geology of massif montgris

DeclarationThis report entitled "The Geology of the Massif Montgris" was
composed by me and is based in my own work. Where the work of
others has been used, it is fully acknowledged in the text and in captions
to tables and illustrations. Signed Date
Chapter 1.0AbstractThis is a study of the
Massif Montgris, it is based on evidence gathered in the field over 21
days of field work. To supplement this data I have looked at papers and
works by previous visitors to the Montgris. The units within the area are
from the Upper Cretaceous the Tertiary and the Quaternary. I aim to give
an overall guide to the geology on a smaller scale than has previously
been accomplished. This study is mainly aimed at correctly dating the
units of limestone using micropalaeontological data. The
micropalaeontological data has also given light into the
palaeoenvironment/geography during deposition.Chapter
2Introduction2.0.1 Introduction Between the 24th of June and the 24th
of July 1995 Glen Burnham and I ventured to Catalunya. More precisely
to Torroella de Montgris. Torroella is in the North East of Spain, just
inland of the Mediterranean sea. This remarkable old town lies at the
foot of the rather imposing Massif Montgris.Locally known as "El
Montgris" (literally the grey Mountain) the massif rises up over the town
and dominates the skyline. Torroella sits on quaternary conglomerate
deposits. These are easily eroded, hence the valley between Pals (10Km
to the south) and Torroella is extremely flat. The valley is bisected by the
river El Ter, which flows at a leisurely pace from the foothills of the
Pyrenees. The river flows to the south of Torroella and winds it's way to
its conclusion in the Playa de Pals (6Km east of Torroella).El Montgris
has been known to humans since prehistoric times. It has some large
caves on its slopes that served as a shelter to prehistoric man. The area
was very popular with the Romans who cultivated the local area, built
roads and towns (many of which still stand to this day) such as
Peretelada to the south adjacent to Pals. Since the time of the Romans

Torroella has grown into a thriving market town. It has always had close
links with the Montgris which until recently still served a purpose as a
shelter, not , however, against the elements but against Pirates and
marauders from the sea. In fact, on top of the Muntanya Santa Catherina
stands the remains of a thirteenth century castle (the last castle ever built
in Spain).El Montgris has provided for the local commerce since it was
first settled. The local people value the Mountains greatly and still use
them today. The rock from which our dwelling was made was quarried
from the mountain, the castle rock was quarried on the mountain. 2.0.2
Aims of Study.When I first considered the Montgris as a project area I
realised that information would be sparse and that the project would be
more complicated than a similar project in the U.K because the
environment is so very different and resources would be a great deal
more difficult to access (due to the language barrier). I also realised the
project would probably be very different to the proposal. Before Glen and
I left England we attempted to research the Massif Montgris through the
usual channels in order to get an idea of what we would be facing. The
research lead to a few vague leads, we new the rock was sedimentary
and most likely limestone. Having visited the area previously I could
recall a little about the rocks but was certain of their sedimentary nature.
Our first lead came from an unexpected source. My parents had
vacationed in the area and upon my request had asked locally about any
information pertaining to the Geology. The result was that they brought
back a research map that dated the Massif as Cretaceous but suggested
it was composed of 1 massive bed. We loosely agreed our study areas
and arranged our projects accordingly. The local guide books and map
had supplied us with information about the palaeontology (macro fossils)
which suggested the rock was full of bivalves, brachiopods, corals and
belemnites. Before leaving we were unable to unearth much more
information BUT seemingly at the last minute we were able to make

contact with Dr. David Brusi from the Universidad de
Gerona(departament del geophysica) who reassured us that upon our
arrival in Spain he would brief us on geology of El Montgris.Therefore,
with very little in the way of successful research we traveled to Spain.
Upon our arrival we immediately made our way to the city of Gerona and
to the University. Our meeting with David Brusi and his team proved very
productive indeed as they gave us a couple of papers about the area as
well as providing us with a geological map of the Montgris. The most
important information they gave us was about our working environment
and how to "survive".2.0.3 Methodology.Previously, we have been taught
to outcrop map. These skills were honed in the inhospitable environment
of the Highlands of Scotland, where one can actually draw outcrops onto
the map. It was, therefore, it was the intention to use this technique over
approximately 6km2 . In order for this mapping technique to work you
have to know what it is you are looking at. With this knowledge in mind
one set out to spend most of the first week exploring the area and
identifying the different strata, and their relationships. This as you will
see proved most difficult for various reasons. The plan had been to have
the Muntanya de Santa Catherina as common ground, but after 3 or 4
days we came to the conclusions were made that there was a need for
safety equipment. There were reports of packs of wild dogs patrolling the
area also the terrain was at best rugged and challenging and at worst
moderately dangerous. On top of all this it was understood that work
would have to be completed in temperatures of up to 40 0 Celsius, every
day with the possibility of hotter/muggier weather to come. Each day
would begin with plotting a starting position, when the castle was
obscured an estimated position would be used to locate a specific point.
Most dip/strike readings are estimated as there were not many bedding
planes level enough to use the compass clinometer accurately . The
local geological map (296-2-2[78-24]) gave an indication to the geological

relationships present, however, even though the map is a 1:25,000 it is
quite ambiguous with the position of some boundaries and faults.In order
to cross reference the different strata, samples were taken and labeled.
So further samples could be identified. This was assisted by the
geological map and by referring to the map it was possible to take
samples away from faults and boundaries to ensure correct
identification.Chapter 3The RocksThis is an in depth study into the
locations, ages and natures of the rocks that were studied. These have
included both observations from the field and later observations made in
response to new evidence, which was forthcoming after thin sections of
the different units were made in the laboratory.Whilst in Spain Glen and I
only had each other to consult on the more difficult matters of El Montgris.
This led to a subtle stagnation of ideas towards the end of the trip.
Therefore, on our return we were most grateful for the assistance of
various members of the faculty in gently pointing us in different directions
which proved to be pivotal. I have attempted to bring together various
different sources of data in the study of the individual rock types.
Limestone diferention between facies variations was exceedingly difficult
in the field. Therefore, it was necessary to use external references these
resources have been the 1994 1:25,000 scale geological map of Torroella
de Montgrí produced by the Servei Geològic de Catalunya. This provided
gives basic framework in the field and also a foundation with which to
begin research upon the return to England. The main tool in discovering
the nature of the rocks was micropalaeontology. The mainstay of this
evidence is the study of the Foraminiferida within the thin sections of
each unit. The most useful resource in this respect was: Loeblich A. R.
Tappan H., Foraminiferal Genera and their classification plates 1988 Van
Nostrand Reinhold.This book gives an accurate correlation and
measuring device. It gave in all cases a link between the framework in
the map and the actual rocks we encountered. This in turn has allowed

us to build up a stratigraphy as well as helping to formulate our ideas with
respect of the structural relationships within the Massif. In addition to all
the less obvious links it gave a very exact view of the palaeoenvironment
during deposition.Chapter 3.1The RocksGrey Limestone3.1.1
LocationThe grey unit occurs at the very base of the limestone
succession. In the area that was mapped the grey unit is found adjacent
to the underlying thrust plane. The unit is best exposed within the study
area on the south slope of Mt. Santa Caterina between the 170-200m
contours. The unit is also supposed to appear on the south slope of
MontPlà, also within the area under study. Evidence for this outcropping
is less obvious and difficult to locate.3.1.2 Age/ThicknessThe grey unit is
thought to be as being from the Turonian stage. Subsequent data has
confirmed this evidence to corroborate this with microfossil data. As for
thickness, the unit appears to be up to 45m thick.3.1.3 Field
DescriptionThis was one of the first units encountered, as with the red
limestone. This unit was grey on the surface and slightly darker when a
fresh surface was made. As with the red unit it effervesces on the
application of dilute hydrochloric acid, thus showing it to be of carbonate
nature. Another correlation to the red unit was the fact that veining
increased in coverage, the closer you get to the North-South faults. It
should be noted that most of the information about grey was collected on
Mt. Santa Caterina. The unit was for the most part very accessible there
because of paths made by tourists/shepherds over recent years. The
grey was no different to the other units in as much as it has been
attacked by surface erosion. This has left it in the early stages of
karstification. The grey did not have many joints within it therefore it was
nearly impossible to measure the dip/strike. The grey unit is cut by two
faults with north east south west orientation in Mt. Santa Caterina.3.1.4
OrientationThe few dip/strike readings showed the grey to have a dip
direction opposite to that of the red. In this bed there was evidence of an

an