Leslie Kanat and Alan Morris A working stratigraphy for central western Oscar Il Land, Spitsbergen NORSK POLARINSTITUTT OSLO 1988 Leslie Kanat and Alan Morris A working stratigraphy for central western Oscar Il Land, Spitsbergen ------�.... _-_ .... _---- NORSK POLARINSTITUTT OSLO 1988 Cooer page. Deformation in the Chaotic Zone. Two textural oceurrcnccs of veining are common in dolostonc within the Chaotic Zonc. In this drawing, fine grained, rccrystallizcd catadastic quartz (stipp1c) was injcctcd by later quartz vcin (strained) within a massive dolomitic host. The fine graincd texture (stipplc) is typ;cal for quartz in whieh catacl.sis was followcd by rccrystallization accommodated dislocation crcep. Scale bar: 0.5 mm. ISBN 82-90307-52-7 Norsk Polarinstitutt. Printed December 1988 Rolfstangveien 12, 1330 Oslo Lufthavn, Primcd in Great Bruam by Page Bros (Norwkhi Lld Norway Contents Abstract " ,.. ,.... , ........ , .. ,."." ..", ... "... '"",.,., ..."".""""""""".,.",." .. " .....",."""",'.'.', .. '"".","' .... ',, ' .. , , ,., " ,,'. 5 Introduction ,.', , ,."" .. , ,., .. ,., " '" ,.. "'."" ,.""."".,.... , .. "."".",.,.,., ..", .. , ..."."",."."""",.".,.""",.""""""""""", 7 Strandtlat strip rocks (CAR)", .... ... ".""".""." ........ "", .................... , ....... " ... " ... , ...... ,."... ""., .. ,,, 8 Bullbreen Group ..., ",.""., ,.,.... , , .... , .. ,.,.. ' " ..., , .., ,.,.,., ",.. , ,.. , ,.'.", .." ,.,'... , ,... , , .., , .. , ,.. " .. '".. "., ",.", ."., "'" ,.. ", ,., 9 Holmesletfjella Formation (BHI-6)" ...., ..." ,' .. ,.",., ,.,.. "...... , ....... ,.",... ','.'"", .. ", .., "." .. , .... , ",.,""'" "'"",',' .., .., lO Motalafjella Formation (BMI) ,."."., .., , ... , ,.",., '... " .... ,' .. ,.. " ....." ,.. , ,.,.,.", "'""" ,." ,.' ..... , .., ,... , ,.,.", '.,." "'",."". 13 Sarsøyra Formation (SZI-2) ......... , .. , .. ,., ,., .. """'" ,.. ""., ... , ... , ......, """ ,' .. ""... ,,, ...... , ...... ,., .. ,."., .. "", .... ,....... , .. " 14 ComfortJessbreen Group",.,.",.".. ",."""",.. "".", .. " .." .." ..", .. , .. "."",.".",.""",.",.. " ... " .. " .. ,., ... "." .. ",.. " "."". 14 Aavatsmarkbreen Formation (CV!-3) .............................. " ........................." ................. , ..,.... ..... ............... !4 Annabreen Formation (CA!) . ,." .. " '., .... , ...... " ".., ... " ,.. " , .. ,,'o '" .. " ,.... ...... ,." " ,.. " , .. " ,., .. '" .. " .. , ... .... , ..... .. , .. , ••' !4 }{aaken Formation (CHI-2) " .., .... , .........................., ...., ............" ........ ".. " .., ...... , ...................... ,.... , .... ,.... , .. , 14 St. Jonsfjorden Group",.", .. ,."."., .. ,... ",.. ",." .. ", .., .... , .."",., ..... ",.",., .... """,.".",.,.,.,."".,... " .. ",."""." , ,., "". , 16 Løvliebreen Formation (SLl·2) .... ",........ , ........ ,.... , ....................................... , ........ ' , .... ,.. ,..... , .. " "" .., .. ,.. ,,,, .., 16 Alkhorn Formation (SA!·2) .. ".. ,............... "........ , .... , .... ,........................... " .........., , .... ,.......... , 16 Miillerneset Formation (MVF) .. ,." . ,." ."""", . ,",." ", ",., ",. , " ." ... " " .,."" " " ,",'O , . ". " , •• " .,." " ,," ,." ." " ,'" ,.,., , ••, .", 17 Vestgotabreen Structural Complex" .. ""...... , "", ... ' ,.",.. ""." .... " ... " .., "" ,." '... ' .. ,., .. " ....... , .... , ... ,.'"", ",." ... ".... ,.. 17 Dolostone division (VOD) .... ... ... ... , ...................... ...................... , .... , .................................. , ,,'................. 18 Micaceous marble division (VM!-2) .. " ........, ...... , ......, ......, .... ", ...... ,.................... , .... , ................., .... "...... 19 Mafic schist division (VSH) ............. ..... ............................. " ..., ...., ...... " .." .. " ........................, .. " .........., ...... , 19 Scrpentinite division (VSP) .""'.".,."."",.,.""""".", ..""""",.,." .. , .. ",... " ... ,.""""."".""", .. "".""",.""""",,, 19 Pelitie sehist division (VPE) ........................, ..........., .... ,.......... ,.... , ................... , ........, .... , .... ,,,"'" .............. ,.. ' 19 Greenstone division (VGT) ", .. ",,., ,.. " ... ", ...... " ... ,, ... "',",., ,' ... ',.. " .." ......., ,... ", ... ",, .. ', ... ' ..", .., .." , .., ,.. 20 Psammite division (VPS) , ..... , ............. " ........., " ........ " ...... ".................... , ..... " ...... " .................. ,,,.. , " .. ,.. , .... , 20 Garnet glaucophane division (VGG) ......... " ...................., ........................................ ,.......... , .................., .., .. , 20 Eclogite division (VEC) .., .........................., ............................, ...... ,,..................... , .. , .., .... .....,,, ...... , 21 Chaotic Zone " ", .. " ,,., '" ,., " ,,,'o , •• " •••• " .,.,." ., , •• , ,••,'.,. " " ., ,." ,., •• ". , "' .','." ,,, " ' " " ., ,." ,." , ••, , ••• , , .,.' ,., , ••• ", ." ,., ••" , 21 Concluding remarks ", ..", .., ..... """"""" " .. , "'" .. ", ,.".. , ............., .. "" " .., "." ... , ........... ", ....... ", .. "" .." .. , ...., ....,.. 21 Acknowledgements " """"""." ...., ,., """,'",' ,.. ",... ",.", .".".", " "., ".',.'"'.'.",.,,, .".,."" ",., ., ,.,., , ,... , "."""'" 21 References ,... ,............ , .......... .........., ...., ...................... ,.... ,....... , ... , .................. , ,........ ' ....... ................... 22 Plate"""""",. ", """".,."""".", """"""..", .. "."".,."""",.. ,.""." .." .. """""""""".""",."" .. ",.,.""""".",." 24 Abstract A modified stratigraphy for the pre-Carboniferous rocks in central Oscar Il Land, Spitsbergen, is needed to rcconcile reccnt mapping with earlier interpretations. Outerop maps and lithological dcscriptions for the Bullbreen, Cnmfortle"brcen and St. Jonsfjorden Groups, the Miillernesel Formalion, and Vestgotabreen Structural Complcx are presented, The contacl at Ihe base of the upper Ordovician Bullbreen Group was originally unoonformable, although it is now thrust at most loealities. A new internal stratigraphy for the Group is prescnted, and a revised sequcnee for the St. Jonsfjorden Group is described based On tbe rccognition of sedimentary oontacts not previously observed, A change in name from Vestgotabreen Formation to Vcstgotabreen Structural Complex is proposed, and severai new rock units within this eomplex are deseribed. Deposilion of the Bullbreen Group rcsulted from uplifl of the Vestgotabreen Complex, Continued orogenesis, rclaled lo mid,Paleozoic plate motion, drove bolh units over the Comfortlessbreen and SL Jonsfjorden Groups. us/le Kanal, Departmenl of Earlh Sciences, Univer.ity of Cambridge, Downing Street, Cambridge CB2 3EQ. England; Present address: College of Scienæs and Engineering, Division of Earth and Physical Sciences, The University of Texas at San Antonio, SanAntonw, Texas 78285-0663, U.S.A.; Alan Morris, College of Sciences and Engineering, Division of Earlh and Physical Sciences, The University of Texas at San Antonio, San Antonio, Texas 78285-0663, U.S.A. Introduction forrned nature of the rocks, unit thicknesses are necessarily estimates. The aim of this paper is to erect a working litho­ Uncertainty exists regarding the nature of the stratigraphic succession for central western Oscar original contacts and age of some lithologic units Il Land, Spitsbergen (Table 1). Three different in Oscar Il Land. However, there is general agree­ accounts of the stratigraphy and structure of ment on the following points: Oscar Il Land and Prins Karls Forland were pub­ 1. A significant discontinuity occurs between lished in 1979 (Harland et al. 1979; Hjelle et the Bullbreen Group (Harland et al. 1979; Ohta al. 1979; Krasiltschikov & Kovaleva 1979). The et al. 1983) and the Vestg6tabreen Structural outerop pattern in the study area closely follows Complex. that presented by Harland et al. (1979) and their 2. A late Ordovician depositional age (most nomenclature is largely adopted in this work, likely Caradoc through Liandovery) for the although we propose a name change for the Bullbreen Group (Armstrong et al. 1986; Scrut­ Vestg6tabreen Formation (formerly the Vest­ ton et al. 1976) and a mid-Paleozoic metamorphic g6tabreen Suite (Horsfield 1970; Ohta 1979)) to age for the Vestg6tabreen Structural Complex Vestg6tabreen Structural Complex. Waddams (Horsfield 1972). It is also probable that dia­ (1983) indicated that two diamictites in different mictites which occur in Oscar IT Land are Vendian groups occur in Oscar Il Land, but our field in age (Knoll 1981; Hambrey 1982,1983). observations do not support this interpretation in 3. The rock units represent distinet meta­ the St. Jonsfjorden area. In the following account, morphie facies: Vestg6tabreen Structural Com­ the his tory of research is included with the pl ex - blueschists and eclogites; Miillerneset description of each unit in order to preserve name Formation - upper greenschist to amphibolite precedence. facies; St. Jonsfjorden and Comfortlessbreen Pre-Carboniferous rocks in western Spits­ Groups - lower greenschist facies; Bullbreen bergen have undergone both mid-Paleozoic and Group - extremely low grade metamorphism; Paleogene orogenesis (see for example Harland Carboniferous rocks - unmetamorphosed. 1961; Birkenmajer 1972,1975,1981; Harland & Place names are given in Fig. 1,and the outerop Horsfield 1974). As a result of the highly de­ pattern of the rocks in the St. Jonsfjorden area is CENTRAL WESTERN SPITSBERGEN U)r BRGGERHALVØYA