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An offshore transgressive–regressive mudstone-dominatedsuccession from the Sinemurian of Skåne, Sweden

Nils Frandsen and Finn Surlyk

A Sinemurian mudstone-dominated succession was exposed until recently in the Gantofta quarryin Skåne, southern Sweden. The deposits are placed in the Döshult and Pankarp Members ofthe Sinemurian–Aalenian Rya Formation. Similar facies of the same age are widespread in theDanish Basin where they constitute the F-Ib unit (F-I member) of the Fjerritslev Formation. TheGantofta succession thus represents the easternmost extension of the environment characteris-tic of the Fjerritslev Formation and is essentially the only locality where it has been possible tostudy the facies of this formation in outcrop. Sedimentation seems to have taken place under rel-atively quiet tectonic conditions except for the possible fault-control of the basin margin. Thelower part of the Gantofta section is of Early and early Late Sinemurian age. It represents theupper part of the Döshult Member and consists of muddy, lower shoreface sandstones, abruptlyoverlain by dark, bioturbated, fossiliferous mudstones with thin storm siltstones and sandstones.They are overlain by the Upper Sinemurian Pankarp Member which comprises red-brown,restricted marine calcareous mudstones with an upwards increasing number of storm siltstonesand sandstones reflecting general shallowing and shoreline progradation.

The succession spans the greater part of two simple sequences with a distal sequence bound-ary located at the boundary between the Döshult Member and the Pankarp Member. The exposedpart of the lower sequence includes a thick transgressive systems tract and a very thin highstandsystems tract. The upper sequence is represented by an undifferentiated transgressive and high-stand systems tract. An Early Sinemurian sea-level rise, a late Early Sinemurian highstand, an earlyLate Sinemurian fall and a Late Sinemurian minor rise and a major fall are recognised. Nearby bore-holes show evidence for an end-Sinemurian – Early Pliensbachian major rise. This evolution cor-responds well with trends recorded in the subsurface Fjerritslev Formation of the Danish Basin.

Comparison with published European and British Jurassic sea-level curves show similar over-all trends, but exhibit differences in the precise ages of sequence boundaries and maximum flood-ing surfaces. This may reflect poor biostratigraphical resolution of the Gantofta section, differencesin sequence stratigraphic interpretation, real differences in the age of sequence stratigraphic keysurfaces, or the basin marginal position of Gantofta in the Fennoscandian Border Zone.

Keywords: Skåne, southern Sweden, Lower Jurassic, Sinemurian, facies analysis, sequence stratigraphy, sedimentary

environments, sea-level change

N.F., DONG, Agern Allé 24–26, DK-2970 Hørsholm, Denmark. E-mail: nfr@dong.dk

F.S., Geological Institute, University of Copenhagen, Geocenter Copenhagen, Øster Voldgade 10, DK-1350 Copen-

hagen K, Denmark.

Geological Survey of Denmark and Greenland Bulletin 1, 543–554 (2003) © GEUS, 2003

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Jurassic sedimentary rocks occur in great thicknessesin the subsurface of Denmark and southern Sweden(Michelsen 1978; Norling et al. 1983; Nielsen 2003, thisvolume). They are, however, only exposed in a few rel-atively small outcrops on Bornholm in the Baltic Sea,and in Skåne, southern Sweden, in the FennoscandianBorder Zone (Fig. 1; Sellwood 1972; Rolle et al. 1979;Gravesen et al. 1982; Norling et al. 1983; Surlyk & Noe-Nygaard 1986; Ahlberg et al. 2003, this volume). Thisintensely block-faulted zone forms the north-easternboundary of the Danish Basin. Detailed facies, bio-stratigraphic and sequence stratigraphic studies ofexposed units are thus of outstanding importance inobtaining a more detailed picture of the sedimentaryenvironments prevailing during Jurassic time in south-ern Scandinavia.

The aims of the present paper are to interpret thefacies and sequence stratigraphy of the Sinemurian off-shore marine deposits exposed in the Gantofta quarryin Skåne, southern Sweden, to place the succession inits regional context, and to compare the derived sea-level curve with the sea-level curves of Haq et al. (1988),Hallam (1988) and Hesselbo & Jenkyns (1998).

Geological setting and stratigraphyGantofta is located close to the NW–SE-trending westernmargin of the Fennoscandian Border Zone (Fig. 1). Themargin is characterised by a major faulted flexure formedby Late Cretaceous – Palaeogene tectonic inversion whichmarks the transition to the major depocentre of the DanishBasin to the south-west (Norling 1981, fig. 37).

The locality is a small clay pit (150 x 100 m) whichwas abandoned some years ago and the section is thusno longer easily accessible. The ammonites from thesuccession were described by Reyment (1969a, b), theforaminifera by Norling (1972), the palynology by Lund(1977), the ostracodes by Sivhed (1977, 1980, 1981) andthe sedimentary facies and environments by Frandsen(1977), Rolle et al. (1979) and Pienkowski (1991a, b).The succession is 70 m thick and consists of sandstonesand mudstones of the Lower – lower Upper SinemurianDöshult Member and the Upper Sinemurian PankarpMember, which constitute the two lower members ofthe Sinemurian–Aalenian Rya Formation (Sivhed 1984;Ahlberg et al. 2003, this volume). The whole succes-sion is tilted, and the strata strike 140° and dip 30° SW(Fig. 2).

Vomb Trough

FyledalenFault

Gantofta

25 km

HöganäsBasin

MalmöTrough

HanöBay

Kullen

I

I

II

II

I

II

I

I

I

I

I

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I

I

II

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I

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IIII

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I

Sweden

DK

Bornholm

II

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Rhaetian and Jurassicpresent distribution

Fault active in the Jurassic

Post-Jurassic fault

N

Norway

Ängelholm Basin

Fig. 1. Map showing the location ofGantofta in the Fennoscandian BorderZone of southern Skåne. ImportantJurassic structural features are indicated;note that Jurassic normal faults weresubsequently inverted in the LateCretaceous – Palaeogene. Based onNorling & Bergström (1987). DK, Denmark.

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A foraminifer fauna from the middle part of theDöshult Member at the base of the exposure indicatesan Early Sinemurian age (Norling 1972). An ammonitefauna including Asteroceras obtusum (Sowerby) andPromicroceras planicostatum (Sowerby) from a level2 m below the base of the overlying Pankarp Memberis of early Late Sinemurian obtusum Chronozone, plan-icostatum Subzone age (Reyment 1969a). K. Hoffman(in: Bölau 1959) reported the occurrence of the birchiSubzone (top of the turneri Chronozone) immediatelybelow the base of the Pankarp Member. The ostracodefaunas of the Döshult Member indicate a latest EarlySinemurian to Late Sinemurian age (Sivhed 1977). Norling(1972) suggested that the succession spans the timeinterval of the semicostatum to obtusum Chronozones.A new find of the ammonite Euagassiceras cf. lundgreniReyment in the basal muddy sandstone of the sectionsuggests a mid Early Sinemurian semicostatum Chrono-zone age for this level (probably resupinatum Subzone).This is in agreement with Bölau (1973).

Correlative strata are widely distributed in the DanishBasin where they form the F-Ib unit (F-I member) ofthe thickly developed, uniform mudstone package ofthe Fjerritslev Formation (Michelsen 1975, 1978, 1989;Pedersen 1985, 1986; Michelsen et al. 2003, this volume;

Nielsen 2003, this volume). The succession of theGantofta quarry consists of similar facies and thus essen-tially represents the only locality where it has been pos-sible to study the characteristic facies of the otherwisedeeply buried Fjerritslev Formation in outcrop.

SedimentologyA detailed sedimentological log of the succession wasmeasured in 1975–1976 by Frandsen (1977). Specialemphasis was placed on recording primary sedimen-tary structures, body and trace fossils, and details of con-cretions and other diagenetic features were also noted.Five sedimentary facies are recognised and are describedbelow followed by an interpretation of the depositionalprocesses and environments.

Sedimentary facies

Muddy sandstone (facies 1)

This facies consists of fine- to very fine-grained quartzsandstone with a mud-rich matrix. It is only known

Fault

N

A

B

BA

II

II

II

II

I

II

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II

II

I

Katslösa Mb

Pankarp Mb

Coal Seam

Mudstone

Sandstone

Gantofta Quarry Fault

II

200 mUpper Sinemurian

Lower Sinemurian

200 m

Döshult Mb

Fig. 2. Geological map and section (A–B)of the Gantofta area. Modified fromSivhed (1981).

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sem

icost

atum

Chr

onoz

one

(?re

supi

natu

m S

ubzo

ne)

obtu

sum

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onoz

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(pla

nico

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um S

ubzo

ne)

Trace fossilsChondrites isp.

Rhizocorallium isp.

Diplocraterion isp.

Planolites isp.

Skolithos isp.

Pyritic tube

Teichichnus isp.

Bioturbationincreasing density

Body fossilsBivalves,suspension feeders

Bivalves,deposit feeders

Bivalve fragments

Gastropods

Ammonites

Belemnites

Scaphopods

Serpulids

Brachiopods

Echinoid spines

Shark teeth

Ostracodes

Foraminifers

Sequence stratigraphySequence boundary

Maximum flooding surface

Transgressive surface of erosion

Transgressive systems tract

Highstand systems tract

Parasequence

SB

MFS

TSE

TST

HST

Ps

TSE

TST

MFS

HST

TST

HST

Dös

hult

Mb

Pank

arp

Mb

Dös

hult

Mb

LithologyMudstone

Calcareous mudstone

Silty and sandy mudstone

Silt- and sandstone

Carbonate cemented

Conglomerate

StructuresParallel lamination

Parallel lamination withsiltstone lenses

Cone-in-cone structures

Clay ironstone concretions

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y

Silt

Sand

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Sand

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Ps

70m m

65

60

55

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35

2

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SB

Faci

es

Seq.

Stra

t.

Fig. 3. Sedimentological section showing the biostratigraphy, chronostratigraphy and sequence stratigraphy of the Sinemurian suc-cession at Gantofta.

from the base of the section (Fig. 3). Shelly coquinaswith quartz granules occur at some levels. The colourvaries from light grey to dark grey. The sandstone isalmost totally bioturbated and the original structures arecommonly difficult to recognise. However, fine bio-genic lamination caused by high densities of the tracefossil Teichichnus isp. is a characteristic feature of thefacies. Siderite is the dominant cement, whereas themost indurated beds have a calcitic cement.

The trace fossils include Teichichnus isp., Diplo-craterion isp., Rhizocorallium isp., Chondrites isp., Plan-olites isp. and Zapfella isp.; the last of these occurs aselongate borings in shells of the bivalve Liogryphaeaarcuata.

The facies contains a fully marine fauna of body fos-sils which occur in rather high densities. Frandsen (1977)compiled a list of the fauna and documented the pres-ence of species described from other localities byTroedsson (1951). A taxonomic revision has not beenattempted. The fauna includes the bivalves Liogryphaeaarcuata, Chlamys textoria, Chlamys interpunctata,Entolium sp., and Oxytoma sinemuriensis, the ammoniteEuagassiceras cf. lundgreni Reyment, and indetermi-nate belemnites, echinoids, serpulids, ostracodes andnodosariid foraminifera. Coalified wood occurs as scat-tered pieces up to 6 cm long. The preservation of theshells is quite variable. Some are well-preserved andunworn, while others occur in coquinas and have clearlyundergone some transport and destruction.

The combination of marine body and trace fossils,intense bioturbation, shelly coquinas and a sand-dom-inated grain size indicates deposition under well-oxy-genated marine conditions with normal salinity andrelatively low sedimentation rates, periodically inter-rupted by higher energy events resulting in erosion,reworking and transport of shells. The taphonomic con-ditions suggest that the fauna can be considered a neigh-bourhood assemblage representing a fauna which livedin the area and which underwent only limited transport.The muddy nature of the sandstone suggests that theoriginal facies was a sand-dominated, possibly flaser-bedded heterolith, but the very high degree of biotur-bation does not allow a detailed process interpretation.

Dark grey mudstone (facies 2)

The mudstone of this facies characterises the bulk ofthe exposed part of the Döshult Member (Fig. 3). It hasa high content of silt and fine sand. Silt and clay areroughly equally abundant, and the clay is dominated

by kaolinite with some illite and chlorite. Coaly detri-tus, muscovite, very small shells and shell fragments,and framboidal pyrite nodules (0.1–0.3 mm in diame-ter) are characteristic constituents. A few intervals, upto 1 m thick, have a relatively higher content of sandand can be classified as muddy sandstones.

The mudstone is laminated with light coloured lam-inae of coarse silt, 1 mm thick. Clay ironstone is a char-acteristic component and occurs as bedding-parallelsiderite impregnated layers, 5 cm thick, with ellipsoidalconcretions, 5–20 cm long. Thin conglomerate bedsconsisting of reworked clay-ironstone concretions arefound at the 35.05 m and 38 m levels (Fig. 3). Carbonateconcretions with cone-in-cone structures occur at sev-eral levels.

The facies is strongly bioturbated, especially in thesandier portions, but several recognisable trace fossilswere noted, including Diplocraterion isp., Skolithos isp.,Rhizocorallium isp. (which has only been recordedfrom the clay-ironstone conglomerate) and Chondritesisp. Pyritic tubes, 0.2–1.0 mm in diameter, probablyrepresenting burrows of small deposit feeders, and?Planolites isp. occur throughout.

This facies and the laminated siltstone–sandstonefacies (facies 3) contain a rich shelly fauna. The twofacies and their faunas are closely related and their fau-nas are described together here. The carbonate shellshave undergone dissolution and are mainly poorly pre-served, but wear due to transport appears to be negli-gible. Liogryphaea arcuata is relatively rare and thespecimens are smaller than those of facies 1. Twospecies of Chlamys and minute specimens of Oxytomasinemuriensis have been found. A major difference infaunal composition compared to facies 1 is the abun-dance of deposit-feeding bivalves of the Nuculanacea(Nuculana, Palaeoneilo, Rollieria, Leda) and Nuculacea(Nucula). Bivalves belonging to Cardinia, Astarte,Homomya and Pleuromya or related genera also occur,but the determinations are uncertain. Small, high-spiredgastropods representing a number of different generaare very common. Poorly preserved scaphopods, brach-iopods, ammonites and rare shark teeth occur at sev-eral levels.

The fine-grained muds were deposited from sus-pension in an offshore open marine environment. Thecontent of silt and sand probably represents materialtransported to the area during storms. Bioturbation thenresulted in mixing of the fine and coarser fractions, anddestruction of primary current-produced structures. Thehigh density and diversity of body and trace fossilsshow that the water was of normal salinity and well-

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oxygenated. The abundance of deposit feeders is acommon characteristic of fine-grained, nutrient-rich sed-iments, whereas the abundant small-sized gastropodssuggest the presence of a marine vegetation.

The clay ironstone layers were formed under con-ditions of negative Eh, low concentration of sulphideions, high activity of ferrous ions, and the presence ofbicarbonate ions. Following Sellwood (1971) it is sug-gested that iron was transported to the marine envi-ronment and deposited as insoluble ferrioxide whichwas adsorbed on clay minerals. The siderite nodulescontain undeformed trace fossils and the mudstoneshows compaction features around the nodules whichwere thus formed after burrowing but before com-paction.

Laminated siltstone–sandstone (facies 3)

This facies varies in grain size from coarse silt to finesand, but grains up to granule size occur set in a muddymatrix. It forms beds up to 1–2 m thick and is commonlyinterbedded with facies 2. More than 95% of the grainsconsist of quartz. Other components are plagioclase,muscovite and coaly grains. Nodules of framboidalpyrite with a diameter of 0.1 mm occur locally. Thecement consists mainly of calcite.

The facies is parallel laminated, but structurelessintervals are also observed and primary structures arecommonly obliterated by bioturbation. Laminae are nor-mally 1–2 mm thick, and may be graded from fine sandto coarse silt. Thin laminae of shell hash occur locally.

The facies is strongly bioturbated. Recognizable tracefossils include rare Skolithos isp., Chondrites isp., Rhizo-corallium isp. with protrusive spreiten, and ?Pygospi-oides isp. which is very similar to Chondrites, but moreclosely resembles Pygospioides isp. as described fromthe Hettangian of Niedersachsen by Häntzschel &Reineck (1968). ?Planolites isp. traces occur through-out the facies. Body fossils are described under facies 2(see above).

The coarse siltstones and sandstones of this faciesprobably represent distal offshore storm deposits(Pedersen 1985), but the pervasive bioturbation pre-cludes an unequivocal interpretation.

Variegated mudstone (facies 4)

This facies and facies 5 characterise the Pankarp Memberin the upper part of the section (Fig. 3). It differs from

facies 2 in the red-brown colour and a finer grain sizedominated by clay and silt. Some levels are light-greywith a greenish tinge. The colour difference from facies2 is associated with a greater content of iron; the redvariety is richer in ferric and poorer in ferrous com-pounds than the greenish variety. The facies showssome lamination and upwards in the succession thinlenticular silt ripples start to appear.

A few indeterminate bivalves and some pyrite-impreg-nated nodosariid foraminifers have been found. Thefacies was deposited under low energy conditions,probably in a marginal marine environment as inferredfrom the impoverished fauna and the scarcity of bio-turbation compared to facies 2 and 3.

Calcareous siltstone and mudstone (facies 5)

The facies consists of intimately interbedded, soft, var-iegated claystone and siltstone of the same type asfacies 4, and harder light grey coarse siltstone and veryfine sandstone. Up to 60–70% of the sediment consistsof calcite while quartz, clay and some muscovite con-stitute the remaining part. The calcite occurs as recrys-tallized cement and grains of uncertain origin.Comminuted coaly fragments occur throughout.

The facies shows an almost varve-like grading with5–17 mm thick beds. The graded beds pass from lightgrey, calcite-rich clay into red clay, poor in calcite. Thelower boundaries of the graded beds are sharp and thetops are flat or gently undulating. Some of the thicker,coarser-grained beds show parallel lamination passinginto low-amplitude hummocky cross-stratification. Thesebeds also display load structures, groove casts, flat-lying folds and wrinkle marks on their upper surfaces.The wrinkle marks are very similar to the Kinneya rip-ples of Reineck & Singh (1980).

Trace fossils are scarce, typically represented by scat-tered 3–4 mm wide subhorizontal burrows, whereasTeichichnus isp. and subhorizontal Rhizocorallium isp.with protrusive spreiten are found in the upper coarser-grained part of the succession. Body fossils are only rep-resented by scattered shell fragments.

The fine grain size and the scarcity of trace and bodyfossils suggest deposition under very low energy con-ditions in a marginal or high stress marine environ-ment. The graded beds probably represent depositionfrom storm-induced suspension clouds (Pedersen 1985).The upwards increase in grain size and in the frequencyof beds displaying parallel lamination and hummockycross-stratification indicate increasingly storm-influenced

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deposition. The sum of characters thus indicates depo-sition under low energy conditions interrupted by sud-den influxes of storm-derived sediments. The environ-ment may have been distant offshore or more likely arelatively protected shallow marine area where theavailable grain sizes were very fine and where theeffects of storm events were relatively subtle. The redcoloration and the presence of Kinneya-type wrinklemarks lend some credence to the latter hypothesis. Thewrinkle marks may have been caused by a strong windblowing over a cohesive, fine-grained sediment coveredby only a thin veneer of water, possibly with a micro-bial mat growing on the sea floor under environmen-tally stressed conditions (Reineck & Singh 1980). Theyare thus indicative of near emergent conditions. As indi-cated on the geological map (Fig. 2), a coal seam is sit-uated slightly above the studied section. This also sug-gests that facies 5 was deposited in a marginal tonon-marine environment.

Depositional environmentFacies 1–5 form a regular vertical succession with facies1 at the base and facies 5 at the top, and interbeddingonly occurs between facies 2 and 3. The section thusincludes a basal muddy sandstone, a lower dark greyunit and an upper unit dominated by light grey and red-brown colours. The sedimentary structures and grainsizes do not show any marked changes and the mainmechanisms of transport and deposition seem to havebeen rather uniform. The whole succession is thus con-sidered to represent an association of genetically relatedfacies.

The basal part of the association consists of muddysandstone (facies 1; only 1.2 m exposed). It is followedwith a sharp boundary by a unit dominated by dark greymudstone with clay-ironstone layers (facies 2), 37.7 mthick, with numerous intercalations of thin siltstone andsandstone beds (facies 3). This unit is overlain with asharp contact by a variegated mudstone unit, 14.9 m thick,(facies 4), which gradually gives way to a succession ofcalcareous mudstones and siltstones (facies 5); 15.9 mof this last unit was exposed in the 1970s.

The succession is interpreted to reflect changes inrelative sea level in an area with uniform subsidenceand relatively constant sediment influx. Thus, facies 1represents slow deposition in a well-aerated shallow shelfsea. The muddy sand was originally deposited as alter-nating thin layers of mud and thicker layers of sandwhich were thoroughly mixed by bioturbation in the

offshore transition to lower shoreface zone close towave-base. The sharp boundary to the overlying mud-stones of facies 2 is interpreted as a ravinement surfacecaused by combined drowning and transgressive ero-sion when coarser clastic material was trapped in estu-aries and other inshore environments.

The main part of the succession represented by mud-stone with coarser-grained intercalations (facies 2 and 3)was deposited in deeper offshore areas with periodicinfluxes of silt and sand from storm-generated sus-pension clouds. Most of the silt and sand beds werethoroughly bioturbated and their identity as storm depositsbecame less obvious. The unit shows an upwardsdecrease in the density and diversity of body fossils cul-minating at the almost barren 35 m level (Fig. 3). Thetop 4 m of the unit are again rich in body fossils. Thistrend is interpreted to have resulted from transgressionand increasing water depth associated with a decreasein oxygenation followed by a regression combined withincreasing oxygenation at the sea floor.

The variegated mudstones of facies 4 and 5 overliethe dark grey mudstone with a sharp contact (38.9 min Fig. 3) and are somewhat difficult to interpret envi-ronmentally. They have the finest grain size of thewhole succession indicating very low energy condi-tions during deposition. The red colour and the occur-rence of wrinkle marks or Kinneya ripples suggestwell-oxygenated, very shallow water conditions. The sed-iments were possibly derived from erosion of fine-grained red beds of Triassic age exposed in a nearbysource area. The upwards increase in storm siltstonesand sandstones suggests coastal progradation, whereasthe scarcity of body and trace fossils suggests a mar-ginal marine or high stress environment. The generallyfine grain size points to deposition in a sheltered, some-what enclosed area. The variegated mudstones withstorm siltstones and sandstones of facies 4 and 5 thusseem to have been rapidly deposited in a very shallowmarine, restricted environment under the influence ofstorms.

Sequence stratigraphy The Döshult Member can be divided into six or sevencoarsening-upwards units, about 2–8 m thick, withsharp upper boundaries (Fig. 3). They are typical exam-ples of distal parasequences (Van Wagoner et al. 1990).Thin fining-upwards units, 10–20 cm thick, are notassigned any sequence stratigraphic significance butare interpreted as bioturbated storm siltstones and sand-

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stones. The parasequences stack into a parasequenceset which shows a subtle overall fining-upwards trendaccompanied by a distinct decrease in density and diver-sity of body and trace fossils (0–25 m in Fig. 3). Thetrend is interpreted as an overall backstepping stack-ing pattern which culminates in the poorly fossiliferousinterval between 25 m and 35 m in the upper part ofthe Döshult Member (Fig. 3). A few thin conglomeratesrich in body and trace fossils occur between 35 m and38.9 m.

The dark mudstones of the Döshult Member (facies2) are overlain by the Pankarp Member with a sharpconglomeratic boundary at 38.9 m. This unit comprisesabout 30 m of variegated, and red-brown, almost unfos-siliferous mudstones which contain an upwards increas-ing number of thin storm siltstones and sandstones.

The slowly deposited fully marine muddy sandstonesat the base of the section are interpreted to belong tothe lower part of the transgressive systems tract. Theyare capped by a sharp erosional drowning or ravine-ment surface formed by transgressive marine erosion(TSE in Fig. 3). The overlying dark mudstones form theupper part of the transgressive systems tract (TST inFig. 3). Lowstand deposits cannot be recognised andwere probably not deposited in the area. The trans-gressive marine erosion surface corresponds to thelithostratigraphic boundary between units F-Ia andF-Ib (both F-I member) of the Fjerritslev Formation butis slightly younger than in most of the Danish Basin.The age of the erosion surface is close to the semi-costatum–turneri Chronozone boundary.

A distinct maximum flooding surface cannot be iden-tified on the basis of the available data but a maximumflooding zone is interpreted to occur at about 34 m(MFS in Fig. 3). The upper part, from 34 m to the topof the section may represent a simple highstand sys-tems tract. The siderite pebble conglomerate at 38.9 mis not easy to interpret in terms of sequence stratigra-phy. It occurs at a marked facies change from darkfossiliferous mudstones (facies 2) to variegated and red-brown almost non-fossiliferous mudstones (facies 4, 5).This change seems to represent a significant environ-mental change associated with a marked seawards shiftin facies and it is possible that it represents a distalsequence boundary. If this is the case then the high-stand systems tract of the underlying sequence is amaximum of 5 m thick and consists of dark, uniformmudstones at the top of the Döshult Member (34–38.9 min Fig. 3). This interpretation is tentatively preferredhere and the exposed Döshult Member thus includesa lower transgressive systems tract (TST), a transgres-

sive surface of erosion (TSE), a thick upper transgres-sive systems tract (TST), a maximum flooding surfaceor zone (MFS) and a thin highstand systems tract (HST)topped by a distal sequence boundary (SB; Fig. 3). Theoverlying Pankarp Member probably represents poorlydifferentiated transgressive and highstand systems tracts.

The fossiliferous siderite pebble conglomerate at theDöshult–Pankarp Member boundary may be interpretedas reworked hiatus concretions formed when sedimentsupply to the basin was shut off during maximum flood-ing (Hesselbo & Palmer 1992). This interpretation is, how-ever, considered unlikely due to the marked facies change,the seawards shift in facies and the associated inferredmajor drop in water depth across the boundary.

Correlation to the contemporaneous Sose BugtMember (Rønne Formation) on Bornholm in the BalticSea is hampered by the paralic, poorly fossiliferousnature of that unit (Surlyk et al. 1995). Dating of theGantofta succession is based on ammonites, ostracodesand foraminifera, whereas the Sose Bugt Member isdated on the basis of pollen in the lower part and a fewdinoflagellates in the upper part. A major sequenceboundary is situated close to the Hettangian–Sinemurianboundary in the Sose Bugt section. This correlates wellwith a sequence boundary at the base of the DöshultMember in Skåne, below the Gantofta section (Surlyket al. 1995). Two minor sequence boundaries are iden-tified in the Sose Bugt section in the Lower Sinemurianand in the middle Upper Sinemurian, respectively. Thelower sequence boundary occurs at a level roughly cor-responding to the top of the muddy sandstone (facies 1)at the base of the Gantofta section (1.2 m in Fig. 3),whereas the upper one may correlate with the interpretedsequence boundary at the sharp break between darkmudstones (facies 2) and variegated mudstones (facies4) at Gantofta (Döshult Member – Pankarp Memberboundary; 38.9 m in Fig. 3). This correlation may cor-roborate the interpretation of the erosional boundarybetween the Döshult and Pankarp Members as repre-senting the distal expression of a sequence boundary.It is remarkable that highstand systems tract depositsare almost absent in the Sinemurian Sose Bugt sectionwhich mainly consists of transgressive systems tractdeposits. This is thought to be typical of the more prox-imal, basin margin areas (Surlyk et al. 1995) and mayalso account for the thinly-developed highstand depositsat Gantofta which occupied an intermediate basinalposition between the paralic setting of the Sose BugtMember and the offshore Danish Basin. Higher partsof the Pankarp Member are known from boreholes sit-uated close to the Gantofta quarry. The red-brown, var-

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iegated and light grey mudstones of facies 4 and 5 areoverlain by 10–17 m of bluish-grey mudstone. This isfollowed by about 5 m of sand with an allochthonouscoal seam, 5–15 cm thick, representing a marked regres-sion (Sivhed 1980). The sand is overlain by about 15m of red-brown or bluish-grey mudstone. The PankarpMember spans the Upper Sinemurian oxynotum andmost of the raricostatum Chronozones. The nature ofthe lower boundary of the sand bed is not known anda sequence stratigraphic interpretation cannot be under-taken on the basis of the available data.

A relative sea-level curve constructed on the basisof the sedimentary evolution as interpreted here isshown on Figure 4. It is compared with the Jurassic eusta-tic sea-level curves of Haq et al. (1988) and Hesselbo& Jenkyns (1998). The overall trends of the curves areremarkably similar, but the exact ages of the main highsand lows differ somewhat. The Haq et al. (1988) andHesselbo & Jenkyns (1998) curves show the highestdegree of similarity although the latter is more detailedand shows more candidate sequence boundaries andmaximum flooding surfaces. The two curves show majorsequence boundaries in the uppermost Hettangian,uppermost Lower Sinemurian and uppermost Sine-murian, and maximum flooding surfaces in the middleLower Sinemurian and middle Upper Sinemurian.

The Gantofta curve is simpler due to a combinationof uniform facies development and lower biostrati-

graphical resolution. It differs from the curve of Hesselbo& Jenkyns (1998) in that they place the main Sinemuriansequence boundary at the base or immediately belowthe base of the obtusum Chronozone whereas it occurswithin this chronozone at Gantofta. The mismatchbetween the Gantofta curve and the two other curvesmay be due to the basin marginal position and the lackof lowstand deposits at Gantofta. The low biostrati-graphic resolution prevents identification of possible hia-tuses in the mudstone-dominated succession. Theeustatic signal may thus be overprinted by tectonismin the Fennoscandian Border Zone, by higher sedimentinput during transgression and condensation and bypassduring regression. Hallam (1988) did not give anydetailed zonal data for his transgressive and regressiveevents and his curve is thus difficult to compare withthe other curves.

ConclusionsUntil recently, a Lower Jurassic, Sinemurian marine suc-cession, 70 m thick, was exposed at the Gantofta local-ity in north-western Skåne, southern Sweden. Gantoftarepresents the only place where it has been possibleto study exposed strata of the same facies as the deeply-buried contemporaneous Fjerritslev Formation of theDanish Basin. The succession comprises the upper part

SB SB

SB

SBSB

SB

SB

SB

MFS MFS

MFS

MFSMFS

High Low High Low High Low

After Haq et al.(1988)

After Hesselbo & Jenkyns(1998)

This paper, Gantofta

200

195

Ma

jamesoni

Chrono-zones

rari-costatum

oxynotum

obtusum

turneri

semi-costatum

bucklandi

angulata

Upp

erU

pper

Low

erLo

wer

Pliensbachian

Stages Sea-level changes

Sinemurian

Hettangian

Fig. 4. Relative sea-level curve con-structed for the Gantofta successioncompared with the Jurassic sea-levelcurves of Haq et al. (1988) and Hesselbo& Jenkyns (1998); the time scale is afterGradstein et al. (1994). An ammonitefrom the basal muddy sandstone atGantofta suggests a mid-semicostatumChronozone age for this level. The levelof the obtusum Chronozone is welllocated and the lower part of thesuccession has a general EarlySinemurian age. The age of the post-obtusum Chronozone beds is not well-known but ostracode data suggest a LateSinemurian age (Sivhed 1980).MFS, maximum flooding surface;SB, sequence boundary.

of the Döshult Member and the lower part of the PankarpMember, both belonging to the Sinemurian–Aalenian RyaFormation. The basal 1.2 m of the Gantofta sectionexposed the uppermost levels of the sand-dominatedLower Sinemurian part of the lower Döshult Member.This overall transgressive, fluvial and lacustrine to shal-low marine succession is known from temporary expo-sures at nearby Örby where it is 32 m thick (Erlströmet al. 1999).

Five genetically related facies are recognised. Thelower half of the Gantofta section, representing theupper Döshult Member, is composed of three facies(1–3). The lowermost 1.2 m consists of Lower Sinemurianbioturbated, richly fossiliferous muddy sandstones (facies1), interpreted as having been deposited relatively slowlyin an offshore to transition zone environment. Theyare followed with a sharp contact by Lower – lowerUpper Sinemurian, dark grey, bioturbated, fossiliferousmudstones (facies 2) with intercalations of siltstonesand sandstones (facies 3). The mudstones representslow, fair-weather deposition below wave base underoffshore shelf conditions interrupted by deposition ofthin silts and sands from storm-generated suspensionclouds. The general low sedimentation rate and thedistal, thin nature of the storm deposits is reflected bythe pervasive bioturbation and mixing of both facies.

The succeeding Upper Sinemurian succession,referred to the lower Pankarp Member, comprises mar-ginal marine, variegated mudstones and red-brown cal-careous mudstones (facies 4, 5) with an upwards in-creasing number of storm siltstones and sandstonesreflecting general shallowing and progradation of thecoastline associated with restriction of the marine cir-culation. A fossiliferous siderite pebble comglomerateoccurs at the boundary between the Döshult andPankarp Members.

The succession encompasses the greater part of two,relatively simple depositional sequences. The basalmuddy sandstone is interpreted as belonging to thelower transgressive systems tract of the lower sequence.It is topped by a ravinement surface formed by trans-gressive marine erosion overlain by a backsteppingparasequence set representing the upper transgressivesystems tract. A maximum flooding zone is identifiedclose to the top of the dark Döshult Member mud-stones. It is overlain by a thinly developed highstandsystems tract topped by an erosion surface marked bythe siderite pebble conglomerate. The erosion surfaceis tentatively interpreted as a distal sequence bound-ary and the overlying variegated and red-brown PankarpMember mudstones belong to the poorly differentiated

transgressive and highstand systems tracts of the sec-ond sequence. Comparison with the sequence strati-graphy of the contemporaneous Sose Bugt Member(Rønne Formation) of Bornholm lends some credenceto this interpretation.

The Gantofta succession records an Early Sinemuriansea-level rise, a mid-Sinemurian highstand, an earlyLate Sinemurian sea-level fall followed by a LateSinemurian minor rise and subsequent major fall. Datafrom nearby boreholes indicate an end Sinemurian –Early Pliensbachian major rise. The sea-level curve con-structed on the basis of the Gantofta section is com-pared with the sea-level curves of Haq et al. (1988) andHesselbo & Jenkyns (1998) in Figure 4. It is remarkablethat the three curves show similar overall trends but thesequence boundaries and maximum flooding surfacesare delayed in the Gantofta curve compared to the twoother curves. This may reflect the basin marginal posi-tion of the Gantofta section in the Fennoscandian BorderZone with higher sedimentation rates during sea-levelrise and condensation or bypass during fall. Furthermore,the Gantofta curve is much simpler than the Hesselbo& Jenkyns (1998) curve. This is probably a direct resultof the poor biostratigraphic resolution of the Gantoftasection and the implicit difficulty in identifying hiatusesin the mudstone-dominated succession.

AcknowledgementsWe thank Ulf Sivhed for useful comments, Lars B. Clem-mensen for critically reading an early manuscript ver-sion and referees Stephen P. Hesselbo and Gunver K.Pedersen for constructive criticism. The study was sup-ported by the Carlsberg Foundation and the DanishNatural Science Research Council.

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Manuscript received 23 May 1997; revision accepted 13 October 1999.