Annales Societatis Geologorum Poloniae (2015), vol. 85: 151–175.

DEPOSITIONAL HIS TORY OF THE YOUN GEST STRATA OF THE SASSENDALEN GROUP (BRAVAISBERGET FORMA TION, MID DLE TRI AS SIC–CARNIAN) IN SOUTH ERN SPITSBERGEN, SVALBARD

Krzysztof P. KRAJEWSKI1 & Wolfgang WEITSCHAT2

1 Insti tute of Geolog i cal Sciences, Polish Academy of Sciences, Research Centre in Warszawa, Twarda 51/55, 00-818 Warszawa, Poland; e-mail addresses: [email protected]; [email protected] 2 Geologisch-Paläontologisches Institut und Museum, Universität Hamburg, Bundesstrasse 55, 20146 Hamburg, Ger many; e-mail address: wolfgang.weitschat@uni-ham burg.de

Krajewski, K. P. & Weitschat, W., 2015. Depositional history of the youngest strata of the Sassendalen Group (Bravaisberget Forma tion, Mid dle Tri assic–Carnian) in southern Spitsbergen, Svalbard. Annales Societatis Geolo- gorum Poloniae, 85: 151–175.

Ab stract: The Bravaisberget For mation of south ern Spitsbergen (the youn gest for mation of the Sassendalen Group; Middle Tri as sic–Carnian) comprises a suc ces sion of organic-rich and sandy phosphogenic de posits that de vel oped in a mar ginal part of the Svalbard ba sin, in re sponse to a high bi o log i cal pro duc tiv ity event in the Barents Shelf. The ba sin margin was bounded on the south west by the el e vated struc ture of the SÝrkapp-Hornsund High. North of the high, the sub siding shelf bot tom stretched from south ern to west ern Spitsbergen. The or ganic-rich, fine-grained sed i menta tion that gave rise to the for mation of the Passhatten Member ex tended southward af ter the Anisian trans gres sion; it reached the top most part of the SÝrkapp-Hornsund High during the maxi mum flooding of the ba sin in the early Ladinian. The sud den ap pear ance of deltaic depos its of the Karen- toppen Mem ber di rectly af ter the max i mum flooding was a con se quence of short-lived tec tonic ac tiv ity of the SÝrkapp-Hornsund High and the ad ja cent land area. Re working and re distri bution of the deltaic sed i ments during the Ladinian brought about the for mation of shal low-marine clastic fa cies of the Somovbreen Mem ber. De cre- as ing depositional rates close to the Mid dle-Late Tri as sic bound ary led to a re gional hi a tus and the for mation of a con densed phosphorite ho ri zon at the top of the Somovbreen Mem ber. The sed i menta tion of the Bravaisberget Forma tion ended in the early Carnian. The youngest siliciclastic and spiculitic sedi ments of the Van Keulen- fjorden Mem ber were de posited in south ern and west ern Spitsbergen in shal low- to mar ginal-ma rine en vi ron - ments.

Key words: Svalbard, Spitsbergen, Tri as sic, Sassendalen Group, Bravaisberget Forma tion, lithostratigraphy, fa cies, ammonoids.

Manu script re ceived 9 July 2014, ac cepted 2 De cem ber 2014

IN TRO DUC TION The Trias sic succes sion of Svalbard (Fig. 1; Harland, 1984; BjorÝy et al., 2006, 2010; Karcz, 2010, 2014; Kra- 1997; MÝrk et al., 1999) com prises marine facies in its jewski, 2013). They contain sandstone bod ies in south ern lower part (Sassendalen Group) and paralic facies in its up- and western Spitsbergen (Worsley and MÝrk, 1978; Kra- per part (Kapp Toscana Group). It records the geolog i cal jewski, 2000c; Krajewski et al., 2007; Haugan, 2012), and evolu tion of the NW Barents Shelf that was constrained by are overlain by thick sandstone units of the Kapp Toscana eustatic sea-level fluc tu a tions and oce anic in flu ences, re - Group throughout Svalbard (B³lum et al., 2012; MÝrk, gional tecton ics, and progradation of deltaic systems from 2013), which have the poten tial to be res ervoir rocks for hy- lo cal and dis tant source ar eas (Riis et al., 2008; Worsley, drocar bons in the Barents Sea. The assess ment of this north- 2008; Basov et al., 2009; GlÝstard-Clark et al., 2010). The ern source-res er voir sys tem for pe tro leum ex plo ra tion (Gro- youngest strata of the Sassendalen Group (Botneheia and gan et al., 1999) depends on an under stand ing of the depo- Bravaisberget for ma tions) are en riched to a ma jor ex tent in sitional, strati graphic, and struc tural con trols of the dis tri bu - marine organic carbon and are consid ered to be im portant tion of the organic-rich and sandy facies (HÝy and Lund- petro leum source rocks in the region (MÝrk and BjorÝy, schien, 2011; Anell et al., 2013, 2014a, b). 152 K. P. KRAJEWSKI & W. WEITSCHAT

Fig. 1. The Bravaisberget For mation (Mid dle Triasic–Carnian) in Spitsbergen, Svalbard. A. Map of Svalbard show ing out crops of the Trias sic succes sion in the West Spitsbergen Fold-and-Thrust Belt (WSFTB), includ ing the Lidfjellet-yrlandsodden Fold Zone (LFZ), and in the East ern Svalbard Platform (ESP), includ ing cen tral Spitsbergen. These two devel opments are sep a rated by the Palaeogene Cen - tral Spitsbergen (fore land) Ba sin (CSB). The sug gested bound ary be tween the ar eas of oc cur rence of the Botneheia and Bravaisberget for - mations (the youngest for mations in the Sassendalen Group) is marked by a dashed line. The Trias sic out crop belt after Dallmann et al. (2002), mod i fied. B. Geo log i cal map of SÝrkapp Land. The area en larged in Fig. 8 is marked by a rect an gle. Ge ol ogy af ter Winsnes et al. (1993), Dallmann et al. (1993b, 2002), Krajewski and Stempieñ-Sa³ek (2003), and un pub lished ma te ri als of the pres ent au thors, simpli - fied. 1 – ice and snow cover; 2 – Qua ter nary sed i ments; 3 – Van Mijenfjorden Group (Palaeogene); 4 – Helvetiafjellet and Carolinefjellet for ma tions (Early Cre ta ceous); 5 – Janusfjellet Subgroup (Late Ju ras sic–Early Cre taceous); 6 – Kapp Toscana Group (Late Tri as sic–Mid - dle Ju ras sic); 7 – Sassendalen Group (Early Tri assic–Carnian); 8 – Billefjorden, Gipsdalen and Tempelfjorden groups (Car bonif er ous– Perm ian); 9 – Adriabukta For mation (De vo nian); 10 – Cal edo nian base ment. C. Cen tral part of the SÝrkapp-Hornsund High shows the Tri as sic suc ces sion of the Sassendalen and Kapp Toscana groups rest ing di rectly on the Cal edo nian sub stra tum; here at Karentoppen be - tween Vitkovskibreen and Olsokbreen. The Bravaisberget Forma tion shows the pres ence of deltaic depos its (Karentoppen Mem ber) in the shallow-ma rine suc cession, which reflect event of sup ply of clastic ma terial from a land area lo cated southwest of the pres ent coast of southern Spitsbergen. This is the stratotype for the Karentoppen Mem ber (MÝrk et al., 1999). Pho to graph taken from Fisneset. BRAVAISBERGET FOR MATION IN SOUTH ERN SPITSBERGEN 153

This pa per pres ents the fa cies dis tri bu tion, lithostrati- graphy, and biostratigraphic data of the Bravaisberget For- mation of southern Spitsbergen (Middle Trias sic–Car- nian), with partic u lar ref er ence to the spatial and tempo ral re la tion ships be tween the or ganic-rich and sandy de pos its. It dem on strates that the sandy facies of the Somovbreen Member devel oped over the organic-rich facies of the Pass- hatten Mem ber as a result of shal low-marine rework ing and re dis tri bu tion of deltaic sed i ments (Karentoppen Mem ber), de liv ered to the ba sin margin from a local source area. The deltaic in put was a re sult of an event of tec tonic ac tiv ity that occurred di rectly after maxi mum flooding of the basin in the early Ladinian. The sandy succes sion of the Somovbreen and Van Keulenfjorden members straddles the Middle-Late Trias sic boundary and extends into the Carnian, record ing com plex his tory of ter mi na tion of fully ma rine en vi ron - ments in Svalbard. On the basis of these obser va tions and the revi sion of published data, the authors discuss the local and regional controls of depo si tion of the Bravaisberget Formation. A new corre la tion is proposed be tween the Bra- vaisberget Forma tion of southern and western Spitsbergen and the Botneheia Forma tion of central and eastern Spits- bergen and eastern Svalbard.

GEO LOG I CAL SET TING

The Trias sic Sassendalen Group in Svalbard (Harland, 1997; Vigran et al., 2014) shows pronounced differ ences in lithological devel op ment be tween the West Spitsbergen Fold-and-Thrust Belt (includ ing the Lidfjellet-yrlandsod- den Fold Zone) and the Eastern Svalbard Platform (includ - ing cen tral Spitsbergen). These two tectonic settings are sepa rated by the Central Spitsbergen (foreland) Basin, filled by Palaeogene depos its that accu mu lated during the time of the West Spitsbergen orogeny (Fig. 1). They repre sent dif- ferent depositional areas of the Trias sic basin in the NW Barents Shelf, with shallow-ma rine sandy fa cies con cen - trated in the fold belt and open-marine shaly facies domi nat - ing the platform (MÝrk et al., 1982; Steel and Worsley, 1984; Pèelina, 1998). The lithological contrast be tween these depositional sys tems was enhanced by differ en tial burial and tec tonic de for ma tion of the Tri as sic suc ces sion that led to ex ten sive ce men ta tion and the me chan i cal and chemical compac tion of the fold-belt strata (Krajewski, 2000b; Krajewski and WoŸny, 2009; MÝrk, 2013). Even though there are no exposed transi tions between Fig. 2. The Triassic lithostratigraphic scheme of Svalbard after the two devel op ments of the Trias sic succes sion and the rel- Nakrem and MÝrk (1991), MÝrk et al. (1999), Hounslow et al. atively fos sil-rich platform strata are far better rec og nized (2007, 2008), and Hounslow and Nawrocki (2008), simpli fied. WSFTB – West Spitsbergen Fold-and-Thrust Belt (in clud ing the than the fossil-poor strata in the fold belt, a consen sus has Lidfjellet-yrlandsodden Fold Zone); ESP – Eastern Svalbard been reached to pres ent a common stratigraphic scheme for Plat form (in clud ing cen tral Spitsbergen). For fur ther ex pla na tion, the Sassendalen Group (MÝrk et al., 1999). It distin guishes see text. (in ascend ing order) the VikinghÝgda and Botneheia forma - tions on the platform, and the Vardebukta, Tvillingodden, and Bravaisberget forma tions in the fold belt (Fig. 2). The The Botneheia Forma tion has been the subject of sev- VikinghÝgda Forma tion is con sidered to be an age equiv a- eral studies; and its stra tig raphy is best known in central lent of both the Vardebukta and Tvillingodden forma tions Spitsbergen (Korchinskaya, 1972a; Korèinskaja, 1972b, (roughly Early Trias sic), and the Botneheia Forma tion is fa- 1982, 2000; Weitschat and Lehman, 1983; Weitschat and cies equiv alent of the Bravaisberget Forma tion (roughly Dagys, 1989; Dagys and Weitschat, 1993; Pèelina, 1996; Mid dle Tri as sic). Hounslow et al., 2006b, 2007, 2008; Xu et al., 2009). The 154 K. P. KRAJEWSKI & W. WEITSCHAT

forma tion spans a period from early Anisian to late Ladi- ships in southern and western Spitsbergen indi cate diachro- nian, though the dat ing of its basal and top parts is am bigu - nous boundaries be tween the mem bers of the Bravaisberget ous. The lower part of the forma tion (recog nized as the Forma tion (Krajewski, 2000a, c, Krajewski et al., 2007; Muen Mem ber in eastern Svalbard; Krajewski, 2008) is of Haugan, 2012). early to middle Anisian age in central Spitsbergen (Houn- The transi tion between the Sassendalen and Kapp Tos- slow et al., 2008). It comprises a black shale fa cies rep re - cana groups in the main outcrop belt in Svalbard (Spitsber- sent ing a dis tal prodelta en vi ron ment. The over ly ing Blank- gen, BarentsÝya and EdgeÝya) has been in ter preted as re fer - nuten Mem ber is of late Anisian through Ladinian age able to the Ladinian-Carnian boundary (Dagys and Weit- (Hounslow et al., 2008; Xu et al., 2009). It is rep resented by schat, 1993; Pèelina, 1998; Korèinskaja, 2000; Konstanti- a phosphatic black shale and mudstone succes sion depos - nov, 2008). However, recent magneto-biostratigraphic in- ited in an open shelf envi ron ment (Krajewski, 2013). ves ti ga tions in cen tral Spitsbergen sug gest an im por tant hi a- The Bravaisberget Forma tion has been subdi vided into tus between the groups (Hounslow et al., 2006a, b, 2007, four members (the Passhatten, Somovbreen, Karentoppen, 2008; Hounslow and Nawrocki, 2008). Accord ing to these and Van Keulenfjorden members) that show facies com- authors, the hia tus is likely to occur over the whole of Sval- plexity and differ ences in distri bu tion in southern and west- bard, broaden ing south-westward in Spitsbergen (Fig. 2). ern Spitsbergen (Pèelina, 1967, 1985; MÝrk et al., 1982; This in di cates that the ter mi na tion of ma rine en vi ron ments of Krajewski, 2000c; Krajewski et al., 2007). The shale-dom i- the Sassendalen Group was not sim ply related to prograda- nated Passhatten Member makes up the lower and middle tion of the prodelta/delta facies of the Kapp Toscana Group, parts of the forma tion in western Spitsbergen (Bellsund, but included a period of erosion and/or non-depo si tion. Isfjorden). It is thought to repre sent organic-rich depo si tion The Trias sic part of the Kapp Toscana Group in the in a mostly shallow-shelf envi ron ment (Karcz, 2010). It platform devel op ment con sists of the lower Tschermak- thins southward and becomes a subor di nate unit of the for- fjellet Forma tion (early Carnian prodelta shale) and the up- mation on the SÝrkapp-Hornsund High, a Palaeozoic uplif- per De Geerdalen Forma tion (Carnian deltaic sand stone) ted structure, exposed along western SÝrkapp Land (Har- that are overlain by the shallow-ma rine shale/sandstone suc- land, 1997). The overly ing Somovbreen Mem ber com prises ces sion of the Wil helmÝya Sub group (Steel and Wors ley, a sandy to silty, marine succes sion encom pass ing and cov - 1984; MÝrk et al., 1999; Hounslow et al., 2007). The Wil- ering wedges of deltaic depos its. This member is best deve- helmÝya Sub group in central and east ern Spitsbergen, on loped in southern Spitsbergen, thinning north of Bellsund Wil helmÝya, and in some loca tions in eastern Svalbard and replaced by a succes sion of phosphatic (“oolitic”) grain- (Knorringfjellet, Flatsalen, SvenskÝya, and KongskÝya for- stones in the Isfjorden area (Festningen). The deltaic depos its ma tions) strad dles the Tri as sic-Ju ras sic bound ary and ex- are distin guished as the Karentoppen Mem ber (MÝrk et al., tends into the Mid dle Ju ras sic (Bäckström and Nagy, 1985; 1999; Haugan, 2012). They are confined to the southern and Nagy et al., 2011). This divi sion be comes less distinct in the western parts of SÝrkapp Land (Fig. 1C). Both the Passhatten fold belt, where in many places only an undif fer en ti ated and Somovbreen members are phosphatic as a rule, contain - succes sion of the lower part of the Kapp Toscana Group ing mostly nod u lar phos phate ac cu mu la tions (Krajewski, (shale with sandstone) has been rec og nized (Harland, 2000a). The topmost Van Keulenfjorden Member comprises 1997). However, in sev eral places, the basal part of the suc- sili ceous and dolomitic sandstones and shales as well as spi- ces sion is shale-domi nated, and there fore classi fied as the culitic depos its that are rec og nized throughout south ern and Tschermakfjellet For ma tion (Birkenmajer, 1977; Steel and west ern Spitsbergen (Pèelina, 1983; MÝrk et al., 1999; Kra- Wors ley, 1984; Vigran et al., 2014). The overly ing sand - jewski et al., 2007; Krajewski and WoŸny, 2009). stone-domi nated unit, which in some sections is classi fied Rare discov er ies of ammonoids, bivalves, and cono- as the De Geerdalen For mation (Dallmann et al., 1993b; donts in the Passhatten and Somovbreen mem bers ap pear to Vigran et al., 2014), tends to replace the shaly succes sion in in di cate a Middle Tri as sic age for the Bravaisberget For ma - the fold belt between Bellsund and Isfjorden (MÝrk and tion (Buchan et al., 1965; Pèelina, 1967, 1983, 1985, 1996; Wors ley, 2006). The Wilhelm Ýya Subgroup is repre sented Korchinskaya, 1972a; Korèinskaja, 1972b; Birkenmajer, by a condensed Smalegga Forma tion (MÝrk et al., 1999). It 1977; Trammer, 1978; Clark and Hatleberg, 1983; Nakrem can be identi fied in most sections in southern and western et al., 2008). Parts of the forma tion were assigned either an Spitsbergen, form ing a thin quartzitic sand stone unit at the Anisian or Ladinian age, though the geolog i cal loca tion of top of the Kapp Toscana Group (Krajewski, 1992a, b). the fossils col lected is com monly un certain, and the valid ity of the palaeontological deter mina tions is dif fi cult to as sess. In the stratigraphic scheme of MÝrk et al. (1999) and in the MA TE RI ALS AND METH ODS sub se quent pa pers by Hounslow et al. (2007, 2008) and Hounslow and Nawrocki (2008), the Passhatten Mem ber is This paper reports the results of geolog i cal and palaeo- cor re lated with the lower part of the Botneheia For mation ntological in ves ti ga tions of the Bravaisberget For ma tion in and the succes sion of the Somovbreen and Van Keulenfjor- SÝrkapp Land, supported by com para tive stud ies in the den mem bers are proposed as being roughly coeval with the Hornsund and Bellsund areas (Fig. 1A). The field work con- Blanknuten Mem ber (Fig. 2). The discon tin u ous Karen- centrated on the Trias sic outcrop belt, exposed along the toppen Member is placed between the Passhatten and So- western and southern coasts of SÝrkapp Land and on the movbreen mem bers. How ever, biostratigraphic doc u men ta - neighbour ing islands (Fig. 1B). The succes sion in the south- tion of this cor re la tion is lacking; and the fa cies re la tion - ern most SÝrkapp Land, which gave stratigraphically impor - BRAVAISBERGET FOR MATION IN SOUTH ERN SPITSBERGEN 155

tant ammonoid findings, is reported here in detail. This in - 1C) wedges out southward (north of St. Nikolausfjellet) and cludes detailed logs of two sections, located at Bergnasen northward (south of Vitkovskibreen). The Karentoppen (KS section) and Keilhaufjellet (KL section) on both sides Member reap pears below the Somovbreen Mem ber on SÝr- of Mathiasbreen. The petrog ra phy of the sed iment types kappÝya and StjernÝya. It should be noted, however, that discerned and the fossils was studied in thin sec tions, using the suc ces sion exposed there is nearly ver tical in the west - trans mit ted- and re flected-light mi cros copy. The mi cro - ern limb of a complex synclinal structure belong ing to the scopic sur vey was sup ported by min eral iden ti fi ca tion, us- Lidfjellet-yrlandsodden Fold Zone. This structure has a ing x-ray dif frac tion anal y sis of dis or dered pow der sam ples. continuation toward TokrossÝya and yrlandsodden (Per- Se lected thin sec tions were ana lysed us ing scan ning elec - mian TokrossÝya Forma tion), but it is sepa rated from the St. tron micros copy (back-scat tered elec tron images and micro- Nikolausfjellet-Kistefjellet area by down-faulted Palaeo- probe analy sis) in order to reveal the compo si tion and distri - gene strata at yrlandet. The deltaic wedges of the Ka ren- bution of heavy miner als in the clastic sed iments. De tails of toppen Mem ber, observed along the western coast of SÝr- the an a lyt i cal pro ce dure and the in stru ments used can be kapp Land, have a complex pattern, although they disap pear found in Krajewski and WoŸny (2009) and Krajewski north-east ward over a distance of a few kilo metres (Fig. 3). (2013). Palaeontological inves ti gation of the fossils was This can be best demon strated in the Lidfjellet tectonic done us ing a bin oc u lar mi cro scope un der ×5–50 mag ni fi ca - structure (Krajewski and Stempieñ-Sa³ek, 2003), where the tions. The fos sil col lec tion of Stolleyites planus from the KS Karentoppen Mem ber thins from about 30 m in the autoch- and KL sections (samples KL-1C.1, KL-1C.2, KL-1E, thonous cover (Liddalen) to less than 5 m in the overthrust KS-17, and KS-20) is housed at the Insti tute of Geolog i cal unit (Lidfjellet) over a displace ment distance of about 2 km, Sci ences, Polish Academy of Sci ences in Warszawa. and becomes ab sent at Kovalevskifjellet over the next 2 km to the northeast. The Van Keulenfjorden Mem ber shows contin u ous de- RE SULTS velop ment in southern and western Spitsbergen. It is thick- est on SÝrkappÝya and at Kistefjellet-Bergnasen in south - Lithostratigraphy of the Bravaisberget Forma tion ern most SÝrkapp Land, thinning slightly in the remain der of in southern Spitsbergen southern and western Spitsbergen. In the Bellsund and The lithostratigraphy and facies devel op ment of the Sa- Hornsund areas, the mem ber is repre sented by two suc ces - ssendalen Group in south ern Spitsbergen is given in Figure sive coarsen ing-up ward units (Krajewski, 2000c, Krajewski 3A–D. The Early Trias sic Vardebukta and Tvillingodden et al., 2007). This subdi vi sion becomes less distinct south- forma tions are well devel oped north of SÝrkapp Land, but west ward, where a more com plex suc ces sion of al ter nat ing thin toward the SÝrkapp-Hornsund High, where the trans- silty and sandy lithologies appears along the western and gressive con glomer atic suc ces sion of the Kistefjellet Mem- southern coasts of SÝrkapp Land. ber repre sents the Vardebukta Forma tion. On the southern margin of the high (SÝrkappÝya), only an un dif fer en ti ated Fa cies of the Bravaisberget Forma tion in south ern succes sion of shales and lam inated siltstones/sandstones Spitsbergen can be assigned to these forma tions. Sim ilar thickness reduc tion can be ob served in the Bra- The Passhatten Mem ber (Fig. 4) comprises a suc ces sion vaisberget Forma tion, which thins from more than 200 m in of dark grey to black mud- to silt-shales with siltstone/sand- the Bellsund area (Bravaisberget) to about 100 m in the stone in ter ca la tions; the latter are bioturbated as a rule, with Hornsund area (Treskelen), and to less than 70 m in the cen - Taenidium and Rhizocorallium the domi nant trace fossils. tral part of the SÝrkapp-Hornsund High (Fisneset). This is Thalassinoides is observed in the shale, form ing flattened as so ci ated with a sig nif i cant re duc tion in the thick ness of burrow systems filled with phosphatic sedi ment (see also the shale-domi nated Passhatten Member, which is progres - MÝrk and Bromley, 2008). The shale contains com mon sively replaced south ward by the thicken ing sand stone-/ quartz grains in the fine- to coarse-silt fractions, and flakes siltstone-dom i nated Somovbreen Mem ber. of de tri tal mica. Other de tri tal com po nents, in clud ing feld - SÝrkapp Land is the only area where all four members spar and heavy min eral grains, are ac ces sory. Clay miner als of the Bravaisberget Forma tion can be discerned. The ma- are dom inated by illite. The succes sion is organic-rich, rine Passhatten and Somovbreen mem bers and the marginal though usually it shows advanced levels of thermal alter - marine Van Keulenfjorden Member occur in stratigraphic ation (Krajewski, 2000c). Both amorphous and structured order. They are recog nized throughout the outcrop belt in or ganic matter oc cur in the shale. The or ganic matter is as - SÝrkapp Land, except for the Passhatten Mem ber that is soci ated with authigenic, framboidal and microgranular py- missing in the cen tral part of the SÝrkapp-Hornsund High rite. Microfossils ob served in thin sec tions in clude si li ceous (RÝysneset–Fisneset), and on SÝrkappÝya and StjernÝya. sponge spicules, rare arenaceous foraminifera and radiolaria The Karentoppen Member, which comprises medium- to moulds, and the debris of uniden ti fied bivalve and brachio - coarse-grained deltaic fa cies in the lower part of (or be low) pod shells. Their content irreg u larly decreases toward the the Somovbreen Member, makes up a stratiform hori zon on SÝrkapp-Hornsund High, along with a general increase of SÝrkappÝya and StjernÝya, and lensoidal bodies at Lidfje- the amount of clastic grains. llet–Liddalen, RÝysneset, and Karentoppen. It is absent in The silty and sandy sedi ments of the Somovbreen Mem - south ern most SÝrkapp Land. The main deltaic fa cies com- ber (Fig. 5) are com posed of quartz grains ce mented by cal- plex recog nized at Karentoppen and Lébedevfjellet (Fig. citic sparite. The sandy sed iments are very fine- to fine-grai- 156 K. P. KRAJEWSKI & W. WEITSCHAT BRAVAISBERGET FOR MATION IN SOUTH ERN SPITSBERGEN 157

Fig. 3. Lithostratigraphy and fa cies of the Sassendalen Group in south ern Spitsbergen. A. Van Keulenfjorden (Bravaisberget). B. In ner Hornsund and NE SÝrkapp Land. C. Western coast of SÝrkapp Land. D. SÝrkappÝya and StjernÝya. For fur ther ex pla na tion, see text. 158 K. P. KRAJEWSKI & W. WEITSCHAT

Fig. 4. Facies de vel opment of the Passhatten Mem ber in south ern Spitsbergen. A. Succes sion of the Sassendalen Group in Liddalen, NW SÝrkapp Land. The suc ces sion be longs to the autochthonous part of the Lidfjellet tec tonic struc ture (Lidfjellet-yrlandsodden Fold Zone), and re cords Tri assic depositional his tory at north ern mar gin of the SÝrkapp-Hornsund High. The transgressive con glomer ates and sand stones of the Kistefjellet Mem ber (Vardebukta Forma tion) rest dis cor dantly on quartzitic sand stones of the Car bon if er ous Horn- sundneset For mation. They are over lain by lam i nated siltstones and shales of the Tvillingodden For mation. The Bravaisberget Forma tion is rep re sented by the Passhatten, Karentoppen, Somovbreen, and Van Keulenfjorden members. The Passhatten Member com prises a cliff-form ing black shale suc ces sion, re flect ing or ganic-rich de posi tion at mar gin of the high before the in put of coarse deltaic clastics of the Karentoppen Member. B. Non-lami nated, fissile black shale of the Passhatten Member. Sec tion per pen dic u lar to bed ding. Lidfjellet, NW slope. C. Flat tened, phos phate-filled bur row sys tem Thalassinoides in black shale of the Passhatten Member. Plane paral lel to bed- ding. Lidfjellet, NW slope. D. Photo micro graph of black shale shown in (B). The shale con tains quartz grains of the fine- to coarse-silt fractions (q) and detri tal mica flakes (m) in a clay-rich ma trix. E. Organic mat ter in the black shale is rep re sented by seams of amorphous fraction (am) and vitrinite parti cles (v), preserved at an advanced stage of thermal alter ation. Quartz grains (q) oc cur in the ma trix. Lidfjellet, NW slope. (D, E) – trans mit ted-light mi cros copy, crossed nicols. BRAVAISBERGET FOR MATION IN SOUTH ERN SPITSBERGEN 159

Fig. 5. Fa cies de vel op ment of the Somovbreen Member in south ern Spitsbergen. A. Suc ces sion of marine sand stones with siltstone/ shale in ter ca la tions of the Somovbreen Mem ber at Fisneset was de posited in front of deltaic sed i ments of the Karentoppen Member. The sand stone pack ages con tain vary ing amounts of pris tine and allochthonous phos phate nod ules. B. Re worked ho ri zons of allochthonous phosphate nod ules and clasts in highly bioturbated sand stone of the Somovbreen Mem ber at RÝysneset. The sandstone con tains com mon trace fossil Skolithos. C. Taenidium on a sur face paral lel to bedding in fine-grained sand stone of the Somovbreen Mem ber at Keil- haufjellet. D. Rep til ian bone in phos phatic sand stone of the Somovbreen Mem ber at RÝysneset. E. Finely bioturbated na ture of sand stone of the Somovbreen Mem ber at Kistefjellet. Thin sec tion pho to graph. Sec tion per pen dic u lar to bed ding. F. Pho to mi cro graph of very fine-grained sand stone of the Somovbreen Mem ber at Wintherpynten. The sed i ment con sists of quartz (q) and glauconite (g) grains ce - mented by calcitic sparite (c). Diagenetic do lo mite rhombs (d) oc cur as sub or di nate ce ment. Trans mit ted-light mi cros copy, crossed nicols. 160 K. P. KRAJEWSKI & W. WEITSCHAT

Fig. 6. Fa cies de vel op ment of the Karentoppen Member in south ern Spitsbergen. A. Me dium- to coarse-grained sand stones fill ing delta distributary chan nel (Karentoppen Member) in the lower part of shal low marine sand stone suc ces sion of the Somovbreen Member at RÝysneset. The Somovbreen Member con tains in places lenses of beach gravelstone, composed of peb bles of dif fer ent rocks of the Cal - edo nian base ment in ter mixed with allochthonous phosphate nod ules and clasts. Note that the suc ces sion seen on the photo can be as sessed dur ing low tide of the sea. B. Part of a 30 m high cliff of the Karentoppen Member at Karentoppen show ing me dium- to coarse-grained sand stone lenses with tab u lar cross-bed ding. Lo ca tion of this cliff is shown in Fig. 1C. C. Medium- to coarse-grained sand stone lenses of the Karentoppen Member at RÝysneset. The lenses show erosional bound aries, tab u lar cross-bed ding with tan gen tial foresets, and scat - tered land-plant de tri tus. Sec tion per pen dic u lar to bed ding. D. Large Diplocraterion-like bur row that cuts lamina set of coarse-grained sand stone fill ing distributary chan nel at SÝrkapplaguna on SÝrkappÝya. Sec tion per pen dic u lar to bed ding. E. Land-plant de tri tus (black) in coarse-grained sand stone of the Karentoppen Member at SÝrkapplaguna on SÝrkappÝya. Bed ding plane. F. Pho to mi cro graph of me- dium- to coarse-grained sand stone of the Karentoppen Member at RÝysneset. The sandstone con tains quartz (q) and quartz ite (qz) grains, with subor di nate ad mixture of other lithic grains. Trans mitted-light mi cros copy, crossed nicols. BRAVAISBERGET FOR MATION IN SOUTH ERN SPITSBERGEN 161

ned. They contain glauconite grains and subor di nate feld spar though most of the phosphate fraction is repre sented by grains and also show an ele vated content of detri tal zircon phosphatic ammonoids and products of their mechan i cal and rutile at recur rent lev els in the suc ces sion. Coarser-grai- dis in te gra tion. In south-west ern SÝrkapp Land, they are ned sed iments contain ing lithic grains appear in close prox- concen trated in recur rent hori zons up to 0.5 m thick, which imity to the deltaic depos its of the Karentoppen Member. The are sepa rated by thicker sandstone packages with out phos- sandstones and siltstones are finely bioturbated. Taenidium is phate. In north-east ern SÝrkapp Land and in in ner Horn- the domi nant trace fossil. However, the contri bu tion of verti - sund, the top of the Somovbreen Mem ber is ac centu ated by cal burrows (Polykladichnus and Skolithos) ir reg u larly in- a thin (up to 0.4 m thick), con densed phosphorite-bearing creases up ward within the suc ces sion. The clastic sed iments ho rizon or a remanié de posit, con tain ing re worked and show com mon ev i dence of me chan i cal re work ing and win- rounded phosphate nodules and phosphatic ammonoids. now ing. Biogenic com po nents in clude phos phatic ammono- The Van Keulenfjorden Mem ber (Fig. 7) com prises a ids, sili ceous sponge spicules, debris of bivalve and brachio - clastic succes sion of quartz sandstones, siltstones, and silty pod shells, and reptil ian bones and copro lites. Rare fragments shales that usually are silica-ce mented and show a sub or di - of petri fied tree trunks have been observed north of the SÝr- nate admix ture of dolo mite cement. This contrasts with cal - kapp–Hornsund High. cite-ce mented sandstones and siltstones of the under ly ing The sandstones of the Karentoppen Member (Fig. 6) are Somovbreen Member. In south-western SÝrkapp Land, these composed of well-rounded quartz and quartzite grains of the sed i ments con tain an im por tant ad mix ture of de tri tal mica medium- to coarse-sand fraction (in places, also the fine- and feld spar. The suc ces sion shows sed i men tary fea tures in- gravel fraction), with a subor di nate admix ture of other lithic dic a tive of mar ginal- to shal low-ma rine en vi ron ment, in clud - grains. In the distributary chan nel fills, they are arranged in ing structures and lamina tions typi cal of fine-grained beach pack ages up to a few meters thick that show large-scale tab - de pos its. Polykladichnus is the domi nant trace fos sil. Within u lar cross-bed ding and ero sional bound aries ac cen tu ated by the clastic suc ces sion, there are interbeds and lenses of oc cur rences of gravel. These pack ages show the pres ence of spiculitic depos its. They are com posed of sili ceous sponge U-shaped bur rows re sem bling Diplocraterion and scat tered spicules showing advanced stages of disso lu tion and replace - plant de tri tus. The plant de tri tus is con cen trated at some ment by diagenetic sil ica. Ma trix sili ci fi ca tion was a common bedding planes to form carbo na ceous layers and seams. process in these lithologies. It led to the forma tion of nodu lar These seams be come common in the SÝrkappÝya outcrop and/or banded chert hori zons with microlaminated quartz ce- belt, where indi vid ual wood fragments may attain 10 cm in ment. The cherts are also ob served in the siliciclastic sedi - length. It should be noted, however, that the woody de bris ments. The con tent of spiculites in the Van Keulenfjorden repre sents the washed and transported fraction, and that no Mem ber in creases north-east ward in SÝrkapp Land. palaeosol ho rizons have been noted in the deltaic succes - sion. In the delta-front facies, the sandstones form thick, Bergnasen (KS) and Keilhaufjellet (KL) sections massive beds, sepa rated by thin layers of muddy sedi ment of the Bravaisberget Forma tion or by erosional boundaries. The beds are mechan i cally and bioturbationally ho mog enized, though some exhibit wave- The Passhatten, Somovbreen, and Van Keulenfjorden and cur rent-in duced sed i men tary struc tures. Skolithos ap - members are recog nized on the mountain slopes between pears in this facies. In the Karentoppen-Lébedevfjellet sec - Kistefjellet and Keilhaufjellet, where they form a nearly tion, two events of delta advance ment can be discerned. flat-ly ing sed i men tary suc ces sion (Fig. 8). How ever, the They are sepa rated by a thin, marine sandstone unit with Passhatten Member is mostly cov ered by scree, and its con - phosphate nodules and Thalassinoides that re flects flood ing tact with the un der ly ing Tri as sic de pos its is ob scured. The event of the delta envi ron ment (Haugan, 2012). One thick same succes sion can be seen in a fallen tec tonic block in the succes sion of the deltaic depos its on SÝrkappÝya suggests coastal area be tween Skjemmeneset and Moloen, though it that the flooding was a local phenom e non, most proba bly is poorly exposed and sepa rated from the Kistefjellet block related to changes in delta config u ra tion in SW SÝrkapp by a sys tem of eche lon faults. Land. Close to the margins of the Karentoppen Mem ber at The sections of the Bravaisberget Forma tion measured RÝysneset, there occur beach gravelstones com posed of on the eastern slope of Bergnasen (KS section) and at the pebbles of differ ent rock types of the Caledo nian substra - foot of western slope of Keilhaufjellet (KL section) are pre- tum (the SÝrkapp-Hornsund High suc ces sion), in ter mixed sented in Figures 9 and 10, respec tively. with allochthonous phosphate nodules and clasts. The KS section displays about 5 m of the upper most The Passhatten and Somovbreen members contain phosphatic shale succes sion of the Passhatten Mem ber, com mon phos phate de pos its, in clud ing nod u lar, con glom er- which is over lain by a suc ces sion of cal cite-cemented, fine- atic, peloidal and crust-type ac cu mu lations as well as phos - grained sand stones and siltstones of the Somovbreen Mem- phatic fossils, burrows and phosphatized bones (Figs 4, 5). ber, 60 m thick (Fig. 11A). Phosphate depos its are common On the SÝrkapp-Hornsund High, the content of phosphate over the lower 12 m of the succes sion, making recur rent ho - in the Passhatten Member exhib its a rather ir reg u lar pat tern, rizons of pristine and allochthonous nodules sepa rated by reflect ing phosphogenesis in shallow-ma rine shaly facies. It winnowed surfaces (Fig. 11B, C). In the upper part of the attains a maxi mum in the lower part of the Somovbreen suc ces sion, there are re cur rent ho ri zons en riched in phos- Member in loca tions where the deltaic Karentoppen Mem- phatic ammonoids. The Somovbreen Member is overlain ber is miss ing. The upper part of the Somovbreen Mem ber with a sharp boundary by a 30-m-thick succes sion of sil - shows a notice able decrease in the content of phosphate, ica-cemented sandstones, sandy siltstones, and shales of the 162 K. P. KRAJEWSKI & W. WEITSCHAT

Van Keulenfjorden Member. This succes sion is in turn levels, and between the 22-m and 25-m levels (Fig. 11D). overlain by shales with flora detri tus of the lower part of the These ho ri zons con tain al most ex clu sively phos phatic Kapp Toscana Group. ammonoids and products of their mechan i cal rework ing The KL section encom passes the upper part of the So- (Fig. 11E, F). The overly ing silica-ce mented sandstones and movbreen Mem ber (about 30 m thick), with phosphatic ho- shales of the Van Keulenfjorden Member are 20 m thick, rizons concen trated in inter vals between the 6-m and 12-m being sharply overlain by shales of the Kapp Toscana BRAVAISBERGET FOR MATION IN SOUTH ERN SPITSBERGEN 163

Fig. 7. Facies de vel opment of the Van Keulenfjorden Mem ber in south ern Spitsbergen. A. Succes sion of the up per part of the Bravaisberget Forma tion at Treskelodden (in ner Hornsund), showing po si tion of the Van Keulenfjorden Mem ber. This mem ber is sep a - rated from the un der ly ing Somovbreen Mem ber by a thin, dis con tin u ous ho ri zon of con densed phosphorite con glom er ate con tain ing phos- phatic ammonoids of the family Nathorstitidae (?Stolleyites sp.). The condensed ho ri zon marks the bound ary be tween the Somovbreen and Van Keulenfjorden members in the fold belt (from AustjÝkultinden on the south to Bravaisberget on the north; see Fig. 3). It is re - placed by re worked, fossiliferous phos phatic ho ri zons in the sandy suc ces sion of the up per most part of the Somovbreen Member in the south-west ern out crop belt in SÝrkapp Land (Fisneset–Keilhaufjellet). The Van Keulenfjorden Member is rep re sented by si li ceous sand - stones, siltstones and shales with spiculitic de posits. The Treskelodden out crop be longs to the east ern limb of the Hyrnefjellet Anticline (Birkenmajer, 1964) that rep re sents the Sassendalen Group de posited north of the SÝrkapp-Hornsund High. This suc ces sion rests upon the Hyrnefjellet and Treskelodden for mations (Gipsdalen Group) cov ered by a thin Kapp Starostin Forma tion (Tempelfjorden Group), and is over lain by the Kapp Toscana Group con tain ing in its lower part the shaly in ter val classi fied as the Tschermakfjellet Forma tion. B. Sand - stone bed in the silty/shaly pack age in the middle part of the Van Keulenfjorden Member at Bautaen, in ner Hornsund. The sand stone shows sedimentologic fea tures in di cat ing a beach en vi ronment. The com mon trace fos sil Polykladichnus cuts lensoidal and rip ple lami na - tions of the sand stone. Dark shaly siltstones be low and above the sand stone bed show the pres ence of banded and nod u lar chert, re spec - tively. The chert depos its reflect silici fica tion of the sedi ment as a re sult of diagenetic mobi li za tion of spiculitic silica. C. Nodu lar chert in silty sand stone in the up per part of the Van Keulenfjorden at Bautaen. D. Photo micro graph of very fine-grained sand stone of the Van Keulenfjorden Mem ber at Kistefjellet. The sand stone con sists of quartz grains (q) cemented by microcrystalline quartz cement (qc). E. Photo micro graph of spiculite in the lower part of the Van Keulenfjorden at Bautaen. The rock is com posed of si li ceous sponge spicules (s) replaced and cemented by microcrystalline quartz cement (qc). (D, E) – diagenetic do lo mite rhombs (d) oc cur as sub or di nate ce ment. Trans mit ted-light mi cros copy; (D) – crossed nicols; (E) – par al lel nicols. Scale in (D) for both pho tos.

Group. The top most part of the Tri assic succes sion at Keil- crofossils. The central parts and voids in the phragmocones haufjellet is af fected by a small-scale overthrust, which dou - are filled with cal cite ce ment, which usu ally is blocky bles the thickness of the upper part of the Kapp Toscana and/or gran u lar sparite. Cal cite ce ment also fills mouldic Group (includ ing the Smalegga Forma tion) higher up on the pores, devel oped after disso lu tion of the aragonitic skele - moun tain slope. tons. Paragenetic re la tion ships be tween ap a tite, py rite, and cal cite in di cate that the cal cite ce men ta tion oc curred af ter the forma tion and rework ing of the phosphatic moulds dur- Phos phatic ammonoids in the Somovbreen Member ing their final burial in the sedi ment column. All ammonoids found in the Bravaisberget Forma tion of south ern most SÝrkapp Land came from the upper part of Stolleyites planus the Somovbreen Member. They are preserved in the form of More than forty ammonoid spec imens were col lected phosphatic moulds of phragmocones, devel oped as a result along the outcrop belt of the Somovbreen Member between of phos phate ce men ta tion of the orig i nal an i mal skel e tons, Kistefjellet and Keilhaufjellet. How ever, most of them as well as their sedi ment in fill ings (Fig. 12). The ce menta - show poor pres erva tion. The gen eral features of the phrag- tion was a very early pro cess oc cur ring close to the wa ter/ mocone moulds allow classi fi ca tion of them into the family sed iment in ter face in loose, clastic sed iment. The major Nathorstitidae. Five well-pre served spec imens from sec- phosphate phase in the phosphatic ammonoids and else- tions KL and KS were deter mined to be Stolleyites planus where in the phosphate fraction has been x-ray identi fied as (Fig. 13). Details of the loca tion of these discov er ies are car bon ate fluorapatite. Mi cro scopic ob ser va tions sug gest shown in Figures 9 and 10. that the crys talli za tion of ap atite was pre ceded by the pre - Stolleyites planus (Frebold) is char acter ized by a very cip i ta tion of an amor phous cal cium phos phate pre cur sor. It distinct umbil i cal depres sion in the early and middle onto- led to the forma tion of fringe cement on the skele tal sur- genetic stages and by the presence of strongly pronounced faces, pre serv ing their fine an a tom i cal de tails (see also umbil ical bullae in the middle and late ontogenetic stages. It Weitschat, 1986; Weitschat and Bandel, 1991; Zakharov is sim i lar to its prob a ble an ces tor Nathorstites lindstroemi, and Shkolnik, 1994). The dynamic envi ron men tal agents from which it differs mainly in the presence of distinct bul- contrib uted to the winnow ing of the upper sed iment layer lae up to the lat est ontogenetic stages. and the exhu mation of the ammonoids at var ious stages of Samples of the fauna under consid er ation were first de - phosphatization. Conse quently, the state of preser va tion of scribed by Stolley (1911) as two new spe cies: Nathorstites the ammonoids varies widely, even within the same phos- tenuis and N. gibbosus. These two spe cies were later divi- phatic hori zon. The best preserved are those forming pris- ded into two differ ent genera. N. tenuis was assigned to the tine nodules, i.e. the ones that ex peri enced a sin gle ep isode ge nus Paraindigirites by Popov (1961). N. gibbosus was as - of phosphogenesis and remained at their origi nal posi tion in signed to the new ge nus Stolleyites by Arkhipov (1974). the sedi ment. The forma tion of fringe apa tite cement in- The ge nus Stolleyites differs from other genera of the fam ily cluded pulses of phos phate pre cip i ta tion sep a rated by pul- Nathorstitidae in its ontogenesis and the char ac ter is tic ses of precip i ta tion of pyrite micrograins and/or framboids. cross-section of volutions. Nathorstites gibbosus, var. In the clastic infill ings of the phragmocones, the apa tite ce- plana, ac cord ing to the rules of zoo log i cal no men cla ture, ment forms enve lopes around sed iment grains and im preg- was re named Stolleyites planus (Frebold, 1929), because nates or ganic-rich par ticles, such as fae cal pel lets and mi- var. plana was mentioned first by Frebold. 164 K. P. KRAJEWSKI & W. WEITSCHAT

Fig. 8. The Bravaisberget For mation (Mid dle Triasic–Carnian) in southern most Spitsbergen. A. Geo log i cal map of the south ern most part of Spitsbergen show ing lo ca tion of the Bergnasen (KS) and Keilhaufjellet (KL) sec tions of the Bravaisberget For mation. Ge ol ogy af - ter Winsnes et al. (1993), Dallmann et al. (1993b, 2002), and un pub lished ma te ri als of the pres ent au thors, simpli fied. B. Pan oramic pho - to graph of the south ern coast of SÝrkapp Land, showing lo ca tion of KS and KL sec tions on the west ern and east ern sides of Mathiasbreen, re spec tively. Pho to graph taken from SÝrkappÝya.

DIS CUS SION tween the depositional areas of the forma tions, but also a dif fer ent char acter of domi nant clastic source for the shelf The Mid dle Tri as sic sed i men tary cy cle in Svalbard sed i men ta tion. It is plau si ble that the fa cies con trast be - shows a transgressive-re gres sive fa cies ar range ment (MÝrk tween the forma tions was enhanced by a northward tectonic et al., 1989; Pèelina, 1998; MÝrk and Worsley, 2006; Basov displace ment of the West Spitsbergen Fold-and-Thrust Belt et al., 2009), though the shallow-shelf Bravaisberget For- and the as so ciated tec tonic struc tures rel a tive to the East ern mation is charac ter ized by much more complex and vari able Svalbard Platform (Dallmann et al., 1993a; Faleide et al., facies distri bu tion than the deep-shelf Botneheia Forma tion 2008; HÝy and Lundschien, 2011; Leever et al., 2011). This (Fig. 3). This re flects a gen eral dif fer ence in bathymetry be - dis place ment would have jux ta posed the re pos i to ries of the BRAVAISBERGET FOR MATION IN SOUTH ERN SPITSBERGEN 165

Fig. 9. Bergnasen (KS) sec tion of the Bravaisberget For mation. Find ings of Stolleyites planus are in di cated. For fur ther ex pla na tion, see text. for ma tions that orig i nally oc cu pied dif fer ent lo ca tions on tion, the major sedi ment source was located in close prox- the Trias sic Barents Shelf (Fig. 1A). im ity (west and southwest of the present coast of Spits- The Botneheia Forma tion was built up of sedi ments bergen), most proba bly in the land area of northern Green - transported from distant deltaic systems on the south-east- land (Riis et al., 2008; Worsley, 2008). In southern Spits- ern Barents Shelf (GlÝstard-Clark et al., 2010; HÝy and bergen, the land termi nated along the SÝrkapp-Hornsund Lundschien, 2011), which formed a major embayment north High. The facies devel op ment of the Bravaisberget Forma - of the Fennoscandinavian Shield (Laursen et al., 2006; tion points to a supply of fine-grained clastics during the Basov et al., 2009; GlÝstard-Clark et al., 2011). The influ - transgressive and high-stand phases of the Mid dle Trias sic ence of local sedi ment sources was subor di nate in Spitsber- cycle, which re flected a tec toni cally qui es cent period in the gen and negli gi ble in eastern Svalbard. As a conse quence, land area. Depo sition was con trolled by subsi dence in west- the Botneheia Forma tion shows subtle facies changes in the ern Spitsbergen and by the stable posi tion of the SÝrkapp- fine-grained sed i ments, in flu enced mostly by in ter play be- Hornsund High, a part of which formed an emergent struc- tween the distal prodelta and the open-shelf depositional ture af ter its ini tial flood ing in Dienerian (Nakrem and systems (Krajewski, 2013). For the Bravaisberget Forma - MÝrk, 1991). The sudden appear ance of the deltaic depos its 166 K. P. KRAJEWSKI & W. WEITSCHAT

Faleide et al., 1991), though there is lim ited knowl edge on the Trias sic evo lu tion of this tec tonic unit (Czuba et al., 2008; Faleide et al., 2008; Henriksen et al., 2011). The sandy fa cies of the Somovbreen Member straddles the SÝrkapp-Hornsund High and extends basinward over a distance of about 50 km (north and east of Bellsund). Its out line marks the max i mum ma rine re dis tri bu tion of sed i - ments deliv ered to the Svalbard basin by the south-western deltaic system. De spite the coarse-grained na ture of the del- taic depos its of the Karentoppen Member, the sandstones of the Somovbreen Member are fine-grained and frequently silty, grading into siltstones and mudstones. They are exten - sively bioturbated, showing common traces of winnow ing and sed i ment re work ing. The mi cro scopic sur vey re vealed that they are quartz-dom inated with an admix ture of glau- conite, and con tain in ter vals of con cen tra tion of de tri tal zir - con and rutile. This facies devel op ment sug gests a pro- longed pe riod of low sedi men ta tion rates and com mon sedi - ment re cy cling in a shal low-shelf en vi ron ment af ter the deltaic input. Gravely beach depos its observed at RÝysneset indi cate the presence of a rocky shore in close proxim ity to the delta outlets. The gen eral change of the na ture of clastic sed imen ta- tion from the Passhatten Mem ber to the Somovbreen Mem- ber did not af fect phosphogenic condi tions in the shelf en vi- ronments of southern and western Spitsbergen (Krajewski, 2000a, c; Krajewski et al., 2007; Pèelina and Korèinskaja, 2008). This is a strong evi dence of the contin u ation of high bi o log i cal pro duc tiv ity, re lated to nu tri ent sup ply from the oceanic basin during and after the event of deltaic input (Krajewski, 2011). The inflow of fresh water into the shelf basin was insuf fi cient to im pact on the authigenic processes in the marine facies, which supports the suppo sition of short-lived activ ity of the south-west ern deltaic sys tem. It has been suggested that the maxi mum flooding sur- face during the Mid dle Trias sic cycle in Svalbard (both Botneheia and Bravaisberget forma tions) was located in a sed i men tary in ter val show ing the high est con cen tra tion of marine organic carbon (Karcz, 2010; Krajewski, 2013). Fig. 10. Keilhaufjellet (KL) section of the Bravaisberget Forma - This in ter val re flects ad vanced stag na tion and ox y gen def i - tion. Find ings of Stolleyites planus are indi cated. For further ex- cit in the drowned shelf envi ron ments under ly ing a surficial pla na tion, see Fig. 9 and text. zone of high bi o log i cal pro duc tiv ity (Basov et al., 2009; Krajewski, 2013). The highest concen tra tion of marine or- ganic carbon was noted in the middle part of the Blanknuten Member of the Botneheia Forma tion (massive phosphatic of the Karentoppen Mem ber above the or ganic-rich Pass- mudstone facies of Krajewski, 2013), which was dated as hatten Member or di rectly on older strata in SÝrkapp Land early Ladinian in cen tral and east ern Svalbard (Weitschat in di cate an event of tec tonic ac tiv ity in the source area and and Lehmann, 1983; Weitschat and Dagys, 1989; Houn- rapid supply of clastics to the south-western margin of the slow et al., 2008). This age is consis tent with the suggested Svalbard basin. This sup ply changed the na ture of marine age of the Mid dle Trias sic maxi mum flooding surface in sedi men ta tion in southern Spitsbergen, from mostly muddy deltaic sys tems of the southern Barents Shelf (GlÝstard- envi ron ments before the event to sandy ones after it. Clark et al., 2010; HÝy and Lundschien, 2011). The massive The source area for the deltaic de pos its seems to be phosphatic mudstone in the Blanknuten Member occurs be- miss ing in the present geo logi cal struc ture of the NW tween the 75-m and 90-m levels in the 105-m-thick section Barents Shelf, owing to Late Cre taceous– Ce no zoic rift ing of the Botneheia Forma tion at Blanknuten (Krajewski, and the sepa ra tion of Greenland from the East Euro pean 2008), and be tween the 90-m and 110-m levels in the 130 m Craton (Faleide et al., 1993; Riis et al., 2008; Worsley, thick sec tion at VikinghÝgda (Krajewski and Weitschat, 2008; Smelror et al., 2009). A part of it (about 40 km wide) unpubl. ms.; see also Hounslow et al., 2008, fig. 5). The could be located on the margin of the Barents Shelf, off the max i mum con cen tra tion of ma rine or ganic car bon was west ern coast of SÝrkapp Land (NÝttvedt et al., 1988, 2008; noted in the upper part of the Passhatten Mem ber of the BRAVAISBERGET FOR MATION IN SOUTH ERN SPITSBERGEN 167

Fig. 11. Lithostratigraphy and fa cies of the Bravaisberget For mation in the vi cin ity of Mathiasbreen. A. East ern slope of Bergnasen showing lithostratigraphic sub di vi sion of the Tri as sic suc ces sion and the di rec tion of KS sec tion of the Bravaisberget For mation. Lo ca tion of find ings of Stolleyites planus is indi cated. B. Lower part of the Somovbreen Member at Bergnasen showing suc ces sion of fine-grained sand stone with re cur rent rows of phos phate nod ules. Ham mer is 40 cm long. C. Rows of pristine (pn) and allochthonous (an) phosphate nod ules sep a rated by win nowed sur face (ws) in the lower part of the Somovbreen Mem ber at Bergnasen. D. Rocky cliff at foot of the west - ern slope of Keilhaufjellet showing di rec tion of KL sec tion of the Bravaisberget For mation. Lo ca tion of find ings of Stolleyites planus is in di cated. E. Phosphatic ho ri zon in the up per part of the Somovbreen Member at Keilhaufjellet con sists of phosphatic ammonoids pre- served at var i ous stages of me chan i cal re working. Sec tion per pen dic u lar to bed ding. Ham mer is 40 cm long. F. Ammonoids in phosphatic ho ri zon shown in (E). The ex ter nal parts of the fossil moulds are ce mented by phosphate (p), and the inter nal rings are filled with later blocky cal cite (c). 168 K. P. KRAJEWSKI & W. WEITSCHAT

Fig. 12. Phosphatic ammonoids in the Somovbreen Member of the south ern most SÝrkapp Land. A. Pristine phos phatic ammonoid in KL sec tion. Note the compactional in jec tion struc ture of sandy sedi ment de vel oped in the lower part of in ter nal rings be fore cal cite ce menta - tion of the voids. B. Re worked phosphatic ammonoid in KL section. Me chan i cal frag menta tion of the phos phatic in fill ing oc curred be fore cal cite ce men ta tion of the voids. C. Carbon ate fluorapatite fringe cement (p) in in ter nal rings of phos phatic ammonoid contrib utes to per - fect im print of the orig i nal phragmocone anat omy. Note small geopetal struc tures made of polyframboidal py rite (pf). The re main ing pore space and mouldic pores af ter dis solu tion of the skele ton are filled by blocky cal cite ce ment (c). D. Mul ti lay ered ap a tite fringe ce ment with seams of py ritic microcrystals (p) coat ing ammonoid septum (am). The sep tum was dissolved dur ing early diagenesis and infilled by a sequence of phosphate and calcite cement. Void space in the phragmocone was infilled by later blocky cal cite (c). E. Apa tite fringe ce - ment (p) with py rite framboids (pf) de vel oped on ammonoid septum (am). The mouldic pore af ter dis solu tion of the sep tum and the in ter - nal void were infilled with later blocky cal cite (c). F. Clastic sed i ment fill ing ammonoid phragmocone shows apa tite fringe ce ment (p) on detri tal quartz grains (q) and moulds of sili ceous sponge spicules (s), and ap a tite im preg na tions of fae cal pel lets (f). Clus ter-like ap a tite ce - ment (cl) and polyframboidal pyrite (pf) are seen in inter-parti cle pore space. The remain ing voids were filled by calcitic sparite (c). (A, B) – thin-sec tion pho to graphs; (C–F) – combined trans mitted- and re flected-light pho to micro graphs, par al lel nicols. Scales in (A) and (D) are for (A, B) and (D–F), re spec tively. BRAVAISBERGET FOR MATION IN SOUTH ERN SPITSBERGEN 169

Fig. 13. Stolleyites planus (Frebold). A, B. Sample KL-1C.1 from KL sec tion at Keilhaufjellet (see Fig. 10 for sam ple lo ca tion). Cal - cite-filled middle ontogenic stage. The su ture lines are accen tu ated by thin apa tite fringe ce ment.

Bravaisberget Forma tion in Bellsund (the inter val between Somovbreen Member is typi cal for south-western SÝrkapp the 100-m and 118-m levels in the 160-m-thick section of Land. It provides the most complete record of sedi men ta tion the Passhatten Mem ber at Bravaisberget; Karcz, 2010) and of the Somovbreen Member. These hori zons join one an- close to the top of this mem ber in Hornsund (the inter val be- other to form a condensed phosphorite hori zon occur ring at tween the 50-m and 53-m levels in the 54-m-thick section of the top of the Somovbreen Member further northeast in the the Passhatten Member at Treskelen; Krajewski, 2000c). fold belt. This is thought to re flect de creasing depositional These organic-rich in ter vals in the Passhatten Member lack rates and in creas ing con den sa tion to gether with in creas ing biostratigraphic dating. However, it is reason able to assume distance from the coastal envi ron ments. The condensed ho- that they consti tute an isochronous ho rizon related to the rizon contains phosphatic ammonoids of the family Nathor- maxi mum flooding of Spitsbergen during the Mid dle Trias - stitidae (?Stolleyites sp.). It can be traced from AustjÝkultin- sic cy cle, which should cor re late with a simi lar ho ri zon in den in NE SÝrkapp Land through inner Hornsund (Bautaen– the Blanknuten Mem ber (Fig. 14). These data sug gest that Hyrnefjellet) to Bellsund (Bravaisberget–Bravaisodden). the sup ply of deltaic clastics to south ern Spitsbergen oc- Stolleyites planus has been found at several places in curred shortly af ter the maxi mum flooding of the basin, i.e. cen tral and east ern Spitsbergen (Milne Edwardsfjellet, at the end of or af ter the early Ladinian. Hence, the old est Teistberget, Roslagenfjellet) in a thin, discon tin u ous phos- marine clastics of the Somovbreen Mem ber should be phatic black shale unit (blue-weather ing), oc curring just roughly of the same age. above the cliff of the Blanknuten Mem ber of the Botneheia The dis cov er ies of Stolleyites planus in phosphate-bea- Forma tion (Weitschat and Dagys, 1989; Dagys and Weit- ring hori zons of the upper part of the Somovbreen Member schat, 1993; Dagys et al., 1993; Hounslow et al., 2007). in the Kistefjellet-Keilhaufjellet area bear wit ness to the Korèinskaja (2000) reported the presence of Stolleyites pla- con tin u a tion of ma rine sed i men ta tion and phosphogenic nus and Daxatina canadensis from the same stratigraphic con di tions through the Mid dle-Late Tri as sic bound ary. In level on EdgeÝya. This thin shale was consid ered to be the Svalbard, Stolleyites planus de fines the lower Stolleyites basal deposit of the Tschermakfjellet Forma tion. The top of planus Subzone of the S. tenuis Zone, which is the first bio- the cliff-form ing suc ces sion of the Blanknuten Mem ber stratigraphic zone of the Carnian (Weitschat and Dagys, contains a con densed phosphorite hori zon that under lies the 1989; Dagys and Konstantinov, 1992; Dagys and Weit- dis con tin u ous phos phatic shale unit. The over ly ing si der it ic schat, 1993; Korèinskaja, 2000). The fossiliferous phospha- (pur ple-weather ing) shales of the Tschermakfjellet For ma - te-bearing hori zons observed in the Kistefjellet-Keilhau- tion contain Stolleyites tenuis in the lower part of the suc- fjellet area are also found at Fisneset north of Stormbukta, cession (Korchinskaya, 1972a; Korèinskaja, 1972b, 1982; indi cat ing that this de velop ment of the upper part of the Dagys and Weitschat, 1993; Dagys et al., 1993). In the 170 K. P. KRAJEWSKI & W. WEITSCHAT

Fig. 14. Strati graphic scheme of the Bravaisberget Forma tion of south ern and west ern Spitsbergen and its suggested cor re la tion with the Botneheia Forma tion of cen tral and east ern Spitsbergen and east ern Svalbard. LFZ – Lidfjellet-yrlandsodden Fold Zone; WSFTB – West Spitsbergen Fold-and-Thrust Belt; CSB – Cen tral Spitsbergen Ba sin; ESP – East ern Svalbard Plat form (in clud ing cen tral Spits- bergen). For fur ther ex pla na tion, see text.

opinion of the authors, the classi fi ca tion of the thin phos- mineral phase of the fossil mould. This contrasts with the phatic shale to the base of the Tschermakfjellet For ma tion low organic content of the overly ing shales of the Tscher- was a con se quence of failure to discrim i nate be tween the makfjellet For mation (c. 1 wt.% TOC), which con tain al - Botneheia and Tschermakfjellet shales in the boundary in- most ex clusively woody organic matter (kerogen type III), ter val, which at many places is compli cated, ow ing to listric sider ite cement, concre tions, and fossil moulds; and are faulting and décollement structures (Hounslow et al., 2007, very poor in authigenic pyrite and devoid of sedi men tary 2008). Mi cro scopic and geo chem i cal in ves ti ga tions in di - phosphate. These findings are consis tent with the recent in- cate that this shale has char ac ter istics typi cal of the Botne- ves ti ga tions of Xu et al. (2014) who located the Ladinian- heia shales, i.e. it contains large amounts of marine organic Carnian boundary in the upper most part of the Botneheia matter (up to 11 wt.% total organic carbon – TOC) and For ma tion. Hence, the sub stan tial hi a tus sug gested for the Tasmanites algae (kerogen type II/I), phos phate nod ules, boundary between the Botneheia and Tschermakfjellet for- phosphatic fossil moulds, and authigenic pyrite; and it lacks ma tions (Hounslow et al., 2006a, b, 2007) should be located sider ite concre tions and cement (Krajewski, 2008, 2013). below the condensed phosphorite hori zon in the upper most X-ray dif fraction of a Stolleyites planus col lected from this part of the Botneheia Forma tion (Fig. 14). On southern shale at Roslagenfjellet in Agardhbukta (eastern Spitsber- BarentsÝya and possi bly at other places on the East ern gen) in dicates that carbon ate fluo- rapatite is the dom inant Svalbard Platform, the depo si tion of this hori zon was pre- BRAVAISBERGET FOR MATION IN SOUTH ERN SPITSBERGEN 171

ceded by an erosional event that removed a part of the ar range ment is com plex, re sult ing from the in ter play be- cliff-forming succes sion (Krajewski, 2013). The changing tween regional processes on the Barents Shelf and local pro- po sition of the up per Ptychid Layer with Aristoptychites, cesses, re lated to tec tonic ac tiv ity along the ba sin margin Ussurites and Daonella (late Ladinian) in sec tions of the and chang ing condi tions in the shallow shelf en viron ments. Blanknuten Mem ber in central and east ern Spitsbergen 3. The follow ing stages of depo si tion of the Bravais- (from 14 m to 2 m below the phosphorite conglom er ate), berget Forma tion can be discerned: and the presence of reworked moulds of Aristoptychites and a) Or ganic-rich, dom i nantly fine-grained sed i men ta - Ussurites in the phosphorite conglom er ate in Spitsbergen, tion of the Passhatten Mem ber during the transgressive and on EdgeÝya and southern BarentsÝya in di cate that the ero - high-stand phases of the Mid dle Trias sic cycle. This sedi - sion/con den sa tion was a re gional event dur ing ter mi na tion menta tion extended from west ern Spitsbergen south ward of the phosphogenic envi ron ments in Svalbard (Köhler- after the Anisian transgres sion; it reached the topmost part Lopez and Lehmann, 1984; Weitschat and Dagys, 1989; of the SÝrkapp-Hornsund High during maxi mum flooding Dagys et al., 1993; Krajewski and Weitschat, unpubl. ms.). of the shelf basin in early Ladinian. The supply of fine- The data presented above suggest that the upper most grained clastics indi cates a tec toni cally qui es cent pe riod of inter val of the Somovbreen Member of the Bravaisberget the adja cent land area. Phosphogenic condi tions were com- For ma tion in south-west ern SÝrkapp Land, which grades mon in the or ganic-rich en vi ron ments and par tic u larly in- into the condensed phosphorite hori zon in the remain der of tense on subma rine silty-sandy bars that migrated between southern and western Spitsbergen, can be corre lated with muddy de pressions (Krajewski, 2000c; Krajewski et al., the con densed phosphorite hori zon and the as soci ated phos- 2007). phatic shale at the top of the Blanknuten Member of the b) The sud den appear ance of the deltaic depos its of the Botneheia Forma tion in cen tral and east ern Svalbard (Fig. Karentoppen Mem ber in SÝrkapp Land di rectly af ter maxi - 14). These depos its repre sent the youngest phosphogenic mum flooding of the shelf basin. This was a conse quence of en vi ron ments in Svalbard that are already of the ear liest short-lived event of tectonic activ ity in the south-western Carnian age. Hence, the Van Keulenfjorden Member that source area. Rapid uplift and erosion of this area brought overlies the Somovbreen Member in southern and western about the input of coarse clastics to the basin margin through Spitsbergen should be consid ered to be Carnian in age. It re- narrow delta out lets sepa rated by rocky shores. The eroded pres ents clastic sed i men ta tion in mar ginal- to shal low-ma - substra tum was domi nated by acidic rocks and/or products of rine en vi ron ments that were char ac ter ized by the abun dance the sed i men tary re cy cling of them. The moun tain ous land- of sili ceous sponges and by the lack of either phosphate or scape, at least in part, was covered by veg eta tion. sider ite authigenesis. The de po sition of the mem ber seems c) Shal low-ma rine re dis tri bu tion of the deltaic clastics to have been confined to a part of the early Carnian. It in- un der sup pressed sed i men ta tion rates. Ces sa tion of the del- cluded a time period corre spond ing to the hi atus be tween taic activ ity and a re gional regres sive trend in the Barents the top most part of the Botneheia Forma tion (phosphogenic Shelf in late Ladinian contrib uted to the rework ing of the marine facies of the S. planus Subzone) and the lower most deltaic clastics into finer frac tions and their re dis tri bu tion in part of the Tschermakfjellet For mation (si derit ic prodelta Spitsbergen. The sandstones and siltstones of the Somov- fa cies of the S. tenuis Subzone) in cen tral and east ern Sval- breen Member form a bulge that extended into the shelf ba- bard. However, on the basis on available palaeontological sin for a distance of about 50 km. Low sedi men ta tion rates data (Pèelina, 1967; 1983, 1985, 1996; Korèinskaja, 1972b, contrib uted to the forma tion of glauconite grains, com mon 1982) the exact time of termi na tion of depo si tion of the Van bioturbation of the sedi ment, and widespread phosphoge- Keulenfjorden Member is diffi cult to es timate. nesis. Outside the sandy/silty bulge, there were depos ited phos phatic “oolitic” grainstones that required subma rine hiatal con di tions and re cur rent re work ing/win now ing of the CONCLU SIONS sea bed. d) Basinward con den sa tion dur ing ter mi na tion of the 1. The Bravaisberget Forma tion of southern Spitsber- depo sition of sandy/silty phosphogenic facies of the So- gen (Mid dle Tri as sic–Carnian) rep re sents a marginal part of movbreen Member at the Middle-Late Trias sic boundary. the organic-rich, phosphogenic depositional system that de- These en vi ron ments seem to re flect fluc tu at ing sea-level veloped in Svalbard in response to an event of high bio log i - dur ing a tec toni cally qui es cent period close to the end of the cal produc tiv ity on the Barents Shelf. The ba sin margin was regres sive phase. Recur rent flooding of the basin margin af- bounded on the southwest by the SÝrkapp-Hornsund High, fected phosphogenic epi sodes that contrib uted to the forma - a posi tive tectonic structure that marked the border of an tion of phosphate-bear ing hori zons in the coastal envi ron - emergent area lo cated further southwest. North of the high, ments of south-west ern SÝrkapp Land. They were sep a rated the subsid ing shelf bottom stretched from southern to west- by re gressive events that provided clastic supply to the ern Spitsbergen. coastal en vi ron ments, though in tense sub ma rine re work ing 2. The Bravaisberget For mation shows a general fa cies and/or erosion domi nated in areas remote from the shore. distri bu tion and thickness changes that reflect a transgre- e) An event of siliciclastic and spiculitic de posi tion of ssive-re gres sive cy cle over the mar ginal part of the ba sin. It the Van Keulenfjorden Member. This event re flects pe cu - forms a wedge of organic-rich depos its thin ning to ward the liar condi tions that devel oped along the basin margin during SÝrkapp-Hornsund High, where they are re placed by ma- the early Carnian. It resulted in the forma tion of a contin u- rine and deltaic sandy fa cies. However, the de tailed fa cies ous clastic hori zon in southern and western Spitsbergen that 172 K. P. KRAJEWSKI & W. WEITSCHAT

shows the abundance of sili ceous sponges and common rents Shelf. Ma rine and Pe tro leum Ge ol ogy, 54: 167–179. traces of early diagenetic silici fi cation of the sed iment. The Arkhipov, Y. V., 1974. Stratigrafija Triasovyh Otložhenii Vos- fa cies de vel op ment in di cates shal low- to mar ginal-ma rine toènoj Yakutii (Stra tig ra phy of the Tri as sic De pos its of East - envi ron ments. This unit is missing in the remain der of Sval- ern Yakutia). Yakuttskoe Knižnoje Izdatelstvo, Yakuttsk, 270 bard; it is not recog nized in other parts of the Trias sic Ba- pp. [In Rus sian.] rents Shelf. Bäckström, S. A. & Nagy, J., 1985. Depositional his tory and fauna of a Ju ras sic phosphorite con glomer ate (the Brentskardhau- 3. At least two corre la tion hori zons between the Bra- gen Bed) in Spitsbergen. Norsk Polarinstitutt Skrifter, 183: vaisberget and Botneheia forma tions can be suggested (Fig. 1–61. 14): Basov, V. A., Vasilenko, L. V., Viskunova, K. G., Korago, E. A., a) Track ing a ho ri zon with max i mum con cen tra tion of Korèinskaja, M. V., Kupriyanova, N. V., Povysheva, L. G., marine organic carbon in the fine-grained facies of the Pas- Preobrazhenskaya, E. N., Pèelina, T. M., Stolbov, N. M., shatten and Blanknuten members would help to reveal the Suvorova, E. B., Suprunenko, O. I., Suslova, V. V., Ustinov, po sition of the maxi mum flooding surface during the Mid - N. V., Ustritsky, V. I. & Fefilova, L. A., 2009. Evoljucija dle Tri as sic transgressive-re gres sive cy cle. Its sug gested lo - obstanovok osadkonakoplenija Barencevo–Severo-Karskogo cation is in the middle part of the Blanknuten Member in paleobassejna v fanerozoe (Evo lu tion of sed i mentary en vi - eastern Svalbard and central Spitsbergen and in the upper ron ments of the Barents–North Kara palaeobasins in the Pha- part of the Passhatten Member in western Spitsbergen. nerozoic). 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Amer i can As so ci a tion of Pe tro leum Ge ol o gists. lo gis ti cal sup port of the Pol ish Polar Sta tion in Hornsund and the Den ver.] research vessel SSB Horyzont II. Field as sistance from Przemy- BjorÝy, M., Hall, P. B. & MÝrk, A., 2006. Tri as sic hy dro car bon s³aw Karcz, Marcin Klisz, Bartek Luks, Stanis³aw Mazur, Tomasz source rocks on Svalbard and in the Barents Sea. In: Nakrem, Nowicki, and Mateusz Zab³ocki at dif fer ent stages of the geo log i - H. A. & MÝrk, A. (eds), Bo real Tri as sic. Ab stracts and Pro - cal work is greatly ap pre ci ated. This is a con tri bu tion to the pro ject ceed ings of the Nor we gian Pe tro leum So ci ety, 3: 42–45. “Paleoenvironments of the Tri as sic or ganic car bon-rich fa cies in Buchan, S. H., Challinor, A., Harland, W. B. & Parker, J. R., 1965. Svalbard” at the Insti tute of Geolog i cal Sciences of the Polish Aca- The Tri as sic stra tig ra phy of Svalbard. 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