UNIVERSITY OF GOTHENBURG
Department of Earth Sciences
Geovetarcentrum/Earth Science Centre
PROVENANCE OF PEBBLE
CLASTS IN HUMMOCKS IN
THE EASTERN SOUTH SWEDISH
HIGHLANDS NEAR GULLASKRUV
Martin Thor
Karin Grodzinsky
ISSN 1400-3821
Mailing address
Geovetarcentrum
S 405 30 Göteborg
Address
Geovetarcentrum
Guldhedsgatan 5A
B931
Bachelor of Science thesis
Göteborg 2016
Telephone
031-786 19 56
Telefax
031-786 19 86
Geovetarcentrum
Göteborg University
S-405 30 Göteborg
SWEDEN
Table of contents
Introduction ........................................................................................................................................... 3
Aim of study ....................................................................................................................................... 3
Research question .............................................................................................................................. 3
Study site & geology ............................................................................................................................... 3
Bedrock geology ................................................................................................................................. 3
Deglaciation of southern Sweden ...................................................................................................... 7
Acquisition and transport of glacial debris ......................................................................................... 7
Hummocks ......................................................................................................................................... 8
Hummocks in Gullaskruv .................................................................................................................... 9
Esker formation .................................................................................................................................. 9
Methodology ........................................................................................................................................ 10
Field work ......................................................................................................................................... 10
Lab work ........................................................................................................................................... 10
Results .................................................................................................................................................. 12
Rock descriptions ............................................................................................................................. 12
Provenance studies .......................................................................................................................... 14
CHI2 test ........................................................................................................................................... 14
Provenance markers......................................................................................................................... 14
Shape analysis .................................................................................................................................. 15
Discussion............................................................................................................................................. 17
Provenance study ............................................................................................................................. 17
CHI2-test .......................................................................................................................................... 18
Difference between eskers and hummocks ..................................................................................... 18
Shape analysis .................................................................................................................................. 20
Hummock formation ........................................................................................................................ 20
Conclusions .......................................................................................................................................... 21
Further studies ..................................................................................................................................... 21
Acknowledgements .............................................................................................................................. 22
References ........................................................................................................................................... 22
Appendices ........................................................................................................................................... 24
1
Abstract
Hummocks occur in many forms in southern Sweden. However, the genesis of these landforms has not
fully been understood. The new LiDAR dataset covering Sweden is a new source of information with
large possibilities for giving further insight on the genesis of many glacial landforms, including
hummocks. Provenance studies of sediment in hummocks on the south Swedish highlands, near
Gullaskruv, suggest a very local provenance where granites, rhyolites and porphyries from the
Transscandinavian Igneous Belt predominate. Some of the furthest transported clasts are inferred to
come from the Vetlanda group and nearby basalt formations, 70 km away. Shape analysis on clasts
from the hummocks imply that the sediment composing the hummocks is similar to sediment of known
subglacial origin. Lithological provenance studies and shape analysis suggests that the clasts have been
locally eroded, entrained and deposited with a maximum transportation distance of 70 km. The studied
samples have been compared statistically and lithologically to samples with the same grain size from
eskers in order to strengthen a possible transportation mechanism. The difference that was found
between the hummocks and the eskers can probably be traced back to that the sediment in the two
types of landforms had different transport routes and distances.
Sammanfattning
Hummocks förekommer i många former i södra Sverige. Men bildningen av dessa landformer har inte
helt förståtts. Den nya LiDAR-datan över Sverige är en ny källa till information med stora möjligheter
att ge ytterligare insikt om uppkomsten av många glaciala landformer, bland annat hummocks.
Provenansstudier av sediment från hummocks på Sydsvenska höglandet, nära Gullaskruv, föreslår en
mycket lokal härkomst där graniter, ryoliter och porfyrer från Transskandinaviska magmatiska bältet
dominerar. Några av de längst transporterade klasterna kan härledas att komma från Vetlandagruppen
och närliggande basaltformationer, 70 km bort. Shape analys på klaster från dessa hummocks antyder
att moränen som utgör dessa landformer liknar sediment av känt subglacialt ursprung. Litologiska
provenansstudier och Shape analys tyder på att dessa klaster har blivit lokalt eroderade,
transporterade och avsatta med en maximal transportsträcka på 70 km. De studerade proverna har
blivit jämförda statistiskt och litologiskt med prover med samma kornstorlek från rullstensåsar för att
stärka en möjlig transportmekanism. Skillnaden som påträffats mellan hummocksen och
rullstensåsarna kan troligtvis spåras till att sedimentet i de två landformerna hade olika transportvägar
och transportavstånd.
Keywords: hummocky terrain, esker, South Swedish Highlands, provenance, glacial geomorphology,
LIDAR
2
Research question
Introduction
What is the provenance of the sediment in
these “fish scale” hummocks?
Hummocks and associated landforms occur
widely on the south Swedish highlands. They
are a type of glacial landform which are
enigmatic and widely discussed. Many
different theories have been presented
regarding their genesis, and it is likely that
similar forms can be made by more than one
process. To simplify, there are a few different
theories on their formation: One theory
suggests that debris-rich ice is thrusted at the
top of the glacier and later on deposited as hills
when the glacier melts (Johnson & Clayton,
2003). Another where they are interpreted as
supraglacial and, or subglacial deposits, where
till is melted out from a stagnant ice (Johnson
et al., 1995). Still another is one where the
hummocks are interpreted to form when
subglacial debris is thrusted to a en- or
supraglacial position. This debris is then
collapsed down when the ice melts, in an active
ice setting, creating hummocks (Hambrey et
al., 1997). Previously, the hummocks in the
south Swedish highlands have been considered
stagnant ice deposits, for example by
Andersson (1998), Möller (2010) and Möller &
Dowling (2015). The New National Elevation
Model (NNH) consists of LiDAR (Light Detection
and Ranging) data with complete coverage
over southern Sweden. This data is utilized by
Gustaf Peterson, PhD student at Gothenburg
University and SGU (Swedish Geological
Survey), with the purpose of shedding light on
how these hummocks are formed. The LiDAR
data has revealed hummocks in many
previously unknown forms, whose origin and
genesis are to be investigated.
Is there a significant statistical difference
between the clasts in the studied hummocks
and eskers in the area? If so, can this help in
determining the genesis of the hummocks?
These two groups of samples will be examined
separately and compared to each other in
order to establish whether or not a significant
statistical difference can be found between
them.
Study site & geology
The area studied in this thesis lies on the south
Swedish highlands in Småland, Kalmar län,
approximately halfway between Växjö and
Kalmar in Nybro municipality (Fig. 1). The study
area lies within an area bounded by
56°54'33.5"N, 15°39'17.8"E and 56°51'15.3"N,
15°40'49.1"E. Sampling was made at three
hummocks and three eskers, in the study area
which is shown in Fig. 1. The studied hummocks
are highlighted in Fig. 2.
Figure 1. Map over southern Sweden. The black dot marks
the study area in this thesis.
Aim of study
Bedrock geology
This thesis will examine if lithological
provenance studies and clast shape analysis
can help provide insight into and help identify
the genesis of the “fish scale” (a working term)
hummocks studied by Peterson at a site called
Gullaskruv, se Fig. 1.
The descriptions of the bedrock in the study
area will be focused on western Småland, predominantly the Jönköping province and parts
of Kronoberg and Kalmar provinces (Fig. 3).
3
The bedrock in the study area is part of the
Transscandinavian Igneous Belt (TIB), which
started to form in the Paleoproterozoic era
between 1,8 -1,9Ga BP. It was formed when the
Eurasian plate collided with the North
American plate (Högdahl et al, 2004). It is one
of the larger structural units that constitute the
Baltic shield, the large craton that holds
Scandinavia, Finland and the Baltic countries.
The TIB reaches north from Småland up
through Värmland and Dalarna, with a few
occurrences in the Scandinavian mountains,
see Fig. 4.
Figure 2. LiDAR Hillshade DEM over the study area. The studied hummocks are highlighted by the red square. The eskers are
highlighted with blue lines.
4
Figure 3. Map over the study area showing the different bedrock classes found in the studied
hummocks. The black star marks the location of the study area. Modified after Bergman et al.
(2012).
5
commonly gray to reddish gray. The granites
and rhyolites in this area often carry
phenocrysts and are porphyritic in their texture
(Wik et al., 2007). The rhyolites in the area are
commonly slightly younger than the granitic
rocks, but often dated to 1,8 Ga (Lundqvist et
al., 2011). Porphyry is often considered a
subvolcanic rock and often occur in contact
zones between intrusive and extrusive rocks.
Their grain size can often be somewhere
between the fine grained granites and the
rhyolites
(Thomas
Eliasson,
personal
communication)
Close to the Protogine zone, which separates
the Eastern segment in the west from the TIB
in the east (Fig. 4), rocks are commonly
deformed and metamorphosed (Wik et al.,
2006). These deformed rocks also occur in the
Oskarshamn-Jönköping belt (OJB), outside of
Jönköping (Lundqvist et al., 2011).
According to the Wik et al. (2006) there are
several bodies of mafic extrusive rock scattered
across the region. These bodies occur mostly in
the Jönköping province, close to the Vetlanda
and Almesåkra formations (Vetlanda light blue
and Almesåkra dark blue in Fig. 3). A basalt
composition is most common, but there is
some andesite occurring as well. There are also
some areas with intrusive gabbroic rocks
scattered across the TIB. These rocks
commonly show signs of magma mixing
structures, resulting from mixing with the
granitoid country rock. Mafic hypabyssal
varieties also occur, where diabase (dolerite) is
the most common. They can predominantly be
found in the Almesåkra formation where the
mafic rocks are slightly younger than the
sedimentary rock bodies they surround.
However, several large dikes and sills are
scattered across the region in long north-south
running dikes across the landscape.
Figure 4. Map over the Baltic shield, where the
Transscandinavian igneous belt is highlighted in red
(Lundqvist et al., 2011).
The bedrock is characterized by intrusive and
extrusive felsic rocks belonging to the TIB 1
stadium (1,81-1,76 Ga) (Lundqvist et al., 2011).
The intrusive rocks are of granitic composition
and are, in some areas, very fine grained,
because they were recrystallized when
extrusive rocks intruded in immediate
proximity to the granites (Thomas Eliasson,
personal communication) and in areas with
contact to the porphyries (Lundqvist et al.,
2011). These granites (unit 108 in Fig. 3) are
mapped as red to gray-red, fine to finely
medium grained granite (Wik et al., 2007). In
other areas medium grained syenitic granite is
common with larger grains of quartz and
potassium feldspar, and SGU has mapped
these rocks as red to gray red, medium to
coarse granites. The extrusive rocks are
prominently of rhyolitic composition, with
some cases where dacitic rocks occur. The
rhyolites are commonly red to pink in color,
with a very fine grained matrix. The dacites are
There are several stratigraphic units that are
composed of sedimentary rock in the TIB. The
three largest are the Visingsö Group (approx.
800-700 Ma), Almesåkra Group (at least 970
Ma) and Vetlanda Group (1830-1800 Ma)
6
(Lundqvist et al., 2011). The rocks from the
Visingsö Group (dashed yellow area, unit 14 in
Fig. 3) are commonly fine grained and quartz
rich. They are not as compressed and hard as
other sedimentary rocks in the area, since they
have not endured the same grade of
metamorphism (Wik et al., 2006; Thomas
Eliasson, personal communication, 2016).
Rocks from the Almesåkra group are much
more compacted, and comprised of both
quartz arenite and arkose (Wik et al., 2006).
Rocks with a jotnian sandstone texture occur in
this area (Nationalencyklopedin, 2016). The
Vetlanda group is characterized by wackes,
sandstones, and some conglomerates that
have all been metamorphosed to some extent
(Wik et al., 2006). All of these sedimentary
rocks are at least 150 Ma years older than
those found in the Lower Paleozoic sandstones
from Västergötland. The Visingsö Group was
formed at the latest 700 Ma (Lundqvist et al.,
2011) and the Västgöta sandstones were
deposited during the Cambrian period
(Bergman et al., 2012).
Lundquist & Wohlfarth (2001) to ~13.9 ka yr
BP, and have therefore been deposited
sometime between the formation of the
Halland and Gothenburg moraines. The area
with the moraines lies directly west of the
studied area and can therefore be considered
to be relevant for this study.
Anjar et al. (2014) used 10Be exposure dating in
order to provide dates that does not only
represent the minimum age of deglaciation,
but when the ice actually left the area. This
study has been conducted across all of
southern Sweden. In their study, Anjar et al.
(2014) conducted exposure dating in areas
north and south of Gullaskruv, close to Lake
Åsnen and Sjöanäs. The dates produced in their
work show that the ice sheet passed over the
area sometime between 15.6 ka yr BP and 16.9
ka yr BP. These isotope dates of rocks have
yielded very inconclusive results, which could
either originate from errors in the method or
be explained by that the ice either re-advanced
or left in a very irregular or stagnant way.
Acquisition and transport of glacial
debris
Deglaciation of southern Sweden
About 20-19 ka yr BP, during the LGM (Last
glacial maximum), the ice sheet over
Scandinavia started to retreat (Clark, et al.
2009). It reached down to northern Germany
and covered Sweden and parts of Denmark.
The ice sheets retreat has been well
documented and compiled in several papers,
among others Lundqvist & Wohlfarth (2001)
and Anjar et al. (2014). The retreat is well
documented along the western coast of
Sweden where several end moraines have
been dated. The Halland coastal moraines have
been dated to 14.1- 14 ka yr BP and the
Göteborg moraine is dated to 12.7 to 12.6 yr BP
(Lundquist & Wohlfarth, 2001) The southern
Swedish highlands do not have continuous
moraines which can be seen as troublesome
when discussing the deglaciation. However,
there are some 14C dating of clay varves
performed by Björck & Håkansson (1982) from
lake Trummen, close to Växjö. These varves
have been interpreted and corrected by
When an ice sheet is advancing across a
landscape, the glacier acquires sediment and
transports it further away from its source.
According to Benn & Evans (2010) these clasts
have three different ways of entrainment and
transportation: (1) supraglacial, where rock
debris is deposited on top of a glacier by
avalanches or rock fall. These clasts are later on
transported on the top of the ice until they are
deposited. Material from underneath the ice
can also be thrusted up in the ice and carried in
a supraglacial position over large distances; (2)
englacial, where the clasts can have the same
entrainment principle as supraglacial material
with avalanches, but are later covered by
accumulating snow and ice on top of them. The
same thrusting mechanic as with supraglacial
material can also create englacially transported
material; and (3) subglacial, where the material
is dragged along underneath it or in the basal
debris-rich zone within the ice.
7
Puranen (1988) concluded that clast transport
distance varies depending on both transport
time as well as glacier velocity. Clasts
transported en- or supraglacially can therefore
travel farther since the ice creep movement is
faster there. This can lead to that the
provenance of the clasts vary in the
stratigraphy when supraglacial material is
deposited on top of basal material.
When the ice left the area these melt out
features were created when the debris-rich ice
melted away slowly.
Andersson
(1998)
conducted
a
sedimentological study of hummocks in the
area close to lake Bolmen, approximately 120
km from Gullaskruv. He argued that the
hummocks in this area were formed by
supraglacial
material
accumulating
in
depressions at the top of the ice. This material
could possibly have been thrusted up from the
bottom of the ice due to a re-advance. This
later resulted in an inversion of the landscape.
The former depressions in the ice now
appearing as hills and knobs scattered across
the landscape. An illustration of this principle
can be seen in Fig. 5.
Hummocks
Hummocky glacial deposits in Småland have
almost exclusively been interpreted as
stagnant ice deposits (Andersson, 1998;
Hebrand & Åmark, 1989; Möller, 2010).
Stagnant ice is ice that has been left behind as
the ice sheet retreats and which is no longer
flowing. These interpretations have also been
made by Möller and Dowling (2015) who
described hummocks in southern Sweden as
stagnant ice deposits. Their study was
conducted with the help of LiDAR data, and
they have described two different zones
landform where the deposits have certain
characteristics. One zone is described as ribbed
and hummocky moraine, and the other is
described as a streamlined terrain, which
contains drumlins and other streamlined
features. Hummocks occur in between the
streamlined features, which is also the case
with the hummocks in this study. In their study,
Möller & Dowling (2015), classified their
hummocks as stagnant ice glacial deposits with
an elongation ratio of less than 2, which means
that the length of the formation must be
smaller than twice that of the width.
Hummocks and their formation have been a
topic of discussion in geology. Generally,
hummocks have been interpreted as some
form of collapse of supraglacial material
(Johnson and Clayton, 2003). These hummocks
typically have rather chaotic shapes and
formations. In addition to the supraglacial
collapse origin, other studies have argued for
other processes. Johnson et al. (1995)
conducted a study in Wisconsin, USA, arguing
that the hummocks in their study area are
formed by melt-out from basal debris-rich ice.
Figure 5. Supraglacial formation of hummocks by infilling
of sediment in depressions and later inversion of the
landscape. From Benn & Evans (2010).
Hambrey et al. (1997) argues that some
hummocks formed both in Scotland and on
Svalbard are the result of thrusting in a polythermal glacier. Subglacial material is thrusted
up from the bottom of the glacier and carried
in an englacial or supraglacial setting. The till is
8
later deposited when the glacier melts, and the
deposits form hills and knobs that follow each
other in a train. An example of this can be seen
in figure 6.
suggests that these hummocks were formed by
subglacial processes.
The hummocks at the study site near
Gullaskruv (Fig. 7) have a somewhat regular
pattern, which is uncommon in stagnant ice,
collapse-type hummocks as described
previously in the area. These hummocks are
wedge shaped with a steep side pointing
towards SSE. The hummocks have somewhat of
a fan-shape or triangular shape where the
steep side of the hummocks is the thinnest and
they widen on their flat side. These wedges of
hummocks seem to overlap each other which
is the origin of the name “fish scale”
hummocks. Their length range from 100m to
30m and are typically around 70m long. Their
widths wary between 70m to 30m.They are
typically around 6-7m tall, but slight variations
occur.
Figure 6. Hummock formation by thrusting according to
Hambrey et al. (1997).
Johnson and Clayton (2003) also discuss the
possibility of subglacially deposited and formed
hummocks. They list several different ways
that other papers have discussed how
hummocks could have been formed
subglacially. They include pressing of ice blocks
in a stagnant setting into a deformable bed and
an active ice subglacially molding hummocks,
rogen-moraines and drumlins.
Hummocks in Gullaskruv
The new LiDAR images show that the
hummocks have a wide variety of shapes
including several recognizable types. Because
of this variety, it is likely that different
hummocks forms may have different origins.
Thus, the genesis of some of these hummocks
has to be reconsidered. The work being
produced by Gustaf Peterson aims to utilize
this new data in order to clarify whether or not
there are other possibilities of genesis for the
hummocks in the area. For example: A
hummock near Hörda studied by Dahlgren
(2013) and Grodzinsky & Thor (2016) is overlain
by an esker, which along with other signs
Figure 7. Close up of the hummocks in Fig. 2. The green
dots symbolize the sampling sites.
Esker formation
Eskers are long, elongate glacial landforms
created when an ice sheet retreats over a
landscape and deposits glacifluvial material
along the way through large meltwater
channels (Benn & Evans, 2010). These
meltwater channels or tunnels are eventually
filled by the glacifluvial sand and gravel and a
ridge is created when the ice has fully melted.
The meltwater channels can either be en-, sub9
, or supraglacial. The length of the ridges is
controlled by whether or not the material is
deposited by a normal retreat of the ice, by a
surging glacier or if the glacifluvial material is
deposited into a subaqueous fan. The two
latter cases can result in stubby, short eskersections spread out over the landscape.
Hebrand and Åmark (1989) have studied eskers
in the vicinity of the study area. They infer that
the eskers were formed by subglacial
processes, and not in open supraglacial
channels. Their study area lies in the northern
part of Skåne, south of the area studied in this
thesis.
GIllberg (1968) concluded that
sediment and clasts deposited in eskers often
are previously transported subglacially by the
glacier. Eskers can therefore be considered to
be composed of secondary sediments. Gillberg
(1968) also concluded that a long transport of
the glacifluvial material will result in a large
variety of lithologies.
arbitrarily chosen as the grain-size fraction for
collection. The clasts with approximately the
right size that were in close proximity to the 50
cm mark were collected. They were then
placed in a sampling bag that was labeled
MTGE-XX for eskers or MTGH-XX for
hummocks.
Figure 8. Sampling during field work in Gullaskruv,
Småland.
Methodology
The span of the clasts size is rather large seeing
that the clasts with different sizes could have
travelled different lengths. However, this could
compromise the random selection since the
method with the measuring tape is dependant
on picking the clast closest to each 50 cm mark.
If this method was not performed, the
ramndomness of the test would not be the
same which would compromise the CHI2-test.
Field work
Sampling sites were selected using SGUs
application GEOKARTAN with a LiDAR map and
a Hillshade cover to locate old cuts, i.e. gravel
pits, road cuts, into the glacial landforms. Sites
where Gustaf Peterson had already done
excavations and logging were also used. Mark
Johnson and Gustaf Peterson helped identify
hummocks and eskers that were suitable for
sampling.
Lab work
The samples were washed and scrubbed with a
fiber brush in a lab in order to get rid of clay and
lichen. The washed samples were put in labeled
boxes in order to keep them separated from
each other and avoid possible contamination.
The sampling took place at several different
locations, in close proximity to Gullaskruv. Five
samples from hummocks and five samples
from eskers were collected during the field
work (Fig. 7). Two of the sampling sites were
sampled twice since they were located in
favorable excavations. Each of the samples
contained approximately 100 rock samples
each.
A large part of the work consisted of the
classifications of different rock types. In order
to determine which rock classes to assign to
the different rocks, local bedrock geology maps
from Wik et al. (2006) & Wik et al. (2007) were
utilized along with the expertise from SGU. The
rock classes that were finally used were: Basalt,
diabase, gabbro, granite, pegmatite, porphyry,
rhyolite, sandstone, TIB granite and quartzite.
The rocks were selected randomly by placing a
measuring tape in front of an exposure, and
rock samples were taken every 50 cm, see Fig
8. A phi size of -5 to -6 (32 to 64mm) was
10
Ulf Bergström, Lena Lundquist and Thomas
Eliasson, geologists from SGU, Göteborg,
supervised part of the classification of the
different rock types. They, among other things,
helped show the difference between rhyolites
and granites, which in the study area have very
similar characteristics. These geologists have
been part of a team mapping the area
previously. Their knowledge was essential in
order to ensure that the classifications were
made correctly.
After samples were classified, a measurement
of their long A-, intermediate B- and short Caxes were made with calipers and roundness
was estimated for use in a shape analysis
according to Sneed & Folk (1958) and Powers
(1953). The categories used for roundness
were Very Angular (VA), Angular (A), SubAngular (SA), Sub-Rounded (SR), Rounded and
Very Rounded (VR). The samples were entered
individually into an excel sheet designed by
Graham & Midgley (2000) in order to calculate
the samples C40 index. C40 index is the portion
of clasts where the axis ratio c/a is ≤ 0.4. The
samples RA indices were calculated by dividing
the amount of angular and very angular clasts
with the total amount of clasts. This was done
in order to compare the samples to the control
samples established and utilized by Lukas et al.
(2013).
A hand lens was utilized during the
classifications along with a magnetic pen.
Sometimes a hammer was used in order to
examine a fresh surface. To preserve and
document the rocks original shape for the
shape analysis, this procedure was performed
after the axes of the clast were measured.
Some of the samples were cut with a rock saw
in order to either highlight good examples of
certain rocks or see a fresh surface of a rock
that was too hard to break with a hammer.
Samples that were of special interest, stood
out from the rest or were good examples of a
certain rock type were labeled and recorded in
an excel sheet. An example from the
classifications can be seen in Fig. 9.
Lithology and shape data was collected,
compiled and processed in Microsoft Excel,
where a CHI2-test was performed. A CHI2-test
examines whether the lithologies of the
samples are significantly different by
calculating the expected amounts for each
parameter observed.
Figure 9. All rock samples from sample GH02 during the classification.
11
Results
Rock descriptions
Fine grained extrusive rocks with a mafic
composition where classified as basalt (Fig. 10).
These rocks are commonly weathered on the
outside. Their color is black or very dark grey,
sometimes with a hint of green or blue when
weathered.
Figure 10. Basalt sample from an esker.
Rocks with a mafic composition with small
grains of white plagioclase, albite, in a dark
matrix were classified as a diabase (Fig. 11).
These rocks were commonly very hard. Some
of them had an ophitic texture.
Rocks with an albite matrix and small mafic
grains were classified as gabbro (Fig. 12). These
rocks could also be of a diorite or granitoid
composition, but that distinction has not made.
Metamorphosed samples are included in this
category.
Figure 11. Diabase sample from an esker.
A large number of the rocks classified as granite
(Fig. 13) have a composition that resembles
syenite or a syenite granite. A distinction has
not been made as suggested by the SGU
geologists. Rocks classified as granite are
commonly fine grained and the tags X, Y, Z has
been applied when the rock is of granitic
composition but differs from the rest of the
granites. A P-tag has been added to some of the
clasts if they contained some phenocrysts or
had a minor porphyric texture, a G or M tag has
been added if the sample shows signs of
metamorphism or it has a gneissic texture. A
common denominator of these rocks is that
they have a texture that is aplitic or close to
aplitic.
Figure 12. Gabbro sample from a hummock.
Figure 13. Granite sample from a hummock.
Rocks with very large homogenous grains of
either quartz or potassium feldspar were
classified as pegmatite (Fig. 14).
Some of the rocks with a granitoid composition
were hard to distinguish from each other. Since
there are a lot of felsic extrusive rocks that
have formed simultaneously to the granites in
the area (Lundqvist et al., 2011), there are a lot
of rocks that are hard to differentiate whether
Figure 14. Pegmatite sample from an esker.
they are of an intrusive or extrusive origin.
These rocks have been classified as porphyry
(Fig. 15) since that is often used as a
12
nomenclature for sub volcanic or hypabyssal
rocks with a granitic composition. The origin of
these rocks was hard to establish since they
have a lot of characteristics similar to both
rhyolite and granite. All of these samples had
large phenocrysts of quartz, potassium
feldspar or plagioclase, embedded in a finer
matrix, which are characteristic for porphyries.
Figure 15. Porphyry sample from an esker.
Rocks with a very quartz rich composition and
high metamorphic texture, and some small
mafic grains have been classified as quartzite
(Fig. 16).
The rhyolites (Fig. 17) in the samples commonly
have a very fine grained matrix, undetectable
without magnification. Some samples are even
glassy in their texture. A pink to dark red color
is common. They almost always contain
phenocrysts. A P-tag has been added to
samples with very prominent phenocrysts. A Dtag has been added to samples with a grey
color that appeared to be of dacitic
composition. These samples are commonly
gray, but a distinction was not made. Samples
that had been metamorphosed or had a
mylonitic texture were labeled with an M-tag.
Figure 16. Quartzite sample from an esker.
Figure 17. Rhyolite sample from an esker.
Sandstone (Fig. 18) occurs in some samples.
They primarily stem from the Almesåkra group
(unit 95 in Fig. 3), but some less compacted,
samples have been interpreted to be from the
Visingsö group (unit 14 in Fig. 3). Commonly
they are fine grained and mostly quartz arenitic
in their composition. A J-tag has been added to
one sample that has a texture that bears
resemblance to Jotnian sandstone. A C tag has
been added to samples that have the
characteristics of sandstone deposited during
the Cambrian. Samples with a silt matrix have
been labeled with an S tag. Conglomerates
have also been found in the samples. They are
often somewhat metamorphosed, which is
common for rocks from the Vetlanda (unit 111
in Fig. 3) and Almesåkra formations. There are
some conglomerate bodies in the eastern part
of this region. These rocks commonly have a
sandy or silty matrix with embedded coarser
Figure 18. Sandstone sample from an esker. Good
example of rock from the Visingsö group.
Figure 19. TIB granite sample from an esker.
13
clasts. These rocks have been classified as
sandstone for the statistic test in this thesis.
Basalt, gabbro, granite and porphyry are more
common in the hummock samples. But
pegmatite, conglomerate, gneiss and quartzite
did not occur at all. In the samples from eskers,
Rhyolites and TIB granites are more numerous
than in the hummock samples.
Rocks classified as TIB granite (Fig. 19) have
characteristic medium to coarse grains of
quartz and potassium feldspar, which is typical
of the rocks formed in the Transscandinavian
Igneous Belt.
CHI2 test
The result from the CHI2-test is shown in Table
2 where P denotes the significance level. A
significance level of 0.05 is often utilized as a
delimiter if there is a significant difference
between the two datasets. A lower number
means that there is a significant difference
between the two samples, which there is in this
test.
Provenance studies
The summary of the lithological classifications
for all the esker samples and all the hummock
samples are shown in Table 1 and Fig. 21.
Table 1. Result from the classification of rock samples
from eskers (GE) and hummocks (GH).
Rocktype
GE
GH
Basalt
6
8
Diabase
3
3
Gabbro
3
5
Granite
69
218
Pegmatite
6
0
Porphyry
29
141
Quartzite
2
0
Rhyolite
319
110
Sandstone
8
1
TIB granite
59
37
Total
504
523
The esker samples show a wide diversity of
rocktypes. Several different types of rocks are
represented, where basalt occurred in almost
all of the samples. The rhyolites are by far the
most common rock type. The two different
types of granites and porphyry also occur quite
frequently, but not nearly as abundantly as the
rhyolites.
Table 2. Results from the CHI2-test
Observed Basalt Granite Porphyry Rhyolite Other TIB granite TOTAL
GH
8
218
141
110
9
37
523
GE
6
69
29
319
22
59
504
TOTAL
14
287
170
429
31
96 1027
Expected Basalt Granite Porphyry Rhyolite Other TIB granite TOTAL
GH
7,130 146,155
86,573 218,468 15,787
48,888
523
GE
6,870 140,845
83,427 210,532 15,213
47,112
504
TOTAL
14
287
170
429
31
96 1027
P
7,02E-55
Provenance markers
In several cases, the lithologies can be traced to
specific localities and specific mapped rock
units, and these interpretations have been
corroborated in conversation with the SGU
geologists mentioned above. The Jotnian
sandstone from sample GE02 is inferred to
come from the Almesåkra group (unit 95 in Fig.
3).
The samples collected from the hummocks are
not as diverse in different rock types as the
samples from eskers. The most common rock
type is the fine-grained type of granite.
Porphyry and rhyolite also occur in large
quantities. However, the three most abundant
rocks show a more even distribution. The TIB
granites are not as common as in the esker
samples, but still occur in every esker sample.
Figure 20. Jotnian sandstone from the Almesåkra group.
The basalt sample in Fig. 10. is inferred to come
from the basalt formations south or east of the
Vetlanda group (unit 112 in Fig. 3).
The histogram in Fig. 21 highlights the
differences between the two types of deposits.
14
The sandstone in Fig. 18. is inferred to come
from the Visingsö group (unit 14 in Fig. 3).
had much lower C40 values, 4-10%. The RAindices are low to non-existant in the esker
samples but range from 30-50% in the
hummocks.
Shape analysis
The shape analysis resulted in tri-plots where
each triangle represents one sample (Fig. 23 &
24).
The different samples RA and C40 indices were
plotted against each other in a covariant plot
(Fig. 22) in order to compare with Benn & Evans
(2010) and Lukas et al. (2013).
The samples from the eskers has C40 indices in
the 10-30% range, but the hummock samples
70,0%
63,3%
60,0%
50,0%
41,7%
40,0%
30,0%
27,0%
21,0%
20,0%
13,7%
11,7%
10,0%
7,1%
5,8%
1,2% 1,5% 0,6% 0,6% 0,6% 1,0%
0,0%
Basalt
Diabase
Gabbro
1,2%
0,0%
0,4% 0,0%
1,6%
0,2%
Granite Pegmatite Porphyry Quartzite Rhyolite Sandstone TIB granite
GE
GH
Figure 21. Bar plot showing a side by side comparison of the two samples rock type distribution in percentages.
1,00
0,90
0,80
RA index
0,70
0,60
0,50
GH
0,40
GE
0,30
0,20
0,10
0,00
0,00 0,10 0,20 0,30 0,40 0,50 0,60 0,70 0,80 0,90 1,00
C40 index
Figure 22. Co-variant plot of RA and C40 indices for the different samples plotted against
each other.
15
Figure 23. Results from the shape analysis. From top left GH01, GH02, GH03, GH04 & GH05. The tri-plots were used to
calculate C40 and the bar plots in each top right corner shows the distribution of roundness.
Figure 24. Results from the shape analysis. From top left GE01, GE02, GE03, GE04 & GE05. The tri-plots were used to
calculate C40 and the bar plots in each top right corner shows the distribution of roundness.
16
type could be classified and origin determined
were interpreted to be very local. The different
granites from the TIB are of local origin and it is
very improbable that they would come from
another area in Sweden or Norway. The TIB
extends up through Värmland, Dalarna and
parts of Norway, but those rocks have very
dissimilar characteristics to the ones found in
Småland and are not as fine grained. The same
principle should also apply to the porphyries.
They are very common in Dalarna, but given
the very local signature of the other rocks, it is
highly improbable that they have traveled that
far. The only rocks that had to have been
transported over a greater distance are the
basalts. The only large basalt bodies found in
the local bedrock geology are the basalt bodies
near the Vetlanda formation, approximately 70
kilometers away.
Discussion
Provenance study
It is hard to exactly pinpoint the outcrops a
large portion of the rock samples from the
hummocks originated from. However, all of
them were determined to have a very local
signature. None of the rocks in the samples
have been identified as being transported very
far, more than 70 km.
Porphyry, rhyolite, granite and TIB granite are
considered to be locally eroded and. These
rocks occur in the immediate proximity of the
glacial deposits and do not have to travel a very
long distance in order to end up in the
hummocks or eskers. The origin of pegmatite
and diabase are harder to pinpoint since there
are many basalt dikes and quartz and
pegmatite veins in the area. The diabase rocks
are possibly from the Almesåkra group, but the
age for the dikes and the large formations in
the Almesåkra group have the same age. Thus,
even if a chemical analysis were to be
conducted, it would be hard to exactly
determine their origin. Sandstone and basalt
are not per se locally eroded, since there are no
occurrences in the immediate proximity to the
studied hummocks or eskers. But their
provenance has been determined to be from
the area in, or close to, the sedimentary
deposits in the Jönköping province. Thus, rocks
from the Visingsö group would have to travel
about 130 kilometers in order to end up in the
esker deposits where they were found. The
gabbroic samples could stem from various
gabbro bodies in the area, and it is impossible
to say from which one without further chemical
analyses. The quartzite observed in the
samples are much more deformed than the
hard sandstone originating from the Almesåkra
formation, suggesting that this is not their
origin. Hence, its origin cannot be fully
determined.
The single sandstone found in the hummock
samples was very hard and probably somewhat
metamorphosed or at least compacted. This
would indicate that the rock originates from
the Almesåkra or Vetlanda formation. Taking
the suggested transport route in Fig. 25 into
account, it would be probable that this
sandstone is from the Vetlanda group. The
hardness of this rock type would allow it to be
transported over a large distance or even
survive a previous deposition and retransportation. The same is also true for the
basalts. They were all somewhat rounded
which could point towards re-deposition and
transportation from a previous glaciation or
transportation mechanism. This would further
lower the transportation distance for the
hummocks. The studied hummocks must be
considered locally eroded and transported
given these factors.
The hummock samples also contain a lot of
local rocks with similar lithologies as in the
esker samples, even though the composition is
different. Most of the rocks in which the rock
17
CHI2-test
Difference between eskers and
hummocks
The CHI2-test yielded a significant difference
between the esker samples and the hummock
samples. This could suggest that the samples
have different provenance. However, the fact
that both of the landforms contain very local
rock types suggests that both of the sample
groups are still largely locally eroded, entrained
and deposited. The large significant difference
could stem from the fact that the deposits are
in close proximity to a contact zone between
rhyolite and granite and that the different
landforms have been created by different
transport routes in the ice or in the subglacial
tunnel systems. This would explain the
different composition of the hummocks and
eskers, while maintaining the observation that
they both are locally eroded, entrained and
deposited, see Fig. 25.
The black lines in Fig. 25 represent the possible
transport routes for the eskers. They have been
drawn on top of eskers from SGUs soil surficial
maps obtainable through SGUs service
Geolagret. The lines have been interpolated
where there were no eskers. Esker deposits
pass through the extrusive rock formation
close to the sampling sites and does only enter
the intrusive granite batholites after a couple
of miles. The black lines should not be
interpreted as long complete eskers, but as a
possible transportation route for the
meltwater tunnels under the ice. However,
these could just as well not be representative
for the tunnels during the entire time of
deglaciation because esker deposits are time
transgressive. But, the extended inferred esker
deposits pass through all of the different rock
Figure 25. Bedrock map from SGU over the extended study area. Green dots symbolize the extent of the sampling area. The
blue lines represent eskers mapped by SGU. The black line are inferred esker transportation routes. The green line is the
suggested transportation directon of the hummocks. The circles show where the different lithological probably originated
from.
18
types found in the eskers, which would make
this a viable transportation route and explain
the significant difference between the
hummock and esker deposits from the CHI2test. Based on the hummocks appearance,
general ice sheet retreat movement and which
rock types that were found, the dark green line
is a suggested route that the ice could have
moved.
by two different transportation methods have
a larger opportunity to travel a longer distance.
It could be argued that the increased amount
of rhyolites in the eskers stems from that the
way transport may comminute different rock
types at different rates. The granites and
porphyries transported glacifluvially would
therefore have had to be broken and eroded at
a higher rate. The samples from the eskers
were much more rounded than those from the
hummocks and by that reasoning, more
abraded. But the chemical composition and
hardness of the rhyolites, granites and
porphyries are too similar for this effect to be
fully acceptable as a reason for the difference.
A remarkable observation in the esker samples
is that they are composed of a large majority of
rhyolites (63,3%) but at the same time have a
large distribution of different kinds of rock
types. This implies that the ice forming the
eskers eroded a lot of rhyolites during their
formation, but also eroded quite a large area.
Gillberg (1968) concluded that long eskers
often contains varying lithologies, which fits
very well in this case. The eskers west of the
hummocks would have been formed in tunnels
where the ice had eroded the rhyolites at a
greater extent. The Jotnian sandstone found in
sample GE02 likely originates from the
Almesåkra group, since the sample contains
both feldspar and quartz and is very hard. The
more loosely packed sandstone found in the
same sample was likely eroded from the
Visingsö group. This suggests that the eskers
are capable of transporting material over a vast
distance, even though most of the material is
locally eroded.
The fact that the different rock types were not
observed or studied in situ is undesirable and
something that could have been done to give
more legitimacy to the thesis. This could have
been done by collecting control samples from
outcrops in the field and comparing these to
the clasts found in the eskers and the
hummocks. However, it can be argued that the
assistance from geologists from SGU during the
classifications negates any effect this would
have on the project’s result.
According
to
Puranen
(1988)
the
transportation distance of clasts can vary in the
vertical stratigraphy of the formation. The
clasts at the top could have been transported
further if they were carried higher up inside or
on top of the ice. The sampling method used in
this thesis does not account for this effect since
the measuring tape was laid out horizontally
across the formation. This could lead to that
the samples all displayed signs of one kind of
transportation distance. However, the
collected clasts showed signs of both short and
long transport so this effect could be
considered negated and the results valid and
representable. A sampling section with a
vertical direction could have been performed
in order to compare to the rest of the samples.
This could strengthen the results even further.
The wider range of different lithologies
occurring in the eskers could infer that the area
of erosion and transportation is larger for the
eskers than the hummocks. This would further
strengthen that the hummocks are a very
locally eroded and transported landform,
which would point at subglacially transported
debris. This becomes even more clear when
taking the different maximum transportation
distances into account, ~130 km for eskers and
~70km for hummocks. Eskers are often thought
of as being secondary deposits as suggested by
Gillberg (1968) which could explain that some
clasts seem to have been transported over a
very long distance. Clasts that are transported
19
Shape analysis
The shape analysis shows that there is a large
difference in roundness between the clasts
that were deposited in a hummock and those
that were deposited in an esker. Their C40
indices were also very different. When
comparing the covariant plot of the RA- and
C40 indices in Fig. 23, to the control samples
from Lukas et al. (2013) (Fig. 26), it can be
found that the samples from this thesis plots
very similarly to the subglacially transported
gneiss samples in their study. The gneiss
samples from their study have to be considered
the most relevant in this study, since the
majority of the lithologies found in the samples
are of granitic composition. The esker samples
from this study can also be utilized in these
covariant plots. If they are compared to
fluvially transported material in the same
control samples from Lukas et al. (2013) it can
be noted that these samples have very similar
RA- and C40 indices. The shape analysis
supports a fluvial history for the esker
sediment and a subglacial history for the
hummock sediment. Significantly, the shape
analysis does not show that the material from
the hummocks is similar to scree or
supraglacial material, indicating that the
hummock sediment is subglacial or did not
occur in a supraglacial position for any length
of time. In order to be considered to be
supraglacially transported material or scree,
the angularity of the rocks should also have
been much higher, according to Benn & Evans
(2010).
Figure 26. Covariant plots of control samples from Lukas
et al. (2013) with the results from the shape analysis
from this study plotting inside the circles. The orange
circle for the hummocks and the blue circle for the eskers.
In many ways, the Gullaskruv hummocks
resemble the ones studied by Hambrey et al.
(1997) both in morphology and clast shape.
Hummocks like these are inferred to be formed
by active ice which is in direct conflict to the
many observations of stagnant ice deposits in
the area (Hebrand & Åmark, 1984; Möller
2010). It is a possibility that this proposed
thrusting is a local occurrence in an otherwise
stagnant ice setting. But, the landscape is
dominated by drumlins and other streamlined
landforms, indicating subglacial activity. A readvance into a stagnant ice could possibly
produce thrusting large and prominent enough
in order to create these hummocks, but it
would have to be very local or small in order to
maintain the rest of the stagnant ice features.
If active ice is involved, it likely played a role in
the orthogonal structure displayed by the
hummocks (Fig. 7).
Hummock formation
Andersson (1998) suggested that the
hummocks in his area in western Småland were
formed by supraglacial deposition of rock
debris on top of stagnant ice. The till is argued
by Andersson (1998) to be in a supraglacial
position due to thrusting occurring during a readvance of the ice. This corresponds very well
with both the shape of the Gullaskruv
hummocks, the subglacially transported
material according to the clast shape analysis
and the stagnant ice setting of the area around
it. The theory proposed by Andersson (1998)
When considering the very local provenance of
the clasts and the result from the shape
analysis (Fig. 23) it stands clear that the
hummocks must have been formed by locally
eroded rock fragments that at least initially
were transported subglacially.
20
does include the stagnant ice setting in the area
(Möller, 2010; Möller & Dowling, 2015) which
Hambrey et al. (1997) does not. A re-advance
into stagnant ice could also help explain the
“Fish scale” pattern in the hummocks as a
result of till being deposited on top of a
stagnant ice and inverting the landscape when
it melts away. Even if the suggested genesis of
hummocks in the area does not quite fit the
Gullaskruv hummocks, does not mean that
their investigations are wrong. The Gullaskruv
“Fish scale” hummocks are a very local type of
feature which has not been observed before.
So, even if they do not fit perfectly with the
previously suggested origin for hummocks in
the area, these previous theories are not in any
way disproven by this study.
suggests that the clasts were not glacifluvially
transported and that a supraglacial transport is
highly unlikely given the very local provenance
of the majority of the rocks.
Conclusions
The hummocks in the study are composed of
clasts that has been eroded in an area very
close to the deposits. The hummocks were
likely formed in a stagnant ice setting where
the ice sheet re-advanced and thrusted
subglacial material was left behind with the
stagnant ice. This material has probably not
been transported supraglacially for a long time
but has been thrusted up onto the ice during a
re-advance. The hummocks in the area has
previously been suggested to have been
formed when the stagnant ice with till on top
of it melted away causing an inversion of the
landscape. It could be argued this is the case
even for these hummocks. Results from the
shape analysis and the local provenance of
rocks found in the hummocks suggest that they
have been transported subglacially over a fairly
short distance. The shape of the hummocks,
which can be observed in the LiDAR images,
also corresponds with this theory as they
resemble those found by Andersson (1998).
The stagnant ice setting of the area as indicated
by Möller (2010) and Möller & Dowling (2015)
also fits in very well with this theory.
If these hummocks were to be formed by melt
out like the ones suggested by Johnson et al.
(1995) they would need to have a larger
amount of clasts transported over a long
distance. The melt out hummocks are often
formed by basal debris from the base of the
glacier. The provenance study cannot fully rule
out that this is a possible explanation of the
Gullaskruv hummocks, but this would have to
be proven by other studies and more
investigations.
A formation by squeezing as described by
Johnson & Clayton (2013) seems unlikely given
the shape of the hummocks. In the LiDAR
pictures, they seem to overlap each other. This
would be easier to explain if they were to be
formed by a stagnant ice with debris thrusted
up between the stagnant ice segments.
There is a significant difference between the
rock types of the hummocks and eskers in the
area. They are however both comprised of
predominantly locally eroded rocks. The
difference could be explained by an alternate
transport route for the eskers, as well as a
longer transport distance.
All previous studies in this area have been
concluding that the glacial landforms in the
area are the result of a stagnant ice. It could be
the case for the hummocks, but it has to be
argued that these hummocks could very well
be the result of a supraglacial deposition, if it
has been done by thrusting. In order to
establish whether they have been formed by
squeezing, melt out or another medium, more
sedimentological studies will have to be
performed. However, the shape analysis highly
Further studies
Further sedimentological research is being
conducted by Gustaf Peterson for Gothenburg
University and SGU. In terms of provenance
studies some chemical analyses would be
helpful in order to establish provenance,
especially in some of the sandstones and
diabases. Radiometric dating on some clast
21
which provenance were hard to pinpoint could
also be useful to further improve the results in
this study.
Dahlgren, S. (2013). Subglacially meltwater
eroded
hummocks
(Master
thesis).
Gothenburg: Department of Earth Science,
University of Gothenburg.
Acknowledgements
Gillberg, G. (1968). Lithological distribution and
homogeneity of glaciofluvial material. GFF,
90(2), 189-204.
We would like to thank our supervisor Mark
Johnson and Gustaf Peterson for their help,
both in the field and with designing this thesis.
We would also like to thank Thomas Eliasson,
Lena Lundquist and Ulf Bergström at SGU for
their help during the rock type classifications.
Their help was invaluable. Andreas Karlsson
also provided a lot of help during the
classifications and definitely deserves a
mention.
Graham, D. J., & Midgley, N. G. (2000).
TECHNICAL
COMMUNICATION-Graphical
Representation of Particle Shape using
Triangular Diagrams: An Excel Spreadsheet
Method. Earth Surface Processes and
Landforms, 25(13), 1473-1478.
Grodzinsky, K., & Thor, M. (2016). Insights into
landform genesis based on lithological
provenance studies in the western South
Swedish highlands near Hörda. (Bachelor of
Science thesis). Department of Earth Sciences,
Gothenburg University.
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23
Appendices
Appendix 1. Full results from the classifications of the samples from hummocks.
GH01
Diabase
Gabbro
Granite
Granite M
Granite P
Porphyry
Rhyolite
Rhyolite P
TIB granite
2
1
33
2
15
18
19
3
10
GH02
Basalt
Gabbro
Granite
Granite P
Granite X
Porphyry
Rhyolite
Rhyolite P
Sandstone M
TIB granite
6
4
23
6
1
21
42
1
1
6
GH03
Granite
Porphyry
Rhyolite
TIB granite
62
9
25
3
GH04
Granite
Granite E
Granite Z
Porphyry
Rhyolite
Rhyolite P
TIB granite
GH05
Basalt
Diabase
Granite
Granite P
Porphyry
Rhyolite
Rhyolite P
TIB granite
2
1
9
5
70
5
3
15
GE05
Conglomerate
Porphyry
Rhyolie WT
Rhyolite
Rhyolite C
Rhyolite D
Rhyolite M
Rhyolite P
Rhyolite R D
Rhyolite WT
Sandstone
TIB granite
TIB granite K
1
12
1
55
1
3
2
5
1
3
1
16
1
58
1
3
23
11
1
3
TOTAL
Basalt
Diabase
Gabbro
Granite
Porphyry
Rhyolite
TIB granite
Sandstone
Total
8
3
5
218
141
110
37
1
523
TOTAL
Basalt
Diabase
Gabbro
Granite
Pegmatite
Porphyry
Quartzite
Rhyolite
Sandstone
TIB granite
Total
6
3
3
69
6
29
2
319
8
59
504
Appendix 2. Full results from the classifications of the samples from eskers.
GE01
Basalt
Conglomerate M
Granite G
Granite
Granite M
Granite P
Porphyry
Rhyolite
Rhyolite M
Sandstone J
TIB granite
1
1
2
21
1
1
9
52
2
1
9
GE02
Basalt
Conglomerate
Diabase
Granite
Granite P
Pegmatite
Porphyry
Quartzite
Rhyolite
Rhyolite B
Rhyolite D
Rhyolite M
Rhyolite P
Rhyolite WT
TIB granite
2
1
1
7
2
2
1
1
67
1
1
1
1
2
10
GE03
Basalt
Gabbro
Gabbro M
Granite
Granite T
Pegmatite
Porphyry
Quartzite
Rhyolite
Rhyolite D
Rhyolite D M
Rhyolite M
Sandstone
TIB granite
2
2
1
10
2
2
4
1
63
3
1
5
1
5
GE04
Basalt
Diabase
Granite
Granite
Granite G
Granite P
Granite T
Pegmatite
Porphyry
Rhyolite
Rhyolite C
Rhyolite D
Rhyolite M
Rhyolite P
Rhyolite P WT
Rhyolite WT
Sandstone
TIB granite
24
1
2
15
1
1
4
2
2
3
39
1
1
1
2
1
4
2
18