Provenance of Pebble Clasts in Hummocks in the Western South

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

PROVENANCE OF PEBBLE

CLASTS IN HUMMOCKS IN THE

WESTERN SOUTH SWEDISH

HIGHLANDS NEAR HÖRDA

Karin Grodzinsky Martin Thor

ISSN 1400-3821 B955 Bachelor of Science thesis Göteborg 2016

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

The southern part of Sweden contains areas with widespread hummock tracts, and their genesis has been studied for a long time. Using high resolution LiDAR-technique (Light Detection and Ranging), new observations and hypotheses for their genesis are possible. This thesis presents a provenance study of the material in hummocks and eskers in an area on the south Swedish highlands near Hörda. The hummock tract near Hörda is located in a valley, interpreted to be a tunnel valley, where hummocks in places are overlain by eskers. The aim is to investigate if the provenance of the material can help determine the genesis of the hummocks. In total, 1000 clasts were collected, half from five hummock sites and the other half from five esker sites. The lithology was determined, and the results from the sediment of each landform were tested statistically. The statistical test showed that there was a significant difference; however, most of the pebbles from both landforms seem to have been eroded from local sources. The samples also include many clasts with an interpreted provenance directly north of Hörda, with a maximum transport distance of 110km. These have most likely been transported by an earlier ice flow with a north-south direction and subsequently picked up by the latest glacier with the ice-flow direction from northeast and deposited in Hörda. Even though there was a significant difference between the eskers and hummocks, both are most likely derived from basal ice debris. This interpretation is strengthened by the geomorphology in the area, which suggests that the valley as well as the hummocks are formed by subglacial erosion. The eskers on top of the hummocks must have formed later, most likely as the ice retreated, but consist of the same material.

Sammanfattning

Den södra delen av Sverige består av områden med hummocks, varav deras uppkomst har studerats under en lång tid. Med hjälp av LiDAR-tekniken (Light Detecting and Ranging) och dess höga upplösning kommer nya förslag på deras bildningssätt upp. I denna rapport genomförs en proveniensstudie där materialet i hummocks och rullstensåsar undersöks. Området av intresse är beläget på det sydsvenska höglandet i närheten av Hörda. Området ligger i en dal, där vissa hummocks är överlagrade av rullstensåsar. Syftet är att se om materialets proveniens kan bestämmas och om det kan vara till hjälp att bestämma hummocksens bildningssätt. Totalt samlades 1000 stenar in, hälften från hummocks och den andra hälften från rullstensåsar. Proverna bergartsklassificerades och resultatet för varje landform testades statistiskt mot varandra för att se om det fanns någon skillnad. Det visade sig vara en signifikant skillnad, trots det verkade majoriteten av materialet från båda landformerna lokalt eroderade. De stenar som inte eroderats lokalt har sin proveniens norr om Hörda. Dessa anses ha transporterats från ett tidigare isflöde från norr, som sedan plockats upp av den senaste glaciären med isflödesriktningen från nordöst och slutligen avsatts i hummocks och rullstensåsar nära Hörda. Trots den signifikanta skillnaden mellan rullstensåsarna och hummocksen, är båda landformerna troligen avsatta av subglaciala mekanismer. Denna teori stärks av geomorfologin i området, som tyder på att dalen liksom hummocksen har formats av subglacial erosion. Rullstensåsarna ovanpå hummocksen måste ha avsatts senare, troligen under isens tillbakagång, men består av lika material.

Keywords: hummock tract, esker, South Swedish Highlands, provenance, glacial geomorphology, LIDAR

Table of contents Introduction ...... 4 Background ...... 5 Regional bedrock geology ...... 5 Scandinavian geology ...... 5 Sveconorwegian province ...... 5 Transcandinavian Igneous Belt ...... 6 Deglaciation of Småland ...... 6 Landform genesis ...... 6 Genesis of eskers ...... 6 Genesis of hummocks ...... 6 The study site: Hörda ...... 7 Deglaciation of the study site ...... 7 Local bedrock geology ...... 8 Local topography and geomorphology ...... 8 Methodology ...... 10 Field ...... 10 Laboratory ...... 10 Statistics ...... 10 Results ...... 11 Rock type classification ...... 11 Rock descriptions ...... 13 Form analysis ...... 18 Discussion ...... 21 Provenance study ...... 21 Form analysis ...... 24 Hummock formation ...... 24 Conclusions ...... 25 Acknowledgements ...... 25 Appendices ...... 28

forms that hummocks take. With its high Introduction resolution over the hummocky terrain, the precise shapes of hummocks are more The aim of this study is to provide insight into distinctly defined than before. An on-going how glacial hummocks are formed. The study project (Mark Johnson and Gustaf Peterson, area is in the southern part of Sweden and is University of Gothenburg and Swedish based on lithological provenance studies Geological Survey, SGU) is using LiDAR data to together with form analysis to help determine help re-interpret how the geomorphology and sediment and landform genesis. geology have developed. This Bachelor thesis Is it possible to interpret the provenance of will investigate if provenance studies are a the clasts in the till and, further, to get an useful tool for helping to interpret hummocky insight into how the hummocks were formed? deposit mechanisms, both for the current project but also for the general study of Hummocks are one of the most common hummocky deposits. glacial landforms, but their formation has been a topic of considerable discussion The study will separately examine clasts from (Johnson et al., 1995). The most common idea two different hummocky areas (here at Hörda, is that they are formed due to some kind of but also at Gullaskruv), and the same amount collapse of supraglacial material (Johnson and of clasts have been collected from eskers that Clayton, 2003). Other theories suggest that occur in the vicinity of the hummock tracts. thrusting in the ice creates a structure of The results will be compared to see if there is sediment inside the glacier, that can be a significant difference between the preserved and form hummocks as the provenance of clasts in the eskers as sediment is let down during melting (Hambrey compared to the hummocks. It is thought that et al., 1997). There is also possible that the comparative provenance of the material in hummocks can form subglacially (Johnson and the eskers versus the hummocks may provide Clayton, 2003). An example of this is the restrictions on various models of hummock conclusion made by Dahlgren (2013), where formation. hummocks were interpreted to have been This thesis is being carried out together with formed by subglacial meltwater erosion. In another bachelor project (Thor & Grodzinsky, this case, erosion forms a tunnel valley with 2016). The field and lab work was performed an irregular floor of glacial landforms that can together, but on the different sample sites at best be described as hummocks (Dahlgren, Hörda and at Gullaskruv. 2013). The provenance study in this thesis will be performed on one of the areas that was Because this study requires a good knowledge studied in the rapport by Dahlgren (2013). of the bedrock geology, we start with describing the regional geology, as well as the According to Andersson (1998), Möller (2010) basic concepts of landform genesis. Then we and Möller & Dowling (2015), the area present our study site. surrounding the study site consists of hummocks made primarily by stagnant ice. The debate continues, and the new LiDAR (Light Detection and Ranging) data, which is a part of the New National Elevation Model (NNH), has shed light on the many variable

Background gneiss. After the TIB granitoids formed 1,80- 1,65 Ga ago, the formation of the Regional bedrock geology Sveconorwegian province meant that the Baltic shield grew towards the west. The Scandinavian geology growth probably occurred in the eastern Much of Scandinavia lies on the Baltic shield, segment 1,70-1,65 Ga ago, but mostly in the sometimes called the Fennoscandia shield. western segment at 1,62-1,55 Ga. (Lundqvist The Baltic shield stretches from the western et al., 2011). part of Russia across Finland, Sweden and Norway and under the Baltic Sea (Fig. 1). The Baltic shield has been formed due to repeated accretion of crustal provinces onto the craton. The oldest part of the craton is in the northeast, where Archean rocks occur, and rocks are younger towards the southwest. This is known from age dating that shows that the oldest rocks are located in the northern parts of Norway, Russia and Finland (3,5-2,5 Ga), while the youngest are present in the southeastern parts of Norway and southwest Sweden (1 Ga). Additionally, paleomagnetic measurements show that the Baltic shield has moved across the Earth and endured continuous collisions over a very long time. (Lundqvist et al., 2011).

The Baltic shield is divided into five main units (Fig. 1); the Caledonian province, Transcandinavian Igneous Belt (TIB), Svecofennian province, Sveconorwegian province (also called Southwestern gneiss) and the Archean province. (Lundqvist et al., 2011).

Sveconorwegian province The Sveconorwegian province, where the sample site is located, is further divided into Figure 1. The Baltic shield with its primary areas, including The Caledonian (blue), the Transcandinavian two segments, the western (V) and the Igneous Belt (TIB) (red), Svecofennian province (orange), eastern (Ö) segment (Fig. 1). The western Sveconorwegian province (also called Southwestern segment stretches from the southern parts of gneiss) (white) and the Archean province (beige). The Norway to the Mylonite zone in the east. The Sveconorwegian province is divided in the west (V) eastern segment is located east of the segment and the east (Ö) segment. In between these segments the Mylonite zone is located (blue dashed line). Mylonite zone. Between the eastern segment In between the east segment and TIB, the Protogine zone and TIB lies the Protogine zone. The is located (green dashed line). (Lundqvist et al., 2011) Sveconorwegian province is also called the Black star shows the study site of this thesis. gneiss segment of southwest Sweden. This name is due to the dominant rock type,

Transcandinavian Igneous Belt This study concerns samples from two types The Transcandinavian Igneous Belt, TIB, of landforms; eskers and hummocks. Here, stretches from southeast Sweden north across we give a brief background on the genesis of the middle of Sweden and towards the west, them. where the rocks that occur in it underlie the Genesis of eskers Caledonian province, but is found again at the Compared to hummocks, the formation of surface in the northern parts of Norway. Granitoids of the ages 1,85 to 1,65 Ga are the eskers is fairly well understood. Eskers are dominating rock type, but there is also a large formed by deposition of sediment within large meltwater channels when the ice sheet amount of extrusive rock types, such as rhyolite as well as sub-volcanic porphyries. retreats (Benn & Evans, 2010). They are elongated ridges most-often formed (Lundqvist et al., 2011). perpendicular to the ice front and consist of Deglaciation of Småland glaciofluvial material (Benn & Evans, 2010). During the Quaternary Period, Scandinavia The meltwater channels can be subglacial, experienced several cold periods. During the englacial or supraglacial. The eskers can be Late Glacial Maximum (LGM), 23-21 ka ago, very long if the retreat of the glacier is normal, the Fennoscandian ice sheet (FIS) covered but if it is a surging glacier, or the material is Scandinavia from the northern parts of deposited into a subaqueous fan, the eskers Norway and Sweden down to the northern are shorter. In a study of Hedbrand and Åmark European lowland (Fig. 2) (Anjar et al., 2014). (1989), eskers were examined in an area south Following the LGM, the ice margin began its of the area studied in this thesis. They suggest retreat. According to Lundqvist & Wohlfarth that the landforms in that area are subglacial (2001), the southwest part of Sweden became eskers. In the study area and elsewhere in ice free at around 18-16 cal. ka BP. Småland, eskers can be found in valleys interpreted to be tunnel valleys (Gustaf Peterson, personal communication, 2016-03- 16). Such eskers are almost certainly formed subglacially. Such an interpretation applies to the Hörda site.

Genesis of hummocks The genesis of hummocks is, as earlier mentioned, debated. Johnson and Clayton (2003) present 11 different mechanisms for hummock formation. It is likely that Figure 2. Reconstruction of the LGM ice sheets, about 20 ka yr BP. (Svendsen, 2014) hummocks can be made in more than one way, so here it is not the case of choosing The ice retreat of the southwest coast of which mechanism is correct. Sweden is well documented thanks to the The most general theory is by supraglacial many end moraines (Lundqvist & Wohlfarth, mechanisms (Johnson and Clayton, 2003). The 2001). The deglaciation of the study site will shapes of these hummocks are typically be presented in the next chapter. chaotic, irregular forms and can be referred to Landform genesis as ‘collapse hummocks’ (Johnson and Clayton, 2003).

Andersson (1998) in a study close to Lake southern part of Sweden. The sampling site is Bolmen, 80km west of the study site, located north west of a small village called suggested a collapse origin for the hummocks Hörda, located between the cities of Värnamo, he studied and that supraglacial material had Växjö and Ljungby (Fig. 3). accumulated on top of the ice, in depressions. This resulted in an inversion of the landscape, with the source of the material as having been thrusted up from the bottom of the ice. The Värnamo landscape today appears as hills and knobs Växjö scattered across the landscape, each Ljungby representing a former depression on the ice surface (Andersson, 1998). Figure 3. Map over the study site. Värnamo, Ljungby and Växjö are the largest cities around the Another example of collapse hummocky study site Hörda, which is marked with a red star. formation is from a study in Wisconsin, USA, According to Dahlgren (2013) the area of by Johnson et al. (1995). The argument in this interest most likely has formed due to study is that the hummocks are formed from subglacial meltwater erosion forming a tunnel melt-out of basal debris-rich ice. The debris valley with hummocks along its bottom. . The rich ice melted and slowly left the material morphology of the area will be presented in a behind, creating hummocks consisting largely further section. of melt-out till.

An additional theory from Hambrey et al. Deglaciation of the study site (1997), is that the hummocks form due to Continuous moraines are not as evident in the thrusting in a polythermal, active glacier. The south Swedish highlands, where this study is material gets carried into an englacial or conducted, as they are on the west coast supraglacial setting, to get deposited when where they are also well dated. Deglaciation the ice melts. The landforms deposited will dates in the study area need to come from have the look of hills and knobs after each other sources. For example, Björck & other as a line. Håkansson (1982) dated varves from a lake The possibility of subglacially deposited and close to the city Växjö, named Trummen. By formed hummocks are also discussed by corrections from Lundqvist and Wohlfarth Johnson and Clayton (2003). Some of their (2001), the varves were dated to ca 13,9 ka yr suggestions are that ice blocks in a stagnant BP. Hörda is located not far to the west of this setting get pressed down into a deformable area, which makes this date relevant. bed. Another is that an active ice subglacially moulds hummocks. Furthermore, hummocks Anjar et al. (2014) has dated the deglaciation 10 are suggested to form at the study site due to of southern Sweden based on Be subglacial erosion, where the meltwater measurements from exposure dating. The streams were chaotic (Dahlgren, 2013). dating provides information about when the ice actually left the area. Anjar et al. (2014) made exposure dating at Lake Sjöanäs, which The study site: Hörda is located east of Hörda. The result shows that The study site is located in the county of the area became ice free at 15.2+/-0.8 to Kronoberg on the south Swedish highlands. 16.9+/-0.9 ka yr BP. Based on this, Hörda was The south Swedish highland is an area where likely deglaciated sometime after 17.8 ka yr BP the landscape has an elevation above 200 and before 14.6 ka yr BP. m.a.s.l. and is, as it is named, located in the

Local bedrock geology the Protogine zone, metamorphosed and even The bedrock of the study area belongs to the migmatized rocks are common, together with eastern segment in the Sveconorwegian younger mafic intrusions, which are mostly province (Fig. 1). The area is dominated by metamorphosed as well. East of the Protogine felsic metamorphic rocks with the ages of 1,78 zone and east of the sample site lies TIB. Here to 1,65 Ga. There is also abundant granitoid is older bedrock containing mostly granitoids gneiss with a porphyric texture, due to large and porphyries, but also some sedimentary veins of K-feldspar. Hörda is located rocks (Fig. 4). There are also sedimentary southwest of the Protogine zone (Fig. 1). In rocks north of Hörda in the area of Jönköping (Lundqvist et al., 2011).

Figure 4. Local bedrock map. Black star for location of the study site. Modified after Bergman et al. (2012). Local topography and geomorphology (2013), a profile of the valley shows that both The sample site nearby Hörda is located in a of its ends slope downhill, which indicates that valley where the surrounding uplands contain the whole valley itself most likely be made streamlined landforms. The bottom of the from subglacial erosion rather than by surface valley contains glaciofluvial deposits as well as streams. There are also, as mentioned before, irregular hummocks. This valley is interpreted eskers overlying hummocks in the area as a tunnel valley, although it differs due to (Dahlgren, 2013). An overview of the the irregular bottom compared to others landforms in the area can be seen in the LiDAR tunnel valleys that commonly have a flat image (Fig. 5). bottom. Measurements of drumlins in the vicinity of the tunnel valley indicate an ice flow from N 25 E. According to Dahlgren

Glaciofluvial material Study area

Hörda

Figure 5. LiDAR image covering the study area. Image to the left showing an overview of the landscape and the Hörda valley, with higher plateaus on each side. A few drumlins are identified with the yellow arrows, which indicate the ice-flow direction. The right image is a closer look of the valley and the study area in the red square. The hills and knobs are hummocks, while the green markings are glaciofluvial material, mostly eskers.

Methodology stationed in Gothenburg. First, an overview over what kind of rock types there were to Field distinguish among was made, and then rock- type classes were defined with help from local To select sampling sites, a LiDAR image with a bedrock geology maps by SGU (Wik et al., hillshade cover was developed, showing 2006; 2007). A hand lens, magnetic pen and a locations of potential road cuts or excavations needle was used during classification. If the in the glacial landforms. Sites where Gustaf lithology was not possible to determine by Peterson had already made excavations were ocular analysis, the clasts where split with a also utilized. rock hammer to get a fresh surface. A few In total, five samples from eskers and five clasts were sawed with a rock saw if they were samples from hummocks were collected, difficult to hammer or if they were a good where each sample consisted of 100 clasts type example for photo documentation. with a phi size of -5 to -6 (32 to 64 mm). The Form analysis was made measuring the long clasts were collected randomly by laying out a A-, intermediate B- and short C-axes with a measuring tape in front of an exposure, calliper and plotted in tri-plots according to selecting a stone every 50 cm and placing Sneed & Folk (1958) and Benn & Ballantyne them in a plastic bag tagged HH01-HH05 for (1993). The measurement results were ‘Hörda Hummock’ and HE01-HE05 for ‘Hörda entered individually into a Microsoft Excel Esker’ (Fig. 6). All samples were taken to the sheet designed by Graham & Midgley (2000). Department of Earth Sciences (University of The diagrams were plotted including a line for Gothenburg) for analysis. C40 ratio, which shows the percentage of the pebbles in the sample that had a ratio between the c/a axis ≤ 0,4.

The roundness was estimated visually using the Powers scale (Powers, 1953) where the different classes where Very Angular (VA), Angular (A), Sub Angular (SA), Sub Rounded (SR), Rounded (R) and Very Rounded (VR). The RA-index was determined, which is the total percentage of angular and sub-angular clasts.

Figure 6. Field sampling from hummock landform. All the results were compiled and processed in Photo: Martin Thor, 2016. Microsoft Excel. C40 ratio and RA-index for Laboratory each sample was also calculated in Excel and In order to be able to define the rock type of then plotted in a co-variance plot according to each clast, the clay and lichen were washed Lukas et al. (2013). and scrubbed with water and a fibre brush. Statistics Thereafter they were placed in labelled boxes. The lithology of the clasts was determined A statistical Chi-square test was performed on using Quartz, Alkali feldspar, Plagioclase, the lithology to see if there were a significance Feldspathoid (QAPF)–diagrams together with difference between the results from the help from Lena Lundquist, Thomas Eliasson hummocks and the eskers, with a significance and Ulf Bergström, SGU bedrock geologists level of P < 0,05.

Results

The analysis of all the clasts will be presented Table 1. Rock type classification of the esker and in different sections in the order that follows; hummock samples. rock type classification, rock description, form analysis and roundness. Rock type Esker Hummock Amphibolite 5 5 Rock type classification Breccia 1 1 The total amount of clasts is 500 from the Diabase 1 1 Gabbro 16 22 eskers and 501 from the hummocks. The rock Granitoid 43 60 type classification results are presented in Granitoid gneiss 324 345 Table 1. The most abundant rock type in both Mylonite 4 1 landforms is granitoid gneiss. The eskers, as Pegmatite 9 8 well as the hummocks, contain porphyric Porphyry 2 4 granitoid gneisses, but the higher amount is Porphyric granitoid found in the eskers. Mafic rocks, such as gneiss 79 29 amphibolite, gabbro and diabase, are also Rhyolite 1 0 present in the sediment from both landforms. Quartzite 1 0 The presence of sandstone is greater in the Sandstone 10 18 hummocks, and only one clast of breccia has TIB-granitoid 4 6 Ultramafic 0 1 been observed in each landform. One single TOTAL 500 501 clast of rhyolite was found in the esker, as well as one ultramafic clast in the hummocks. Porphyries are rare but present in both landforms.

The statistical test gave, with the significance level of P ≤ 0,05, a P value of 4*10-5, which means that there is a significant difference in the lithology between the samples in the eskers and the hummocks (Table 2).

Table 2. The Chi-square test results, where the observed values are at the top, and the calculated expected values are at the bottom. The P value is presented at the very bottom, and is lower than the set significance level of 0,05, which indicates that there is a difference of rock types between the eskers and the hummocks.

The combination of the lithological result for contain a higher content, 15,8%, compared to both eskers (HE) and hummocks (HH) are the hummocks, 5,8%. The difference in the presented in Figure 7. As mentioned, granitoid amount of sandstone is reversed, where the gneiss is the most abundant rock type in both eskers contain only 2,0% compared with 3,6% eskers and hummocks. The largest difference in the hummocks. between the landforms is the amount of the porphyric granitoid gneiss, where the eskers

Figure 7. Diagram of the rock type classification in the eskers (HE) and the hummocks (HH). Each column is also shown in percent, for comparison. It clearly shows that the granitoid gneiss is the dominant rock type in both landforms. There are many granitoid and porphyric granitoid gneiss clasts in both eskers and hummocks. A distinct difference is present between the amount of porphyric granitoid gneiss, where the eskers contain 15,8% compared to the hummocks on 5,8%. There is also see a difference in the amount of sandstones, where eskers have only 2,0% compared to 3,6% in the hummocks.

Rock descriptions Gabbro In this section, we give a brief description of The gabbro samples vary from a bright colour the rock types we identified. containing high concentrations of plagioclase, to the dark samples containing mostly Amphibolite pyroxene (Fig. 10). They are medium to coarse The amphibolites have a dark grey to black grained. Most of them are metamorphosed colour. One of them was heavily folded and contains biotite. Two clasts have an (Fig. 8). They consist mostly of amphiboles, ophitic texture. but also plagioclase and biotite. A few samples appeared to have contained small garnets.

Figure 10. Metagabbro. From sample HH05.

Ultramafic Figure 8. Amphibolite. From sample HH04. The one sample of ultramafic rock is heavy, Diabase contains magnetic minerals and has a black The diabase has an ophitic texture and is fine colour (Fig. 11). to medium grained. It mostly contains plagioclase and pyroxene (Fig. 9).

Figure 11. Ultramafic. From sample HH03.

Figure 9. Diabase. From sample HH05.

Breccia Granitoid The breccia from sample HE02 (Fig. 12), seems The granitoids differs from fine to coarse to contain two rock types. The outermost rock grained, red grey to grey red, even to uneven type has a fine grained, red matrix with coarse grained. Many samples are rich in quartz and clasts of brighter minerals, which could K-feldspar. It was difficult to observe foliation possibly be plagioclase. The innermost is a in many of the samples, because of the dark, fine grained rock. absence of dark minerals. This made it hard to determine if they would be classified as “Granitoid” or “Granitoid gneiss”.

Approximately 10 clasts of the granitoids have zones of dark minerals, mostly pyroxene but also biotite (Fig. 14). They differ in grain size distribution from medium to coarse, where the zones of darker minerals are fine to medium grained. They have a colour of red- grey, are estimated as quartz syenites and display no foliation.

Figure 12. Breccia. From sample HE02.

The breccia from sample HH03 (Fig. 13) has, like Figure 12, the fine grained red matrix with brighter, possibly plagioclase, coarse clasts in it.

Figure 14. Quartz syenite. From sample HE03.

Figure 13. Breccia. From sample HH03.

Two of the granitoid clasts have the look of Mylonite Figure 15. They have a bright colour The mylonites are fine grained, compact and containing abundant K-feldspar as well as highly foliated. Because of the heavy plagioclase, and have medium to coarse sized deformation, the original rock type is difficult to distinguish (Fig. 17). grains.

Figure 17. Mylonite. From sample HE01.

Porphyry Figure 15. Granitoid. From sample HH02. The porphyry samples vary a lot. All of them Granitoid gneiss have a fine matrix with large clasts inside. There is a large distribution of composition Figure 18 displays phenocrysts of albite. The and structure of the granitoid gneisses. They sample in Figure 19 consists of dark grey vary from quartz syenite composition to minerals with larger darker areas and granodioritic, some are possible tonalitic, but plagioclase clasts. The matrix in Figure 20 very difficult to determine solely based on consists mostly of quartz and has larger clasts ocular analysis. The grain size range of fine to of mostly plagioclase. medium appears to be the most abundant.

One example of variation is this quartz monzodiorite from sample HH05 (Fig. 16), which contains lots of albite and therefore has a bright colour.

Figure 18. Porphyry. From sample HH03.

Figure 16. Quartz monzodiorite. From sample HH05.

Rhyolite The only sample with a rhyolitic composition that was found (Fig. 22) is fine grained and has a red-brown colour; therefore, it is likely that the amount of K-feldspar is high.

Figure 19. Porphyry. From sample HH04.

Figure 22. Rhyolite. From sample HE01.

Sandstone There are two different types of sandstones (Fig. 23 and Fig. 24). They have a high content of quartz and very few dark minerals. They vary from bright beige, yellowish to darker, greenish colour. The bright ones (Fig. 23) are

Figure 20. Porphyry. From sample HE01. slightly frail and can be scratched with a needle, and some even possible to break with Porphyric granitoid gneiss your hands. They have a grain size of fine to The porphyric granitoid gneiss (Fig. 21) medium and contain almost only quartz. The consists of a granitic composition, with large darker, greenish sandstones (Fig. 24) are more veins of red K-feldspar. It is classified as compact and very fine grained. They are also porphyric because of the veins, which, before heavier than the bright ones. There was only it became metamorphosed, must have had a two of this type found. porphyric structure.

Figure 21. Porphyric granitoid gneiss. From sample HE03. Figure 23. Sandstone. From sample HH05.

Figure 24. Sandstone. From sample HH02.

TIB-granite The granites named TIB-granites are fine grained and have a red to grey red colour. The clasts mineralogical compositions are dominated by K-feldspar, have a varying content of quartz and are poor in plagioclase. Most of them were discerned as quartz syenites. One of the samples had a bluish colour on the quartz crystals.

Form analysis formed as blocks, not elongates or plates as The results of the form analysis are shown in the left and right corner represents. The RA- the tri-plots in Figure 25 and 27. One black indices are almost zero for all the esker point indicates one clast, so there are 100 samples, which indicate that the amounts of points in each diagram. The form analysis of clasts with angularity are low. In Figure 26 the the esker samples shows that most of the roundness result for the esker samples is samples plot in the upper part of the tri-plots presented, where the most abundant class is (Fig. 25). Therefore, the C40 value is low, Sub-rounded (SR), followed by Sub-angular which means that most of the clasts are (SA).

Figure 25. Form analysis of the esker samples. Showing low ratio of both C40 ratio and RA-Index, which means that the angularity of the clasts is low, and the most abundant form is blocks, not elongates or plates.

Figure 26. Roundness results of the esker samples with the classification of Very Angular (VA), Angular (A), Sub-angular (SA), Sub-rounded (SR), Rounded (R) and Very Rounded (VR). The most abundant classification is Sub-rounded, thereafter Sub- angular.

The form analysis of the hummock samples 0.12-0.22, which indicate that the spreading of plot, like the esker samples, in the top section forms is higher in the hummocks, but not of the diagrams (Fig. 27). This means that distinctly from the esker samples. The RA- most of them also are of the form of a block Index varies between 0-0.31, which is low, but rather than a platy or an elongated form, higher than the eskers. The dominated which also can be seen in the C40 values. The classification of roundness in the hummock C40 values are a little bit higher in the samples is Sub-angular (SA), followed by Sub- hummock than in the esker samples, between rounded (SR) (Fig. 28).

Figure 27. Form analysis of the hummock samples. Showing higher than the esker results, but still low ratio of both C40 ratio and RA-Index, which means that the most abundant clast form is blocks, not elongates or plates.

Figure 28. Roundness results of the hummock samples with the classification of Very Angular (VA), Angular (A), Sub-angular (SA), Sub-rounded (SR), Rounded (R) and Very Rounded (VR). The most abundant classification is Sub-angular, thereafter Sub-rounded.

The co-variance plot (Fig. 29) presents a amount of very angular as well as angular comparison between the RA-Index and the clasts and that most of them has a blocky C40 ratio of both hummock samples and esker shape. Two of the hummock samples have a samples. Most of the samples plot in the higher amount of angular and very angular lower left part, which means that they have a clasts, and plot therefore higher on the RA- low RA-Index and C40 ratio and therefore, low Index axis.

Figure 29. Co-variance plot of the RA-Index and the C40 ratio between the hummock and esker samples. Both the esker and hummock samples plot in the lower left corner but the eskers plot directly on the x-axis. The hummock samples varies more, but plot clearly in the lower left corner.

amphibolite facies including garnets, and still retain their original gabbroic texture and Discussion composition in the centre. Therefore, Since the statistical test yielded a significant determining provenance can be extremely difference considering the rock types of the difficult. landforms, it indicates that there could be a According to Wik et al. (2006; 2007), there are difference in provenance as well as transport several small breccia occurrences in the TIB- mechanisms. province. However, since it is such a small Provenance study percent of the total, its presence at Hörda can be a coincidence, or indicate that this rock The estimations of clasts lithology, based on type was transported during an earlier ice inspection of the bedrock maps from SGU flow. Nonetheless, the most likely source of (Wik et al., 2006; 2007) and discussion the breccias is from the TIB province. together with the SGU geologists, yielded a local bedrock origin for all samples. This The granitoids are most similar to the ones interpretation is made for both the hummocks described in the eastern segment of the and the eskers, even though the statistical test Sveconorwegian province, but also show showed that the lithologies differed similarities to the granitoids from TIB significantly. The local origin implies local (Lundqvist et al., 2011). Aside from that, there erosion and transport (Puranen, 1988), almost are two types of granitoids that differ from certainly subglacial. This hypothesis is the others. One is shown in Figure 14, which is supported in that in the local bedrock, the determined in collaboration with SGU, to be a most abundant is the granitoid gneisses (Wik quartz syenite from Vaggeryd. Vaggeryd is et al., 2006; 2007). The granitoid gneiss is the located north of the sampling site (Fig. 30). most abundant rock type in the area (Wik et Most clasts of this type were found in the al., 2006; 2007), and also in the samples, esker samples, but it was also present in the which implies local provenance. But, the hummock samples. This indicates that it is granitoid gneiss is hard and resistant to possible that in an earlier time, a glacier erosion during transport, which could play an moved from the north or northwest, eroded important role. However, there are large the granitoids, and transported them towards distributions of different rock types in both the southeast only to later get picked up by the eskers and hummocks, and according to the latest glacier from the northeast, Gillberg (1968), eskers often consist of a large transporting them to Hörda. distribution of different rock types, which agrees with the result in this study. The other peculiar granitoid is presented in Figure 15, which is a typical Filipstad-type The provenance of the mafic rock types, such granitoid (Personal communication, Ulf as amphibolite, diabase, gabbro and the Bergstöm, 2016-05-04). The Filipstad granitoid ultramafic clast, is very difficult to precisely is characterized by coarse grains, and has its locate. The reason for this is due to the large origin in the TIB-province (Wik et al., 2006; spatial distribution of small mafic outcrops in 2007). These are found in the hummock Sweden. According to Wik et al. (2006; 2007), samples, which could indicate that it is the rock bodies can differ substantially within transported from northeast, which would themselves. With this in mind, they can be correlate with the latest ice flow direction highly metamorphosed near the edges, e.g. (Dahlgren, 2013).

The distinction between classifying a clast as TIB, where the textures can vary a lot (Wik et granitoid gneiss or mylonite was difficult in al., 2006; 2007). The fourth porphyry that was some cases. The few clasts that we classified found (Fig. 18) is concluded to be as mylonite are highly deformed, and, because characteristic of porphyries from Småland and of its recrystallized mineralogy, it was difficult also common in the TIB province (Lundqvist et to tell their original rock type. Furthermore, al., 2011). Because of the large area that TIB there are several localities in both the covers (Fig. 1), it is hard to distinguish if its Protogine zone and Mylonite zone that are provenance is in the southern or northern characteristic for this grade of deformation part. However, since it is a typical porphyry (Wik et al., 2006; 2007), which makes it from Småland (Lundqvist et al., 2011), its possible that they may be derived from either provenance is most likely not a large distance of those zones. Because of the distance (Wik away from Hörda. et al., 2006; 2007), and the direction of the latest ice flow (Dahlgren, 2013), it is more One important rock type for the study is the likely that the mylonites provenance is in the porphyric granitoid gneiss. There are abundant porphyric granitoid gneisses Protogine zone rather than the Mylonite zone. throughout the Sveconorwegian province, but To determine a provenance of the pegmatites the one identified in this study seems to be a is not possible in this study because of the typical rock type in the area surrounding extent and spatial distribution of pegmatite Barnarp (Wik et al., 2006; 2007). Barnarp is veins (Wik et al., 2006; 2007). located approximately 80km north of the sample site, close to Jönköping (Fig. 30). The Porphyries occur as clasts in both esker and amount of this type of gneiss is distinctly hummock samples and could be very larger in the eskers compared to the important for the provenance study. In hummocks. Furthermore, this, like the corporation with SGU, the dark porphyry syenites from Vaggeryd and the porphyry (Fig. 19), which is collected from a hummock, from Habo, indicates a northern provenance is suggested to originate close to Habo and implies transport by earlier glaciers with a (Fig. 30). This implies that it has been direction from north or northwest and later transported approximately 110km from north, deposition in Hörda. almost northwest. The porphyry has a rounded shape, which could indicate a The rhyolite was found in an esker and has subglacial or fluvial transport mechanism at most likely been transported from the TIB- some point during transport (Lukas et al., province (Wik et al., 2006; 2007). It is not 2013). This influence of the clast shapes will possible in this study to determine from be discussed further on in next section. where, except that it is not likely from the Additionally, the transport from the north Sveconorwegian province because of the correlates with the syenites from Vaggeryd, higher amount of rhyolite in TIB compared to and therefore also indicates an earlier ice flow the Sveconorwegian province (Wik et al., direction from north or even possible 2006; 2007). northwest. Lastly, explanation of the provenance of the The other porphyries (Fig. 20) have been sandstones is difficult. The two different types suggested to originate from the TIB-province seem to have two or three possible origins. (Wik et al., 2006; 2007). This interpretation is The less compact, brighter one based on the high amount of porphyries in the (Fig. 23) is similar to the ones that are found in

22 the Visingsö group, in the southern part of transported from the northeast. Comparing lake Vättern, close to the city Jönköping the location of Almesåkra with the latest ice- (Fig. 30). It is located approximately 90km flow direction, it correlates well. north of Hörda. The hummocks contain several clasts of this type of sandstone. Due to this provenance study it seems like, and despite the slight difference in the Furthermore, several lithologies mentioned statistical test, the sediment in the landforms above also indicate provenance from the north, implying an earlier ice flow from the has been eroded from the local sediment or north or northwest. But the sandstone could bedrock (Wik et al., 2006; 2007). Furthermore, the debris has likely been transported before also have a similar composition as the Cambrian sandstones in Kinnekulle and the eskers and hummocks where formed Billingen (Johansson et al., 1943). Kinnekulle is during an earlier glaciation. According to the provenance study, we suggest that a large located approximately 200km northwest from Hörda. Because of the distance and without amount of the analysed clasts have been further chemical analysis, it is more likely that transported during an earlier ice flow that had the direction from north, possible from the sandstones have their provenance in the northwest, and only during the latest episode Visingsö group (Lukas et al., 2013). were the clasts deposited at in Hörda. It could However, the more compact, darker and finer also be that several ice flows are inbedded in grained sandstone (Fig. 24) is, according to the clast histories; it is just that the measured SGU, similar to the Almesåkra group (Wik et ice flow on the drumlins in the Hörda valley (N al., 2006; 2007) located to the east of the 25 E) is the latest. Protogine zone. If so, these clasts are

Jönköping

Figure 30. Local bedrock map. White star for study site. Black solid arrow showing the latest ice flow direction (N 25 E) (Dahlgren, 2013), black dashed arrow showing the suggested earlier ice flow direction from north, north west. Names for the interpreted locations of provenance. Modified after Bergman et al. (2012).

Form analysis bed of till. The material transported by The form analysis can distinctly show that englacial or supraglacial mechanism gets both the esker and hummock samples have transported faster and are often deposited in experienced glacial and/or fluvial transport the top part of the till bed (Puranen, 1988). because of their loss of angular and very This implies a variation in the vertical direction angular shapes. The tri-plots (Fig. 25 and Fig. of the landform, which could have an 27) show as well the abundance of a blocky influence of the material in this thesis. On the form of the clasts rather than elongated or other hand, since our result does not only platy, which indicates that their edges have include clasts from local erosion, but also been smoothed out. The higher amount of further travelled lithologies, the results are subrounded and subangular in the eskers and considered to be representable. Our study hummocks respectively could suggest that the could however be improved by taking notice esker samples have travelled further, with to the vertical variation, together with the higher energy, or reworked from an earlier random selection while collecting the samples. glacier. In this study, the small difference of the esker and hummock samples will be seen as a similarity instead. This is based due to the comparison between this paper RA/C40 plot (Fig. 29) and a plot made by Lukas et al. (2013). The comparison is presented in Figure 31, where the plot from Lucas et al. (2013) has been modified for this study. It shows that both the esker and hummock samples from this study are similar to the subglacial deposits summarized by Lukas et al., (2013).

The choice of phi size (-5 to -6) of the collected Hummock Esker clasts can be discussed further. It can be Figure 31. Modified co-variance plot originally from inadequate since the lithology of the clasts has Lukas et al. (2013). Shows the RA-Index and C40 ratio a major influence on the strength against from different glacial deposits, which further are erosion. However, since the distribution of interpreted as either fluvial distal, subglacial or supra/extraglacial. The blue circle is where the esker different rock types was high, we determined samples plot in this thesis, and the orange circles it was representable. represents the hummock samples.

Furthermore, the method of sampling can be Hummock formation discussed. Because of practical reasons, the The fact that one of the hummocks is overlain measuring tape which was used to get a by an esker supports the interpretation that random selection was mostly put along the the hummocks in the valley are formed by horizontal direction of the excavation of subglacial processes under the glacier. This is interest. According to Puranen (1988), the strengthened by Dahlgren (2013) who provenance of the till can vary a lot in a interpreted that an esker further down in the vertical direction of a section. The reason for Hörda valley as a typical esker that forms by this is that the material that gets transported subglacial processes. Dahlgren (2013) also subglacially travels slowly, are often eroded interpreted that there are subglacial deposits locally, and deposited at the bottom of the along the whole valley. However, typical

24 tunnel valleys are often assumed to have a flat and suggests that the samples experienced or channel-shaped bottom, but this one at little further modification when they were Hörda has an irregular, hummocky one (Fig. carried in esker tunnels. The common 5). Dahlgren (2013) suggested that water flow provenance of the hummock and esker was chaotic to form the hummocks in the samples supports the interpretation that tunnel valley. Despite the difficulty involved in erosion of the hummocks in the tunnel-valley explaining how irregular hummocks can be the bottom was followed afterwards by esker product of fluvial erosion, the geomorphic formation and explains why they both have context strongly suggests that these similar provenance. hummocks are erosional and subglacial in origin. Acknowledgements If the hummocks were formed by subglacial We are grateful for the invaluable rock meltwater erosion of basal till, and the eskers classification support from Lena Lundquist, on top of them during deglaciation, it is not Thomas Eliasson and Ulf Bergström at SGU. surprising that they consist of local sediment. The quality of this thesis would not be as high However, because many clasts show a if it were not for your help. We would also like provenance from the north (rather than N 25 to thank our supervisor Mark Johnson for E), it is likely that much of the material was great supervision, guidance and coaching eroded and reworked from earlier glaciers, during the whole project, as well Gustaf deposited in the till and then picked up by the Peterson for all help during the field sampling latest ice flow to get deposited as these but also during the project. Major thanks to hummocks and eskers. Samples like gneiss Andreas Karlsson for all help during the rock from Barnarp, porphyry from Habo, sandstone classification and support along the way. from Visingsö and syenite from Vaggeryd (Fig. Lastly, big acknowledgements to John 30) suggests that an earlier, or several, ice Eliasson, Ingrid Jillerö, Amie Remberg, Josefine flow directions came from north or northwest, Johansson and Linnea Johansson for reviewing and later picked up and as the latest, the rapport and helping us improve it. deposited in Hörda.

Conclusions This thesis supports the idea that the hummocks in the valley near Hörda are formed by subglacial meltwater erosion. The esker clasts likely were derived from the till layer that was shaped (eroded) into the hummocks. Statistical test shows a significant difference in the rock type distribution between the hummocks and the eskers, but, both of the landforms mostly contained local eroded bedrock. Form analysis of the examined samples shows them to be similar, both sub-rounded to sub-angular, which strengthens the theory of subglacial formation

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Appendices

Appendix 1. Total result of the rock type classification of the esker samples.

Appendix 2. Total result of the rock type classification for the hummock samples.