Department of Geology MSc Geoscience and Environment Field “Geological Processes in Lithosphere and Environment’’
STRATIGRAPHIC STRUCTURE OF MESOZOIC WITH EMPHASIS AT SENONIAN LIMESTONES IN ARTA’S SYNCLINE, NW GREECE.
Supervisor: Avraam Zelilidis MSc Student: Eleftherios Georgoulas
PATRAS, 2019 THE THREE MEMBER COMMITTEE
Avraam Zelilidis
Supervisor
Professor at the Department of Geology, University of Patras
Department of General, Marine Geology & Geodynamics
George Iliopoulos
Member of three-member Advisory Committee
Assistant Professor at the Department of Geology, University of Patras
Department of General, Marine Geology & Geodynamics
Pavlos Avramidis
Member of three-member Advisory Committee
Professor at the Department of Geology, University of Patras
Department of General, Marine Geology & Geodynamics
1 ACKNOWLEDGEMENT
I would first like to thank my thesis advisor Professor Avraam Zelilidis of the Department of Geology at University of Patras, for all the knowledge and advice he gave me as well as for the opportunities that helped me discover the subjects the Laboratory of Sedimentology of Geology of Patras deals with.
Secondly, I want to thank George Iliopoulos, Assistant Professor of the Department of Geology at University of Patras, for compiling me in the part of fossil determination and the advices he gave me.
I need to thank Konstantina Karanika, MSc student at University of Patras, for the help and support she gave me and the time she spend aiding me through my Master studies.
Furthermore, I want to thank my fellow students Dimopoulos Nikolaos and Peridis Savvas, also MSc students, for all the good time and ideas we shared and the collaboration we had especially during field work.
Finally, I owe a big thank to my parents, for giving me the opportunity to continue my studies and gain knowledge that will make me one day a reliable Geologist.
2 CONTENTS
Abstract …………………………………………………..………………………… 6
Περίληψη ………………………….……………………………………………….. 7
CHAPTER 1: INTRODUCTION ……………………….……………………….. 8
CHAPTER 2: GEOLOGICAL SETTING OF WESTERN GREECE ……...…. 9
2.1 Geotectonic zones of Hellenides ……………………………………………………… 9
2.1.1. Ionian Zone ………………………………………………..……….………. 11
2.1.1.1 General information ………………………………….………….. 11
2.1.1.2 Lithostratigraphy of the Ionian Zone ………………..…………. 11
2.1.1.3 Paleogeographic evolution of the Ionian Zone …………....……. 14
2.2 Analysis of the Central Ionian Zone ……………..…………………………………. 18
2.3 Analysis of the studied area …………………………………………………………. 20
CHAPTER 3: INTRODUCTION TO CARBONATE SEDIMENTATION ….. 22
3.1 Carbonate series ………………………………………….………………………….. 22
3.2 Environments of carbonate sedimentation ………………………………………… 24
CHAPTER 4: MATERIALS AND METHODS OF ANALYSIS ……...……… 27
4.1 Bibliography ………………………………………………………………………….. 27
4.2 Microfacies Analysis ………………………………….……………………...………. 27
4.2.1 Introduction to Microfacies analysis ……….…………………………….... 27
4.2.2 Lithofacies analysis …………………………..……………….……………. 28
4.2.2.1 Mineral composition of limestones ………………..………..…… 28
4.2.2.2 Components of limestone sediments and limestones ….…..…… 29
4.2.2.3 Non-skeletal grains ………………………………………………. 29
4.2.2.4 Skeletal grains ……………………………………...…………….. 31
3 4.2.2.5 Matrix: micrite and sparite…………….….…………………….. 32
4.2.2.6 Porosity ………………….…………..……………………………. 33
4.2.3 Classification of limestones ………………..……………………………….. 34
4.2.4 Classification of carbonate facies ……………………..…………………… 37
4.3 Determination of Microfossils …………………………………...………………….. 40
4.3.1 Foraminifera ……………………….…………………………..…………… 40
4.3.2 Systematic classification of Foraminifera …………………………………. 42
CHAPTER 5: THE STUDIED AREA – FIELD WORK ……………………… 44
5.1 Introduction to the studied area ………………………………..…………………… 44
5.2 Field work – Descriptions of the sections …………………...……………………… 47
5.2.1 Section 1 ………………….…………………………………………………. 48
5.2.2 Section 2 …………………………….…………….………………………… 50
5.2.3 Section 3 …………………………………………………………………….. 51
5.2.4 Section 4 ……………………..……………………………………………… 52
5.2.5 Section 5 …………………………………………….………………………. 53
5.2.6 Section 6 ……………………..…………………..………………………….. 55
5.2.7 Section 7 …………………………………….………………………………. 59
5.2.8 Section 8 ………………………….….……………………………………… 61
5.2.9 Section 9 …………………………………….………………………………. 64
5.2.10 Quarry ……………………………………………..………………………. 66
5.2.11 Road to Gribovo ………………………………..………………………….. 68
CHAPTER 6: LITHOFACIES ANALYSIS AND AGE DETERMINATION .. 72
6.1 Analysis of the samples and the thin sections of each section …………………….. 72
6.1.1 Section 2 ……………………………………………..……………………… 72
6.1.2 Section 3 ……………………………………………….……………………. 75
6.1.3 Section 4 ………………….…………………………………………………. 76
4 6.1.4 Section 6 ………………….…………………………………………………. 80
6.1.5 Section 7 ………………………..…………………………………………… 82
6.1.6 Section 8 …………………………………………………………………….. 86
6.1.7 Road to Gribovo …………………………………………………………….. 88
CHAPTER 7: DISCUSSION ………………………………….…………………. 93
CHAPTER 8: RESULTS ………………………………………………………… 98
REFERENCES …………………………………………………….…………… 100
5 STRATIGRAPHIC STRUCTURE OF MESOZOIC WITH EMPHASIS AT SENONIAN LIMESTONES IN ARTA’S SYNCLINE, NW GREECE.
Georgoulas Eleftherios a
a University of Patras, Department of Geology, Laboratory of Sedimentology, 26504, Patras, Greece
Abstract
In this diploma thesis, the analysis of the stratigraphic structure of the Mesozoic in the syncline of Arta, with emphasis on the Senonian limestones was carried out. The study area consists of nine (9) sections with a NNE-SSW direction along the new Ionian road from the village of Kambi as far as Ammotopos, a quarry located to the west of the Ionian road and the road connecting the plain with the village of Gribovo to the east, at Xerovouni Mountain, and geotectonically belongs to Central Ionian Zone. Studied outcrops cross cut the major thrust between the Central and the External Ionian Zone and the prospect was the study of the deformation close and far from the thrust. Results have emerged from work in the field as well as from microfacies analysis.
The field-work includes a detailed description of the lithology of the sections and their characteristics as well as the recording of the faults. The intense internal deformation recorded in most of the sections is synchronous to the sedimentation and is owed to the thrust activity. The general dip direction of the deformation is to the SW. A strike slip fault brings the Vigla’s limestones into lateral contact with the Senonian limestones.
From the studied area seventeen (17) samples were collected, and microfacies analysis was carried out, using polarizing microscope in order to identify fossil assemblages and age determination. Four (4) facies zones (FZ 1, 2, 3 & 4) were identified in the same region, i.e. the coexistence of 4 different environments. The above different facies are due to the fault activity that brings into lateral contact different environments. It seems that stratigraphically the environment changes from shallow waters to deep-sea basin, during the sedimentation. Age determination showed that some of the sections have a different age from the ages that the geological map indicates. Especially, for sections 7 and 8, the geological maps states that their age is Late Cretaceous, but our results showed a Lower Cretaceous age. Based on our data, we propose changes in the geological map of I.G.M.E. as well as an additional study of the area.
Key words: Central Ionian Zone, Senonian limestones, microfacies analysis, calciturbidites
6 Περίληψη
Στην παρούσα διπλωματική πραγματοποιήθηκε η ανάλυση της στρωματογραφικής διάρθρωσης του Μεσοζωικού στο σύγκλινο της Άρτας, με έμφαση στους ασβεστόλιθους του Σενωνίου. Η περιοχή μελέτης περιλαμβάνει εννέα (9) τομές με διεύθυνση ΒΒΑ-ΝΝΔ που βρίσκονται κατά μήκος της Ιόνιας οδού από το χωριό Καμπή μέχρι τον Αμμότοπο, ένα νταμάρι που βρίσκεται δυτικά από την Ιόνια οδό και τον δρόμο που συνδέει την πεδιάδα με το χωριό Γρίμποβο στα ανατολικά, πάνω στο βουνό Ξηροβούνι, που γεωτεκτονικά ανήκουν στην Κεντρική Ιόνια Ζώνη. Η περιοχή αυτή επιλέχθηκε επειδή είναι κάθετη στην επώθηση που χωρίζει την Κεντρική και την Εξωτερική Ιόνια Ζώνη και η προοπτική ήταν η ανάλυση της παραμόρφωσης κοντά και μακριά από την επώθηση. Αποτελέσματα προέκυψαν τόσο από την εργασία στην ύπαιθρο όσο και από την μικροφασική ανάλυση.
Η εργασία πεδίου περιλαμβάνει λεπτομερή περιγραφή των λιθολογιών και των χαρακτηριστικών τους καθώς και καταγραφή των ρηγμάτων. Η έντονη εσωτερική παραμόρφωση που καταγράφηκε στις περισσότερες τομές είναι σύγχρονη με την ιζηματογένεση και οφείλεται στην δράση της επώθησης. Η γενική διεύθυνση κλίσης της παραμόρφωσης είναι προς τα ΝΔ. Ένα οριζόντιας μετατόπισης ρήγμα φέρνει σε πλευρική επαφή στους ασβεστόλιθους της Βίγλας και του Σενωνίου.
Από την περιοχή μελέτης συλλέχθηκαν δεκαεπτά (17) δείγματα στα οποία πραγματοποιήθηκε μικροφασική ανάλυση και μελετήθηκαν στο πολωτικό μικροσκόπιο με σκοπό να γίνει αναγνώριση απολιθωμάτων και καθορισμός των ηλικιών. Τέσσερις (4) φασικές ζώνες (φασικές ζώνες ή FZ 1, 2, 3 & 4), δηλαδή συνύπαρξη 4 διαφορετικών περιβαλλόντων. Οι παραπάνω διαφορετικές φάσεις οφείλονται στην δραστηριότητα των ρηγμάτων της περιοχής που φέρνουν σε πλευρική επαφή διαφορετικά περιβάλλοντα. Φαίνεται ότι στρωματογραφικά το περιβάλλον γίνεται από ρηχό σε περιβάλλον βαθειάς θάλασσας κατά τη διάρκεια της ιζηματογένεσης. Ο προσδιορισμός των ηλικιών από την αναγνώριση απολιθωμάτων στις λεπτές τομές έδειξε ότι κάποιες από τις τομές έχουν διαφορετική ηλικία από αυτή που υποστηρίζει ο γεωλογικός χάρτης. Ειδικότερα, οι τομές 7 και 8, η ηλικία τους με βάση τον γεωλογικό χάρτη είναι Ανώτερο Κρητιδικό, ενώ τα αποτελέσματά μας δείχνουν ότι είναι Κατώτερο Κρητιδικό. Με βάση τα δεδομένα μας προτείνονται αλλαγές στον γεωλογικό χάρτη του Ι.Γ.Μ.Ε. καθώς και επιπλέον μελέτη της περιοχής.
Λέξεις κλειδιά: Κεντρική Ιόνια Ζώνη, Ασβεστόλιθοι του Σενωνίου, μικροφασική ανάλυση, Ανθρακικοί τουρβιδίτες
7 CHAPTER 1: INTRODUCTION
This diploma thesis titled "Stratigraphic structure of Mesozoic with emphasis at Senonian limestones in Arta’s syncline, NW Greece" was elaborated for the MSc studies of the Department of Geology of the University of Patras.
During the last 50 years, the Ionian Zone of western Greece has been the subject of an extensive geological investigation (mapping, petroleum and mineral exploration) which has given a lot of information on the structure and the paleogeographic evolution of the basin (Skourtsis-Coroneou et. al., 1995). The Cretaceous stratigraphy of the Ionian Zone first became well known through the study of the phosphoric-bearing limestones that have been traced in the Cretaceous sequences of the eastern boarder of the Central Ionian Zone (Papastavrou, 1981; Papastavrou et. al., 1985). The area of study is situated in the Central Ionian Zone, near the thrust on the boundaries of the External Ionian Zone and the Central Ionian Zone (Figure 2.4). Further study and analysis of the Ionian Zone is of paramount importance and this diploma thesis was planned towards this purpose.
In the second chapter of this MSc thesis, a bibliographic review of the geological status of the Ionian Zone and geology of the study area is made. The third chapter is an introduction to carbonate sedimentology and the fourth chapter introduces us to the microfacies analysis and the classification of limestones and carbonate facies.
In the fifth chapter there is a presentation of all the work done in the field and a detailed description of each section, describing the lithology and recording the faults. In the sixth chapter the microfacies analysis of the samples collected from the sections and the determination of the age of the sections is carried out, through the determination of the microfossils they contain. Determination derives from the identification of fossils in thin sections under the polarizing microscope.
Finally, the Discussion and the Results follow in the seventh and eighth chapter, respectively.
In conclusion, the purpose of this MSc thesis is the study of the stratigraphic structure of the Mesozoic in Arta’s syncline, with emphasis at the limestones of Upper Cretaceous (Senonian limestones). This thesis was based on the field data synthesis but also on the microfacies analysis.
8 CHAPTER 2: GEOLOGICAL SETTING OF WESTERN GREECE
2.1 Geotectonic Zones of Hellenides
Before we begin with the main part of the MSc thesis, I will refer generally to the geological status prevailing in Greece, which includes the Greek mountain ranges. The Greek mountain ranges formed during the Alpine orogenesis and include a series of nappes (Figure 2.1). They are a series of mountains that connects the Deinarides with the Taurides.
Figure 2.1: a. A generalized tectonic map of the Alpine Orogenesis in the southern European region, which shows its Inner and Outer Zones (modified by Dewey et al., 1973, Smith and Woodcock 1982, Coward & Dietrich, 1989). b. Generalized geotectonic map of the Hellenides. The mountains of the Greek area are subdivided into geotectonic zones, each of which consists of 3 elements. These are the certain stratigraphic structure of its sedimentary rocks, its particular lithological characters and its particular tectonic behavior, elements that generally depend on its paleogeographical position. The Greek geotectonic zones presented from the east to the west are (Figure 2.2):
1. The mass of Rodopi 2. The Serbo-Macedonian zone 3. The Perirodopic zone 4. The Axios zone A) The sub-area of Paionia B) The Paikos sub-zone C) The Almopia sub-area 5. The Pelagonian zone 6. The Attico-Cycladic zone 7. The Parnassos – Giona zone
9 8. The Olonos - Pindos zone 9. The Gavrovo - Tripoli zone 10. The Ionian zone (Zone that we are interested in this MSc thesis) 11. The Pre-Apulian Zone or Paxos Zone
Figure 2.2: Geological map of Greece which shows the Geotectonic zones of External and Internal Hellenides and the zone of our study area in the black box (modified by Rondogianni -Tziambaou and Bornovas, 1983; Tougiannidis, 2009; Gurk et al, 2015). The External Hellenides are part of the Alpine mountain range and were created during the collision between the continents of Africa and Eurasia, after the subduction of the ocean of Tethys was preceded. This ocean was then located in the area where the Mediterranean Sea is today and its sybduction began at the beginning of the Jurassic period (Smith 1977, Robertson et al 1991, Ricou et al., 1986). Finally, they are separated from the Deinarides by the fault line "Skoutari-Pec".
Internal Hellenides include a series of isotopic zones to the east of the Deltal Platform. The main feature of these zones is that they have been affected by two orogenetic phenomena, one that occurred during the Lower Cretaceous and a second at the end of the Eocene.
The region of Arta and therefore the study area is structured by formations of one isotopic zone of the Hellenides, the Ionian Zone.
10 2.1.1 Ionian Zone
2.1.1.1 General information
The Ionian zone is one of the four zones that make up the Greek External Hellenides. To the west, the Ionian is enclosed by the Pre-Apulian zone through the Ionian thrust, while to the east by the Gavrovo zone. From a paleographical point of view, the Ionian zone (Aubouin, 1959) was a submarine groove between the underwater ridge of the Apulian Plate (west) and the Gavrovo’s zone (east). Aubouin (1959) had also proposed the division of the zone in internal, central and external zones, an aspect also reinforced by IGSR & IFP (1966). According to Doutsos (1995), thrusts of NW direction that have listric characteristics, interrupted by strike slips (NE direction), such as Lefkada’s and Kefalonia’s, constitute the tectonic regime that characterizes the zone.
2.1.1.2 Lithostratigraphy of the Ionian Zone
At the base of the sedimentary succession in the Ionian zone of NW Greece there are Triassic evaporites, which are overlain by thick Mesozoic carbonates. The sediments of the Ionian zone were originally divided into three basic sequences which correspond to three stages of evolution of the basin (Karakitsios, 2013), a status that changed as we will see. a) Pre-rift stage (the stage before the creation of the trench) b) Syn-rift stage (the stage during the creation of the trench) c) Post-rift stage (the stage after the creation of the trench)
A. Pre-rift stage
This stage is represented by the neritic limestones of Pantokrator, of early Jurassic age. These neritic limestones overlay, through the limestones of Foustapidima (middle – upper Triassic), on the Lower-Middle Triassic evaporites, whose thickness exceeds 3000m (Vakalas, 2003).
B. Syn-rift stage
This stage begins with the deposition of the Lower Jurassic limestones of Louros. These limestones signify the beginning of the subduction of the area, which is expressed by synsedimentary depositional prisms such as Ammonitico rosso, limestones with Filaments and schists with posidonia in the middle and upper Jurassic. Unconformities are very common in the upper parts of
11 the prisms, and there are many and big differences in the stratigraphic thickness of the deposits along the basin (Vakalas, 2003).
C. Post-rift stage
This stage is determined by an unconformity at the basis of the pelagic limestone of Vigla in the lower Cretaceous. The layers of these limestones are thin with bedded cherts. The sedimentation of the limestones during this period is synchronous throughout the Ionian zone. The differences in the thickness of the limestone of Vigla indicate the continuation of the evaporitic background. From the upper Cretaceous (Senonian limestones) to the upper Eocene, the pelagic sedimentation continues and pelagic limestones are deposited in some places with characteristic thin layers. From the middle Eocene until the lower Oligocene, the sedimentation of the submarine fans begins (Vakalas, 2003). The Senonian age is the age that we will emphasize in this paper.
According to Zelilidis et. al. (2015) the Upper Posidonia beds include yellow to green chert-rich intervals 5-10cm thick together with thin-bedded siliceous argillites containing abundant pelagic bivalves and radiolaria. In the lower part, thin intervals of chertified lumachelles occur with large planktonic bivalves (Posidonia) to which the formation owes its name. The formation is about 9m thick. In other places the Lower and Upper Posidonia Beds are separated by some meters of Limestones-with-Filaments, and the total thickness of the succession is up to 150m. The Lower Posidonia beds correspond to the first 41m of the succession. They consist of green to grey marly limestones intercalated with thin-bedded, dark-grey, marly siliceous sand intervals rich in radiolaria and large pelagic bivalves (e.g. Bositra).The formation on the top is dominated by black chert-rich intervals.
The overlying Lower Cretaceous (Berriasian) to Paleogene (Eocene) post-rift sequence is marked by the break-up unconformity (early Berriasian) at the base of the pelagic Vigla Limestones, which is equivalent to the Maiolica facies in Italy (see Cazzini et al., 2015). The outcrops of Vigla Limestones are usually about 180m thick although they may be up to 600m thick in total. The formation consists of thin-bedded grey packstones in rhythmic alternations with chert intervals and shale intercalations. The Vigla Shales Member of the Vigla Limestones Formation consists of limestones with chert intervals and dark grey to green or red shale intercalations. The two uppermost shale horizons are thin (5-7cm) with very low carbonate content (CaCO3 = 6%). The next two shale horizons consist of thin-bedded marly limestones and are followed by 15 shale
12 intervals, each 15-30 cm thick and with a total thickness of 3m. It is not clear whether these shale horizons continue in the subsurface.
Upper Cretaceous (Senonian) limestones, which rest on the Vigla Limestones, comprise two facies: (a) limestones containing Globotruncanidae and fragments of rudists, and (b) microbrecciated intervals with limestones and rudist fragments within a calcareous matrix containing pelagic fauna. This period corresponds to the subdivision of the basin into a central, topographically-high area with reduced sedimentation, and two surrounding talus slopes with increased sedimentation. During the Paleocene-Eocene, erosion of Cretaceous carbonates from both the Gavrovo platform (to the east) and the Apulian platform (to the west) provided the Ionian Basin with a source of microbreccia materials. However, the supply of clastic sediment diminished significantly during the Eocene, especially in the central Ionian Basin. The main depositional facies during this period consisted of platy wackestone/mudstones with Globigerinidae and siliceous nodules, analogous to the Vigla Limestones but lacking continuous cherty intervals.
The overlying Pindos foreland basin succession is dominated by submarine fan deposits. Avramidis and Zelilidis (2001) and Avramidis et al. (2002) showed that during the middle Eocene to late Oligocene, the distribution of submarine fan facies and palaeo-dispersal directions indicate that the northern part of the Pindos foredeep served as an underfilled foreland basin. Conglomerates (inner fan deposits) are restricted to areas near the Pindos thrust front in the internal Ionian Zone. By contrast further from the Pindos thrust front in the middle Ionian Zone, fine- and medium-grained sediments were deposited in outer-fan and basin-plain settings.
According to Bourli et. al., (2019), the status about the Ionian zone has changed and the post-rift stage is included at the syn-rift. The latest and most detailed stratigraphic column that contains the actual thicknesses is shown at Figure 2.3.
13
Figure 2.3: Detailed lithostratigraphic column for the Ionian zone, NW Greece. The syn- and post-rift stages have been replaced with one syn-rift stage (modified from Bourli et. al., 2019).
2.1.1.3 Paleogeographic evolution of the Ionian Zone
The Ionian zone according to Aubouin (1959) and based on the differences between limestone phases per region is divided into three sub-zones from east to west: (a) the external, (b) the central, (c) the external (Figure 2.4).
14
Figure 2.4: Geological map of External Hellenides showing the sub-zones of the Ionian Zone and a red box marking the study area (Zelilidis et al., 2015). According to this widely accepted model, the Internal and External sub-zones correspond to the shallow eastern and western margins, respectively, of the Ionian basin, while the Central corresponds to its middle and deepest part. However, this model does not apply to the entire length of the Ionian zone, since it is indivisible at some parts (e.g. in the geographical area of Aitoloakarnania). In the pre-orogenetic sequence of the Ionian zone, three periods of deposition and evolution of the basin are distinguished according to their different stratigraphic characteristics (Figure 2.5).
15
Figure 2.5: Paleogeographic evolution of the Ionian zone, from the Lower Jurassic to Lower Cretaceous (Berriasian) (Karakitsios, 1992). Legend:(1) Evaporites. (2) Foustapidima limestones. (3) Pantokrator limestones. (4) Limestones of Sinias and Louros. (5) Sequence of sediments deposited during the creation of the rift (Syn-rift formations), (6) Limestones of Vigla.
The first period, before the creation of the trench, is attributed to the period of Triassic - Lias. The first half of this period (Lower - Middle Triassic) is characterized by the deposition of limestones, dolomites and evaporites on a large scale. In the central part of the Ionian zone we have large thick anhydrite and halite depositions, while the absence of the halite by outcrop appearances can be attributed to its dissolution (Underhill, 1989). The exact age of the evaporites is unknown to us, but it is considered to be older than the Ladinian (Karakitsios, 1995). The second half of this period (Middle Triassic - Lias) corresponds to the initial stages of the opening of the Atlantic Ocean and the left-handed movement between Europe and Africa. During this period, carbonate sedimentation occurs, resulting in the deposition of the following formations: Foustapidima limestones, neritic limestones of Pantokrator and finally the equivalent lateral half-pelagic limestone of Sinias and Louros (Renz, 1955).
The second period corresponds to the Middle - Upper Jurassic period and is characterized by the creation of the rift, which affects the Ionian zone (Figure 8). As it is logical, this period is characterized by deep sea formations such as limestones with ammonites (Ammonitico Rosso formation), the lower silicate "shales" with Posidonia, limestones with filaments, and the upper silicate "shales" with Posidonia. The fact that their presence and their thickness are probably not constantly, is due to the existence of grabens and horsts created in the area of the Ionian zone due to the creation of the rift (Karakitsios, 1995).
16 Also, it is most likely that some local diapirisms of the evaporites of Lower Triassic influenced stratigraphic evolution in the lower layers of the sequence. Besides, it should be noted that "shales" with Posidonia are the parent rocks for petroleum production in the area of Western Greece (Karakitsios & Rigakis, 1996). During Bathonian (Middle Jurassic), at the same time as the oceanic opening of the Atlantic begins, the precipitation in the Pindos ocean begins. This process led to the placement of the ophiolites of Vourinos on the Pelagonian microplate, while future ophiolites of Pindos were still part of the Pindus Ocean (Doutsos et al., 1993).
The third period is after the creation of the rift and is related to the period of Cretaceous-Eocene. Between Lower Cretaceous and Lower Senonian, the basin of the Ionian zone is characterized by a sinking caused by the creation of the rift of the previous period. As a consequence of this particular sinking, pelagic thin-bedded limestones of Vigla are deposited containing nodules of cherts that cover the pre-existing relief of tectonic horsts and grabens. The significant fluctuations in their thickness are most probably explained by the preservation of the pre-existing basin geometry and the continuing diapirisms (Karakitsios, 1995). Locally, the limestones of Vigla overcame the Pantokrator's limestones, which indicate the erosion of an important part of the stratigraphic sequence that should have been deposited in the Middle –Upper Jurassic.
The Upper Senonian in the central sub-zone consists of alternations of pelagic and microbrecciated limestones, while in the internal and external sub-area we have a strong presence of brecciated limestones. Classical materials in both cases have as their source the neighboring ridges of Gavrovo (east) and Pre-Apulian (west). The sequence continues with similar lithofacies in the Paleocene - Upper Eocene (Dercourt et al 1977, IGRS - IFP 1966, Fleury 1980).
The sequence of the Ionian zone ends with the presence of turbiditic deposits. However, the passage from carbonate to clastic sedimentation occurs at different times in each sub-zone.
In conclusion, the Ionian zone during its pre-orogenetic evolution from the Triassic to the Eocene changed its paleogeographic character from neritic to pelagic, as opposed to Pre-Apulian and Gavrovo-Tripoli, which continued to receive neritic sediment up until that time.
A total paleographic evolution of the Ionian Zone is shown at Figure 2.6.
17
Figure 2.6: Schematic depiction of the evolution of the Ionian basin from the Triassic to the Miocene (modified from Χριστοδούλου, 1982).
2.2 Analysis of the Central Ionian Zone
The studied area is situated at the Central Ionian Zone, so it is important to analyze the zone more specifically. The zone extends along a NNW-SSE axis and the succession crops out from the Albanian border to the Gulf of Corinth (Figure 2.7).
18
Figure 2.7: Simplified topographic map of Epirus (Western Greece), showing the position of the studied area in the red box (modified by Skourtsis-Coroneou et. al., 1995). According to Skourtsis-Coroneou et. al., 1995, the beds of Vigla Limestone formation consist of yellow to red marly limestones or marly limestones and chert alterations, as well as clay cherts that are usually green and red. The main constitution of the calcareous beds is micrites, boimicrites with foraminifera and radiolaria, and siliceous biomicrites.
The Senonian limestones, or the Clastic limestones, which are the limestones that we are mostly interested in, are mainly microclastic, bioclastic or microbreccias with a micritic matrix, intercalated with micrites and biomicrites. In places, chert layers are observed. The thickness of this layer varies from 100-400m.
The lower beds of the Vigla Limestone Formation contain abundant calpionellids and radiolaria. Planktonic foraminifera made their first appearance in the basin in the middle Albian (lower Cretaceous). The Upper Cretaceous beds of the central Ionian include microfaunas of both foraminifera and radiolaria. The foraminiferal fauna of Campanian-Maastrichtian interval comprises planktonic and benthic species. All species of each age that were examined will be analyzed in a next chapter.
19 2.3 Analysis of the studied area
The study area of this paper is situated in the wider area of Epirus, about 10 kilometers northwest of the town of Arta, as we can see in Figure 2.8:
Figure 2.8: (A) Map of the Geotectonic Zones in northwestern Greece that indicates the study area. (B) The major structures of the Hellenic arc are indicated: HSZ – Hellenic Subduction Zone, AC – Adriatic Collision, KTF – Kefalonia Transform Fault, PT – Pliny Trench, StT – Strabo Trench, VA – Volcanic Arc, NAT – North Aegean Trough, NAF – North Anatolian Fault, (modified by Ntokos, 2017b). The geological structure of Epirus, which is part of the Ionian zone, consists of a series of sedimentary formations, the deposition of which has took place in specific environmental conditions, which prevailed in the area, at certain times.
The development of these formations from bottom to top has as subsequently:
1. Evaporitic series (Triassic age).
2. Carbonate-Silica series (Triassic to Lower Miocene).
3. Series of flysch (Oligocene - Lower Miocene age).
4. Post-Alpine sediments of various compositions.
20 Aubouin (1959) proposes the differentiation of the Ionian basin during the middle Lias. Pelagic conditions prevailed during this time, following the development of an extensive carbonate platform in the area of the external Hellenides, from the upper Triassic until the middle Lias. This progress, was also confirmed by subsequent investigations carried out during hydrocarbons explorations from the IGRS - IFP (1966), which in addition they also accepted horst tectonics, which begins at the end of the lower Lias and develops up to the upper Lias. As a consequence of this tectonism they believe that the precursors of modern anticline structures have emerged from the sea, which are again sinking in their majority during the Cretaceous.
The tectonic structure of Epirus is characterized by a system of anticlines and synclines, with general axes of NW-SE direction which is a consequence of the tectonic disruption that began during the Oligocene period under the influence of the Alpine orogenetic forces. Many of the existing older normal faults acted as reverse faults (Karakitsios, 1988). Due to a strong compressive field during Alpine orogenesis, we have the creation of folds and thrusts. This situation continues, also, during the Miocene period, and as a result we have the creation of more intense folds and many reverse faults. This period is expressed by long-distance NNW-SSE transition faults, parallel to the axes of the anticlines and by newer faults of NE-SW and E-W direction, almost vertical to the previous ones. The result of this tectonic regime is the intense rupture of the rocks, as well as the intensely mountainous topographic landscape that Epirus has acquired, as well as the deep karstification of limestones.
Important role to the formation of the geological and tectonic structure of Epirus has played the underlying Triassic evaporites, the upward movements to the surface of which (due to diapirism), create many times saline structures (typical geological formations), which they may have dimensions of several kilometers and which tend to rise to the surface (BP Co LD, 1971).
The Triassic Evaporites of the Ionian zone were initially submitted to large movements (both horizontal and vertical), mainly during the period of Pindos orogenesis. However, they were reactivated during the Neogene and Quaternary, giving neo-diapirism within the respective sediments (Nikolaou, 1986). Hence, the way of the movement of the evaporites (paleo-diapirisms and neo-diapirisms), contributed substantially to the tectonic evolution, as well as in the current geomorphological configuration of the basins of Epirus including the plain of Arta, as well as the configuration of thickness of the neogene sedimentary deposits within these basins.
21 CHAPTER 3: INTRODUCTION TO CARBONATE SEDIMENTATION
3.1 Carbonate series
This chapter aims to make an introduction to carbonate sedimentation as well as to the environments in which carbonate sediments and limestones are formed, with particular emphasis on the conditions prevailing during their formation. Determination of the depositional environment of the carbonate sediments is done via the Microfacies Analysis which will be analyzed in a following chapter. The Microfacies Analysis is the description and collection of all Sedimentary and Paleontological data of thin sections (Flügel, 2004, Figure 3.1).
Figure 3.1: Two examples of thin sections analyzed by the Microfacies Analysis method, (A) on the left an example of a thin section of Paleocene (sample D3) and (B) on the right an example of a thin section of Cretaceous (sample D2). Although sedimentary rocks form only 5% of the Earth's outer crust, ¾ of the surface of the continental platforms and an even greater proportion of the surface of the underwater basins, consist of a rather thick layer of sediments. Sedimentary rocks are classified into 3 categories: clastic, chemical and biochemical.
Among the most important sedimentary rocks are limestones (or carbonate rocks in general), which belong to chemical or biochemical sediments, depending on whether they are formed from materials that are precipitated by the organic world (animal or plant). These rocks are very interesting for many reasons, as they are the most important part of geological recordings and fossil recordings that give us information about the life of the planet. Most important, however, is that they make up 40% of the world's hydrocarbon reservoirs. They are also deposits of basic metals, groundwater and first materials. No other type of rock is so economically interesting.
22 Carbonate rocks are of particular interest for the diversity of their origins. Most limestones are of biogenic origin and the estimation of biological and paleobiological factors is necessary to assess their formation conditions. Also, most limestones are derived from the deposition of skeletal grains or the precipitation of inorganic CaCO3 sediments in the depositional environment under suitable conditions. The factors that control carbonate sedimentation are four: geotectonic environment, climate, light and temperature, and nutrients.
The geotectonic environment basically determines the type of the environment of carbonate sedimentation, as well as the inland topography and the intensity of river discharge. It, therefore, controls one of the primary requirements of carbonate sedimentation, which is the absence of silicoclastic material. It is known that that material, apart from dissolving the carbonaceous material, also plays a damaging role in the production of carbonate material, especially in the production of corals.
The climate determines water circulation, temperature, salinity, nutrient supply, turbulence, and the intensity of storms, tidal currents and waves. For example, small-scale marine carbonate sediments can be deposited anywhere, of course, if we do not have deposition of continental classical material. The areas where the optimum of the carbonate sedimentation is achieved are areas poor in clastic material but with high biological productivity. This phenomenon is observed at low latitudes, mainly around 300o, on both sides of the equator. The growth of coral and green algae, which, as is known, are important carbonate producers, is favored only in warm tropical waters. On the contrary, mollusks and calcareous red-alga are more resistant and survive, creating remarkable deposits, up to very high (76oN in Arctic Norway) latitudes.
Alterations in environmental conditions, such as temperature and/or vitamins, may cause a change in stratigraphic distribution and facies architecture, if and as long as they affect the biological system. The most critical factors that affect the organic world and accordingly favor the development of some organisms are temperature and salinity.
The reaction that causes the sedimentation of the calcium carbonate is the following:
+ - (1) CO2 + H2O ↔ H2CO3 ↔ H + HCO3
-2 2+ (2) (HCO3) + Ca ↔ CaCO3(s) + CO2 +H2O
The precipitation of CaCO3 is mainly controlled by the temperature. In particular, the solubility of
Ca and CO2 is increased in cold waters and that results in an increase in their saturation by increasing the temperature. The second factor in controlling the precipitation of CaCO3 is the 2- reduction of CO2 which leads to an increase in pH and increase in CO3 . Decreasing CO2 is the
23 most important factor in Ca precipitation. The release of carbon dioxide is indicated in turbulent waters with high current turbulence such as waterfalls and fast and steep rivers.
As it is known, for the understanding of the deposition conditions of the old carbonate formations, data and observations are used from areas of modern carbonate sedimentation, such as the Bahamas platform and the Persian Gulf. It is obvious that it is not always possible to interpret the deposition conditions of the old carbonate formations taking into account only the data of modern sedimentation and this is because the conditions of sedimentation in the various geological periods vary. This differentiation reflects the mineral composition of the formations, with the result that modern carbonate formations differ mineralogically from the older ones (Flügel, 2004).
3.2 Environments of carbonate sedimentation
Carbonate sediments are formed both on land and sea. They are formed in the following main points: on the shore, in the transition between land and sea, as well as in shallow and deep waters except the very deep oceanic areas (below the Carbonate Compensation Depth level). Today only 10% of marine carbonate sediments occur in shallow waters. Figure 3.2 shows in simple form the main carbonate sedimentation environments starting from the left with the non-marine environments ending right into the deep sea environments.
Figure 3.2: Simplified model of carbonate sedimentation environments (Modified by Flügel, 2004). Consequently, Continental carbonate sediments originate from terrestrial and aquatic environments without marine influence. In particular, they are formed in sub-atmospheric exposure conditions and in submerged aquatic environments. Non-marine carbonate sediments formed under sub- atmospheric conditions include pedogenic carbonates, palustrine carbonates, cave carbonates, eolian carbonates and glacial carbonates. On the other side, carbonated sediments deposited in non-marine
24 but aquatic settings are carbonate sediments of fresh water such carbonate sediments that come from lakes and rivers.
Another environment of carbonate sedimentation are the Transitional Depositional environments (continental-marine), such as deltas, shores, estuaries, lagoons, tidal flats and others, which we find in shallow areas near the coast, especially at the boundary between continental and marine deposition. Characteristic of these environments is their high instability resulting from the interaction of high energy forces associated with waves, tide, wind and continually changing sea levels.
Continuing, the criteria commonly used for separating shallow sea environments (envelope-neritic zone) from deep sea environments (pelagic or oceanic zone) are "the shelf break" and the bottom of the breeding zone (Figure 3.3). Another criterion is the storm base. Shallow marine environments are within the bathymetric boundaries of the continental shelf environment (from the coast to about 200m). Ramps and platforms as well as reefs are environments of carbonate sedimentation and are characterized by shallow water deposits. Specifically, with the term platform, we describe carbonate deposits of shallow water with flat peaks but also steep slopes created by the deposition of carbonate precipitate either on the margins or the continental shelf or the ocean bottom. Generally, the term platform is a very general term that includes margins ramps as well as the various categories of platforms, especially for cases that are not easily categorized. There are six main types of platform: 1) platform with margin, 2) mild inclination platform, 3) continental platform, 4) isolated platform, 5) abruptly submerged platform, and, 6) oceanic atols (Flügel, 2004).
Figure3.3: Zonation of the ocean (Encyclopedia Britannica, 2010). Deep-sea environments may include part of the continental shelf, starting from the point adjacent to the continental margins up to its base (deeper limit), the continental slope, the abyssal plains, mid-
25 ocean ridges, the oceanic and the volcanic "mountains", as well as the ocean trenches. Deep marine environments may also include parts of the deepest area of peri- and epi- continental margins, as well as the outer part of the ramp under the waving base and the base of the storms, as well as below the bottom of the breeding zone, which corresponds to a depth of >200m.
Finally, for a long time, the dominant view was that carbonate deposits are mainly confined to tropical climates with warm waters. However, carbonate sedimentation can occurs in all latitudes with hot to cold waters and can be distinguished in carbonated sediments of tropical (warm-water carbonates) and temperate-water. Modern "non-tropical" carbonate deposits are observed, at tidal levels and on platforms, as well as along the continental shelf.
In conclusion, the following figure gathers almost all the carbonate sedimentation environments, in order to have a more complete schematic view (Figure 3.4).
Figure 3.4: Main carbonate depositional environments (from Stanley, 2009).
26 CHAPTER 4: MATERIALS AND METHODS OF ANALYSIS
The MSc thesis developed in the following study stages:
4.1 Bibliography
The first stage included mainly a bibliographic exploration on the following topics: (a) Paleotectonic and paleogeographic status of the Ionian zone, (b) Analysis of microfacies and phasic zones, (c) Microfossils and definition of foraminifera and (d) possibilities of exploiting the results.
4.2 Microfacies analysis
Subsequently, seventeen (17) thin sections were prepared for Microfacies analysis in a polarizing microscope.
4.2.1 Introduction to Microfacies analysis
The microfacies analysis compiles all sedimentary (lithofacies) and paleontological elements (biofacies) that can be described in thin sections. It provides information that cannot be given by the simple macroscopic observation with regard to the conditions of deposition and the conditions of diagenesis (Brown, 1943). Specifically, the Microfacies Analysis:
Describes carbonate deposits in a variety of marine and terrestrial environments as well as carbonate deposits of tropical and non-tropical waters, Analyzes the conditions of deposition and diagenesis of carbonate rocks, It presents diagnostic features and underlines the importance of Microfacies analysis criteria, Emphasizes the importance of biological factors that control carbonate sedimentation and provides an overview of the most common fossils found in thin sections made from limestones, Combines diagenetic processes with dolomite and porosity, It is of great importance to the creation of stratigraphic sequences and deposition models, It is an important tool in distinguishing palaeoclimatic changes and in archaelogical research as well, It separates the depositional conditions of the basin-platform, Finally, it is a very important tool in the assessment of limestones either as source rocks or as reservoirs.
27 4.2.2 Lithofacies analysis
Lithofacies Analysis of Carbonate Rocks is defined by the texture and composition of the limestone components, made by observing thin sections combined with macroscopic observation. The natural arrangement of these components, including texture and structure, is a texture that reflects the depositional conditions as well as the conditions of carbonate rock diagenesis. Most structures reflect depositional environments as well as early diagenetic processes. It should be noted that Microfacies analysis, and consequently the lithofacies analysis, is based on a small scale analysis of thin sections.
4.2.2.1 Mineral composition of limestones
The main components of limestones are calcite, aragonite and dolomite, the most important characteristics of which are given in Table 1. According to Milliman and Folk (1974), the main parameters determining the formation of carbonates are as follows:
Aragonite: water with high content in Mg, high water temperatures (between 20 and 30°C), high pressure, high pH, presence of Sr and probably Ba and Pb.
Calcite: very low concentrations or absence of Mg, low water temperatures (about 10°C), low pH, presence of Na2CO3 and (NH4)2CO3.
Dolomite: high ratio of Mg / Ca (> 5), high water temperatures (generally> 30°C).
Table 1: Crystallo-Chemical analysis of the main carbonate minerals.
28 4.2.2.2 Components of limestone sediments and limestones
Τhe basic purpose of the petrography of limestones is to classify them, in order to be compared to modern carbonate sediments. First of all, it should be known that limestones have two major differences from modern carbonate sediments.
Their first difference is obvious. The limestones have become compact, while the sediments are still sediments. The second difference concerns their mineralogy. Modern sediments consist of aragonite and calcite rich in Mg (>4 mole% MgCO3). Because, however, under normal diagenetic conditions, aragonite and Mg-rich calcite are unstable, they immediately migrate to poor Mg calcite (<4 mole% MgCO3). All three of the aforementioned mineralogical phases can be substituted by dolomite, and for this reason most of the limestones of the geological record consist of Mg and / or dolomite poor calcite (Pomoni-Papaioannou, 2005).
The main components of limestones are 3:
- Grains: skeletal and non-skeletal grains - Matrix: micrite andsparite
4.2.2.3 Non-skeletal grains
According to Zoumpouli (2016), as non-skeletal granules we characterize those that are not derived from skeletal material of microorganisms. There are four (4) types of grain in this category: coated grains, peloids, grain aggregates and clasts. The only category that we came across was the peloids and those will be analyzed thoroughly, for the other categories, just a few things will be mentioned.
Coated grains: The origin of these grains is polygenetic, since they can be formed by different processes and in a variety of environments. Consequently, they can be hardly used in the interpretation of the environment. Two (2) categories are distinguished:
Grains resulting from chemical processes (ooids and pisoids), and Grains resulting from a biogenic process (oncoids).
Grain aggregates: They are created when various carbonate granules (peloids or ooids or bioclasts) are adhered to each other with sparitic or micritic material and microorganisms (cyanobacteria / algae). Their size usually ranges from 0.5 to 3mm and they are irregular in shape. They occur mainly in platform environments, but also in reefs. Often the grains are nothing but small ooids called botryolites. Another category of grain aggregates are algal lumps, amorphous aggregates (lumps) and Caliche aggregates (caliche-lumps).
29 Clasts: Syn-sedimentary or post-sedimentary limestone clasts, reworked partly consolidated carbonate sediments or already lithified material. Shape and size are highly variable and sometimes, very small clasts are hardly distinguished from peloids (Flugel, 2010).
Peloids: Peloids (Scholle & Ulmer-Sholle, 2003) (Figure 4.1) are polygenetic grains in which it is not easy to determine their exact origin, and for this reason the term "peloids" is mainly descriptive. They are small, spherical grains which do not have any specific internal structure. Peloids represent an important component of shallow carbonate sediments and characterize low energy environments. Fecal pellets, algal peloids, pseudopeloids as well as pelletoids are some of the peloid types. Their size varies between 0.02 to 1 mm, commonly 0.10 to 0.50 mm.
Figure 4.1: An example of peloids that were recognized found in a thin section.
30 4.2.2.4 Skeletal grains
Skeletal granules are limestone grains consisting of fragments or entire shells of precipitated organisms. Limestones usually contain a large variety of skeletal granules, which depend, of course, on the geological period and the surrounding environment.
They are therefore an important tool for palaeo-ecological and biostratigraphic analysis and for this reason proper identification of skeletal grains is of great importance for the interpretation of the environment (Pomoni-Papaioannou, 2005).
The size of the skeletal grains ranges from 0.05mm to a few centimeters, but exhibits the same mineralogical instability as the contemporary sedimentation of shallow environments because they consist primarily of Mg-rich aragonite and / or calcite.
Skeletal grains may be many organisms, such as benthic and planktonic foraminifera, ostracods, bivalves, corrals, mollusks etc.
All the above mentioned categories can be included in the Figure 4.2 below:
Figure 4.2: Pivot table of the categories of skeletal and non-skeletal grains (Flügel, 1982).
31 4.2.2.5 Matrix: Micrite and sparite
By the term main mass we call the "binder" material among the largest granules of limestones. The main mass of most limestones often consists of a dense, thin crystalline calcite known as micrite (<4μm). Generally, with the term micrite, we refer to the very finest main mass of carbonate rocks. Micrites can undergo recrystallization into microsparite (5-15μm) or pseudosparite (>50μm). Therefore, due to the recrystallization that usually exists in the limestones, it is advisable to use a specific classification according to the size of the crystals (Figure 4.3).
Figure 4.3: Sizes of the crystals in the matrix of limestones. Another problem with the determination of micrite is its origin as it is polygenetic and due to its subsequent diagenesis it is often impossible to ascertain its origin (Pomoni-Papaioannou, 2005).
For example, at high temperatures and salinities or changes in the partial pressure of CO2, the micrite can be a chemical sediment. It may also have a biogenic origin, as is happens when skeletal particles of Coccolithophoridae or the bio-erosion caused by certain organisms as they grind or bore the carbonate substrate.
In some cases micrite may be of diagenetic origin and in fact represents a form of matrix. Taking into account the ways of genesis of the micrite, Wolf & Conolly (1965) have made a distinction between the primary orthomicrite and the secondary pseudomicrite resulting from neomorphism processes.
32 Sparite is a carbonate material consisting of relatively large crystals that originates either from the filling of pores or from neomorphic recrystallization. Depending on its size, sparite can be divided into sparite and microsparite (Folk, 1959): (a) Sparite is generally characterized by crystals bigger than 10 μm and light translucent crystals, and depending on its origin it is divided into orthosparite (Wolf, 1965), formed as matrix and pseudosparite formed by neomorphic processes (recrystallization, mineral extraction) (Folk, 1965), (b) Microsparite is characterized by sizes generally less than 10 μm and larger than 4 μm, homogeneous crystals and a relatively high percentage of clay or organic substances among the crystals, compared to sparite. According to Folk (1974), microsparite originates from the recrystallization of micritic calcite, which is only possible after removal of Mg2+ ions (Longman, 1977; 1980). Removal of Mg2+ ions is due either to fresh water inflow or to their adsorption on clay minerals.
4.2.2.6 Porosity
More than half of the hydrocarbon deposits are contained within the limestone and dolomite rocks, and so the amount and the type of porosity play an important role in the study of limestone rocks (Zoumpouli, 2016). According to the definition, the porosity of a rock represents the ratio of total porosity to total rock volume (%). Porosity can be classified as primary, if it is formed upon deposition of the rock, or secondary when created after the deposition. According to the classification of Choquette & Pray (1970), porosity can be distinguished in: a) Fabric selective porosity that its location is controlled by particular parts of the depositional or post-depositional fabric of the rock and maintains the histological features of the rock such as:
Interparticle porosity that occurs during deposition of sediments Intraparticle porosity due to the internal primary microstructure of the skeletal grains Intercrystal porosity (secondary porosity) Mouldic porosity due to grain dissolution is a secondary porosity that develops after the grains have dissolved Fenestral porosity of drying is due to the creation of window type cavities. Shelter porosity where it is created under allochemical components. Growth framework porosity where it develops from skeletal growth of organisms.
(b) Non-fabric selective porosity, which does not retain primary texture and cuts across the fabric of the rock:
Porosity of fractures (fracture porosity)
33 Porosity of channels (channel porosity) Porosity of small cavities (vuggy porosity) Porous of caves (cavern porosity)
(c) Intermediate porosity, Fabric-selective or not, whether or not retaining primary texture:
Porosity of lamination (breccia) Boring porosity Burrow porosity Porosity of shrinkage
A table below shows schematically the various porosities (Table 2):
Table 2: Classification of porosity in carbonate sediments. Porosity is dark blue (Modified from Choquette and Pray, 1970; Adams & MacKenzie, 1998).
4.2.3 Classification of limestones
Several classifications, morphological and / or genetic, have been formulated for the classification of limestones, which emphasize specific properties such as color, crystals size, texture etc. Generally, the classification is based on the granulometric and textural properties of the rock (Pomoni-Papaioannou, 2005).
34 The main target of the classification is the interpretation of the depositional environment of the limestones. Each microfacies type or paragenesis of various microfacies types gives us information about the energy of the environment during their formation. Therefore, the most appropriate classification would be the one that combines the characteristics of limestone with some environmental parameters such as energy level. Therefore, for each thin section of this MSc thesis was performed textural classification according to Folk (1962) and Dunham (1962), while the classification of microfacies and facies zones was done according to Wilson (1975) and Flügel (1972; 1982) (Pomoni-Papaioannou, 2005).
This classification system of Folk (1959) is based on the fact that limestone rocks consist of: a) skeletal grains, b) non-skeletal grains (bioclasts/fossils, oolites, pellets/peloids and intraclasts) and c) the matrix (Figure 4.4).
Figure 4.4: Graphic classification table of limestones (Modified from Folk, 1959, Fig A). Folk’s classification (1959) is not just about classifying a rock; it also gives us an estimate of the energy levels of the depositional environment. For example, a biomicrite or packed biomicrite indicates a low-energy environment where the energy of currents or waves was low to remove matter. In contrast, a well-classified biosparite suggests a high energy environment (Figure 4.5).
35
Figure 4.5: Carbonate textural spectrum from Folk. The left part of the figure, represents low energy sediments, while the right part high energy sediments (Modified from Folk, 1962, Fig.4).
Although the classification of Folk (1959) is widespread, the Dunham classification (1962) is more useful (Figure 4.6). This classification is based on the rock's texture as well as on the presence of organogenic structures. According to this classification of limestones, we have the following four basic subdivisions: (a) mud-supported (mudstone, wackestone), (b) grain-supported (packstone, grainstone), (c) organogenic limestones, and, (d) crystalline limestones. Figure 4.6 is a schematic representation of the basic types along with their subclasses.
A characteristic of this type of classification is the direct relationship of each type of rock with the energy level. For example, mud-supported limestones (mudstone, wackestone), reflect deposits in a low energy environment where the mud between them is not washed away. On the contrary, grain- supported limestones (packstone, grainstone) reflect deposits of high energy environments (Pomoni-Papaioannou, 2005).
36
Figure 4.6: Classification of Carbonate rocks according to depositional texture, modified from Dunham (1962, Table 1) and Embry & Klovan (1971).
4.2.4 Classification of carbonate facies
The classification and interpretation of carbonate facies is not an easy task. To achieve this, various factors are taken into account, such as lithology, texture, color, species and percentage of fossils, types of grains and fossils, and diagenetic factors.
The term "lithofacies" refers to a rock, whether it is a layer or part of a layer and is determined by its natural and sedimentary characteristics. Similarly, the term “biofacies” is based on palaeontological differences.
According to (Pomoni-Papaioannou, 2005), lithofacies are the result of a particular depositional environment and may have undergone a variety of modifications during early diagenesis. Frequently, diagenetic processes affect the primary structure of a lithoface to an extent that it does not become more recognizable. In a carbonate sequence, lithoface can be repeated several times. However, we cannot come up with an interpretation of the environment taking into account one individual lithoface. For this purpose, the phenomenon called Paragenesis of Lithofacies should be taken into account. In this sense, paragenesis of lithofacies is a group of lithofacies, which are found
37 together in a particular part of the carbonate sequence (usually 1-2 meters) and are considered to be genetically and environmentally related.
Wilson (1975), using the observations from the study of the Holocene sedimentation, proposed a system with 26 standard microfacies (Figure 4.7). Each one of the microfacies has a specific texture that is somehow a diagnostic of a particular environment. But there are exceptions, where a microfacies type responds to more facies zones. The facies to be studied are compared to Wilson's standard microfacies and thus approach the interpretation of the environment.
Figure 4.7: List of Standard Microfacies Types and Facies Zones. The order of the SMF numbers follows approximately the order of the Standard Facies Zones in the Wilson Model going from the basinal SMF Type 1 to SMF 26 that characterizes subaerial exposed areas (Flugel, 2004). In the Wilson model there are 10 standard Facies Zones (Figure 4.8). Starting from the open deep basin and going along of the slope to the margins of the platform, we reach at the inner platform and then on the coast (Figure 4.8). Facies zones are clear to be idealistic models, which, they usually do not correspond to reality. For example, the geological record proved that it is possible to develop a platform even straight on zones of deep sedimentation. Often only the bands appear 5 and 6 of the platform and the zones 7, 8 or 9 are absent. The model of Wilson responds only to tropical environments, especially to marginal platforms (Figure 4.8). It does not respond, though, to cold environments in which the development of ramps without margins is favored.
38
Figure 4.8: Distribution of SMF Types in the Facies Zones (FZ). Nearly all facies zones are characterized by assemblages consisting of several SMF Types. FWWB stands for Fair-Weather Wave Base and SWB for Storm-wave Weather Base (SWWB) (Modified from Flugel, 2004). As a result from Figure 4.9, the following Table 3 shows briefly which SMF types can be found at each FZ.
Table 3: A table containing all FZ and SMF and to which FZ the SFM correspond. FZ 6, 7 and 8 seems to contain the higher density.
39 4.3 Determination of Microfossils
The dating of the carbonate sedimentary rocks in the study area was based on the study of the microfossils that are encapsulated in the samples. Small fossils are petrified animal fossils (Foraminifera, Radiolaria, Ostracods etc.) or plant organisms (Diatoms etc.) or petrified microscopic parts of larger organisms (sponge needles, etc.).
Microfossils are studied from material collected either from surface horizons by sampling stratigraphic sections or from sub-surface horizons. In both cases, the initial work concerns the gathering of existing data (e.g., tectonic structure, stratigraphic position, sedimentation rate), which will help to assess the research needed and identify the appropriate sampling site.
The preparation of the material for the study of microfossils is carried out by preparing samples in laboratories with the appropriate equipment and qualified personnel. The treatment varies according to the composition of the micro-paleontological content as well as the characteristics of the rock. If they are loose, not solid, such as siliceous rocks, the separation of microfossils from the rock is easier and gives them their entire shells, while solid rocks have to be cut into thin sections to study the microfossils. In any case, the methodology followed is in line with international standards on similar issues.
In the case of hard rock, such as limestones, thin sections of 30μm thick are produced, with a cutting and abrasive machine and so, permanent thin sections are made. More specifically, from each rock sample, a 50 x 75 mm tile is cut and solidified. When the whole process is completed, thin sections are studied in a polarizing microscope.
Thus, for the studied area, consisting of solid limestones, a total of 17 thin sections were prepared and examined, in order to strengthen our work. The study of the microfossils was performed on a polarizing microscope using lenses of the order of 2.5 x 10 and 5 x 10 where it was necessary.
4.3.1 Foraminifera
Microfossils are a very important part of sedimentary rocks and especially of carbonates, providing many and important information on biostratigraphy, paleoecology and hydrocarbon field study. The credibility of microfossils can be the best test field for numerous evolutionary studies.
The micropaleontological analyzes are mainly based on the study of foraminifera and this is why foraminifera are the most important group of microfossils for many reasons, such as their tiny size, their abundant presence, their wide geographic spread to sediments of all ages and their appearance
40 in almost all marine environments (Figure 4.9) (Todo et al., 2005). The same appears at the study area in which both planktonic and benthic foraminifera have a strong presence.
Figure 4.9: Marine microfossils appear in the sediments since the Precambrian until nowadays and live in all marine areas and environments (Encyclopedia Britannica, 2010). The foraminifera are unicellular organisms, marine and only a few of their representatives live in brackish waters. Their size varies from a few μm to a few cm. They live either free in surface waters such as pelagic organisms (planktonic foraminifera) or attached or free near the seabed (benthic foraminifera). Some of them live freely at the young stage of their lives and later adhere to various backgrounds. The foraminifera are known from the Cambrian to nowadays. Approximately 30.000 species of foraminifera have been described, most are known only as fossils. It is likely that they existed in Pre-Cambrian, while the age of the first planktonic foraminifera is Middle Jurassic (Schiebel & Hembleben, 2005).
All petrified species, and most living species are known mainly by their shells, while knowledge of the organism, life cycles, and their behavior is known in less than 50 species. For this reason, their classification is based on the characteristics of their inner wall, their chambers, the shape of their shell and the position of the mouth opening.
Foraminifera are the best biostratigraphic and palaeo-ecological indicators (Loeblich, 1988), which can be used in addition in statistical analyzes, for both the large number of their species and their abundance in the various sediments due to the easy maintenance and recognition of the shell. For these reasons, foraminifera are the most used fossil organisms for biostratigraphy, identification of geological age, sediment correlations, and paleo-environmental interpretations, or as organisms that
41 represent ecological data or as shells whose minerals provide geochemical features that record past temperatures, expansion of glaciers and other paleogeographic data. They are considered to be one of the main groups of biogenic carbonate sedimentation.
4.3.2 Systematic classification of Foraminifera
According to Zoumpouli (2016), the classification of the foraminifera is based on the characteristics of the shells due to easy diagnosis and conservation. Below there is an image of the characteristic shells of the benthic foraminifera (Figure 4.10).
Figure 4.10: Some common external shapes and chamber arrangement patterns in foraminiferal tests. Some organisms follow a single test construction pattern throughout their life; others can change patterns during their life cycle (Scholle, 2003). Most foraminifera have shells with a diameter of <500μm. Based on the structure, the shell is distinguished in: microgranular compound, porcelaneous, hyaline radial, hyaline oblique, hyaline intermediate or hyaline compound (Figure 4.11). It should be noted that most foraminifera are multi-chamber.
Figure 4.11: Diagrammatic view of the main types of secreted calcareous wall structures of foraminiferal tests. The dashed lines represent the c-axis orientation of constituent microcrystalline calcite crystals in hyaline wall structures. The lamellar growth structure of most hyaline tests is not illustrated here (Scholle, 2003).
42 Until today, 1,500 genus of foraminifera and about 30,000 species have been described, of which 4,500 are recent. For the purposes of identification of the family, into account should be taken the following: (1) whether it lives freely or attached, (2) the material and structure of the shell, (3) the layout and number of chambers, (4) the shape and position of aperture, and (5) the internal structure of the shell.
Thus, the determination of the genus and the type of the foraminifera in thin sections using a polarizing microscope is based on the description of the following characteristics: (A) the size of the shell, (B) the nature and structure of the shell, (C) if they are ornamented, (D) shape and the number of chambers, (E) the type and shape of the sutures, (F) and the position of the aperture (Boudagher-Fadel, 2008). These diagnostic characteristics are relatively difficult to observe and be interpreted in detail in thin sections, as their description depends on the cutting orientation of the thin sections and the shells.
The classification of the foraminifera in the study area was done according to the systematic classification of Loeblich & Tappan (1988).
43 CHAPTER 5: THE STUDIED AREA – FIELD WORK
5.1 Introduction to the study area
The area of study is located about 10 kilometers northwest of the town of Arta (Figure 5.1 a,b) and is part of a continuous carbonate sequence of the Upper Cretaceous, which for ease of convenience was studied in 2 sections, those crosscutting the thrust and those with parallel direction to the thrust plane. The aim is to record the differentiations of the Cretaceous sediments.
During field work, based on I.G.M.E. sheets with scale 1:50,000, carbonated sedimentary rocks were identified and studied along the Ionian Road from the village Kambi to Ammotopos and then until the village of Gribovo (Figure 5.1 c). More specifically, the rocks that we mainly studied were limestones of Vigla and the Senonian limestones, in other words limestones of Cretaceous of the Central Ionian Zone.
Figure 5.1: (a) Map of Greece and of the studied area is indicated, (b) Map of the studied area and the area of Epirus, (c) Map of the studied area, where are indicated the Ionian road and the road to Gribovo village (1), the two areas under study (taken from Google Earth). The sections located along the Ionian Road have a NNE-SSW direction and were studied in a total of 9 sections (Fig. 5.2). We also visited a large Quarry (Fig. 5.2) located in the area in order to get some additional information that will help us reach our conclusions. The other section is the road connecting the plain with the village of Gribovo, which has in general an E-W direction (Figure 5.3). It was studied as a single section.
44 In total, 26 samples of rocks were collected from the 2 sections, 19 from the sections along the Ionian road and 7 from the road to Gribovo. From the collected samples, a total of 17 thin sections were prepared, 13 from the section along the Ionian road and 4 from the other, for the purpose of their microfacies analysis. The thin sections were studied under a polarizing microscope and classified according to the taxonomic patterns of Dunham (1962) and Folk (1959).
Detailed microfacies analysis was then performed according to Flügel (2004), Wilson (1975) and Embry & Klovan (1971).
Figure 5.2: Detailed map of the main section along the Ionian Road showing the 9 positions that were examined. It shows also the quarry on the western side of the area (taken from Google Earth).
Figure 5.3: Detailed map of the road that connects the plain with the Gribovo village. The dots indicate the sampling locations for the samples D14, D16, D18 and D20 (taken from Google Earth). The studied area and the sampling locations are shown in the following geological map (Figure 5.4), which is a combination of the I.G.M.E. sheets of Arta and Thesprotiko with scale 1:50,000.
The tables below the geological map include the coordinates of every section (Table 4) and the coordinates of the samples (Table 5), according to the projection system GGRS '87.
45
Figure 5.4: Processed geological map of I.G.M.E. in which the sections are shown and with A, B is the Ionian road and the road to Gribovo, respectively (I.G.M.E. sheets of Arta and Thesprotiko).
Table 4: Table with the coordinates of the beginning and the end of every section.
46
Table 5: Table with the coordinates of the samples.
5.2 Field work- Descriptions of the sections
The study area from afar (Figure 5.5) shows what will be analyzed in the following chapters, that are the graben created between the 2 mountainous volumes, which has a NNE-SSW direction and extends to the village of Ammotopos in the north.
Figure 3.5: A panoramic photo of the study area showing the relation of the strike slip and the thrust, and in which sections 4-8 are shown. The strike slip has a NNE-SSW direction, parallel to the positions shown. The arrow shows the graben created between the 2 mountainous volumes, which, as we shall see later, have different lithology. Due to the fact that the layers have a general dip direction to the south-west, we believe that the stratigraphically lower parts are located at the northern part of each section.
47 5.2.1 Section 1
The length of this section is about 240 meters and its maximum height exceeds 10 meters. The orientation of section 1 is E-W; it switches to NNW-SSE until it reaches N-S. The section is structured by 2 sections, one with E-W direction (section 1A) and one with N-S direction (section 1B). In the E-W direction part, the contact of an undisturbed block and a damaged fault zone of about 30 meters length are shown. The sediments of the undisturbed block, according to the geological map, belong to the Upper Cretaceous (Senonian limestones). They are thin-bedded microbrecciated limestones, white-gray in color and do not show internal deformation. From section 1B to section 9, everything is deformed. Section 1B is the northernmost part from which the description of intense deformation begins within the studied sediments. This discontinuity occurs due to a fault and is shown in Figure 5.6.
Figure 5.6: The contact of the undisturbed blocks, of Late Cretaceous age, with the zone of intense fragmentation ending in the graben formed between the 2 mountainous volumes. The dip of the undisturbed blocks that appear is the apparent, with the actual being an WNW direction, without a numerical value. The legend is representative for all the following figures. This section is at the crossing of the strike slips and the thrusts. It is evident that because of the thrust, the Senonian sediments tend to lie over the very fragmented rocks. The strike slip has a NNE-SSW direction, parallel to the graben created between the 2 mountains and continues to Ammotopos (Figure 5.7).
48 Due to the observed tectonic activity sediments with an N-S strike-slip (1B) receive the compression and therefore several folds are observed (Figure 5.8).
Deformation of rocks continues until the end of section 1B. The axis of deformation has a dip direction of 175°/355° (Figure 5.9).
Figure 5.7: Geological map showing sections 1A and 1B of section 1, as well as the crossing of the strike slips and the thrust (modified from Thesprotiko sheet of I.G.M.E.).
Figure 5.8: A photo showing the rock deformation and presence of folds at section 1B with NNW-SSE direction.
49
Figure 5.9: Intense deformation in the sediments with 175°/ 355° deformation axis.
5.2.2 Section 2
The length of this section is about 30 meters and its maximum height is 3 meters. Layers of section 2 have dip and dip direction, respectively, 178°/60°. The sediments of this section consist of microbrecciated thick-bedded limestones, gray in color. They are heavily fragmented with many cracks of different directions, due to the intense tectonic activity that influenced the area. The northernmost part of the section has a NNE-SSW direction while as we head south, the orientation is N-S. A stratigraphic column of section 2 as well as the parts from which sampling was performed are shown in Figure 5.10.
Figure 5.10: Stratigraphic sequence of section 2 and sampling positions of samples D1 & D2.
50 5.2.3 Section 3
Section 3 of the study area is about 875 meters south of section 2 and is about 120 meters long. Its orientation is NNW-SSE. The dip ranges from 52° to 80° and the height of the section exceeds 5 meters.
From the stratigraphically lower to the upper part, this section consists of 10-meter-thick thin- bedded microbrecciated limestones. Over them, there are 4 meters of medium-bedded microbrecciated limestones, followed by 6 meters of thin-bedded microbrecciated limestones. For 1 meter, we have alternations of gray-white thin-bedded and medium-bedded microbrecciated limestones. The dip and dip direction, respectively, is 106°/80°.
Over them, there are 5 meters of medium-bedded microbrecciated limestones with dip and dip direction, respectively, 161°/70° and at the end of section 3, at the upper stratigraphic point, there are 4 meters of thin-bedded microbrecciated limestones with dip and dip direction, respectively, 085°/52°. From this position we took sample D3. A stratigraphic column of section 3, as well as the sampling position of sample D3 is shown in Figure 5.11
Figure 5.11: Stratigraphic sequence of section 3 and sampling position of sample D3. The top photo is about the upper stratigraphically part of the section, while the photo below of the 1-meter-long alterations of thin- bedded and medium-bedded grey and white limestones.
51 5.2.4 Section 4
Section 4 of the study area is about 320 meters long, while the height of the section exceeds 12 meters. Its orientation is NNE-SSW.
Starting from the northern and stratigraphically lower part of the section, medium-bedded microbrecciated limestones, white-gray in color are observed and which are strongly damaged with dip and dip direction, respectively, 020°/75°. They have a 27 meters length, and then, above them for the next 26 meters, the sediments dip is 164°/82°. Deformation is intense as shown in Figure 5.12.
Figure 5.12: Intense deformation of rocks, which, as shown by the 2 shaded polygons, shows a different direction and dip. This deformation alters the thickness of the particular horizon. Where the thickness decreases, the layers are better organized, while on the contrary, where the layers are thick, the layers have compact bedding. For the next 35 meters, the section consists of medium-bedded limestones and has a dip of 115°/35°, while throughout strike slips are interfered with dip and dip direction, respectively, 015°/80°. From there we also collected sample D6, the only sample of section 4. This sequence is interrupted by a strike slip fault.
From this point up to the upper stratigraphically parts of the section (approximately 220 meters), there are folds mainly in the lower visible part of the position with their height in some cases exceeding 6 meters. Several faults, such as a reverse fault, with dip and dip direction 230°/81°
52 (Figure 5.13), appear in places. On either side of the fault, the rocks have dip and dip direction of 235°/50°.
Figure 5.13: In this figure, there is an intense deformation in the southern section and a reverse fault where a 30 cm displacement of the guidance horizons (with a yellow dashed line) is shown. The only thing that changes until the end of the section is that the dip decreases and becomes 280°/65°. It is noteworthy that the upper layers are much more deformed than the layers with the folds, due to the intense tectonic activity and the many faults.
5.2.5 Section 5
Section 5 of the study area is about 330 meters long and its height exceeds 15 meters. Its orientation is NNE-SSW.
Starting from the stratigraphically lower part of the section, the rocks are strongly deformed. As we head south to the stratigraphically upper parts, for a distance of 46 meters and until the appearance of a strike slip, the section consists of medium-bedded and thick-bedded microbrecciated limestones, gray and white in color. The main dip and dip direction, respectively, of the sediments is 263°/55°, while gradually it becomes 154°/75° (Figure 5.14) and reaches 290°/85°. Throughout the sediments, there are a large number of cracks. The fault is a strike slip with dip and dip direction, respectively, 162°/82° (Figure 5.15).
53
Figure 5.14: The dip of the sediments, which is 154ο/75ο. The picture shows the strong deformation, which as seen from the shaded parts, alters the layer thickness.
Figure 5.15: Strike slip with dip and dip direction, respectively, 162ο/82ο. On either side of the fault is not possible to measure the dip.
Then, for the following 28 meters, as far as lithology is concerned, no changes are observed. The main dip and dip direction of the sediments is 300°/73°. Throughout the rocks, as above, there are many cracks.
At the end of this sequence, a normal fault was detected with dip and dip direction, respectively, 225°/72°. Above them for the next 44 meters, the dip of the rocks is constantly changing, with the main dip and dip direction, respectively, being 276°/70°. The sediments are thick-bedded microbrecciated limestones, gray-white in color, locally turning into medium-bedded. A strike slip follows, as shown in Figure 5.16.
At the stratigraphically upper part of the section (length approximately 220 meters), the main dip and dip direction, respectively, is 265°/75°. The dominant lithology is the thick-bedded limestone, of grayish-white color, which is locally medium-bedded, while in the sediments many faults and cracks are observed.
54
Figure 5.16: Strike slip with dip and dip direction at 160°/84°. On either side of the fault, no significant deformation at the sediments is observed.
5.2.6 Section 6
The length of this section is about 330 meters and the height is about 15 meters. From this section, 3 samples were collected. The orientation is NNE-SSW.
Due to the tectonic activity, the sediments throughout the section are highly stressed and fragmented. The sediments at the stratigraphically lower part of the section are gray-white medium- bedded limestones and have dip and dip direction, respectively, 089°/87°. Gradually, the dip decreases and reaches up to 260°/50° for the medium-bedded limestones and 264°/72° for the alternations of the thin-bedded and medium-bedded, as seen in Figure 5.17. From these rocks, we took the sample L1. About 45 meters to the south and the upper part of the section, no changes are observed.
55
Figure 5.17: In this figure, on the left, we see the alternations of thin-bedded and medium-bedded microbrecciated limestones with a dip of 264ο/72ο, from which we took the sample L1. On the right, they are the medium-bedded limestones can be seen with a dip 260°/50°. The dip, then, rises again and was measured at 305°/80°. For about 40 meters, the deformation in the sediments is so intense that the bedding is not even visible. At the next appearance where the dip was measured, it was 082ο/88ο. Above them, there are 14 meters of compact microbrecciated limestone, and this sequence is interrupted by a normal fault with a dip of 070°/75°. The sediments at the southern side of the fault (Figure 5.18) consist of thin-bedded to medium-bedded limestones, which appear to exhibit intense deformation. In the lower part of the section, the dip of the rocks is 220°/65°.
In the next 25 meters, we noticed alternations of thick-bedded and very thick-bedded microbrecciated limestones, gray-white in color, until the next fault, on the one side of which, as seen from Figure 5.19, the rocks are almost vertical, with the dip and the dip direction, respectively, is 185°/87°. The figure also shows the sampling point of sample L2.
56
Figure 5.18: This figure shows a normal fault with a dip of 070°/75° in the northern part of the section and the deformed medium-bedded limestones in the south with the dip of the rocks at the lower part being 220°/65°.
Figure 5.19: This image shows a damaged fault zone at the south of the section that causes deformation to the neighboring rocks. In circle is the sampling position of sample L2.
57 Above them, for approximately 20 meters the dominant lithological type is white-gray thick-bedded microbrecciated limestone and then a strike slip is interfering with dip and dip direction, respectively, 345°/78°. The layers on either side of the fault have the same dip.
In the following layers for the next 25 meters, the sediments are composed of a thick-bedded microbrecciated limestone, gray and white in color. At the end of these 25 meters, we noticed alternations of thin-bedded microbrecciated limestones to very thick-bedded microbrecciated with dip and dip direction, respectively, 262°/73°.
There is a fault, as shown in Figure 5.20, which penetrates the medium-bedded limestone and the stratigraphically upper parts of the section consist of medium-bedded microbreccia without a numerical value for the dip.
Figure 5.20: Sampling location of sample L3. The fault has a dip direction of 210°/85° and as shown in the picture, the surrounding rocks are strongly deformed. In the stratigraphically upper part of the site, the dip and the dip direction, respectively, were measured at 280°/70° and refer to medium-bedded and thick-bedded microbrecciated limestones, grayish-white in color.
58 5.2.7 Section 7
Section 7 of the study area is about 370 meters long and 3 samples were collected. Its height is 5 meters and its orientation is NNE-SSW.
The sediments in the stratigraphically lower part of the section consist of medium-bedded white- colored limestone with dip and dip direction, respectively, 146°/38°. From there we took sample D12. In the next 100 meters, we noticed alternations of thin-bedded and medium-bedded white-gray limestones with dip and dip direction, respectively, 306ο/17ο (Figure 5.21).
Figure 5.21: The dip and the dip direction, respectively, of thin-bedded limestones is 306o/17o. They are situated approximately 100 meters from the stratigraphically lower parts of the section. In the south, we noticed a normal fault, with dip and dip direction, respectively, 007ο/75ο, while we proceeded we noticed other faults. The main one is a reverse fault with a dip of 232ο/85ο with the rocks on either side having 140ο/30ο (Figure 5.22). The D13A and D13B samples were derived from thin-bedded limestones, gray and white in color, as shown in Figure 5.23. Bouma turbidite sequences were then observed in the stratigraphically upper part.
59
Figure 5.22: The picture shows the action of the reverse fault, in which we notice displacement of the index horizons, which are shaded to indicate this movement. The red color is the thin-bedded limestones, while the yellow is the medium-bedded. The dip of the sediments remains the same on both sides of the fault.
Figure 5.23: Sampling positions of samples D13A and D13B. Approximately 230 meters up to the stratigraphically upper parts of the section, the sediments are more damaged, due to the deformation. The dip does not change, while two folds were recorded (Figure 5.24). In the stratigraphically upper parts of the section, a damaged fault zone of about 3 meters thick was observed. At the end of the section, Bouma turbidite sequences were observed.
60
Figure 5.24: The 2 successive folds and the dip direction that their axes of deformation have.
5.2.8 Section 8
The length of this section is about 290 meters and its height exceeds 14 meters. Its orientation is NNE-SSW and from this section, 2 samples were collected.
In the stratigraphically lower part of the section, the sediments have undergone severe deformation. The first measured dip and dip direction is 10 meters at the beginning of the section, and is 227°/80°, referring to white-gray thick-bedded limestones. Above them, there are 10 meters of less tectonically strained white-gray thick-bedded limestones with their main dip remaining the same.
Then, we noticed a damaged fault zone, about 70 cm of thick. For the next 10 meters, the sediments are again white-gray thick-bedded limestone, where its thickness exceeds 1 meter, until we noted a fault with a dip and a dip direction of 163°/50° (Figure 5.25). Then, we noticed another damaged fault zone, about 50 cm thick and for the next 15 meters, there are alternations of white and gray colored thick-bedded and medium-bedded limestones with dip and dip direction, respectively, 200o/85o.
61
Figure 5.25: View of the fault whose dip was measured at the lower part as we see. In the left part of the photo, in the section with the color shading, the beginning of the damaged fault zone appears. There is another deformation of the rocks, which now have a dip and dip direction of 150°/40°. We collected the L4 sample and above them for the next 50 meters, the sediments are gray-white limestones, ranging from medium-bedded to very thick-bedded, as their thickness exceeds at some points even the 2 meters. Then, we noticed a possible strike slip with dip and dip direction, respectively, 003ο/80ο (Figure 5.26). The fault as we will see has created some branches that indicate “flower structure”. At that point, some nodules of siliceous composition were found, while the limestone became microbrecciated.
The dip of the rocks was measured 135°/40° and the strike slip has a dip and dip direction, respectively, 232°/75°. The limestone is white-gray in color and its thickness varies from 40 cm (medium-bedded) to more than 2 meters (very thick-bedded) (Figure 5.27). In the stratigraphically upper part of the section, the sediments consist of white-gray thin-bedded limestone.
62
ο ο Figure 5.26: The picture shows the possible strike slip with its dip being 003 / 80 , which has created a 30 cm thick damaged fault zone. Its dip direction implies that it is parallel to the thrust. The indicated branches show a flower structure.
Figure 5.27: This image shows a strike slip. Its dip direction indicates that it is vertical to the thrust. The precipitates that intersect are not deformed and there is no evident displacement of a horizon.
63 In the last 70 meters, we noted a damaged fault zone and the rocks in this zone have undergone intense tectonic strain. The main dip of the rocks is 238°/60°. The limestones are white-gray in color, microbrecciated and the thickness of the layers ranges from 20 cm to 70 cm. In the stratigraphically upper parts of the section, about 20 meters before the end of the section, we took the sample L5. Finally, 5 meters before the end, the dip and the dip direction, respectively, are 065°/83°.
5.2.9 Section 9
Section 9 of the study area is the southernmost section and is about 100 meters long. Its height starts at 2 meters and in places exceeds 10 meters.
Starting from the stratigraphically lower part of this section, the dip and the dip direction, in the first meters is 335°/70° (Figure 5.28). The sediments consist of gray-white medium-bedded limestones, which in places become thin-bedded.
Figure 5.28: View of the first meters of the section from of the northern part (stratigraphically lower part) of the section where the dip and the dip direction is 335°/70°. The dominant lithological type is the medium-bedded microbrecciated limestone. Characteristic of this section is that almost all rock horizons are heavily deformed. This is due to the fact that this section is on the front of the thrust and the tectonic activity is very intense and because of this, we also noticed the following tectonic lenses (Figure 5.29).
64
Figure 5.29: Tectonic lenses that were found, due to the active tectonic activity. We can observe smaller lenses inside the outer one. The rocks above the lenses are so tectonically affected that we cannot take more information about their dip. In the stratigraphically upper part of the section, we noticed one fold and more specifically an anticline, and the dip and dip direction in the adjacent rocks as shown in Figure 5.30 is 115°/70° (similar to the dip at the beginning of the position-stratigraphically lower parts).
65
Figure 5.30: View from the southern part of the section where the anticline is depicted. As in the previous photos of this section, we observe the intensity of the tectonic activity.
5.2.10 Quarry
The quarry lies west of the Ionian Road. Until that moment, the quarry was composed of 7 levels. A panoramic view of the southern side of the quarry is shown in Figure 5.31.
Figure 5.31: Panoramic view from the south side of the Quarry, showing the 7 levels of excavation and its entrance. At the entrance of the quarry, we observed turbidite sequences. At Level 3, a 1 meter long damaged fault zone was identified (Figure 5.32). The dips are relatively mild in contrast to the upper levels, in which the dip seems to gradually grow.
66
Figure 5.32: Picture from the third level of the Quarry in which a damaged fault zone of 1 meter length is depicted. Numbers indicate levels. The dip as shown on the left side of the photo is mild (no data available). At the fourth level, the dip becomes bigger (dip and the dip direction are 180°/ 55° - Figure 5.33) indicating that the layers are parallel to the thrusts.
Figure 5.33: The dip at the forth level of the Quarry is indicative of the general increase of the dip as we are heading to the upper levels. At the seventh and the upper level of the quarry, where trace fossils were found (Figure 5.34 B), the white color that exists in the rocks at this level suggests a marly composition. There was also a "negative flower structure", which indicates the existence of strike slip faults (Figure 5.34A).
67
Figure 5.34: A) Negative flower structure in a strike slip, in the upper layers of the Quarry, B) A rock with trace fossils found in the upper layers of the Quarry.
5.2.11 Road to Gribovo
Due to the fact that outcrops were only found on the road to Gribovo and this was not a continuous section, all those appearances will all be examined together. The outcrop height is about 3-4 meters and the distance from the location of sample D14 until the village is 3 km.
Starting from the stratigraphically lower parts, we observe gray-colored medium-bedded limestones from which we took the D14 sample and above them thin-bedded limestones with dip and dip direction, respectively, 238ο/80ο. Then, we encountered alternations of gray thin-bedded and medium-bedded limestone layers with their dips being as shown in Figure 5.35. From there, sample D16 was collected.
Figure 5.35: The picture shows the location of sample D16 and the dip of the alternations of the thin-bedded and the medium-bedded grey limestones.
68 Moving towards Gribovo and the stratigraphically upper parts, the alternations of thin-bedded and medium-bedded limestones with a dip of 250°/40° continue (Figure 5.36), from which we took the sample D18. Their dip in cases is 208o/20o.
Figure 5.36: The picture shows the alternations of thin-bedded and medium-bedded limestones, with dip and dip direction 250o/40o. At the same time, the calciturbidites, which are found in the stratigraphically upper sections, appear above the thin-bedded gray limestones, which their dip and dip direction, respectively, is 248ο/40ο (Figure 5.37). In the calciturbidites were found silicate layers
69
Figure 5.37: The picture shows at the upper parts the calciturbidites and below them the thin-bedded limestones with dip 248o/40o. In the calciturbidites we can see the silicate layers. Subsequently, the sediments consist of white-gray thin-bedded limestones with dip and dip direction, respectively, 158°/18° (Figure 5.38).
Figure 5.38: The dip of the thin-bedded limestones, at the stratigraphically upper parts. The shales of Vigla follow about 70 meters thick, signaling the change in lithology. The stratigraphically superior limestones are now thin-bedded microbrecciated, grey-white in color, with a dip of 070°/45° up to 100°/18°. In the stratigraphically upper parts, there are alternations of white- gray thin-bedded and medium-bedded limestones with dip and dip direction, respectively, 060°/30° (Figure 5.39). Within the layers horizons of silicate composition or in spherical form were found.
70
Figure 5.39: Thin-bedded microbrecciated limestones found at the stratigraphically upper parts with dip 060o/30o, nearby Gribovo. A final map with all measured dips is shown in Figure 5.40.
Figure 5.40: A final form of the study area that includes all the dip measurements.
71 CHAPTER 6: LITHOFACIES ANALYSIS AND AGE DETERMINATION
The microfacies analysis, as already mentioned, is a very important tool that helps determine the depositional environment. As mentioned in chapter 5.1, a total of 26 samples were collected, of which the microfacies analysis was carried out at 17 of them. 13 of them refer to the sections that are located along the Ionian Road, with a main direction of NNE-SSW, while the other 4 were collected on the road to the village of Gribovo. No samples were collected from sections 1, 5 and 9 or from the quarry. The following table summarizes the sections studied and which samples were collected from each.
Table 6: Table summarizing the number of samples collected from each section.
6.1 Analysis of the samples and the thin sections of each section
6.1.1 Section 2
Section 2 includes samples D1 and D2.
SAMPLE D1
Microscopic observation
The analysis allowed the identification of one microfacies type for sample D1.
Sorted biosparite of Grainstone type with plenty of microfossils (SMF 4)
At this microfacies, SMF 4, we observe a microbrecciated limestone of Grainstone type, with rounded and sorted grains. It also has clastic material (quartz, fragments of hornfels and
72 limestones). The fossils it contains are scattered foraminifera (benthic and planktonic – Figure 6.1) and bivalve fragments. Also, lamination was found, indicating the upper part of a turbidite flow.
Figure 6.1: Left: A) Globotruncanita elevata. B) Globotruncanita stuartiformis, c) Globotruncana arca Right: Coexistence of planktonic and benthic foraminifera: a) Planktonic foraminifera, b) Benthic foraminifera.
Matrix: Sparite, Fossils: planktonic foraminifera, benthic foraminifera, bivalves fragments, Dunham’s classification: Grainstone, Folk’s classification: Sorted Biosparite, Wilson’s classification: SMF: 4, Environment: FZ 3, Sample: D1
Interpretation
The depositional environment of sample D1 is represented by microfacies type Sorted biosparite, of Grainstone type, with the presence of many fossils (SMF 4), belonging to the FZ 3 facies zone, i.e., the basin boundary or deep shelf limit (clinotherm, toe of slope). The depth of this zone varies, with a maximum of 200-300 meters, which is generally below the ripple base and just at the level of oxygenation. The dominant facies types are finely crystalline carbonate facies (mudstones- wackestones) with alternations of breccia and bioclastic-lithoclastic packstones, with thin beds of aluminate-silicate material. For the sedimentation in this area both pelagic organisms, and fine- grained clastic material from the adjacent shallow shelves contribute, so there is mixing of benthic and pelagic organisms (FZ 3).
73 SAMPLE D2
Microscopic observation
The analysis allowed the identification of one microfacies type for sample D2.
Packed biomicrite of Packstone type with plenty of microfossils (SMF 4)
At this microfacies, SMF 4, we observe a microbrecciated bioclastic limestone of Packstone type, with varying biodiversity, including planktonic and benthic foraminifera (Figure 6.2), ostracods (Figure 6.2), gastropods and bivalve fragments (Figure 6.2), algae, corals and peloids (Figure 6.3). The grains are rounded and usually sorted. It also contains clastic material (quartz, fragments of cherts and limestones).
Figure 6.2: Left: a & b) Benthic foraminifera (Milliodae), c) Biserial benthic foraminifera. Right: a) Planktonic foraminifera (Globotruncanidae), b) bivalve fragment, c) ostracod.
Figure 6.3: Left: Orbitoides media, Right: Clast with peloids
74
Figure 6.4: Left: Cuneolina sp. Right: Globotruncana stuartiformis.
Matrix: Micrite, Fossils: benthic foraminifera, planktonic foraminifera, ostracods, coral fragments, bivalves and gastropods fragments, algae, peloids, Dunham’s classification: Packstone, Folk’s classification: Packed Biomicrite, Wilson’s classification: SMF: 4, Environment: FZ 4, Sample: D2
Interpretation
The depositional environment of sample D2 is represented by microfacies Packed biomicrite, of Packstone type with a great number of microfossils (SMF 4), which belongs to the FZ 4 facies zone, that is to say a slope of the carbonate platform (marine talus, clinotherm, unstable sedimentation with debris). The slope area is above the lower oxygenation limit and between the base and the upper ripple boundary and has a dip of ~30°. These are unstable, re-deposited debris sediments, which vary in shape and size and create finely crystalline layers with mega-slump structures. In these bioclastic wackestones-packstones participate and the fauna consists of allochthonous elements, as well as various encrusting organisms (FZ 4). In addition to the main facies developed previously, a small segment of peloids was observed, indicating a rock fragment from a shallow section.
6.1.2 Section 3
Section 3 includes sample D3.
SAMPLE D3
Microscopic observation
The analysis allowed the identification of one microfacies type for sample D3.
Sorted biosparite of Grainstone with plenty of microfossils (SMF 2)
75 At this microfacies, SMF 2, we observe a very finely crystalline pelagic limestone of Grainstone type containing small bioclasts (scattered planktonic and benthic foraminifera) and cross- stratifications.
Figure 6.5: Left: Acarinina subsphaerica, Right: Morozovella angulata.
Matrix: Sparite, Fossils: benthic foraminifera, planktonic foraminifera, Dunham’s classification: Grainstone, Folk’s classification: Sorted Biosparite, Wilson’s classification: SMF: 2, Environment: FZ 2, Sample: D3
Interpretation
The depositional environment of sample D3 is represented by microfacies type Sorted biosparite, of Grainstone type, with plenty of microfossils (SMF 2), belonging to the FZ 2 facies zone, that is to say a deep continental shelf. Sedimentation in these environments takes place in marine waters of good oxygenation and normal salinity circulation. The depth is big (up to several hundred meters) and due to the low wave energy, homogeneous neritic sedimentation of a shelf takes place. During episodes, bioclastic grainstones appear. The sediments of this zone have been homogenized through bioturbation and the layers are of low to medium thickness (FZ 2).
6.1.3 Section 4
Section 4 includes samples D5 and D6.
SAMPLE D5
Microscopic observation
Sample D5 can be separated in two parts, which for convenience are divided into A and B.
76 Α) The analysis allowed the identification of one microfacies type for sample D5a.
Sparse biomicrite of Mudstone type with radiolaria (SMF 3)
At this microfacies, SMF 3, we observe a pelagic limestone of Mudstone type. The matrix contains scattered fossils (radiolaria) and some transferred foraminifera, at the boundaries of the 2 sections.
Matrix: Micrite, Fossils: radiolaria, foraminifera (transferred), Dunham’s classification: Mudstone, Folk’s classification: Sparse Biomicrite, Wilson’s classification: SMF: 3, Environment: FZ 1, Sample: D5a
Interpretation
The depositional environment of sample D5a is represented by microfacies type Sparse biomicrite, of Mudstone type with radiolaria (SMF 3), that belongs to the FZ 1 facies zone, i.e. a deep-sea sedimentation basin where pelagic carbonate sedimentation is triggered by carbonate turbiditic sedimentation. Below the limits of calcite dissolution, radiolarites are formed. Limestones at these depths (deep sea sediments) often show rhythmic structure. Planktonic and neritic organisms such as radiolaria prevail (FZ 1).
Β) The analysis allowed the identification of one microfacies type for sample D5b.
Unsorted biosparite of Grainstone with few microfossils (SMF 2)
At this microfacies, SMF 2, we observe a pelagic microbrecciated limestone of Grainstone type, with varying biodiversity, mainly planktonic foraminifera and ostracods. Also, some fossils are diagenetically altered.
Figure 6.6: Rugoglobigerina sp.: Within the boundaries of the 2 sections
77
Figure 6.7: Left: Rugoglobigerina sp., Right: Globotruncana lapparenti.
Figure 6.8: Globotruncana ventricosa,
Matrix: Sparite, Fossils: planktonic foraminifera, ostracods, Dunham’s classification: Grainstone, Folk’s classification: Unsorted Biosparite, Wilson’s classification: SMF: 2, Environment: FZ 2, Sample: D5b
Interpretation
The depositional environment of sample D5b is represented by microfacies type Unsorted biosparite, of Grainstone type, with presence of few fossils (SMF 2), belonging to the FZ 2 facies zone, that is to say a deep continental shelf. Sedimentation in these environments takes place in marine waters of good oxygenation and normal salinity circulation. The depth is big (up to several hundred meters) and due to the low wave energy, homogeneous neritic sedimentation of a shelf takes place. During episodes, bioclastic grainstones appear. The sediments of this zone have been homogenized through bioturbation and the layers are of low to medium thickness (FZ 2).
78 SAMPLE D6
Microscopic observation
The analysis allowed the identification of one microfacies type for sample D6.
Packed biomicrite of Packstone type with plenty of microfossils (SMF 4)
At this microfacies, SMF 4, we observe a microbrecciated bioclastic limestone of Packstone type, with varying biodiversity, including planktonic and benthic foraminifera, ostracods, rudists and bivalves fragments and peloids (Figure 6.10). The grains are rounded and usually sorted. It also has clastic material (quartz, fragments of cherts and limestones).
Figure 6.9: Left: Marginotruncana pseudolinneana, Right: Sigalitruncana schneegansi.
Figure 6.10: Left: Globotruncanita stuartiformis, Right: Peloids.
Matrix: Micrite, Fossils: planktonic foraminifera, benthic foraminifera, bivalves fragments, ostracods, rudists fragments, peloids, Dunham’s classification: Packstone, Folk’s classification: Packed Biomicrite, Wilson’s classification: SMF: 4, Environment: FZ 4, Sample: D6
Interpretation
The depositional environment of sample D6 is represented by microfacies Packed biomicrite, of Packstone type with presence of many microfossils (SMF 4), which belongs to the FZ 4 facies zone, that is to say a slope of the carbonate platform (marine talus, clinotherm, unstable
79 sedimentation with debris). The slope area is above the lower oxygenation limit and between the base and the upper ripple boundary and has a dip of ~30°. These are unstable, re-deposited debris sediments, which vary in shape and size and create finely crystalline layers with mega-slump structures. There participate bioclastic wackestones-packstones and the fauna consists of allochthonous elements, as well as various encrusting organisms (FZ 4). In addition to the main facies previously developed, a small segment of peloids was observed, indicating origin from a shallow low energy position.
6.1.4 Section 6
Section 6 includes samples L1, L2 and L3.
SAMPLE L1
Microscopic observation
The analysis allowed the identification of one microfacies type for sample L1.
Unsorted biosparite of Grainstone with Packstone alternations type with scattered planktonic foraminifera (SMF 2)
At this microfacies, SMF 2, we observe a bioclastic pelagic limestone of Grainstone with packstone alternations type, containing small bioclasts such as scattered planktonic foraminifera and others belonging to the Globotruncanidae family.
Matrix: Sparite, Fossils: planktonic foraminifera, ostracods, Dunham’s classification: Grainstone & Packstone, Folk’s classification: Unsorted Biosparite, Wilson’s classification: SMF: 2, Environment: FZ 2, Sample: L1
Interpretation
The depositional environment of sample L1 is represented by microfacies type Unsorted biosparite, of Grainstone with Packstone alternation type, with scattered planktonic foraminifera (SMF 2), belonging to the FZ 2 facies zone, that is to say a deep continental shelf. Sedimentation in these environments takes place in marine waters of good oxygenation and normal salinity circulation. The depth is big (up to several hundred meters) and due to the low wave energy, homogeneous neritic sedimentation of a shelf takes place. In episodes, bioclastic grainstones appear. The sediments of this zone have been homogenized through bioturbation and the layers are of low to medium thickness (FZ 2).
80 SAMPLE L2
Microscopic observation
The analysis allowed the identification of one microfacies type for sample L2.
Sparse biomicrite of Packstone type with few microfossils (SMF 4)
At this microfacies, SMF 4, we observe a bioclastic pelagic limestone of Packstone type, with varying biodiversity, containing bioclasts that are highly eroded and rounded grains. It includes clastic material such as quartz and fragments of limestones and cherts. The fossils that it contains are mainly foraminifera, ostracods and bivalve fragments.
Figure 6.11: Left: Globotruncanita stuarti, Right: Globotruncana falsostuarti.
Matrix: Micrite, Fossils: planktonic foraminifera, benthic foraminifera, ostracods, bivalve fragments, Dunham’s classification: Packstone, Folk’s classification: Sparse Biomicrite, Wilson’s classification: SMF: 4, Environment: FZ 3, Sample: L2
Interpretation
The depositional environment of sample L2 is represented by microfacies type Sparse biomicrite, of Packstone type, with presence of a few fossils (SMF 4), belonging to FZ 3 facies zone, i.e., the basin boundary or deep shelf limit (clinotherm, toe of slope). The depth of this zone varies, with a maximum of 200-300 meters, which is generally below the ripple base and just at the level of oxygenation. The dominant facies types are finely crystalline carbonate facies (mudstones- wackestones) with alternations of breccia and bioclastic-lithoclastic packstones, with thin beds of aluminate-silicate material. For the sedimentation in this area contribute both pelagic organisms, and detailed clastic material from the adjacent shallow shelves, so there is mixing of benthic and pelagic organisms (FZ 3).
81 SAMPLE L3
Microscopic observation
The analysis allowed the identification of one microfacies type for sample L3.
Packed biomicrite of Packstone type with few microfossils (SMF 4)
At this microfacies, SMF 4, we observe a bioclastic pelagic limestone of Packstone type, with varying biodiversity, including planktonic and benthic foraminifera, ostracods and bivalves fragments. The grains are rounded and usually sorted. It also has clastic material (quartz, fragments of cherts and limestones). Beyond the main facies previously developed, a small segment of peloids was observed, indicating a piece from the platform's internal phase, both transported.
Matrix: Micrite, Fossils: planktonic foraminifera, benthic foraminifera, ostracods, bivalves fragments, peloids, Dunham’s classification: Packstone, Folk’s classification: Packed Biomicrite, Wilson’s classification: SMF: 4, Environment: FZ 3, Sample: L3
Interpretation
The depositional environment of sample L3 is represented by microfacies type Packed biomicrite, of Packstone type, with the presence of few fossils (SMF 4), belonging to FZ 3 facies zone, i.e., the basin boundary or deep shelf limit (clinotherm, toe of slope). The depth of this zone varies, with a maximum of 200-300 meters, which is generally below the ripple base and just at the level of oxygenation. The dominant facies types are finely crystalline carbonate facies (mudstones- wackestones) with alternations of breccia and bioclastic-lithoclastic packstones, with thin beds of aluminate-silicate material. For the sedimentation in this area contribute both pelagic organisms, and detailed clastic material from the adjacent shallow shelves, so there is mixing of benthic and pelagic organisms (FZ 3).
6.1.5 Section7
Section 7 includes samples D12, D13A and D13B.
SAMPLE D12
Microscopic observation
Sample D12 consists of two different parts, which for convenience are divided into A and B.
Α) The analysis allowed the identification of one microfacies type for sample D12a.
Fossiliferous micrite of Mudstone type with various transferred microfossils (SMF 3)
82 At this microfacies, SMF 3, we observe a bioclastic pelagic limestone of Mudstone type. The matrix contains scattered radiolaria and few foraminifera, both benthic and planktonic (Figure 6.12), that are probably transferred. Characteristic is a stream that has been broken and moved, which has been filled with planktonic foraminifera.
Figure 6.12: Deformed planktonic foraminifera, Radiolaria
Matrix: Micrite, Fossils: planktonic foraminifera, benthic foraminifera, radiolaria, Dunham’s classification: Mudstone, Folk’s classification: Fossiliferous Micrite, Wilson’s classification: SMF: 3, Environment: FZ 1, Sample: D12a
Interpretation
The depositional environment of sample D12a is represented by microfacies type Fossiliferous micrite, of Mudstone type, with various transferred fossils (SMF 3), that belongs to the FZ 1 facies zone, i.e. a deep-sea sedimentation basin where pelagic carbonate sedimentation is triggered by carbonate turbiditic sedimentation. Below the limits of calcite dissolution, radiolarites are formed. Limestones at these depths (deep sea sediments) often show a rhythmic structure. Planktonic and neritic organisms such as radiolaria prevail (FZ 1).
Β) The analysis allowed the identification of one microfacies type for sample D12b.
Unsorted biosparite of Grainstone type with a few scattered peloids (SMF 2)
At this microfacies, SMF 2, we observe a very finely crystalline pelagic limestone of Grainstone type containing no fossils, except from some transferred (some scattered peloids).
Matrix: Sparite, Fossils: few scattered peloids, Dunham’s classification: Grainstone, Folk’s classification: Unsorted Biosparite, Wilson’s classification: SMF 2, Environment: FZ 2, Sample: D12b
83 Interpretation
The depositional environment of the sample D12b is represented by the microfacies type Unsorted biosparite, of Grainstone type, with a few scattered peloids (SMF 2), belonging to the facies zone FZ 2, that is to say a deep continental shelf. Sedimentation in these environments takes place in marine waters of good oxygenation and normal salinity circulation. The depth is big (up to several hundred meters) and due to the low wave energy, homogeneous neritic sedimentation of a shelf takes place. In episodes, bioclastic grainstones appear. The sediments of this zone have been homogenized through bioturbation and the layers are of low to medium thickness (FZ 2).
SAMPLE D13Α
Microscopic observation
The analysis allowed the identification of one microfacies type for sample D13A.
Unsorted biosparite of Grainstone type with foraminifera and peloids (SMF 2)
At this microfacies, SMF 2, we observe a very finely crystalline pelagic limestone of Grainstone type containing small bioclasts such as some ostracods and scattered planktonic and benthic foraminifera and peloids (Figure 6.14). Also, few radiolaria were found and cross-stratifications.
Figure 6.13: Left: Globotruncana bulloides, Right: Globotruncanita stuartiformis.
84
Figure 6.14: Peloids.
Matrix: Sparite, Fossils: benthic foraminifera, planktonic foraminifera, ostracods, peloids, few radiolaria, Dunham’s classification: Grainstone, Folk’s classification: Unsorted Biosparite, Wilson’s classification: SMF: 2, Environment: FZ 3, Sample: D13Α
Interpretation
The depositional environment of sample D13A is represented by microfacies Unsorted biosparite, of Packstone type, with presence of foraminifera and peloids (SMF 2), belonging to the FZ 2 facies zone, that is to say a deep continental shelf. Sedimentation in these environments takes place in marine waters of good oxygenation and normal salinity circulation. The depth is big (up to several hundred meters) and due to the low wave energy, homogeneous neritic sedimentation of a shelf takes place. In episodes, bioclastic grainstones appear. The sediments of this zone have been homogenized through bioturbation and the layers are of low to medium thickness (FZ 2).
SAMPLE D13Β
Microscopic observation
The analysis allowed the identification of one microfacies type for sample D13B.
Micrite & Dismicrite of Mudstone type with few pelagic microfossils (SMF 3)
At this microfacies, SMF 3, we observe a bioclastic pelagic limestone of Mudstone type that contains scattered pelagic planktonic protozoans (Calpionella sp. - Figure 6.15), and radiolaria (Figure 6.15).
85
Figure 6.15: Left: a) Calpionella sp. b) Radiolaria, Right: Different sizes of Radiolaria.
Matrix: Micrite, Fossils: Planktonic protozoans (Calpionella sp. - scattered), Radiolaria, Dunham’s classification: Mudstone, Folk’s classification: Micrite & Dismicrite, Wilson’s classification: SMF: 3, Environment: FZ 1, Sample: D13Β
Interpretation
The depositional environment of sample D13B is represented by microfacies type Fossiliferous Micrite, of Mudstone type, with few pelagic microfossils (SMF 3), that belongs to the FZ 1 facies zone, i.e. a deep-sea sedimentation basin where pelagic carbonate sedimentation is triggered by carbonate turbiditic sedimentation. Below the limits of calcite dissolution, radiolarites are formed. Limestones at these depths (deep sea sediments) often show rhythmic structure. Planktonic and neritic organisms such as radiolaria prevail (FZ 1).
6.1.6 Section 8
Section 8 includes samples L4 and L5.
SAMPLE L4
Microscopic observation
The analysis allowed the identification of one microfacies type for sample L4.
Micrite and dismicrite of Mudstone type with scattered pelagic microfossils (SMF 3)
At this microfacies, SMF 3, we observe a bioclastic pelagic limestone of Mudstone type, that contains scattered microfossils, and at this particular sample radiolaria (Figure 6.16) and some planktonic organisms.
86
Figure 6.16: Scattered radiolaria
Matrix: Micrite, Fossils: few planktonic organisms, radiolaria, Dunham’s classification: Mudstone, Folk’s classification: Micrite & Dismicrite, Wilson’s classification: SMF: 3, Environment: FZ 1, Sample: L4
Interpretation
The depositional environment of sample L4 is represented by microfacies type Micrite & Dismicrite, of Mudstone type, with scattered pelagic microfossils (SMF 3), that belongs to the FZ 1 facies zone, i.e. a deep-sea sedimentation basin where pelagic carbonate sedimentation is ejected by carbonate turbiditic sedimentation. Below the limits of calcite dissolution, radiolarites are formed. Limestones at these depths (deep sea sediments) have often showed rhythmic structure. Planktonic and neritic organisms such as radiolaria prevail (FZ 1).
SAMPLE L5
Microscopic observation
The analysis allowed the identification of one microfacies type for sample L5.
Packed biomicrite of Packstone type with various microfossils (SMF 3)
At this microfacies, SMF 3, we observe a bioclastic pelagic limestone of Packstone type. The matrix contains scattered microfossils, such as planktonic and benthic foraminifera, bivalve and gastropod fragments, ostracods and radiolaria.
87
Figure 6.17: Left: Globotruncanita stuartiformis, Right: Sigalitruncana schneegansi.
Matrix: Micrite, Fossils: Planktonic foraminifera, benthic foraminifera, ostracods, bivalve fragments, gastropods fragments, radiolaria, Dunham’s classification: Packstone, Folk’s classification: Packed biomicrite, Wilson’s classification: SMF 3, Environment: FZ 3, Sample: L5
Interpretation
The depositional environment of sample L5 is represented by microfacies type Packed biomicrite, of Packstone type, with presence of various microfossils (SMF 3), belonging to the FZ 3 facies zone, i.e., the basin boundary or deep shelf limit (clinotherm, toe of slope). The depth of this zone varies, with a maximum of 200-300 meters, which is generally below the ripple base and just at the level of oxygenation. The dominant facies types are finely crystalline carbonate facies (mudstones- wackestones) with alternations of breccia and bioclastic-lithoclastic packstones, with thin beds of aluminate-silicate material. For the sedimentation in this area contribute both pelagic organisms, and detailed clastic material from the adjacent shallow shelves, so there is mixing of benthic and pelagic organisms (FZ 3).
6.1.7 Road to Gribovo
Section along the road to Gribovo includes samples D14, D16, D18 and D20.
SAMPLE D14
Microscopic observation
The analysis allowed the identification of one microfacies type for sample D14.
Micrite & Dismicrite of Mudstone type with radiolaria (SMF 3)
88 At this microfacies, SMF 3, we observe a bioclastic pelagic limestone of Mudstone type, that contains scattered pelagic microfossils, and at this particular sample radiolaria (Figure 6.18). The sample contains plenty of cracks which are filled secondary by calcite material.
Figure 6.18: Radiolaria
Matrix: Micrite, Fossils: Radiolaria, Dunham’s classification: Mudstone, Folk’s classification: Micrite & Dismicrite, Wilson’s classification: SMF: 3, Environment: FZ 1, Sample: D14
Interpretation
The depositional environment of sample D14 is represented by microfacies type Micrite & Dismicrite, of Mudstone type, with radiolaria (SMF 3), that belongs to the FZ 1 facies zone, i.e. a deep-sea sedimentation basin where pelagic carbonate sedimentation is triggered by carbonate turbiditic sedimentation. Below the limits of calcite dissolution, radiolarites are formed. Limestones at these depths (deep sea sediments) often show rhythmic structure. Planktonic and neritic organisms such as radiolaria prevail (FZ 1).
SAMPLE D16
Microscopic observation
The analysis allowed the identification of one microfacies type for sample D16.
Sparse biomicrite of Wackestone type with scattered pelagic microfossils (SMF 3)
At this microfacies, SMF 3, we observe a bioclastic pelagic limestone of Wackestone type, that contains scattered pelagic microfossils, and at this particular sample radiolaria (Figure 6.19) and some scattered planktonic protozoans of Calpionellidae family (Calpionella sp.).
89
Figure 6.19: Radiolaria Matrix: Micrite, Fossils: Radiolaria, Planktonic protozoans (Calpionella sp.), Dunham’s classification: Wackestone, Folk’s classification: Sparse Biomicrite, Wilson’s classification: SMF: 3, Environment: FZ 1, Sample: D16
Interpretation
The depositional environment of sample D16 is represented by microfacies type Sparse biomicrite, of Wackestone type, with scattered pelagic microfossils (SMF 3), that belongs to the FZ 1 facies zone, i.e. a deep-sea sedimentation basin where pelagic carbonate sedimentation is triggered by carbonate turbiditic sedimentation. Below the limits of calcite dissolution, radiolarites are formed. Limestones at these depths (deep sea sediments) often show rhythmic structure. Planktonic and neritic organisms such as radiolaria prevail (FZ 1).
SAMPLE D18
Microscopic observation
The analysis allowed the identification of one microfacies type for sample D18.
Sparse biomicrite of Wackestone with radiolaria (SMF 3)
At this microfacies, SMF 3, we observe a bioclastic pelagic limestone of Wackestone type, that contains scattered pelagic microfossils, and at this particular sample radiolaria (Figure 6.20).
90
Figure 6.20: Radiolaria Matrix: Micrite, Fossils: Radiolaria, Dunham’s classification: Wackestone, Folk’s classification: Sparse Biomicrite, Wilson’s classification: SMF: 3, Environment: FZ1, Sample: D18
Interpretation
The depositional environment of sample D18 is represented by microfacies type Sparse biomicrite of Wackestone type, with radiolaria (SMF 3), that belongs to the FZ 1 facies zone, i.e. a deep-sea sedimentation basin where pelagic carbonate sedimentation is triggered by carbonate turbiditic sedimentation. Below the limits of calcite dissolution, radiolarites are formed. Limestones at these depths (deep sea sediments) are often show rhythmic sedimentation. Planktonic and neritic organisms such as radiolaria prevail (FZ 1).
SAMPLE D20
Microscopic observation
The analysis allowed the identification of one microfacies type for sample D20.
Unsorted biosparite of Grainstone type with few microfossils (SMF 4)
At this microfacies, SMF 4, we observe a microbrecciated pelagic limestone of Grainstone type, containing a few fossils, mainly foraminifera. It is polymict and it includes clastic material such as quartz and fragments of limestones and cherts.
91
Figure 6.21: Left: Sigalitruncana sigali, Right: Marginotruncana pseudolinneiana.
Matrix: Sparite, Fossils: planktonic foraminifera, mollusks fragments, Dunham’s classification: Grainstone, Folk’s classification: Unsorted Biosparite, Wilson’s classification: SMF: 4, Environment: FZ 3, Sample: D20
Interpretation
The depositional environment of sample D20 is represented by microfacies type Unsorted biosparite, of Grainstone type, with presence of few fossils (SMF 4), belonging to the FZ 3 facies zone, i.e., the basin boundary or deep shelf limit (clinotherm, toe of slope). The depth of this zone varies, with a maximum of 200-300 meters, which is generally below the ripple base and just at the level of oxygenation. The dominant facies types are finely crystalline carbonate facies (mudstones- wackestones) with alternations of breccia and bioclastic-lithoclastic packstones, with thin beds of aluminate-silicate material. For the sedimentation in this area contribute both pelagic organisms, and detailed clastic material from the adjacent shallow shelves, so there is mixing of benthic and pelagic organisms (FZ 3).
92 CHAPTER 7: DISCUSSION
After the analysis from the field work, we can conclude that the intense deformation presented in all outcrops is due to the fact that they are positioned close to the thrust, confirming that all these rocks were probably deformed synchronously with orogenesis (Figure 7.1).
Figure 7.1: Combined map with the study area on a geological and topographic map from Google Earth. Both show the study area (c), the geological (a) relative to the thrusts and the other relative to the relief (b). This leads to the conclusion that there are many smaller faults, either strike slip with smaller branches or parallel to the thrust, resulting in the dip of the layers being in places to the west and in places to the east. The existence of these ridges suggests that they characterize the anticline structures created within these structures, and for that as we have seen before, they dip to the west or to the east. The existence of reverse faults is affected by the thrust, whereas the existence of normal faults shows their syn-sedimentary character.
Exceptions are sections 1 and 3, as well as the upper layers (top) of the quarry, in which the layers appear without any deformation. They were probably deposited later hence; the deformation of rocks should be synchronous with sedimentation. But this is not true because the deformation occurred during the Eocene, that is, some of the folds found are actually slumps. Such deformations synchronous with the thrusts, however, as some of the non-deformed rocks are of Paleocene’s age and the rocks below them are deformed, this suggests that they are contemporary to sedimentation.
The stratigraphically upper layers in section 1 and in the quarry as well as the layers of section 3 seem to be without deformation. The questions that arise and will be discussed in conclusions whether all layers that are deformed have slumps rather than folds.
93 Except for these three sections, all others exhibit intense internal deformation, but it is not clear whether the deformation occurred during the Eocene activation of the thrusts (folds) or during sedimentation in limited basins (slumps). The presence of turbidites and microbreccia indicates that some of these deformations may have occurred during sedimentation. The analysis of the ages, which will be carried out in the conclusions, will probably help to clarify what happened.
The existence of deformation also forms the external relief of the studied areas. Each hill we encountered (Figure 5.5) also shows an anticline structure and each low point a syncline structure. The term structure is used because we do not yet know whether it is anticline and syncline respectively or whether they have been formed due to slumps.
The identification of the ages will not exclude the possibility that it is a combination of events, that is, a part of the deformations in respect are synchronous to sedimentation, but most of them seem to be due to the thrust as it is adjacent to it.
Sections 2,4,5,6,7,8,9 are stratigraphically lower, section 1 and the top of quarry are stratigraphically on the upper part and section 3 is the eastern section. This combination, the fact that the upper parts seems to be non-deformed, leads to the conclusion that most of the deformation is synchronous with sedimentation. However, the study area is close to the thrust and therefore the factor of tectonism should be also taken into account.
According to the geological map of the Arta sheet of I.G.M.E., across the A-Ά section, the following structure appears to be broadly followed: anticline-syncline-anticline. Thus, this structure is supported by the fact that Paleocene and Eocene rocks are outcropping. Paleocene limestones were not traced across the A-Ά section; nevertheless they may be covered by the alluvial sediments. Due to the fact that the age of section 3 is Paleocene, it could be in a narrow zone, but we didn’t recognize it with the shape that the geological map suggests. As Paleocene limestones are found to the north, the fault should be considered as a strike slip thus observed lateral changes can be explained and leaving the relief as it was.
Taking the microfacies analysis into consideration, we can conclude that the FZ of the studied samples ranges between 1 & 4, thus it varies from deep-sea basin to the slope of the carbonate platform (Figure 7.2).
Also, it is important to note that samples D1, D2, D5, D6, D12 and L3 represent parts of turbiditic sequences, carrying downslope rock fragments, such as peloids, from shallower zone environments from a nearby platform. So, to find them side-by-side suggests the presence of a turbiditic sequence. That is the reason that we study separately samples D5 and D12, like two different samples.
94
Figure 7.2: Distribution of the samples according to the results from microfacies analysis. A: Sea level, B: Fair-weather wave base, C: Storm-wave weather base, D: Oxygenation level (modified from Flugel, 2004). As we see, in the same area four different FZ were found, that means four different depositional environments. The samples whose age is Lower Cretaceous were collected from Vigla’s limestones representing very deep waters. The samples collected from Senonian limestones indicate shallower depositional environments. The changes from FZ 2 (deep-shelf) to FZ 4 (slope) could be due to faults between the sections or faults in the sections.
Sample D1 was collected from sediments that are stratigraphically lower from D2 and we see that the older sediments represent deeper parts. But, sample D3 which was collected from Eocene limestones characterizes an FZ 2 environment, that confirms its syn-rift and not post-rift position being in deeper waters (from FZ 4-slope we are at FZ 2-deep shelf).
Due to the faults between the sections, is seems that stratigraphically the environmental changes from shallow waters to deep-sea basin, during the sedimentation. Also, faults that are between sections could possibly bring sediments of different environments side-by-side.
For example, in section 4 alternations of shallow and deep water deposits show the change of the environment during sedimentation. On the contrary, between section 4 and 5 a fault could provide the lateral contact of two different environments.
Only on the road to Gribovo, samples D14, D16 and D18, that their age is Lower Cretaceous (Vigla limestones), belong to the same FZ (FZ 1). Sample D20, whose age is Upper Cretaceous and is stratigraphically upper, belongs to FZ 3, that is shallower waters, as is should be.
95 It has to be noted that variations in sedimentation conditions were observed, meaning that some of these faults were normal and affected sedimentation conditions. We observed variations in sedimentation environments according to microfacies analysis suggesting that the faults that today appear as thrusts possibly were normal faults during sedimentation, thus affecting sedimentation conditions. This concerns Lower Cretaceous (syn-rift) that there was extension of the basin and normal faults were acting. These differentiations could mean that a platform is probably in the north, close to Ammotopos, because most of the samples representing shallower waters are northern.
According to bibliography, a characteristic of Vigla limestones is that they contain calpionellids and radiolaria. Planktonic foraminifera made their first appearance in the basin in the middle Albian (middle Cretaceous). This is something to be highlighted because some samples had radiolaria, fossils that we were not able to determine the age of the respective samples. However, we know that they are collected from Vigla limestones.
The following Table (Table 7) contains the thin sectioned samples with the respective sections that they belong to, the determined fossils that were found in the thin sections, the FZ and the SMF that were defined, the age that derived from the determination of the fossils and the age according to the geologic map.
96
Table 7: A table resulting from the microfacies analysis and fossil recognition. The table contains all the samples and information about their age, the FZ and SMF that they belong and the ages according the geological map.
97 CHAPTER 8: CONCLUSIONS
The intense deformation recorded in sections 1b, 2, 4, 5, 6, 7, 8, 9 and in the Quarry (except the top) is owed to thrust activity. Their general direction is to the SW. Since we found the Paleocene formation (northern that we expected) in a restricted area, this means that it is not acceptable that the anticline was very broad (Figure 8.1 – shape 1). We suggest that it is located in a narrow zone. The changes from FZ 2 (deep-shelf) to FZ 4 (slope) could be due to faults between the sections or due to the faults in the sections. Due to these faults, it seems that stratigraphically the environment changes from shallower waters to deep-sea basin, during the sedimentation (syn-rift stage). Also, these faults could possibly bring sediments of different environments and different ages side-by-side. The changes from FZ 2 to FZ 4 refer mainly to Senonian limestones that show internal intense deformation to the sedimentation conditions, while Vigla’s limestones are represented from FZ 1 (deep-sea basin). These variations indicate the existence of a nearby platform. The different activation of the same faults could provide a mechanism that would control the depth of the basin (deeper or shallower). Age determination from thin sections analysis showed that some of the sections provide a different age from the age that the geological map indicates. Especially, sections 7 and 8, due to the fact that they were cut recently, the geological maps states that their age is Late Cretaceous, but we found out that some of them come from the Lower Cretaceous. Another example is that through the microfacies analyses the age of sample D14 has been determined as Lower Cretaceous (Vigla limestones) but the geological map states that its age is Late Cretaceous. A proposal about the section A-A’ of the geological map, including our data is given in Figure 8.1.
Figure 8.1: Section A-A’ after our analysis, that we state that: Eocene formation in area 1 is not there but even if it is, it is covered by the alluvial sediments and the age of the sediments in shape 2 is not Late Cretaceous but Lower Cretaceous.
98 We propose that the narrow zone of Eocene age (letter A on the map below) is located in a more northern position, at section 3 as shown in Figure 8.2. Is may, though, be covered by alluvial sediments. Letter B on the map represents an area that D14 was collected. Thus, the age of all this area in the sketched piece can be considered as Lower Cretaceous instead of Late Cretaceous (Figure 8.2). A strike slip in the area brings Vigla’s limestones into a lateral contact with the Senonian limestones. The possible direction of the strike slip is shown in Figure 8.2 with a black interrupted line (C). A proposal about how the area probably is, after our analysis is given in Figure 8.2.
C
Figure 8.2: A modified geological map with all the proposals that we made according to our analysis.
99 REFERENCES
ADAMS, A. E. & MACKENZIE, W.S., (1998): A Colour Atlas of Carbonate Sediments and Rocks under the Microscope. 180 pp. London: Manson Publishing; distributed by Oxford University Press.
AUBOUIN, J., (1959): Contribution à l’ étude géologique de la Grèce septentrionale: Le confins de l’ Epire et de la Thessalie. Annales Géologiques des Pays Helléniques, 10, 525.
AVRAMIDIS, P. & ZELILIDIS, A., (2001): The nature of deepmarine sedimentation and palaeocurrent directions as evidence of Pindos foreland basin fill conditions. Episodes, 24, 252-256.
AVRAMIDIS, P., ZELILIDIS, A., VAKALAS, I. & KONTOPOULOS, N., (2002): Interactions between tectonic activity and eustatic sea-level changes in the Pindos and Mesohellenic basins, NW Greece: Basin evolution and hydrocarbon potential. Journ. Petrol. Geol., 25, 53-82.
BORNOVAS, J., & RONDOGIANNI-TSIAMBAOU, T., (1983): Geological map of Greece, Scale: 1: 500,000. Athens: Institute of Geology and Mineral Exploration.
BOUDAGHER-FADEL M.K., (2008): Evolution and Geological Significance Larger Benthic Foraminifera: Department of Earth Sciences, University College London, London, WC1E 6BT, UK.
BOUDAGHER-FADEL M.K., (2012): Biostratigraphic and Geological significance of Planktonic Foraminifera: Department of Earth Sciences, University College London, London, WC1E 6BT, UK.
BOURLI, N., PANTOPOULOS, G., MARAVELIS, A.G., ZOUMPOULIS, E., ILIOPOULOS, G., POMONI-PAPAIOANNOU, F., KOSTOPOULOU, S., ZELILIDIS, A., (2019): Late Cretaceous to early Eocene geological history of the eastern Ionian Basin, southwestern Greece: A sedimentological approach: Copyright: © 2019 Elsevier Ltd. All rights reserved.
BRITISH PETROLEUM CO. LTD, (1971): The Geological Results of Petroleum Exploration in Western Greece. Special Report. Institute for Geology and Subsurface Research, Athens.
CAZZINI, F., DAL ZOTTO, O., FANTONI, R., GHIELMI, M., RONCHI, P. & SCOTTI, P., (2015): Oil and gas in the Adriatic Foreland, Italy. Journal of Petroleum Geology, 38 (3), 255- 279.
100 CHOQUETTE, P.W. & PRAY L.C., (1970): Geologic nomenclature and classification of porosity in sedimentary carbonates: AAPG Bulletin, v. 54/2, p. 207-244.
COWARD, M. P., DIETRICH, D. & PARK, R. G., (1989): Alpine Tectonics, Geological Society Special Publication No. 45, pp. 1-29.
DERCOURT, J., AUBOUIN, J., SAVOYAT, E., (1977): Reunion extraordinaire de la Societe Geologique de France en Grece: Bull. Soc. Geol. France, ser.7, 19: 5-70.
DEWEY, J.F., PITMAN, W.C.III, RYAN, W.B.F., & BONNIN, J., (1973): Plate tectonics and the evolution of the Alpine system. Geological Society of America Bulletin 84:3137–3180.
DOUTSOS, T., PIPER, G., BORONKAY, K., & KOUKOUVELAS, I., (1993): Kinematics of the Central Hellenides: Tectonics, 12, 936-953.
DOUTSOS, T., KOUKOUVELAS, I., ZELILIDIS, A., & KONTOPOULOS, N., (1995): Intracontinental Wedging and Post-Orogenic Collapse in the Mesohellenic Trough. Geologische Rundschau, 83, 257-275.
DUNHAM, R.J., (1962): Classification of carbonate rocks according to depositional texture. – In: Ham, W.E. (ed.): Classification of carbonate rocks. A symposium. – Amer. Ass. Petrol. Geol. Mem., 1, 108-171.
EMBRY, A.F. & KLOVAN, J.E., (1971): A late Devonian reef tract on northeastern Banks Island. N.W.T. – Bull. Canadian Petrol. Geol., 19, 730-781.
Encyclopedia Britannica, 2010
FLEURY, J.J., (1980): Evolution d’une platforme et d’un basin dans leur cadre alpin: les zones de Gavrovo-Tripolitze et du Pinde-Olonos, Soc. Géol. du Nord, Special Publication 4, 651.
FLUGEL, E., (1982): Microfacies Analysis of Limestones. -633pp., 78 figs., 53pls., 58 tabs., Berlin.
FLUGEL, E., (2004): Microfacies of Carbonate Rocks: Analysis, Interpretation and Application (Second Edition).
FLUGEL, E., (2010): Microfacies of Carbonate Rocks, Analysis, Interpretation and Application. Springer-Verlag, Berlin, 976 p.
FOLK, R.L., (1959): Practical classification of limestones. – Amer. Ass. Petrol. Geol. Bull., 43, 1-38.
101 FOLK, R.L., (1974): The natural history of crystalline calcium carbonate: Effect of magnesium content and salinity. J. Sed. Petrol., Tulsa, 44/1, 40-53.
GURK, M., TOUGIANNIDIS, N., OIKONOMOPOULOS, I., & KALISPERI, D., (2015): The basement structure below the peat-lignite deposit in the Philippi sub-basin (Northern Greece) inferred by electromagnetic and magnetic methods: Journal of Applied Geophysics, 115, 40-50.
IGRS-IFP (Institut de Géologie et Recherches du Sous-sol–Institut Français du Pétrole), (1966): Etude géologique de l’Epire (Grèce nord-occidentale): Editions Technip, Paris, France, 306 p.
KARAKITSIOS, V., & TSAILA-MONOPOLIS, S., (1988): Donnees nouvelles sur les niveaux superieurs (Lias inferieur-moyen) des Calcaires de Pantokrator (zone ionienne moyenne. Epire, Grece continentale). Description des Calcaires de Louros. Revue de Micropaleontologie, 31, 49-55.
KARAKITSIOS, V., (1992): Ouverture et inversion tectonique du basin Ionien (Epire, Grèce): Annales Géologiques des Pays Helléniques, series 1, v. 35, p. 185–318.
KARAKITSIOS, V., (1995): The influence of preexisting structure and Halokinesis on organic matter preservation and thrust system evolution in the Ionian basin, Northwest Greece. Article in AAPG Bulletin - January 1995, Copyright 1995, The American Association of Petroleum Geologists. All rights reserved.
KARAKITSIOS, V., & RIGAKIS, N., (1996): New Oil Source Rocks Cut in Greek Ionian Basin. Oil and Gas Journal, 94, (7), 56-59.
KARAKITSIOS, V., & RIGAKIS, N., (2007): Evolution and petroleum potential of Western Greece. Journal of Petroleum Geology, 30, (3), 197-218.
LATREILLE, M., SAVOYAT, E., & MONOPOLIS, D., (1962-1963): Arta sheet of I.G.M.E.
LOEBLICH, A., R., Jr., & TAPPAN, H., (1988): Foraminiferal Genera and their Classification: New York, Van Nostrand, v. 1, 970 p.; v. 2, 212 p.
LONGMAN, M.W., (1977): Factors controlling the formation of microspar in Bromide Formation J. Sed. Petrol., 47/1, 347-350.
LONGMAN, M.W., (1980): Carbonate diagenetic textures from nearshore diagenetic environments. Amer. Ass. Petrol. Geol. Bull., 64/4, 461-487.
102 MARAVELIS, A.G., KOUKOUNYA, A., TSEROLAS, P., PASADAKIS, N. & ZELILIDIS, A., (2014b): Geochemistry of Upper Miocene-Lower Pliocene source rocks in the Hellenic Fold and Thrust Belt, Zakynthos Island, Ionian Sea, western Greece, Marine and Petroleum Geology, doi: 10.1016/j.marpetgeo.2014.09.014.
MAVROMATIDIS, A., (2009): ‘Review of Hydrocarbon Prospectivity in the Ionian Basin, Western Greece’: Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 31:7,619-632.
MILLIMAN, J.D., (1974): Carbonates and the ocean. In Milliman, J.D. (Ed.), Marine Carbonates (Part 1): New York (Springer-Press), 3-15.
NIKOLAOU, C., (1986): Contribution to the Knowledge of the Neogene, the Geology and the Ionian and Pre-Apulian Limits in Relation to the Petroleum Geology Observations in Strophades, Zakynthos and Kephalinia Islands. Ph.D Thesis (Unpublished), University of Athens, Athens, 228.
NTOKOS, D., (2017b): Synthesis of literature and field work data leading to the compilation of a New geological Map—A review of geology of northwestern Greece. International Journal of Geosciences, 8(2), 205–236. doi:10.4236/ijg.2017.82009.
PAPASTAUROU, S., (1981): Sedimentological phosphoritic formations: classification- conditions of development, research in Greece. Bulletin of the Geological Society of Greece, 15, 13-31.
PAPASTAUROU, S., PERDIKATSIS, V., PETRIDOU-NAZOU, V., PITSIKAS, L., POMONI-PAPAIOANNOU, F., SKOURTSIS-CORONEOU, V., & VARTI-MATARANGA, M., (1985): Sedimentation of the Upper Cretaceous phosphorites of western Greece. 8th Meeting of the International Association of Sedimentologists, Abstract.
POMONI-PAPAIOANNOU, F., (2005): Notes of Carbonate Sedimentation (In Greek: Πομώνη-Παπαιωάννου, Φ., (2005): Σημειώσεις Ανθρακικής Ιζηματογένεσης)
RENZ, C., (1955): Die vorneogene stratigraphie der normal-sedimentaren formationen Griechenlands: Institute of Geological Subsurface Research, Athens, 637 p.
RICOU, L.E., DERCOURT, J., GEYSSANT, J., GRANDJACQUET, C., LEPVRIER, C. & BIJU-DUVAL, B., (1986): Geological constraints on the Alpine evolution of the Mediterranean Tethys. Tectonophysics. 123 (this vol.): 83-122.
103 ROBERTSON, A.H.F., CLIFT, P.D., DEGNAN, P. J. & JONES, G., (1991): Palaeogeographic and palaeotectonic evolution of the eastern Mediterranean Neotethys. Paleogeography, Paleoclimatology, Paleoecology, 87, 289–343.
SAVOYAT, E., & MONOPOLIS, D., (1962-63): Thesprotiko sheet of I.G.M.E.
SCHIEBEL, R., & HEMLEBEN, C., (2005): Extant planktonic foraminifera: A brief review. Palaontogische Zeitschrift.
SHOLLE, P.A. & ULMER-SHOLLE D.S., (2003): Petrography of Carbonate Rocks: Grains, textures, porosity, diagenesis. AAPG Memoir 77. Published by The American Association of Petroleum Geologist Tulsa, Oklahoma, U.S.A.
SKOURTSIS-CORONEOU, V., SOLAKIUS, N., & CONSTANTINIDIS, I., (1995): Cretaceous stratigraphy of the Ionian Zone, Hellenides, western Greece.
SMITH, J. G., (1977): Geology of the Ketchikan D-1 and Bradfield Canal A-1 quadrangles, south eastern Alaska: U.S. Geological Survey Bulletin 1425, 49 p., 1 pl., scale 1:63360.
SMITH, A. G. & WOODCOCK, N. H., (1982): Tectonic syntheses of the Alpine- Mediterranean region: A review. In: Alpine-Mediterranean Geodynamics. Am. Geophys Un., Geodynamics Series, 7, 15-39.
STANLEY S., M., (2009): Earth System History, Third Edition; by W. H. Freeman and Company.
TODO, Y., KITAZATO, H., HASHIMOTO, J., GOODAY, A., J., (2005): Simple Foraminifera flourish at the ocean’s deepest point. Science 307, 689.
TOUGIANNIDIS, N., (2009): Karbonat- und Lignitzyklen im Ptolemais-Becken: Orbitale Steuerung und suborbitale Variabilität (Spätneogen, NW Griechenland). Sedimentologische Fallstudie unter Berücksichtigung gesteinsmagnetischer Eigenschaften, PhD Thesis, 122p., Institute of Geology and Mineralogy, University of Cologne, Cologne.
UNDERHILL, J.R., (1989): Late Cenozoic deformation of the Hellenides foreland western Greece, Geol. Soc. Am Bull 101:613–634
VAKALAS, I. & ZELILIDIS, A., (2003): Paleogeographic reconstruction of Pindos Foreland basin during Middle Eocene – Upper Oligocene. PhD thesis, University of Patras.
WILSON, J.L., (1975): Carbonate Facies in Geologic History: Springer-Verlag, Berlin, 471 p.
104 WOLF, K.H., & CONALLY, J.R., (1965): Petrogenesis and paleoenvironment of limestone lenses in Upper Devonian Red Beds of New South Wales. Palaeo. -3,1, 69-111.
WRIGHT, V.P., & BURCHETTE, T.P. (eds., 1999): Carbonate ramps: an introduction. - Geol. Soc. London Spec. Publ., 149, 1-5.
ZELILIDIS, A., MARAVELIS, A.G., TSEROLAS, P & KONSTANTOPOULOS, P.A., (2015): An overview of the petroleum systems in the Ionian Zone, onshore NW Greece and Albania. Journal of Petroleum Geology, Vol. 38(3), July 2015, pp 331-348.
ZOUMPOULIS, E., (2016): Carbonate sedimentation at Cephalonia Island (Paxos Zone), during Mesozoic (In Greek: Ζουμπούλη, Ε., (2016): Η ανθρακική ιζηματογένεση στο νησί της Κεφαλονιάς, Ζώνη Παξών, στη διάρκεια του Μεσοζωικού).
GREEK
ΒΡΕΛΛΗ, Γ., ΒΕΚΙΟ, Π., ΕΥΘΥΜΙΟΠΟΥΛΟΣ, Θ., & ΣΠΥΡΙΔΩΝΟΣ, Ε., (2007). Τελική μελέτη Γεωθερμικού πεδίου Συκιών-Άρτας.
ΧΡΙΣΤΟΔΟΥΛΟΥ, Γ., (1982). Στρωματογραφία της Ελλάδας.
105