UNIVERSITY OF GOTHENBURG Department of Earth Sciences Geovetarcentrum/Earth Science Centre

Petrography and sedimentary

facies of the lower

Cambrian succession at the

Kinnekulle table mountain,

south-central Sweden

- Implications for the late

Precambrian peneplainization and

early Cambrian transgression

Anders Eurenius

ISSN 1400-3821 B974 Master of Science (120 credits) thesis Göteborg 2017

Mailing address Address Telephone Telefax Geovetarcentrum Geovetarcentrum Geovetarcentrum 031-786 19 56 031-786 19 86 Göteborg University S 405 30 Göteborg Guldhedsgatan 5A S-405 30 Göteborg SWEDEN Abstract Kinnekulle, in south-central Sweden, is located in a region of table mountains where weathered Proterozoic gneiss is overlain by early Paleozoic strata, which have been preserved by Permian dolerite intrusions. The early and middle Cambrian (Stage 4 and 5) succession at Kinnekulle is here studied in a new drill core containing strata from the File Haidar (Mickwitzia Sandstone and Lingulid Sandstone members) and Alum Shale Formation. A stratigraphic log, together with petrographic descriptions and field observations from localities at Råbäcks hamn and Lugnås, form the basis for this study.

Results show that, in addition to the weathered gneissic basement, seven distinctly different sedimentary lithofacies can be recognized. These include: 1 – Massive polymict conglomerate, characterized by poorly sorted, sub-angular to rounded, fine to pebble-sized quartz and distinctly weathered feldspar; 2 – Interbedded sandstone and mudstone, characterized by cross-laminated and normally graded, fine-grained sand and bioturbated mud; 3 – Thickly bedded sandstone, characterized by cross-laminated or massive, fine to coarse-grained sandstone; 4 – Disrupted sand and mudstone, characterized by fine-grained sand and mudstone constituting homogenized zones, remnant original bedding, mudstone clasts and vertical tubes; 5 – Massive sandstone, characterized by very fine-grained, homogenous sandstone with thin, interspersed, silty and micaceous lamina; 6 – Sandstone-pebble conglomerate, characterized by internally sorted and vaguely imbricated sandstone-pebble clasts and fine-grained quartz matrix; and 7 – Black shale, characterized by laminated black shale interspersed with thin layers of limestone or fine-grained quartz-rich sand. Together, lithofacies 1 – 7 represent different types of deposition occurring in terrestrial and marine environments. They record a variety of processes related to marine storm and fair- weather sedimentation, fluvial currents, chemical weathering, cementation, bioturbation, and possibly eolian abrasion and soft-sediment deformation. The basement rock is characterized by distinct textures associated with Precambrian weathering. The lower Mickwitzia Sandstone Member includes a basal conglomerate that consist of sediment derived from different local sources and was reworked in a terrestrial environment. Reworking also occurred during the early Cambrian transgression, after which the conglomerate was chemically weathered and cemented. The conglomerate is followed by deposits of sandstone and mudstone that show an upward increase of storm-influenced facies associated with the lower shoreface. The overlying Lingulid Sandstone Member record deposition of overall homogenous and more bioturbated sands, possibly indicating relatively calm conditions. The early Cambrian sediment was lithified, indicating substantial burial. An erosion surface at the topmost Lingulid Sandstone Member marks the region-wide Hawke Bay unconformity, which was followed by an intra-basin conglomerate that developed during sub-aerial exposure and fluvial processes. The environment then changed rapidly from terrestrial to marine, represented by deposition of black shale that belong to the Alum Shale Formation. Key words: Early Cambrian, File Haidar Formation, Kinnekulle, Cambrian transgression, peneplainization, stratigraphy, sedimentary facies, petrography Table of contents 1. Introduction ...... 1 1.1. Background ...... 1 1.2. Aim and purpose ...... 1 1.3. Study area ...... 1 1.4. Geologic setting and stratigraphic framework ...... 2 Baltica and surrounding paleo continents of the late Precambrian to early Cambrian ...... 2 Lithotectonic units and peneplainization of the Baltic shield ...... 3 Precambrian and early Cambrian basins and sediment ...... 5 The early Cambrian shelf and highlands ...... 5 Regional extent of the lower Paleozoic cover rocks ...... 6 Sequence stratigraphy of the early Cambrian ...... 6 Clastic supply over the course of the early Cambrian ...... 6 The File Haidar Formation ...... 7 2. Material and methods ...... 9 2.1. Drill core...... 9 2.2. Localities ...... 10 2.3. Petrography ...... 11 2.4. Terminology ...... 12 3. Results and interpretation ...... 13 3.1. Stratigraphic log ...... 13 3.2. Gneissic basement ...... 22 3.3. Sedimentary facies ...... 24 Lithofacies 1: Massive polymict conglomerate ...... 24 Lithofacies 2: Interbedded sandstone and mudstone ...... 29 Lithofacies 3: Thickly bedded sandstone ...... 34 Lithofacies 4: Disrupted sandstone and mudstone ...... 37 Lithofacies 5: Massive sandstone ...... 41 Lithofacies 6: Sandstone-pebble conglomerate ...... 43 Lithofacies 7: Black shale ...... 45 4. Discussion ...... 46 4.1. Peneplainization and the development of the basal conglomerate ...... 47 4.2. Marine environments represented by the Mickwitzia Sandstone Member...... 51 4.3. Marine environments represented by the Lingulid Sandstone Member ...... 53 4.4. Development of the sandstone-pebble conglomerate and the following transgression ...... 55 5. Conclusions ...... 57 6. Acknowledgements ...... 58 7. References ...... 59

1. Introduction 1.1. Background Kinnekulle, a table mountain located in Västergötland, is one of the few places in south-central Sweden where the sub-Cambrian peneplain and the overlying cover rocks are both well preserved. The early Cambrian strata constitutes the File Haidar Formation, which is subdivided in the Mickwitzia Sandstone Member and the Lingulid Sandstone Member. The middle Cambrian to Ordovician constitutes the Alum Shale Formation.

The deposits in Västergötland have been preserved under protective dolerite sills (Calner et al., 2013), of which the one at Kinnekulle intruded in the Cisuralian (early Permian, 282 ± 5 Ma by Priem et al., 1968, as cited in Calner et al., 2013). Except for a few other occurrences mainly preserved in fault grabens, much of the Cambrian deposits of south-central Sweden have been eroded away, down to the underlying peneplain (Lidmar-Bergström, 2013). Remnants of the sub-Cambrian peneplain are well preserved in south-central and south-eastern Sweden, and likely extended over much of Baltoscandia (East Baltic countries and Scandinavia) during the dawn of the Cambrian period (Lidmar-Bergström, 2013).

The early Cambrian strata of Baltoscandia were largely deposited on this intra-continental, sub-Cambrian peneplain. According to Nielsen and Schovsbo (2011) and references therein, the early Cambrian rocks are largely marine sandstone and mudstone with rare intra-basin conglomerates. The deposits range in thickness from a few thousands of meters in the East Baltic area to a few tens of meters in Västergötland and Närke in south-central Sweden. The decreasing thickness is generally attributed to deposition further into the continental interior that experienced significantly less subsidence.

1.2. Aim and purpose The aim of the study is to describe the petrography and interpret the depositional facies of the rocks constituting the early and middle Cambrian at Kinnekulle. The purpose is to determine what material was produced and what this can tell us about weathering during the period of peneplainization. The purpose is also to distinguish changes in sea-level, depositional environment and depositional processes that dominated during the ensuing Cambrian transgression.

1.3. Study area Kinnekulle is located on the south-eastern shore of Lake Vänern (Fig. 1). The mountain is part of a district of table mountains including Billingen-Falbyggden, Halleberg and Hunneberg as well as Lugnåsberget. These table mountains represent intra-craton outliers of the Baltoscandian basin that is preserved in the present-day Baltic Sea and East Baltic Area. The preservation of the outliers is due to a resilient dolerite cover that intruded the sedimentary succession in the Permian (Calner et al., 2013). The stratigraphic succession rests on top of a widespread denudation surface, the sub-Cambrian peneplain (Lidmar-Bergström, 2013). The early Cambrian succession is comprised of the Mickwitzia Sandstone Member and the Lingulid Sandstone Member of the File Haidar Formation. The Mickwitzia Sandstone Member has been 1

shown to contain conglomerate, interbedded mudstone and sandstone, while the Lingulid Sandstone Member comprises massive sandstone (Jensen, 1997). This early Cambrian succession is capped by the widespread Alum Shale Formation of middle Cambrian to

Ordovician age (Nielsen and Schovsbo, 2011).

Figure 1. Shows (A) the location of south-central Sweden and the table mountains in the Västergötland-region. The district of table mountains consist of Kinnekulle, Billingen-Falbyggden, Halleberg and Hunneberg, and Lugnåsberget. Drill-core site and the localities studied are marked by numbers 1 – 3. Modified from Ahlberg et al. (2016). (B) The Kinnekulle table mountain, located on the shore of Lake Vänern. Kinnekulle constitute lower Cambrian through Silurian strata that rests on top of Precambrian basement rock. The drill-core site is marked by number 1, it is located at Dimbo near the summit of Kinnekulle. Modified after map information from the Swedish Geological Survey.

1.4. Geologic setting and stratigraphic framework Baltica and surrounding paleo continents of the late Precambrian to early Cambrian Following the break-up of Rodinia at ca 750 Ma, four major continental areas dominated the late Precambrian and early Paleozoic. These were Baltica, Laurentia, Siberia, and the supercontinent Gondwana (Torsvik and Hartz, 2002). Baltica had previously been amalgamated in a constellation together with Siberia and Laurentia, where the continental break-up that started with Rodinia, ended with separation of Baltica from Siberia at approximately 580 Ma on present-day western side of Scandinavia (Nielsen and Schovsbo; 2011; Kleina et al., 2015). At around 550 Ma, Gondwana was situated near the South Pole, while Baltica, Siberia and Laurentia were situated on mid-southerly latitudes (Fig. 2). Paleo- magnetic and paleontological evidence suggest that Baltica was rotated 180◦ in respect to the present orientation during the late Precambrian (Torsvik and Rehnström, 2001). Models in

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Torsvik and Rehnström, (2001) and Torsvik and Hartz (2002) show that Baltica was separated from Laurentia to the west, by what may have been a transverse fault zone. To the east, separating Baltica and Siberia, was a spreading zone opening the Aegir Ocean. To the south, Baltica was separated by a southward subduction zone toward Avalonia (Torsvik and Rehnström, 2001; Torsvik and Rehnström, 2003; Torsvik and Cocks, 2005). Moreover, early Cambrian fossil assemblages from the File Haidar Formation are largely comparable to other Cambrian assemblages from basins on Laurentia and China (Slater et al., 2017).

Figure 2. Paleogeographic reconstruction of the late Precambrian. Modified from Nielsen and Schovsbo (2011). Lithotectonic units and peneplainization of the Baltic shield According to Åhäll and Conelly (2008) as well as Roberts and Slagstad (2014), the basement rocks that made up the Baltic Shield, on which the early Cambrian sediments accumulated, is today largely exposed in western, eastern and south-central Sweden. These consists mostly of Palaeoproterozoic granitoids which is subdivided in three main lithotectonic units (Fig. 3B) including; the Transscandinavian Igneous Belt (TIB) that make up large parts of south-eastern Sweden (1.85 – 1.69 Ga). This unit is bordered to the west by the deformed Protogine Zone, which is followed directly westward by the more reworked part of the TIB. This reworked TIB is usually referred to as the Eastern Segment (1.71 – 1.65 Ga). The western border of the Eastern Segment constitutes the Mylonite deformation zone. Bordering directly westward of the deformation zone, is the Mesoproterozoic Gothian domain (1.66 – 0.92 Ga), also known

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as the Idefjorden terrane. Associated metamorphic overprinting is predominantly attributed to the Sveconorwegian orogeny (1.15 – 0.9 Ga).

Figure 3. Shows (A) the present day Baltoscandia (Scandinavia and the Baltic countries), (B) the geographical extent of the lithotectonic units in south-central Sweden, (C) the geographical extent of the sub-Cambrian peneplain and later denudation surfaces, (D) the geographical extent of lower Paleozoic cover rock. Re-drawn and modified based on Åhäll and Conelly (2008), Nielsen and Schovsbo (2011), Roberts and Slagstad (2014) and Lidmar-Bergström et al. (2013; 2017, submitted).

The sub-Cambrian peneplain is a vast denudation surface (Fig. 3C) that developed across the different lithotectonic units constituting the basement (Lidmar-Bergström et al. (2013). The existence of this major weathering and erosion surface along with overlying widespread shallow marine deposits imply tectonic quiescence in Baltoscandia during the Precambrian and early Cambrian.

According to Lidmar-Bergström et al. (2013), preserved parts of the peneplain today stretch from the inland part of the northern west coast of Sweden, toward the east where it makes

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up most of the southern east coast. Here it is also inclined toward the south-east. It terminates to the south-west with an erosional surface and to the south Småland peneplain. In south- central and southern Sweden, close to the Baltic Sea, it is buried under Cambrian and Ordovician strata. In close contact to cover rocks, the surface is very flat and has a relative relief of less than 20 m.

It is suggested that no tectonic movements along older Sveconorweigan or Svecokarelian fault and deformation zones were occurring during the development of the peneplain, due to the crosscutting of the peneplain over these units without any change in morphology. It is unclear, however, how much of the sub-Cambrian peneplain has been destroyed by later erosion. It has been inferred that much of the Baltoscandian part of Baltica consisted of this peneplain at the time of the Cambrian transgression (Nielsen and Schovsbo, 2011; Lidmar-Bergström, 2013).

Age estimates of the sub-Cambrian peneplain remains poorly constrained. There is a consensus that the peneplain formed sometime between the middle to late Proterozoic and the deposition of the early Cambrian rocks. In some places where Precambrian sedimentary rocks are preserved, for example in the Dalarna basin, it has been shown that the Precambrian basement rocks likely had developed low relief before the middle of the late Riphean (Lidmar- Bergström and Olvmo, 2015).

Precambrian and early Cambrian basins and sediment Local Precambrian basins in present-day Sweden and Norway include for example the Dalarna basin, Vättern rift basin as well as the Hedmark and Risbäck basins. The Hedmark and Risbäck basins was at the middle Vendian to Cambrian, a denuded craton margin (Winchester, 2012). The late Riphean and Vendian deposits of the Hedmark basin predominantly consists of parts dominated by fluvial sandstone and alluvial-fan conglomerates, and parts dominated by turbidites and shale; these are overlain by late Precambrian tillites, as well as fluvial sandstone, quartzite and siltstones and shale deposed near the Precambrian-Cambrian boundary (Nystuen, 1987). In the Risbäck basin, Varangerian glacial and glacio-fluvial sediment are overlain by post-Varangerian fluvial, deltaic and shallow marine sediment (Winchester, 2012). The Precambrian deposits in the Vättern rift-basin comprises largely Neoproterozoic alluvial fan deposits, fluvial and nearshore marine deposits as well as arkoses and quartz sandstones of the Visingsö group (Vidal, 1984). The deposits in the Dalarna basin constitute predominantly Jotnian quartz-sandstones with eolian dune-facies and muddy, wave-ripple interdune facies (Pulvertaft, 1985). The Precambrian deposits on the East European Platform consist of rift-associated sediment and volcanics related to the Volhyn aulacogen (Vidal and Moczydtowska, 1995), however, these are not considered to be part of the scope of this study.

The early Cambrian shelf and highlands According Nielsen and Schovsbo, 2011 and references therein, the early Cambrian north- eastern shelf of Baltica, which is now present-day western Scandinavia, was a passive margin with exceptionally low relief and that stretched from southern Sweden to northern Norway.

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The Timanide orogeny and associated fold belt was located in present-day northern Norway, and has been proposed to have heavily influenced sediment influx to foreland basins in that area. Further, in what is today the eastern Baltic, rift-related tectonism occurred during the Ediacaran and early Cambrian. In this area, the inversion of the Volhyn-Orcha Rift is believed to have caused uplift and erosion of sediments deposited in the post-rift basin, influencing the oldest Cambrian sediments (Rovnian-Lontovan, equivalent to early Terrenuvian) and later sedimentation in the easternmost Baltic Sea.

Regional extent of the lower Paleozoic cover rocks During the Cambrian transgression, the peneplenized Proterozoic basement rocks of Scandinavian were covered by sediments that would come to stretch over vast areas of Baltica. The extent of this sediment cover was obviously great because the existing remnants are widespread (Fig. 3D). The strata cover most of the Baltic countries as well as the southern Baltic Sea and major parts of Denmark. The lower Cambrian specifically, can be found in the Bothnian Sea and Bothnian bay, along with minor occurrences preserved in Närke, Östergötland, Billingen-Falbygden, Kinnekulle, Halleberg and Hunneberg, and in parts of the Oslo region (Nielsen and Schovsbo, 2011).

Sequence stratigraphy of the early Cambrian The sequence stratigraphic context of the early Cambrian at Kinnekulle is extensively discussed in Nielsen and Schovsbo (2011). They suggest that the lower Cambrian can be subdivided in two 2nd-order sequences that represent cycles of sea-level rise and fall, both which are terminated by subaerial exposure. These subdivisions are based on a sequence- stratigraphic interpretation of Baltic Cambrian sandstones, and a correlation of interpreted sequence boundaries. The first 2nd-order sequence corresponds to the global Cambrian Stage 3. This can in turn be subdivided into nine 3rd order sequences. This super-sequence ends with the Rispebjerg Lowstand which is likely due to glacio-eustatic changes. The second 2nd- order sequence span the lower and middle of Cambrian Stage 4 (equivalent to European Vergalian-Rausvian and lower Kibartian) and consists of five 3rd order sequences, and two or more 4th order sequences. The early Cambrian at Kinnekulle was deposited during the latter of these two super-sequences.

Clastic supply over the course of the early Cambrian According to Nielsen and Schovsbo (2011), the two 2nd-order sequences described above also represent two distinct depositional phases during the Cambrian transgression that have been identified in Baltoscandia, they represent high and decreasing clastic supply respectively. The high clastic supply characterizes Baltoscandia in the beginning of the early Cambrian, which is reflected by the rapid progradation following pulses of sea-level rise during an overall transgressive period. Wide sand belts showing tidal influence occurred in nearshore environments, as well as storm deposits on the inner shelf. It is likely that the distribution can be accounted for by dispersal and reworking of sediment in a basinward direction, due to low slope of the shelf and frequent storms. In the offshore environment, this dispersion of sediment gave rise to storm layers of sand interbedded into finer sediment. These eventually

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disappear toward the outer shelf where the sediment is dominated by greenish, reddish or grayish mudstones. In contrast, the decreasing clastic supply had a substantial effect on Baltoscandia during the second half of the early Cambrian, which is indicated by slowing progradation. Sediment was still coming from present-day Finland, present-day western Russia, Belarus and Scandinavia (approximately southern Norway and central Sweden); the stratigraphic thickness of the mudstones deposited in offshore areas were greatly reduced. Due to the limited supply of sediment, the periods of sea level fall likely resulted in non- deposition and erosion on the upper shelf, which is seen as outward displacement of facies and erosion of offshore fine sands due to lowering of the storm weather wave base.

The File Haidar Formation This summary of the File Haidar Formation is based on Slater et al. (2017) and references therein. The File Haidar Formation (Fig. 4) is of early Cambrian age and belongs to the global Stage 4 that span 514 – 509 Ma. This is equivalent to the upper part of the European Vergalian- Rausvian Stage. The formation consists primarily of fine to medium-grained sandstones, mud and siltstones. It overlies the weathered gneissic basement and is terminated by the widespread unconformity of the ‘Hawke Bay-event’. On Gotland, Öland as well as in the Bothnian Sea, the formation is overlain by the the Borgholm Formation (Grötlingebo Member) of middle Cambrian age (Stage 5). In south-central Sweden and the Olso region, it is overlain by the Alum Shale Formation of middle Cambrian and early Ordovician age. The sediment of the File Haidar Formation was deposited in a shallow epeiric sea, geographically outlined similar to the modern-day seas of the Bothnian and Baltic and characterized by the flatness of the Precambrian peneplain.

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Figure 4. Stratigraphic framework of the File Haidar Formation. Modified from Nielsen and Schovsbo (2011). As stated by Slater et al. (2017) and references therein, the File Haidar Formation is mainly documented from subsurface data of drill cores and its stratigraphy is based on acritarch biostratigraphy and sequence stratigraphic correlation. Shelly fossils are rare in the File Haidar Formation and mainly consist of trilobite fragments and brachiopods, whereas trace fossils are relatively abundant. Based on lithology and marker beds of conglomerate, the File Haidar Formation is subdivided in five members: the Mickwitzia Sandstone Member, the Lingulid Sandstone Member, the När Sandstone Member, När Shale Member and the Viklau Member. These members contain sediments deposited in a nearshore sand belt influenced by storms. The inner shelf is dominated by sand in the shallow marine setting, it is represented by the Mickwitzia Sandstone and Lingulid Sandstone members. The När and Viklau members are gradually transitioning into shales, this represent deposition at greater depth in the distal part of the inner shelf.

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2. Material and methods 2.1. Drill core The Kinnekulle-1 core (Fig. 5) was drilled at Dimbo, near the summit of mount Kinnekulle. This was done with the Swedish research drill-rig and its operative organization called Riksriggen (‘The National Rig’), in May 2016, for the Department of Geology, Lund University. The core has a total length of 220 m and includes the Cambrian, Ordovician and basal Silurian strata of the mountain. Coring was terminated a few meters down in the Precambrian gneissic basement. The drill core is stored at the Department of Geology, Lund University.

Figure 5. Photographs of the basal part of the Kinnekulle-1 core, drilled at Dimbo, near the summit of mount Kinnekulle. Box-numbers are marked in lower right corner of corresponding box. (A) Boxes containing (from right to left and bottom to top) the gneissic basement in the lower part of the photograph (box 53), followed upwards by massive polymict conglomerate (box 53), interbedded mud and sandstone (box 53 – 50), disrupted sandstone and mudstone (box 52 – 51) and thickly bedded sandstone (box 53 – 51) of the Mickwitzia Sandstone Member, it also contains massive sandstone (box 50 – 49) of the Lingulid Sandstone Member. (B) Boxes containing massive sandstone (box 48 – 44) of the Lingulid Sandstone Member, and a sandstone-pebble conglomerate (box 44) that is followed by black shale (box 44) of the Alum Shale Formation (uppermost part of photograph). 9

The part of the core used for this study is approximately 36 m long and includes Cambrian strata belonging to the File Haidar Formation and the basal Alum Shale Formation. Data from the core was collected and presented in a sediment log (chapter 3, Fig. 8 – 16), in which mineralogical and textural characteristics, as well as sedimentary structures, bed thickness and contacts were recorded. The reference-level of the stratigraphic log is based on the upper contact of the gneissic basement. Bioturbation was classified based on bioturbation index in Taylor and Goldring (1993); BI 0 indicate no bioturbation, BI 1 – 6 indicate sparse through moderate and intense bioturbation.

2.2. Localities In addition to core study, samples of the basal conglomerate of the Mickwitzia Sandstone Member were collected at Råbäcks hamn on the western shore of Kinnekulle. This unique outcrop hosts patches of the basal conglomerate (Fig. 6) preserved in fissures, pits and low areas of the underlying gneiss.

Figure 6. Photographs of the basal conglomerate in two different places at the locality Råbäcks hamn. (A) The conglomerate predominantly preserved within large fissures and joints. (B) The conglomerate preserved on a flat surface. Lens is 5 cm in diameter.

Another outcrop is located at Lugnås, where the ‘Lugnås millstone-mine’ (Fig. 7) provides a unique possibility to study the transition from the gneiss to the basal conglomerate and the lowermost part of the Mickwitzia Sandstone Member.

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Figure 7. Photographs showing weathered Precambrian basement, conglomerate and interbedded sandstone and mudstone of the Mickwitzia Sandstone Member. These constitute the walls and ceiling in the Lugnås mill-stone mine, located 20 km east of Kinnekulle. (A) Interference ripples and symmetric ripples in the lower parts of two different muddy beds, located approximately 2 m above the basement. The picture is taken at an angle from below, and the scale at the upper part of the photograph is approximately 2 m wide. (B) Weathered Precambrian basement in the lower part of the photograph, followed upward by conglomerate containing yellowish, thin and clayey horizons. The uppermost part is a sandstone bed. The vertical scale in the left side is approximately 2 m. (C) Irregular and symmetric ripples within interbedded sandstone and mudstone. The vertical scale is approximately 1 m. (D) A close-up of the photo in (C). The lens is 5 cm in diameter.

2.3. Petrography From the conglomerate that is directly overlying the gneiss at Råbäcks hamn, ca 20 samples were taken, from which 7 were made into petrographic thin sections. From the core,

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representative sections across all lithofacies were made into 24 petrographic thin sections. Thin sections were produced by Oliver Lehnert of Friedrich-Alexander-University of Erlangen- Nürnberg. Stratigraphic location of these thin sections from the core are shown in the stratigraphic log in chapter 3.1 (Fig. 8 - 16). From these thin sections, small-scale features such as replacements and cement, but also sorting, grain size and grain shape, were measured and determined visually in microscope. Specifically, grain size was compared to and described after the Udden Wentworth scale (Prothero and Schwab, 2004, p. 83). Grain shape was described after Powers (1953). Sorting was determined after visual estimation in comparison with standard schematic images (Prothero and Schwab, 2004, p. 5). 2.4. Terminology The terminology used here that relates to the depositional environment and bathymetry includes: Foreshore, which is equivalent to the intertidal zone. Upper shoreface, ranging from the lowermost tidal level down to the fair-weather wave base (FWWB). Lower shoreface, ranging from FWWB down to the storm-weather wave base (SWWB). Offshore is below the SWWB. The equivalence of other terminology commonly used to describe these units (e.g. Nielsen and Schovsbo, 2011) are: Shoreface (equivalent to foreshore and upper shoreface in this study), inner shelf (lower shoreface in this study) and outer shelf (offshore in this study).

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3. Results and interpretation 3.1. Stratigraphic log

Figure 8. Stratigraphic log of the Kinnekulle-1 drill core. It ranges from 0 – 4.0 m above the basement and contain core from box 53 and 52. The log starts from the surface of the gneissic basement and contain core from the Mickwitzia Sandstone Member.

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Figure 9. Stratigraphic log of the Kinnekulle-1 drill core. It ranges from 4.1 – 8.2 m above the basement and contain core from box 52 and 51. The log contain strata from the Mickwitzia Sandstone Member.

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Figure 10. Stratigraphic log of the Kinnekulle-1 drill core. It ranges from 8.3 – 12.4 m above the basement and contain core from box 51 and 50. The log contain strata from the Mickwitzia Sandstone and Lingulid Sandstone members, the contact is located at 9.4 m.

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Figure 11. Stratigraphic log of the Kinnekulle-1 drill core. It ranges from 12.5 – 16.6 m above the basement and contain core from box 50 and 49. The log contain strata from the Lingulid Sandstone Member.

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Figure 12. Stratigraphic log of the Kinnekulle-1 drill core. It ranges from 16.7 – 20.8 m above the basement and contain core from box 49, 48 and 47. The log contain strata from the Lingulid Sandstone Member.

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Figure 13. Stratigraphic log of the Kinnekulle-1 drill core. It ranges from 20.9 – 25.0 m above the basement and contain core from box 47 and 46. The log contain strata from the Lingulid Sandstone Member.

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Figure 14. Stratigraphic log of the Kinnekulle-1 drill core. It ranges from 25.1 – 29.2 m above the basement and contain core from box 46 and 45. The log contain strata from the Lingulid Sandstone Member.

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Figure 15. Stratigraphic log of the Kinnekulle-1 drill core. It ranges from 29.3 – 33.4 m above the basement and contain core from box 45 and 44. The log contain strata from the Lingulid Sandstone Member.

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Figure 16. Stratigraphic log of the Kinnekulle-1 drill core. It ranges from 33.5 – 36.0 m above the basement and contain core from box 44. The log contain strata from the Lingulid Sandstone Member up to 33.5 m and Alum Shale Formation from 33.9 and upward.

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Figure 17. Stratigraphic distribution of lithofacies 1 – 7 in the Kinnekulle-1 drill core, scale in meter. Four sections of the log are shown, going upward through the stratigraphy from bottom to top and left to right. Lithofacies 1 (red) is visible as a thin unit just above 0 m in the first section of the log. Lithofacies 2 and 3 (gray and brown respectively) occur throughout the first section of the log and in the lower part of the second section. Lithofacies 4 (green) can be seen in the middle part of the first section. Lithofacies 5 (bright yellow) can be seen throughout the second, third and fourth section. Lithofacies 6 and 7 (brown and dark gray respectively) can be seen in the upper part of the fourth section.

3.2. Gneissic basement The metamorphic basement rock that make up the bottom part of the core consist of gneiss of overall felsic lithology (Fig. 18A and 18C) and to a much lesser extent, mafic lithology (Fig. 18B). The felsic lithology is dominating, and makes up the contact between the gneiss and the overlying conglomerate. It has a medium-grained composition of quartz, biotite as well as heavily weathered feldspar. A mafic lithology (Fig. 18B) occurs within a short interval of 1 – 2 decimeters, approximately 1 m below the top of the gneiss. It is predominantly comprised of fine-grained biotite, plagioclase and amphibole.

The whitish color increase upward in the core. It can be seen in petrographic thin sections as weathered feldspar that is commonly replaced by very fine grained, patchy clusters of quartz and calcite. HNO3 of low concentrations produce a reaction with small gas-bubbles when 22

applied to the grains containing conspicuous calcite-replacement, confirming the presence of carbonate minerals. Light brown inclusions occur in the upper parts of the gneiss. These can also be seen in thin section as brownish, diffuse and amorphous replacement that in places occur with quartz and calcite. The top 10 cm is intensely weathered, and although weathering decreases down-core, it is still prominent down to approximately 40 cm below the top of the gneiss. From here it transitions from a smooth gray-white colour toward un-weathered gneiss at around 1.5 m.

Figure 18. Photographs showing varying degree of weathering within felsic lithology and mafic lithology of the Proterozoic gneissic basement (Eastern Segment) from the Kinnekulle-1 core. (A) Un- weathered felsic gneiss located approximately 2.3 m below the upper contact. (B) Moderate degree of weathering in mafic lithology within the gneiss, located approximately 0.9 m below the upper contact. (C) High degree of weathering in felsic gneiss. Contains and overall whitish character due to quartz- calcite replacements of feldspar, and orange-brown iron-rich inclusion. Located approximately 5 cm below the upper contact. Represents the lower part of KC-3 (Fig. 8).

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3.3. Sedimentary facies Lithofacies 1: Massive polymict conglomerate

Description Lithofacies 1 consists of poorly sorted, massive polymict conglomerate (Fig. 19 and 20) containing very fine sand to pebbles, with a generally fine to coarse-grained sand matrix. The conglomerate is located at the base of the Mickwitzia Sandstone Member. In the core, the conglomerate is approximately 8 cm thick. At the locality at Lugnås it is up to 1 meter thick. At Råbäcks hamn, only the most basal parts of the conglomerate are preserved in-situ, while stratigraphically unconstrained (detached from the in-situ preserved conglomerate) parts are found scattered around the locality.

The detached conglomerate samples show largely the same composition as conglomerate found in the core and the in-situ preserved conglomerate at Råbäcks hamn. The conglomerate in the field show a surface which is weathered and etched, features that give it a porous appearance in outcrops. The conglomerate is, however, well cemented internally. The conglomerate in the core has a lower contact that rests directly on top Figure 19. Photograph showing the of the heavily weathered Precambrian basement. The upper part of KC-3 (Fig. 8), displaying top part of the conglomerate is generally more fine- the contact between basement, con- glomerate (lithofacies 1) and inter- grained than the rest of the conglomerate. This upper bedded sandstone and mudstone part also show a fining upward that terminates in an (lithofacies 2) from the Kinnekulle-1 irregular ripple-like contact, which appear similar to the drill core. The gneissic basement can irregular surfaces of the sand units within lithofacies 2. be seen in the lower part where the feldspar shows a weathered and Field observation from Lugnås, and petrographic thin whitish character similar to Fig. 18C. Overlying this, separated by a sharp sections from samples taken at Råbäcks hamn, show contact, is 7 cm of conglomerate that large portions of the conglomerate consist of sub- containing, fine to granule sized, sub- angular to rounded, granule to pebble-sized clasts of angular to rounded grains of quartz primarily mono and polycrystalline quartz, euhedral and feldspar. In the upper-middle part of the photo, the upper conglomerate feldspar clasts and lithic fragments of mainly quartz and can be seen to be rippled and vaguely feldspar. The quartz clasts especially, show somewhat cross-laminated in the contact with the smooth or abraded surfaces. interbedded sandstone and mudstone.

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Figure 20. Photographs showing conglomerate samples that were collected as clasts that had been detached from the in-situ preserved conglomerate at Råbäcks hamn. (A) Conglomerate predominated by very coarse-grained sand. Contains a clast of sandstone in the lower right corner. (B) Pebbly, coarse- grained variety of the conglomerate showing a more clast-supported character and an abundance of pegmatitic clasts. Note euhedral feldspar in the top-center and a rounded quartz clast in the bottom- center. (C) Conglomerate containing an abundance of quartz-clasts as well as one finer-grained (left side) and one coarser-grained (right side) part. (D) Constituting a good example of a yellowish, sedimentary rock-clasts in the right-center. The clast is a mud-rich and micaceous, very-fine-grained sandstone. (E) Containing pebbles of quartz and feldspar supported by an abundant matrix. (F) Coarse- grained, clast-supported conglomerate with abundant quartz-pebbles. Note the upper, fine-grained, non-conglomeratic sand bed.

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The matrix is composed of fine to coarse-grained sand that primarily consists of sub-angular, sub-rounded or in places rounded quartz, as well as sparse grains of lithic fragments, feldspar and very little mica. The sand-sized fraction of the conglomerate can also be seen in overall better sorted portions (also described later, in relation to quartz cement). These are more quartz-rich parts that are overall moderately sorted, as opposed the poorly sorted textures which are also common in the conglomerate. Small portions are in places well sorted and contain overall finer grains. There are no distinguishable contacts, and these fine-grained portions appear to be related to the rest of the conglomerate. Another type of sand can be seen in Fig. 20D. This is significantly different from the rest of the sand-sized material in the conglomerate; it has a sharp contact to the poorly sorted conglomerate and consists of overall well sorted, sub-angular to rounded, very fine to fine-grained quartz-sandstone. Feldspar and mica occur sparsely and it also contains nearly plane parallel streaks that follow the outline of the conglomerate, these streaks consist of mica and diagenetic iron-minerals.

Outcrops containing conglomerate at Råbäcks hamn and Lugnås commonly include rounded clasts of sedimentary rock. Petrographic thin sections of samples from Råbäcks hamn show that these clasts of sedimentary rock are in places iron stained and commonly consist of quartz-cemented, fine-grained quartz with abundant mud and mica. The sandstone clasts are normally rounded or well-rounded and elongate or discoidal in shape. In places, the clasts show uneven or craggy surfaces that appear to incorporate surrounding material. Thin section show that some of the sandstone clasts are commonly deformed in the outer edges; surrounding grains appear to be penetrating the sandstone grains, in which the mica change orientation to align with the outline of the penetrating grain.

Petrographic thin sections show that the conglomerate is either calcite or quartz cemented. Calcite is most abundant in samples of the conglomerate that rests directly on top of the basement. The conglomerate of the core is dominated by calcite cement but also contains relatively small areas of quartz-cement. The conglomerate here is very thin, and thus also represents the upper contact. In addition to calcite as cement, it is evident that much of the weathered feldspar is replaced by same type calcite. Many clasts are completely replaced and can only be distinguished as feldspar or plagioclase by the remnant outline and the polysynthetic- or tartan twinning. Some clasts within the conglomerate appear to be floating in a calcite matrix. In most places, the calcite cement is indistinguishable from the calcite replacement.

The stratigraphically unconstrained samples from Råbäcks hamn display calcite cement but are in places entirely cemented or partly cemented with quartz, this appear to occur in overall better sorted and quartz-rich portions of the conglomerate. The quartz cemented portions of the conglomerate are commonly more poor in feldspar, and the feldspar that exist show no quartz-calcite replacement and appear less weathered in comparison to feldspar in the calcite cemented parts. Within the quartz-cemented parts, calcite occurs but only as small inclusions. Iron staining is found to make up the cement to a lesser degree but is commonly restricted to small inclusion or clusters, much like the inclusions of calcite. The main difference between

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calcite and quartz cemented parts is that quartz commonly make up grain boundaries while the calcite is found in large pores or as matrix.

One pebble-sized lithic fragment and similar smaller clasts are composed of predominantly quartz, feldspar and plagioclase, as well as mica to a lesser degree. These are compositionally and texturally much like the gneissic basement and occur sparsely in the conglomerate. These are in places even more weathered than the gneissic basement and sometimes nearly devoid of feldspar. Patchy clusters of quartz-calcite replacement occur predominantly within in the feldspar; it is present both within lithic fragment and individual feldspar grains. This commonly occur together with inclusions of iron staining similar to that found in the underlying gneiss. The most common case is that quartz-calcite replacement can be seen where the feldspar itself is entirely replaced by calcite, or to some extent, where the grain-boundary outline or original feldspar grain partly remains. In these places, the quartz-calcite replacements appear to remain largely unchanged and can be distinguished by its patchy, fine-grained character.

One sample from the contact with underlying gneiss contain a very thin (<2 mm) sub- horizontal crack, which is filled with very fine quartz sand. In one sample (Fig. 20F), similar, well-sorted, fine-grained sand is found in the contact with the conglomerate.

Interpretation The mineralogical composition, maturity and great difference in grain and clast size together with shape of clasts in the conglomerate, can be interpreted as containing sediment from different types of sources. Sub-angular and rounded clasts can be interpreted as resulting varying degree of transport or reworking, and the smooth surfaces may indicate abrasion in an eolian environment (Prothero and Schwab, 2004).

The composition of pebble-sized, polycrystalline, euhedral crystals of feldspar, quarts and lithic fragments (containing largely quartz and feldspar) can be interpreted as pegmatite clasts. These must have originated from a very coarse-grained magmatic source rock such as pegmatite veins. It is unlikely that they were derived from the directly underlying, overall medium-grained gneiss. The grain size and angularity seen in several of these large pegmatitic clasts suggest short transport indicating that they are locally derived. The variation in rounding, size and shape of clasts may also indicate that inherited crystal shapes and sizes played a role in rounding, or that some clasts have been more reworked than others. It is possible that sub-sequent reworking or redistribution may give rise to some variation in shape. However, it appears most likely that the rounding of the clasts occurred during transport. Fluvial processes are one possibility for transporting clasts with large grain size, indicating that associated currents in that case were probably relatively strong.

Many of the pegmatitic clasts show smooth surfaces, these could be interpreted as eolian abrasion. Ventifacts are commonly associated with eolian environments in which abrasion can produce angular shapes by faceting (Prothero and Schwab, 2004). No clear evidence of ventifact are found within any of the conglomerate samples. However, some of the quartz- pebbles show a conspicuous angularity that could be due to faceting.

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Another possible indication of eolian activity is the fine-grained fraction of sand within the conglomerate and the occurrence of rounded fine-grained quartz. Much of the fine-grained sand in the conglomerate is overall moderately sorted at best, and occur only in small portions. This may be due to contemporaneous or later reworking. However, well sorted, fine- grained, quartz sandstone occur, which can be seen in Fig. 20F; this does not appear to be associated with any reworking of the conglomerate, as is the case at the contact to the overlying marine deposits. It is possible that this may be a remnant from a previous environment. It is difficult to determine the manner of deposition from such a small, incomplete sand bed, but the lack of any type of current or wave structures indicate that it is clearly different from the marine deposits that make up the upper contact top of the conglomerate.

Sandstone clasts occurring within the conglomerate are compositionally and texturally different from the conglomerate. These are interpreted as extra-formational clasts derived from sedimentary rocks exposed in this area during the early Cambrian. The overall muddy and fine-grained textures may represent aqueous deposition. The broken, uneven edges, grains that penetrate the clasts, and deformed mica, are interpreted as a lesser competence of the sandstone clasts together with pressure associated with burial.

Medium-grained or pebble-sized, non-pegmatitic lithic fragments in the conglomerate show similar composition as the underlying basement. The lithic fragments in places contain distinct quartz-calcite cement, and to a lesser degree, iron cement replacement that is also found in many of the individual feldspar grains that occur in both the conglomerate and the basement. Based on these similarities in lithology and the composition of the replacements, the lithic fragments and feldspar grains are interpreted as derived from the underlying, weathered gneissic basement. Many of the lithic fragments have been entirely or partly replaced by matrix-forming calcite, suggesting that the quartz-calcite replacements were precipitated first.

The compositional and textural difference, such as the significantly less feldspar and better sorting in places with quartz cement than in calcite-cemented parts, together with inclusions of calcite cement occurring inside the quartz-cemented parts; these features suggest that the quartz cement was precipitated before the matrix-forming calcite cement. It is possible that much of the conglomerate was originally quartz-cemented, but also compositionally zoned; much of the feldspar may have been later replaced with calcite, resulting in quartz-rich areas remaining relatively unchanged. Another possibility is that partly or entirely quartz-cement portions existed at some point, but were reworked and redistributed within the conglomerate. The ripple structures in the upper part of the conglomerate support an interpretation that the conglomerate was reworked, likely by marine processes. This is also supported by the fact that material from the conglomerate is incorporated in the lower parts of the directly overlying lithofacies 2. Another feature is the size and orientation of the ripples, which in conglomerate, are much like the ripple in lithofacies 2, suggesting that the processes that deposited lithofacies 2 likely also reworked the upper part of the conglomerate.

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Lithofacies 2: Interbedded sandstone and mudstone

Description Lithofacies 2 consists of interbedded sandstone and mudstone that are characterized by cross- laminated, or normally graded, very well sorted, fine to medium-grained sandstone interbedded with dark or greenish mudstone (Fig. 21). These beds belong to the Mickwitzia Sandstone Member and are primarily located between 0.1 – 6.3 m in the core, and to a lesser extent up to 9.4 m (Fig. 8 – 10 and 17).

In the interbedded sandstone and mudstone, the sandstone make up the lower part, and the mudstone make up the upper part. Each composite set of sandstone and mudstone are together normally 2 – 7 cm thick and typically occur stacked in several sets. The lower sandstone part is commonly bright or iron-stained. Individual sandstone units are commonly 1 – 5 cm thick and show fining upward of fine to very fine-grained quartz. The sandstone beds include small-scale cross-lamination, irregular bedding or dipping surfaces as well as load casts, groove casts and tool marks that cut into underlying mud. In the drill core, cross- lamination within the sandstone consists of both upward-concave and downward-concave, curved lamination, in places with truncated tops which are overlain by mudstone or, in places, another sandstone unit. Normally, the sandstone beds gradually transition overlying mudstone units.

The composition of the sandstone units is dominated by largely prismoidal, rounded to well- rounded quartz grains as well as minor parts mica. Feldspar grains and sedimentary rock-clasts exist but are rare. The sedimentary rock-clasts are commonly muddy sandstones. However, these can be difficult to distinguish from intra-formational rip-up clasts of muddy sandstone, which are relatively common. Iron staining and quartz can be seen in thin section to predominate the cement within the sandstone beds.

Almost all the sandstone beds are fine grained, but coarse-grained sandstone occurs at around 6.0 m (Fig. 9), and granule-sized sandstone at 9.1 m (Fig. 10). At 9.1 m, there are three coarse- grained beds consisting of coarse sand to granule which contain sub-rounded quartz, sub- angular euhedral feldspar grains and a small fraction of lithic fragments and clasts of extra- formational sedimentary rock. The beds with coarse sand to granule range from 1 – 3 cm in thickness and are capped by mudstone. The granule-sized beds show no apparent internal structure, but have distinct erosional lower contacts.

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Figure 21. Photographs showing composite sets of interbedded sandstone and mudstone (lithofacies 2) of the Mickwitzia Sandstone Member in the Kinnekulle-1 drill core. (A) Normally graded, cross- laminated and in places truncated beds of undulating or irregular sandstone and mudstone. Containing relatively low bioturbation (BI 1) occurring within mud layers. Red-brown iron staining can be seen within the lower fine-grained sandstone of each set, the iron-stained sandstone is commonly overlain by bright, silty and micaceous sand and dark mud. Represents KC-5 (Fig. 8). (B) Overall thicker beds of sandstone and mudstone and a lack of bioturbation except for the uppermost part of the photo. An intra-clast characterized by darker shade can be seen in the middle of the photo. Represents KC-6 (Fig. 8). (C), (D) Represent the lower and upper part respectively, of a bed containing moderate to thorough bioturbation (BI 3 – 4) within lithofacies 2. Located in the upper Mickwitzia Sandstone Member. (C), (D) represents the lower and upper part respectively of KC-11 (Fig. 9). The mudstone that make up the upper part of the composite beds of interbedded sandstone and mudstone are commonly <1 – 3 cm thick. The mudstone beds commonly consist of large amounts of un-deformed mica and mud, and to a lesser extent very fine-grained quartz. The mudstone also contains variable amounts of calcite interspersed within the mud. The mudstone also takes on a greenish tint, which is more prominent at around 2.5 m. The mudstone beds show a fining upwards that appear as normal grading, the grading is characterized by a change from very fine sand, to mica and mud. In places where mudstone drapes sandstone with irregular surfaces and truncated lamination, the mudstones are normally associated with a thin very-fine sand-rich layer at the base. They are prominently cross-laminated and normally graded, and consist of mud in the upper part, as well as fine- grained and silty sands at the interface between the sand and mud. The cross lamination is most prominent in the lower part, in the contact to the sandstone beds. The cross-lamination in the sandy part of the mudstone is recognized as curved laminations largely similar to those observed in the sandstone. One difference is that the lamination in the sandy part of the

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mudstone appear to be more horizontally continuous and overall less truncated. The cross- lamination in the sandy part of the mudstone commonly appears as an extension of the cross- lamination within the sandstone. Such similarities are also apparent in the seemingly random, gentle dip that is exhibited by many of the sandstone and mudstones.

In places where mudstone caps exist, the sandstone at the base is in places less bioturbated than the upper mudstone. The bioturbation index within lithofacies 2 generally ranges from 1 – 3. There is no trend that can be distinguished, but it is evident that two sections of significantly more bioturbated (BI 3 – 4) lithofacies 2 occur in the upper part of the Mickwitzia Sandstone Member.

In each composite set of sandstone and mudstone, the lower contacts of these sets are in places characterized by loading, and more rarely, scoured contacts. The loading and the scoured contacts occur especially in the thicker sands. The amount of mudstone in each set varies, and it is sometimes omitted entirely, in places this can be seen as erosional amalgamation of two sandstone beds. The sandstone beds regularly have a gradual transition into overlying mudstone caps that are in places bioturbated.

The locality at Lugnås displays largely similar interbedded sandstone and mudstone. These indicate that the irregular surfaces of sandstone and mudstones containing cross-lamination, belong to symmetric ripples and interference ripples, or to a lesser extent, vaguely undulating thicker beds of sand (Fig. 7A, 7C and 7D). In the core, the occurrence of these interbedded sandstone and mudstone layers can be seen to decrease upward in frequency (Fig. 17).

Interpretation Marine sediment with interbedded sand and mud are known by several different descriptive and genetic terms such as flaser, wavy or lenticular bedding, as well as rythmites, tempestites, turbidites and contourites. Such beds can occur in significantly different depositional environments in terms of process and water depth but share that they were deposited under fluctuating energy conditions (Prothero and Schwab, 2004). Such conditions are commonly found in marine environments during the influence of mass movements, bottom currents, tides or storms. What follows is a discussion of this wide range of depositional environments and an evaluation of which environments best explain lithofacies 2.

Marine mass-movement deposition from turbidites commonly results in partial to complete Bouma sequences (A through E), where the Bouma sequences represent the idealized vertical succession of turbidites (Leeder, 1999). When comparing the interbedded sandstone and mudstone found in lithofacies 2, to the turbidite model by Bouma (1962, as cited in Prothero and Schwab, 2004), it is clear it does contain some of the characteristics found in the Bouma sequences: These characteristics include basal tool marks, graded bedding (division A of the Bouma sequence) and to some extent the laminated and homogenous mud (division D and E respectively). Although complete Bouma-sequences are rare (Prothero and Schwab, 2004), many of the important diagnostic features representing turbidity currents are not present at all. These include Bouma sequence division B and C, which should include several current- 31

induced structures such as plane-parallel lamination, tabular cross-lamination and climbing ripples.

Facies with interbedded sand and mud can also be produced by contourites. These are deep- sea sediment that commonly display intercalated sand and mud associate with bottom currents (Rebesco et al., 2014). These are described by Rebesco et al. (2014) as “rather poorly sorted, mud-rich (between 5 and 40 μm) facies, which is intensively bioturbated, intercalated by thinner horizons of fine-grained sands and silt, and typically shows a somewhat rhythmic bedding”. Deposition of contourites normally take place by unidirectional traction flow and suspension-settling of fines, although sand-rich contourites occur, these are less common and may be related to reworking of sandy turbidites (Rebesco et al., 2014, and references therein). Sediment structures within contourites can be largely similar to tidal sediments and turbidites, however, suggested diagnostic features include reverse grading, longitudinal triangular ripples, double mud layers and sigmoidal crossbedding (Rebesco et al., 2014).

While turbidites and contourites can be considered quite unlikely in a flat, craton interior setting, this interpretation can also be excluded by considering sedimentary structures. The interbedded sandstone and mudstone of lithofacies 2 exhibit only few or none of the sedimentary structures considered diagnostic for turbidites and contourite. Further, lithofacies 2 shows overall very little influence by unidirectional, sustained currents, which suggest they did not originated in an altogether current-dominated environment as such responsible for producing contourite-deposits.

Interbedded sand and mud are also produced on tidal flats. Such environments are characterized by deposition of sand during alternating tidal currents and suspension-settling of fines in between (Leeder, 1999). Typical tidal sequences (Klein, 1972, as cited in Walker, 1984) show fining upward with entirely sand or mud dominated lower and upper parts respectively, while flaser, wavy or lenticular bedding are present in the mid parts of the sequence. In the mid part of such typical sequences, ripple-lamination commonly record bi- directional flow paths, and re-activation surfaces are common (Prothero and Schwab, 2004). In lithofacies 2, there is little evidence of sedimentary structures that would suggest alternating currents. Although, the rhythmic intercalations of sand and mud together with tool marks are an indicating of fluctuating energy and flow respectively (Leeder, 1999; Prothero and Schwab, 2004). Lithofacies 2 also contain centimeter-scale curved, cross-lamination that drape irregular surfaces, these can be interpreted as a type of small-scale hummocky cross stratification (HCS). Such sedimentary structures have been reported from, but are not indicative of tidal environments (Campbell and Oaks, 1973, as cited in Dott and Bourgeois, 1982). Bioturbation is common in mudstones deposited on the upper part of tidal flats where flow conditions are relatively weak, however, these parts of the tidal flat are regularly exposed to subaerial exposure, giving rise to features such as algal mats and mud cracks (Prothero and Schwab, 2004). No such subaerial features have been found in lithofacies 2. The most abundant ripple-types can be attributed to oscillation ripples, suggesting that wave action played much more important role. The current-induced ripple-forms are sparse, suggesting

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that unidirectional currents played a sub-ordinate role in deposition of lithofacies 2. The occurrence of interference ripples could indicate a tidal environment and may represent asymmetrical currents (Prothero and Schwab, 2004). However, the sparsity of current-induced structures and that the interference ripples are largely over and underlain by wave ripples, suggests that the interference pattern may instead be associate with the interference of waves, or current and waves. Finally, although several sedimentary structures exist that can be produced in tidal environment, the absence of structures reflecting alternating currents or an overall current-influence make it less likely that lithofacies 2 originated in a tidal-flat environment.

The morphology of the sandstone beds in the core is such that differentiation between wave ripples and what has been called ‘small-scale hummocky cross bedding’ (Dott and Bourgeois, 1982) is difficult. The irregular surfaces seen in the sandstone beds present in lithofacies 2 may be attributed ripple forms or small-scale hummocky forms. What these forms look like in three dimensions is difficult to determine within the core. The locality at Lugnås indicate that the irregular surfaces seen within the core is likely interference ripples or possibly symmetrical oscillation ripples. The thicker beds containing vaguely undulating surfaces are likely represented as low-angle dipping surfaces within the core.

In lithofacies 2, the irregular beds of sand are on a scale of centimeters. These may, however, be either a type of small-scale HCS, oscillation or interference ripples. It is possible that these represent deposition in an environment alternating between wave-induced, oscillatory movements and rather weak combined flow. Combined flows are associated with storm generated unidirectional flows and oscillation during storm-wave action, in fine sands and silt these are responsible for producing meter-scale HCS that develop by traction and suspension- fallout during wave-oscillation (Walker, 1984; Duke et al., 1991; Dott and Bourgeois, 1982). During the waning of the storm, wave ripples are produced, these are commonly associated with moderate wave-action (Brenchley, 1989).

Sediment deposited or reworked by storms are conventionally referred to as tempestites. Indicative for tempestites are the specific combined-flow conditions resulting in HCS, as well as the interbedding of fine-grained or conglomeratic sandstones and bioturbated mudstones (Walker, 1984; Brenchley, 1989). Sedimentary structures occurring in tempestites were presented in an idealized sequence by Brenchley (1989), the structures were divided into B, P, H, F, X and M, and represent the change in structures as deposition gradually went from taking place during the peak of the storm (i.e. division P or H) to fair-weather sedimentation (i.e. division M). Generally, the sandstone beds can be attributed to moderate wave-action during the waning of the storm, division ‘F’ in Brenchley (1989). The mudstone beds can be attributed to fair-weather sedimentation, division ‘M’ in Brenchley (1989). However, the absence of any of the divisions representing the peak of the storm event (i.e. B, P, H and F), suggest that the moderate wave-action seen in sandstone bed (attributed to division X) may represent a distal setting or deeper water rather than the waning-stage of storm action.

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The character of the sedimentary structures and general lithology of the interbedded sandstone and mudstone are also well consistent with the tempestite facies described in Dott and Bourgeois (1982), as well as tempestite trends described by Aigner and Reineck (1982) as cited in Leeder (1999). These facies associations suggest that lithofacies 2 represents deposition on the lower shoreface, below FWWB and above SWWB. The associations also suggest that HCS and oscillation ripples, together, as well as small-scale or ‘micro’-HCS, like the ones present in the lithofacies 2, may be indicative of the mid or distal tempestite facies. Additionally, small-scale HCS may be associated with waves acting in conditions where sand supply is too ‘starved’ to produce oscillation ripples, which instead produce very small hummocky lamina (Dott and Bourgeois, 1982).

Lithofacies 3: Thickly bedded sandstone

Description Lithofacies 3 is characterized by fine to coarse-grained, very well to well sorted, massive or cross-laminated sandstone beds (Fig. 22). These are in places capped by very thin homogenous or normal graded mudstone. These beds occur throughout the Mickwitzia Sandstone Member. They are generally interbedded with lithofacies 2. The thickly bedded sandstones increase upward in thickness and frequency (Fig. 17).

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Figure 22. Photographs showing quartz-cemented, iron-cemented and calcite-cemented fine to medium-grained quartz within thickly bedded sandstone (lithofacies 3) of the Mickwitzia Sandstone Member within the Kinnekulle-1 drill core. (A) Relatively thin example of overall fine-grained sandstone, the lowermost occurrence of lithofacies 3. Contains gently dipping cross-lamination and orange-brown iron-staining. Represents KC-4 (Fig. 7). (B) Gently dipping cross-lamination within fine- grained, iron-stained sandstone. Horizon of slightly coarser grains can be seen in the middle of the photo. Represent KC-7 (Fig. 8). (C), (D), (E), (F) Thickly bedded sandstone of the upper part of the Mickwitzia Sandstone Member. Fine to medium grained, but overall coarser and more porous than lower occurrences of lithofacies 3. Cross-lamination can vaguely be seen within the upper part of (C) and vaguely dipping horizons occur within (F) that can be distinguished as part of a cross-laminated section within the core. Represents KC-10 (C), KC-12 (D), lower (E) and upper (F) part of KC-13 (Fig. 9 and 10).

The beds consist of relatively thick (overall 10 – 30 cm, sometimes thicker) sandstone that are in places iron stained. The beds are in places massive, or show gently dipping cross lamination, or cross-lamination of oscillation-type ripples. The beds also contain truncated, in places

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amalgamated cross-lamination as well as less common plane parallel or slightly dipping lamination. The sandstone beds are fine to coarse grained and texturally different between individual beds; some are well sorted like the sandstone in lithofacies 2, while some are more poorly sorted with larger quartz clasts at the base indicating that they are normally graded. Many beds display a coarse-grained base and normally have erosional lower contact. The textural and compositional difference can in places be seen coarser and porous beds, which contain calcite inclusion in the shape of grains. The calcite inclusions appear as remnants within cavities or as whitish ‘grains’. Overall, these beds are predominantly quartz-cemented, but calcite cement exist in places, and is especially common within in the coarse-grained porous beds.

Interpretation Based on the general absence of current-induced sedimentary structures and presence of oscillation ripples, the sandstone units in the interbedded sandstone and mudstone (lithofacies 2) were interpreted as deposited and reworked by storm waves. The thick sandstone beds of lithofacies 3 (this lithofacies) display similar sedimentary structures, general characteristics (sandstone capped by mudstone) close interbedding with lithofacies 2, which suggest largely similar depositional processes.

The thickly bedded sandstone of this lithofacies show an upper contact that is in places irregular or slightly dipping, which may represent a hummocky topography. Sandy lithology and in places truncated and amalgamated cross-lamination with erosive, coarse-grained and ‘conglomeratic’ lower contacts; are features common in HSC (Dott and Bourgeois, 1982). However, because HSC is commonly occurring on meter-scale and these are on a decimeter- scale, and because the three-dimensional relationships of beds cannot be determined in a drill core; the interpretation that these are HSC beds is very uncertain, and should be done with caution.

The increasingly sandy lithology, overall coarse-grained texture together with the better developed cross-lamination; the thickly bedded sandstone can be interpreted as deposited by storms in an environment dominated by either, an abundance of sand, shallower depth, more frequent storms, larger waves or a more proximal setting (cf. Dott and Bourgeois, 1982). Further, the much thinner and sparser mudstone beds can be interpreted as calm conditions that favored deposition of fine material, occurred less frequently. The amalgamated HCS beds can be interpreted as storm-reworking and deposition that either occurred without an intermediate period of mud-deposition, or that any mud that had been deposited was scoured away by the following storm event (Dott and Bourgeois, 1982).

The compositionally different sandstone bed located between 8.5 – 8.8 m likely represents a source different from the other sandstone beds. The whitish inclusions or remnants of whitish material that fill pore spaces consists of calcite. It appears unlikely that one bed should experience deposition of calcite grains in an otherwise mud or sand dominated environment. It appears more likely that calcite replaced whatever constituted the pore spaces within this

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bed. One possible explanation is that this bed had a more arkosic composition at the time of deposition; calcite may have completely replaced the feldspar as is the case in lithofacies 1. Moreover, Dott (2003) and reference therein, suggests that diagenesis can produce ‘skeletal grains’ and that cavities associated with them are indicative chemical weathering.

The great similarity suggests that the genesis of lithofacies 3 is essentially the same as lithofacies 2. However, the predominance of sand, erosive contacts and better developed cross-lamination suggest that it is possible that there were more sand or less mud in the system, but likely that the energy condition during storm events were frequently higher, which would result in poor preservation potential for mud deposited during fair-weather conditions.

Lithofacies 4: Disrupted sandstone and mudstone

Description Lithofacies 4 consist of disrupted sandstone and mudstone bedding. It occurs approximately between 3.8 – 5.7 m (Fig. 8 – 9) within the Mickwitzia Sandstone Member. The original, non- disrupted sandstone and mudstone bedding is preserved in places, these partially preserved beds appear to be largely similar to lithofacies 2 and 3. What follows are descriptions of the four distinct features that characterizes lithofacies 4.

The first feature is homogenized zones, consisting of poorly consolidated, disordered bedding of ‘speckled’ iron-stained, fine to medium-grained sandstone and green mudstone. Homogenized zones occur sporadically, and to a varying degree throughout lithofacies 4. One section that is approximately 30 cm thick, stands out due to the well-defined upper and lower contacts, complete homogenization, and absence of other structures. Similar sections normally have no distinguishable upper and lower contacts; the thickness of these sections are usually 10 – 30 cm.

The second feature is horizontally discontinuous beds of remnant original bedding. These exists as small (approximately 3 – 7 cm in thickness) isolated and discontinuous beds that consist of massive, in places iron-stained sandstone, or laminated greenish mudstone and sandstone. The remnant bedding show little or no trace of bioturbation and are in places bounded above and below by ‘homogenized’ zones as described above, or separated from each other by vertical sand and mud filled cavities which are described below.

The third feature is isolated mudstone that occur in addition to discrete beds in lithofacies 4. These can be viewed as either be ‘pockets’, ‘balls’ or ‘clasts’ of mudstone. The first, dominating type of mudstone ‘clasts’, occur within massive sandstone. The clasts are characterized by horizontally elongate mudstone approximately 1 – 5 cm in diameter. The mudstone ‘clasts’ show no lamination and appear to be only vaguely laterally continuous where several occur in a cluster. The rounding or elongation of the ‘clasts’ appear to be accompanied by irregularities within the bedding of the laterally and vertically surrounding sandstone. Such irregularities occur approximately between 4.1 – 4.3 m. Here, the individual mudstone beds also appear to have been deformed or ‘squeezed’ from above and below by interbedded sandstone. The

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second type of mudstone ‘clasts’ consist of single, more spherical mudstone balls or mud-filled pockets which may also be seen as another perspective of the ‘cavities’ described below. Around these spherical mudstones, or filled holes, are medium-grained sandstone which is also sometimes incorporated inside the mudstone balls. The surrounding sandstone is mainly well cemented and cross-laminated and have minor parts which are more massive and poorly consolidated.

The fourth feature is vertical cavities filled with sandstone and mudstone. These features may be seen either as vertical tubes or filled holes that cross-cut the primary bedding described above. The vertical tubes are 10 – 15 cm long and filled by a mix constituting green mudstone together with iron-stained, medium- grained sandstone. The filling in these structures are either porous or loosely consolidated within mud, similar to the homogenized zone described above. There are no clearly distinguishable contacts marking the portion of the core that contain these ‘tubes’. The entire section (at approximately 5.6 m) span approximately 50 centimeters and contain multiple vertical tubes which are directly or vaguely connected. The horizontal holes that penetrate through the core (described above) may be another perspective of these ‘tubes’ or ‘holes’. The horizontal holes are filled by the same greenish mud that fills the vertical tubes. The horizontal holes could also be seen as similar to the

Figure 23. Photographs showing examples of some of the features in the disrupted sandstone and mudstone (lithofacies 4) of the Mickwitzia Sandstone Member within the Kinnekulle-1 drill core. (A) Partly obscured vertical tube showing a sharp contact with remnant bedding of cross- laminated, fine-grained sandstone (right side) and an iron- stained, mudstone and sand-filled vertical tube showing a more irregular or ‘soft’ contact where it disrupts the primary bedding (left side). Represents KC-9 (Fig. 9). (B) Orange- brown iron-stained sandstone and mudstone with tube-like structures and small-scale homogenization. Represents KC-8 (Fig. 9).

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mudstone ‘clasts’ described above, but main difference is that the horizontal holes do not occur in clusters, but rather as isolated ‘holes’. Another difference is that the horizontal ‘holes’ have a more spherical shape, and that they have iron-stained contacts with the sandstone they occur within. Moreover, the mudstone ‘clasts’ consists predominantly of mud, while the horizontal ‘holes’ commonly constitute a mix of sand and mud.

Interpretation In general, features and structures like the disturbed and homogenized bedding as well as the tube-like scours or cavity-fills that occur in lithofacies 4, could have been formed either during deposition or as a diagenetic effect. Additionally, in-situ deformation in unconsolidated sediment can be associated with purely physical or biological processes. Because parts of the primary bedding are preserved, this suggests that deformation and disruption occurred after rather than as a direct depositional feature.

Sedimentary structures that are made by, or associated with bioturbation, can be difficult to distinguish from other types of soft-sediment deformation. Conical or plug-shaped deformation are examples of such structures that can be attributed to both organic and inorganic processes (Buck and Goldring, 2003). Buck and Goldring (2003) showed in lab experiments, that dragging an object through laminated sediment could produce features such as cone-shaped collapse structures, narrow shafts and homogenized bedding (in the core of the deformed zone) as well as mudstone balls or dish-structures, which they were also able to also identify in the field. Although such structures exist throughout the facies 4, the greatest similarity is to the homogenized bedding, the vertical pipe or shaft like structures as well as, to a lesser extent, ball or dish-like mudstones. There is, however, no evidence that suggest that any of these structures are related to each other in the form of a burrow. There is little or no change in the small-scale bioturbation, which characterizes the ichnofabric of the isolated parts of preserved primary bedding in lithofacies 4, as well as over and underlying sediment (lithofacies 2 and 3).

Buck and Goldring (2003) also compared bioturbation-induced structures to fluidized, dewatering and water-escape structures. They found that conical structures associated with dewatering are commonly identified by homogenized or otherwise deformed sediment at the base. This may be the case in lithofacies 4, where the vertical ‘cavity-fill’ or pipe-structures occur above homogenized bedding. Although there is no evidence that suggest a direct connection, the limited lateral view of the drill core makes this difficult to distinguish.

Soft-sediment deformation structures (SSDS), like dewatering and water-escape structures can form as either primary structures during rapid deposition or as secondary, post- depositional structures during shallow burial (Prothero and Schwab, 2004). According to Põldsaar and Ainsaar (2014) and references therein, examples of such post-depositional structures include load casts, flame structures, ball-and-pillow structures as well as breccia or sedimentary dykes. These can occur in shallow marine environments where water-saturated sediment is affected by changes in hydrostatic pressure. The driving mechanism for this kind

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of SSDS is fluidization and liquefaction, in which the sediment behaves as a liquid when it loses shear resistance and granular strength.

Many of the structures that occur in lithofacies 4 are similar to liquefaction-triggered SSDS, such as those described in Põldsaar and Ainsaar (2014). Four of these features and their possible equivalents in lithofacies 4 respectively, include: 1) Homogenized or partly homogenized zones resulting from particle movements during complete liquefaction, they are comparable to the homogenized zones in lithofacies 4. 2) Bedding preserved as un-deformed brecciated parts within the homogenized zones, this could possibly explain preservation of original bedding in lithofacies 4. 3) Ball-like pseudo-nodules are comparable to the mudstone balls in lithofacies 4. They are somewhat different, which may be due to the different lithology. It is still possible that the mudstone balls and the ‘pseudo-nodules’ formed due to the same processes of upward displacement of underlying sediment caused by liquefaction, and downward displacement of overlying sediment caused by loading and dewatering. The sandstone that is in between the mudstone balls show similarities to loading features. If such loading occurred, it also appears to have given the mudstone balls a ‘smooth’ and rounded character in contact to the sand. Another effect of loading may also be the curved shaped of the mudstone balls, which are either convex-upward or convex-downward. These could be interpreted as upward or downward movement of fluid and sediment surrounding the mudstone balls. The mudstone balls are overall similar to the over and underlying, less deformed mudstone layers, which suggest that they are likely in-situ deformed mud-layers. 4) Sedimentary dykes caused by fluidization of underlying sediment which is then injected upward. Such injections are believed to be able to produce deformation within unconsolidated sediment that are appear much similar to brittle deformation. These features are comparable to the vertical sand and mud-filled cavities in lithofacies 4.

It is possible that the sediment was lithified at the time structures formed. Processes occurring in lithified rock which could be responsible for producing structures within an isolated section like in lithofacies 4, could be related to dissolution. In siliciclastic rocks, dissolution occurs preferentially in cracks, joints and grain boundaries; grain boundaries widen through dissolution of cement as well as corrosion and etching of the quartz grains (Wray, 2003, and references therein). Shade et al. (2015) note that, although dissolution is not commonly associated with siliciclastic rocks, it can form both in quartz arenites and orthoquartzites as well as on all continents and in a wide climate range.

The reviews of Wray (2003) and Shade et al. (2015), and references therein, discuss the processes, structures and landforms of siliciclastic dissolution features. Based on these reviews, it is perhaps only the vertical sand and mud-filled cavities in lithofacies 4 that could be explained as a feature formed by dissolution. This could be indicated by ‘collapse’ or ‘removal’ of grains derived from the sides as well as over and underlying layers, which is occurring during dissolution under near-surface conditions. Features produced on sub-aerially exposed surfaces can include networks of lamellar porosity, formed by flowing water and dissolution-controlled separation of individual grains. There are, however, no evidence in the

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core that suggest any such subaerial exposure at the top of lithofacies 4. Dissolution can occur in deep buried sandstones as well, although examples of such evidence are largely microscopic features of silica solution. The magmatic intrusion approximately 250 meter above consist of diabase, and it should be noted that, hydrothermal fluids have been suggested as a possible dissolution agent in examples from quartzite in Venezuela. However, in this example, the hydrothermal fluids were believed to have been very aggressive and originated from a granitic magma. Additionally, the role of these hydrothermal fluids is suggested to have been mainly agents for opening flow-paths that were further eroded during subsequent weathering.

Overall, the vertical sand and mud-filled tubes are distinctly different from examples of lamellar networks, and the associated homogenized zones and mudstone ‘clasts’ in lithofacies 4 fit poorly the concept of dissolution-features.

Lithofacies 5: Massive sandstone

Description Lithofacies 5 consist of very well sorted, overall massive sandstone (Fig. 24). It occurs approximately between 9.4 – 33.5 m, and span the entire Lingulid Sandstone Member. Lithofacies 5 is largely composed of bright, very fine to fine-grained sandstone that is normally homogenous, with a massive or thinly laminated appearance. Lithofacies 5 is largely similar throughout its extent, with the exceptions of sparsely occurring cross-lamination, sections rich in pyrite, and an abundance of interspersed, thinly laminated fines that predominates in the middle of the Lingulid Sandstone Member, approximately between 19 – 25 m.

The sandstone in lithofacies 5 is mainly made up of well cemented and consolidated quartz sand with minor parts of white mica. The quartz grains are mostly spherical or prismoidal and largely rounded to well-rounded. The cement consists primarily of quartz and to a lesser degree, calcite. Traces of bioturbation are most evident in the abundant thinly laminated fines that in places makes up very thin (1 – 2 mm) lamination. This finely laminated material is predominantly made up of silt-sized mica and mud.

The portions where mudstone lamina is sparse generally occur at the bottom and the top of the Lingulid Sandstone Member. Due to less bioturbation in these parts, the interspersed fines are better described as thin (1 – 2 mm) lamination that drape underlying surfaces. These surfaces are either horizontal, gently dipping or vaguely undulating. The thin, muddy lamination commonly make up bundles of 2 – 5 layers that have a spacing of a couple of centimeters between each lamina. Sections with similar variation in the frequency of bundles are generally around 20 – 30 cm thick. Where these laminations are abundant, the bioturbation is commonly moderate to high (normally BI 4 – 5), that is, predominantly in the middle of the Lingulid Sandstone Member. Whether the sandstone that is draped by the lamination is plane, dipping or undulating, is difficult to determine in sections where the lamina is thin or sparse.

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The parts with abundant mudstone lamina are characterized by a brownish green color and are characterized by thorough bioturbation. Despite bioturbation, some draped irregular surfaces can be seen. The lamination or drapes are generally thin (1 – 2 mm), but here occasionally make up very dense stacks of 1 – 2 cm. The contact between over and underlying units is gradual, and each section can be between 20 cm and 2 meter.

The lower portion of lithofacies 5 is rich in pyrite. The pyrite occurs within a span of 3.5 m in the lower part of the Lingulid Sandstone Member, approximately between 13.1 and 17.6 m (Fig. 11 – 12). In places, the pyrite consists of euhedral crystals. Commonly, these are anhedral crystals that occur scattered throughout the section, as well as some large clusters.

Figure 24. Photographs showing very fine to fine-grained, quartz-cemented, massive or thinly laminated sandstone (lithofacies 5) that make up the entirety of the Lingulid Sandstone Member in the Kinnekulle-1 drill core. Letters (A) through (G) represent an upward succession of samples in the core, (H) represent the second-to-the-top while (I) represent the top-most sample. (A) Cross-laminated sandstone with a vertical burrow in the upper right of the photo. Represents KC-15 (Fig. 10). (B) Example of massive appearance of the sandstone in lithofacies 5. Represents KC-16 (Fig. 10). (C) Vaguely visible, gently dipping or planar lamination and very thin streaks of fines. Represents KC-17 (Fig. 11). (D), (E) High frequency of thinly laminated fines with more bioturbation. This part of the core has an overall greenish-brown character due to interspersed fines. (D), (E) represents KC-18 and KC-19 respectively (Fig. 12 – 13). (F), (G), (I) Represents a gradual upward absence of the thinly laminated fines. Small brownish cluster of pyrite can be seen in the center of (F). These represent KC-20 (F), KC- 21 (G) and KC-22 (I) (Fig. 13 – 15). (H) The upper-most part of the Lingulid Sandstone Member where the thinly laminated fines are still present but nearly indistinguishable. Represents KC-23 (Fig. 15). Interpretation Lithofacies 5 is difficult to interpret due to the lack depositional context in form of associated facies, and poorly distinguishable sedimentary structure that reflect depositional processes. It is possible that many such structures may have been lost due to bioturbation. The

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bioturbation appears to be most evident in the portions with an abundance of thinly laminated fines. One possibility is that an abundance of muddy lamina represents an environment preferable to burrowing organism. However, sedimentary structures are also sparse in parts where the thinly laminated fines are sparse. This suggests that the bioturbation is likely highlighted by the lamina. It is also possible that the massive portions that are sparse in lamina, also has bioturbation but which cannot be distinguished. Another possibility is that these massive beds are a depositional feature, especially such that occur in the otherwise heavily bioturbated, abundantly laminated portions. There are only few sharp contacts, which together with the thorough bioturbation, suggest that sediment influx did not have a great effect on the bioturbating organism in the environment. This may suggest that events of erosion or rapid deposition were rare.

The pyrite commonly shows a great variety in grain size and consist in places, of very large euhedral crystals, this suggest that this is not detrital pyrite which would show some evidence of transport. Most likely the pyrite formed in-situ as a digenetic feature. Pyrite diagenesis is a common feature in sandstone, and normally precipitate under locally reducing conditions around organic matter or in anoxic basins (Pettijohn et al., 1987).

In upward succession, lithofacies 5 transition from sparse lamination, to abundant lamination, and back to sparse lamination again. The grain size of the quartz in lithofacies 5 does not appear to change significantly upward. Instead the coarsening and fining upward is seen in the frequency of the interspersed lamina. If abundant lamina represents a calmer or deeper environment and the sparse lamina represents more energetic or shallower environment; the lower half can be interpreted as a deepening upward, and the upper half can be interpreted as a shallowing upward.

Moreover, the rhythmic character of the thin mudstone lamina is overall similar to the rhythmicity of the interbedded mudstones of lithofacies 2. Lithofacies 5, however, appear to be much more bioturbated and contain much less clay and more mica than the mudstone in lithofacies 2. This may be interpreted as a gradual transition from one environment to another. Conversely, despite the gradual lithological transition from the Mickwitzia Sandstone Member, the associated conglomeratic beds, irregular surfaces and sudden absence of sedimentary structures may suggest a subtle depositional hiatus or period of erosion that separates the Lingulid Sandstone Member from the Mickwitzia Sandstone Member.

Lithofacies 6: Sandstone-pebble conglomerate

Description Lithofacies 6 is characterized by a largely clast-supported, monomict sandstone-pebble conglomerate that make up 20 – 30 cm on top of the Lingulid Sandstone Member, located at 33.6 – 33.8 m (Fig. 25). The conglomerate comprises very well-rounded, spherical or elongate, pebble-sized arenite sandstone clasts, and to a lesser extent, interstitial fine to granule-sized sand. Many of the larger and elongate clasts are imbricated, which is less evident in the smaller clasts where the clasts tend to be more rounded. Clast size vary from the bottom to the top 43

of lithofacies 6; the bottom and upper parts of the conglomerate appear to contain poorly sorted and generally larger sandstone clasts together with lesser amounts of interstitial sand, while the middle part comprises moderately sorted and generally smaller sandstone clasts with greater amounts interstitial sand. Horizons of quartz-sand in the middle part are in places well sorted. The sandstone clasts contain very well sorted grains made up of largely spherical and discoidal, fine to medium-grained quartz. The sandstone clasts also contain very sparse amounts of feldspar and plagioclase. One granule-sized clast of sedimentary rock containing sandy shale was found in the conglomerate.

Figure 25. Photographs showing a vaguely imbricated, rounded, sandstone-pebble conglomerate (lithofacies 6). It is located above the top of the Lingulid Sandstone Member in the Kinnekulle-1 drill core. (A), (B) Represents the lower part of the conglomerate, and they show two different sides of the same section of the core, the right side in (A) corresponds to the left side in (B). Imbrication can be seen toward the right in (A) and to the left in (B). The conglomerate is coarser in the top and the bottom with a finer, sandy, matrix-forming horizon in the middle. Interspersed black shale can be seen predominating in the sandy parts. Parts of sandy matrix without shale in the middle-left and upper- middle-right can be seen in photo (A). (C) Represents the top-part of the section. Shows an upward continuation of the coarse clasts seen in the upper part of (A) and (B). The black shale can be seen in the upper-most sandy part, but is largely absent in lower part of photo. Represents KC-24 (Fig. 16).

The interstitial matrix between some of the pebble-sized clasts primarily consists of sand or sandstone clasts with a composition of quartz, largely similar to that which constitutes the pebble-sized sandstone clasts. Most of the sandstone clasts have quartz cement, although much of the interstitial sand as well as partly some of the sandstone clasts are cemented or infiltrated with dark greenish mudstone like that of the overlying black shale of lithofacies 7. However, in some parts of the matrix the dark mud is absent, these parts appear to be

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cemented similar to the quartz-cemented sandstone clasts. In places, minor parts of calcite are found to make up the innermost contacts between sandstone clasts.

Interpretation According to Prothero and Schwab (2004), conglomerates can be deposited in a number of environments such as deep and shallow seas as well as fluvial, alluvial and glacial environments. However, tillites are commonly very poorly sorted and normally show clear angularity. Sediment gravity flows that could indicate turbidites in a deep-sea environment, or debris flows in alluvial an environment, does commonly not show clast supported or internally organized fabric (Nichols, 2009). Conglomerates found in shallow marine sequences are sometimes associated with ‘transgressive lags’, produced as shoreline deposits (Prothero and Schwab, 2004). The overlying lithofacies 7 indicate that such a marine environment most likely existed during some point of the transgression. Although currents do occur to some degree in marine environments, the imbricated clasts and the overall better sorted horizons, together with the degree of rounding can more easily be interpreted as bedload transport and deposition from currents in a fluvial environment. Based on the maximum clasts size and the variation within different horizons of the conglomerate, it is likely that such currents may have periodically reached high energy or flow-velocities.

The large clasts size and the similarity in lithology to lithofacies 5, suggests a relatively short transport distance, and that clasts were likely derived locally. The differently cemented parts are interpreted as two separate events; the quartz-cemented sandstone-pebbled was deposited first, after which the conglomerate was partially cemented with quartz, subsequent burial caused infiltration of pore spaces from the overlying black shale.

Lithofacies 7: Black shale

Description Lithofacies 7 consists predominantly of black shale and is part of the Alum Shale Formation. The part studied here is located between 33.5 m – 36.0 m, but continue further upward (Fig. 16). The black shale rests conformably on the conglomerate of lithofacies 6. In addition to the black shale, lithofacies 7 also contains thin (<1 cm), homogenous sandstone interbeds that occur in the lowermost 1 meter, approximately between 33.8 – 34.5 m. It also contains very thin (<2 mm) layers of limestone that commonly occur throughout the black shale.

Interpretation The predominance of mudstone suggests that energy conditions were very calm. Although sparse, the thin interbedded sandstone layers suggest that some processes that deposited sand did occur initially. The absence of the sandstone beds in the upper parts may be seen as an increase of depth, distance to the shoreline or paucity in sediment transport and reworking. The black shale can be interpreted as deposited in an offshore environment, or an environment restricted from storm-waves. The Alum Shale is believed to be overall deposited in a restricted, shallow marine environment with prevailing low-energy conditions (Calner et al., 2013). 45

4. Discussion Based on observations and interpretations in chapter 3.3, a stratigraphic summary diagram is presented (Fig. 26), in which the main points of the lithological and depositional features are presented, together with a model for sea-level change based on depositional environment in relation to wave base. These features are further discussed in chapters 4.1, 4.2 and 4.3.

Figure 26. Stratigraphic summary diagram based on observation and interpretation in chapter 3.3. Includes a compressed version of the log seen in Fig. 8 – 16. The right side shows a model for possible sea-level change, based on depositional environment in relation to SWWB and FWWB.

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4.1. Peneplainization and the development of the basal conglomerate Based on the observations in this study and previous reports, the conglomerate represents a sediment with pre-weathered clasts, evidence of marine processes, and possibly eolian processes. The evidence for weathering within feldspar as well as cementation within the conglomerate, suggests that chemical maturation and cementation probably occurred during or after the early Cambrian. The conglomerate also contains clasts, of which it is possible, that some were derived locally while others were transported from elsewhere.

The whitish character and the weathering seen in the upper part of the basement is consistent with an intensively weathered sub-Cambrian peneplain. The weathered basement at Lungås has been described as porous with quartz-calcite replacements and hematite inclusions (Hadding, 1929, as cited in Lidmar-Bergström, 1997). The basement below Cambrian strata elsewhere has also been reported as kaolinized to a maximum of 5 m underlying Cambrian strata in Närke (Hedström and Wiman 1906, Högbom and Ahlström 1924, Högbom 1931, Hadding, 1929, as cited in Elvhage and Lidmar-Bergström, 1987). Kaolinite has also been reported as inclusions within the overlying conglomerate at Lugnås (Lidmar-Bergström, 1997). The locality at Lugnås show horizons of clayey material which may be kaolinite. However, such clayey material is not found within any of the conglomerate samples collected at Kinnekulle, or in the conglomerate or gneiss in the drill core. Moreover, clay mineralogy has not been analysed in this study, and kaolinite cannot be reliably distinguished in thin section; thus, kaolinite may exist, but the amounts are likely very sparse. Some degree of kaolinization in the basement would be expected, as kaolinite is a common constituent in weathered feldspar (Prothero and Schwab, 2004).

Kaolinite may be present within the whitish feldspar grains that make up the overall whitish character of the upper 1.5 meter of the gneissic basement in the core. However, these are shown be largely weathering or alteration textures of feldspar, that are associated with quartz-calcite-hematite replacements. If the feldspar was initially weathered into kaolinite and was subsequently replaces by quartz and calcite; this is something that can no longer be seen or distinguished in thin section. The quartz and the calcite in these parts have a fine- grained, patchy character, and calcite does not show the typical calcite twinning. One possibility is that this reflects step-wise quartz-calcite replacement of the feldspars. Another possibility is that quartz-calcite replacement represents a step-wise replacement of clay- minerals previously constituted parts of the weathered feldspars.

In addition to kaolinite, illite can also be considered a weathering product in very old sandstones. Flaky or filamentous, diagenetic illite have been found to constitute weathered K-feldspar in the late Proterozoic sandstones of the Visingsö Formation in south-central Sweden (Morad and AlDahan, 1987, as cited in Chamley, 2013). They found that the illite was likely produced by dissolution and crystallization, from which the orientation of the illite- crystals was believed to follow the feldspar-cleavage orientation. They also suggest that the illite formation in preference rather than kaolinite, may have been associated with the composition together with less acidic conditions of groundwater, which could favour illite

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formation. Although none of these features have been possible to distinguish in thin section, it is still possible that this may be the case in the conglomerate at Kinnekulle as well. Because clay minerals have been not analysed in this study, this remain an open question for further research. In addition to the pH-conditions during weathering into clay minerals, this is also something that is interesting in regards to the formation of calcite.

The quartz-cemented parts in the conglomerate are suggested to be cementation that occurred before the transgression (Hadding, 1929, as cited in Jensen, 1997). In this study, the conglomerate shows quartz cementation that appears to occur preferentially in places that are better sorted and dominated by quartz grains. The quartz-cemented parts appear anomalous in the otherwise predominantly calcite-cemented conglomerate, they may be intra-clasts, or horizons that have been cemented with quartz at an earlier time, and later reworked or redistributed within the conglomerate.

Only a few conglomerate samples used in this study are stratigraphically controlled, and they represent either the lower or upper contact. The conglomerate in the Kinnekulle-1 drill core is very thin compared to the conglomerate in the drill core logged by Jensen (1997) and the conglomerate at Lugnås. It is likely that the conglomerate in the Kinnekulle-1 drill core reflects deposition on a topographic high in the basement. Additionally, except for very small sections of quartz-cement, the conglomerate in the core is dominated by calcite cement. It is possible that the conglomerate in the Kinnekulle-1 drill core represent a later stage of the development.

It has been suggested that grains hematite occurring in the gneiss is evidence for alteration that took place before the transgression, such loose grains of hematite in the overlying conglomerate were also suggested as derived from the basement during denudation (Hadding, 1929, as cited in Lidmar-Bergström, 1997). No individual grains of hematite composition were identified in this study, but there are small inclusions iron-staining that occurs in the conglomerate and in the gneiss. Additionally, the overlying conglomerate contains grains of heavily weathered feldspar interpreted as derived from the gneissic basement. These contain fine-grained, patchy quartz and calcite similar to the altered feldspar observed in the basement. This further supports the idea that there was alteration and weathering of the basement before the transgression. The conspicuous quartz-calcite replacements are in places found floating within the calcite matrix that makes up large portions of the conglomerate. In these places, the feldspar grains in which the quartz-calcite replacement occurs show partial or complete replacement by the better developed calcite cement that is largely present throughout the conglomerate. However, in many cases where these feldspars can be seen, the outline of the grain boundary is preserved. This suggests that the quartz-calcite replacement are only occurring in feldspar grains. The feldspar grains were likely pre-weathered in the basement, and must thus also have been derived from there. It is evident that, in addition to a previous stage of weathering within the basement, the feldspar grains also experienced significant weathering within the conglomerate, meaning that the

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calcite in the patchy quartz-calcite replacement is older than the matrix-forming calcite in the conglomerate.

The calcite cement in the conglomerate of lithofacies 1 can also be seen in the lowermost part of the overlying interbedded sandstone and mudstone of lithofacies 2. Most of lithofacies 2, however, is predominantly quartz cemented. The similarity of ripple structure present in the top of lithofacies 1 and base of lithofacies 2, together with the presence of calcite cement, suggests that the top and likely most of the conglomerate was not lithified during the time of transgression.

At the Trolmen locality, the conglomerate is separated from the basement by a 5 – 15 cm thick bed containing a lower clay-rich bed, and an upper, rippled sand bed (Hadding, 1927, as cited in Jensen 1997; Jensen, 1997). It is unclear whether this bed was deposited before or after the conglomerate. One possibility is that the sandstone bed was deposited as part of a fluvial channel where the conglomerate was eroded down to the gneiss. This area may later have been covered by surrounding conglomerate, possibly during transgressive reworking. However, the sandstone bed is most readily explained by that it is older than the overlying conglomerate. Basal sandstone beds such as the one at Trolmen, may originally have had a wider extent. One of the samples from Råbäcks hamn that contain the contact between the basement and the conglomerate show filling of fine-grained sandstone within a crack in the basement. The fine-grained sandstone in the crack may have originated from a sandstone bed that existed there before the conglomerate. Although there is nothing that suggests that deposition of the sandstone bed and the filled crack are related to the time of quartz-calcite replacement in the basement; it may indicate that deposits of other sediment existed in the area before saprolite formation. Lidmar-Bergström et al. (1997) suggested that thick saprolite did not develop due to the absence of vegetation on the early Cambrian landscape. If the basal sandstone bed and the sand-filled crack are older than the conglomerate, the preservation of these at the top of the gneiss would mean that the gneiss cannot have been deeply weathered during saprolite formation.

The similar weathering characteristics of feldspar is suggesting that some material come from basement rock similar to that which directly underlies Kinnekulle. In addition to this, textures and composition suggests that some of the material in the conglomerate were also likely derived from a local pegmatite source. This was also suggested by Högbom and Ahlström (1924) and Hadding (1927), as cited in Jensen (1997). The pegmatite clasts also can also be seen at Lugnås (Nathorst, 1885, 1886; Hadding 1927, as cited in Jensen, 1997; this study). At the Lugnås locality, these clasts appear to be sparser than at Kinnekulle, which may reflect a greater distance to the source. No specific source area has been suggested for the pegmatitic clasts and no occurrences of pegmatites have been mapped in the immediate area near Kinnekulle or Lugnås. It is possible that such an area may be concealed below the surface of Lake Vänern, beneath soil cover or under sedimentary rocks in the region.

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Previous interpretations of the worn clasts in the conglomerate, include wind-faceted ventifacts (Lidmar-Bergström, 1997, and references therein). In this study, no good examples of ventifacts were identified; the smooth, flat surfaces and rounded edges of many of the larger pegmatitic clasts in the conglomerate, could have been abraded or reworked in an eolian environment. However, it is uncertain whether these are actual wind-faceted clasts or if the surfaces reflect crystal faces. Some of the pegmatite clasts have shapes reflecting rounded, but well-developed euhedral crystals. The rounding was most likely attained during transport from the source area. The size of many of these clasts suggests that the transporting agent must have been strong, possibly associated with fluvial processes.

The composition and textures of sedimentary-rock clasts in the conglomerate are shown to be predominantly mica-bearing, fine-grained, sandstone and mudstone. Such sandstone clasts are found at Lugnås (Jensen, 1997; this study), and Jensen (1997) also found them at Kinnekulle at the Hjälmsäter locality, but not at Trolmen locality. The sandstone clasts have been described as siderite-rich and mica-rich pebbles (Westergård, 1931b, as cited in Jensen, 1997) or “elongated, rounded clasts of fine-grained material, clay and silt, with occasional larger grains” (Jensen, 1997). One possibility is that the sandstone clasts may have been derived from sandstone in surrounding basins, such as the Dalarna basin or the Vättern rift- basin. Another possibility is that the sediment in such basins originally had a wider extent. A third possibility is that another sedimentary rock-cover existed at some point before peneplainization, and which may have remained as remnant outliers forming some local topography during the development of the basal conglomerate.

The sandstone clasts are well cemented, and the rounding is thus interpreted as an indication of transport or reworking, rather than poor mechanical competence. The relatively large grain size is comparable to that of the pegmatite clasts, which may indicate a similar local source. One possible source is the ‘basal’ sandstone bed described previously as underlying the conglomerate at Trolmen. However, it is uncertain whether the sandstone bed is younger or older than the conglomerate, or if it is a part of the conglomerate. In any case, it is unlikely that the clasts originating from the specific bed at Trolmen, such clasts would likely have seen only little transport which would result in more angular shape. What is more likely is that, similar basal sandstone beds existed elsewhere, from which material was eroded, transported and deposited during formation of the conglomerate.

The basement-derived feldspar together with cross-lamination and ripple structures are a few examples suggesting that the conglomerate is overall consistent with a saprolite that formed by denudation and erosion of the basement, and which was subsequently reworking by marine processes (Lidmar-Bergström et al,. 1997). Whether the conglomerate experienced eolian activity, as suggested by reports of ventifacts and dreikanter, appear less certain as no good examples of such are found in this study. In addition to the overall roundness of sand- sized grains within the conglomerate, the only thing that suggests eolian reworking is the smooth surfaces found especially on pegmatite clasts, which can be interpreted as wind abrasion. Although it is possible that several clasts may have been part of a surface exposed

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to eolian processes, the smooth surfaces alone may not be sufficient for an interpretation of eolian reworking.

It is difficult to determine how much the textures and composition of lithofacies 1 reflect saprolite formation during peneplainization. The conglomerate contains several compositional and textural features that can be traced to weathering of the basement, but it also records a history of reworking, cementation and chemical maturation that likely occurred after, or during deposition of the overlying early Cambrian succession.

4.2. Marine environments represented by the Mickwitzia Sandstone Member The marine deposits of the Mickwitzia Sandstone Member include lithofacies 2, 3 and 4 as well as the upper part of lithofacies 1. The distribution of lithofacies 2 and 3 show that deposition initially took place in a wave-dominated environment that frequently alternated between storm and fair-weather conditions. The overall coarsening upward and shift toward increasingly storm-influenced facies, as indicated by the more dominant lithofacies 3 in the middle and upper parts, suggest either that the intensity of storms increased, or that the environment was more shallow.

The absence of other associated facies makes it difficult to determine the depositional context. There are gaps in the record, represented by small unconformities that occur where more proximal facies would be expected. These ‘missing facies’ occur at the base of the Mickwitzia Sandstone Member where lithofacies 2 is directly overlying the largely terrestrial lithofacies 1, but also in the lowermost part of lithofacies 5 that constitute the basal Lingulid Sandstone Member, where an irregular surface is interpreted as erosion or a depositional hiatus.

Overall, the observations and interpretations presented in this study are largely consistent with observations and interpretations made by Jensen (1997). Jensen (1997) interpreted the shallowing upward, storm-influenced Mickwitzia Sandstone Member as deposited below normal wave base in relatively shallow water some distance from the shoreline. Jensen (1997) also presented a log with an informal division (A through D) of the deposits in the Mickwitzia Sandstone Member at Kinnekulle. These divisions can readily be recognized in the lithofacies boundaries shown in Fig. 17. Thick individual beds can also frequently be correlated, indicating that they are relatively homogenous in lateral extent.

The log presented in Jensen (1997) has also been interpreted in a sequence stratigraphic context by Nielsen and Schovsbo (2011). They suggest that the transition from the conglomerate (lithofacies 1) to the interbedded sandstone and mudstone (lithofacies 2), is a Transgressive Systems Tract. They also interpret the coarsening upward (the overall transition from lithofacies 2 to lithofacies 3) in the upper half of the Mickwitzia Sandstone Member, as a Falling Stage Systems Tract.

One difference in the interpretations by Jensen (1997) include the coarse-grained, rippled bed, in this study, they are interpreted as a part lithofacies 2 that were deposited on the lower

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shoreface. Jensen (1997) suggests that these may be shoreface deposits (upper shoreface in this study). Although the coarse grain size stands out as anomalous in these otherwise fine- grained deposits, the presence of interbedded fair-weather mud and the general appearance of the coarse-grained beds indicate a similar type of deposition that predominates in lithofacies 2. Because these coarse-grained sandstone beds occur together with predominantly lithofacies 3, it is reasonable to assume that they were deposited in a shallower environment than much of lithofacies 2, possibly the transition between the lower shoreface and upper shoreface.

Another difference is the ‘disrupted sandstone and mudstone’ (lithofacies 4 in this study). Jensen (1997) interpreted the structures as bioturbated and storm-modified dune deposits, based on fragmentary body fossils and locally abundant but poorly preserved trace fossils of Rhizocorallium jenense. In this study, lithofacies 4 can be interpreted as produced either by bioturbation or soft sediment deformation. The interpretation for bioturbation is primarily based on different types of deformation in comparison to lab experiments. The lithology and the coarsening upward within these parts of respective core appear similar. However, the ‘disrupted sandstone and mudstone’ appear to be nearly twice as thick in the core logged by Jensen (1997). This difference in thickness of the ‘disrupted’ section could be then seen as an indication of a post-depositional process, and may be better reconciled with the interpretation of large-scale soft-sediment deformation rather than bioturbation. On the other hand, it could be that bioturbation occurred preferentially on the sea floor in some areas. Whether the structures were produced by organism or liquefaction is difficult to determine. There is a great similarity to soft-sediment deformation structures, but the lack of three-dimensional and lateral view in the drill core, ultimately make this interpretation less reliable than the interpretation of bioturbation.

Lithofacies 2 and 3 are interpreted as tempestite deposits. However, they are rather atypical when compared to descriptions of better known tempestite deposits. Models for storm deposits commonly include several indicative features reflecting processes that take place during a storm event and the gradual transition toward fair-weather conditions (Dott and Bourgouis, 1982; Walker, 1984; Brenchley, 1989). In these models, the presence of HCS is perhaps the most important indication of a storm event. Although lithofacies 2 and 3 constitute many indicative features described in the depositional models, the fact that HCS cannot be reliably distinguished in the drill core is one problem with interpreting lithofacies 2 and 3 as storm dominated facies. However, lithofacies 3 does in many places show truncated, sub-horizontal, cross-lamination and that would be an expected view of HSC in a drill core. Such beds of lithofacies 3 that occur in the upper part of the Mickwitzia Sandstone Member, have been described by Jensen (1997) as steep HCS-beds containing skolithos. This is one argument for suggesting that the more uncertain cases of HCS in lithofacies 3, further down in the Mickwitzia Sandstone Member, may also be a type of HCS-beds.

Lithofacies 2, which dominates the lower part of the Mickwitzia Sandstone Member, shows cm-scale cross-lamination that is interpret as a type of small-scale HCS. These are present in

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graded beds of fine sand and silt interpreted as deposited during early waning of the storm. The graded fines above these beds are interpreted as being deposited during the latter waning stages or after the storm. The lowermost bedded sandstone in the composite sets of sandstone and mudstone in lithofacies 2 is interpreted as deposited during the peak of the storm. These beds are associated with moderate wave-action and combined flows producing oscillatory and interference ripples, which are not typical for peak storm-deposition. This may instead represent weak storm-influence at increased depth or a distal setting, close to the storm-wave base. However, considering lithofacies 2 and 3 together, an interpretation that these are tempestite-deposits still appear the most probable.

The flat intra-cratonic setting, and the absence of large terrestrial vegetation, are factors that have been suggested to have influenced deposition and preservation of Cambrian sediments (Dott, 2003). Facies that are proximal or distal to those seen in the Mickwitzia Sandstone Member in Västergötland appear to be absent, which makes determining depositional environment difficult. However, lithofacies 2 and 3 are largely comparable to tempestites in North America described by Runkel et al. (1998). The tempestite facies described by Runkel et al. (1998) are of Cambrian age from the Upper Missisippi Valley (UMV), where deposition took place in a flat, stable, intra-craton setting. Runkel et al. (1998) argue that such deposits were not dependant on atypical terrestrial conditions such as eolian and fluvial reworking of terrestrial sediment on the craton prior to the Cambrian transgression.

Further, the tempestite deposits described in Runkel et al. (1998) consist of fine-grained, rippled and normally graded sandstones and siltstones, as well very fine to fine-grained sandstone that include small-scale HCS, much like lithofacies 2 and 3 in this study. The tempestites described by Runkel et al. (1998) are geographically and stratigraphically well constrained, and interpreted as deposited in an offshore environment, but above SWWB. It is possible that a similar situation was the case during deposition of lithofacies 2 and 3 in the Mickwitzia Sandstone Member.

Runkel et al. (1998) based the bathymetric estimation on storm currents on modern shelves that occur to a depth of 180 m, but argued that the epeiric setting must have meant that such depth was significantly lower. They argue that such a wide and low-gradient, epeiric shelf can be better compared to modern-day Bering Sea, where storm erosion of the sea floor occurs at a maximum of 70 m. One hypothesis endorsed here, which was similarly suggested by Jensen (1997), is that, the low gradient of such embayment or shelf like the Cambrian UMV, Bering Sea or the peneplained surface in south-central Sweden, may have served to distribute storm-wave energy over a much wider area than is the case on steeper shelves on the continental margin.

4.3. Marine environments represented by the Lingulid Sandstone Member The Lingulid Sandstone Member in the core consists entirely of lithofacies 5. The lack of depositional context in form of associated facies, together with the general absence of sedimentary structures and the small variations in lithology, make this part of the core difficult

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to interpret. The grain size of the sand appears to be largely similar throughout, but the variation in frequency and thickness of the interspersed, thin laminations of mud and mica is interpreted as a fining or coarsening upward. This suggests a deepening upward in the lower half, and shallowing upward in the upper half of the Lingulid Sandstone Member. Although lacking detailed descriptions, this unit was interpreted by Nielsen and Schovsbo (2011) as an overall coarsening upward sequence.

Regarding the contact between the Mickwitzia Sandstone and Lingulid Sandstone members. One possibility is that this represent a gradual transition from one environment to another, as sandy lithologies are commonly associated with shoreward facies (Prothero and Schwab, 2004). The Mickwitzia Sandstone Member record deposition of sand that shift upward to become dominant at the transition to the basal, sand-dominated Lingulid Sandstone Member. Additionally, the interspersed mud of lithofacies 2 and 3 in the upper parts of the Mickwitzia Sandstone Member, is thinner, greenish and overall more similar to the fine lamina in lithofacies 5. If this is a continuation of the shallowing upward from a lower shoreface, as indicated by the deposits in the Mickwitzia Sandstone Member, one would expect the Lingulid Sandstone Member to represent an even shallower, possibly upper shoreface. However, lithofacies 5 show no such indications that represent a shallower environment. Instead, the fine lamina, thorough bioturbation, low frequency of cross-laminated beds, and sharp contacts in lithofacies 5, suggest an environment in which calm conditions prevailed while reworking and rapid deposition of sediment occurred less frequently. It is possible that lithofacies 5 and the Lingulid Sandstone Member represents an even deeper environment than the Mickwitzia Sandstone Member. It is possible, but less probable, that the Lingulid Sandstone Member represents a shallower and more proximal environment than the Mickwitzia Sandstone Member, but with the difference that storm energy is somehow dampened further by the flat inland shelf.

It has previously been suggested that the Mickwitzia Sandstone and the Lingulid Sandstone members are separated by a hiatus (Bergström and Gee, 1985, as cited in Nielsen and Schovsbo, 2011). Nielsen and Schovsbo (2011) suggested that this contact may represent a sub-aerial unconformity. In this study, the transition between the Mickwitzia Sandstone and the Lingulid Sandstone members is placed at a coarse-grained bed at the upper-most occurrence of lithofacies 2. However, a coarse-grained, somewhat irregular and conglomeratic surface is present at 10.3 m. This has also been reported at the same level by Jensen (1997), who also reported such an occurrence at a similar level at localities of Hällekis and Trolmen. This may represent the hiatus or unconformity suggested by Bergström and Gee (1985) and Nielsen and Schovsbo (2011). However, the beds that make up the 0.9 m underlying the irregular surface are more similar to lithofacies 5, that is, more like the rest of the overlying Lingulid Sandstone Member. The beds directly underlying the irregular surface are interpreted by Jensen (1997) as shoreface deposits (upper shoreface in this study). Upper shoreface deposits are usually not well preserved in the stratigraphic record (Prothero and Schwab,

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2004), and it is possible that the irregular surface at 10.3 may represent a lasting period in which erosion or non-deposition occurred on the upper shoreface.

Despite the sparsity of indicative structures, the interpretation that the Lingulid Sandstone Member was deposited in deeper water than the Mickwitzia Sandstone Member, and that it is separated from the Mickwitzia Sandstone Member by a period of erosion or non-deposition, is supported by sequence stratigraphic analysis and paleogeographic reconstructions (Nielsen and Schovsbo, 2011). According to Nielsen and Schovsbo (2011), the basin geometry changed significantly between deposition of the Mickwitzia Sandstone and Lingulid Sandstone members; large landmasses that connected south-central and northern Sweden to landmasses of Finland and Russia, which made up the interior of Baltica, were disconnected as the sea transgressed the outline of the modern-day Baltic Sea and Bothnian Sea. This resulted in a landward displacement of the shoreline that shut off all major landmasses except for a narrow peninsula on present-day western Baltica, stretching along the axis of central to northern Sweden. One possible hypothesis is that flooding of landmasses and fluvial systems led to slowing aggradation and an increased reworking of pre-existing shelf-sediment. This may have resulted in sand-rich deposits such as the Lingulid Sandstone Member on the lower shoreface, or transition to an offshore environment.

4.4. Development of the sandstone-pebble conglomerate and the following transgression The sandstone-pebble conglomerate in lithofacies 6 at the top of the Lingulid Sandstone Member represents a drastic change from the marine environment in which lithofacies 5 was deposited. Lithofacies 6 is interpreted to be an intra-formational conglomerate, as the composition indicate that the source of the material in lithofacies 6 is likely the underlying lithofacies 5. This suggests that lithofacies 5 must have been lithified at the time, which implies burial, meaning that the conglomerate is likely to have developed above a major unconformity.

Further, as indicated by clast size and internal structure, the interpretation here is that lithofacies 6 likely developed in a terrestrial environment where the landscape probably had enough topography to produce a pebbly conglomerate. Considering these interpretations together with the placement at the top of the Lingulid Sandstone Member; lithofacies 6 can be seen as a part of the region-wide unconformity of the Hawk Bay Event, which occurred during the transition between the early and middle Cambrian (Nielsen and Schovsbo, 2011).

Based on Nielsen and Schovsbo (2011; 2014) and references therein, the unconformity represents sub-aerial exposure that spanned over much of Baltoscandia. Conglomerates at the top of the Lingulid Sandstone Member has also been reported from Östergötland (i.e. Bårsta-2 core) and other places, where it is recognized as marking the sequence boundary. The unconformity developed diachronously over much of Baltoscandia, while Västergötland has been suggested to be one of the places in which there was perhaps the longest time gap between deposition of units underlying and overlying the unconformity. The unconformity likely occurred as a result of uplift that coincided with sea-level fall (estimated to have

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exceeded 100 m) due to global plate-tectonic rearrangement. During approximately 6 Ma in the latter half of Cambrian stage 4, the shoreline was displaced to present day southern Denmark, northern Germany and Poland.

Considering the time span during which lithofacies 6 and similar conglomerates in south- central Sweden may have developed, it is surprising that they are relatively thin deposits, suggesting that there may in fact have been very little topography and sediment-producing areas. However, significant burial likely occurred before lithification of the underlying Lingulid Sandstone Member. If this was that case, the sediment overlying the Lingulid Sandstone Member at this point, was likely the source of large amounts of sediment that must have been transported away. It is possible that the rounding, vague layering, sorting and somewhat imbricated character of lithofacies 6 may reflected fluvial processes such as braided stream systems that existed on a relatively flat, vegetation-free landscape. It is also possible, but appear less likely, that such textures were attained from marine processes during transgression, before deposition of the overlying black shale. The black shale in lithofacies 7 is interpreted as a marine shale deposited relatively shallow, restricted environment, or offshore environment. There are no intermediate facies that record the transgression, which may suggest that there was a depositional hiatus during the transgression. It also possible that facies representing a more proximal environment may have been eroded away, but it appears unlikely that this should have occurred in the depositional environment represented by lithofacies 7. Another possibility is that the shift from a terrestrial (lithofacies 6) to a marine environment (lithofacies 7) may have been rapid from a geologic perspective. According to Gee (1987), Cambrian tectonism on the Baltoscandian margin was associated with the Caledonian orogeny, and may have been contemporaneous with deposition of the Alum Shale Formation on the Baltoscandian platform.

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5. Conclusions In this study, the petrography and the depositional facies of the early-middle Cambrian succession at Kinnekulle have been described, interpreted and discussed. What follows is a summary of the conclusions made about the material produced and the weathering during the period of peneplainization, as well as depositional processes, depositional environment and changes in sea-level that occurred during the early Cambrian transgression.

 The gneissic basement from the core represents an intensely, but relatively shallow weathered part of the sub-Cambrian peneplain. Significant weathering occurred predominantly within feldspar grains, in which quartz-calcite replacements represent a period of weathering that took place prior to deposition and calcite-cementation of the overlying conglomerate.  The basal polymict conglomerate represents a sediment partly derived from underlying weathered basement, local pegmatite veins, and remnant outliers of sedimentary rocks, the latter of which predominantly consisted of sandstone and mudstone. The upper part of the conglomerate was unconsolidated (except for intra-clasts of quartz-cemented conglomerate) when it was reworked by marine processes during the early Cambrian transgression. Significant chemical maturation occurred through calcite-replacement of feldspar, which likely occurred subsequently to burial beneath early Cambrian rocks.  The Mickwitzia Sandstone Member consists of interbedded sandstone and mudstone associated tempestite facies formed on the lower shoreface. These were deposited under oscillatory-dominated combined flows, and suspension-settling that occurred during peak-stage, waning-stage and fair-weather conditions. Thickly bedded sandstone in the Mickwitzia Sandstone Member was deposited in a similar environment but during greater storm-influence. Coarsening upward and a transition to more storm-influenced facies represent deposition beneath, but closer to fair-weather wave base suggesting a shallowing of water depth. Disruptive features in the tempestite facies are conspicuously similar to soft-sediment deformation structures but can also be attributed to bioturbating organisms. These two mechanisms cannot be reliably differentiated in a drill core.  The Lingulid Sandstone Member may be separated from the Mickwitzia Sandstone Member by an irregular surface that may indicate erosion or a depositional hiatus. The overall absence of sedimentary structures and lithological variation make the Lingulid Sandstone Member difficult to interpret. Lithology and bioturbation suggest that this was an environment in which calm conditions prevailed, while erosion or rapid deposition of sediment occurred less frequently.  The eroded top of the Lingulid Sandstone Member represents the Hawke Bay unconformity. The overlying, intra-basin, sandstone-pebble conglomerate, developed during terrestrial erosion together with fluvial transport and deposition. Rapid transition from a terrestrial environment is represented by an absence of intermediate facies before deposition of black shale associated with a calm and restricted marine environment (Alum Shale Formation).

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6. Acknowledgements This study is part of a M.Sc. thesis at the University of Gothenburg, and was financed by the University of Gothenburg and Lund University. I would like to express my gratitude to my supervisors; Mark D. Johnson at the Department of Earth Sciences at the University of Gothenburg, and Mikael Calner at the Department of Geology at Lund University, who also provided the drill core that made this project possible. Their commitment and guidance, in the form of discussions, remarks and comments have been of great importance during the process of writing this thesis. I am also grateful to my examiner Rodney Stevens, for his advice and encouragement throughout, and to Adi Fazic, for serving as my opponent. Finally, I would like to thank Oliver Lehnert for producing the petrographic thin sections, as well as Tony Runkel and Kairi Põldsaar for providing valuable input and suggestions on interpreting sedimentological features in the drill core.

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