning Basin Early Permian granitoids CC Wongwibinda Metamorphic Complex Myall Dev-Carb. accretionary complex Sydney Dev-Carb. fore-arc basin Basin 0 50 100 Newcastle Km 33°S Paleozoic serpentinites 151°E 152°E 153°E 154°E

Figure 1. Tectonostratigraphic, aeromagnetic, and geological maps of the study area. (A) The Tasmanides of eastern Australia and location of the Syd- ney-Gunnedah-Bowen basin system and the New England Orogen. (B) Tectonostratigraphic map of the southern New England Orogen. (Continued on following page.)

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C F TO Dyamberin Block CHO Co s Harbour

NO MO

200 Km D

Nambucca Block

Nambucca Slate Smoky Cape Kempsey beds

200 Km

Hastings Block Hat Head E (Korogoro)

Crescent Head

Port Macquarie

200 Km 10 km

Figure 1 (continued ). (C) Aeromagnetic gridded map of the southern New England Orogen (from Geoscience Australia; Milligan et al., 2010) highlight- ing the oroclinal structure. (D) Early Permian S-type granitoids. (E) Structural fabrics (dashed black; after Li et al., 2012) and magnetic fabrics (foliation in red and lineations in grayscale; after Mochales et al. 2014). (F) Geological map of the Nambucca block and its vicinity. Abbreviations: AL—Alum Rock Conglomerate, AS—Ashford Coal Measures, BB—Bondonga beds, CC—Cranky Corner outlier, CH—Coffs-Harbour block, CHO—Coffs-Harbour orocline, Dy—Dyamberin block, MO—Manning orocline, NO—Nambucca orocline, PK—Pikedale beds, PMFS—Peel-Manning fault system, SS—Silver Spur beds, TB—Texas beds, TO—Texas orocline, We—Werrie syncline, Dev.-Carb—Devonian to Carboniferous.

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inconclusive because of the possibility that angular relations of paleo- zone in the area of the Manning orocline (Manning Basin; White et al., magnetic vectors represent large displacements across medium to high 2016), (3) the Cranky Corner outlier in the Gresford block (Fig. 1B; Facer latitude rather than vertical-axis block rotations (Cawood et al., 2011b). and Foster, 2003), and (4) the more extensive outcrop belts of the Nam- To address this shortcoming, we have taken an alternative approach that bucca (Leitch, 1978, 1988; Johnston et al., 2002; Shaanan et al., 2014, focuses on sedimentological data from Lower Permian rocks. The data 2015b) and Dyamberin blocks (Korsch, 1978; Shaanan and Rosenbaum, inform us on paleocurrent directions and the paleoslope of the continental 2016) (Fig. 1F). Detrital zircon provenance studies of the Nambucca and margin. Combined with a new synthesis of geochronological provenance Dyamberin blocks indicate that both successions are correlative and were data, and available paleomagnetic and structural information, these results likely deposited in one basin (Shaanan and Rosenbaum, 2016). Moreover, are used to infer that vertical-axis block rotation may have played an early Paleozoic and Precambrian zircon U-Pb age populations in the suc- important role in the formation of the Manning orocline. cession of the Nambucca and Dyamberin blocks indicate that detritus was transported and recycled from cratonic Gondwana, thus suggesting that GEOLOGICAL SETTING sedimentation occurred in a backarc environment (Shaanan et al., 2015b; Shaanan and Rosenbaum, 2016). The New England Orogen (Fig. 1) is predominantly composed of The Lower Permian succession of the Nambucca and Dyamberin Devonian–Carboniferous subduction-related rocks, which are in part blocks is fault bound against older Devonian–Carboniferous accretionary intruded and/or overlain by Permian–Triassic magmatic and clastic sedi- complex and forearc basin units (Tablelands Complex and Hastings block, mentary rocks (Leitch, 1974, 1975a). Lower Permian sedimentary succes- respectively; Fig. 1F). Rocks of the Nambucca block vary from moderately sions are mainly found in the Sydney-Gunnedah-Bowen basin system (Fig. deformed in the south to intensely deformed further north and west (with 1A), but also in outliers throughout the southern New England Orogen multiple, superimposed structural fabrics including slaty cleavage) and are (Figs. 1B and 2) (Roberts and Engel, 1987; Korsch et al., 2009). The ori- in part regionally metamorphosed (Leitch, 1975b, 1978, 1988; Offler and gin of these sedimentary basins has been attributed to a phase of crustal Brime, 1994; Shaanan et al., 2014). Leitch (1975b, 1978) estimated a total extension, which occurred throughout the margin of eastern Gondwana thickness of at least 5 km for the succession, and Shaanan et al. (2014) in the Early Permian (Veevers et al., 1994) and was possibly driven by showed a broad younging to the northwest and a stratigraphic tendency trench retreat (Jenkins et al., 2002; Shaanan et al., 2015b). associated with crude upward fining. The Kempsey beds, which occur in Among the lower Permian outliers that are within the oroclinal struc- the southeastern part of the Nambucca block (Fig. 1F), are characterized ture (Fig. 1B) are (1) several discrete outcrop belts in the Texas region by well-preserved conglomerate and sandstone-dominated rocks (Brunker (Silver Spur, Alum Rock, Terrica, Bondonga, Pikedale, and Ashford; et al., 1970; Shaanan et al., 2014). The rocks of the Kempsey beds are Donchak et al., 2007; Campbell et al., 2015), (2) a structurally complex significantly less deformed and less metamorphosed than the metapelitic

GUNNEDAH WERRIE NORTHERN MANNING NAMBUCCA System & Stage BASIN SYNCLINE SYDNEY BASIN BASIN BLOCK Ma MAITLAND GROUP 270 ROA. WATERMARK FM.

PORCUPINE FM. KUN. GRETA

280 N COAL MEASURES A MAULES CREEK

M N FORMATION

A I

E L

P A LEARD FM. MANNING GROUP R ART.

FARLEY FM.

U S 290 I WERRIE BASALT RUTHERFORD FM. C GOONBRI FM. TEMI FORMATION ALLANDALE FM. KEMPSEY BEDS SAK. WERRIE BASALT LOCHINVAR FM. AND EQUIVALENTS BOGGABRI VOLC. WOODTON ASS. FORMATION 300

L GZH.

O U

R KAS.

A CURRABUBULA

C F SEAHAM FM.

P VNMOS. FORMATION

Continental (lacustrine/alluvial) Coastal plain Shallow marine Deep marine

Figure 2. Time-space diagram showing the distribution of uppermost Pennsylvanian through lower Permian stratigraphic units across the Gunnedah and northern Sydney Basins, and adjacent southern New England Orogen. Based on time-space framework of Fielding et al. (2008), and updated using data from Metcalfe et al. (2015), Shaanan et al. (2015b), Phillips et al. (2016), White et al. (2016), and our data. Absolute time frame is from Cohen et al. (2013; updated 2015). Abbreviations: MOS.—Moscovian, KAS.—Kasimovian, GZH.—Gzhelian, ASS.—Asselian, SAK.—Sakmarian, ART.—Artinskian, KUN.—Kungurian, ROA.—Roadian, FM.—formation, VOLC.—volcanics.

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rocks in the northwestern part of the Nambucca block (Nambuccca slate), TABLE 1. GEOCHRONOLOGICAL DATA SOURCES although the deformation history of both parts of the succession appears Sample name FormationNumber of Location to be consistent (Shaanan et al., 2014). concordant (coordinates) analyses Earlier studies have recognized four phases of folding and associated Lat Long deformation in the Nambucca block (Leitch, 1978; Johnston et al., 2002; (°S) (°E) Shaanan et al., 2014), the second of which was dated as 275–265 Ma NAMX1 Nambucca slate7830°47′39″ 153°00′04″ 40 39 by Ar/ Ar geochronology on muscovite (Shaanan et al., 2014). Both NAMX10Nambucca slate4530°51′14.5″ 152°34′56.4″ the first and second phases of deformation have been attributed to the 007_SH_BU Nambucca slate8030°25′54.09″ 153°4′33.58″ process of oroclinal bending (Offler and Foster, 2008; Rosenbaum et al., 050_SH_AK Nambucca slate6 30°35′20.41″ 152°9′54.18″ 2012; Shaanan et al., 2014). Furthermore, in Shaanan et al. (2015b) it 053_SH_AK Nambucca slate3730°46′58.19″ 152°24′48.20″ 066_SH_DE Nambucca slate3930°51′6.93″ 152°38′25.78″ was proposed, based on the large fraction of craton-derived Precambrian 073_SH_NW Nambucca slate113 30°37′21.35″ 152°44′12.15″ detrital zircons in the succession, that deposition occurred in a backarc 019_SH_SM Kempsey beds 96 30°55′7.40″ 153°5′13.94″ basin that developed in response to trench retreat, and that the same driv- 031_SH_HA Kempsey beds 83 31°4′46.33″ 153°2′54.03″ ing mechanism was responsible for the formation of the New England TotalNambucca slate398 oroclines. Shaanan et al. (2015b) showed that the youngest detrital zircon Kempsey beds 179 age populations in the Nambucca block (including the Kempsey beds and Note: Samples NAMX are after Adams et al. (2013) and samples 0XX_SH_ the Nambucca slate) are 299 ± 1.4 (n = 22) and 285.5 ± 2.3 (n = 7) Ma. XX are after Shaanan et al. (2015b). These ages are consistent with smaller detrital zircon U-Pb age populations from the same rocks of 297 ± 6 (n = 5) and 293 ± 7 (n = 7) Ma (Adams et al., 2013) and with a U-Pb SHRIMP (sensitive high-resolution ion microprobe) age of 292.6 ± 2.0 Ma from a dacite at the base of the A succession (Halls Peak Volcanics; Cawood et al., 2011a). B 90 To date, no stratigraphic or sedimentological analysis has been carried out on the Kempsey beds. In the following we provide a facies analysis of 80 the putative lower part of the succession. We evaluate the geochronological 70 provenance relationship of the Kempsey beds with the overlying strata of 60 the Nambucca slate, and establish constraints on the depositional environ- 50 ment and sediment dispersal directions. We then place the succession in the regional context of Early Permian extension and orocline evolution. 40 Nambucca Slate (n = 398) 30 GEOCHRONOLOGY AND PROVENANCE Kempsey beds (n = 179) 20 Relative probability Cumulative proportion (%) 10 In order to compare the geochronological provenance of the Kempsey beds and Nambucca slate, we compiled previously published data sets of 0500 1000 1500 Age (Ma) 2500 3000 detrital zircon U-Pb ages from the Nambucca block (Table 1; after Adams et al., 2013; Shaanan et al., 2015b). The relative probability and cumulative proportion curves of the data sets of the Kempsey beds (n = 179), and of the Nambucca slate (n = 398), predominantly overlap and consist 0500 1000 15002000 2500 3000 3500 of similar age populations (Fig. 3). The close resemblance implies that Age (Ma) the Kempsey beds and the Nambucca slate, despite the clear variation in Figure 3. Geochronological provenance comparison between the grain size and existence of several distinct drainage systems (Shaanan Kempsey beds and Nambucca slate. Previously published (Adams et al., and Rosenbaum, 2016), shared similar provenance and received input of 2013; Shaanan et al., 2015b) detrital zircon U-Pb age data are replotted detritus from the same drainage systems. The consistent scatter of poly- together. The relative probability and cumulative proportion curves of the modal detritus in the Nambucca block (Shaanan et al., 2015b; Shaanan and data sets from the Kempsey beds (n = 179) and the Nambucca slate (n = 398) predominantly overlap, indicating similar age populations. This sug- Rosenbaum, 2016) suggests that the different drainage systems remained gests that despite differing grain size, the Nambucca slate and Kempsey constant during the accumulation of the succession of the entire block. beds share a common provenance. The relative probability curves were Petrographic investigation of sandstones and conglomerates from the plotted using the Isoplot 4.1 toolkit on Microsoft Excel (Ludwig, 2003). Kempsey beds reveals a mineralogically immature composition dominated by lithic fragments, with lesser quartz and minor feldspar (Fig. 4). Most samples are lithic arenites according to the classification of Dott (1964), FACIES ANALYSIS or feldspathic litharenites and litharenites according to Folk (1980). A significant component of sandstone grains is present in most samples The moderately deformed exposures of the Kempsey beds examined (and of sandstone clasts in conglomerates), with lesser pyroclastic, crys- herein represent two distinct facies associations. Facies association A con- talline igneous, and chert lithic grains (Fig. 4). The detrital composi- sists principally of conglomerates with subordinate gravelly sandstones, tion suggests that the Kempsey beds formed by significant reworking of whereas facies association B comprises mainly sandstones with interbed- older sedimentary and igneous detritus. The interpretation of polycyclic ded mudrocks (Table 2). All of the outcrop areas examined exposed one or sedimentation is consistent with previously suggested recycling of detri- other of the two facies associations. None of the exposures shows interbed- tus from the Devonian–Carboniferous forearc units of the New England ding, or vertical juxtaposition, of the two facies associations. Accordingly, Orogen (Shaanan et al., 2015b). Samples plot in the recycled orogenic there is no direct means of establishing whether the two associations field according to the provenance classification of Dickinson et al. (1983). represent lateral facies variations, or an upward stratigraphic change from

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component of angular and complexly shaped, intraformational siltstone A clasts (Fig. 5D). Dominant clast types are quartzite, sandstone, vein quartz, chert, and lesser felsic intrusive lithologies, granites, and volcanic rock types (including fine-grained tuff). Overall, the clast population is poorly sorted, but individual beds show moderate to good sorting (Fig. 5). A sand matrix is dominant in all association A facies. Continuous vertical intervals of association A reach at least 50 m in thickness at Hat Head (Korogoro) (Fig. 5A). Facies A1 occurs both as the upper portions of sharply based, fining-upward units several meters thick (Fig. 5B) and as discrete intervals to at least 20 m thick. Trough 5mm cross-beds are locally visible in both this and facies A2 (Fig. 5E), both of which are typically planar stratified (Fig. 5F). Stratification is in all B cases defined by grain-size differentiation among successive strata. Facies A3 comprises thick intervals of continuous, clast-supported, pebble- to boulder-grade conglomerate (Fig. 5B). Clast imbrication is common in this facies, particularly in outsized and platy clasts (Fig. 5C), and is both of a-axis and b-axis varieties. No trace or body fossils were encountered in association A facies during the course of this study. Paleocurrent directions measured from clast imbrication (n = 120) and cross-bedding (n = 8) indicate a strong northeast mode (Fig. 6). 5mm Interpretation The coarse-grained, stratified nature of much of facies association A C suggests that it formed in the proximal reaches of depositional fans. A purely fluvial origin can be discounted because no channel forms were noted in the 10–50-m-high and laterally extensive cliff exposures. None- theless, it is unclear whether facies association A accumulated in a sub- aerial or subaqueous setting, because no trace or body fossils were found in these rocks. The lack of soft-sediment deformation and mudrock part- ings (together with the lack of fossils) within association A facies argues against deposition in substantial depths of standing water (cf. Nemec and 5mm Steel, 1984). The dominance of stratified beds over massive beds and a lack of any relationship between maximum clast size and bed thickness Figure 4. Photomicrographs of lithic sandstones within the Kempsey beds, (Heward, 1978; Nemec and Steel, 1984) argue for deposition from turbu- from (A) Smoky Cape, (B) Hat Head (Korogoro), and (C) Crescent Head. The left and right halves of images were taken in cross-polarized and plane- lent, frictional flows rather than from debris flows. This interpretation is polarized light, respectively. also supported by the common preservation of trough cross-bedding. The fact that the most abundantly preserved physical sedimentary structure is planar stratification, however, suggests that formative flows were powerful and often within the stability field of plane beds, and/or that they were one association into the other. The establishment of general northwestward carrying high concentrations of sand in traction and near-bed suspension, younging in coastal outcrops of the Nambucca block led Shaanan et al. leading to suppression of bedforms (Sumner et al., 2008; Baas et al., 2011, (2014) to suggest that the Permian succession preserves a gross fining- 2016). Overall, the lithology, texture, fabric and preserved sedimentary upward character. Nonetheless, exposures of the two facies associations structures suggest that facies association A was formed in shallow-water alternate along the coast (from south to north, Crescent Head, Hat Head fans or fan deltas that issued northeastward into the formative basin. [Korogoro], Smoky Cape, and Southwest Rocks; Fig. 1F). From regional structural orientations (Shaanan et al., 2014), it is clear that the coarser Facies Association B grained lithologies of the Kempsey beds as a whole pass northward and westward (stratigraphically upward) across the Nambucca block into more Description strongly deformed, mudrock-dominated lithologies of the Nambucca slate. Facies association B (Table 2; Fig. 7) comprises an array of clastic lithologies ranging from interbedded sandstones and siltstones (facies Facies Association A B1), through discrete sharp-bound sandstones beds (facies B2), to amalgamated sandstone intervals (facies B3), intraformational siltstone clast Description breccias (facies B4), and a single occurrence of intraformational sand- Facies association A (Table 2; Fig. 5) comprises an array of three stone clast breccia (facies B5). Although some of the sandstones in this facies that are intimately interbedded with each other, ranging from facies association are coarse to very coarse grained and locally contain coarse-grained sandstone (facies A1), through gravelly sandstone and small extraformational and intraformational gravel, there is no palpable matrix-supported conglomerate (facies A2), to clast-supported, pebble to overlap with facies of association A. Vertical intervals of up to at least boulder conglomerate (facies A3). The coarse fraction comprises typically 75 m are continuously exposed in coastal cliffs near Crescent Head (Fig. subrounded to well-rounded clasts, as much as 40 cm in a-axis length, 1F). A graphic log of the best-exposed portion of the section at Crescent but typically <10 cm (Fig. 5C), and mostly extraformational with a local Head is presented in Figure 8.

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TABLE 2. CHARACTERISTICS OF LITHOFACIES IDENTIFIED FROM THE KEMPSEY BEDS Lithologies Sedimentary structures Trace Fossils Interpretation

Facies association A A1 Sandstone and granule conglomerate Flat stratification, trough cross-beddingNone identified Distal or lateral locations on fan lobes A2 Matrix-supported conglomerate to Flat stratification, trough cross-beddingNone identifiedMedial fan lobe gravelly sandstone A3 Clast-supported pebble to boulder Crude flat stratification, clast imbrication None identified Proximal fan lobe conglomerate (a- and b-axes)

Facies association B B1 Thinly interbedded siltstone and very Linsen (pinstripe), lenticular and wavy Planolites, Asterosoma, Distal submarine slope lobe fine- to fine-grained sandstone bedding, flat and low-angle lamination, Helminthopsis, Zoophycos, ripple cross-lamination, load casts, Cosmorhaphe, sedimentary intrusions, intraformational Palaeophycus, siltstone clasts ?Siphonichnus B2 Sharp-bounded sandstone beds Normal grading, intraformational and Zoophycos, Planolites, Medial submarine slope lobe >0.3 m thick extraformational gravel, flat and low-angle ?Siphonichnus, lamination, convex-upward stratification, fugichnia convolute bedding, load casts, sedimentary intrusions B3 Amalgamated intervals of sharp- Flat and low-angle lamination, convolute None identified Proximal submarine slope lobe bounded sandstone beds bedding, sedimentary intrusions

B4 Intraformational siltstone clast breccia Local clast imbrication None identiﬁed Erosional event on submarine slope lobe

B5 Intraformational breccia with imbricate Imbrication, compressive deformation, None identiﬁedSubmarine slope failure (slump) slabs of sandstone convolute bedding, load casts

Thinly interbedded sandstones and siltstones (facies B1) contain a which in turn may point to periodically dysoxic to anoxic seafloor con- variety of interlamination and soft-sediment deformation structures (Fig. ditions that led to restricted trace diversity, another characteristic of the 7B), and some are diversely bioturbated (Fig. 7C; Table 1). Sandstone Zoophycos Ichnofacies. beds (facies B2 and B3) are sharply bounded (Figs. 7A, 7B, 7F), and many The dominance of planar and low-angle stratification in facies B2 and are normally graded, with small gravel abundant in the basal portion of B3, with some convex-upward stratification and common scour surfaces, beds. The most common structures are planar and low-angle lamination suggests that sand was deposited from turbulent (frictional) flows that locally with a convex-upward component (Fig. 7B), and scour surfaces were transcritical (within the stability fields of plane beds, antidunes, are common within composite beds (Fig. 7D). Soft-sediment deformation and even chutes and pools; Cartigny et al., 2014). Some flows may have structures are common, including small clastic intrusions, some of which been high-concentration flows transitional to debris flows on the basis are tilted in the direction of paleoflow (Fig. 7E). Bioturbation is sparse, of their virtually massive character with floating siltstone clasts (Mulder and where present is composed of vertical traces (especially fugichnia; and Alexander, 2001). The presence of internal erosion surfaces and ver- escape burrows) in the uppermost parts of beds. Paleocurrent indicators tical changes in sedimentary structure within composite sandstone beds (n = 40) suggest northeastward sediment dispersal (Fig. 6). suggests sustained flows of temporally varying strength. The general absence of trace fossils from all but the very tops of some sandstone Interpretation beds is suggestive of rapid rates of sand deposition from formative flows. The presence of trace fossils associated largely or exclusively with The occurrence of locally derived (from the ragged clast shape) siltstone marine settings indicates that facies association B formed subaqueously clast breccias (facies B4) attests to the erosional potential of these flows. in a marine environment. The absence of any wave- or combined flow- Tilting of load structures, small sandstone dikes, and some trace fos- generated sedimentary structures from facies association B places the sil shafts in the direction of paleoflow (determined independently from depositional environment below (storm) wave base. The trace fossil physical sedimentary structures) suggests that deposition occurred on a assemblage, most diversely preserved in facies B1, is interpreted as an northeastward slope. expression of the Zoophycos Ichnofacies (MacEachern and Bann, 2008). The occurrence of facies B5 at Crescent Head (Fig. 7F) also indicates The composition of the trace assemblage is also distinctively different that the depositional surface was a slope, subject to failure with downslope from Permian trace fossil suites in nearshore marine successions of the transportation of (apparently) cohesive slabs of sandstone. In the absence Sydney Basin (Thomas et al., 2007; Bann et al., 2008; Rygel et al., 2008; of any evidence for cyclic wave loading of the depositional surface, the Fielding et al., 2006, 2008) in preserving few if any vertical domicile most likely triggers for such slope failures are oversteepening due to traces and more extensive records of surface dwellers and infaunal min- sediment buildup, and seismic shaking of the seafloor. Whatever the trig- ers. This also suggests that the depositional environment was relatively ger, facies B5 indicates that the slope failed en masse, causing coherent deep, in the range of 100–500 m water depth. The medium gray color slabs of sandstone to slide and perhaps locally be entrained into debris of mudrocks in facies B1 suggests moderate organic carbon contents, flows, and then accumulate a short distance downslope in an imbricate

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C D

E F

Figure 5. Field photographs of facies association A. (A) General view of a sea cliff on Korogoro headland, exposing ~50 m of vertical section to the top of the hill. Dips are gently into the face in this exposure. (B) View of an upward-fining conglomerate body (facies A1) that abruptly overlies pebbly sandstones of facies A3 at Hat Head (Korogoro). Hammer is 0.3 m long. (C) Close-up view of facies A1 fabric, showing crude planar stratification, dominance of extraformational clasts, and local imbrication of some larger clasts (arrowed). Horseshoe Bay, Southwest Rocks. Notebook is 0.22 m long. (D) Close-up view of facies A1 at Hat Head, showing common intraformational siltstone clasts with angular and irregular shapes. Notebook is 0.22 m long. (E) Southernmost outcrop of Hat Head, showing trough cross-bedding in gravelly sandstone (facies A2). Notebook (0.22 m long) is on the top of a prominent cross-set. (F) Well-defined planar stratification in facies A1 at Hat Head. Notebook is 0.22 m long.

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N stack. Such failures are common on modern submarine slopes, where they may reach considerable size and are termed mass-transport complexes (e.g., Sawyer et al., 2007; Moscardelli and Wood, 2008; Khani and Back, A Kempsey Beds 2012). The facies B5 occurrence at Crescent Head closely resembles a all data series of Middle Permian submarine debris flow deposits in the Moah M = 042° Creek Beds of east-central Queensland, which were interpreted (Fielding n = 164 et al., 1997) to record the onset of Middle Permian to Triassic multiphase contractional deformation. The range of lithologies and the physical and biogenic sedimentary structures in facies association B are entirely consistent with deposition on a submarine slope, below storm wave base. The surface sloped north to northeastward, based on paleocurrent measurements including the attitudes of imbricated sandstone slabs in facies B5 (Fig. 6). This interpretation is consistent with what little has been published previously on B Hat Head/Korogoro the topic (Leitch, 1988). all data M = 054° DISCUSSION n = 112 Depositional Setting and Time-Space Distribution of Permian Strata

The surface exposures of the Kempsey beds disclose two different depositional environments: shallow fans or fan deltas (facies association A) and submarine slopes below storm wave base (facies association B). The lack of any information regarding the relative stratigraphic position of the two facies associations, and the lack of any interfingering or inter- bedding of the two facies associations, renders resolution of the overall C Crescent Head depositional setting a challenging task. Nonetheless, it is clear that the all data two facies associations are intimately associated, given the alternation M = 026° of one with the other in successive coastal outcrops and the consistency n = 33 in sediment dispersal direction between them (Fig. 6). The local trend of bedding and the idea of a large-scale (megasequence) fining-upward trend in the Nambucca block suggest that facies association A underlies facies association B and that the succession records upward deepening of the depositional setting. The regional paleoslope in the study area was toward the northeast (current orientation), suggesting a large, deep-marine basin along the present-day coast and immediate offshore easternmost Australia, outboard of the other, more localized Early Permian structural outliers. Detrital zircon (U-Pb) ages from the Nambucca block (n = 577; after Adams et al., 2013; Shaanan et al., 2015b), including two samples from the Kempsey beds (n = 179; after Shaanan et al., 2015b), indicate that D Crescent Head sediment accumulation occurred in the Early Permian ca. 299–290 Ma, imbricate slabs with a later phase of sediment accumulation ca. 285 Ma (Shaanan et al., M = 018° 2015b). These sediments were subjected to deformation, with muscovite 40 39 n = 10 from the second foliation phase (S2) dated as 275–265 Ma by Ar/ Ar geochronology (Shaanan et al., 2014). The rocks therefore must have been deposited in the Early Permian. Similar depositional ages are recorded from other structural blocks within the southern New England Orogen (Fig. 9), including the Werrie syncline (Roberts et al., 2006), Manning Basin (White et al., 2016), Dyamberin block (Shaanan and Rosenbaum, 2016), and Texas region (Roberts et al., 1996; Campbell et al., 2015). Data from these areas appear to indicate two major periods of Early Permian sediment accumulation, the first from ca. 299 to 290 Ma, and the second Figure 6. Circular histograms summarizing paleocurrent data from from ca. 290 to 280 Ma. Although there is only modest separation between the Kempsey beds. M is mean. (A) All data. (B) All data from Hat Head these modes, individual areas typically include radiogenic isotope ages (Korogoro). (C) All data from Crescent Head. (D) Imbricate sandstone from both periods and a clear time gap between (Fig. 9). slabs in slump sheet (facies B5) at Crescent Head. Paleocurrent direc- The earliest phase of sedimentation at 299–290 Ma (Asselian to late tions were measured from sedimentary structures where reliably exposed in three dimensions (principally cross-bedding, ripple cross- Sakmarian) is consistently represented in all samples from the Nam- lamination, and imbrication of platy clasts). Data were analyzed and bucca and Dyamberin blocks (Adams et al., 2013; Shaanan et al., 2015b; plotted using EZ-ROSE software (Baas, 2000). Shaanan and Rosenbaum, 2016; Fig. 9). The rocks, which occupy a zone

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A B

C D

RXL ?Si

E F

Figure 7. Field photographs of facies association B. (A) General view of the main headland at Crescent Head, showing interbedded facies B1 and B2 passing upward into more amalgamated sandstones of facies B3. Section illustrated corresponds to the range 2–18 m in Figure 8. (B) Close-up view of interbedded facies B1 heterolithic deposits and facies B2 sharp-bound sandstone beds at Crescent Head. Note presence of convex-upward wavy stratification in the lower sandstone bed (possible antidunal stratification; arrow). Hammer is 0.3 m long. (C) Close-up view of bioturbation in facies B1 and B2 at Crescent Head. Abbreviations: RXL—ripple cross-lamination; ?Si—?Siphonichnus; Zo—Zoophycos; Pl—Planolites. Scale card is in inches and centimeters. (D) Close-up view of stratification and internal erosion surface (arrow) in amalgamated sandstones of facies B3 at Crescent Head. Ham- mer is 0.3 m long. (E) Close-up view of facies B4 siltstone clast breccia at Crescent Head, overlain by a bioturbated heterolithic interval (facies B1) that contains a sandstone dike (arrow). The presence of abundant floating siltstone clasts in the upper part of a composite sandstone bed (facies B3) may indicate deposition from a laminar debris flow. (F) View of the interval 16–25 m in Figure 8, at Crescent Head. Much of the interval preserves amalgamated sandstones of facies B3, but a single bed of sandstone slab breccia is preserved near the base of the exposure (facies B5). This bed is interpreted as the product of a submarine slope failure and slump, with a margin of the slump (?sidewall) exposed toward the right side of the field of view (arrow).

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25 Bioturbation Sedimentary Index (BI) Structures 0 2 Planar Lamination Low-angle Lamination 1 3 Linsen (Pinstripe Lamination) Lithology Ripple Cross Lamination Lenticular Bedding Siltstone S Supercritical Flow Structures Sandstone Convolute Bedding Load Casts

Biogenic Structures S Syneresis Cracks Asterosoma Growth Faults

20 Conichnus Siltstone Clast fugichnia Exotic Clast Helminthopsis Paleophycus Planolites Siphonichnus

Zoophycos undifferentiated

15 40

S S

10 S 35

5 S 30 S

0 m 25 BI clay silt sand gravel BI clay silt sand gravel

Figure 8. Graphic sedimentological log of part of the exposed succession at Crescent Head (Fig. 1F). The exposed interval illustrates lithologies and vertical stacking patterns in facies association B (Fig. 7; Table 2).

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TEXAS WERRIE MANNING DYAMBERIN NAMBUCCA System & Stage REGION SYNCLINE BASIN BLOCK BLOCK 280.7 289.0 Ma KUN. ± 3.0 ± 14 289.6 280 ? ± 10 285.5

N 283.1 ± 2.3

WERRIE BASALT A

I ± 5.2 L

I A 281.8 TEMI FM. MANNING M KEMPSEY R ART. GROUP

R U ± 5.2 BEDS

S 293 I 290 P WOODTON AND C 288.5 ± 7 289.7 287.6 FORMATION EQUIV- ± 2.1 SAK. ± 9.9 ± 2.8 ALENTS 295 297 ? ± 18 ± 6 292.6 ASS. 293.7 ± 2.0 ± 3.4 300

L GZH.

N S 299 Y 302.4 297.8 296.8

O U S ± 1.4

I ± 5.1 ± 4.3 ± 8

R KAS.

A CURRABUBULA

C F

P VNMOS. FORMATION Bondonga beds U-Pb SHRIMP age (Roberts et al., 1996) Detrital zircon Detrital zircon age Silver Spur beds Detrital zircon ages age (Shaanan (Shaanan et al., 2015b) Pikedale beds (Campbell et al., 2015) U-Pb SHRIMP age (Roberts et al., 2006) & Rosenbaum, Detrital zircon age Terrica beds 2016) (Adams et al., 2013) Manning Group (White et al., 2016) U-Pb SHRIMP age (Cawood et al., 2011a) Figure 9. Time-space plot showing available timing constraints on the Permian rocks of the southern New England Orogen. Youngest age populations from detrital zircon samples are shown by colored circles, and magmatic ages are shown by squares. Ages are given with one standard deviation (shown also by tagged vertical lines). Age ranges given for individual formations are otherwise based on biostratigraphic data. Time frame, sources, and abbreviations are as in Figure 2. Note the clustering of ages into two broad groups, one from 302 to 290 Ma, and the other from 290 to 280 Ma. SHRIMP—sensitive high-resolution ion microprobe.

in the center of the main embayment of the New England oroclines, differ that represent this age range comprise both diamictites and other probable both in lithology and in inferred depositional environment from rocks of glaciogenic facies with interbedded sandstones and mudrocks of shallow- comparable age that are preserved elsewhere around the trace of the New marine origin. They are coeval with successions in the Gunnedah Basin England oroclinal structure. Included in this latter category are rocks of the (Leard and Goonbri Formations; Tadros, 1993) to the west of the New Texas region (Bondonga beds, Terrica beds, and Alum Rock Conglomer- England Orogen and in the northern Sydney Basin (Allandale, Ruther- ate, Fig. 1B; Roberts et al., 1996; Donchak et al., 2007; Campbell et al., ford, and Farley Formations, McClung, 1980; Fig. 2) that were deposited 2015). The lower parts of all these Permian successions are dominated in shallow-marine and lacustrine environments under the influence of by diamictites, with associated sandstones and mudrocks. The succes- glacial ice (Fielding et al., 2008). Like the earlier deposits, these forma- sions are also correlative to some of the earliest formations preserved tions have all been interpreted to have formed during a period of Early in the northern Sydney Basin (Lochinvar Formation; McClung, 1980) Permian extension (Scheibner, 1973, 1993; Jenkins et al., 2002; Korsch farther southwest (Figs. 1 and 2). Those formations preserve trace and et al., 2009; Shaanan et al., 2015b). body fossils suggesting shallow-marine depositional environments, and the presence of outsized clasts and other features that imply deposition Tectonic Reconstruction and Implications for Oroclinal Bending under glacial influence (Fielding et al., 2008). The glaciogenic facies preserved in all these successions are considered part of the glacial epoch Our results provide new constraints on the Early Permian paleogeog- P1 of Fielding et al. (2008). These formations have all been interpreted to raphy in the southern New England Orogen and specific information on have formed during a period of Early Permian extension (Scheibner, 1973, paleocurrent directions in the Nambucca block. The implications of these 1993; Jenkins et al., 2002; Korsch et al., 2009; Shaanan et al., 2015b). results to tectonic reconstructions (Fig. 10) are discussed in the following. The second phase of sedimentation at 290–280 Ma (Artinskian) is All of the lower Permian basins and outliers mentioned here, from recorded in detrital zircons from sedimentary successions in most outli- the Gunnedah and Sydney Basins to the west, eastward to the coastal ers around the Texas region (Silver Spur beds, Pikedale beds, Terrica exposures of the Nambucca block, are interpreted to have formed in beds, and Bondonga beds; Campbell et al., 2015), detrital zircons from response to crustal extension, most likely in a backarc context (Scheibner, the Manning Basin (White et al., 2016), a U-Pb SHRIMP age from the 1973; Korsch et al., 2009; Jenkins et al., 2002; Shaanan et al., 2015b). Werrie syncline (Woodton Formation; Roberts et al., 2006), and detrital Furthermore, a number of studies have shown that Early Permian exten- zircons from the Nambucca block (Shaanan et al., 2015b) and the Dyam- sion occurred approximately simultaneously with oroclinal bending in berin block (Shaanan and Rosenbaum, 2016; Figs. 1 and 9). The rocks the southern New England Orogen (Cawood et al., 2011b; Rosenbaum

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27°S Postulated paleodrainage ABLand (current day) Early Permian successions Brisbane Dev-Carb. Accretionary Complex rocline rocline s O s O Dev-Carb. Fore-arc basin xa xa e e T 28°S T

Queensland

New South Wales 29°S Co s Harbour Co s Harbour Block Block

30°S Dyamberin Block Tamw Tamw Co s Harbour or Nambucca Orocline or th Belt th Belt Block 31°S Manning Basin (west) (east) Hastings Nambucca Orocline Gunnedah Gunnedah Basin Basin Ø Ø Rouchel 32°S Rouchel Manning Orocline Gresford Gresford (Ø inferred rotation axis) Hastings Dyamberin Myall Myall Nambucca Block Block Sydney Sydney Basin 050 100 Basin Newcastle Km 33°S 151°E 152°E 153°E 154°E

Figure 10. Suggested reconstructions for the rotation of the blocks of the eastern limb of the Manning orocline, southern New England Orogen, eastern Australia. Paleodrainage is modified after Shaanan and Rosenbaum (2016). Dev.-Carb—Devonian to Carboniferous.

et al., 2012; Shaanan et al., 2014, 2015a, 2015b). We therefore think that paleocurrent measurements do not seem to conform with typical drainage the spatiotemporal record associated with the depositional environment orientations, which are expected to be orthogonal to the plate boundary. of the lower Permian successions contributes to the understanding of the The inconsistency between the measured paleocurrent directions and the process of oroclinal bending. expected approximately north-south orientation of the continental margin The depositional environment of the Gunnedah and Sydney Basins, as suggests that the Nambucca block may have been rotated around a vertical well as the Texas region, Werrie syncline, and Manning Basin, was mainly axis. Such block rotations commonly occur in backarc regions during the lacustrine and shallow marine during the early Permian. In contrast, the progressive curvature of the plate boundary that is driven by trench retreat lower Permian rocks of the Dyamberin and Nambucca blocks were initially (e.g., see Lonergan and White, 1997; Rosenbaum, 2014). deposited in a shallow-marine setting that progressively became deep In order to account for the paleocurrent orientations, we suggest that marine over time. Altogether, the rocks of the Dyamberin and Nambucca the Nambucca block was subjected to a counterclockwise rotation around blocks show distinct sedimentological features indicative of deposition in the inferred hinge of the Manning orocline (Fig. 10). A number of inde- deeper water environments relative to the other lower Permian rocks farther pendent arguments support this reconstruction. (1) Rocks from the Nam- west. Within the Nambucca block, samples from the Kempsey beds and bucca block, Cranky Corner outlier, and northern Sydney Basin (Fig. 1B) Nambucca slate show remarkably similar geochronological provenances share similar sedimentary facies, thus suggesting connectivity during the (Fig. 3), which also correspond to the geochronological provenance of early Permian. (2) Paleomagnetic studies from Devonian–Carboniferous the Dyamberin block (Shaanan and Rosenbaum, 2016), indicating that forearc basin rocks of the Rouchel, Gresford, and Myall blocks record the two formations, and the two blocks, received detritus from similar counterclockwise rotations by 80°, 80°, and 120°, respectively (Geeve sources. This means that the paleocurrent directions from the Kempsey et al., 2002), before 272 Ma (Shaanan et al., 2015a). It is therefore pos- beds likely represent the general paleocurrent direction in the Nambucca sible that the Nambucca block was subjected to a similar sense of rota- block. However, we note that the observed north- to northeast-directed tion. The Hastings block father east (Fig. 10) has also been subjected to

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rotations and translations, although the sense of kinematics and timing Baas, J.H., 2000, EZ-ROSE: A computer program for equal-area circular histograms and statistical analysis of two-dimensional vectorial data: Computers & Geosciences, v. 26, of emplacement are debated (Schmidt et al., 1994; Roberts et al., 1995; p. 153–166, doi:10.1016/S0098-3004(99)00072-2. Lennox and Offler, 2009; Cawood et al., 2011a, 2011b; Pisarevsky et al., Baas, J.H., Best, J.L., and Peakall, J., 2011, Depositional processes, bedform development 2016; Phillips et al., 2016). (3) A post–288 Ma counterclockwise rotation and hybrid bed formation in rapidly decelerated cohesive (mud-sand) sediment flows: Sedimentology, v. 58, p. 1953–1987, doi:10.1111/j.1365-3091.2011.01247.x. was also inferred for the eastern part of the Manning Basin, based on a Baas, J.H., Best, J.L., and Peakall, J., 2016, Predicting bedforms and primary current stratifica- recent structural investigation (White et al., 2016). tion in cohesive mixtures of mud and sand: Journal of the Geological Society [London], The timing of block rotations is constrained by several lines of evi- v. 173, p. 12–45, doi:10.1144/jgs2015-024. Bann, K.L., Tye, S.C., MacEachern, J.A., Fielding, C.R., and Jones, B.G., 2008, Ichnological dence. The first phase of deformation in rocks of the Nambucca block is and sedimentologic signatures of mixed wave- and storm-dominated deltaic depos- represented by penetrative vertical east-west slaty cleavage, and asym- its: Examples from the Early Permian Sydney Basin, Australia, in Hampson, G.J., et metric, rounded, open mesoscopic folds (Leitch, 1978; Johnston et al., al., eds., Recent advances in models of siliciclastic shallow-marine stratigraphy: SEPM (Society for Sedimentary Geology) Special Publication 90, p. 293–332, doi:10 .2110 2002; Offler and Foster, 2008; Shaanan et al., 2014), which were sug- /pec.08 .90 .0293. gested to result from north-south contraction of the Nambucca block in Brunker, R.L., et al., 1970, Hastings: New South Wales Department of Mines Geological Series map sheet SH 56-14, scale 1:250,000. the course of oroclinal bending (Offler and Foster, 2008; Shaanan et al., Campbell, M., Rosenbaum, G., Shaanan, U., Fielding, C.R., and Allen, C., 2015, The tectonic 2014). This deformation phase and thus the rotation of the block are con- significance of Lower Permian successions in the Texas Orocline (eastern Australia): Aus- strained to have taken place after sediment accumulation (post–285 Ma; tralian Journal of Earth Sciences, v. 62, p. 789–806, doi:10.1080 /08120099 .2015.1111259. Cartigny, M.J.B., Ventra, D., Postma, G., and van den Berg, J.H., 2014, Morphodynamics and Shaanan et al., 2015b) and before deformation (pre–275 Ma) (Shaanan et sedimentary structures of bedforms under supercritical-flow conditions: New insights al., 2014). These constraints overlap with the 298–288 Ma ages of a bent from flume experiments: Sedimentology, v. 61, p. 712–748, doi:10 .1111 /sed.12076. belt of granitoids that provide a maximum constraint for oroclinal bending Cawood, P.A., 2005, Terra Australis Orogen: Rodinia breakup and development of the Pacific and Iapetus margins of Gondwana during the Neoproterozoic and Paleozoic: Earth-Science (Rosenbaum et al., 2012), and a minimum age constraint from paleomag- Reviews, v. 69, p. 249–279, doi:10.1016/j.earscirev.2004.09.001. netic data that indicate that no significant block rotations occurred after Cawood, P.A., Leitch, E.C., Merle, R.E., and Nemchin, A., 2011a, Orogenesis without collision: Stabilizing the Terra Australis accretionary orogen, eastern Australia: Geological Society 272 Ma (Shaanan et al., 2015a). of America Bulletin, v. 123, p. 2240–2255, doi:10 .1130 /B30415 .1. Cawood, P.A., Pisarevsky, S.A., and Leitch, E.C., 2011b, Unraveling the New England orocline, CONCLUSIONS east Gondwana accretionary margin: Tectonics, v. 30, TC5002, doi:10 .1029/2011TC002864. Cohen, K.M., Finney, S.C., Gibbard, P.L., and Fan, J.X., 2013, The ICS international chronostrati- graphic chart: Episodes, v. 36, p. 199–204. A sedimentological study, complemented with a synthesis of detri- Dickinson, W.R., Beard, L.S., Brakenridge, G.R., Erjavec, J.L., Ferguson, R.C., Inman, K.F., Knepp, tal zircon geochronological data, was conducted on the lower Permian R.A., Lindberg, F.A., and Ryberg, P.T., 1983, Provenance of North American Phanerozoic sandstones in relation to tectonic setting: Geological Society of America Bulletin, v. 94, Kempsey beds of the Nambucca block, eastern Australia. The Kempsey p. 222–235, doi:10.1130/0016-7606(1983)94<222:PONAPS>2.0.CO;2. beds, comprising a lower conglomeratic association and an overlying Donchak, P.J.T., Bultitude, R.J., Purdy, D.J., and Denaro, T.J., 2007, Geology and mineralisa- heterolithic sandstone-mudrock–dominated association, are interpreted to tion of the Texas region, south-eastern Queensland: Queensland Geology, v. 11, p. 1–96. Dott, R.H., 1964, Wacke, graywacke and matrix: What approach to immature sandstone clas- have formed in initially shallow water or even emergent fans and fan deltas, sification?: Journal of Sedimentary Petrology, v. 34, p. 625–632, doi:10 .1306/74D71109 evolving over time into deeper marine slope environments. This implies -2B21-11D7-8648000102C1865D. Facer, R.A., and Foster, C.B., 2003, Geology of the Cranky Corner Basin: Geological Survey the existence of a large, deep-marine basin along the present-day eastern of New South Wales Coal and Petroleum Geology Bulletin 4, 252 p. Australian coast during the Early Permian that contrasted markedly with Fielding, C.R., Stephens, C.J., and Holcombe, R.J., 1997, Submarine mass-wasting depos- more localized, continental to shallow-marine extensional depocenters its as an indicator of the onset of foreland thrust loading—Late Permian Bowen Basin, Queensland, Australia: Terra Nova, v. 9, p. 14–18, doi:10.1046/j.1365-3121.1997.d01-2.x. farther west in the New England Orogen. North to northeastern paleo- Fielding, C.R., Bann, K.L., MacEachern, J.A., Tye, S.C., and Jones, B.G., 2006, Cyclicity in the current and paleoslope measurements suggest postdepositional counter- nearshore marine to coastal, Lower Permian, Pebbley Beach Formation, southern Syd- clockwise northward rotation of the Nambucca block around the inferred ney Basin, Australia: A record of relative sea-level fluctuations at the close of the late Palaeozoic ice age: Sedimentology, v. 53, p. 435–463, doi:10 .1111 /j .1365 -3091 .2006 .00770 .x. hinge of the Manning orocline. The proposed kinematic reconstruction Fielding, C.R., Frank, T.D., Birgenheier, L.P., Rygel, M.C., Jones, A.T., and Roberts, J., 2008, is supported by structural evidence from other blocks in the eastern limb Stratigraphic imprint of the late Palaeozoic Ice Age in eastern Australia: A record of alter- nating glacial and nonglacial climate regime: Journal of the Geological Society [London], of the Manning orocline, including the Devonian–Carboniferous blocks v. 165, p. 129–140, doi:10.1144/0016-76492007-036. of the southern Tamworth Belt, Hastings block, and the Early Permian Folk, R.L., 1980, Petrology of sedimentary rocks (second edition): Austin, Texas, Hemphill Manning Basin. A compilation of paleomagnetic and geochronological Publishing Company, 184 p., https://www.lib.utexas.edu/geo/folkready/entirefolkpdf.pdf. Geeve, R.J., Schmidt, P.W., and Roberts, J., 2002, Paleomagnetic results indicate pre-Permian constraints places the rotation of the blocks, and the formation of the counter-clockwise rotation of the southern Tamworth Belt, southern New England Oro- Manning orocline, between 285 and 275 Ma. These results provide robust gen, Australia: Journal of Geophysical Research, v. 107, 2196, doi:10.1029 /2000JB000037. indications for the much-debated existence of the Manning orocline, place Glen, R.A., 2005, The Tasmanides of eastern Australia, in Vaughan, A.P.M., et al., eds., Terrane processes at the margins of Gondwana: Geological Society, London, Special Publication time constraints for its formation, and contribute toward a fuller under- 246, p. 23–96, doi:10.1144/GSL.SP.2005.246.01.02. standing of the development of the New England oroclinal structure and Heward, A.P., 1978, Alluvial fan sequence and megasequence models: With examples from the late Paleozoic Gondwanan margins. Westphalian D–Stephanian B coalfields, northern Spain, in Miall, A.D., ed., Fluvial sedimentology: Canadian Society of Petroleum Geologists Memoir 5, p. 669–702. Jenkins, R.B., Landenberger, B., and Collins, W.J., 2002, Late Palaeozoic retreating and ad- ACKNOWLEDGMENTS vancing subduction boundary in the New England Fold Belt, New South Wales: Austra- This research was supported by Australian Research Council Discovery Grant DP130100130 lian Journal of Earth Sciences, v. 49, p. 467–489, doi:10.1046 /j .1440-0952 .2002.00932.x. to Rosenbaum, S.A. Pisarevsky, Fielding, and F. Speranza. We thank two anonymous referees Johnston, A.J., Offler, R., and Liu, S., 2002, Structural fabric evidence for indentation tecton- for their constructive reviews of the submitted manuscript. ics in the Nambucca Block, southern New England Fold Belt, New South Wales: Austra- lian Journal of Earth Sciences, v. 49, p. 407–421, doi:10.1046 /j .1440-0952 .2002.00919.x. 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MANUSCRIPT RECEIVED 4 MAY 2016 Phillips, G., Robinson, J., Glen, R., and Roberts, J., 2016, Structural inversion of the Tam- REVISED MANUSCRIPT RECEIVED 18 AUGUST 2016 worth Belt: Insights into the development of orogenic curvature in the southern New MANUSCRIPT ACCEPTED 7 OCTOBER 2016 England Orogen, Australia: Journal of Structural Geology, v. 86, p. 224–240, doi:10 .1016 /j.jsg.2016.03.004. Printed in the USA

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