Marine and Petroleum Geology 78 (2016) 516e535

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Marine and Petroleum Geology

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Research paper Provenance of Triassic sandstones on the southwest Barents Shelf and the implication for sediment dispersal patterns in northwest Pangaea

* Edward J. Fleming a, , Michael J. Flowerdew a, Helen R. Smyth a, 1, Robert A. Scott a, 2, Andrew C. Morton a, b, Jenny E. Omma c, Dirk Frei d, Martin J. Whitehouse e a CASP, 181A Huntingdon Road, Cambridge, CB3 0DH, UK b HM Research Associates, St Ishmaels, Haverfordwest SA62 3TG, UK c Rocktype Limited, Oxford, OX4 1LN, UK d Stellenbosch University, Victoria Street, Stellenbosch, South Africa e Swedish Museum of Natural History, Frescativagen€ 40, 114 18, Stockholm, Sweden article info abstract

Article history: Thick Triassic siliciclastic units form major reservoir targets for hydrocarbon exploration on the Barents Received 21 June 2016 Shelf; however, poor reservoir quality, possibly associated with variation in provenance, remains a key Received in revised form risk factor in the area. In this study, sandstone dispersal patterns on the southwest Barents Shelf are 24 August 2016 investigated through petrographic and heavy mineral analysis, garnet and rutile geochemistry and zircon Accepted 3 October 2016 U-Pb geochronology. The results show that until the Early Norian Maximum Flooding Surface, two Available online 5 October 2016 contrasting sand types were present: (i) a Caledonian Sand Type, characterised by a high compositional maturity, a heavy mineral assemblage dominated by garnet and low chrome-spinel:zircon (CZi) values, Keywords: Barents sea predominantly metapelitic rutiles and mostly Proterozoic and Archaean detrital zircon ages, interpreted Triassic to be sourced from the Caledonides, and (ii) a Uralian Sand Type, characterised by a low compositional Palaeogeography maturity, high CZi values, predominantly metamafic rutiles and Carboniferous zircon ages, sourced from Provenance the Uralian Orogeny. In addition, disparity in detrital zircon ages of the Uralian Sand Type with U-Pb zircon geochronology contiguous strata on the northern Barents Shelf reveals the presence of a Northern Uraloid Sand Type, Reservoir quality interpreted to have been sourced from Taimyr and Severnaya Zemlya. As such, a coincidental system is Sediment composition inferred which delivered sand to the Northern Barents Shelf in the late Carnian/early Norian. Following Petroleum basin analysis the Early Norian Maximum Flooding Surface, a significant provenance change occurs. In response to Late Triassic/Early Jurassic hinterland rejuvenation, supply from the Uralian Orogen ceased and the northern Scandinavian (Caledonian) source became dominant, extending northwards out on to the southwest Barents Shelf. The data reveal a link between reservoir quality and sand type and illustrate how prov- enance played an important role in the development of clastic reservoirs within the Triassic of the Barents Shelf. © 2016 Elsevier Ltd. All rights reserved.

1. Introduction corner of the supercontinent Pangaea (Worsley, 2008). This seaway was progressively infilled by prograding delta complexes which The Triassic succession on the Barents Shelf is currently of deposited up to 7 km of siliciclastic sediment in a series of considerable importance for hydrocarbon exploration (Henriksen transgressive-regressive sequences (Glørstad-Clark et al., 2011; et al., 2011; Lundschien et al., 2014). During the Triassic, the area Klausen et al., 2015; Riis et al., 2008). The deposition of thin formed part of a large epicontinental seaway in the northwestern organic-rich shales in front of these prograding systems, followed by extensive paralic sandstones of the delta front and top have led authors to postulate prolific hydrocarbon play potential (e.g. Lundschien et al., 2014). These ideas were reinforced by the dis- * Corresponding author. fi E-mail address: edward.fl[email protected] (E.J. Fleming). covery of the Goliat eld (174 MMbbl estimated) in 2000, which 1 Present address: Neftex Exploration Insights, Halliburton, Abingdon OX14 4RW found good reservoir quality in mid-late Triassic sandstones in the United Kingdom. southern Hammerfest Basin. The considerable thickness of Triassic 2 Deceased. http://dx.doi.org/10.1016/j.marpetgeo.2016.10.005 0264-8172/© 2016 Elsevier Ltd. All rights reserved. E.J. Fleming et al. / Marine and Petroleum Geology 78 (2016) 516e535 517 strata further north, combined with extensive play development progradation of major delta complexes which gradually infilled the has prompted a significant drilling campaign in recent years. remnant end-Permian palaeotopography (Glørstad-Clark et al., However, outside the southern Hammerfest Basin, exploration re- 2010; Lundschien et al., 2014). These are separated by periods of sults within the Triassic have been less successful, with only small transgression where offshore marine deposits onlap against deltaic accumulations and/or residual hydrocarbons being encountered facies. Of particular note is the Early Norian MFS (Klausen et al., (Henriksen et al., 2011). 2015) which separates the Snadd and Fruholmen formations. The reservoir quality of Triassic sandstones on the Barents Shelf Whilst being poorly defined seismically (Glørstad-Clark et al., can be variable (Henriksen et al., 2011) which is a key risk factor for 2010), the surface coincides with a profound change in miner- exploration in the area. The cause of this variability is likely to be alogy and depositional environments (e.g. Bergan and Knarud, complex, but differences in the original sandstone composition 1993; Mørk, 1999; Ryseth, 2014). likely play a significant role. One of the fundamental controls of Traditionally, northern Scandinavia was thought to have been sandstone composition is provenance (Johnsson, 1993). Previous the major source area for Palaeozoic and Mesozoic successions on research has shown this to be inconsistent on the Barents Shelf in the southwest Barents Shelf (Rønnevik et al., 1982). In the Triassic, the Triassic (Mørk, 1999). Northern Scandinavia is thought to have Mørk et al. (1999) identified quartzofeldspathic sandstones in the been an important sediment source throughout the Mesozoic, Hammerfest Basin, interpreted to be derived from the Caledonides particularly during the Jurassic. However, in the Triassic, seismic of Northern Scandinavia and the Baltic margin. However, since the analysis has revealed that major deltaic complexes migrated from early days of hydrocarbon exploration, the recognition of north- the southeast across the shelf (Glørstad-Clark et al., 2010; Klausen westerly prograding clinoforms and an increasing thickness of et al., 2015; Riis et al., 2008) in response to the developing Uralian the sediment pile to the east (Jacobsen and Veen, 1984; Nøttvedt Orogeny. Additional sources have been inferred from Greenland et al., 1993; van Veen et al., 1993) implied the existence of a ma- (Mørk, 1999; Pozer Bue and Andresen, 2014) and local topographic jor source area to the southeast of the Barents Shelf. This was highs (e.g. Glørstad-Clark et al., 2010). The delineation and possible supported by the work of Mørk (1999), who also identified distinct interaction between these systems on the southwest Barents Shelf epidote-bearing, lithic-rich sandstones which were interpreted to is largely unknown. be sourced from the developing Uralian Orogeny. Today, the seismic This paper presents provenance data from Triassic core mate- evidence for delta progradation to the northwest is well docu- rials that form part of the CASP Barents Shelf provenance dataset. mented (Glørstad-Clark et al., 2010; Høy and Lundschien, 2011; The selection includes 39 petrographic analyses, 72 heavy mineral Lundschien et al., 2014; Riis et al., 2008) and the shoreline is analyses, 10 rutile geochemical analyses, 8 garnet geochemical interpreted to have reached Svalbard in the late Carnian (Pozer Bue analyses and 8 U-Pb zircon age analyses. Using an integrated and Andresen, 2014). A source from Greenland has been suggested approach, the aims of this study are to (i) characterise the prove- for some parts of the Triassic on Svalbard (Mørk, 1999) which may nance signatures of Triassic sandstones on the southwest Barents also have provided sediment to the southwest Barents Shelf Shelf; (ii) map the distribution of sand types to reconstruct the (Glørstad-Clark et al., 2010). drainage distribution; and finally (iii) compare the provenance data Shelfal environments, such as those that characterise the with published data from the greater Barents Shelf in order to Triassic on the Barents Shelf, can have a complex source-to-sink provide insight into the wider tectonic evolution and location of system as they are capable as acting both as sediment sources sedimentary source regions. The outcomes of this work enable (e.g. wave ravinement), transporters (e.g. longshore drift) and sinks more precise constraints on the location and composition of (Sømme et al., 2009). These processes have the ability to cause local Triassic sandstones on the Barents Shelf, which may be used to provenance variation and are therefore an important consideration reduce uncertainty in reservoir prediction. during analysis. However, the majority of the samples in this study were collected from deltaic facies formed during the rapid pro- 2. Geological background gradation of the clinoform belts (Klausen et al., 2015). As such, significant mixing and erosion of different source areas either by The Barents Shelf is subdivided into numerous basins, platforms tides, waves or through long shore drift was probably minor at the and highs (Fig. 1a; Gabrielsen et al., 1990). To the east, the regional scale examined. structure is dominated by a major basin, located west of Novaya Zemlya, called the East Barents Basin. Westwards, there is a sig- 3. Methods nificant change in structural style, and a series of relatively narrow, predominantly northeast-southwest trending, elongate exten- Point counting of thin sections, stained for porosity and K- sional basins are present (Gernigon et al., 2014). Deposition was feldspar, and conventional heavy mineral analysis followed the initiated due to Late Palaeozoic collapse of the Caledonian moun- methods outlined by Folk (1980) and Mange and Wright (2007), tain belt. This was followed by rift-related subsidence and the respectively. The provenance-sensitive heavy mineral ratios ATi development of the North Atlantic rift system (Dore, 1992). Rapid (apatite:tourmaline index), GZi (garnet:zircon index), RuZi (ruti- subsidence occurred in the North and South Barents basins to the le:zircon index), MZi (monazite:zircon index) and CZi (chrome- east during the Late Permian and continued through the Triassic spinel:zircon index) were determined following Morton and resulting in the creation of a large epicontinental seaway (Smelror Hallsworth (1994). Garnet geochemical analyses were performed et al., 2009). using a Link Systems AN 10/55S energy-dispersive x-ray analyser On the southwest Barents Shelf, a total thickness in excess of attached to a Cambridge Instruments Microscan V electron 2.5 km was deposited in the Triassic, which has been divided into 5 microprobe housed at the University of Aberdeen. Garnet assem- lithostratigraphic formations (Havert, Klappmyss, Kobbe, Snadd blages have been compared by determining the relative abun- and Fruholmen formations; Fig. 1b). Each of these can be related to dances of garnet types A (low-Ca, high-Mg), B (low-Mg, variable- a transgressive-regressive cycle, bounded by a maximum flooding Ca) and C (high-Mg, high-Ca), as defined by Mange and Morton surface (MFS) (Glørstad-Clark et al., 2010; Henriksen et al., 2011; (2007). Rutile chemical analyses were carried out at the School of Klausen et al., 2015). Significant seaward shifts of the shoreline Earth, Ocean and Planetary Sciences at Cardiff University, using a can be recognised seismically (Glørstad-Clark et al. 2010, 2011; Thermo Elemental X(7) series inductively coupled mass spec- Klausen et al., 2015). These reflect regression and the trometer (ICP-MS) coupled to a New Wave Research UP213 Nd:YAG Fig. 1. (a) Map of the Barents Shelf showing the location of wells used in this paper (tectonic elements after Gabrielsen et al., 1990). (b) Chronostratigraphy and facies summary of the Triassic stratigraphy on Svalbard and the western Barents Shelf. Facies interpretations are compiled and adapted after Henriksen et al. (2011), Lundschien et al. (2014), Mørk and Elvebakk (1999), Rød et al. (2014) and Vigran et al. (2014). Lithostratigraphy is after Mørk et al. (1999) with adaptations from Mørk et al. (2013). Maximum flooding surfaces are after Glørstad-Clark et al. (2010) and Klausen et al. (2015). The sea level curve is modified after Haq et al. (1987) and Golonka and Ford (2000). E.J. Fleming et al. / Marine and Petroleum Geology 78 (2016) 516e535 519

213 nm UV laser. The rutile chemical data were used to determine 4.2. Heavy mineral data the proportion of metamafic and metapelitic rutiles following Meinhold et al. (2008) and their temperature of formation using Seventy-two samples were selected for conventional heavy the Zr-in-rutile thermometer of Watson et al. (2006). mineral analysis (Table 1). The results are aligned with the temporal Detrital zircon U-Pb geochronology was performed using either and spatial changes recognised in the petrographic data. In the laser ablation single collector magnetic sector field inductively Havert, Klappmyss, Kobbe and Snadd formations, strong coupled plasma mass spectrometry (LA-SF-ICP-MS) or secondary geographic variation is seen in the heavy mineral characteristics. ionisation mass spectrometry (SIMS). Geochronology using LA-SF- Samples collected from the southern part of the Hammerfest Basin ICP-MS was carried out at the Central Analytical Facility of Stel- are commonly dominated by garnet (77%), with minor zircon (12%), lenbosch University with a Thermo Finnigan Element 2 mass tourmaline (5%) and apatite (4%) (Fig. 3c). In contrast, samples from spectrometer coupled to a NewWave UP213 laser ablation system. elsewhere contain a more diverse heavy mineral assemblage SIMS dating was carried out by using either a Cameca 1270 ion dominated by apatite (49%), including relatively high proportions microprobe at the NORDSIM facility housed at the Swedish of tourmaline (7%), chrome-spinel (6%), chloritoid (5%), epidote Museum of Natural History, Stockholm or a SHRIMP RG instrument (3%) and titanite (2%). Garnet is only a minor constituent (14%) and at the Australian National University in Canberra, Australia. The is absent in samples from the Bjørnøya Basin. Zircon contents are ICP, Cameca 1270 and SHRIMP analytical methods closely variable (x ¼ 14%) and increase up stratigraphy. Samples from the followed those outlined by Frei and Gerdes (2009) and Whitehouse Havert Formation from one well in the Nordkapp Basin display and Kamber (2005) and Williams (1998), also see supplementary unusually high proportions of epidote and titanite. material. Cross plots of the provenance-sensitive heavy mineral ratios for the Havert, Klappmyss, Kobbe and Snadd formations are shown in Fig. 3a i-a.iii. Distinct differences in these ratios are observed be- 4. Results tween samples from the southern part of the Hammerfest Basin and those from elsewhere. Of particular note, CZi is uniformly low 4.1. Petrography in samples from the southern part of the Hammerfest Basin (<1). In contrast, CZi ratios from other areas are variable but normally Thirty-nine samples were selected for petrographic analysis significantly higher (e.g. 55 in Sample 7228_7-1A_2059.3 from the (Table 1). A wide range of compositions are encountered which Nordkapp Basin). Similarly, the southern Hammerfest Basin dis- show both spatial and temporal variation (Fig. 2). In the Havert, plays high GZi (x ¼ 84) and RuZi (x ¼ 42) ratios but relatively low Klappmyss, Kobbe and Snadd formations (Fig. 1b), strong ATi (x ¼ 47) compared to the remaining areas. geographic variation is seen in the petrographic characteristics. A distinct change in the heavy mineral assemblage is seen across Samples from the southern part of the Hammerfest Basin are the boundary between the Snadd and the Fruholmen formations. classified as sub-arkoses (Fig. 2a) and are generally compositionally Across this boundary, an increase in the average proportion of mature. The relative proportions of quartz, plagioclase, K-feldspar ultrastable heavy minerals e.g. zircon (42%), and tourmaline (20%) and rock fragments are shown in Fig. 2c. The samples contain an and fewer less stable minerals such as apatite (11%) and garnet (6%) average of 79% quartz, with minor plagioclase (10%), K-feldspar (5%) are apparent (Fig. 3d). Geographic variation is also seen within the and rock fragments. These rock fragments are predominantly Fruholmen Formation. Samples from Well 7122/7-4s and 7122/7-1 plutonic with minor metamorphic and sedimentary grains. The in the Hammerfest Basin (south) display an unusually high pro- reservoir quality is generally good or excellent, with visible po- portion of kyanite. In addition, samples in the Bjørnøya Basin rosities ranging from 0 to 30%, with a mean (x) of 14%. In contrast, display large amounts of apatite and chrome-spinel. away from the southern part of the Hammerfest Basin, samples are Cross plots of the provenance-sensitive heavy mineral ratios for compositionally immature and can be classified as arkoses, lithic the Fruholmen Formation are shown in Fig. 3b i-b.iii. In contrast to arkoses and arkose litharenites (Fig. 2a). On average, samples the underlying formations, the samples are characterised by low from these areas contain a lower proportion of quartz (54%) and ATi (x ¼ 14) and CZi (x ¼ 4) values across the study area. The K-feldspar (2%), but a higher proportion of plagioclase (19%) notable exception to this pattern comes from the Bjørnøya Basin and rock fragments (25%) (Fig. 2c). The rock fragments are where high CZi and ATi values are retained. These Bjørnøya Basin mostly sedimentary (mudstone and sandstone) or metamorphic, Fruholmen Formation samples fall into distinct fields on the with subordinate plutonic grains. The reservoir quality is RuZi:ATi, RuZi:CZi and GZi:ATi cross plots. variable, with visible porosities ranging from 0 to 20%, with an average of 7%. 4.3. Garnet geochemistry A major petrographic shift occurs across the boundary between the Snadd and the Fruholmen formations (Fig. 2) at the Early Norian A subset of 8 samples was selected for garnet geochemical MFS. Above this boundary, a marked increase in compositional analysis (Table 1). Garnet geochemistry can be a particularly useful maturity is seen in all areas. The sandstone compositions become mineral-chemical tool due its common occurrence in heavy min- dominated by quartz (94%), with low proportions of K-feldspar eral assemblages, relative stability during both weathering and (1%), plagioclase feldspar (3%) and rock fragments (2%) (Fig. 2c). Of diagenesis, and its wide range of major element compositions (see particular note are samples from the south Hammerfest Basin Mange and Morton (2007) for review). Although the results are not which show extreme compositional maturity. Elsewhere, maturity as distinct as the other provenance techniques, some spatial vari- is variable, but extreme compositional maturity is also seen in some ability can be seen between the samples. Samples from the samples from the Nyslepp/Måsøy Fault Complex (e.g. samples southern part of the Hammerfest Basin (Fig. 4a, b and c) are typi- 7124_3-1_1349.35 and 7124_3-1_1355.4). Others display slighter cally moderately pyrope-rich and spessartine-poor and have a high greater immaturity (e.g. 7125_4-1_904.5). Rock fragments, where proportion of Type Aii garnets, suggesting a derivation from high- present, are mostly sedimentary (65%; mudstone and sandstone) grade granulite-facies metasediments. In contrast, samples from and plutonic and volcanic fragments are low in abundance (9%). other areas such as the Finnmark Platform (Fig. 4e) and Nordkapp The reservoir quality is generally good or excellent, with porosities Basin (Fig. 4f, g and h) are typically more pyrope-poor and ranging from 5 to 30%, with an average of 19%. spessartine-rich and most grains tend to plot within in the Type Bi 520 E.J. Fleming et al. / Marine and Petroleum Geology 78 (2016) 516e535

Table 1 Samples data table.

Sample No Formation Latitude Longitude Region Provenance Petrography HM garnet rutile zircon

7120_12-1_3521.7 Kobbe 71.11353 20.75559 Hammerfest Basin (south) Caledonian CC 7121_5-1_3097.4 Snadd 71.59858 21.40605 Hammerfest Basin (north) Uralian C 7122_6-1_2065.4 Fruholmen 71.63870 22.81189 Hammerfest Basin (north) Caledonian CC 7122_6-1_2093.4 Fruholmen 71.63870 22.81189 Hammerfest Basin (north) Caledonian CC 7122_6-2_2499.9 Snadd 71.58711 22.85598 Hammerfest Basin (north) Uralian C 7122_7-1_1141.3 Fruholmen 71.28637 22.31862 Hammerfest Basin (south) Caledonian CC 7122_7-1_1148.5 Fruholmen 71.28637 22.31862 Hammerfest Basin (south) Caledonian C 7122_7-1_1153.5 Fruholmen 71.28637 22.31862 Hammerfest Basin (south) Caledonian CC 7122_7-1_1162.4 Fruholmen 71.28637 22.31862 Hammerfest Basin (south) Caledonian CCC 7122_7-1_1163.7 Fruholmen 71.28637 22.31862 Hammerfest Basin (south) Caledonian CC 7122_7-1_1169.5 Fruholmen 71.28637 22.31862 Hammerfest Basin (south) Caledonian C 7122_7-1_1173.6 Fruholmen 71.28637 22.31862 Hammerfest Basin (south) Mixed C 7122_7-3_1187.8 Snadd 71.25487 22.26794 Hammerfest Basin (south) Caledonian CC 7122_7-3_1813.2 Kobbe 71.25487 22.26794 Hammerfest Basin (south) Caledonian C 7122_7-3_1821.7 Kobbe 71.25487 22.26794 Hammerfest Basin (south) Caledonian C 7122_7-3_1828.8 Kobbe 71.25487 22.26794 Hammerfest Basin (south) Caledonian C 7122_7-3_2520.2 Havert 71.25487 22.26794 Hammerfest Basin (south) Caledonian CCCC 7122_7-4S_1185.5 Fruholmen 71.25363 22.31817 Hammerfest Basin (south) Caledonian CC 7122_7-4S_1194.3 Fruholmen 71.25363 22.31817 Hammerfest Basin (south) Caledonian C 7122_7-4S_1198.5 Fruholmen 71.25363 22.31817 Hammerfest Basin (south) Caledonian CC 7122_7-4S_1210.5 Fruholmen 71.25363 22.31817 Hammerfest Basin (south) Caledonian CC C 7122_7-4S_1805.5 Kobbe 71.25363 22.31817 Hammerfest Basin (south) Caledonian CC C C 7122_7-4S_1811.4 Kobbe 71.25363 22.31817 Hammerfest Basin (south) Caledonian C 7122_7-4S_1817.9 Kobbe 71.25363 22.31817 Hammerfest Basin (south) Caledonian CCC 7122_7-4S_1885.4 Kobbe 71.25363 22.31817 Hammerfest Basin (south) Caledonian CC 7122_7-4S_2057.9 Klappmyss 71.25363 22.31817 Hammerfest Basin (south) Caledonian CCC 7122_7-5_1902.3 Kobbe 71.27353 22.27790 Hammerfest Basin (south) Caledonian CC 7122_7-5_1908.6 Kobbe 71.27353 22.27790 Hammerfest Basin (south) Caledonian CC 7124_3-1_1316.4 Fruholmen 71.76001 24.78055 Nyslepp/Måsøy Fault ComplexNyslepp/ Caledonian CC CC Måsøy Fault ComplexNyslepp/Måsøy Fault ComplexNyslepp/Måsøy Fault Complex 7124_3-1_1337.5 Fruholmen 71.76001 24.78055 Nyslepp/Måsøy Fault ComplexNyslepp/ Mixed CC Måsøy Fault ComplexNyslepp/Måsøy Fault ComplexNyslepp/Måsøy Fault Complex 7124_3-1_1349.35 Fruholmen 71.76001 24.78055 Nyslepp/Måsøy Fault ComplexNyslepp/ Caledonian CCC Måsøy Fault ComplexNyslepp/Måsøy Fault Complex 7124_3-1_1350 Fruholmen 71.76001 24.78055 Nyslepp/Måsøy Fault ComplexNyslepp/ Caledonian C Måsøy Fault ComplexNyslepp/Måsøy Fault Complex 7124_3-1_1355.4 Fruholmen 71.76001 24.78055 Nyslepp/Måsøy Fault ComplexNyslepp/ Caledonian CC Måsøy Fault ComplexNyslepp/Måsøy Fault Complex 7124_3-1_1380.3 Fruholmen 71.76001 24.78055 Nyslepp/Måsøy Fault ComplexNyslepp/ Mixed C Måsøy Fault ComplexNyslepp/Måsøy Fault Complex 7124_3-1_1403.7 Fruholmen 71.76001 24.78055 Nyslepp/Måsøy Fault ComplexNyslepp/ Caledonian C Måsøy Fault ComplexNyslepp/Måsøy Fault Complex 7125_4-1_889.0 Fruholmen 71.55017 25.23951 Nyslepp/Måsøy Fault ComplexNyslepp/ Caledonian C Måsøy Fault ComplexNyslepp/Måsøy Fault Complex 7125_4-1_904.5 Fruholmen 71.55017 25.23951 Nyslepp/Måsøy Fault ComplexNyslepp/ Mixed CC Måsøy Fault ComplexNyslepp/Måsøy Fault Complex 7131_4-1_1080.5 Snadd 71.69472 31.01138 Finnmark Platform Uralian CCC 7131_4-1_1100.1 Snadd 71.69472 31.01138 Finnmark Platform Uralian CC 7131_4-1_920.1 Fruholmen 71.69472 31.01138 Finnmark Platform Caledonian C 7131_4-1_941.5 Fruholmen 71.69472 31.01138 Finnmark Platform Caledonian CC C 7219_9-1_2747.4 Fruholmen 72.40022 19.95324 Bjørnøya BasinBjørnøya BasinBjørnøya Mixed CC CC Basin 7219_9-1_2760.4 Fruholmen 72.40022 19.95324 Bjørnøya BasinBjørnøya BasinBjørnøya Mixed C Basin 7224_7-1_1725.8 Kobbe 72.28509 24.30083 Bjarmeland Platform Uralian CC 7224_7-1_1734.3 Kobbe 72.28509 24.30083 Bjarmeland Platform Uralian CC 7226_11-1_2141.7 Kobbe 72.23838 26.47911 Nordkapp Basin Uralian CC 7226_11-1_3058.3 Havert 72.23838 26.47911 Nordkapp Basin Uralian C 7226_11-1_3067.5 Havert 72.23838 26.47911 Nordkapp Basin Uralian CCC 7226_11-1_3079.2 Havert 72.23838 26.47911 Nordkapp Basin Uralian CC 7228_2-1_4190.4 Havert 72.85271 28.44156 Bjarmeland Platform Uralian C 7228_7-1A_2059.3 Snadd 72.25803 28.14992 Nordkapp Basin Uralian CC C C 7228_7-1A_2062.1 Snadd 72.25803 28.14992 Nordkapp Basin Uralian CCCC E.J. Fleming et al. / Marine and Petroleum Geology 78 (2016) 516e535 521

Table 1 (continued )

Sample No Formation Latitude Longitude Region Provenance Petrography HM garnet rutile zircon

7228_7-1A_2062.1b Snadd 72.25803 28.14992 Nordkapp Basin Uralian C 7228_7-1A_2073.4 Snadd 72.25803 28.14992 Nordkapp Basin Uralian C 7228_7-1A_2090 Snadd 72.25803 28.14992 Nordkapp Basin Uralian C 7228_7-1A_2096.2 Snadd 72.25803 28.14992 Nordkapp Basin Uralian C 7228_7-1A_2846.6 Klappmyss 72.25803 28.14992 Nordkapp Basin Uralian CC 7228_7-1A_2858.7 Klappmyss 72.25803 28.14992 Nordkapp Basin Uralian CC 7228_9-1S_2871.6 Havert 72.39677 28.71908 Finnmark Platform Uralian CC 7321_7-1_2387.7 Snadd 73.43210 21.07549 Bjørnøya Basin Uralian CC 7321_8-1_1480 Fruholmen 73.33666 21.41591 Bjørnøya BasinBjørnøya Basin Mixed C 7321_8-1_1510 Fruholmen 73.33666 21.41591 Bjørnøya BasinBjørnøya Basin Mixed C 7321_8-1_1538.1 Fruholmen 73.33666 21.41591 Bjørnøya Basin Mixed C 7321_8-1_2840.6 Snadd 73.33666 21.41591 Bjørnøya Basin Uralian CC 7324_10-1_1664.4 Kobbe 73.16374 24.31323 Bjarmeland Platform Uralian C 7324_10-1_1666.8 Kobbe 73.16374 24.31323 Bjarmeland Platform Uralian C 7324_10-1_2640.4 Havert 73.16374 24.31323 Bjarmeland Platform Uralian CC 7324_10-1_2653.7 Havert 73.16374 24.31323 Bjarmeland Platform Uralian C 7324_10-1_2656.3 Havert 73.16374 24.31323 Bjarmeland Platform Uralian CC

or Type B fields on the discrimination diagram of Mange and abundant grains with Permian and Carboniferous ages between Morton (2007), suggesting more of a derivation from amphibolite 280 Ma and 370 Ma. A minor population of Late Neoproterozoic/ facies metasediments. In the Fruholmen Formation, sample Early Cambrian ages between 520 Ma and 570 Ma was also recor- 7124_3-1_1349.35 (Fig. 4d) from the Nyslepp/Måsøy Fault Complex ded. Grains with older Proterozoic and Archaean ages are rare. has a mixed garnet geochemistry, with garnets plotting within the In the Fruholmen Formation, the ages of detrital zircons were Type Ai, Aii B and Bi fields. measured on 4 samples: Sample 7219_9-1_2747.4 (Fig. 6e) is from the Bjørnøya Basin, Sample 7122_7-1_1162.4 (Fig. 6f) is from the 4.4. Rutile geochemistry southern part of the Hammerfest Basin and samples 7124_3- 1_1316.4 (Fig. 6g) and 7124_3-1_1349.35 (Fig. 6h) are from the Detrital rutile geochemical data were obtained from 10 samples Nyslepp/Måsøy Fault Complex. A diverse zircon age spectrum (Table 1 and Fig. 5). In the southern part of the Hammerfest Basin, containing significant Carboniferous c. 340 Ma and Late Neo- samples from the Havert (7122_7-3_2520.2) and Kobbe formations proterozoic 550e600 Ma populations was observed in the sample (7122_7-4s_1805.5 and 7122_7-4s_1817.9) have predominantly from the Bjørnøya Basin (Sample 7219_9-1_2747.4). In contrast metapelitic rutiles (x ¼ 68%) and have an average crystallisation grains younger than 900 Ma are rare or absent in the other samples. temperature of 640 C. In contrast, samples from the Kobbe Instead, these samples have grains which yield a spread of Meso- (7224_7-1_1725.8) and Snadd formations (7228_7-1A_2059.3) proterozoic and Palaeoproterozoic ages with a significant zircon situated away from the southern part of the Hammerfest Basin have population at c. 1640 Ma. dominantly metamafic rutiles (x ¼ 79%) and a slightly lower calculated average crystallisation temperature of 615 C. Samples 5. Provenance interpretation of the Barents Shelf Triassic from the Fruholmen Formation display variable rutile varieties with succession mean crystallisation temperatures similar to those from other Triassic formations. Through the integration of the petrographic analyses, heavy mineral analyses, single grain garnet and rutile geochemical ana- 4.5. Detrital zircon U-Pb geochronology lyses and detrital zircon U-Pb geochronology, it is possible to identify different sand types. Within the Havert, Klappmyss, Kobbe U-Pb detrital zircon geochronology was carried out on 8 sam- and Snadd formations, two contrasting groups of samples are seen ples (Table 1). In addition to the histogram and probability dia- in the provenance results (Fig. 7), as summarised and interpreted in grams displayed on Fig. 6, the data are given as the percentages the following sections. within key age ranges are given in the supplementary materials, and these further highlight similarities and differences between the 5.1. Pre-Early Norian Triassic sand types samples. Two samples were analysed from the Kobbe Formation in the 5.1.1. The Caledonian Sand Type southern part of the Hammerfest Basin. Sample 7122_7-4s_1805.5 A distinct group of samples is seen from wells that are located in and 7122_7-4s_1817.9 (Fig. 6a and b) display a broad Proterozoic the southern Hammerfest Basin. They are characterised by a high zircon age distribution. A significant Late Neoproterozoic (c. 600 degree of compositional maturity (Fig. 7c). They have a low pro- Ma) population is recorded in both samples. Other Mesoproterozoic portion of rock fragments, which are mostly plutonic in origin, and populations are recorded between 1000 Ma and 1250 Ma and a the reservoir quality is generally good or excellent, with mean broad Palaeoproterozoic age distribution are seen between 1500 visible porosity at 14%. The heavy mineral assemblage in these Ma and 1800 Ma. Finally, a minor Archaean population is observed samples is dominated by garnet, and chrome-spinel contents are in both samples. low resulting in high GZi values and CZi values at or close to zero In the Snadd Formation, detrital zircon age analysis was carried (Fig. 7a). Rutiles have compositions consistent with a metapelitic out on 2 samples 7228_7-1A_2059.25 and 7228_7-1A_2062.1 from source (Fig. 7d) and most of the detrital garnets plot within the the Nordkapp Basin (Fig. 6c and d). Both yield broadly similar Type A fields (Fig. 7b). The detrital zircon spectrum (Fig. 7e) dis- detrital zircon age spectra. In contrast to the Kobbe Formation in plays a significant Late Neoproterozoic population, in addition to the southern part of the Hammerfest Basin, the samples contain older Meso and Palaeoproterozoic and Archaean populations; Loca Q Q (a) (b) Hammerfest Basin (south) Quartz Hammerfest Basin (central and north) Arenite Nyslepp/Måsøy Fault Complex litharenite Bjarmeland Pla orm

Sub- Nordkapp Basin Sub- Bjørnøya Basin arkose Finmark Pla orm Forma Fruholmen Havert Q Q Klappmyss Quartz Kobbe Arenite Snadd

litharenit

Sub-

Ark ose

Post-Early Sub- ose lithar ark Norian MFS e Lithar

enite enite

Arkose Lithic arkose

FKPK

Pre-Early Ark Norian MFS ose litharenit

Lithar

enite

e

Arkose Lithic arkose

FRP K (c) 7122_7-1_1141.3 7122_7-1_1153.5 7122_7-1_1163.7 7122_7-4S_1185.5 Hammerfest Basin (south) 7122_7-4S_1198.5 7122_7-4S_1210.5 7122_6-1_2065.4 Hammerfest Basin Fruholmen Fm. 7122_6-1_2093.4 (central and north) 7124_3-1_1337.5 7124_3-1_1349.35 Nyslepp/Måsøy 7124_3-1_1355.4 Fault Complex 7124_3-1_1380.3 7125_4-1_904.5 7219_9-1_2747.4 Bjørnøya Basin 7131_4-1_941.5 Finnmark Pla orm

7122_7-3_1187.8 Hammerfest Basin (south) 7121_5-1_3097.4 Hammerfest Basin 7122_6-2_2499.9 (central and north) 7228_7-1A_2062.1 Snadd Fm. 7228_7-1A_2096.2 Nordkapp Basin 7321_7-1_2387.7 7321_8-1_2840.6 Bjørnøya Basin 7131_4-1_1080.5 7131_4-1_1100.1 Finnmark Pla orm

7120_12-1_3521.7 7122_7-4S_1885.4 7122_7-5_1902.3 Hammerfest Basin (south) Kobbe Fm. 7122_7-5_1908.6 7224_7-1_1734.3 Bjarmeland Pla orm 7226_11-1_2141.7 Nordkapp Basin

7122_7-4S_2057.9 Hammerfest Basin (south) Klappmyss Fm. 7228_7-1A_2846.6 7228_7-1A_2858.7 Nordkapp Basin

7122_7-3_2520.2 Hammerfest Basin (south) 7324_10-1_2656.3 Bjarmeland Pla orm 7226_11-1_3067.5 Havert Fm. 7226_11-1_3079.2 Nordkapp Basin 7324_10-1_2640.4 Bjørnøya Basin 7228_9-1S_2871.6 Finnmark Pla orm 0 % 10 % 20 % 30 % 40 % 50 % 60 % 70 % 80 % 90 % 100 % Quartz Plagioclase Alkali Feldspar Rock Fragments

Fig. 2. Petrographic analysis of sandstone samples from the Triassic formations. a) Ternary diagram showing the relative proportions of quartz (Q), feldspar (F) and rock fragments (R) with fields representing the sandstone classification of Folk (1980). b) Ternary diagram showing the relative proportions of quartz (Q), plagioclase feldspar (P) and K-feldspar (K). The upper plots show data from the Fruholmen Formation only, whereas the lower plots shows data from the other formations. c) Normalised stacked bar charts showing the relative proportions of quartz, plagioclase, K-feldspar and rock fragments. (a. i) (a. ii) (a. iii) ATi vs. RuZi CZi vs. RuZi ATi vs. GZi 100 100 100 Pre-Early Norian MFS 80 80 80

60 60 60 GZi RuZi RuZi 40 40 40

20 20 20

0 0 0 0 20 40 60 80 100 0 10 20 30 40 50 60 0 20 40 60 80 100 ATi CZi ATi (b. i) (b. ii) (b. iii) 100 100 100 Post-Early Forma Norian MFS Fruholmen 80 80 80 Havert Klappmyss 60 60 60 Kobbe Snadd GZi RuZi RuZi 40 40 40

20 20 20

0 0 0 0 20 40 60 80 100 0 10 20 30 40 50 60 0 20 40 60 80 100 ATi CZi ATi (c) 7122_7-1_1141.3 7122_7-1_1148.5 7122_7-1_1153.5 7122_7-1_1162.4 7122_7-1_1163.7 7122_7-1_1169.5 Hammerfest Basin (south) 7122_7-1_1173.6 7122_7-4S_1185.5 7122_7-4S_1194.3 7122_7-4S_1198.5 7122_7-4S_1210.5 7122_6-1_2065.4 Hammerfest Basin 7122_6-1_2093.4 (central and north) Fruholmen Fm. 7124_3-1_1316.4 7124_3-1_1337.5 7124_3-1_1350 7124_3-1_1355.4 Nyslepp/Måsøy 7124_3-1_1403.7 Fault Complex 7125_4-1_889.0 7125_4-1_904.5 7219_9-1_2747.4 7219_9-1_2760.4 7321_8-1_1480 Bjørnøya Basin 7321_8-1_1510 7321_8-1_1538.1 7131_4-1_920.1 Finnmark Pla orm 7131_4-1_941.5 7122_7-3_1187.8 Hammerfest Basin (south) 7121_5-1_3097.4 Hammerfest Basin 7228_7-1A_2059.3 (central and north) 7228_7-1A_2062.1 7228_7-1A_2062.1b Nordkapp Basin Snadd Fm. 7228_7-1A_2073.4 7228_7-1A_2090 7321_7-1_2387.7 Bjørnøya Basin 7321_8-1_2840.6 7131_4-1_1080.5 Finnmark Pla orm 7131_4-1_1100.1 7120_12-1_3521.7 7122_7-3_1813.2 7122_7-3_1821.7 7122_7-3_1828.8 7122_7-4S_1805.5 Hammerfest Basin (south) 7122_7-4S_1811.4 7122_7-4S_1817.9 Kobbe Fm. 7122_7-4S_1885.4 7122_7-5_1902.3 7122_7-5_1908.6 7224_7-1_1725.8 7224_7-1_1734.3 Bjarmeland Pla orm 7324_10-1_1664.4 7324_10-1_1666.8 7226_11-1_2141.7 Nordkapp Basin 7122_7-4S_2057.9 Hammerfest Basin (south) Klappmyss Fm. 7228_7-1A_2846.6 Nordkapp Basin 7228_7-1A_2858.7 7122_7-3_2520.2 Hammerfest Basin (south) 7228_2-1_4190.4 7324_10-1_2653.7 Bjarmeland Pla orm 7324_10-1_2656.3 Havert Fm. 7226_11-1_3058.3 7226_11-1_3067.5 Nordkapp Basin 7226_11-1_3079.2 7324_10-1_2640.4 Bjørnøya Basin 7228_9-1S_2871.6 Finnmark Pla orm 0 % 10 % 20 % 30 % 40 % 50 % 60 % 70 % 80 % 90 % 100 % Apa e Anatase Calcic amphibole Clinopyroxene Chrome spinel Chloritoid Epidote Gahnite Garnet Kyanite Monazite Titanite Staurolite Tourmaline Zircon

Fig. 3. Heavy mineral characteristics of the Triassic formations. Cross plots of the heavy mineral ratios for samples from the pre (a) and post (b) Early Norian MFS showing (i) RuZi:ATi, (ii) RuZi:CZi and (iii) GZi:ATi. c) Normalised stacked bar charts showing the heavy mineral assemblage. 524 E.J. Fleming et al. / Marine and Petroleum Geology 78 (2016) 516e535

Fig. 4. eTernary diagram of garnet compositions showing the relative proportions of Pyrope (XMg), Grossular (XCa) and Almandine- Spessartine (XFeþMg) garnets. Filled symbols ¼ XMn > 5%. Also shown are pie charts with the relative portion of the different garnet types according to the subdivisions of Mange and Morton (2007). however, Palaeozoic zircons are absent. Northern scandinavia. The grouping is referred to as the Caledonian The broad detrital zircon age spectrum, combined with the Sand Type despite the absence of grains with ages that coincide geographic distribution of these samples, suggests a source from with the main Caledonian magmatic and tectonic events (Bingen E.J. Fleming et al. / Marine and Petroleum Geology 78 (2016) 516e535 525

Fig. 5. Rutile geochemistry of the analysed samples showing the relative abundance of metapelitic and metamafic rutile and their peak metamorphic temperatures. Discrimination of rutile provenance (metamafic or metapelitic) is after Meinhold et al. (2008) and the temperature calculations are from Watson et al. (2006).

and Solli, 2009). This is because in northern Scandinavia the orogen 5.1.2. The Uralian Sand Type contains few felsic Palaeozoic intrusions but is instead formed of A second group of samples is present with provenance charac- thick Neoproterozoic and Early Palaeozoic successions of the teristics that are distinct from those from the Caledonian Sand Caledonian Allochthons and Autochthons (Sturt and Austrheim, Type. These samples come from wells that are located in areas 1985). It is thought that many of the grains were recycled from north of the southern part of the Hammerfest Basin and are char- these units because the combined signal from the Caledonian acterised by low compositional maturity (Fig. 7c). The reservoir successions yields a detrital zircon pattern that is most similar to properties are quite variable, with an average visible porosity of 7%. the offshore samples (Fig. 8). The proportion of rock fragments is high and they are mostly of Fig. 6. Histogram of U-Pb ages and relative probability curve for detrital zircon. (i) 0-3.5Ga (50 Ma bin width) and (ii) 0e800 Ma (25 Ma bin width). Numbers above the probability curve equate to the approximate ages of the most significant zircon populations. The grey bars represent periods of magmatic and metamorphic activity within the Fennoscandian Shield and Caledonides of northern Norway. The red bars represent periods of magmatic and metamorphic activity within the Uralian Orogeny whilst the blue bars represent the Timanian Orogeny. The deeper colours represent higher zircon fertility. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) E.J. Fleming et al. / Marine and Petroleum Geology 78 (2016) 516e535 527

Fig. 7. Summary of the different characteristics of the Caledonian and Uralian sand types seen in the Havert, Klappmyss, Kobbe and Snadd Formations. a) Cross plots of the heavy mineral ratios for (i) RuZi:ATi, (ii) RuZi:CZi and (iii) GZi:ATi. b) Ternary diagram showing the relative proportions of Pyrope (XMg), Grossular (XCa) and Almandine- Spessartine (XFeþMg) garnets, using the subdivisions of Mange and Morton (2007). Filled symbols ¼ XMn > 5%. c) Ternary diagram showing the relative proportions of quartz (Q), feldspar (F) and rock fragments (R) with fields representing the sandstone classification of Folk (1980). d) Rutile geochemistry of the analysed samples showing the relative abundance of metapelitic and metamafic rutile and their peak metamorphic temperatures. e) Histogram of U-Pb ages and relative probability curve for detrital zircon. (i) Caledonian Sand Type and (ii) Uralian Sand Type (20 Ma bin width). The grey bars represent periods of magmatic and metamorphic activity within the Fennoscandian Shield and Caledonides of northern Norway (deeper colours represent higher zircon fertility). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) 528 E.J. Fleming et al. / Marine and Petroleum Geology 78 (2016) 516e535

(Glørstad-Clark et al., 2010; Klausen et al., 2014; Lundschien et al., 2014; Riis et al., 2008) are consistent with a source for this sand type from the Uralian Mountains and magmatic rocks associated with the Uralian Orogeny. The high chrome-spinel contents are from ultramafic rocks, present along the length of the origin (e.g. Ivanov et al., 2013). The important population of c. 310 Ma zircons may have originated from the continental arc rocks which occur within tectonic units which were accreted to the Siberian Craton (Fershtater, 2013; Fershtater et al., 2007; Smirnov et al., 2014). These units were exhumed during the suturing of Baltica with Siberia and the final phases of the Uralian Orogeny. The exact source area along the length of the Uralian Orogeny remains uncertain.

5.2. Post-Early Norian Triassic sand types

In the Havert to Snadd formations, a clear distinction is seen between the Caledonian and Uralian sand types. However, above the Early Norian MFS, a significant change in sandstone texture and composition occurs in the Fruholmen Formation. All geographic areas display an increase in compositional maturity and extreme compositional maturity is seen in some samples (Fig. 2a). Rock fragments are mostly sedimentary and reservoir properties are generally good or excellent. Samples display a large increase in the average proportion of ultra-stable heavy minerals (e.g. Zircon and tourmaline; Fig. 3c). As a consequence, ATi and CZi values are low (Fig. 3b i - b.iii). There is some geographical variation in composi- tion. Samples from the Bjørnøya Basin, in particular, are less mature and have a greater proportion of apatite and chrome-spinel and thus high CZi and ATi values, akin to those recorded from the Uralian Sand Type. The garnet geochemistry (Fig. 4) of samples from the Fruholmen Formation is a mixture between those seen in the Caledonian and Uralian sand types in older units with garnets falling in the Type Ai, Aii, B and Bi fields (Fig. 4d). Rutiles are mostly metapelitic (Fig. 5). The zircon signature of the Fruholmen Formation is variable (Fig. 6). Samples from the Hammerfest Basin and Nyslepp/Måsøy Fault Complex display abundant Mesoproterozoic and Palae- oproterozoic populations (Fig. 6f, g and h) which are typical of the Caledonian Sand Type and the (meta) sedimentary successions of northern Scandinavia. The sample from the Bjørnøya Basin (Fig. 6e) displays a much more mixed zircon age spectrum. In addition to the older populations, the sample displays two dominant younger peaks: one corresponding to the main Uralian Orogen seen within the Uralian Sand type and one resembling the Neoproterozoic Fig. 8. Histogram of U-Pb ages and relative probability curve for detrital zircons population evident within the Caledonian Sand Type of the comparing the data from this study on the southwest Barents Shelf for (a) the Cale- southern Hammerfest Basin. donian Sand Type deposited after the Norian Flooding surface with (b) Caledonian The conspicuous textural and compositional changes that occur Sand Type deposited prior to the Early Norian MFS, (c) the Barents Sea Group (Zhang between the Snadd and Fruholmen formations suggest a sharp et al., 2015), (d) the Neoproterozoic e Early Palaeozoic Paraautochthon and Autoch- thon of northern Norway (Andresen et al., 2014; Kirkland et al., 2008; Zhang et al., increase in the degree of weathering. Climate plays a major role in 2015) and (e) the Kalak Nappe Complex of north Norway (Kirkland et al., 2007, 2008). controlling weathering (Morton and Hallsworth, 1999); however, whilst there is a general trend to more humid climatic conditions in the Late Triassic Boreal Realm (Decou et al., 2016; Hochuli and sedimentary origin (mudstone and sandstone). These samples also Vigran, 2010), the changes in the zircon age spectra cannot easily have a distinct heavy mineral assemblage characterised by a low be attributed to climatic variations. Instead the data suggest that abundance of garnet but a high proportion of apatite and chrome- the Early Norian MFS marks the start of a change in provenance. spinel, which results in high CZi and ATi values (Fig. 7a). Most of the Major tectonic activity, such as the uplift of Novaya Zemlya detrital rutiles have metamafic compositions and a higher portion (Scott et al., 2010), is postulated in areas surrounding the Barents of the garnets fall in the Type B field compared with those from the Shelf in the Late Triassic. In addition, uplift and hinterland rejuve- Caledonian Sand Type. The detrital zircons are predominantly Late nation of the Finnmark Platform has been suggested by various Carboniferous and Permian in age (Fig. 7e). Proterozoic and authors (Mørk, 1999; Ryseth, 2014; Worsley, 2008). This would Archaean grains are much less abundant. have had a pronounced effect on the source-to-sink relationship of The occurrence of Permian and Carboniferous zircons and high the southwest Barents Shelf. A continued sediment input from the chrome-spinel contents, combined with the extensive seismic ev- Caledonian source area combined with the recycling of the un- idence of north-easterly prograding clinoforms in these areas derlying Uralian and/or Caledonian sand types in the Triassic due to E.J. Fleming et al. / Marine and Petroleum Geology 78 (2016) 516e535 529 the hinterland rejuvenation provides a likely explanation for the accompanied by a westward shift in the depocentre and subse- mixed signature seen in the Fruholmen Formation from the quently an eastward-thinning of sediment thickness, representing Bjørnøya Basin. a stepwise infilling of the western Barents Shelf (Glørstad-Clark By comparing the zircon spectrum from the Caledonian Sand et al., 2010). The shoreline extended over the top of the Loppa Type with that from the Fruholmen Formation (excluding the High and migrated westwards. The provenance results reveal that sample with a mixed signal from the Bjørnøya Basin), some dif- the two major fluvial systems continued to be active during this ferences are evident (Fig. 8). The zircon pattern from the Fruholmen time. Most of the western Barents Shelf was dominated by the Formation (Fig. 8a) closely resembles that from the Kalak Nappe major delta complexes that prograded from the southeast, resulting Complex (Fig. 8e), whereas the samples of the Caledonian Sand in the widespread deposition of the Uralian Sand Type. However, Type deposited before the Early Norian MFS (Fig. 8b) have a pattern the Caledonian Sand Type is seen in various samples in the Goliat more akin to a mixture of the signatures that characterise Kalak field area and further west in well 7120/12-1. These match the Nappe Complex and the Para-autochthon and Autochthon of the clinoform geometries in the Hammerfest Basin (Glørstad-Clark northern Fennoscandian Shield (Fig. 8d). A Kalak Nappe Complex et al., 2010) and imply a second fluvial system delivered the Cale- source for the Fruholmen Formation samples from the Hammerfest donian Sand Type to the southern Hammerfest Basin. Basin is consistent with their unusually high proportion of kyanite Progressive, stepwise infilling of the basin continued through because this nappe complex contains kyanite-bearing rocks the Ladinian and early Carnian (Fig. 10d). The depocentre shifts (Kirkland et al., 2007). By contrast, the increased proportions of west- and northwards, towards Hopen and the Edgeøya Platform apatite and chrome-spinel and Uralian-aged zircons in samples (Glørstad-Clark et al., 2010). Further south, a significant depocentre from the Bjørnøya Basin could be considered consistent with a first occurred over the top of the Loppa High and a westward migration cycle origin from the Uralian Orogeny. However, these samples are of the shoreline is observed. The exact position of the shoreline more compositionally mature than the typical Uralian Sand Type during this period is poorly constrained due to problems inter- and therefore more consistent with a recycled origin. preting clinoform geometries in the latest Carnian because of increasingly shallow water deposition. Whilst we place the shore- 6. Reconstruction of Triassic dispersal patterns line immediately west of the Loppa High (Fig. 10d), it is plausible that the epicontinental sea may have closed completely at times. Samples from each of the 5 main transgressive-regressive cycles The provenance results reveal that the two major fluvial systems are assigned a sand type and in combination with sedimentological continued to be active during this time; however, the system data from offshore boreholes and published seismic data (Høy and associated with the Uralian was clearly dominant as almost all of Lundschien, 2011; Klausen et al., 2014; Lundschien et al., 2014; Riis the samples from wells during this period show the Uralian Sand et al., 2008) sand dispersal reconstructions are made in Fig. 10. Type. One well from the Goliat field area (7122/7-3) displays the These reconstructions show the interpreted palaeogeography at Caledonian Sand Type, indicating that the second fluvial system maximum shoreline progradation with the shoreline positions still delivered sediment to the southern Hammerfest Basin. from the Induan to Norian are after Glørstad-Clark et al. (2010). A major provenance change occurs across the early Norian MFS The Induan (Fig. 10a) marks the start of the basin organisation (Fig. 10e) in response to basin reorganisation which coincided with that continued to the early Norian and developed following Late the development of the Slottet Bed in Svalbard (Mørk et al., 1999). Permian tectonic movements associated with the Uralian Orogeny. Up until this boundary, the Triassic was dominated by the Uralian Most of the wells analysed during this period display the Uralian Sand Type and the Caledonian Sand Type was restricted to the Sand Type, associated with the major deltaic complexes that orig- southern Hammerfest Basin. However, above this boundary the inated from the Uralian Orogen, depicted seismically from north- Caledonian Sand Type becomes dominant and supply of the Uralian westerly prograding clinoforms (Anell et al., 2014; Glørstad-Clark Sand Type is impeded. Hinterland rejuvenation resulted in wide- et al., 2010; Høy and Lundschien, 2011; Riis et al., 2008; van Veen spread sediment recycling and fluvial systems, sourced from the et al., 1993). One well (7122/7-3), restricted to the southern Kalak Nappe Complex in Finnmark, supplied sediment to extensive margin of the Hammerfest Basin, displays the Caledonian Sand regions over the Finnmark Platform and into more northerly areas. Type suggesting a second fluvial system delivered sand from Some samples display elevated CZi values and zircon ages associ- northern Scandinavia, supported by the presence of northward ated with the Uralian Orogeny. In most cases, these samples can be prograding clinoforms in the Induan (Glørstad-Clark et al., 2011; explained by mixing of the two sand types by recycling of an un- van Veen et al., 1993). derlying Uralian signature. The basin organisation continued during the Olenekian regres- sion (Fig. 10b). Clinoform geometries suggest the coastline reached 7. Comparisons with the De Geerdalen Formation in Svalbard as far as the eastern margins of the Loppa High (Glørstad-Clark et al., 2011). There is a slight shift of the depocentre towards the The De Geerdalen Formation in Svalbard is often used as an Bjarmeland Platform and minor progradation of the delta com- analogue for the Snadd Formation on the Barents Shelf (e.g. plexes towards the northwest. The provenance results reveal that Harishidayat et al., 2015; Klausen and Mørk, 2014; Lord et al., the two major fluvial systems continued to be active during this 2014b). It was initially thought to have been sourced from the time. Most of the wells display the Uralian Sand Type. However, one northeast, possibly from an area of land not currently exposed but well (7122/7-4s), in the southern Hammerfest Basin, displays the thought to have existed in the Mesozoic, known as Crockerland Caledonian Sand Type implying a second fluvial system delivered (Embry, 1993). However, recent seismic evidence has identified sand from northern Scandinavia, probably corresponding to the north-westerly prograding clinoforms offshore Svalbard and else- northward prograding clinoform belts seen in the Hammerfest where on the Barents Shelf (Høy and Lundschien, 2011; Riis et al., Basin (e.g. Glørstad-Clark et al., 2010). Further east, northward 2008). As such, deposition of the De Geerdalen Formation in Sval- prograding clinoforms are also observed on the Finnmark Platform bard is widely interpreted to have been associated with these (Glørstad-Clark et al., 2011) and these systems probably also south-easterly sourced prograding units (Lundschien et al., 2014; delivered the Caledonian Sand Type to these areas although this Rød et al., 2014). cannot be proven with the present sample and well coverage. The detrital zircon age data for the De Geerdalen Formation The Anisian to early Ladinian sequence (Fig. 10c) was (Fig. 9b) reveals a ~300 Ma population which corresponds with the 530 E.J. Fleming et al. / Marine and Petroleum Geology 78 (2016) 516e535

Fig. 9. Histogram of U-Pb ages and relative probability curve for detrital zircons comparing the data from this study on the southwest Barents Shelf for (a) the Uralian Sand Type with (b) data from Svalbard (Festningen, Hopen and Edgeøya; Pozer Bue and Andresen, 2014) and (c) data from Franz Josef Land (Soloviev et al., 2015). Numbers above the probability curve equate to the approximate ages of the most significant zircon populations.

main Uralian Orogeny and matches the dominant population northeast. recorded in the Snadd Formation from the southwest Barents Shelf. However, significant c. 235e240 Ma and c. 420e470 Ma zircon age 8. Implications for the tectonic evolution of the Barents Shelf populations are also seen. Zircons of this age are unusual as they are largely absent from the samples on the southwest Barents Shelf The data are placed within a wider sedimentary provenance (Fig. 9a) and sources for these zircons are not currently evident diagram for maximum regression in the early Norian in Fig. 11. The within the Uralian Orogen or Novaya Zemlya. Similar populations results have several important implications for the tectonic devel- are observed in Late Triassic samples from Franz Josef Land (Fig. 9c) opment of the Barents Shelf, particularly surrounding the timing and the age spectra in these areas can be considered cognate. and development of Novaya Zemlya. Until the early Norian, sedi- A possible explanation is that zircons of this age were sourced ment sourced from the Uralian Orogen must have crossed the East from the northeast. Syenitic to granitic magmatism of this age has Barents Basin to reach the southwest Barents Shelf. This implies been reported in Taimyr within the western part of the Taimyr fold- that the East Barents Basin and any possible embayment areas to and-thrust belt and this magmatism was possibly associated with the east prior to the development of Novaya Zemlya were not acting the late stages of the Siberian Traps (Vernikovsky et al., 2003). In as effective sediment sinks. This suggests that sediment supply addition, intrusive rocks with ages between 411 and 470 Ma occur must have been greater than subsidence in the basin allowing the on Severnaya Zemlya (see Lorenz et al., 2008 and references Uralian Sand Type to fill and bypass these basins. therein) which could provide an explanation for the Ordovician and The provenance change which occurs across the Early Norian Silurian zircon populations. MFS is interpreted to mark a major change in basin organisation. The seismic evidence for progradation to the northwest towards The Caledonian Sand Type which was previously restricted to the Svalbard in the Carnian is well documented (Glørstad-Clark et al., southern margins of the Hammerfest Basin became extensive and 2010; Høy and Lundschien, 2011; Lundschien et al., 2014; Riis flowed northwards over the Finnmark Platform and Hammerfest et al., 2008) and is not in dispute. The provenance data from the Basin and beyond into more northerly basin areas. This boundary Snadd Formation presented here is supportive of this interpreta- also marks a change in sedimentary style from one dominated by tion. However, the zircon signature of samples from the De Geer- delta progradation to one of shallow shelf conditions. This marked a dalen Formation on Svalbard and Late Triassic sandstones on Franz new phase of basin organisation that continued into the Jurassic Josef Land are not cognate with the Snadd Formation which implies and facilitated the deposition of mature sandstones of such as those the two areas had different sources. As such, an additional system is of the Stø Formation (main reservoir of the Snøhvit gas field). These proposed which delivered sand to Svalbard from source areas to the changes coincide with major tectonic activity in areas surrounding Fig. 10. Reconstruction of the palaeogeography and sandstone dispersal patterns for the southwest Barents Shelf during (a) the Induan (Havert Formation), (b) Olenekian (Klappmyss Formation), (c) Ladinian (Kobbe Formation), (d) Carnian (Snadd Formation) and (e) Rhaetian (Fruholmen Formation). 532 E.J. Fleming et al. / Marine and Petroleum Geology 78 (2016) 516e535

Fig. 11. Summary of the wider implications of the provenance results for northwest Pangaea in the late Carnian at maximum regression. The tectonic plate configuration was constructed using GPlates for plate reconstruction at 220 Ma using data from Müller et al. (2016). The palaeogeography is adapted after Scott et al. (1996) and Smelror et al. (2009). Also shown are the locations of samples used in Fig. 9. the Barents Shelf, such as the uplift of Novaya Zemlya (Scott et al., tectonism on Novaya Zemlya progressed, the East Barents Basin 2010). In Late Triassic to Early Jurassic times, uplift is also docu- would have transitioned into a forebulge basin resulting in mented in Eastern Finnmark and the Kola Peninsula (Hendriks and increased subsidence and the deposition of thick Jurassic and Andriessen, 2002; Veselovskiy et al., 2015) and it is inferred to have Cretaceous successions in that region. The barrier created by uplift occurred in other areas on the central and northern Barents Shelf. of the Finnmark Platform combined with increased subsidence in Such tectonic activity would have had two significant conse- the East Barents Basin would have acted to divert sediment quences. Firstly, uplift of the Finnmark Platform and Kola Peninsula northward, away from the western Barents Shelf possibly into areas would have created a barrier and prevented sediment derived from adjacent to the developing Novaya Zemlya thrust belt. Uplift of the the Urals reaching the southwest Barents Shelf. Secondly, as Triassic Finnmark Platform would have also resulted in the rejuvenation of E.J. Fleming et al. / Marine and Petroleum Geology 78 (2016) 516e535 533 the hinterlands in the northern Scandinavian source area. The presence of less mature sandstones, deposited at a considerable sandstones contain few Archaean and Palaeoproterozoic zircons, distance to the Uralian source area. These are in contrast to the high suggesting that the crystalline basement of the Fennoscandian porosity, clean sandstones seen around the Goliat field area in the Shield contributed few zircons. Instead, the zircon signal may either Caledonian Sand Type. This shows that until the Early Norian MFS, have been controlled by grains recycled from Caledonian molasse the reservoir characteristics of the Goliat discoveries are an deposits, which are thought to have extended across the area exception to the dominant provenance pattern seen on the (Larson et al., 1999) or were derived directly from the extension southwest Barents Shelf. As such, the existence of Triassic reser- Kalak Nappe Complex on to the Finnmark Platform (Gernigon et al., voirs with similar characteristics in areas further north should not 2014). The hinterland rejuvenation would have allowed fluvial be expected. After the Early Norian MFS, the more extensive units to extend further north onto the southwest Barents Shelf than development of depositional systems supplied by the composi- they had done previously. At the same time, the actions of sedi- tionally mature Caledonian Sand Type means that the reservoir mentary recycling of the pre-existing Caledonian and Uralian sand potential of Norian, and where preserved Rhaetian, sediments types and the erosion of coarser grained older units would have should not be overlooked. increased compositional maturity and grain size. These tectonic changes may also provide an explanation for the 10. Conclusions apparent contradiction between the zircon spectra from the De Geerdalen Formation in Svalbard and the offshore seismic data. We In this study, Triassic sandstones on the southwest Barents Shelf suggest that, in addition to the well-documented northwest cli- have been investigated through petrographic and heavy mineral noform progradation that reached offshore Svalbard in the Carnian analysis, garnet and rutile geochemistry and U-Pb zircon geochro- (Glørstad-Clark et al., 2010; Høy and Lundschien, 2011; Lundschien nology. Using these provenance techniques, in combination with et al., 2014; Riis et al., 2008), a second delta complex was also published sedimentological, provenance and seismic data, sand- present that delivered a Northern Uraloid Sand Type, sourced from stone dispersal patterns on the Barents Shelf have been recon- Taimyr and routed via Severnaya Zemlya to the northern Barents structed. The main outcomes are as follows: Shelf (Fig. 11). Although this system may have initially been minor, by the late Carnian, sediment restriction in the southwest associ- Until the Early Norian MFS, two sand types are recognised on the ated with initial stress change during the development of Novaya southwest Barents Shelf. The Caledonian Sand Type is charac- Zemlya combined with the Late Triassic uplift of Taimyr in the terised by a high compositional maturity, a heavy mineral northeast Barents may have resulted in renewed progradation of assemblage dominated by garnet, a low CZi value, predomi- this system. This system dominated sedimentation on Svalbard in nantly metapelitic rutiles and mostly Proterozoic and Archaean the late Carnian and delivered the unusual Mid Triassic population detrital zircon ages. It is interpreted to be sourced from northern from sources in Taimyr and Silurian/Ordovician from sources in Scandinavia. The Uralian Sand Type is characterised by a low Severnaya Zemlya. compositional maturity, high CZi value, predominantly meta- The poor documentation of this system to date may be due to mafic rutiles and Carboniferous zircon ages which are consistent problems interpreting clinoform geometries in the latest Carnian, with an origin from the Uralian Orogen. due to the increasingly shallow water deposition, along with a lack During the Induan to Early Norian stages (Havert, Klappmyss, of publically available seismic coverage from the northeast Barents Kobbe and Snadd formations), most of the southwest Barents Shelf. If confirmed, this hypothesis may provide an explanation for Shelf was dominated by the Uralian Sand Type. These results the evidence of marine conditions in Hopen (Hopen Member; Lord correspond to the well documented northeasterly prograding et al., 2014a) at the same time as continental deposition on Spits- Triassic clinoforms seen in the seismic data. In contrast, the bergen (Vigran et al., 2014) despite the former being in a more Caledonian Sand Type is restricted to the southern Hammerfest proximal to the northwest prograding systems. In addition, the Basin. northern system may have continued past Svalbard to the north- A significant provenance change occurs across the Early Norian eastern Sverdrup Basin which provides an explanation for Triassic- MFS. In response to Late Triassic/Early Jurassic hinterland reju- aged zircons in the area (Anfinson et al. 2016; Omma et al., 2011). venation and an increase in accommodation space in the East Future field, provenance and geophysical data, especially from Barents Basin, the Caledonian Sand Type becomes dominant and Svalbard and the northern Barents Shelf offshore, are needed to test extends northwards out onto the southwest Barents Shelf. The these hypotheses. main Uralian supply from the southeast is impeded and diverted into the East Barents Basin by the uplift of Novaya Zemlya. 9. Implications for petroleum exploration Recycling of Triassic units occurs at the basin margins, leading to a mixed Uralian/Caledonian signature in some samples. As provenance has a fundamental control on the composition of Discrepancies exist between the provenance signature of the clastic reservoir units, the variation highlighted in this study has Uralian-sourced Snadd Formation and age-equivalent strata in implications for hydrocarbon exploration on the Barents Shelf. The Svalbard and Franz Josef Land, which contain abundant zircons Triassic sandstone reservoirs of the Goliat field display high with mid-Triassic and Silurian-Ordovician ages. Sources for porosity and good reservoir quality (Rodrigues Duran et al., 2013). these zircons within the Uralian Orogen or Novaya Zemlya are With the considerable thickness of Triassic sediments further elusive; the most likely sources are Taimyr and Severnaya north, in areas postulated to be favourable for play development Zemlya. This system became increasingly dominant in the late (NPD, 2014), underpinned by the proven Triassic petroleum system Carnian and early Norian because the developing orogeny on in the Goliat field, one would expect significant opportunity for Novaya Zemlya choked sediment supply from the southwest hydrocarbon exploration. Despite this exploration outcomes have and resulted in a renewed phase of uplift in Taimyr in the Late been mixed. Triassic/Early Jurassic. Whilst the cause of the poor reservoir quality is likely to be These results are important for reservoir quality prediction. The complex, it is not coincidental that these more northerly explora- provenance data reveal that the sandstone reservoirs of the tion wells sit within the area that is dominated by the Uralian Sand Goliat field are an exception to the provenance signature for Type. The poor reservoir quality is at least in part due to the Triassic sandstones seen further north on the Barents Shelf at 534 E.J. Fleming et al. / Marine and Petroleum Geology 78 (2016) 516e535

this time. Until the Early Norian MFS, the Caledonian Sand Type, Special Publ. 24, 7e13. with often good reservoir potential, is restricted to the southern Harishidayat, D., Omosanya, K.d.O., Johansen, S.E., 2015. 3D seismic interpretation of the depositional morphology of the middle to late Triassic fluvial system in Hammerfest Basin. The remaining areas are dominated by the eastern Hammerfest Basin, Barents sea. Mar. pet. Geol. 68, 470e479. Uralian Sand Type which displays more variable reservoir Hendriks, B.W.H., Andriessen, P.A.M., 2002. Pattern and timing of the post- quality. Caledonian denudation of northern Scandinavia constrained by apatite fission-track thermochronology. Geol. Soc. Lond. Spec. Publ. 196, 117e137. Henriksen, E., Ryseth, A.E., Larssen, G.B., Heide, T., Rønning, K., Sollid, K., Acknowledgments Stoupakova, A.V., 2011. Tectonostratigraphy of the greater Barents Sea: impli- cations for petroleum systems. In: Spencer, A.M., Embry, A.F., Gautier, D.L., Stoupakova, A., Sørensen, K. (Eds.), Arctic Petroleum Geology, vol. 1. Geological This work was undertaken as part of the CASP Barents Shelf Society, London, pp. 163e195. Memoirs. Provenance Project. The sponsoring companies are thanked for Hochuli, P.A., Vigran, J.O., 2010. Climate variations in the boreal Triassic d inferred their continued support of this work. In addition, the authors would from palynological records from the Barents sea. Palaeogeogr. Palaeoclimatol. Palaeoecol. 290, 20e42. like to thank Stephen Vincent, two anonymous reviewers and the Høy, T., Lundschien, B.A., 2011. Triassic deltaic sequences in the northern Barents editor, Sven Egenhoff, for their constructive comments. The Nord- Sea. In: Spencer, A.M., Embry, A.F., Gautier, A.V., Stoupakova, A., Sørensen, K. sim ion microprobe facility operates as a joint Nordic infrastructure. (Eds.), Arctic Petroleum Geology, vol. 35. Geological Society, London, pp. 249e260. 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