______Director Doc. Rer. Nat., P.Doc. Pedro Calixto Patarroyo Gama

______Codirector Ph.D. José María Jaramillo Mejía

II Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

María Fernanda Almanza Meléndez

Geologist, Universidad Nacional de Colombia Sede Bogotá

Universidad Nacional de Colombia

Facultad de Ciencias, Departamento de Geociencias

Bogotá D. C., Colombia

2017

Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

María Fernanda Almanza Meléndez Geologist, Universidad Nacional de Colombia-Sede Bogotá

Thesis presented as partial requisite to get the title of: Mágister en Ciencias-Geología

Director: Doc. Rer. Nat., P.Doc. Pedro Calixto Patarroyo Gama

Co-Director: Ph.D. José María Jaramillo Mejía

Research field: Stratigraphy

Universidad Nacional de Colombia Facultad de Ciencias, Departamento de Geociencias Bogotá D. C., Colombia 2017

To those who enjoy each piece of the cake, who love researching and never forget to be a good human being. To my beloved father, mother and brother

Acknowledgments

The main reason to do this master theses was the curiosity I had for some poorly-known old rocks. So, I feel deeply grateful with those Ordovician complicated rocks for allowing me discover something new.

I am grateful with my advisor Pedro Patarroyo for accompanings me during field work, and with my co-advisor professor José María Jaramillo, firstly, for the enlightining discussions during the best researching-breakfasts, secondly for guiding me to unlock dreams and build this master theses and its related peer-reviewed publications, lastly for introducing me to such metamorphic rocks and to encourage me to study them. I am also grateful with Francisco Javier Muñoz, Master candidate at Genève University, for their valuable assistance during field work. Thanks to my friends, fellow geologists, professors and my family for listening to my changing geological models.

Thanks to the Academic Vice-Rectory of the Universidad Nacional de Colombia (UN) for the Honours Degree Scholarship, the Welfare Science Faculty of the UN for supportting part of the academic exchange to Johannes Gutenberg Universität, the Geosciences Department of the UN for supportting geochemical analyses, the Spanish Mineco (CGL 2012- 39471) of the CSIC (Spain) for financing a research trip, and GmasLab (Bogotá) for supportting laboratory measurements.

Finally, many thanks in advance to those who will be next to me not only in the process of improving the geological model here proposed, but also for continuing publishing the information relevant to La Cristalina Formation. As Philippe ROSSI (President of the Commission for the Geological Map of the World) reflected about maps but here applied to the geological model of La Cristalina Formation:

“(…) never achieved just abandoned”

Paul Valery

Resumen y Abstract IX

Abstract

La Cristalina Formation is a low-grade polimetamorphic sedimentary unit that crops out in the eastern flank of the Central Cordillera, mainly to the south of La Cristalina Railway Station from which its the name was coined, and corresponds to the northwesternmost Ordovician sedimentary unit of Colombia. La Cristalina has not been defined according to the international procedure, despite “La Cristalina” term has been used for more than 87 years, when was published the first Ordovician sedimentary rocks of Colombia. Here 109 samples were handed, there were made 6 field trips, 8 creeks-sections, 5 cross-sections, 4 general composed stratigraphic columns, photo-geology, 64 thin sections, 39 geochemical and 2 geochronological analyses in order to correctly define the unit, following the international procedure of the International Commission on Stratigraphy. The unit was studied from the stratigraphic point of view, but as during the research fossils were found and igneous rocks analized, special studies were carried out. La Cristalina Formation is a very useful stratigraphic unit if considering the paleography of Gondwana and the tectonic location and its deformation meaning for the understanding of the tectonic processes that have occurred since Ordovician times. Here is suggested to continue using the name “La Cristalina” as a lithostratigraphic unit with a “Formation” rank. La Cristalina is defined here as all the strata concordant with Ordovician graptolitic metamudstones, composed of at least 4 facies and facies associations: metamudstones, siliciclastic intercalations, metamicrites and calcareous intercalations, those suggest an off shore and shoreface epicontinental marine sequence. Fossils occurrences reported here correspond to an assemblage of graptolites determined as Didymograptus cf. murchisoni (Beck), Pseudamplexograptus latus (Bulman) and Glossograptus hincksii (Hopkinson), together with phyllocarids and the first occurrences of Colombian foraminifera identified as Astrorhiza? sp. of international interest. La Cristalina overlies, with a faulted contact and an unconformity some Precambrian paragneisses, and underlies the Middle Jurassic rhyolites and andesites with a fault or an unconformity; besides with an unconformity underlies some Lower Cretaceous marine rocks (Fuquen et al., 2009) and Cenozoic alluvial deposits. Importantly, La Cristalina has an overspread low grade metamorphism that reached biotite isograde. It was intruded by 3 different igneous rocks: granodioritc to dioritic rocks (likely, related with the Middle to Upper Jurassic Segovia Batholith), rhyodacitic porphyries and granitoids with s-type affinities. These igneous rocks allow constraining the relative age of the metamorphism of La X Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Cristalina as pre-Jurassic and are the responsible of the La Cirstalina contact metamorphism. Structural complications and lacking of fossils makes complicated to unequivocally identify the sequence and calculate the total thickness. Lastly, metamudstones of La Cristalina can be correlated with the mudstones of El Hígado Formation. According to all the above, the Chapter 1 of this theses corresponds to the proposal to formally define the unit. Contenido XI

Resumen

La Formación La Cristalina es una unidad metasedimentaria polimetamórfica de bajo grado, que aflora en el flanco oriental de la cordillera Central, principalmente al sur de la Estación La Cristalina del Ferrocarril de Antioquia del cual proviene su nombre, además corresponde a la unidad ordovícica sedimentaria más noroccidental de Colombia. La Cristalina no había sido definida formalmente de acuerdo al procedimiento internacional recomendado, a pesar de que el término “La Cristalina” ha sido usado por más de 87 años, cuando fueron publicadas las primeras rocas ordovícicas de Colombia. Para este estudio se colectaron 109 muestras de mano y se hicieron 6 salidas de campo, 8 secciones por quebrada, 5 cortes geológicos, 4 columnas estratigráficas generalizadas, 64 secciones delgadas, 39 medidas geoquímicas y 2 geocronológicas. Lo anterior con el objetivo de definir formalmente la unidad estratigráfica, de acuerdo al procedimiento internacional recomendado por la Comisión Internacional Estratigráfica. A pesar de que el principal objetivo fue estudiar la unidad desde el punto de vista estratigráfico, durante el trabajo de investigación fueron encontrados fósiles y se analizaron rocas ígneas, por lo que se hicieron estudios adicionales. La Formación La Cristalina es una unidad estratigráfica muy útil si se consideran las reconstrucciones paleogeográficas de Gondwana y el significado que tiene su posición tectónica y su deformación en el entendimiento de los procesos tectónicos que han ocurrido desde el Ordovícico en la esquina noroccidental de Suramérica. Aquí se propone seguir usando el témino “La Cristalina” como una unidad litoestratigráfica con un rango de “Formación”. La Cristalina se define como todos los estratos concordantes con metalodolitas graptolíticas, que incluyen al menos 4 facies y asociaciones de facies: metalodolitas, intercalaciones siliciclásticas, metamicritas e intercalaciones calcáreas. Estas facies representan una secuencia epicontinental marina de costa afuera y de frente de playa. Las ocurrencias de fósiles reportadas aquí corresponden a una asociación de graptolitos determinados como Didymograptus cf. murchisoni (Beck), Pseudamplexograptus latus (Bulman) y Glossograptus hincksii (Hopkinson) con filocáridos, además de las primeras ocurrencias de foraminíferos en Colombia, Astrorhiza? sp., de interés internacional. La Cristalina suprayace con un contacto fallado e inconforme a unos paraneises precámbricos, e infrayace a riolitas y andesitas del Jurásico Medio con posiblemente un contacto fallado o una inconformidad, además infrayace con un contacto inconforme a unas rocas marinas del Cretácico inferior (Fuquen et al., 2009) y a depósitos aluviales del Cenozoico. De XII Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) forma escencial, La Cristalina tiene metamorfismo de bajo grado en toda la secuencia que incluso alcanza la isógrada de la biotita. La unidad fue intruída por al menos 3 unidades ígneas: rocas granodioriticas a dioriticas (probablemente, relacionadas con el Batolito de Segovia del Jurásico Medio a Superior), pórfidos riodacíticos de edad desconocida y granitos tipo-S del Paleoceno, estas rocas ígneas permiten inferir que el metamorfismo de La Cristalina es pre-Jurásico y son las responsables del metamorfismo de contacto que tiene la unidad ordovícica. Complicaciones estructurales y la carencia de fósiles hacen difícil conocer inequívocamente la totalidad de la sucesión y el espesor de la unidad. Metalodolitas con graptolitos de La Cristalina se correlacionan litoestratigráficamente por posición y litología con las lodolitas graptolíticas de la Formación El Hígado. Finalmente, el Capítulo 1 de esta tesis corresponde a la propuesta de definición de la unidad. Contenido XIII

Content

Pág.

Resumen ...... XI

Figures ...... XVI

Tables ...... XVII

Introduction ...... 19

1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina Formation, Puerto Berrío (Colombia) ...... 28 1.1 Introduction ...... 30 1.1.1 Location and access ...... 30 1.1.2 Generalities of La Cristalina Formation ...... 32 1.1.3 Tectonic importance of La Cristalina Formation: Why it is a very useful stratigraphic unit ...... 35 1.2 Methodology ...... 37 1.3 Results ...... 38 1.3.1 Geomorphologic expression...... 38 1.3.2 Stratotype ...... 39 1.3.3 Facies description ...... 43 1.4 Discussion ...... 65 1.4.1 Invalid definitions ...... 65 1.4.2 Composed type locality ...... 65 1.4.3 Stratigraphic relations ...... 65 1.4.4 Age ...... 70 1.4.5 Rocks description and petrogenesis ...... 70 1.4.6 Lithocorrelation ...... 73 1.4.7 Stratigraphic classification: Rank ...... 74 1.4.8 Name ...... 74 1.4.9 Formalization ...... 76 1.5 Conclusions ...... 76 1.6 References ...... 78

2. New graptolite fossil localities of La Cristalina Formation ...... 83 2.1 Introduction ...... 83 2.1.1 General approaches of La Cristalina Formation ...... 83 2.1.2 Ordovician sedimentary/low grade metasedimentary rocks in Colombia86 2.1.3 La Cristalina Formation in the eastern flank of the Central Cordillera... 87 2.1.4 Ordovician transgression in Colombia ...... 88 2.1.5 La Cristalina biostratigraphy and age ...... 89 XIV Título de la tesis o trabajo de investigación

2.2 Methodology ...... 89 2.3 Results ...... 89 2.3.1 Metasedimentary succession bearing graptolites ...... 89 2.3.2 Graptolites occurrences ...... 92 2.4 Discussion ...... 95 2.4.1 Age of La Cristalina Formation ...... 95 2.4.2 Implications of La Cristalina graptolite occurrences in Colombia ...... 96 2.4.3 Paleogeographical implications in South America ...... 97 2.4.4 Colombian tectonic scenario ...... 99 2.5 Conclusions ...... 100 2.6 References ...... 100

3. Colombian first ocurrences of Ordovician foraminifera: La Cristalina Formation105 3.1 Introduction ...... 105 3.1.1 Ordovician foraminifera ...... 105 3.1.2 La Cristalina Formation ...... 107 3.1.3 La Cristalina biostratigraphy ...... 109 3.2 Methodology ...... 110 3.3 Results ...... 110 3.4 Discussion ...... 117 3.4.1 Why foraminifera should be considered Ordovician ...... 117 3.4.2 Paleontological and paleogeographical issues ...... 117 3.4.3 Lithologic facies, sedimentary setting and metamorphism ...... 119 3.5 Conclusions ...... 119 3.6 References ...... 120

4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic porphyries and Paleocene S-type granitoids intruded La Cristalina Formation: Petrological approach and stratigraphic discussion ...... 123 4.1 Introduction ...... 123 4.2 Methods ...... 130 4.3 Results ...... 131 4.3.1 Rock descriptions at outcrop, hand-sample and thin-section scale .... 131 4.3.2 Geochemical analyses ...... 143 4.3.3 Pb dating ...... 149 4.4 Discussion ...... 150 4.4.1 Petrological approaches ...... 151 4.4.2 Stratigraphic nomenclature ...... 155 4.4.3 Critical aspects in relation with La Cristalina Formation ...... 158 4.5 Conclusions ...... 159 4.6 References ...... 160

5. Conclusions ...... 163

6. Future researching opportunities...... 166

A. Supplemental Material 1: Stops, hand-samples and lineaments maps ...... 167

B. Supplemental Material 2: Petrography ...... 170

C. Supplemental Material 3: X Ray Difraction ...... 175 Contenido XV

D. Supplemental Material 4: Precambrian paragneisses ...... 179

E. Supplemental Material 5: Bentonites ...... 180

F. Supplemental Material 6: Gechrological data ...... 181

References ...... 183

Contenido XVI

Figures

Figure 1-1 Geological map of the studied area (…)...... 32 Figure 1-2. Geological Map of La Cristalina Formation (…)...... 40 Figure 1-3 Creek-sections in Las Iglesias and La Miquera creeks (…)...... 41 Figure 1-4 Cross-sections in Las Iglesias and La Miquera creeks (…)...... 42 Figure 1-5 Composed generalized columns of La Cristalina Formation (…)...... 43 Figure 1-6 Outcrops and hand-samples of metamudstones facies (…)...... 47 Figure 1-7 Thin-section pictures of dark metamudstones facies (…) ...... 48 Figure 1-8 Outcrop and hand-sample pictures of silicilastic intercalations facies (…)...... 53 Figure 1-9 Thin-section pictures of siliciclastic intercalations facies (…) ...... 55 Figure 1-10 Outcrop and hand-sample pictures of metamicrites facies (…)...... 57 Figure 1-11 Thin-section pictures of metamicrites facies (…)...... 58 Figure 1-12 Outcrop and hand-sample pictures of calcareous intercalations facies (…)...... 62 Figure 1-13 Thin-section pictures of calcareous intercalations facies association (…)...... 64 Figure 1-14 Stratigraphic relations (nature of contacts) of La Cristalina Formation (…)...... 68 Figure 2-1. Ordovician sedimentary and low-grade metasedimentary (…)...... 84 Figure 2-2. Geological Map of La Cristalina Formation (…)...... 85 Figure 2-3 Outcrops, hand-sample and thin-section pictures of La Cristalina (…) ...... 91 Figure 2-4 Composed generalized columns of La Cristalina Formation (…)...... 92 Figure 2-5 New graptolite assemblage of La Cristalina Formation (…)...... 94 Figure 3-1 Geological Map of the Ordovician La Cristalina Formation (…)...... 108 Figure 3-2. Outcrop and hand-samples pictures of metamudstones (…)...... 111 Figure 3-3 Polished 3D hand-sample (…)...... 112 Figure 3-4 Thin-section pictures of samples where foraminifera were found (…)...... 114 Figure 3-5 Benthic agglutinated foraminifera in thin-section (…)...... 116 Figure 4-1 Geological map of the studied area (…)...... 126 Figure 4-2 Geological Map of the studied area (…)...... 126 Figure 4-3 Outcrops and hand-samples of granitoids (…)...... 134 Figure 4-4 FLC-02 granitoid thin-section photographs (…)...... 135 Figure 4-5 FLC-02 granitoid thin-section photographs (…)...... 136 Figure 4-6 FLC-16 granitoid thin section photographs (…)...... 137 Figure 4-7 Thin-section pictures of granodioritic to dioritic rocks (…)...... 142 Figure 4-8 Rhyodacitic porphyries (CLC-18) at outcrop and hand-sample (…)...... 142 Figure 4-9 Minor and major elements diagrams for granitoids (…)...... 147 Figure 4-10 Spider and REE diagrams for granitoids (…)...... 148 Figure 4-11 Harker diagrams of granitoids (…)...... 149 Figure 4-12 Concordia diagrams and frequencies histogram of granitoids (…)...... 150 Figure 4-13 Contact metamorphism of La Cristalina Formation (…)...... 159 Contenido XVII

Tables

Table 1-1 Main published contributions to La Cristalina Formation knowledge ...... 33 Table 1-2 Main published contributions to La Cristalina Formation biostratigraphic (…) .. 34 Table 1-3 Selected thin-section descriptions of both of metamudstones facies (…)...... 49 Table 1-4 Selected thin-section descriptions of metamicrites facies and (…) ...... 59 Table 1-5 Stratigraphic relations (nature of contacts) of La Cristalina Formation (…) ...... 66 Table 1-6 Names used to refer to La Cristalina Formation since 1911 up to now...... 76 Table 2-1 Main published contributions to La Cristalina Formation biostratigraphical(…) 88 Table 2-2 Fossil localities, identification of graptolite assemblages and age (…) ...... 96 Table 3-1 Main published contributions to the biostratigraphic knowledge (…)...... 109 Table 3-2. Petrographic description of selected samples (…)...... 114 Table 4-1. Selected petrographic description of granitoids (…)...... 137 Table 4-2 Major, minor and trace elements measurements by XRF of granitoids (…). .. 144

Introduction

Preliminary information

This theses is structured in 4 chapters: the 1) “Stratigraphic definition of the Lower to Middle Ordovician La Cristalina Formation, Puerto Berrío (Colombia)”, 2) “New graptolite fossil localities of La Cristalina Formation”, 3) “Colombian first ocurrences of Ordovician foraminifera: La Cristalina Formation” and 4) “Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic porphyries and Paleocene granitoids intruded La Cristalina Formation: Petrological approach and stratigraphic discussion”.

Chapters have a research-paper structure, therefore each one has an abstract, introduction, results, discussion, conclusion and acknowledgements, in such way each chapter has its own contextualization information in a highly condensed way. The dissertation aim is to publish chapters in peer-reviewed journals and is the reason by which it was written in English. Extracts of chapter 2 were submmited to an international peer-review journal, and extracts of chapter 2 and 3 were presented at the 34th International Geological Congress in Cape Town (South Africa) in August, 2016 (Almanza et al., 2016).

Research issues

La Cristalina Formation was the first Ordovician sedimentary succession published in Colombia (87 years ago, Harrison, 1930) and one of the first in South America (Trumpy, 1943; Aceñolaza, 1980). Few cartographical works had been done in the region where La Cristalina Formation crops out (Harrison, 1930; Botero, 1940; Feininger et al., 1972; GRP, 2008; UPTC, 2012; Fuquen et al., 2009; Fonseca et al., 2011).

La Cristalina Formation is critical because its location to the east of the Otú-Pericos Fault in the Central Cordillera, that have been long proposed as a terrane boarder, to the west

20 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) the Tahamí Terrane and to the east Chibcha Terrane (e.g. Toussaint & Restrepo 1989, and subsequent changes cf. Restrepo et al., 2011) (Figure 1).

Unfortunately, little research has been done focused specifically on the Ordovician unit (e.g. Almanza et al., 2013). Missing studies make difficult to know with precision features such as age (sedimentary and metamorphic), sedimentary petrogenesis, metamorphic characteristics and detailed spatial relationships with the adjacent units. Those characteristics are part of the basic stratigraphic knowledge we should have of the Colombian geological units. As a consequence, the stratigraphic unit has not been formally defined yet according to the International Comission on Stratigraphy (ICS) recommendations (Salvador, 2013), despite the term La Cristalina Formation has been used in some published texts (e. g. Mojica & Villarroel, 1990, Borrero et al., 2006) without following the international recommended procedure.

Research importance

The basic stratigraphic questions of La Cristalina Formation have not been solved yet. According to the International Stratigraphic Guide (Salvador, 2013), these questions include the understanding of the stratigraphic relations (spatial-relation with adjacent rock bodies: what is below, above, next, etc.), rocks description, as well as correlation and classification (kind of unit and rank).

Bearing in mind the aforementioned, this proposal obtained a better holistic stratigraphic model that allowed to define formally the lithostratigraphic unit according to ICS´s recommendations. Below, there are explained other issues that justified this research:

—Geological maps published (I-9 Quadrangle at scale of 1:100 000, and 133 Puerto Berrío and 149 Puerto Serviez sheets at the same scale) are not enough detailed, hence this research made a better map using shaded relief images, aereal photographs and field work, that included creek-sections at ca. 1:10 000.

—La Cristalina did not have stratigraphic columns in regions with the best outcrops with the complete succession known and where the Ordovician fossils were found. Besides, despite there are some field and petrographic descriptions of the rocks, I did the most 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 21 complete descriptions, including approaches to the depositional setting, Ordovician relative sea level changes, and another basic sedimentary knowledge.

—Representative quantitative analysis have not been donde using modern technics such as X Ray Diffraction and X Ray Fluorescence. Those were performed with the aim of make a geochemical description of La Cristalina rocks and adjacent rock bodies, in order to have a better understanding of the petrogenetical processes.

—Depositional age was determined by using graptolites that required an urgent revision to the light of: 1) the Areginian age graptolites reported, neither updated nor enough age fine-resolution as can be obtained with graptolites (e.g. stage resolution), 2) the GSSP´s complete definition in 2009 that includes all the Ordovician stages, 3) review made by J.C. Gutiérrez-Marco in Borrero et al., (2006) which suggests different species in comparison with the original paleontological classification, 4) the recent discovery of the first Ordovician foraminifera in Colombia (Almanza et al., 2013) and 5) fossils occurrences not previously taken into account. Although bioestratigraphy was not a specific objective of this research, paleontological occurrences took a part in the basic stratigraphic description. Paleontological occurrences were determined by experts of corresponding groups, foraminifera and graptolites.

—From the regional point of view, if we do not have basic stratigraphic studies, we would not know with certainty the stratigraphic meaning of the Ordovician La Cristalina Formation to the western of Gondwana.

In addition, the study of La Cristalina is critical because it is located to east and very close to a long propossed geological terrane boarder (Restrepo et al., 2011), that is why, indirectly, the understanding of the metamorphic and deformation characteristics can help us to describe the relation between La Cristalina and the tectonic processes that happened since Ordovician times up-to-now.

—Although the lithostratigraphic unit has not significant economic interest, it is necessary to point out that minery of marbles was done by Argos as early as 1940 (Botero, 1940; Feininger et al. 1972), and so, there is a possibility to have calcareous resources. As well mineralization ocurrences due to the presence of igneous intrusions into the La Cristalina Formation could be important. 22 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Considering the energetic resources, many authors have pointed out the increasingly need to research the Paleozoic units as a possible hydrocarbon source rocks (e. g. Barrero et al., 2007; Pinilla et al., 2006; Arminio et al., 2013; Petrotech Engineering, 2007). Taking into account that: 1) in the Middle Magdalena Valley (MMV) has been an increasing petroleum exploration and occurrences of productive wells, and that 2) the Ordovician unit has stability temperatures higher than the field of oil-window, it is necessary to know more about the sedimentary and metamorphic characteristics, in that way we can decipher the roll of the Ordovician unit in the petroliferous systems of the MMV.

According to the aforementioned, the missing knowledge, the necessity of revision and the economical roll of La Cristalina Formation justifies this project.

Objectives

General

Following the definition of the International Stratigraphic Guide (Salvador, 2013), the main objective of this theses was to know the stratigraphic relations of La Cristalina Formation; describe the succession, and correlate and classify the unit, including giving a formal name. The above with the main objective of define formally the lithostratigraphic unit, according to the International Commision on Stratigraphy recommendations. As well, all the aforementioned helped to propose a better geological model.

Specific

—To know the stratigraphic relations of the Ordovician unit

—To describe La Cristalina Formation succession (as sedimentary and metamorphic rocks).

—To check the depositional age of La Cristalina Formation and obtain an approach to the metamorphic age.

—To correlate La Cristalina Formation with other Ordovician units in Colombia. 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 23

—To classify La Cristalina Formation as a formal stratigraphic unit.

—To assign the formal name La Cristalina Formation, according with the Internationa Cammision on Stratigraphy´s procedure.

Methodology —6 field trips were done, 8 creek-sections, 4 composed schematic stratigraphic columns, and 5 cross-sections.

—109 samples were handed

—64 thin sections were done. Petrography included microtectonic descriptions.

—Geochemical measurements with X Ray Fluorescence and X Ray Diffraction, a total of 39.

—U-Pb LA-ICP-MS geochronology of the some igneous bodies that intruded the Ordovician unit. Zircons of 20 samples of La Cristalina Formation, Precambrian paragneisses, granodioritic to dioritoc rocks and rhyodacitic porphyries are being measured by means of U-Pb LA-ICP-MS at University of Arizona, but unfortunately results are not ready by the time for this manuscript had to be delivered. Only 2 measurements are presented.

—An academic exchange at the Johannes Gütenberg Universität Mainz (Germany) was done in order to take classes (Metamorphic Petrogenesis, Igneous Petrogenesis and Microtectonics), learn analitic technics and have an assesory with the professor C. W. Passchier.

The above mentioned methodology allowed to answer effectively the basic stratigraphic questions of La Cristalina Formation: The point 1 allowed to know the stratigraphic relations (spatial) of the Ordovician unit; points 2, 3, 4, 5 and 6 allowed to describe La Cristalina succession (petrological characteristics and cross-cut relations). In adittion, together with the adequate review, the unit was correlated with another equivalent units of Colombia and South America, as well as classify the lithostratigraphic unit, adjusted to the international recommended procedure.

Generalities

La Cristalina Formation is located in the eastern flank of the Central Cordillera, to the southeast of Antioquia Department (Figure 1). 24 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Figure 0-1 Geological map of the studied area. The white rectangle shows the studied area in the eastern flank of the Central Cordillera of Colombia, next to the Middle Magdalena Valley. It should be highlighted the different basements, to the west of the Otú Fault a Triassic metamorphic complex and to the east some Neoproterozoic gneisses. At the studied are the critical Otú Fault is displaced by the Palestina Fault System. Map modified from Gómez et al. (2015) after Feininger et al. (1970). Location map modified from Gómez & Almanza (2015). 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 25

In Figure 2 can be seen the Geological Map of La Cristalina Formation, together with the structural data obtained in field and digitalized from Feininger et al. (1970). The map was modified from Gómez et al. (2015) after Feininger et al. (1970). To modify it field work, photointerpretation and shaded relief images with a resolution of 30 m (USGS, 2004) were used in a conservative way.

In Table 1 can be observed the procedures followed by each sample. On the other hand, in the Supplemental Material 1 can be seen the stops, hand-samples and lineaments maps; in the Supplemental Material 2 and 3, the petrography; in the Supplemental Material 4, information about paragneisses underlying La Cristalina Formation; in the Supplemental Material 5 information about possible bentonites including geochemical measurements, and in the Supplemental Material 6, geochronological data. Rocks were described as sedimentary, despite de low metamorphism, but when necessary metamorphic terms were used.

Further and complete information of La Cristalina Formation can be seen in each chapter, according to each subject. 26 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Figure 0-2 Geological Map of La Cristalina Formation, including the digitalized structural data of Feininger et al. (1970). Map modified from and Gómez et al. (2015) after Feininger et al. (1970). Legend can be seen in Figure 0-1. 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 27

Table 0-1 Procedures performed with each sample. XRF: X Ray Fluorescense, %TOC: Total Organic Carbon percentaje, XRD: X Ray Difraction, U-Pb dating by LA-ICP-MS means.

28 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Abstract

The Floian to early middle Darriwillian La Cristalina Formation is a low-grade metasedimentary unit that has not been defined according to the international procedure, despite “La Cristalina” term has been used for more than 88 years and deserves the stability given by proper formalization. It crops out in the eastern flank of the Central Cordillera, is located to the southeast of the Antioquia Department and mainly to the south of La Cristalina Railway Station from which the name was coined. 109 hand-samples were handed, and 6 field trips, 8 creeks sections, 5 cross-sections, 4 general stratigraphic columns, photogeology and 64 thin sections were made, as well as 39 geochemical measurements in order to correctly define the unit, following the international procedure recommended by the ICS. La Cristalina Formation is a very useful stratigraphic unit when considering the paleography of Gondwana and the tectonic location and its deformation meaning for the understanding of the tectonic processes that have occurred since Ordovician times. Here is suggested to continue using the name “La Cristalina” as a lithostratigraphic unit, with a “Formation” rank. La Cristalina is defined here as all the strata concordant with graptolitic metamudstones, composed of at least 4 facies and facies association with a key overspread low-grade metamorphism: metamudstones, siliciclastic intercalations, metamicrites and calcareous intercalations. Facies together with structures and fossils suggest an off-shore to shoreface epicontinental marine sequence. Critically, La Cristalina Formation has an overspread low grade metamorphism that reached the biotite isograde as the highest grade. La Cristalina overlies with a faulted contact some Precambrian paragneisses and underlies the “Volcanic Rocks” (sensu Feininger et al., 1970) with likely either a fault or an unconformity; also it underlies some Lower Cretaceous marine rocks (Fuquen et al., 2009) and Cenozoic alluvial deposits with unconformable contacts. The unit was intruded by 3 different not-deformed igneous rocks with Middle Jurassic-Paleocene ages, in addition to one not determined. Structural complications and lacking of fossils makes difficult to unequivocally identify the sequence and calculate the total thickness. Lastly, the metamudstones of La Cristalina Formation 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 29 can be correlated with the mudstones of El Hígado Formation, because lithological and stratigraphic position. 30 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

1.1 Introduction

According to the recommendations of the International Stratigraphic Guide (The Guide) (Salvador, 2013) of the International Commission on Stratigraphy (ICS), constituent of the International Union of Geological Sciences (IUGS), in order to define a stratigraphic unit it is necessary to: 1) know stratigraphic relations, 2) describe the rocks, 4) make a stratigraphic correlation and 5) classify the stratigraphic unit, including coining a name. Therefore, the purpose of this paper is to define La Cristalina Formation following the international procedure and also taking into account the North American Stratigraphic Code (the Code) (NASC, 2005) which is up dated in comparison with the Guide and has the advantage of be armonious and complementary with the Guide, at least for this intention.

1.1.1 Location and access

La Cristalina Formation crops out around 45 km2, it is located to the southwest and west of Puerto Berrío Town (Figure 1). The largest outcrops are found to the south of the La Cristalina Railway Station (LCRS). La Cristalina Formation is the northwesternmost Ordovician unit in Colombia.

To arrive to LCRS can be taken the motomesa (it goes on the railroad) from Puerto Berrío Railway Station, but also an unpavement road from the dairy factory called La Quesera in the motorway Puerto Berrío-Medellín ca. 20 km. Also it can be taken an unpavemented road to Puerto Serviez and La Sierra from Puerto Berrío. Once in LCRS the most suitable way to arrive to the outcrops is following narrow unpaved roads to farms (such as La Gabriela or Los Ángeles). The best exposures can be found in creeks. It should be taken into account seriously to visit the area during the dry season. Going by pick-ups, food, riding on motorcycles or on mules could be good options too. In addition and unfortunately, violence is a long fact habitants have to deal with, as well as geologist, therefore is recommended to ask respective authorities before get in. 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 31

32 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Figure 1-1 Geological map of the studied area. The white rectangle encloses the studied area, to the southwest of Puerto Berrío. Note the Chibcha and the Tahamí terranes (Restrepo et al., 2011). Map modified from Feininger et al. (1972) and Gómez et al. (2015). Location map to the lower right modified from Gómez & Almanza (2015)

1.1.2 Generalities of La Cristalina Formation

La Cristalina was the first Ordovician metasedimentary succession published in Colombia (Harrison, 1929), and one of the first in South America (Trumpy, 1943; Aceñolaza, 1980). La Cristalina is widely recognized as a lithostratigraphic unit with “Formation” rank as early as 1945 (Alvarado et al., 1945), despite La Cristalina has not been formally defined according to the international stratigraphic procedure. The main contributions to La Cristalina Formation knowledge can be seen at Table 1. 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 33

Table 1-1 Main published contributions to La Cristalina Formation knowledge

34 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Briefly, the first geologist that mentioned Paleozoic rocks in the Central Cordillera was Ospina (1911), according to stratigraphic field relations and without mentioning any fossil occurrences. Scheibe et al. (1919) was first who discovered possible fossils in, likely, Paleozoic slates intruded by granitic rocks very similar to La Cristalina Formation and at the outcrops between Barbosa and Puerto Berrío Railway Stations. Afterwards, Harrison (1929) reported the first graptolitic fossil association (4 species) found in 1927 by D´Arcy Exploration Co. geologists. Since then, other 5 occurrences has been reported until now (Table 2), being the last that of Almanza et al. (2016) (cf. chapter 2), together with the first Ordovician foraminifera in Colombia and the second in South America (Nestell et al., 2011). Importantly, Botero (1940) found fossils and made the first hand-sketch map of the unit of the northern outcrops, as well as he described for the first time briefly the main facies of the total succession.

Table 1-2 Main published contributions to La Cristalina Formation biostratigraphic knowledge. Colours according to the International Stratigraphic Chart (2016).

Cartographical works have contributed the most to the understanding of La Cristalina Formation. Feininger et al. (1970) prepared the Eastern of Antioquia Quadrangle at scale of 1:100 000, this is one of the most important works, because, mainly, the excellent field observations and the proposed geological model of the region. That map almost has not 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 35 changed since then. In 2009 and 2011 were made the actualization mapping of the area (sheets 139 Puerto Berrío and 142 Puerto Serviez) at 1:100 000 by the Servicio Geológico Colombiano, including the first stratigraphic column of part of the unit including some thin-sections. Finally, Almanza et al. (2013) did the most complete petrological study by that time, the first formal research with the objective of studying specifically the unit, and Almanza et al. (2016) presented the most complete biostratigraphic studio, including new fossils occurrences and the best age for La Cristalina Formation.

1.1.3 Tectonic importance of La Cristalina Formation: Why it is a very useful stratigraphic unit

As was shown in Figure 1, La Cristalina Formation location is critical because crops out to the east of the Otú-Pericos Fault in the Central Cordillera, that has been long proposed as a terrane boarder, to the west the Tahamí Terrane and to the east Chibcha Terrane (e.g. Toussaint and Restrepo 1989, and subsequent changes cf. Restrepo et al., 2011). In the following it will be discussed some critical facts about it.

It should be highlighted that Ospina (1911) and Botero (1940) proposed that La Cristalina Formation belonged to a metamorphic suite in the axial Central Cordillera, and the former author used the term Palaeozoic rocks. Other authors such as Nelson (1959) considered that La Cristalina Formation should be included in the Palaeozoic Cajamarca metamorphic unit in the Central Cordillera, those Paleozoic metamorphic rocks were described to the south and at Cajamarca Town latitude. However, after Feininger et al. (1972) observations it was clear that La Cristalina Formation did not belong to those metamorphic units at the Central Cordillera. Currently, it was proposed that those metamorphic units of the Central Cordillera are rather better Triassic metamorphic units, hence La Cristalina Formation cannot be related in such straight forward way to those units, because critical faults in between (cf. Restrepo et al. 2011; Gómez et al., 2015).

Many questions remain unanswered, when considering that terrane border, such as why some Colombian Ordovician sedimentary units outcrop very close to that boarder and to the east of the Otú Fault are not deformed or have a very low grade of metamorphism (e.g. La Cristalina succession and El Hígado Formation), whereas others to the east of the terrane boarder even have reached amphibolite metamorphic facies as in the Santander Massif e.g. Silgará Formation (sensu Ward et al., 1973 with an Ordovician 36 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) protolite age according to Mantilla et al., 2016 that used detrital U-Pb data in the San Pedro phyllites). To contextualize that question will be discussed some tectonic proposals.

On one hand, it should be considered the preliminary paleomagnetic approaches of Bayona et al. (2010), who suggested that Colombian Ordovician units, to the west Amazonian Craton, may be deposited to the south (probably current Peru or Bolivia latitude) and then they were tectonically transported to the north, in greater magnitude during Late Triassic times by oblique subduction. That model is in clear contrast with Mojica & Villarroel (1990) that suggest a continuous Ordovician deposition between Orinoquian region and Andes region.

On the second hand, it has been proposed a “Lower” Palaeozoic (Ordovician-Silurian, named as well as Quetame event, Caperonensis or Famatinian Orogenies) orogeny to the northwestern of South America (e. g. Restrepo-Pace and Cediel, 2010 and references there in), although evidences that occurred in the late Silurian are provided by Forero (1991), and Aleman & Ramos (2000) proposed a Late Ordovician Orogeny in the northwestern of South America caused by the Gondwana assemblage and collission with Laurentia. Likely, Feininger et al. (1972) also proposed a deformational event during what he called as “Lower” Palaeozoic, responsible of La Cristalina and Silgará formations metamorphism. Thus some key unraveled questions are: what is the age and to which geological event(s) can be related the metamorphism of La Cristalina, and what is the relation between not-metamorphic El Hígado Formation and the metamorphic La Cristalñina Formation with the Silgará amphibolite facies metamorphism.

The Tahamí Terrane has a well-constrained Triassic metamorphism (e.g. Villagómez et al., 2011; Restrepo et al., 2011) (although some Jurassic ages have been proposed by e.g. Blanco-Quintero et al., 2014 or Permian by Vinasco et al., 2006) that is, likely, due to subduction setting to the western of Gondwana (e. g. Restrepo et al. 2011) or less-well constrained by continent collision with Laurentia (Vinasco et al., 2006). It has also suggested that a Permian magmatism in the Central Cordillera was associated with a continental convergent-arc (I-granitoids), followed by extensive anataxis during Triassic times (S-granitoids) (e.g. Cardona et al., 2011). Similarly, Spikings et al. (2015) considers a subduction-related magmatism during Permian-Early Triassic, followed by an extensive rifting, that could account for the Triassic S-granites, in the Central Cordillera (and 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 37 subsequent disassemblage of Pangea). The last authors also proposed a Late Triassic- Jurassic subduction, accretion during Late Cretaceous and current subduction. Accretion and ongoing subduction drives the early Andean Orogenesis responsible of the Central Cordillera uplifting from Late Cretaceous-Paleocene (e. g. Villagómez and Spikings, 2013; Caballero et al., 2013).

Therefore, having a low-grade and undoubtedly Ordovician rocks so close to those regional and critical faults is tremendously useful to unravel the tectonic process, such as translation, accretion and orogenic mechanisms discussed above, between others events that have occurred since Ordovician times to the west of Gondwana. This clearly support the usefulness of La Cristalina stratigraphical unit.

1.2 Methodology

6 field trips have been done to Puerto Berrío (Antioquia) in the eastern flank of the Central Cordillera of Colombia. 109 hand-samples were collected and 64 thin-sections were made at GMAS S.A.S. laboratories and in the Universidad Nacional de Colombia-Bogotá.

Rocks description recorded here according to Fettes & Desmons (2007) and Folk (1980) and Dunham (1962) in Nichols et al. (2009). Mineral abbreviations, metamorphic concepts and another terms ( e.g. metamorphic grade, P/T relation, isograde, etc.) according to Fettes & Desmons (2007), with the aim of following the recommendations of International Union of Geological Sciences (IUGS) and associated sub-commissions. Classification of thin-section samples (cf. Supplemental Material 2) was according to Fettes & Douglas (2007), following the recommendations of the Subcommission on Nomenclature of Metamorphic Rocks. Readers can find that roundness, shape descriptions or other genuine sedimentary descriptions were not done, because the metamorphic re- crystallization of grains that makes doubtful if those correspond to sedimentary or metamorphic characteristics. Mineral assemblage and temperature stability conditions were determined according to Spears (1993) and Vernon and Clarke (2008).

There were done field work following the conventional procedures, sampling according with the local characteristics. Furthermore specific visits were done to find the stratigraphic relations with other rock bodies, looking for contacts and different facies. 38 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Cross-sections and composed general columns were prepared by using creek-sections (visiting each single outcrop) approximately at a scale of 1:10 000 and controlling by using photogeologic observations and shaded rielief images (USGS, 2002). Nevertheless, information of the visited localities was plotted at 1:25 000 and, at the map, was plotted at 1:100 000. Columns have to be considered as generalized, because structural complications made difficult to prepare something meaningful enough at this stage of the knowledge of La Cristalina. Columns were prepared using all the information available: firstly creek-sections, hand-samples, thin-sections, fossil occurrences, etc.

X Ray Fluorescense measurements were done at the Universidad Nacional de Colombia- Bogotá. Samples were measured in a MagixPro PW-2440 Phillips XRF Spectrometer, with Ro tube, and maximum 4 KW power. The spectrometer has a resolution of 200 ppm for heavy metallic elements. Powdered samples of <100 µm were heated to 105 °C for 12 hours and mixed with wax (10:1) (MERK Laboratory), then were pressed hydraulically until 120kN. Those were measured with SEMIQ-2016. Semiquantitative analyses were done with IQ (11 scannings). H, C, Li, Be, B, N, O and trasuranian elements were not measured.

X Ray Difraction measurements were done at GMAS S.A.S. using BrukerD8 Advance - Series I- X-ray diffractometer with the VANTEC-1 PSD detector. 5 g of the sample were used with a size lesser than 44µm, afterwards on an alluminium disc the sample was measured and the wt. percentajes of minerals were obtained.

1.3 Results

In the following will be defined La Cristalina Formation fulfiling the recomendations of the chapters 3-5 of Guide (Salvador, 2013) and the articles 1-3,5-15, 22-24 and 30 of the Code (NASC, 2005).

1.3.1 Geomorphologic expression La Cristalina Formation consists of low lands, with less than 500 m of high, with small hills most of them showing clearly the bed-strike. Calcareous facies (cf. 1.3.3) are the most prominent layered-bodies that form strong lineations along the strike of beds, as seen in Figure 2 to the southwest, which makes easy to differentiate the calcareous and 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 39 siliciclastic facies. Although the siliciclastic intercalations facies also show easily the attitude of beds, it does less clearly than calcareous but better than metamudstones facies and is quite similar to Precambrian paragneisses. Igneous intrusions are very easy to identify by the rounded geoforms. With respect to paragneisses, those show the softest expression with a more flattened relief and rounded hills, as can be seen to the north outcrops of La Cristalina Formation (Figure 2).

1.3.2 Stratotype Because there is no a single creek-section that include the whole known succession, La Cristalina Formation stratotype is composed. La Miquera (together with one tributary to the north which reach the contact with Precambrian paragneisses) and Las Iglesias creeks are the composed stratotype because 4 main reasons: 1) fossils occurrences are found there (La Miquera Creek); 2) there crop out the main facies of which is it thought is composed La Cristalina Formation; 3) accessibility, and 4) fresh rock outcrops.

Figure shows the Geological Map of La Critalina Formation, showing the facies and facies association distribution at 1:100 000 scale, it also includes structural data, critical faults and some key lineations; Figure 3 shows the creek sections in La Miquera and Las Iglesias creeks, at the composed stratotype; Figure 4 shows the cross-section of La Miquera Creek and tributaries, as well as in Las Iglesias Creek, and Figure 5 shows the composite stratigraphic columns of the 4 different facies of La Cristalina Formation. Those figures 2-5 represent the stratigraphic concept of La Cristalina Formation. 40 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Figure 1-2. Geological Map of La Cristalina Formation showing facies and facies association distribution at 1:100 000 scale, including digitalized structural data of Feininger et al. (1970). Geological interpretation using mainly field work, shaded relief images (USGS, 2004) and photogeology. Map modified from Gómez et al. (2015) after Feininger et al. (1970).

1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 41

Figure 1-3 Creek-sections in Las Iglesias and La Miquera creeks and some tributaries of both. Field information was controlled with photogeology and shaded relief images (cf. Supplemental Material 1). 42 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Figure 1-4 Cross-sections in Las Iglesias and La Miquera creeks and some tributaries of both. For locations of cross-sections cf. Figure 1-3. a) Cross-section in one tributary of La Miquera Creek, showing a faulted contact between Precambrian and Ordovician rocks (cf. Supplemental Material 4); b) Cross-section in one tributary of La Miquera Creek; c) cross-section in La Miquera Creek; d) continuation of the c) cross-section in La Miquera Creek, and e) cross section in Las Iglesias Creek. The legend can be seen in Figure 1-3. 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 43

Figure 1-5 Composed generalized columns of La Cristalina Formation, that represent the stratigraphic concept of La Cristalina Formation. a) Column using information obtained in La Miquera Creek and some tributaries; b) column using information from La Miquera Creek; c) column using information from Las Iglesias Creek, and d) column using information from Las Iglesias Creek and some tributaries.

1.3.3 Facies description Following the Guide´s recommendations of the ICS (Salvador, 2013), rocks are described as sedimentary, rather than metamorphic. In the same way, the Code in the Article 22 recommends to consider as lithostratigraphic units metasedimentary rocks in which the primary (sedimentary) characteristics are recognizable.

La Cristalina Formation facies and facies associations will be described, fulfilling the recommendations of the chapters 3-5 of the Guide (Salvador, 2013) and the articles 1- 3,5-15, 22-24 and 30 of the Code (NASC, 2005). According to the Guide, rocks are 44 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) described as sedimentary, rather than metamorphic (litodemic). Likewise, following the Article 22 of the Code the succession is described as lithostratigraphic unit composed of metasedimentary rocks in which the primary (sedimentary) characteristics are recognizable.

4 facies and facies association were identified (cf. Figure 2), grouped in successions of siliciclastic and calcareous rocks. It should be noted that siliciclastic and calcareous rocks are mappeable at 1:100 000 scale (e.g. Feininger et al., 1970, GRP, 2008), the official scale practiced in the region; in addition, those 2 different successions are easy to identify, calcareous rocks outcrop mainly in Las Iglesias Creek and La Argentina and related tributaries, whereas siliciclastic facies can be seen in La Miquera Creek and tributaries.

Furthermore, it is pointed out that the sedimentological structures observed in field always suggest that beds are normal, and in such way the calcareous successions overlies the siliciclastic successions.

In adittion to geomorphologic, outcrop, hand-sample and thin section descriptions, minerals identifications were improved by using X Ray Diffraction (Supplemental Material 3), which allowed to confirm the metamorphic character of the hole La Cristalina Succession.

Siliciclastic successions

Siliciclastis successions are composed of metamudstones facies and siliciclastic intercalations. A lineament put into contact metamudstones facies and siliciclastic intercalations facies thorugh of La Miquera Creek and one tributary (Supplemental Material 1, Figure 2) and crosses by the intersection of both (Figure 4). In adittion both facies have different attitudes despite the proximity, therefore it is thought the contact between both facies is faulted, in such way metamudstones are thrusted on siliciclastic intercalations. Table 3 shows petrographic descriptions of selected samples of metamudstones facies and siliciclastic intercaltions facies association, although in the Supplemental Material 2 can be seen the sample descriptions at thin-section. 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 45

Metamudstones facies: crop out in the north and consists of dark grey metamudstones with minor sandy and silty dark grey metamudstones, besides 3 massive metasandstones of m-sized layers were observed, including one belonging to a regressive sequence 10 m thick coarsening upward, varying from metamudstones, metamudstones and fine grained metasandstones intercalations up to coarse metasandstones. Figure 1-6 shows the genuine outcrops and hand-samples, whereas Figure 1-7 shows thin-section pictures and Table 1-3 the petrpgraphical observations of selected samples.

The contact between the metamudstones facies and the overlying siliciclastic intercalations facies association is a lineament (figures 2-3). Besides both facies have different attitudes despite the proximity in the northern outcrops, therefore it is thought the contact between both facies maybe faulted. The contact with underlying Precambrian paragneisses is a faulted unconformity to the northeast (see further discussions and Figure 3). In contrast, to the north, the metamudstones developed a better the schistocity (forming phyllites) with penetrability (with linear objects, figures 6f and 7c,d) and is missing a metasandstones bed, thus a minor fault is suggested.

At outcrop-scale, metamudstones facies consists of characteristic not well-developed layers of < 1 cm (Figure 6a); however, when minor very fine silt or fine-sand sized laminae are present some well-formed layers can be observed (Figure 6c), typically <5 cm continuous and plane-parallel to slightly wavy. The sequence is faulted and folded thus the thickness must be lesser than ca. 1500 m (cf. figures 3 to the northeast).

At hand-sample scale, rocks have a poorly developed schistosity and fine foliation of <1 mm, with abundant pyrite indicating highly reductive conditions (Figure 6d). As well, sedimentary pyrite might be due to originally high organic matter. Other pyrite crystals are due to igneous intrusions associated with fractures and veins. On the other hand, in at least 8 localities we found graptolites, one of them with phyllocarids (Almanza et al. 2016). This assemblage is typical of offshore settings (Goldman et al., 2013; Cooper et al., 2012).

There are 3 beds and set of beds of light grey, coarse- to medium-grained metasandstones. The stratigraphycally lowest is near to the contact with Precambrian paragneisses (Figure 3). Other metasandstones has 1 m of thickness is massive (structure-less), well-sorted, fine-grained, and very friable with ichnofossils and 46 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) undetermined fossils (Figure 6e). Finally, the uppermost set of metasandstones belong to a sequence of ca. 10 m (Figure 6b), which shows normal polarity criteria. The set of beds can be seen at figures 6a-b and correspond to a coarsening upward sequence, from mm- intercalations of metamudstones with fine-grained metasandstones up to coarse-grained structure-less. This sequence is strongly useful for correlation purposes, as was here used to solce structural issues.

At thin-section, metamudstones are very fine-grained (<1 mm), poorly laminated with very thin wavy laminae of organic matter, other laminae are richer in white mica (biotite was not identified petrographically) and other laminae, in coarser quartz and feldspar. Matrix minerals are composed mainly of white mica, organic matter and pyrite. As framework minerales, minor silt-grained quartz and feldspar, more or less in the same proportion. Deformation microstructures include undulant extinction, kink bands and quartz-veins formation, in addition to undulant extinction in muscovite and feldspar. Those microstructures are indicative of low-grade deformation, coherent with low-grade metamorphism. Evidences of grain boundary migration mechanism, inclusions alignment, deformation lamellae formation and chess-board textures in quartz are suggested as inherited from the provenance rocks. 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 47

Figure 1-6 Outcrops and hand-samples of metamudstones facies. a) Genuine outcrops showing not well- developed layering of metamudstones (slates); b) coarsening upward sequence, to the base cm-sized intercalations of metamudstones and fine metasandstones and, to the top, coarse grained metaquartzsandstones; c) metamudstones with higher silt or sand content, showing better formation of layers; d) hand-sample showing pyritic bioturbation on the foliation planes; e) strongly bioturbed metasandstones and undetermined fossils in metasandstones; f) hand-sample of metamudstones showing penetrability and better development of schistosity (phyllites). 48 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Figure 1-7 Thin-section pictures of dark metamudstones facies in plane-parallel Nichols (to left) and cross polarized (to the right). a-b) Metamudstones with mainly white mica and minor quartz and feldspars silt-sized in similar proportions; d-e) transversal cut of rocks with penetrability showing object lineation (cf. Passchier & Trown, 2005) of mainly quartz and coarser recrystallized muscovite, and e-f) well-sorted coarse metaquartzsandstones, quartz with bulging re-crystallization (cf. Passchier & Trown, 2005). 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 49

Table 1-3 Selected thin-section descriptions of both of metamudstones facies and intercalations facies association of La Cristalina Formation. Mineral abbreviations following Fettes & Desmons (2007).

Metamudstones near to fault zones developed object lineation composed of coarser grains of quartz and re-crystallized muscovite. Figure 7c-d show a transversal cut of those structures. As well, some samples show development of cleavage and minor poorly development of crenulation cleavage.

On the other hand, in thin-section, metasandstones are structure-less. Framework minerals constitute more 90% of volume of the rock and consist of quartz, feldspar and metamorphic lithics with abundant iron oxides and hydroxides. Minor white mica without biotite is the main matrix mineral. Strongly fractured quartz and bulging recrystallization mechanism (Passchier & Trown, 2005) suggest very low deformation grade, coherent either with metamorphism or later deformational events. 50 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Near to igneous intrussions, the metamudstones show contact metamorphism, bearing coarser white mica and minor andalusite porphyroblasts (also observed by Fonseca et al., 2011), as well re-crystallized micas with different orientation than foliation.

Finally, the metamudstones together with metamicrites facies may represent the deepest depositational settings of La Cristalina Formation, according to the lithologic facies association and fossil assemblages (cf. Cooper et al., 2011).

Siliciclastic intercalations facies association: occupies the largest area of La Cristalina Formation outcrops (Figure 2). It has a buried but concordant contact with the overlying metamicrites facies (figures 3-4) in Las Iglesias Creek. A thickness of ca. 500 m has been estimated for this facies, but with structural complications (abundant folds and inferred faults cf. Figure 4 B-B’ cross-section), thus is thought the thickness should be less. In the type section, rocks dips gently, except next to a strike slip-fault with Precambrian paragneisses to the west (Figure 3), where dips are higher and outcrops are the most deformed including crenulation, better development of schistosity and formation of up to cm-sized pyrite cubes (Figure 8g).

This facies association includes cm-sized intercalations of dark grey metamudstones and fine-grained lighter grey metasandstones (Figure 8a), together with dark grey mm-sized intercalations of metamudstones, silty and sandy metamudstones, and minor metasiltstones and metasandstones (Figure 8d).

At outcrop scale (Figure 8a-f), the succession dips gently, and characteristically forms anticlinals and synclinals (figures 4 B-B’ and 8b), with minor accommodation faults. Beds have tabular strata, strongly bioturbated (Figure 8c), with many normal polarity criteria (e.g. Figure 8f). cm-sized intercalations can be differentiated easily by changes in colour (light pinky grey and dark grey, the former caused by red biotite), some layers are mud- rich and other are enriched in very fine to fine sand and coarse silt size grains (Figure 8c- f). This is the clearest way to identify this facies in field, together with the well-developed strata.cm-sized intercalations have minor mm-sized lens, cross-lamination, and other critical structures shown at Figure 8c.

3 metasandstones beds and set of beds have been observed (Figure 8e and f). To the top of this facies association one structure-less of considerable thickness, of m-scale, with 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 51 minor metasiltstones intercalations of cm-scale, this can can be observed in figures 5b and 8f. These beds and set of beds are very useful for correlación porpuses. 52 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 53

Figure 1-8 Outcrop and hand-sample pictures of silicilastic intercalations facies association. a) Genuine outcrop of siliciclastic cm-sized intercalations of metamudstones and fine metasandstones, in La Miquera Creek. A reddish yellow bed is shown, likely related with bentonites; b) anticlinal in La Miquera Creek, with minor faults that accommodate the deformation; c) genuine bioturbated siliciclastic intercalations, lighter layers are enriched in sand-sized framework minerals (quartz and feldspar) those layers are pinky coloured because biotites, whereas darker layers are enriched in organic matter and micas; d) mm-intercalations siliciclastic of metamudstones with variations to minor silty and fine grained sandy metamudstones, without changes in colour; e) metasandstones in La Miquera Creek to the top of the measured sequence, correspond to the coarsest beds, mainly structure-less; f) meetasandstones bed showing a possible erosive base; g) strongly deformed intercalations to the west and near to the faulted contact between siliciclastic intercalations and paragneisses, and h) some fine grained and well sorted metasandstones associated to the highly deformed siliciclastic intercalations showed in g), next to the faulted contact with paragneisses.

At hand-sample scale, all samples have very poorly developed schistosity and gneissosity, and are fine to very fine-grained. Both the mm-sized and cm-sized intercalations are strongly bioturbated. Bioturbation is perpendicular to subperpendicular to lamination and foliation. Structures at hand-sample include lens, cross-lamination, cross-lamination in opposite direction and major plane to wavy-parallel continuous lamination.

At thin-section scale (Figure 9a-h), many structures have been observed in the cm-sized intercalations including cross-lamination and lens, and in one sample cross-lamination in opposite directions, all bioturbated. Laminae are differentitate by some framework- enriched layers and others enriched in white micas, biotite and organic matter. Lamination varies from parallel to minor no-parallel, continuous and discontinuous, most wavy and minor plane. Grain size is mainly silt up to medium sand, well sorted. Microfaults have been observed in the folded outcrops, filled with abundant chlorite. On the other hand, mm-sized intercalations have minor discontinuous slightly wavy to parallel lamination of <20 μm of thickness, one kind of laminae mainly composed of organic matter. Also, samples have minor subperpendicular quartz veins typically of <100 μm of thickness. But what is more evident, is that rocks are strongly bioturbated which, frequently, destroys completely the original sedimentary structures. Bioturbated areas are enriched in framework minerals, mainly coarser quartz and feldspar, typically of very fine sand, which gives the pinky colour to rocks. 54 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 55

Figure 1-9 Thin-section pictures of siliciclastic intercalations facies in plane-parallel Nichols (to left) and cross polarized (to the right). a-b) Metasiltstones with Chl-Wm in addition to quartz, feldspar and organic matter; this sample has organic matter and white mica laminae, with predominant layers composed by quartz and feldspar coarse silt-sized (85% modal); c-d) metamudstone with Mu-Bt in addition to quartz, feldspar and organic matter; it is shown laminae enriched in biotite and white mica, in comparison with other enriched in quartz and feldspar medium silt-sized; e-f) subarcosic metamudstone with Bt-Wm in addition to quartz, feldspar and organic matter; sample shows microcrenulation with incipient development of crenulation cleavage, and g-h) subarcosic metamudstone with Mu-Chl-Bt and many laminae enriched in coarse silt grains; picture shows microfaults in the intercalations, lighter layers are identified by coarser quartz and feldspar enrichments, in comparison with mica rich layers

Beds are mainly parallel to the foliation in most of the cases, but in some localities an inclined relation was observed. Deformation microstructures are undulant extinction, kink bands and veins formation in quartz; undulant extinction in muscovite, and undulant extinction, strong undulant extinction and twins formation in feldspar. Those microstructures are indicative of low-grade deformation, coherent with low grade metamorphism. Evidences of grain boundary migration mechanism, inclusions alignment, deformation lamellae formation, strong undulant extinction and chess-board textures in quartz are thought as inherited from the provenance rocks.

Finally, we suggest that this facies have a shallower depositational setting in comparison with metamudstones and metamicrites facies, when considering facies associations, fossils and type of bioturbation. On the other hand, this facies association has higher volume of biotite (around 30-40 %) in comparison with the others (<10 %).

Calcareous successions

Calcareous successions are composed of metamicrites facies and calcareous intercalations facies association. It seems coherent that both successions are genetically related. Table 4 shows the petrographical observations of the both facies.

Metamicrites facies: Consist of fine foliated dark grey metamicrites. A thickness of ca. 700 m has been calculated for metamicrites facies at Las Iglesias Creek locality, but structural complications might be present, when considering the high structural attitudes, these beds have the highest dips of all successions observed in La Cristalina Formation, even with overturned beds. It should be due to close proximity to the faulted contact with the paragneisses to the west (Figure 3). It is thought the metamicrites are stratigraphically below the calcareous intercalations when consider the close outcrops and similar attitudes, and because metamicrites are concordant with siliciclastic intercalations facies 56 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) association, nevertheless the contact have not been observed yet (figure 2-3). On the other hand, Feininger et al. (1972) suggested the calcareous rocks correspond to lenses, but we found continuous layers in field, which do not support that idea.

At outcrop scale, layers have typically <5 cm of thickness, are continuous, parallel and less commounly crenulated because deformation (Figure 10a). This facies consists of monotonous metamicrites, although one 8 m bed of green metamudstones with no calcareous content was observed, in one tributary of Las Iglesias Creek (Figure 3 to the west). It is recommended to use this bed for correlation porpuses and as tools to improve structural issues.

At hand sample scale, rocks are dark grey, have very poorly developed schistosity and are very fine-grained. Laminae are typically <1cm. Many samples have stylolites and carbonate veins, both parallel and subperpendicular to foliation.

In thin section (Figure 11) rocks matrix consists of recrystallized carbonates (15-50 µm) with slightly coarser white mica and chlorite in a lesser extent. Framework minerals consist of typically coarse silt-sized quartz and minor feldspar. This suggests that the rocks protolite were micrites instead of sparites. Samples show very fine organic matter- rich laminae, continuous to discontinuous, but parallel and plane to wavy. One sample has <1 % of metamorphic lithics and tourmaline (<1 %). 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 57

Figure 1-10 Outcrop and hand-sample pictures of metamicrites facies. a) Outcrop showing crenulated foliation, those beds have been inverted; b) typical foliation; c) dissolution of metamicrites, d) quartzitic green metamudstones; e) stalagmites formation in one bed-plane, very close to there also was observed a sinking stream, and f) hand-samples showing the dark grey colours and frequent carbonate veins formation parallel and subperpendidicular to the foliation, as well as some stylolites. 58 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Figure 1-11 Thin-section pictures of metamicrites facies in plane parallel Nichols (to left) and cross-polirized (to right). a) Metamicrite with white mica, showing quartz grains and opaque mineral not oriented with foliation, all in a matrix of re-crystallized carbonate; b) metamicrite with white mica bearing metamorphic lithics, showing some not oriented with foliation octahedral opaque minerals, and c) metamicrite with white mica and Fe oxides and hydroxides. Mineral abbreviations following Fettes & Desmons (2007). 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 59

Table 1-4 Selected thin-section descriptions of metamicrites facies and calcareous intercalations facies association of La Cristalina Formation. Mineral abbreviations following Fettes & Desmons (2007)

Deformation microstructures are undulant extinction, kink bands and minor fractured grains in quartz; undulant extinction in white mica, as well as veins, stylolites, twins formation and bent twins in carbonates which are indicative of low-grade deformation, coherent with low grade metamorphism. Evidences of grain boundary migration mechanism (Passchier & Trown, 2005) are suggested as inherited from the provenance rocks. In addition, Fonseca et al. (2011) found diopside and epidote in some calcareous metamorphic rocks, either metamicrites or calcareous intercalations can be related to that local mineral assemblage. Those isogrades seem of great interest for metamorphic petrogenesis.

Calcareous intercalations facies association: Consist of intercalations of metamicrites, metawackstones, calcareous metasandstones and minor metamudstones. The succession typically dips gently in the type section. Calcareous intercalations seems to have an either faulted or discordant contact with overlying felsic to intermediate “Volcanic Rocks” (petrographically classified as andesites and rhyolites by us) (sensu Feininger et al., 1970) and are Middle Jurassic in age (González et al,. 2015). Here it is said “either” because the contact is buried, but according to the structural data and observed stria it 60 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) should be faulted, which is also supported by Feininger et al. (1972). The calculated thickness for calcareous intercalations is ca. 1000 m, but stria observed in field and lineaments (Figure 2) demostrate the sequence is affected by structural complications.

At outcrop scale, beds are plane to wavy, parallel, continuous of cm- to m-scale in thickness as shown in Figure 13d. Metawackstones have beds typically of 1 m (Figure 12d), but also less commonly as finer as 5 cm. It is proposed that fine grained rocks correspond to metamicrites because the fine re-cristalyzed carbonate minerals. Metamicrites have thicker beds (ca. meters) with parallel continuous beds, but with irregular upper boundaries with metawackstones (Figure 13b). Lastly, metamudstones (Figure 12c) are the least commoun; those are dark grey with fine foliation. In field and at thin sections we looked for fossil, but we did not found any. Lastly, clasts of calcareous pebbles conglomerates have been found (Figure 12e), but unfortunately those could not be found in situ. 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 61

62 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Figure 1-12 Outcrop and hand-sample pictures of calcareous intercalations facies association. a) Grey fine sand-grained metawackstones, a hand-sample is to the upper right showing discontinuous parallel and slightly undulate lamination; b) intercalations of grey fine sand-grained metawackstones showing a wormy- texture with light grey metamicrites to the upper side; c) intercalations of grey fine sand-grained metawackstones and light grey metamicrites to the base, it should be noted the base of the metawackstones showing the normal polarity of beds; d) the same intercalations showed in b), note the strong contrast in colour, as well note the green and red alteration minerals; e) intercalations of calcareous metasandstones (1 m) and metamudstones; f) other locality of the metamudstones and calcareous metasandstones intercalations; g) clasts of the calcareous metaconglomerates of pebbles, with very well rounded clast, and h) a boulder of metamicrites with plane-parallel discontinuous lamination, showing green and pinky colours, and minor light grey layer of coarser grains.

In hand-sample, metawackstones and calcareous metasandstones have a very poorly developed gneissose textures, fine grained. In contrast, marbles have both poorly developed gneissose textures fine grained and granofelsic textures medium grain-sized. Metawackstones and calcareous metasandstones are medium grey with discontinuous wavy lamination enriched in dark minerals such as organic matter and pyrite. The lighter laminae are mainly enriched in carbonates and quartz. Weathering makes metawackstones and calcareous metasandstones to have a characteristic wormy-surface (Figure 12a), in comparison with the more planar surfaces of metamicrites (figures 12b-d). On the other hand, metamicrites are medium grey, light grey with minor greenish and pinky colours observed in strong re-crystalized samples. Metamicrites have very fine laminae, plane to slightly wavy, parallel, discontinuous and enriched in dark minerals (organic matter and opaque minerals). Metamudstones are dark grey and have some minor discontinuous lighter green laminae enriched in coarser quartz. Green colour is due to chlorite.

At thin section, metawackstones have framework grains of quartz, feldspar and minor lithics of metamorphic and volcanic rocks, fine and medium sand-sized. Matrix minerals correspond to re-crystallized carbonate grains, always smaller than framework minerals, with minor chlorite and white mica. Metawackstones and calcareous metasandstones have darker plane-parallel to slightly wavy and continuous laminae, and others no parallel, wavy and discontinuous, both enriched in organic matter and opaque minerals. Some euhedral opaque minerals are not oriented; therefore those can be introduced or late re-crystallized (porphyroblasts). On the other hand, metamicrites have a fine lamination, wavy to plane parallel, discontinuous and enriched in opaque and organic matter. Metamicrites have very little proportion of framework minerals, mainly silty-sized quartz. Matrix consists of fine grained carbonates (150 µm) and minor white mica. Very light grey marbles with granofelsic textures show strongly re-crystallized carbonates about 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 63

1000 µm sized, but the framework minerals (quartz, feldspar) are silt-sized which is indicative that the contact metamorphism affected mainly carbonates (Figure 13e-f).

Deformation microstructures such as undulant extinction, kink bands and minor fractured grains in quartz, as well as veins formation, twins formation and bent twins in carbonate are indicative of low-grade deformation, coherent low grade metamorphism. 64 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Figure 1-13 Thin-section pictures of calcareous intercalations facies association in plane-paralel Nichols (to left) and cross polarized (to right). a-b) Sandy and lithic metawackstone with the mineral assemblage Cb-Wm- Chl-Ep, at the center a metamorphic lithic of polycrystalline quartz with higher grade deformation in comparison with La Cristalina metamorphism, framework minerals medium sand-sized; c-d) calcareous metasandstone with Cb-Chl-Wm, with fine-sand framework minerals, and e-f) strongly re-crystallized marbles of 1 mm-grains with granofelsic textures in hand sample. Cb:carbonate, Wm: white mica, Chl: chlorite, Ep: epidote. Mineral abbreviations following Fettes & Desmons (2007). 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 65

1.4 Discussion

In the following there will be discussed invalid definitions, type locality, position and stratigraphic relations, lithologic description, depositional setting, age, lithocorrelation, rank and name. In addition to those characteristics not fundamental to define the unit, but of interest for readers.

1.4.1 Invalid definitions

At geological maps memories, such as those of Fuquen et al., (2009) and Fonseca et al. (2011) stratotypes were suggested using an unrepresentative part of the succession traditionally considered as La Cristalina Formation (e.g. Botero, 1940 or Feininger et al. 1972) and without following the international procedure, but very useful and complementary with this definition.

1.4.2 Composed type locality

The type locality is composed and includes outcrops in the whole Las Iglesias and La Miquera creeks, as well as some tributaries of the later that go to the north up the Precambrian paragneisses. There can be observed all the contacts of La Cristalina Formation. See further information at the introduction, such as accessibility, means of transport, etc. The above fulfils the recommendations of the sections 4, 3.B.1 and 5.D.1 of the Guide (Salvador, 2013).

It is highlighted the structural complications of the type locality here proposed, which is a clear disadvantage, but is characteristic of La Cristalina Formation outcrops. Hopefuly future sub-surface (wells, high resolution seismic, etc.) could help to illustrate the contacts diversity and serve as reference sections.

1.4.3 Stratigraphic relations

A summary of the stratigraphic relations of La Cristalina Formation can be seen at Table 5, stratigraphic relations will be discussed below. Figure 14 shows some the critical contacts observed in field. 66 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Table 1-5 Stratigraphic relations (nature of contacts) of La Cristalina Formation with adjacent units

1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 67

68 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Figure 1-14 Stratigraphic relations (nature of contacts) of La Cristalina Formation with adjacent units. a-c) Intrusive contact with the Middle to Upper Jurassic gradioritic to dioritics rocks (“d” unit of the “Igneous rocks mainly to the east of the Otú Fault” sensu Feininger et al., 1970), cropping out in Las Iglesias and La Miquera creeks (cf. Chapter 4); d) intrusive contact with the granitoids, in La Miquera Creek (cf. Chapter 4); e) intrusive contact with rhyodacitic porphyries (“Felsic porphyries to the east of the Otú Fault” sensu Feininger et al. (1970), cf. chapter 4); f) unconformity with some Cenozoic alluvial deposits, in the road La Cristalina- Sabaletas railway stations, and g) outcrop of rhyolites and andesites (“Volcanic Rocks” of the "Felsic rocks to East of the Otú Fault" sensu Feininger et al., 1970) in Las Iglesias Creek, up-stream a buried contact with calcareous intercalations facies association, it should be either an unconformable or a faulted contact, according to observed lineaments (Supplemental Material 1, Figure 2).

La Cristalina Formation has a very contrasting lithological contacts and stratigraphic positions (time differences) with adjacent units, in coherence with the recommendations of the Code (Article 23).

La Cristalina Formation rests unconformably on Precambrian paragneisses according to observations of Feininger et al. (1972), author said the contact “can be seen clearly in some tributaries of La Miquera Creek”. Fonseca et al. (2011) observed an unconformity, but also a faulted contact, but no pictures have shown. During field work, we looked for contacts in La Miquera Creek and many tributaries, according to that mentioned by Feininger et al. (1972), but the majority of contacts are buried along creeks. Field observations suggest that everything is indicative of a faulted contact: better development of schistosity (phyllites) and penetrability next to the contact (Figure 6g) in addition to higher dips (Figure 2). Likely, we observed a faulted contact, but we do not have enough criteria to identify paragneisses undoubtedly (Supplemental Material 4). Nevertheless, to the NE due to the similar orientation of the Precambrian and Ordovician layers (Figure 3), the undeformed rocks and Feininger et al.´s observations the contact is most likely unconformable. It should be considered that recent deformation (eg. Paleocene cf. Chapter 4) could accommodate the deformation by faults through unconformity weak planes, thus originally would have been an unconformity, but today is faulted with very small displacements. To the west of La Cristalina Formation, the contact is undoubtedly a fault, very near to El Bagre and Palestina faults, according to the very strong deformation of La Cristalina Formation, clear geomorphologic lineaments and fault and horizontal stria observed (figure 2 and 6f-g).

Those Precambrian paragneisses have been studied in El Vapor River by Ordóñez et al. (1999). Other authors called those gneisses as “San Lucas Quartz-Feldspatic Gneisses” (cf. González, 2001; Fuquen et al., 2009), “San Lucas Gneiss” (cf. Clavijo et al., 2008), “San Lucas Metamorphic Complex” (Fonseca et al. 2011) or “Grenvillian rocks in the 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 69 eastern flank of the Central Cordillera” (e. g. Cardona et al. 2010). Here are called as “Precambrian paragneisses”, and is remarked that those studied gneisses of Ordóñez et al. (1999) undoubtfully correspond to the paragneisses underlying La Cristalina Formation, whereas the others remain uncertain, because crop out so far away, in addition to the unclear stratigraphical nomenclature.

Age determinations in Precambrian paragneisses in El Vapor River performed by Ordóñez et al. (1999) suggest 894 ± 36 Ma isochronic age by using Rb-Sr, authors considered the age as metamorphic. As well, authors showed TDM= 1829 and 1757 Ma. Despite the uncertainties of the method, this support the Precambrian age. On the other hand and recently, Cuadros et al. (2014) performed U-Pb LA-ICP-MS datings in San Lucas Ranges, which could be more meaningful, but measured rocks crop out further to the north, therefore correlations cannot be confident. Nevertheless, populations around 1400, 1200, 1100 and 900 Ma were reported with a metamorphism during Neoproterozoic, that opened a stratigraphic question about the relation of the here studied paragneisses and those gneisses in San Lucas (cf. Chapter 4).

Many igneous units intruded La Cristalina Formation (cf. chapter 4), those include at least the 1) granodioritic to dioritic rocks mapped as “d” unit sensu Feininger et al. (1970) or very likely genetically related with the Segovia Batholith (cf. Chapter 4), 2) porphyries grouped as “Felsic porphyries to the east of the Otú Fault” sensu Feininger et al. (1970) and 3) granitoids cf. Chapter 4. Only the Middle to Upper Jurassic Segovia Batholith and the Paleocene granitoids have been dated geochronologically, therefore their ages are well-constrained.

Rhyolites and andesites mapped as “Volcanic Rocks” and grouped as “Felsic rocks to the east of the Otú fault” by Feininger et al. (1970) or “La Malena Volcanic Set” sensu González (2001) have a Middle Jurassic concordant age (González et al., 2015). That is also supported by field observations of Feininger et al. (1972), González (2001) and by us, as the granodioritic to dioritic rocks included some xenoliths ans is cut of the rhyolites and andesites. On the other hand, Feininger et al. (1970) mapped an inferred faulted contact to east between La Cristalina and the “Volcanic Rocks”, Fonseca et al. (2011) suggested, apparently, a faulted contact. I suggest either an unconformable or a faulted contact between the calcareous intercalations facies of La Cristalina Formation and some 70 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) rhyolites and andesites (Figure 14g), up-stream of the first outcrops worked in Las Iglesias (Figure 3) the buried contact with calcareous successions can be observed. It is remarkable lineaments between both units in the Supplemental Material 1.

Overlaying La Cristalina Formation are 1) Lower Cretaceous marine strata (Fuquen et al., 2009), 2) doubtfully, not deformed the Mesa Formation? with an unconformity (Fuquen et al., 2009) and 3) Neogene alluvial deposits with and unconformity (Figure 14f). A discordant contact between La Cristalina Formation and the overlying Aptian to Albian strata bearing ammonites, pelecipods, gastropoda and plants was suggested by Fuquen et al., (2009) in the road Puerto Berrío-Puerto Serviez and called as “Segovia Sedimentites to the East of the Otú Fault”. The same authors observed that La Cristalina Formation rests below very thick conglomeratic sandstones matrix supported and polymictic, likely, related with the Mesa Formation? As wll, I observed an unconformable contact with alluvial Cenozoic deposits.

1.4.4 Age

According to the stratigraphic relations, La Cristalina Formation depositional age should be considered as post-Neoproterozoic (cf. Ordoñez et al., 1991) and pre-Middle to Upper Jurassic (e. g. Feininger et al. 1972; Leal-Mejía, 2003). Nevertheless, the most precise age is assigned to the siliciclastic successions by the graptolite fossil association, as Floian to middle Darriwillian (cf. Table 1 and Chapter 2). The calcareous succession age is unknown, but here is suggested strictly it should be post-Darriwillian and pre-Middle to Upper Jurassic, unlikely Silurian or Permian. On the other hand, the metamorphic age should be considered as post-Darriwillian and pre-Middle to Upper-Jurassic.

1.4.5 Rocks description and petrogenesis

At the Results section can be checked out the succession description and further information, such composed columns representative of the stratigraphic concept of La Cristalina Formation. That description should be used as the main criteria to recognize, to extend and to correlate the unit.

In a broad sense, La Cristalina Formation can be described from the sedimentological and metamorphic point of view, because preserves the sedimentary characteristics 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 71

(composition, textures, structures) despite the low-grade metamorphism. This study is the most complete description (in terms of area and facies description) done up to now of La Cristalina Formation, that together with that of Feininger et al. (1972) represent the best knowledge we have about the unit.

The total sequence cannot be determined yet, because it is critical to control the area with a higher density of data, when considering the many faults, folds and in general rock- deformation that affected the unit. Nevertheless, here is proposed that the basal sequence includes the metamudstones facies that represents a Lower-Middle Ordovician transgression. The siliciclastic intercalations overlies the metamudstones facies, but in field a fault is suggested. Furthermore, it was observed a concordant contact between the siliciclastic successions and the calcareous successions. I pointed out that the 2 calcareous facies described here are also concordant in between. Therefore the calcareous successions are to the top of La Cristalina Formation and siliciclastic to the base.

The age of calcareous successions is critical, because if they are Ordovician they could represent the regression to the end of the period that coincided with warmer climates before the glaciations (e.g. Haq & Shuter, 2008; Gutiérrez-Marco et al., 2011) and, unless, they represent somehow another processes such as the Gondwana continent migration to warmer latitudes, but before Jurassic. In addition although no disconformities have been observed, and paraconformities/hiatuses those cannot be discharged and significant amount of time could be absent in the rock record.

Finally, the total and accurate thickness of the succession has not been determined yet, because bed orientation and structures are too variable to consider stratigraphic simplicity, but it is calculated ca. 3600m, with clear structural issues.

Depositional setting

As was afore mentioned, despite there is no enough information to know the total succession, the deposition settings could have evolved in offshore and distal shoreface conditions (Nichols, 2000; Hampson & Storms 2003), as is indicated by the facies association and fossil association (Cooper et al., 2012). For the calcareous successions is suggested off-shore and shoreface conditions (Nichols, 2000 or distal shoreface 72 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) according Hampson & Storms 2003). Therefore, the base of La Cristalina Formation is a transgressive surface and, with minor confidence, the top represents the shallowest facies and a regression in comparison with the base. Many relative sea level changes can be observed when considering the columns showed in Figure 5, but these analyses are out of the scope of this text and requires further and detailed studies.

Deformation

La Cristalina Formation is a polymetamorphic unit. The most important one is that pre- Middle to Upper Jurassic regional metamorphism, likely due to burying and less likely orogenic metamorphism. Metamorphism is provisionally classified as green-schists facies, when consider the biotite isograde, which indicates the peak metamorphic conditions. Nevertheless, it has to be considered that in some localities just reached chlorite or white mica isograde, which will be indicative of lesser grade than biotite isograde, but here is suggested is due to to complex lithological changes that responds differently to the same metamorphic conditions.

La Cristalina Formation has local contact metamorphism caused by the many igneous intrusions, out of which granodioritic to dioritic rocks are the most important in terms of area and expected higher temperatures. Contact metamorphism is evidenced by re- crystallization of coarser and not oriented micas, porphyroblasts (andalusite), marbles with granofelsic textures, in addition to diopside and epidote observed by Fonseca et al. (2011).

Finally, local dislocation metamorphism affected La Cristalina Formation. From the structural point of view, many faults and indications of faults have been observed, especially strong are those in the proximity to Precambrian paragneisses to the west and northwest, which are coherent with photointerpretation lineaments. But neither significant movement indicators (such as shear zones) nor preferential deformation have been observed in the total succession, therefore deformation is due to local faults, which causes local very low-grade dislocation metamorphism. This deformation events could be partially related with the on-going uplift of the Central Cordillera since latest Cretaceous (Villlagómez et al. 2010) (cf. Chapter 4). 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 73

1.4.6 Lithocorrelation

El Hígado Formation, 460 km to the south in the Upper Magdalena Valley (Figure 1), was dated as Darriwilian according to graptolites, trilobites, conodonts and brachiopods occurrences (e.g. Borrero et al., 2007). El Hígado includes the graptolite assemblage Didymograptus murchisoni, D. aff. artus, Glyptograptus sp., Cryptograptus cf. tricornis and Hallograptus cf. bimucronatus (Mojica et al., 1987 and 1988). As well as, an association of conodonts (the first conodont occurrences of Colombia and the third of South America, Gutiérrez-Marco et al., 2007) Lenodus variabilis and Eoplacognathus suecicus that have an age equivalent to Expansograptus hirundo and Didymograptus artus biozones. Hence, at least part of La Cristalina and El Hígado are coetaneous and here is reinforced that were deposited in a common basin.

Therefore, it is clear that La Cristalina and El Hígado successions have the same stratigraphic position, similar lithology (both units have metamudstones bearing graptolites with minor sandstones) and can be partially lithocorrelated; but, on the other hand, it cannot be considered those are the same unit, until some issues can be cleared up. To consider they are the same unit it should better first examined: 1) the lithologic characteristics, 2) the stratigraphic position and 3) proving lateral continuity. Currently, conditions 1 and 2 are fulfilled partially, and 3 is not fulfilled (lacking of information about lateral continuity). Points are said 1 and 2 are partially fulfilled because stratigraphic relations with adjacent bodies are not completely clear in El Hígado Formation (e. g. the top is unknown or faulted) and due to deformation (faults, folds, no-parallel foliation to the stratification, etc.) makes both total successions have not determined accurately (suggestions for El Hígado Formation can be checked in Caicedo, 2001 and Gutiérrez- Marco et al., 2007). It seems there is a lot to do with the best studied Ordovician units of Colombia, up to now.

As far as deformation is concerned, La Cristalina Formation has a higher deformation, undoubtedly metamorphic, in comparison with El Hígado Formation, which actually seems to have advanced diagenesis (Borrero et al., 2007).

Lastly, as was concluded by Almanza et al. (2016), La Cristalina Formation has strong similarities with Peruvian and Bolivian fauna including similar rocks facies and, therefore, 74 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) can be considered reasonably that those were deposited on the western margin of Gondwana in interconnected Andean basin and can be potentially correlated.

1.4.7 Stratigraphic classification: Rank

Until no more studies are available, La Cristalina should be better accompanied by the term formation, mainly because 1) the term has been traditionally used (section 3.B.3.g of the Guide) and 2) fulfil all the recommendations suggested at the Guide, specially section 3.B. and sections 5.A, 5.C and 5.D. On the other hand, it should be considered as lithostratigraphic unit because is undoubtedly its usefulness in mapping, regional geologic understanding and because can be easily recognized by lithologic and geomorphologic characteristics, as well as stratigraphic position.

Why La Cristalina Formation should not be split

At first glance, it might suggested to split the calcareous and siliciclastic successions as 2 different formations, but here is proposed that is more useful not to split the unit considering: 1) usefulness in regional geologic understanding of the area (cf. section 5. A. “Nature of Lithostratigraphic Units” of the Guide) as no other Ordovician rocks crop out in the region, 2) the overspread and homogeneous low grade metamorphism and 3) tradition (section 3.b.3.g of the Guide), when considering the unit has been understood as composed of both concordant successions since Botero (1940) and Feininger et al. (1972). As well, the Article 6 of the Code suggest that is undesirable to split the unit without suitable arguments, and despite the approximation 3600 m of the thickness is not a valid criteria to divide the unit (Article 24, e).

In addition, unless a regional discordance (Article 22, e of the Code) or very different age can be proved between the siliciclastic and calcareous successions, here is suggested not to split the unit.

1.4.8 Name

La Cristalina should be named as La Cristalina Formation because 1) is a well-stablished name (section 3.B.3.g of the the Guide) and deserves preservation (Article 7 of the Code); 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 75

2) fulfil the requirements of section 3.B.3 and section 5.F of the Guide, and 3) priority (section 3.B.3.v).

Here is not recommended a composed name (geographic name+descriptive term+rank) because La Cristalina Formation is a well-stablished name and according to section 3.B.3.a and section 5.F.3 of the Guide which suggest is disadvantageous, in contrast to Article 6 of the Code.

In addition, the unit has at least 2 homonyms. To this respect, it should be pointed out that there are at least 2 map units called also La Cristalina the “Andesitic Porphyry of La Cristalina” in the Western Cordillera in El Cairo Town (Parra, 1984a,b) and “La Cristalina Complex” to the north of the Western Cordillera in the Urrao Town (González, 2002; González & Londoño, 2003). Nevertheless, those names are informal (authors did not followed the international procedure), were coined after the first time La Cristalina name was used to refer to the Ordovician rocks and are just occasionally used. Therefore, those homonyms should not be considered a reason to abandon the name La Cristalina Formation for the Ordovician rocks. On the other hand, La Cristalina could have one synonime as “La Cruz Sedimentites”, but is critical to confirm if those rocks follow the complete definition here proposed (González et al., 2015).

Considering the “Preservation of Traditional and Well-Stablished Names” of the Guide (section 3.B.3.g), it should be pointed out La Cristalina term was used to locate some graptolitic shales as early as 1929 by Harrison (1929); thus La Cristalina term refers to a locality. However, the first time La Cristalina was used to refer not a locality but accompanying a geological term was “La Cristalina fossil locality” in 1940, 77 years ago (Botero, 1940) and in 1945 was coined to name a lithostratigraphic unit! La Cristalina Formation (Alvarado et al., 1945).

Currently, La Cristalina is a name used for a railway station, a small village (vereda) and a creek (where La Cristalina rocks do not crop out!). Therefore, La Cristalina Formation proper name is due to a railway station rather than due to the small village or creek name.

La Cristalina lithostratigraphic unit has been long quoted in many documents since it was first-published (Harrison, 1929). Table 6 summarizes the most remarkable published terms used to refer to La Cristalina Formation since 1911. 76 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

As can be seen at Table 6 most of the authors have used the term La Cristalina plus different adjectives. In 1945 the term La Cristalina Formation was coined by Alvarado et al. (1945), apparently, by the first time. Nevertheless, as it was pointed out by Julivert (1968) Precambrian, Cambrian and Ordovician units had been used as lithostratigraphic terms without defining them; despite the undoubtedly usefulness. On the other hand, La Cristalina Formation term has been frequently used in informal (maps, internal reports, etc.) and formal publications; out of which, Mojica & Villaroel (1990) used for the first time the term in a peer-reviewed journal.

Table 1-6 Names used to refer to La Cristalina Formation since 1911 up to now.

All the aforementioned, supports that La Cristalina Formation term is the most suitable name for the formal stratigraphic unit.

1.4.9 Formalization

To correctly formalize the definition of La Cristalina Formation, publication in a “Recognized scientific medium” must be done, according to the section 3.B.4 of the Guide. This is being currently done, as was submitted to an international and Schimago- indexed journal.

1.5 Conclusions

Following the international procedure recommended by the International Commission on Stratigraphy (Salvador, 2013), the lithostratigraphic unit La Cristalina Formation was 1. Stratigraphic definition of the Lower to Middle Ordovician La Cristalina.. 77 defined here, although it was cleared up that the term La Cristalina Formation was first coined 72 years ago by Alvarado et al. (1945). La Cristalina Formation has a composed stratotype in La Miquera, Las Iglesias creeks, and some tributaries of those, where all contacts and the best outcrops and Ordovician fossils occurrences can be found. La Cristalina Formation was defined as those rocks outcropping to the southeast of Antioquia Department and concordant with Floian-early middle Darriwillian graptolitic metamudstones. La Cristalina Formation is a polymetamorphic, with the most important regional low-grade metamorphism. La Cristalina Formation has 4 facies, with clear structural issues that do not allow knowing the total thickness, accurately. Facies have been grouped in siliciclastic (metamudstones and siliciclastic intercalations) and calcareous successions (metamicrites and calcareous intercalations). The basal metamudstones were considered as the oldest facies and the calcareous intercalations may be the youngest., although it was pointed out that the age of calcareous successions is undetermined and critical. It was recommended that those characteristics together with the low-metamorphism should be used to extend or correlate the unit far from the type locality, and are useful enough to identify the unit in field. It was said La Cristalina Formation has an unconformable and faulted contact with underlying Precambrian gneisses in the composed stratotype, and is overlaid by rhyolites and andesites with either a faulted or an unconformity contact, as well is overlaid by Lower Cretaceous metamudstones (Fuquen et al., 2009) and alluvial Cenozoic deposits with unconformities. Rocks have been intruded granodioritic to dioritic rocks, Paleocene S-type granitoids, and some felsic to intermediate porphyries. It was suggested La Cristalina Formation can be correlated in Colombia with the graptolite-bearing mudstones of El Hígado Formation in the Upper Magdalena Valley and potentially correlated with San Juan and Contaya formations in Peru and Bolivia, which have a very similar fossil assemblages. Also it was proposed La Cristalina should have a formation-rank because it has been traditionally used and due to fulfil all the requirements. The name was coined because priority and because it is well-stablished, and because is more useful bearing in mind the early description of its facies (Botero, 1940) and homogeneous metamorphism. It was remarked that until no more studies are available, it is recommended not to be split. Finally, here was concluded that La Cristalina Formation is a very useful stratigraphic unit when considering the paleography of Gondwana, and the tectonic location and its deformation meaning for the understanding of the tectonic processes that have occurred since Ordovician times 78 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Acknowledgments

To the Academic Vice-Rectory (Honor Degree Scholarship) and the Welfare Science Faculty (partially financed an academic exchange to Johannes Gutenberg Universität) of the Universidad Nacional de Colombia, the Spanish Mineco (CGL 2012- 39471) of the CSIC and GmasLab (Bogotá) for financing this work. As well we are grateful with the today geologists Francisco Javier Muñoz, Luis Miguel Vélez, Andrés Felipe Alvarado, Ángel Verbel and Felipe Pastor for their valuable help during field works.

1.6 References

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Ulloa, C., Pérez, V.E., Baldis, B., 1982. Unidades litoestratiqraficas del Ordovicico de los Llanos orientales de Colombia. V Congreso Latinoamericano de Geología. Actas I, 109-120, Buenos Aires. Vernon, R. H. and Clarke, G. L., 2009. Principles of Metamorphic Petrology. 1st edition, 446 p, Cambridge University Press. Villagómez D., Spikings, R., Magna, T., Kammer, A., Winklerd, W., Beltrán, A. 2011. Geochronology, geochemistry and tectonic evolution of the Western and Central cordilleras of Colombia. Lithos, 125, 875–896. DOI: 10.1016/j.lithos.2011.05.003 Villagómez D. and Spikings, R., 2013. Thermochronology and tectonics of the Central and Western Cordilleras of Colombia: Early Cretaceous–Tertiary evolution of the Northern Andes. Lithos, 160–161, 228–249. DOI: 10.1016/j.lithos.2012.12.008 Villarroel, C., Macía, C., Brieva, J., 1997. Formación Venado, Nueva Unidad litoestratigráfica del Ordovícico Colombiano. Vinasco, C.j., Cordani, U.G., González, H., Weber, M. & Pelaez, C., 2006. Geochronological, isotopic, and geochemical data from Permo-Triassic granitic gneisses and granitoids of the Colombian Central Andes. Journal of South American Earth Sciences, 21: 355–371. doi:10.1016/j.jsames.2006.07.007

2. New graptolite fossil localities of La Cristalina Formation Abstract

La Cristalina Formation is a low grade metasedimentary unit that crops out in the eastern flank of the Central Cordillera of Colombia. La Cristalina includes epicontinental marine deposits that vary in offshore and shoreface. Previously, Floian to Dapingian graptolites were found to the east and southeast of La Cristalina Railway Station in Puerto Berrío (Antioquia). Fossils recorded here include the graptolite assemblage Didymograptus cf. murchisoni (Beck), Pseudamplexograptus latus (Bulman) and Glossograptus hincksii (Hopkinson), in adittion to phyllocarids remains. That assemblage suggests a middle Darriwillian age. Therefore, currently La Cristalina Formation can be considered Floian to middle Darriwilian in age, thus representing the late Lower to most of the Middle Ordovician. This is the best time-resolution La Cristalina Formation has ever had. Regarding the aforementioned, La Cristalina can be correlated with the coeval El Hígado Formation in Colombia, which occurs in the Upper Magdalena Valley. The middle Darriwilian graptolitic assemblage of La Cristalina and El Hígado formations are very similar to those reported in Perú and Bolivia, thus those Ordovician units were, likely, deposited in the today´s the western margin of Gondwana in interconnected basins.

2.1 Introduction

2.1.1 General approaches of La Cristalina Formation

La Cristalina Formation was the first Ordovician unit discovered in Colombia (Harrison, 1929), it is widely recognized for its Ordovician graptolite assemblage, and often cited in paleoreconstructions of South America (e.g. Aceñolaza, 1980; Mojica & Villaroel, 1990).

84 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

La Cristalina Formation is located in the Middle Magdalena Valley (MMV) in Puerto Berrío Town (Antioquia Department). It is the unique Ordovician published in the Central Cordillera, and together with El Hígado Formation are the westernmost outcrops in Colombia (Figure 1). The largest outcrops are in La Cristalina Village and to the south of the Antioquian Railway Station named also La Cristalina; but the best rock exposures can be found rather in creeks, such as La Miquera (Figure 2).

Figure 2-1. Ordovician sedimentary and low-grade metasedimentary rocks in Colombia. From north to south and west to east, outcrops in: 1) La Cristalina Formation (Floian-early middle Darriwilian) in the eastern flank of the Central Cordillera, 2) Negritos Formation in the Orinoquía. 3) Venado Formation in the Eastern Cordillera, 4) La Uribe in the Piedemonte Llanero Foothills, 5) “Series”/”Group” Güejar in La Macarena Ranges, 6) El Hígado Formation in the Upper Magdalena Valley and 7) Araracuara Ordovician rocks in the Amazonía. Many occurrences of Ordovician rocks in the Orinoquía are not showed here and are unpublished. Map modified from Gómez et al. (2015). 2. New graptolite fossil localities of La Cristalina Formation 85

Figure 2-2. Geological Map of La Cristalina Formation at 1:100 000 scale. Geological map modified from Gómez et al. (2015), after Feininger et al. (1970). Location map modified from Gómez & Almanza (2015). 86 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

La Cristalina unit extends over ca. 50 km2 (Figure 2) and consists of mainly metamudstones; intercalations of metamudstones and metasandstones, as minor metasandstones, in addition to metamicrities and calreous intercalations of metamircrites, metawackstones, calcareous metasandstones and not-calcareous dark metamudstones. According to the metamorphic mineral assemblage, the unit has green schist facies, caused by regional metamorphism. The succession (ca. 3600 m with clear structural issues) includes an epicontinental marine sequence that varies from shoreface to offshore (Almanza et al., 2013), it is intruded all along by igneous rocks (mainly plutonic granodioritic to dioritic rocks, felsic porphyries and S-type granitoids) that caused contact metamorphism locally

2.1.2 Ordovician sedimentary/low grade metasedimentary rocks in Colombia

High sea levels during the Early and Middle Ordovician (e. g. Haq and Shutter, 2008) are responsible of thick marine sedimentary sequences preserved all around the world. Successions to the west of Gondwana can be seen today in countries such as Venezuela, Colombia, Ecuador and few in Chile. The the best exposures, and major thicknesses and time-register in the NW of Argentina, Peru and Bolivia (e.g. Aceñolaza, 1980; Benedetto et al., 2007).

Ordovician sedimentary/metasedimentary units recorded and published in Colombia were dated mainly using fossils such as graptolites, trilobites, acritarchs and in a lesser extent conodonts, brachiopods and ichnofossils. Ordovician successions can be seen in the Figure 1.

Sedimentary occurrences to the east of the Andes include: serranía de La Macarena (e. g. Trumpy, 1944; Harrington and Kay, 1951; Mojica and Villarroel, 1990; Gutiérrez-Marco et al., 2006), Amazonía (Bogota, 1982; Thery et al., 1984), SW of Mitú Town (Mojica & Villarroel, 1990) and some petroleum wells occurrences in Orinoquía (e.g. La Heliera-1, Negritos-1, Trinidad-1 and Voragine-1. E. g. Baldis et al., 1984; Théry, 1985; Ulloa et al., 1982; Dueñas, 2001; Arminio et al., 2013). Interestingly, information from Moreno-López et al. (2015) allows figuring out the thick (thousands of meters) Orinoquian successions presumably assignable to the lower part of the Paleozoic, by means of seismic information. 2. New graptolite fossil localities of La Cristalina Formation 87

Andes Ranges occurrences were recorded in: El Hígado Formation (e. g. Mojica et al., 1987; Mojica and Villarroel, 1990; where the unique Ordovician Colombian conodonts were found by Gutiérrez-Marco et al., 2007) in the Upper Magdalena Valley (UMV); Venado Formation (e. g. Villarroel et al. 1997; Moreno-Sánchez et al., 2008b) in the Eastern Cordillera; to the north and southwest of La Uribe (e. g. Trumpy, 1944) in the eastern flank of the Eastern Cordillera, and in the Eastern flank of the Central Cordillera in La Cristalina Formation. La Cristalina is the northern most Ordovician.

Not enough well-constrained Ordovician rocks require better information, such as in the Perijá Ranges in Cesar and La Guajira departments (Tchantz et al., 1969), and Santa Teresa in Tolima Department (González, 2001). Lastly, in Aquitania (Antioquia Department) was suggested presumably Ordovician (Moreno-Sánchez et al., 2008a; González, 2001), but recently Giraldo et al. (2015) found Tithonian ammonites (Upper Jurassic) discarding Ordovician sedimentites to the west of local Palestina Fault, and thus Otú-Pericos Fault.

2.1.3 La Cristalina Formation in the eastern flank of the Central Cordillera

The Antioquia Railway was built in 1878-1929 (Cisneros, 2003) in the Central Cordillera, engineers dealt with a very dense tropical rain forest; but thanks to that and to the petroleum exploration in the area in 1927 D´Arcy Exploration Co. engineers, leaded by V. Böckh, found graptolites near to La Cristalina Railway Station. However, fossil occurrences were published only upto Harrison (1929). The fossil association suggested “Arenigian”, the first undoubtedly Ordovician rocks known in Colombia. Table 1 shows the main contributions to La Cristalina Formation knowledge.

Unfortunately up-to-now, no maps showing fossil-localities were published, except that hand-made of Botero (1940), but fossils were not found by us. As well, neither pictures nor schemas of graptolites are available, and just Botero and Díaz fossils are in the Colombian Geological Survey (National Geology Museum José Royo y Gómez). The other fossil occurrences were not found yet. 88 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Table 2-1 Main published contributions to La Cristalina Formation biostratigraphical knowledge

2.1.4 Ordovician transgression in Colombia

The lowest Ordovician Colombian rocks are Tremadocian (in some localities include the upper Cambrian) in the serranía de La Macarena; Orinoquía, and Floian in the Central Cordillera (La Cristalina Formation). In addition, evidences are in reworked Tremadocian to Floian/Dapingian conodonts found in the UMV (Gutiérrez-Marco et al., 2006) in the Eastern Cordillera. Most of the Colombian Ordovician rocks record the “Arenigian”, as well as most localities to the west of Gondwana (e.g. Aceñolaza, 1980). “Areginian” has been found in the Central Cordillera, Eastern Cordillera, Orinoquía and Amazonía (likely, including Mitú). Finally, the Darriwilian Stage has been just found in the Central Cordillera and in the UMV. The aforementioned cf. Figure 1. Up to now, no later Darriwilian rocks have been found. In the future, more studies will allow us to have a better dating and 2. New graptolite fossil localities of La Cristalina Formation 89 correlation with global sea levels, according to the updated International Chronostratigraphic Chart, but biostratigraphy and geochronological studies are critical.

2.1.5 La Cristalina biostratigraphy and age

In 2009 the International Commission on Stratigraphy completed the GSSP´s definition of the bases of all Ordovician stages, therefore nowadays fossils can be used to date precisely stages, as it was done for the first time for La Cristalina in this paper. Table 2 summarizes the biostratigraphic knowledge of La Cristalina, including fossil localities and the up-to-date age of La Cristalina Formation.

2.2 Methodology

6 field trips to La Cristalina in Puerto Berrío town (Antioquia) have been done, 109 hand- samples were collected and 64 thin-sections were made at GMAS S.A.S. and at the Universidad Nacional de Colombia (Bogotá).

Rocks description were done according to Fettes and Desmons (2007) and Folk (1980). Mineral abbreviations, metamorphic concepts and other terms (e.g. metamorphic grade, P/T relation, isograde, etc.) according to Fettes and Desmons (2007). Mineral association and temperature stability conditions approaches, according to Spears (1993), and Vernon and Clarke (2008).

Samples were prepared in the CSIC laboratories and in the Universidad Nacional de Colombia. Pictures were taken at GMAS S.A.S. photographic studio, with the camera Canon Sony a99, 55mm lent, ISO 100, f/16 and 1/5s and graptolites in the CSIC Laboratories.

2.3 Results

2.3.1 Metasedimentary succession bearing graptolites

La Cristalina Formation consists of fine-laminated metamudstones, intercalations of metamudstones and fine-grained metasandstones, besides minor and very fine to fine quarzitic metasandstones that grades to medium grain-size, in adittion to calcareous 90 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) successions. At least 3 igneous rocks have intruded La Cristalina, causing contact metamorphism. One corresponds to sills-like granitoids and, the other, diorites (Almanza et al. in preparation).

Biotite in metamudstones indicates the highest grade and suggests green schist facies at the metamorphic peak-conditions (Figure 3e-f), whereas metasandstones have a less indicative mineral association with white mica. Succession thickness cannot be determined yet, because deformation that includes belds (several anticlinal and synclinal), faults, etc.; but ca. 3600 m is calculated (cf. Chapter 1). Normal beds polarity has been determined; nevertheless, it seems possible to do it too by biostratigraphic means (that will allow to constrain the depositional rate), but only when the other fossil assemblages will be find, such as those Floian or Dapingian (e.g. Harrison, 1929 or De la Cruz, 1939). Finally, lithology, sedimentological structures and fossil assemblage indicate shoreface to offshore marine setting as was suggested by Almanza et al. (2013) (Hampson and Storms, 2003), out of which the deepest correspond to the black metamudstones where graptolite occurrences were found, as well this facies looks very similar to the facies where Botero (1940) and Botero & Díaz found their fossils.

It should be highlighted that the 250 m of altitude, climate conditions (considered as humid warm climate, with 28.5 °C on average and 2394 mm/year precipitation. IDEAM, 2005) and deformation make fossil preservation a challenge, as well as difficult to find appropriate outcrops, therefore it is thought that some fossil-localities maybe have been totally weathered (specially those not located in creeks, such as those of Feininger et al. 1972 and those in the Nus Section on the railroad).

Graptolites were found in 7 localities to the south of La Cristalina Railway Station in La Miquera Creek and one tributary (Figure 2), the local stratigraphic column can be seen in Figure 4. Fossils are poorly-preserved in dark-grey (N3 in wet) monotonous foliated metamudstones (term slates best describe the rock appearance) with abundant organic matter (leave dark residue in hands) (Figure 3a-d), significantly bioturbated (Figure 3d). Metamudstones foliation layers are plane-parallel continuous and typically of <5 cm (Figure 3c). Lamination, typically of 1-2 mm. Framework grains of silt-size consist mainly of quartz and feldspar, in approximately the same proportion. Importantly, no graptolites have been recorded in other facies of La Cristalina Formation, such as calcareous successions. 2. New graptolite fossil localities of La Cristalina Formation 91

Figure 2-3 Outcrops, hand-sample and thin-section pictures of La Cristalina Formation, where fossils were found. a-c) Kind of outcrops where graptolites were found, it consists of fine foliated metamudstones. Metamudstones typically leave hands dark-coloured. d) Hand-sample with Pseudoamplexograptus latus (Bulman), it can be seen abundant pyritic bioturbation to the right. e, f) Thin section (PPL to the left and XPL to the right) showing quartz (Qtz), biotite (Bt) and organic matter (OM), together with feldspars, which are the main constituents of La Cristalina metamudstones 92 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Figure 2-4 Composed generalized columns of La Cristalina Formation, that represent the stratigraphic concept of La Cristalina Formation. a) Column using information obtained in La Miquera Creek and some tributaries; b) column using information from La Miquera Creek; c) column using information from Las Iglesias Creek, and d) column using information from Las Iglesias Creek and some tributaries.

2.3.2 Graptolites occurrences

Graptolites are found along 400 m in the column, where no structural disturbations were identified, although it cannot be discharged when considering several occurrences of the same fossils. Graptolites were determined by J. C. Gutiérrez-Marco as Didymograptus cf. murchisoni (Beck), Pseudamplexograptus latus (Bulman) and Glossograptus hincksii (Hopkinson). Phyllocarids remains were found too (Figure 5). The main issue with the identification were the poorly preservation (strongly oxidized) and the strong deformation (the same taxon show evidences of stretching and contracting), thereby the important taxonomic dimensions could not obtained with certainty. 2. New graptolite fossil localities of La Cristalina Formation 93

Different localities have variable assemblages. One with Dydimograptus cf. murchisoni (Beck) and Pseudoamplexograptus latus (Bulman), together with phyllocarids; other with Glossograptus hincksii (Hopkinson), and other with a single-specie with Dydimograptus cf. murchisoni. Rhabdosomes commonly are current-oriented on the bedding plane, suggesting bottom currents. In the following the taxonomy of graptolites occurrences will be showed according to website fossiilid.info.

1. Order Graptoloidea Lapworth, 1875

Suborder Dichograptina Lapworth, 1873

Family DIDYMOGRAPTIDAE Mu, 1950

Subfamily Dichograptinae Lapworth, 1873

Genus Didymograptus McCoy, 1851

Species Didymograptus murchisoni (Beck, 1839)

2. Order Graptoloidea Lapworth, 1875

Suborder Axonophora Frech, 1897

Family DIPLOGRAPTIDAE Lapworth, 1873

Subfamily Diplograptinae Lapworth, 1873

Genus Pseudamplexograptus Mitchell, 1987

Pseudoamplexograptus latus (Bulman) 94 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Figure 2-5 New graptolite assemblage of La Cristalina Formation. A-F) Didymograptus cf. murchisoni (Beck); G-J) Pseudoamplexograptus latus (Bulman); K-M) Archiclimacograptus? sp.; N, S) Glossograptus hincksii (Hopkinson), O-T) undetermined and p) phyllocarids. Fossils determined by J.C. Gutiérrez.

3. Order Graptoloidea Lapworth, 1875

Suborder Glossograptina Jaanusson, 1960

Family GLOSSOGRAPTIDAE Lapworth, 1873 2. New graptolite fossil localities of La Cristalina Formation 95

Genus Glossograptus Emmons, 1855

Glossograptus hincksii (Hopkinson, 1872)

Paleontogical material will be stored at the Paleontological Collection of the Universidad Nacional de Colombia in Bogotá, meanwhile are being studied.

2.4 Discussion

2.4.1 Age of La Cristalina Formation

Until now, La Cristalina Formation had been considered Floian to Dapingian due to Expansograptus hirundo, E. extensus, E. nitidus and Pseudisograptus? sp. (equivalent to “Didymograptus” gibberulus) (Harrison, 1929; Gutiérrez-Marco, 2011, and reviews of this study), as well as Botero (1940) and Feininger et al. (1972) as is shown in Table 2. This report is the first time that Posada (1936) graptolitic assemblage is taken into account, those suggest Floian because Clonograptus flexilis, Tetragraptus serra and Phylograptus typus. Unfortunately, all the previous works neither included pictures nor maps (except the Botero, 1940´s schema) nor the fossils have not been found again, despite we have looked for them.

To summarize, thanks to the aforementioned La Cristalina should be considered Floian to early middle Darriwilian (equivalent to late Lower Ordovician to Middle Ordovician), Table 2 shows fossil localities and the time-ranges of the fossil occurrences reported here. 96 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Table 2-2 Fossil localities, identification of graptolite assemblages and age of La Cristalina Formation. Colours according to the International Stratigraphic Chart (2016).

2.4.2 Implications of La Cristalina graptolite occurrences in Colombia

From the correlation point of view, El Hígado Formation, 460 km to the south in the UMV (Figure 1), was dated as Darriwilian according to graptolites, trilobites, conodonts and brachiopods occurrences (e.g. Borrero et al., 2007). El Hígado Formation includes the graptolite association Didymograptus murchisoni, D. aff. artus, Glyptograptus sp., Cryptograptus cf. tricornis and Hallograptus cf. bimucronatus (Mojica et al., 1987 and 1988). As well as an association of conodonts Lenodus variabilis and Eoplacognathus suecicus that have an age equivalent to Expansograptus hirundo and Didymograptus artus biozones. Hence, at least part of La Cristalina and El Hígado are coetaneous and it is reinforced that were deposited in a common basin.

La Cristalina and El Hígado formations have the same stratigraphic position and can be correlated; but, on the other hand, it cannot be considered they are the same unit, until some issues can be cleared up, such as lateral continuity. 2. New graptolite fossil localities of La Cristalina Formation 97

2.4.3 Paleogeographical implications in South America

Lower and Middle Ordovician fossil associations of Colombian La Cristalina and El Hígado formations are very similar to the fauna of Bolivia and Perú (where the others unique South American Ordovician conodonts have been found by Gutiérrez-Marco et al., 2007) as has been proposed as early as 1940 by Botero (1940). But it does not necessary means that they were deposited in the same basin, rather better it should be considered that they were deposited in an interconnected setting to the today´s west of Gondwana (Figure 7).

Borrero et al. (2007) suggested that Tremadocian Oleniids of Colombia are similar to Eastern Argentina-Bolivia Cordillera, Orinioquian planes of Venezuela and in minor extend to Baltica (e. g. Jujuyaspis-Neoparabolina of Baldis et al., 1984 and Kainella of Harrington and Kay, 1951). They also suggested that “Arenigian” fossil association is cosmopolite, with epi- to mesopelagic graptolites and rare oleniids, except coastal icnofacies of Amazonía, similar to ones of the north of Gondwana. They conclude that a number of graptolites and few benthic fossils of El Hígado Formation can be correlated with fossil associations of Contaya Formation of Perú (in Amazonía), that clearly shows Gondwanan affinities, according to Hughes et al. (1980). 98 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Figure 2-6 Paleogeographic reconstruction. Note to the souther position of Gondwana, which suggest La Cristalina graptolites came from cold waters. Modified from Staal & Hatcher (2010).

Borrero et al. (2007) pointed out that Gondwanan proto-Avalonian fauna is very similar to El Hígado Formation because the presence of Anebolithus and Ogygiocarella cf. debuchii in both areas, with Protolloydolithus (or Myttonia?) that reinforces connection. Those affinities began in the early and middle “Arenigian” of Perú (San José Formation), where there are the oldest occurrences of Anebolithus and Athiella, and then they migrate to the north to Colombia, Terranova and Gales (Gutiérrez-Marco et al., 2004).

Interestingly, Lower to Middle Ordovician beds (probably Coroico Formation) in the northermost of Bolivia Eastern Cordillera has Cryptograptus cf. schaeferi and Didymograptus association, including Didymograptus murchisoni (Mitchell et al., 2008). 2. New graptolite fossil localities of La Cristalina Formation 99

Similarly, in the Eastern Cordillera (central Perú), the San José Formation (cerro Huancampa Junín Departament) has Cryptograptus cf. schaeferi (Chacaltana et al., 2006), and in Sandia region in the south of Perú Didymograptus murchisoni was also found (Maletz et al., 2010). Those occurrences prove marine connection between graptolitic faunas of Peru, Bolivia and Colombia.

Finally, in respect of Cruziana furcífera d´Orbigny ichnofossils, they have been reported in Colombia (Araracuara), Peru, Bolivia and Argentina during Ordovician times, which also supports the Gondwanan connection (Aceñolaza and Gutiérrez-Marco, 2010).

2.4.4 Colombian tectonic scenario

It has been long suggested that Colombian tectonic setting has changed significantly to the west of the Colombian Amazonian Craton since Ordovician times, including terranes accretion (e. g. Restrepo and Toussaint, 1989; Spikings et al., 2015) and terranes long translations (e. g. Bayona et al., 2010). Coherently, many questions remain unanswered, such as the degree of deformation reminding e.g. the amphibolite facies of the Silgará Formation (sensu Ward et al. 1973. Forero, 1990; Ordovician protolite age according to Mantilla et al., 2016) in the Santander Massif in contrast to La Cristalina and El Hígado formations with very low deformation. In the same way, other questions remains unanswered such as what is the geological meaning of the Otú-Pericos Fault as terrane boarder (sensu Restrepo et al., 2011) and its close proximity to La Cristalina Formation and, if it is accepted terranes long-translations, the translation mechanisms.

As was showed, those models have wide disagreements in between. The geological history of Colombian terranes is not an easy task and it may have involved tectonic processes we have not understood yet, hence we cannot explain them satisfactory. It is even harder when we have little to guide us, and neither enough geochronological nor geochemical nor isotopic data are available for the Ordovician units. It is required much more information to understand how those events/models can be actually seen and explained regarding La Cristalina and El Hígado formations.

To summarize, considering the current petrologic and paleontological knowledge of the Ordovician units, it does not seems reasonably to favour one over the other model with 100 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

certainty, but it is clear that La Cristalina and El Hígado formations are critical to those models because they are too close to a terrane boarder.

2.5 Conclusions

La Cristalina Formation new graptolite assemblage allowed to date the unit as Floian to early middle Darriwilian in age, thus representing the upper Lower to Middle Ordovician. That is the best age resolution that the La Cristalina has ever had. It was correlated in Colombia with the coeval El Hígado Formation, which occurs in the UMV further to the south. The middle Darriwilian graptolitic assemblage of the La Cristalina and El Hígado formations were compared because are very similar to those of the northern most Eastern Cordillera of Bolivia as well as to the Amazonía and centre of Perú. It was suggested, reasonably, that La Cristalina has clear biostratigraphic affinities with western Gondwanan and, likely, were deposited in interconnected Andean basins. Finally, those occurrences were considered as valuable for regional tectonostratigraphic reconstructions that are challenging to interpret. Also it was pointed out that fossil occurrences suggested that the terrane (if so, the Chibcha Terrane cf. Restrepo et al., 2011) to the west of critical faults systems was in or very near to Gondwana by late Lower Ordovician.

Acknowledgments

To the Academic Vice-Rectory (Honor Degree Scholarship) and the Welfare Science Faculty (partially financind the academic exchange to Johannes Gutenberg Universität) of the Universidad Nacional de Colombia, the Spanish Mineco (CGL 2012- 39471) and GmasLab (Bogotá) for financing this work. As well we are grateful with the today geologists Francisco Javier Muñoz, Luis Miguel Vélez and Andrés Felipe Alvarado for their valuable help during field works, including carrying heavy samples and preparing some figures for this manuscript, as well as with the geologist Lisette Karbach and Anna Rebaza for improving this manuscript.

2.6 References

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Websites: http://fossiilid.info/ visited 22th November, 2016.

3. Colombian first ocurrences of Ordovician foraminifera: La Cristalina Formation Abstract

The low-grade metasedimentary Lower to Middle Ordovician La Cristalina Formation crops out in the Eastern flank of the Central Cordillera, to the southwest of Puerto Berrío. Thanks to conventional petrography and hand-samples preparation, there were discovered the first occurrences of Ordovician agglutinated foraminifera in Colombia. Rocks bearing-foraminifera correspond to highly bioturbated metamudstones. Occurrences were determined as Astrorhiza? sp. Foraminifera together with field work and petrographic analyses suggest those rocks were deposited in a marine epicontinental platform in a shoreface setting, with low ƒO2 and low pH conditions in the bottom of sea, as is also indicated by the rock facies association. Foraminifera found here are not useful bioestratigraphic tools owing to its broad time-range; but considering Ordovician foraminifera are very scarce during Ordovician times, this report seems of international interest, especially for South America, where only 2 occurrences have been reported up- to-now.

3.1 Introduction

3.1.1 Ordovician foraminifera

Following Pawlowski et al. (2013), who used critical molecular phylogenetic studies to improve the higher-level taxonomic classification, the phylum Foraminifera (d'Orbigny, 1826) belong to Rhysopoda, unicellular organisms. 3 highest taxonomic levels of foraminifera were proposed 1) the paraphyletic assemblage of “Monothalamids” (includes the previous orders Allogromiida, Artrorhizida, Xenophyophorea) and the orders 2) Tubothalamea (including Spirillinida, Miliolida and Ammodiscidae orders) and 3)

106 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

Globothalamea (Rotaliida with Globigerinida, Robertinida and Textulariida orders). Importantly, it seems that single-chambered to multi-chambered innovation has occurred 2 times in the last 2 groups.

The “Monothalamids” very frequently are naked and single-chambered (with agglutinated or organic-walled tests), whereas Tubothalamea and Globothalamea are multi-chambered foraminifera. Those high levels are strongly supported by genetic analyses and it seems that from the evolutionary point of view, the single- and multi-chambered is a major step in the evolution of phylum Foraminifera.

The paraphyletic “Monothalamids” group, whose phylogenetic relations are unknown up to known, are abundant at today´s high-latitude and deep-sea habitats. About 24 clades are grouped as “Monothalamids”. Pawlowski et al. (2013) pointed out that richness and genetic diversity of “Monothalamids” by far exceed the multi-chambered orders, which are the best known.

Astrorhizida Order includes almost only single-chambered agglutinated foraminifera, of which some have the ability to change the composition of the test according to the setting conditions. Species typically are cm-sized (Hedley, 1964). The agglutinated characteristic is not anymore a critical condition to identify the group, since agglutination has appeared many times in different “Monothalamids” clades.

To Astrorhizida Order belong the most of the Ordovician foraminifera reported up-to-now (e.g. Nestell & Tolmacheva, 2004; Trela, 2016), as well as those occurrences here.

From the palaeontological point of view, the undoubtedly earliest foraminifera fossil record dates from early Cambrian (Culver, 1991), although is proposed the group emerged in Neoproterozoic, according to molecular clocks (Pawlowski et al., 2003). The first foraminifera are thought were naked and single-chambered, and because of the difficult preservation it is very rare to find foraminifera fossils even in Lower Ordovician rocks. In Floian rocks are recorded the first agglutinated foraminifera (Trela, 2016), whereas by Middle Ordovician the multi-chambered foraminifera appeared (the most well-known group), but only by Carboniferous the radiation was reached. 3. Colombian first ocurrences of Ordovician foraminifera in La Cristalina... 107

The aim of this text is to publish the second report of Ordovician foraminifera of South America, which belong to the “Monothalamids” benthic agglutinated foraminifera, very likely Astrorhizida Order and Astrorhiza? sp.

3.1.2 La Cristalina Formation

High sea levels during Ordovician times are responsible of thick marine sedimentary sequences preserved to the west of Gondwana, as it can be seen today in countries such as Ecuador, Colombia, Venezuela and Chile, with the best exposures and major thicknesses and time-register in the NW of Argentina, Perú and Bolivia. The most abundant Ordovician rocks in South America are “Arenigian” (abandoned term, used here for practical-historical purposes) with lesser reports in Tremadocian and Upper Ordovician.

Ordovician sedimentary units recorded and published in Colombia were dated mainly using fossils such as graptolites, trilobites, and lesser important conodonts, brachiopods, icnofossils and acritarchs, but never before foraminifera.

The unique Ordovician unit in the Central Cordillera is La Cristalina Formation that is widely recognized in Colombia and in South America for its Ordovician graptolites, of which recently new graptolitic assemblage is reported here. That assemblage allowed to date the unit as Lower to Middle Ordovician (cf. chapter 2, Almanza et al. 2016). La Cristalina Formation extends over 45 km2 (Feininger et al., 1970) and consists of mainly low-grade metamorphic siliciclastic and calcareous successions. Metamudstones; intercalations of metamudstones and fine grained metasandstones; metamircrites, and calcareous metasandstones, laminated metamicrites and metamudstones. La Cristalina unit is located to the southwest of Puerto Berrío Town and to the south of Antioquia Railway Station named also La Cristalina, in Figure 1 is shown the geological map of the main outcrops of La Cristalina Formation. 108 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

Figure 3-1 Geological Map of the Ordovician La Cristalina Formation. Thw white rectangle shows the studied area where fossils were found. Map modified from Gómez et al. (2015) after Feininger et al. (1970). Location map modified from Gómez & Almanza (2015). 3. Colombian first ocurrences of Ordovician foraminifera in La Cristalina... 109

3.1.3 La Cristalina biostratigraphy

Table 1 shows the main authors and their contribution to the biostratigraphic knowledge of La Cristalina Formation.

Table 3-1 Main published contributions to the biostratigraphic knowledge of La Cristalina Formation. Colours according to the International Stratigraphic Chart (2016).

The first Ordovician rocks published in Colombia were those of La Cristalina Formation by Harrison (1929). Author reported some arenigian graptolites determined as Didymograptus nitidus Hall, D. extensus Hall, D. gibberulus Nich and D. hirundo Salt. Then, other 5 occurrences were mentioned (cf. Table 1), but it was until Almanza et al. (2016, cf. chapter 2) who reported the most complete biostratigraphy and reported a new Darriwillian association with Didymograptus cf. murchisoni (Beck), Pseudamplexograptus latus (Bulman) and Glossograptus hincksii (Hopkinson). Authors concluded that La Cristalina Formation dates from Lower to Middle Ordovician, taking into account for the first time the graptolites reported by Posada (1936). As well, authors concluded that La Cristalina Formation is partially coetaneous with El Hígado Formation in the Upper Magdalena Valley. 110 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

3.2 Methodology

6 field trips were done to La Cristalina Village, 109 hand-samples were collected and 64 thin-sections were made in GMAS S.A.S. laboratories and in the Universidad Nacional de Colombia-Bogotá.

Metasedimentary rocks were described as sedimentary rocks according to Folk (1980), and nomenclature used following the procedure of Fettes & Desmons (2007); therefore, as the protoliths characteristics were conserved, the most correct name was that of the sedimentary rock with the prefix meta- preceding the sedimentary name.

Mineral abbreviations, metamorphic concepts and another terms (e.g. metamorphic grade, P/T relation, isograde, etc.) were used according to Fettes & Desmons (2007). Mineral association and temperature stability conditions following Spears (1993) and Vernon & Clarke (2008).

As foraminifera were found in metasedimentary rocks (mainly metamudstones) composed from silica material and the very scarce material, it was no possible to isolate them easily. Therefore, paleontological classification was done by optical petrographic means, using 14 thin-sections, where we looked for useful structures.

3.3 Results

Fossils were found in strongly bioturbated metamudstones in the siliciclastic intercalations facies (cf. Chapter 1). At the outcrop scale, rocks containing fossils are metamudstones with fine foliation. Figure 2 shows general outcrops in La Miquera Creek and hand- samples, whereas in Figure 3 a bioturbated hand-sample. 3. Colombian first ocurrences of Ordovician foraminifera in La Cristalina... 111

Figure 3-2. Outcrop and hand-samples pictures of metamudstones bearing foraminifera. a-b) Genuine of metamudstones outcrops where foraminifera were found in La Miquera Creek; c) genuine hand-sample of bioturbated metamudstones, and d) polished hand-sample where can be observed the foraminifera with naked eyes. 112 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

Figure 3-3 Polished 3D hand-sample, showing the foliation and the subperpendicular bioturbation (borrows?). Light-pinky coloured due to biotite and enrichment in coarser grains. 3. Colombian first ocurrences of Ordovician foraminifera in La Cristalina... 113

At hand-sample scale, rocks are dark grey (N3) with weathered surface pale-orange (10YR8/6) and moderate reddish brown (10R 4/6), in wet.

Structures include very fine foliation of ≤ 5 cm, as well minor sedimentary discontinuous parallel to wavy lamination composed of abundant organic matter and anhedral pyrite (Figure 3). It is worth to mention that metamudstones have significant bioturbation perpendicular and subperpendicular to the foliation. Bioturbation can be seen clearly by changes in colour and composition and proportion of framework minerals. Bioturbated areas, likely borrows, have more coarse grained proportion (typically silt to very fine sand size, composed of red biotite, feldspar and quartz) with light pink colour (5R7/4 in wet) (see Figure 3). Stratification and foliation are not always parallel, that fact makes finding macrofossils a challenge.

As well, minor bioturbation is observed parallel to the lamination filled with pyrite, which is different than fractures with introduced pyrite.

At thin section scale (figures 4a-d), metamudstones have minor discontinuous slightly wavy to parallel lamination of < 20 μm of thickness, mainly composed of organic matter. Also, have minor subperpendicular quartz veins typically of 75 μm of thickness. But what is more evident is that rocks are strongly bioturbated which, frequently, destroys completely the original sedimentary structures (figures 4c-d). Bioturbation is enriched in framework minerals, mainly more coarse quartz and feldspar, typically very fine sand (70 μm). Petrographic description of fossils-bearing rocks can be seen in Table 2. 114 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

Figure 3-4 Thin-section pictures of samples where foraminifera were found, in plane-parallel Nichols (to the left) and cross polarized (to the right). a-b) Organic matter enriched lamina, wavy, discontinuous and parallel, and c-d) bioturbated facies showing an enrichment in framework minerals, across the stratigraphic layers.

Table 3-2. Petrographic description of selected samples. Mineral abbreviations following Fettes & Desmons (2007).

3. Colombian first ocurrences of Ordovician foraminifera in La Cristalina... 115

Opaque minerals include syn-genetic and introduced pyrite, it is remarkable the former goes according to foliation and bioturbation structures; the second type of pyrite is bigger and has euhedral shapes, frequently, associated with fractures.

Rocks containing fossils were classified as well-sorted subarcosic metamudstones with biotite and muscovite in addition to quartz and feldspar.

Astrorhiza? sp.

Fossils were determined by professors N. Tchegliakova and C. Sánchez. Figures 5a-d show fossils in thin section, and Figure 3e shows fossils in polished hand-sample, it is remarkable the big size of fossils that can be observed with naked eyes. 116 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

Figure 3-5 Benthic agglutinated foraminifera in thin-section in plane-parallel Nichols (to the left) and cross polarized (to the right). a-e) Arms of Astrorhiza? sp. and f) living Astrorhiza limicola from Lukina (2001) used to illustrate Astrorhiza? sp. specimens.

Kingdom Protozoa: Goldfuss (1817), Owen (1858) Subkingdom Gymnomyxa: Lankester (1878), Cavalier-Smith (2002) Infrakingdom Rhizaria: Cavalier-Smith (2002) Phylum Retaria: Cavalier-Smith (1999), Cavalier-Smith (2002) Subphylum Foraminifera: (d’Orbigny, 1826), Eichwald (1830), Margulis (1974), Cavalier- Smith (2002) 3. Colombian first ocurrences of Ordovician foraminifera in La Cristalina... 117

Class Astrorhizata: Saidova (1981), Mikhalevich (1995) Subclass Astrorhizana: Saidova (1981) Order Astrorhizida: Lankester (1885), Calkins (1909), Fursenko (1958) Family Astrorhizoidae: Brady (1881) Genre Astrorhiza: Sandahl (1858)

Foraminifera specimens showed in Figure 5 are fragmented, not completed specimens have been found. Test of fossils consist of almost uniquely quartz coarse silt sized (45 µm), moderate sphericity, with not observed cement. It is thought that the low metamorphic grade do not affect significantly the degree of sorting as well as minor recrystallization of quartz do not affect at least the sphericity, on the other hand roundness is not considered.

3.4 Discussion

3.4.1 Why foraminifera should be considered Ordovician

The presence of graptolitic metamudstones in La Miquera Creek and tributaries, and the facies association allow to confirm that foraminifera occurrences reported here belong to the same Lower to Middle Ordovician Formation.

3.4.2 Paleontological and paleogeographical issues

As was mentioned before, Astrorhiza genre are unilocular and benthic foraminifera that exists from Ordovician. Unfortunately this single chambered foraminifera are poorly understood because the difficult preservation during Precambrian and Paleozoic times, that is why occurrences recorded here are so valuable.

Astrorhiza? sp. foraminifera use to live freely in stable muddy or sandy bottoms, especially in the later (Buchanan & Hedley, 1960). Those foraminifera tends to make their test from the same material as the bottom (Buchanan & Hedley, 1960), it should be noted that not as coarse quartz as the test is found in rocks facies where fossils were found, as well as not the same biotite composition in the test in comparison with rocks. Therefore, the original habitat where fossils life, likely, was composed of slightly coarser bottoms more enriched in framework minerals. Vertical facies association of the local sequence 118 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación includes, to the top, intercalations of fine metasandstones and metamudstones, which is also expected in the lateral facies variation. Any of those seem more similar to the settings where fossil could life and the material from which the foraminifera tests are made of. Foraminifera occurrences were found in facies association indicative of shallower settings in comparison with facies where graptolites were found.

Astrorhiza limicola and Astrorhiza arenaceous are genuine species of the group, they preferentially live in cold open oceans (deeper than sublittoral habitats), those species have been found in an association with depth up to 3100 m, but as shallow as 8 m (Buchanan & Hedley, 1960; Lukina, 2001). On the other hand, those foraminifera do not usually borrow, they are active predators with not so active displacements, 25 cm in 24 hours as observed by Buchanan & Hedley (1960) in A. limicola.

The abundant pyrite observed in rocks might suggest low oxygen availability and high organic availability, although strong bioturbation suggest not so anoxic bottoms for those rocks facies.

With respect to other formainifera occurrences found in South America, the foraminifera found by Nestell et al. (2011) in the San Juan Formation in Argentina have an association of conodonts that dates Floian, a stage is thought to be present at La Cristalina Formation. Argentinan fossils belong to the same order Astrorhizida as Colombian ones, but to different families.

On the other hand, rock facies are different, in the San Juan Formation fossils are associated to shallow high energy carbonate platform, in contrast to the siliciclastic platform facies of La Cristalina Formation (cf. chapter 2).

Foraminifera occurrences of La Cristalina Formation are the first in Colombia and, importantly, open the possibility to find those organisms in other equivalent units in the northwestern of South America, such as in El Hígado Formation or Peruvian Ordovician units. Although those occurrences are no useful to date La Cristalina Formation because the broad age-range, they are valuable for Ordovician paleontological research and seems of international interest. 3. Colombian first ocurrences of Ordovician foraminifera in La Cristalina... 119

3.4.3 Lithologic facies, sedimentary setting and metamorphism

According to the petrographic analyses, the protolith could have more than about 50 % of phyllosilicates (clays) with a framework of about coarse silt grain-sized, composed by quartz and feldspars, in addition to accessory minerals such as opaques, zircons, together with organic matter.

Considering field, hand-sample and thin section descriptions, including mainly facies association and sedimentary structures of the local sequence, it can be proposed, reasonably, that the unit was deposited in an epicontinental platform in a marine setting, likely, in shoreface (Nichols 2000, Folk 1930, Hampson & Storms 2003) with relatively calm bottoms. Furthermore, sea bottoms had to be soft enough to allow strong bioturbation, which is also indicative of not too depth settings. Pyrite is indicative of low

ƒO2 as well as low pH conditions, probably associated with high organic decomposition.

Finally, metamorphic low grade is suggested by biotite-white mica association, as well as by very fine grained and very poor-developed schistose texture. Those features are consistent with green schist facies, which is also coherent with the observed low grade microtectonic deformation that includes minor undulant extinction, as the highest grade.

3.5 Conclusions

The low grade metasedimentary La Cristalina Formation has been known by its Lower to Middle Ordovician graptolite assemblages, but here the first Ordovician foraminifera were reported. Foraminifera were determined provisionally as Astrorhiza? sp. taking into account the petrologic descriptions at outcrop-, hand sample- and thin section-scale, as well as biostratigraphic indicators, it is reasonable to infer that the local rock facies association belong to continental marine shoreface settings in cold waters. These fossil occurrences call us to carry out biostratigraphic works in the Ordovician units of Colombian, especially in La Cristalina and El Hígado formations.

Acknowledgments

To the Academic Vice-Rectory (Honor Degree Scholarship) and the Welfare Science Faculty (partially finance the academic exchange to the Johannes Gutenberg Universität) of the Universidad Nacional de Colombia, the Spanish Mineco (CGL 2012- 39471) and GmasLab (Bogotá) for financing this work. As well we are grateful with the today geologists Francisco Javier Muñoz, Luis Miguel Vélez and Andrés Felipe Alvarado for their 120 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación valuable help during field works, including carrying heavy samples and preparing some figures for this manuscript, as well as with the geologist Lisette Karbach and Anna Rebaza for improving this manuscript.

3.6 References

Aceñolaza, F.G. 1980. El Sistema Ordovícico en Sudamérica. 26th Congreso Geológico Internacional, París, Francia. Almanza, M.F., Jaramillo, J.M., Tchegliakova, N. 2013., Estudios petrológicos y primer reporte de foraminíferos aglutinados de la Formación La Cristalina: Un aporte al conocimiento del Ordovícico de Colombia, Tesis de pregrado, Universidad Nacional de Colombia-Bogotá, 38p. Almanza, M.F., Jaramillo, J.M., Gutiérrez-Marco, J.C., Sánchez, C.A., Patarroyo-Gama, P, Tchegliakova, N. 2016. Lower to Middle Ordovician La Cristalina Formation: After 50 years new fossil localities were found, including the first Ordovician foraminifera in Colombia. 35th International Geological Congress, Proceedings, Cape Town, South Africa. Botero, G., 1937. Bosquejo de paleontología colombiana. Tesis de pregrado, Escuela de Minas de Medellín. 2nd edition. Imprenta Nacional, Bogotá, Colombia, 84p. Botero, G. 1940. Geología sobre el ordoviciano de Antioquia. Minería, Bogotá, Colombia, 17, 99, 8249-8256. Buchanan, J.B., Hedley, R. H. 1960. A contribution to the biology of Astrorhiza limícola (foraminifera). Journal of Marine Biology Asociation United Kingdom. 39: 549-560. Cooper, R.A., Rigby, S., Loydell, D.K., Bates, D.E.B. 2012. Palaeoecology of the Graptoloidea. Earth-Science Reviews, 112: 23–41. Feininger, T., Barrero, D., Castro, N., Ramírez, O., Lozano, H., Vesga, J. 1970. Mapa Geológico del Oriente del Departamento de Antioquia, Colombia. Cuadrángulo I-9, y partes de los cuadrángulos H-9, H-10, I-10, J-9 y J-10. Instituto de Investigaciones Geológico Mineras-United States of America Geological Survey. Scale 1:100 000, Bogotá, Colombia, 2 sheets. Feininger, T., Barrero, D., Castro N. 1972. Geología de parte de los departamentos de Antioquia y Caldas (subzona II-B), Boletín Geológico del Instituto Nacional de investigaciones Geológico-Mineras (Ingeominas), Bogotá, Colombia, XX, 2, 192p. Fettes, D., Desmons, J. (Eds.). 2007. Metamorphic rocks: A classification and glossary of terms. Recommendations of the International Union of Geological Sciences Subcomission on the systematics of Metamorphic Rocks. Cambridge University Press, United Kingdom, 244p. Folk, R.L., 1980. Petrology of sedimentary rocks. Hemphill Publishing Company, Texas, USA, 179p. Fonseca, H.A., Fuquen, J.A., Mesa, L.D., Talero, C.A., Pérez, O.G., Porras, J.J., Gavidia, O., Pacheco, S.M., Pérez, J.F., Amaya, E., García, Y., Farfán, E. 2011. Cartografía geológica de la Plancha 133 Puerto Berrio. Universidad Pedagógica y Tecnológica-Servicio Geológico Colombiano, Sogamoso, Colombia, Scale 1:100 000, 1 sheet. Forero, A. 1990. The basement of the Eastern Cordillera, Colombia: An allochthonous terrane in northwestern South America. Journal of South American Earth Sciences, 3, 2/3, 141-151. Fuquen, J.A., Gómez, L.A., Quintero, C., Patiño, A., Beltrán, A., López, C., Lancheros, J. A., Renzoni, G., Manrique, M. 2009. Cartografía geológica y muestreo geoquímico escala 1:100.000 de la Plancha 149 Puerto Serviez Valle Medio del Magdalena. Scale 1:100 000, Servicio Geológico Colombiano, Bogotá, Colombia, 1 sheet. Gómez, J., Montes, N.E., Nivia, A., Diederix, H., compilers. 2015. Mapa Geológico de Colombia. Scale 1:1 000 000, Servicio Geológico Colombiano, Bogotá, Colombia, 2 sheets. Gómez, J., Almanza, M. F., editors, 2015. Compilando la geología de Colombia: Una visión a 2015. Servicio Geológico Colombiano. Bogotá. GRP. 2008. Geología de la plancha 149 Puerto Serviez. Scale 1:100 000, Servicio Geológico Colombiano, Bogotá, Colombia, 1 sheet. Hampson, G.J., Storms J.E.A. 2003. Geomorphological and sequence stratigraphic variability in wave- dominated, shoreface-shelf parasequences. Sedimentology, 50, 667–701. DOI: 10.1046/j.1365- 3091.2003.00570.x Haq, B.U., Shutter, S.R. 2008. A chronology of Paleozoic sea-level changes. Science. 322 (5898): 64-68. DOI: 10.1126/science.1161648 Hedley, R.H. 1964. The Biology of Foraminifera. International Review of General and Experimental Zoology, 1:1-41. London, England. Harrison, J.V. 1929. The Magdalena Valley, Colombia. South America. International congress. Pretoria, South Africa. Compe Rendu. II: 399-409. Likina, T.G. 2003. Foraminifera of the Laptev Sea. Protistology, 2 (2): 105-122 3. Colombian first ocurrences of Ordovician foraminifera in La Cristalina... 121

Maletz, J., Reimann, C., Spiske, M., Bahlburg, H., Brussa, E.D., 2010. Darriwilian (Middle Ordovician) graptolite faunas of the Sandia Region, southern Perú. Geological Journal, 45, 397–411. DOI: 10.1002/gj.1182 Nestell, G., Heredia, S., Mestre, A., Beresi, M., González, M. 2011. The oldest Ordovician foraminifers (Oepikodus evae conodont Zone, Floian) from South America. Geobios, 44, 601–608. DOI: 10.1016/j.geobios.2011.02.007 Pawlowski, J., Holzmann, M., Berney, C., Fahrni, J., Goodays, A. J., Cedhagen, T., Habura, A., Bowser, S.S. 2003. The evolution of early Foraminifera. PNAS, 100(2): 11494-11498. Posada, J.C. 1936. Bosquejo geológico de Antioquia. Anales de la Escuela Nacional de Minas, Medellín, Colombia. 38, 1-51. Sabirov, A.A. S. B. Gushchin. 2006. New Early Ordovician Calcareous Foraminifers of the Middle Tien Shan. Paleontological Journal, 40(1): 11-19. Scheibe, R. 1933. Informe sobre los resultados del trabajo de la Comisión Científica en Antioquia. Compilación de los Estudios Geológicos Oficiales de Colombia, Servicio Geológico Nacional, Tome I, Bogotá, Colombia, 67-167. Spears, F. 1993. Metamorphic phase equilibria and Pressure-Temperature-time Paths. Mineralogical Society of America, Michigan, USA, 799p. Trela, W. 2016. Agglutinated benthic foraminifera in Ordovician and Silurian black mudrock facies of the Holy Cross Mountains (Poland) and their significance in recognition of oxygen content. Palaeogeography, Palaeoclimatology, Palaeoecology 457: 242–246. URL: http://dx.doi.org/10.1016/j.palaeo.2016.06.015 UPTC. 2012. Geología de la plancha 133 Puerto Berrío. Scale 1:25 000, Servicio Geológico Colombiano- Universidad Pedagógico y Tecnológica de Colombia, Bogotá, Colombia, 1 sheet. Vernon, R. H., Clarke, G. L. 2009. Principles of Metamorphic Petrology. 1st edition, 446 p, Cambridge University Press.

4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic porphyries and Paleocene S-type granitoids intruded La Cristalina Formation: Petrological approach and stratigraphic discussion Abstract

To the southeast of Antioquia, in the eastern flank of the Central Cordillera granodioritic to dioritic rocks, rhyodacitic porphyries and S-type granitoids intruded the low-grade metamorphic Ordovician La Cristalina Formation. Field work, petrography, XRF geochemical analyses and U-Pb LA-ICP-MS geochronological datings were performed in order to describe and classify those rocks. Those studies suggest that granodioritic to dioritic rocks are, probably, related to the Middle to Upper Segovia Batholith, rhyodacitic porphyries can be related to “Hypabyssal felsic rocks to the east of the Otú Fault” (Feininger et al. 1970) with an unknown age, whereas the Paleocene granitoids has S- type strong evidences, but the petrogenetic mechanisms remains unclear. Finally, igneous rocks allow concluding that the low grade metamorphism of La Cristalina Formation occurred, likely, before Middle Jurassic, and that during Paleocene times La Cristalina was shallow enough to permit hypabbysal felsic rocks to crystallize.

4.1 Introduction

At least 3 different igneous units intruded the graptolitic Lower to Middle Ordovician La Cristalina Formation (cf. chapter 2), those include

1) Granodioritic to dioritic rocks equivalent to the “d” unit included in the “Igneous rocks mainly to east of the Otú Fault” (sensu Feininger et al., 1970);

124 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

2) porphyries grouped as “Hypabyssal felsic rocks to the east of the Otú Fault” sensu Feininger et al. (1970), and 3) some S-type granitoids first described here.

Those units crop out in the eastern flank of the Central Cordillera of Colombia and to the southwest of Puerto Berrío, as can be seen in Figure 1. Figure 2 shows the geologic map of the area and the studied localities, coordinates can be obtained from Table 1.

The aim of this chapter is to study igneous rocks that intruded La Cristalina by using field observations, petrography, geochemistry, trace elements and U-Pb datings. 4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 125

126 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

Figure 4-1 Geological map of the studied area. The white rectangle shows the studied area in the eastern flank of the Central Cordillera of Colombia, next to the Middle Magdalena Valley. It should be highlighted 2 different basements: to the west of the Otú Fault a Triassic metamorphic complex, and to the east some Precambrian gneisses. In the studied area, the critical Otú Fault is displaced by the Palestina Fault. Map modified from Gómez et al. (2015) after Feininger et al. (1970). Location map modified from Gómez & Almanza (2015).

Figure 4-2. Geological Map of the studied area (as shown in Figure 1). Granitoids and “Hypabyssal rocks to the east of the Otú Fault” are mapped as point-elements because outcrop size. “Felsic and intermediate volcanic rocks to the east of the Otú Fault” and “Felsic porphyries to the east of the Otú Fault” sensu Feininger et al. (1970). Map modified from Gómez et al. (2015) after Feininger et al. (1970).

In the following, it will be summarized the current knowledge of the igneous rocks that intruded La Cristalina Formation; rhyolites and andesites and some Precambrian paragneisses (cf. Carmona et al., 1999) that underlies the Ordovician rocks. Taking into account the poor-knowledge of the local igneous rocks, variations of igneous intrusions and critical faults that affected all the units, the information cited here should be considered only for a local interpretation (figures 1 and 2), hence no regionalization is recommended.

Likely, the first who described igneous rocks to the east of Antioquia were T. Ospina and R. Scheibe, in the earliest XX century, as granitic and dioritic rocks (Ospina, 1911; 4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 127

Scheibe, 1933). Afterwards, Botero (1940, 1941) described igneous bodies intruding Paleozoic rocks that caused contact metamorphism and formed marbles and quartzites to the southeast of Antioquia. Critically, the author did not take into account the Palestina and Otú faults because were not discovered by that time, hence some low to medium- grade metamorphic rocks located to the west of those faults were considered Ordovician because La Cristalina graptolites (nowadays, those low to medium metamorphic rocks to the west of the fault are rather better considered as a Triassic metamorphic complex, cf. e.g. Restrepo et al. 2011). Therefore, it is doubtful if all those igneous rocks cited by Botero (1940) intruded either the graptolitic sequence or the Triassic metamorphic complex, or both. Importantly, Botero (1940) proposed that those intrusive bodies belongs to an extensive batholith of more than 8000 km2 and coined the name Antioqueño Batholith. According to the today´s view (e.g. Leal-Mejía, 2003) that batholith main outcrops are to the west of the studied locality and thus to the west of Otú-Pericos Fault, after displaced by the Palestina Fault.

Feininger et al. (1970, 1972) mapped and constrained the geological evolution of the east of Antioquia, mentioning for the first time the critical Palestina Fault and differentiating units in both sides of the fault. Feininger et al. (1970) mapped at 1:100 000 scale, thus the Antioqueño Batholith sensu Botero (1940) was re-interpreted by Feininger et al. (1972) as different igneous units, such as those that will be cited here. Feininger et al. (1970, 1972) divided igneous rocks that intruded or are related with La Cristalina Formation in 3 units: 1) “Volcanic felsic Rocks to the East of the Otú Fault” of special interest is the subunit “Volcanic Rocks”; 2) “Igneous rocks mainly to the east of the Otú Fault” out of which we will focus on the sub-unit “d”, and 3) “Hypabyssal felsic rocks to the east of the Otú Fault”.

With respect to the “Volcanic Rocks”, Feininger et al. (1972) described afanitic rocks that have dark, greenish and light grey colour with less than 1 % of phenocrysts (mainly feldspars), as well as massive and, in a lesser extend, laminated textures.

On the other hand, González (2001) named the “Volcanic Rocks” as “La Malena Volcanic Set” (“LMVS”). “LMVS” was described by González (2001) as effusive rhyolitic to rhyodacitic volcanic fluxes, volcanic breccias and, to the top, tuffs; hence to the medium and top of the sequence there are evidences of explosive volcanism. Locally, basaltic dikes, lamprophyres, and andesitic and traquitic porphyries. The unit also includes 128 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación volcanic mud-flows. According to the author, those rocks were crystallized and deposited in a subaquous setting and have gold occurrences. Lastly, the author suggested that the Segovia Batholith intruded the “LMVS” and thus interpreted that an explosive-effusive acid volcanic magmatism of “LMVS” was followed by a plutonic magmatism that correspond to the Segovia Batholith.

To the northeast of La Cristalina Formation at the Puerto Serviez Sheet were mapped some afanitic rocks as “LMVS” by Fuquen et al. (2009), following the name and genetic proposal of González (2001). According to Fuquen et al. (2009), the “LMVS” consist of highly fractured basic tuffs; peralkaline and hypocrystalline andesites with microporphyritic texture, in addition to ash and lapilli lithic tuffs. Those rocks are covered by Neogene deposits of pebble and granule conglomerates.

Finally, Fonseca et al. (2011) mapped “LMVS” at 133 Puerto Berrío Sheet as afanitic and porphyritic textures composed mainly of volcanic glass (most showing devitrification to quartz, feldspars, biotite, muscovite) and phenocryst of quartz, K-feldspar (sanidine, anorthoclase), plagioclase and biotite, with pyritic mineralization. Authors remarked that quartz, chlorite and epidote are introduced minerals. Also, minor tuffs were mentioned. Rocks were classified as rhyodacites, andesites, trachites and latites. Coronitic and cummulitic textures were also observed, as well as fluidal texture and low grade metamorphism. As well, authors observed a disconformity with the underlying Precambrian gneisses at La Botella Creek.

The subunit ”Volcanic Rocks” crops out in the area and was studied here only by petrographic means. Feininger et al. (1972) inferred a faulted contact between the La Cristalina Formation and the “Volcanic rocks”, but during the field we evidenced this contact might include either unconformities or/and faults (Figure 2). Critically, Feininger et al. (1972) observed that xenoliths of the “d” unit were included in the “Volcanic rocks”, therefore “Volcanic rocks” are older. That relation was also observed by Fonseca et al. (2011) in the Santa Cruz Creek and La Palmera Farm. González et al. (2015) suggested the Middle Jurassic age for this unit according to U-Pb concordant age of 163,51±0,95 Ma.

With respect to the “d” unit, it crops out ~700 km2, but here are only described those that crop out in the studied area (~5 km2). According to Feininger et al. (1972), the unit consist 4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 129 of dioritic and quartz-dioritic rocks, massive to less commonly laminated (differentiated by the mafic and felsic mineral proportions with a diffusive contact) and, locally, strongly gneissic. Those rocks have hypidiomorphic and equigranular texture, are composed mainly of plagioclase, quartz, orthoclase, hornblende, biotite and chlorite. To the southwest of La Cristalina Formation, the unit is metamorphosed by faults. Authors pointed out that the “d” unit produced contact metamorphism in La Cristalina Formation forming marbles. The same authors reported K-Ar ages of 160 ± 7 Ma in the Montecristo Quarry (near to the Cabañas Railroad Station and to the west of La Cristalina Formation) and suggested that veins bearing gold were mined by Frontino Mines Gold Company.

González (2001) considered that the unit “Igneous rocks mainly to the east of the Otú Fault” (and therefore the “d” unit) belongs to the Jurassic Segovia Batholith (age assigned by the radiometric age of Feininger et al., 1972) originally proposed by Álvarez (1981).

Segovia Batholith is described by Fuquen et al. (2009) in the 149 Puerto Serviez Sheet as massive and laminated dioritic, granodioritic, quartz-dioritic and granitic rocks. Grey granodioritic rocks have faneritic fine-grained texture and are composed of hornblende, biotite and chlorite. Two-feldspar granites are melanocratic and have biotite, chlorite and amphiboles, with chlorite, biotite and sericite as alteration minerals. Besides, authors observed that the Segovia Batholith has protomylonites. Fuquen et al. (2009) observed that the Jurassic Segovia Batholith intruded La Cristalina Formation and mapped the “d” unit of Feininger et al. (1970) in 149 Sheet as the Segovia Batholith with few differences.

On the other hand, Fonseca et al. (2011) described the Segovia Batholith in the 133 Puerto Berrío Sheet (to the north of the studied area) as metamonzogranites bearing hornblendes, syenogranites, k-feldspar-metagranites, monzonites, granodioritic and dioritic rocks. Some of them bearing gold. Critically, they observed an unconformity with the overlying Lower Cretaceous rocks bearing ammonites, named “Segovia Sedimentites”.

Leal-Mejía (2011) carried out petrographic, geochemical and U-Pb LA-MC-ICP-MS datings of the Segovia Batholith to the north of the studied area. Author suggests is composed of medium- to coarse-grained faneritic rocks that include massive biotite dioritic rocks to quartz-dioritic rocks. Minerals include quartz (30 %); strongly sericited and not-zoned plagioclase (35 %); k-feldspar including orthoclase and microcline (20 %); 130 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación hornblende (10 %) as primary and as pseudomorphs after pyroxenes and, as accessory minerals, biotite altered to clinochlore (<5 %), clinopyroxene, orthopyroxene, ilmenite, apatite, clinozoisite and very few circons. Author also observed local variations to quartzmonzonites, granodioritic rocks and gabbros. In some areas, rocks are slightly banded to strongly gneissic in aspect. U-Pb datings suggest ages between 166.5 +2.3/- 2.5 to 158.7 ±2.0 Ma (Middle to Late Jurassic) with few inhered ages. Author suggest calc-alkaline and metaluminous I-type intrusions, in a pre-collision and subduction setting with a less contaminated magma. Critically, the author analysed rocks to the north and very close of La Cristalina Formation, but to the west of the Palestina Fault.

Finally, the “Felsic porphyries to the east of the Otú Fault” unit corresponds to felsic and mainly dacitic hypabyssal rocks with porphyritic texture that crop out as small (<50 m) and irregular bodies, that intruded La Cristalina Formation and the Precambrian paragneisses (named by Feininger et al. 1972 as “Precambrian gneisses”). Feininger et al. (1972) suggest porphyries have phenocrysts of not-zoned plagioclase and quartz with 10:1 proportion, with a fine granular matrix of feldspar, quartz, biotite, muscovite and allanite, as well as apatite and magnetite as accessory minerals. Authors proposed a “Lowee Paleozoic” age for those prophyries, because they did not observe cross-cut relations with the other youger igneous rocks. As well, authors suggest “Felsic porphyries to the east of the Otú Fault” have the same metamorphism of La Cristalina Formation because rocks are deformed, and authors suggested plagioclases are not zoned due to metamorphic homogenization.

4.2 Methods

6 field trips have been done to Puerto Berrío (Antioquia), 109 hand-samples were collected including igneous, Ordovician metasedimentary rocks and Precambrian gneisses. 64 thin-sections were made at GMAS Laboratories and at the Universidad Nacional de Colombia-Bogotá. Metamorphic and igneous rocks descriptions recorded here, mineral abbreviations, concepts and another terms were used according to Fettes & Desmons (2007) and Le Maitre (2002).

X Ray Fluorescence measurements: measurements were performed in the AcmeLabs (Canada) and at the Universidad Nacional de Colombia-Bogotá. 4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 131

AcmeLabs (FLC-02, FLC-16): Total rock composition (major and minor oxides) was determined using 0.2 g of the sample. Emission Spectroscopy-ICP followed by Lithium Metaborate/Tetraborate Fusion and Digestion in a solution with nitric acid. Ignition Losses (LOI) was calculated by weight difference after 1000 °C ignition. Total carbon and sulphur by weight by Leco. In order to analyse the trace elements, ICP-MS was used and to determinate REE and refractory elements, the mass spectrometry (ICP), followed by lithium metaborate/tetraborate fusion and digestion with nitric acid, using 0.2 g of the sample. In addition, 0.5 g it was used for simple digestion in aqua regia using ICP, and finally, precious and base metals were worked out.

Universidad Nacional de Colombia (CLC-07, CLC-09, CLC-18): Samples were measured in a MagixPro PW-2440 Phillips XRF spectrometer, with Ro tube, and maximum 4 KW power. The spectrometer has a resolution of 200 ppm for heavy metallic elements. Powdered samples of <100 µm were heated to 105 °C for 12 hours and mixed with wax (10:1) (MERK Laboratory), then were pressed hydraulically until 120kN. Those were measured with SEMIQ-2016. Semiquantitative analyses were done with IQ (11 scannings). H, C, Li, Be, B, N, O and transuranim elements were not measured.

U-Pb datings: were performed at the University of Arizona by Laserchron Center following the method of Gehrels et al. (2006, 2008). U–Pb measurements in zircon single grains were conducted by LA-ICP-MS. For magmatic zircon tips were selected for analysis, in order to check the younger magmatic crystallization age.

Weight average and concordia age calculations as well as detrital zircon histograms were plotted using Arizona Laserchron Excel macro age pick program.

4.3 Results

In the following will be described (at outcrop-, hand sample- and thin section-scale, and geochemically) the granodioritic to dioritic rocks, rhyodacitid porphyries and S-type granitoids. “Volcanic Rocks”, on the other hand, were classified by petrographic means as rhyolites and horblende andesites.

4.3.1 Rock descriptions at outcrop, hand-sample and thin-section scale

S-type granitoids

At outcrop scale, granitoids have 1 up to 20 m of thickness (Figure 3). In Figures 3a-c can be seen how the igneous rocks clearly intruded the Ordovician metasedimentary 132 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación succession, following foliation planes. 3 different outcrops were taken into account, each one separated by c.a. 500 m (Figure 2).

At hand-sample scale (Figure 3g), rocks have an inequigranular porphyritic (microporphyritic) to slightly porphyritic texture (<1 mm), also a fluidal. Rocks are leucocratic with mainly middle grey (N5) to light grey (N7) colours. Alteration surfaces are greyish brown (5YR3/2), dark yellowish orange (10YR6/6), dark greenish grey (5GY 4/1) and light brown (5YR 5/6), in wet. Less commonly, this facies include rocks with faneritic texture with medium to fine gran size (<5 mm).

Those porphyritic rocks have phenocrysts composed mainly of quartz (including minor bipyramidal-shape) and feldspars. In the matrix can be seen quartz and feldspar, minor biotite. As alteration minerals, significant chlorite and Fe-oxides and hydroxides. Finally, quartz and muscovite filled some minor fractures, whereas other fractures have chlorite and significant pyrite. 4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 133

134 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

Figure 4-3. Outcrops and hand-samples of granitoids (S-type) and granodioritic to dioritic rocks in La Miquera Creek. a-b) Outcrop of granitoids from the sample locality, sample FLC-02 showing clearly an intrusive contact; c) granitoid sample (FLC-16), red line shows the contact with La Cristalina Formation; d) genuine granodioritic to dioritic rocks outcrops and falls along La Miquera Creek; e) compositional banding, with some minor hornblende and biotite enrichments, and f) polygonal structures with diffuse contacts and mafic minerals-enrichments. Hand-sample pictures of g) granitoids to upper side FLC-02 sample with porphyritic texture and fine grained phenocrysts and, to the lower side, the FLC-16 sample texture which is lightly porphyritic and fluidal, some fractures show significant quartz and muscovite as filling minerals; h) granodioritic to dioritic rocks showing faneritic texture and showing leucocratic to mesocratic character due to an enrichment in mafic minerals.

At thin section scale, samples are fine-grained (1 mm) and have a holocrystalline, inequigranular, together with fluidal texture (Figure 4a-b). Sample FLC-02 has dynamic metamorphism with sigma objects (figures 4e-f). Biotite aggregates, likely, represents either hidrothermal alteration or evidences of genetic mechanisms (Figure 6). Figures 4-6 show remarkable and critical characteristics of textures, minerals and mineral assemblages of both samples, and Table 1 shows petrographic and microstructural descriptions.

Phenocrysts in both samples include quartz as single crystals (including minor bipyramidal crystals in sample FLC-02, figures 4c-d) or aggregates (polycrystalline grains, figures 5a-b); also, include plagioclase strongly sericited and kaolinitized K-feldspar. Besides, a single euhedral pyroxene with a retrograde rim in sample FLC-02 crystallized from the original magma. On the other hand, sample FLC-16 has strongly fractured garnets (figures 6a-b).

According to hand-samples and thin-sections (following Le Maitre, 2002), rocks were classified as granitoids according to modal phenocrysts composition, specifically as biotitic granitoids bearing sericite (FLC-02) with dynamic metamorphism, and biotitic and sericitic granitoids bearing garnets (FLC-16).

Finally, some microstructures account for minor deformation conditions. In quartz, strong undulant extinction, deformation lamellae and inclusion alignment. Undulant extinction was also observed in feldspars and biotites. In some grains have been observed grain rotations (figures 4e-f). Furthermore, recrystallization mechanisms in quartz include Bulging Recrystallization (BGR) and Subgrain Rotation (SGR) (cf. Passchier & Thrown, 2005). Finally, it has to be highlighted that grains included in the magma (xenocrysts) have higher temperature deformation mechanisms, which do not represent the granitoids deformation conditions, such as polycrystalline quartz. 4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 135

Figure 4-4. FLC-02 granitoid thin-section photographs in plane-parallel Nichols (to the left) and cross- polarized (to the right). a-b) Here is showed the porphyritic texture, biotites aggregates, likely, due to either genetic mechanisms or hydrothermalism; c, d) in centre, bipyramidal quartz phenocryst and to the right-down quartz is partially re-crystallized by bulging re-crystallization (cf. Passchier & Trown, 2005), with surrounding “matrix” of quartz, K-feldspar and biotite aggregates. Upper left there is a strongly sericited plagioclase, and e, f) in centre, plagioclase δ-object showing simple shear. 136 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

Figure 4-5. FLC-02 granitoid thin-section photographs in plane-parallel Nichols (to the left) and cross- polarized (to the right). a-b) At the centre an aggregate of quartz, likely, an assimilated xenocryst, and c-d) euhedral pyroxene showing and outer reacting corona composed of biotite/amphibole (?). 4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 137

Figure 4-6. FLC-16 granitoid thin section photographs in plane-parallel Nichols (to the left) and cross- polarized (to the right). a-b) Strongly fractured garnets xenocrysts and c-d) feldspar phenocryst in a matrix composed mainly of quartz, feldspar and biotite.

Table 4-1. Selected petrographic description of granitoids (FLC-02 and FLC-16), granodioritic to dioritic rocks (CLC-07, CLC-09, CLC-10) and rhyodacitic porphyries (CLC-18). The last 2 columns show the microstructures and deformation mechanisms by petrographic means according to Passchier & Trown (2005).

138 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

Granodioritic to dioritic rocks (CLC-06, CLC-07, CLC-09, CLC-10, CLC-11)

At outcrop scale, granodioritic to dioritic rocks crop out as 2 main bodies that intruded La Cristalina Formation with ca. 60 000 m2 (Figure 1). As well, minor intrusions up to 50 m can be observed in La Miquera and Las Iglesias creeks (figures 3d-f).

Samples studied here come from the northwestern outcrops that intruded La Cristalina Formation. It corresponds to a body of ca. 2.2 km cropping out along La Miquera Creek with an area of ca. 38 000 m2 (Figure 2). Rocks are massive with minor fractures. Minor local banding is formed by relatively more mafic minerals enrichments (hornblendes and minor biotites). Minor quantity of quartz-veins (most of <10 cm) cross-cut the granodioritic to dioritic rocks in La Miquera Creek. Some polygonal structures of cm-size were observed too, with major proportions of mafic minerals and diffusive contacts (Figure 3f).

At hand sample scale (figure 3h), rocks are faneritic, equigranular, most of them with crystals-size variations of 1-5 mm, and minor minerals >5 mm (some hornblendes reach 15 mm) (Figure 3f). Rocks are leucocratic to minor mesocratic, have very light grey colour and minor darker medium grey.

Compositionally, correspond to euhedral feldspar (60-30 %), euhedral hornblende (50-20 %), euhedral biotite (10-20 %) and subhedral quartz (35-10 %), with variations of hornblende up to 60% in the darkest bands. Rocks were classified as granodiorites to diorites, minor banded, with variations to hornblend diorites rocks and in a lesser extend diorites.

At thin section scale (see Table 1), not-deformed samples CLC-07, CLC-09 and CLC-10 are faneritic, holocrystalline, equigranular, with fine to medium grained texture (Figure 8a- p). Plagioclases are zoned and have reaction boarders with quartz, most of them sericited, with minor epidote included in crystals in one sample. Feldspars include minor exolution textures with quartz. Clinoamphiboles are minor chloritized with Fe oxides and hydroxides. As accessory minerals are apatites, titanites and very few zircons.

Samples CLC-07, CLC-09, CLC-10 were classified as biotitic and clino-amphibolic granodiorites; clino-amphibolic granodiorites, and clino-amphibolic biotitic granodiorites. It is highlighted that granodiorites have very low K-feldspar modal proportion that make 4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 139 samples be classified very near to granodiorites-tonalites border. 140 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 141

142 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

Figure 4-7 Thin-section pictures of granodioritic to dioritic rocks and rhyodacitic porphyritic rocks in plane- parallel Nichols (to the left) and cross-polarized (to the right). a-b) Biotitic and clino-amphibolic granodiorite (CLC-07), c-f) clino-amphibolic granodiorite (CLC-09), g-l) clino-amphibolic biotitic granodiorite (CLC-10) and m-p) biotitic andesite with an alkaline-feldspar rhyolitic matrix (CLC-18).

Rhyodacitic porphyries (CLC-18)

At outcrop scale, minor intrusions up to 100 m can be observed in La Miquera Creek in Figures 8a-b is showed a clearly intrusive contact.

Figure 4-8 Rhyodacitic porphyries (CLC-18) at outcrop and hand-sample pictures. a) Contact between rhyodacitic porphyries and La Cristalina Formation; b) rhyodacitic porphyries intruding La Cristalina Formation in La Miquera Creek, intrusion follows the foliation planes of La Cristalina, and c) hand sample of rhyodacitic porphyries.

At hand sample scale, CLC-18 is coarse-grained (5 mm), with a porphyritic texture, mainly composed of phenocrysts of feldspar and very minor quartz (Figure 8d), and was classified as andesitic porphyries. Rocks are mesocratic and have darker medium grey colour.

At thin-section scale (Figure 7m-p, Table 1), CLC-18 has a porphyritic texture, coarse- grained, with holocrystalline matrix. Phenocrysts include not-zoned plagioclases, biotites in aggregates and minor quartz. Matrix consist of anhedral quartz and feldspars, with 4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 143 minor biotite. Zircons are euhedral and are more abundant than in granodiorites and diorites. Rocks were classified as biotitic andesites with an alkaline-feldspar rhyolitic matrix.

4.3.2 Geochemical analyses

Table 2 shows the geochemical measurements performed. Major, minor and trace elements were plotted in different diagrams, as is shown in figures 9 and 10. Trace elements and REE were measured just for granitoids. 144 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

Table 4-2 Major, minor and trace elements measurements by XRF of granitoids (FLC-02 and FLC-16), granodioritic to dioritic rocks (CLC-07, CLC-09 and CLC-10) and rhyodacitic porphyries (CLC-18).

4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 145

Granitoids

XRF measurements (Table 2) show that granitoids (FLC-02 and FLC-16) crystallized from a highly felsic magma with high SiO2 70.3-72.7 % (oversaturated), high Al2O3 14.9-15.7 3 %, low CaO (1.0-1.5 %) and low Fe2O *(1.0-2.5 %). Besides, rocks have slightly higher wt. percentage of Na2O (4.2-4.8 %) in comparison with K2O (3.4-4.3) (Na2O/K2O=1-1.4). Diagrams (Figure 9) allow to classify rocks as rhyolites, calc-alkalines, peraluminous and belonging to high K-series.

With respect to the incompatible trace elements of granitoids (Figure 10a-b), clearly it can be seen the spiky pattern and a general enrichment in trace elements 500-10 times higher than the chondrite (except for Ti) and, in a lesser extent, 200-1 times in comparison with the N-MORB. It is noteworthy the high Rb and Ba enrichment, and U in a minor extend. Furthermore, the Nb, Ta and Ti negative anomalies can be seen. REE diagram (Figure 11c) shows that granitoids have a general enrichment in LREE (<60 times) and more flatten behaviour for elements heavier than Tb (>6 times) in comparison with chondrite, therefore LREE>HREE.

Granodioritic to dioritic rocks and rhyodacitic porphyries

Granodioritic to dioritic rocks (CLC-07 and CLC-09) crystallized from sub-alkaline intermediate magmas, with SiO2 55-62.5 % (oversaturated), high values of Al2O3 15-18.8

%, and expected Fe2O3* 5-11.3 %, CaO 4.4-6.9 %, Na2O 3.2-4.4 % and low K2O 1.9-2.5 %. CLC-09 has an anomalous low MgO of 1 %. Rocks were classified as a granodiorites and a diorites, calco-alkaline, metaluminous to peraluminous (CLC-07 is I-type and CLC- 09 close to limit between I-type and S-type), and belonging to high K-series.

On the other hand, CLC-18 is sub-alkaline, calco-alkaline and at the border between metaluminous and peraluminous with Al2O3 16.5 %. It was classified as a rhyodacitic porphyry (SiO2 67.2 %), according to de la Roche (1980) diagram and, at the equivalent diagram for plutonic rocks, correspond to a granodiorite. An-Ab-Or diagram suggest a trodhjemite.

Incompatible trace elements indicates that granodioritic to dioritic rocks and rhyodacitic porphyries have an enrichment 25 and 500 times in Rb and Ba, and 100 in Sr, with 146 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación respect to chondrite. A lesser difference with respect to N-MORB, 10 times in Rb and 80, Ba. Therefore, in a broad sense rocks show a general enrichment in LIL elements in comparison with a depletion in HFS elements.

Moreover, Harker diagrams (Figure 11) show samples have lineal behaviour for all samples in major and minor elements, except for Na2O and K2O. Granitoids (FLC-02 and

FCL-16) can be strongly correlated in all the diagrams, except for Na2O. Granodioritic to dioritic rocks and rhyodacitic porphyries show a lineal behaviour for all oxides, except K2O and Al2O3. Coherently, AFM diagram also shows a common trend. 4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 147

Figure 4-9 Minor and major elements diagrams for granitoids (FLC-02 and FLC-16), granodioritic to dioritic rocks (CLC-07, CLC-09) and rhyodacitic porphyries (CLC-18). a) TAS Diagram; b) K2O vs. SiO2; c) AFM diagram; d) An-Ab-Or Diagram; e) de la Roche et al. (1980) diagram for intrusive rocks; f) de la Roche et al. (1980) diagram for extrusive rocks; g) A/CNK vs. A/NIK diagram of Shand (1927); h) Nb vs. Y diagram. 148 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

Figure 4-10 Spider and REE diagrams for granitoids (FLC-02 and FLC-16), and Spider diagram for granodioritic to dioritic rocks (CLC-07, CLC-09, CLC-10) and rhyodacitic porphyries (CLC-18). a, e) Diagram with respect to the chondrite of Anders & Grevesse (1989); b, f) diagram with respect to the N-MORB of Sun 4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 149

& McDonough (1989), c, g) LIL/HFS diagram with respect to the N-MORB of Sun & McDonough (1989) and d) REE diagram with respect to the chondrite for granitoids. For granodioritic to dioritic rocks and rhyodacites in spider diagrams just Ba, Rb, K, and Sr value must be taken into account. Ta values were measured just for CLC-18; Zr for CLC-07; Nb values are valid for CLC-18 and informative for the two others; Y are informative for the all samples; Ce values are valid for CLC-18, but informative for CLC-07 and CLC-09. Lastly, other elements were lower than limit detection (cf. Table 2).

Figure 4-11 Harker diagrams of granitoids (FLC-02 and FLC-16), granodioritic to dioritic rocks (CLC-07 and CLC-09) and rhyodactic porphyries (CLC-18). For symbols nomenclature see Figure 9.

4.3.3 Pb dating

55 circons of the 2 granitoid samples samples were dated, at the Supplemental Material 6 can be seen the data and dated circons. Ages vary from Mesoproterozoic to Paleocene, with populations in Mesoproterozoic (1387.2 ± 16.3-1011.7 ±34.7 Ma), Neoproterozoic (954.3 ±76.5-633.3 ±7.7 Ma), Permian (294.7 ±5.9-258.4 ±4.6 Ma), Cretaceous (88.6 ± 2.0-71.6 ± 2.0 Ma) and Paleocene (64.3 ± 1.4-58.3 ± 1.2 Ma). Also there are some dispersed single-ages at the Cambrian-Ordovician limit (486.9 ±12.3 Ma), Ordovician- Silurian (446.7 ±10.2 Ma), Devonian (368.2 ±7.6 Ma), Carboniferous (365.9 ±11.8 and 312.9 ±23.5 Ma) and Jurassic (189.4 ±4.5 Ma). Figure 12 shows the concordia diagrams for the two samples. 150 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

Figure 4-12 Concordia diagrams and frequencies histogram of granitoids of samples FLC-02 (a, b, e) and FLC-16 (c, d, f).

Ages show the most significant frequency in Mesoproterozoic and Neoproterozoic, next Permian and, finally, Cretaceous and Paleocene (figures 12e-f).

4.4 Discussion

In the following, it will be discussed the characteristics, age and stratigraphy (emphasis on nomenclature) of granitoids, granodioritic to dioritic rocks and rhyodacitic porphyries. To the end, it will be pointed out the meaning of this contribution to the local geology to La Cristalina Formation. 4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 151

4.4.1 Petrological approaches

Granitoids

Granitoids have a clearly intrusive contact with Ordovician rocks. Porphyritic, lightly porphyritic and minor faneritic textures indicate the rocks crystallized near to the surface, rather than in deep settings. Phenocrysts arrangements are associated with a fluidal magmatic texture more than metamorphic textures. Nevertheless, minor simple shear and deformation structures of FLC-02 are evidences of the low temperature deformation. This deformation may be responsible of the oriented texture due to a minor fault (figures 3a-b, 4e-f and Table 1) that can be seen field near to an anticlinal formed by the Ordovician metasedimentary strata.

There are some critical petrographical observations that require explanation. On one hand, anhedral garnets in FLC-16 are strongly fractured, likely, representing assimilated minerals. On the second hand, quartz aggregates in both samples seem like polycrystalline metamorphic grains. Here is proposed those were included in the magma. On the third hand, the pyroxene euhedral phenocryst in FLC-02 looks like if it would have crystallized from the original magma, and the retrograde corona could account for typical reaction in those kind of rocks.

With respect to geochemical analyses, similarity of FLC-02 and FLC-16 in major, minor and trace elements and, specially, the incompatible elements diagrams clearly supports are genetically related, in addition to the rocks crop out very close. Therefore, samples studied here are grouped as generated by the same processes, except the dynamic metamorphism exclusively of FLC-02. Rocks are classified as rhyolites.

Granitoids are considered as S-type because high SiO2; calc-alkaline behaviour; low values of R2 and high of R1 in de la Roche et al. (1980) diagram; peraluminous character; enrichment in trace elements and REE, high Cr, Ni, Rb, Th and U values; biotite and ilmenite crystals; included highly fractured garnets and metamorphic aggregates; etc. Rocks belong to high-K series, which can be related with the continental signature, whereas A/CNK>1 maybe related with muscovite crystallization. 152 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

The strongly enrichment in trace elements with respect to primitive mantle and chondrites suggests the magma source was already enriched in those elements and/or during the magma generation and the trend to the surface the magma was enriched in those elements. The strong enrichment in Ba and Rb might be associated with micas source.

On the other hand, ilmenite could be explained by low ƒO2 during magma crystallization.

The Nb-Y diagram (Figure 9b) suggests that granitoids are volcanic arc-related (VAG+syn-COLG field), syn-collision granitoids are discharged with Rb-Y+Nb diagram, because the tectonic regimen in which rocks were generated, including no collision during Paleocene (cf. Bayona et al., 2016).

Remains unanswered what are the petrogenetic mechanisms and the petrological meaning of Paleocene S-type granitoids in the eastern flank of the Central Cordillera, considering the regional tectonic reconstructions for Paleocene, because is out of the scope of this work.

With respect to U-Pb datings, Mesoproterozoic to Cretaceous ages are considered here as inherited ages, whereas the youngest Paleocene ones are considered as the crystallization age. 8 populations were grouped, each of them related with a single geological event or a succession of related geological events, as will be discussed.

Mesoproterozoic-Neoproterozoic ages can be associated with the Precambrian paragneisses that underlies La Cristalina Formation coherent with field observations. Those paragneisses have been considered as the southernmost outcrops of San Lucas Gneisses by González (2001), but with more certainty, because proximity and lithology, correspond to those gneisses studied by Ordóñez et al. (1999). Radiometric datings in those paragneisses, performed by Ordoñez et al. (1999) using Rb-Sr, indicate 894 ± 36 Ma isochronic age, that authors considered as the metamorphic age. As well, authors showed TDM= 1829 and 1757 Ma.

Recently, Cuadros et al. (2014) performed a U-Pb LA-ICP-MS datings in San Lucas gneisses, which would have been more meaningful to these correlation, but measured rocks crop out further to the north in the San Lucas Ranges, therefore correlations cannot be confident. Nevertheless, populations around 1400, 1200, 1100 and 900 Ma were reported with a metamorphism during Neoproterozoic, which is very similar to the ages 4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 153 obtained here and opened a stratigraphic question about the relation of the Precambrian paragneisses and the San Lucas gneisses. Those Mesoproterozoic-Neoproterozoic zircons of granitoids could have got into the magma either during the magma ascent through paragneisses or through the overlying Lower-Middle Ordovician La Cristalina Formation or they will be part of the magma source.

Ordovician and Silurian zircons cannot be easily related with any close geological unit in the area, but it seems very interesting considering Martens et al. (2015), Mantilla et al. (2012) and van der Lelij et al. (2016) U-Pb datings of Ordovician igneous rocks in Colombia, the former in the western flank of the Central Cordillera, and the others in the Eastern Cordillera.

Permian and Triassic zircons could have come from many igneous intrusions and orthogneisses, as Permian-Triassic igneous rocks and metamorphism is well constrained in the Central Cordillera to the west of the granitoids. Those igneous intrusions in the Centra Cordillera with or without metamorphism are interpreted as A and S-Granitoids e. g. Spikings et al. (2015). Units dated as Permian-Triassic near to the granitoids are metagranites 10RC41, 10RC42 and 10RC43 of Spikings et al. (2015); Río Verde Granitic Gneiss of Vinasco et al. (2006), and Santa Isabel Gneiss of Restrepo et al. (2011).

Jurassic ages can be related with igneous intrusions studied here as granodioritic to dioritic rocks and rhyolites and andesites. A sample of the Segovia Batholith dated as 163.1 ±2.8 Ma by Leal-Mejía (2011) is very close to the granitoids in El Dorado locality and is very similar to inherited ages obtained here. As well, obtained ages might be related with other close Jurassic igneous bodies, such as those dated by Spikings et al. (2015) and González et al. (2015).

Finally, Cretaceous ages might mainly come from the Antioqueño Batholith, and other Cretaceous rocks outcropping at the same latitude of the granitoids such as La María, Cerro Gramalote and La Floresta localities cf. Leal-Mejía et al. (2011). Ages of the Antioqueño Batholith have been obtained by several methods. By U-Pb LA-ICP-MS means, it dates as early as 93.5 ±1.5 Ma (Villagómez et al. 2011) and as late as 59.2 ±1.2 Ma (Leal-Mejía et al., 2011). To see ages of the Antioqueño Batholith cf. Gómez & Almanza (2015), some references therein are: Leal-Mejía et al., (2011) ages by U-Pb LA- ICP-MS and SHRIMP; Villagómez & Spikings (2013) fission track and Ar-Ar; Ibáñez-Mejía 154 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación et al. (2007) by U-Pb ID-TIMS; Ordóñez & Pimentel (2001) by Rb-Sr, and Pérez (1967), Botero & Feininger (1982) and Botero (1963) by K-Ar.

Lastly, Bayona et al. (2012) dated Paleogene volcanic and plutonic zircons in the northern Andes (Central Cordillera), as well as some sedimentary rocks in the Middle Magdalena Valley and Eastern Cordillera. According to their measurements and together with other published data (including data from Ecuador to Venezuela), authors suggested that a magmatic arc to the northern Andes of ca. 700 km is the responsible of those ages, due to the subduction of Caribbean Plate. Critically, propose a shutdown during Eocene (ca. 45 Ma) due to the thickened, shallow and obliqueness subduction of the Caribbean Plate, as well as the South American Plate movement to the north. The aforementioned might account for the paleotectonic scenario in which granitoids could be generated, that is mainly a subduction.

Granodioritic to dioritic rocks and rhyodacitic porphyries

Textures of granodioritic to dioritic rocks allow to classify them as plutonic, with enough time to crystalize big crystals (apparently, water has nothing to do). Banded textures could indicate a relative calm magmatic chamber. Enclaves could evidence magma mingling as composition is very similar to host rock, contacts are diffuse and grain size is smaller.

CLC-07 and CLC-09 crystallized from intermediate magma, those were classified as granodioritic to dioritic rocks, but it is expected to find other facies such as granitic and quartzdioritic rocks and even gabbros, according to observed in field and to was pointed out in other studies e. g. Feininger et al. (1972) or Leal-Mejía (2011).

Geochemical results indicate that intermediate rocks have a continental signature, with high Al2O3 content, high-K series and enrichment in trace elements, especially LIL. Diorites are typical continental arc related rocks, this tectonic setting have been long proposed for NW South American margin during Jurassic times (e.g. Spikings et al., 2014, Leal-Mejía et al. 2011; Bustamante et al., 2016); therefore, it is likely that these granodioritic to dioritic rocks magmas were generated in a tectonic setting including an on-going subduction and a continental arc. To confirm that, other analyses should be performed to correctly interpret the petrogenetic scenario, such as isotopic measurements. However, Leal-Mejía (2011) performed isotopical measurements in a 4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 155 quartzdiorite near to the studied area (El Dorado) which suggest a mantle source 87 86 ( Sr/ Sr and variable positive ƐNd) with minor continental crust contamination. Leal-Mejía (2011) performed 7 samples LA-MC-ICP-MS U-Pb datings that suggest Middle to Late Jurassic age. Interestingly, U-Pb datings of Leal-Mejía (2011) have few inherited ages, it indicates no assimilation and accounts for the minor crustal contamination.

Geochemical results, specially, Harker diagrams indicate a relation between granodioritic to dioritic rocks and rhyodacitic porphyries and, despite few trace elements measured, both have a very similar concentrations. Nevertheless, the fact we do not have all the trace elements measurements and geochronology or other isotopes, and the fact have different textures make it difficult to correlate granodioritic to dioritic rocks with the rhyodacitic porphyries, as well as no cross-cut relations have been observed neither directly nor indirectly. Only granodioritic to dioritic rocks should be considered as petrogenetically related with certainty and, likely, differentiated by small extend of fractional crystallization, CLC-07 more differentiated than CLC-09. In coherence, rhyodacitic porphyries are considered here as a different unit and petrogenetically different until no more information are available, and here is considered the metamorphism is local (not the same as La Cristalina Formation), in contrast to Feininger et al. (1972).

4.4.2 Stratigraphic nomenclature

There is much work to do with igneous rocks in the southeastern of Antioquia and in the studied area. Stratigraphic nomenclature of igneous rocks is confusing, because there is a lot of geochemical and geochronological information missing, and studies are critical when considering the economic importance of those igneous intrusions as gold-bearing rocks.

Igneous rocks that intruded La Cristalina Formation and the Precambrian paragneisses have been associated with 1) the Cretaceous Antioqueño Batholith by Botero (1940), 2) “La Malena Volcanic Set” and 3) the Jurassic Segovia Batholith by González (2001), Fuquen (2009) and Fonseca (2011). In the following it will be discussed the stratigraphic nomenclature.

Granitoids 156 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

Granitoids cannot be related with certainty to any unit described in the area up-to-now. Rather, it is proposed here that granitoids are a different unit, because the Paleocene age, the geochemical characteristics, the stratigraphic relations and because there is not enough criteria to correlate them with any other. Below, it will be explained why the granitoids cannot be correlated with any other unit.

Firstly, granitoids do not belong to the “d” unit of Feininger et al. (1972) or the granodioritc to dioritic rocks because its texture, composition and age, and because the cited disconformity with overlying Lower Cretaceous rocks observed by Fuquen et al. (2009).

The possible equivalence between the granitoids and “LMVS”, when considering the similar composition and texture, the critical argument to discard the proposal are the cross-cut relations observed in the field: Aphanitic rocks or “LMVS” were intruded by the granodioritic to dioritic rocks, which was also observed by Feininger et al. (1970), who pointed out that the “Volcanic rocks” (or “LMVS”) were intruded by “Igneous rocks mainly to the east of the Otú Fault” that includes “d” unit.

On the other hand, granitoids seems similar to those hypabyssal rocks named “Felsic porphyries to the east of the Otú Fault” by Feininger et al. (1972). This unit was not mapped in La Miquera Creek. Nevertheless, those hypabyssal rocks were checked in field at some tributaries of La Miquera Creek and Las Iglesias Creek and textures are quite different, but composition is similar. Feininger et al. (1972) suggested what he considers the same metamorphic Paleozoic age of La Cristalina Formation for those felsic porphyries because they assumed rocks have the same metamorphism. That assumption and the fact they were not mapped in La Miquera Creek are not a satisfactory arguments to discard that, actually, those are the same unit. Metamorphism of porphyries is not so likely, because textures may be due to petrogenetic processes or dynamic metamorphism rather than due to the regional metamorphic processes that affected La Cristalina. In coherence not deformed porphyries have been found which confirm this hypothesis.

On the other hand, the Antioqueño (40 my span-time of crystallization, 4 pulses and an area of 7221 km2 of Leal-Mejía, 2011) and Sonsón batholiths (1100 km2 cf. Leal-Mejía, 2011) outcrop in the Central Cordillera and are the nearest batholiths to the granitoids. The second does not show similar characteristics to the granitoids according to Leal- Mejía (2011) data. Nevertheless, to the former have been associated many satellite 4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 157 stocks, of which the Caracolí Stock is the nearest to the granitoids studied here, ca. 15 km. The Caracolí Stock is petrographically and geochemically (quartz-dioritic rocks) different than the studied rocks, but share strong similar characteristics of age. The stock returned a U-Pb LA-MC-ICP-MS crystallization age of 60.1 ±1.2 Ma and have inherited Cretaceous (84-80 and 78-75 Ma) and Neoproterozoic (900 Ma) ages. Therefore, a petrogenetic relation might be considered between the Caracolí Stock and the granitoids.

Due to all discussed above, the granitoids are a different unit, but similar to “Felsic porphyries to east of the Otú Fault”. Those rocks allow to make clear the local geological evolution of the local area and have a geological importance because are S-type granitoids. Those rocks must not be formalized with a proper geographic name because are too small to be mapped at 1:100 000 scale, thus is not recommended to use any the term for granitoids until relations with other bodies will be disclosed, above all with the unit “Felsic porphyries to the east of the Otú Fault” and some Paleocene and Cretaceous igneous rocks outcropping in the Central Cordillera, such as Caracolí Stock, and to light of the magmatic arc and volcanic activity proposed by Bayona et al. (2012).

Granitoids can be defined as Paleocene S-type granitoids with porphyritic, light porphiritic to minor faneritic textures, mainly light grey colour and felsic rocks that intruded La Cristalina Formation in La Miquera Creek, very often along foliation planes and usually of <100 m of thickness.

Granodioritic to dioritic rocks and rhyodacitic porphyries

From the stratigraphic point of view, data from Leal-Mejía (2011) reinforced that the Segovia Batholith can be considered as a single stratigraphic unit from Segovia town (to the north) until El Dorado locality (to the south), which is the nearest locality to the studied area here, but to the west of the Palestina and Otú-Pericos faults.

Granodioritic to dioritic rocks studied here are, likely, associated with the Segovia Batholith, according to strong similarities with field, petrographic and geochemical characteristics. On the other hand, U-Pb datings are being performed at the Rio de Janeiro University, but there are not available data yet. Therefore, if U-Pb are coherent with ages for the Segovia Batholith, the term Segovia Batholith must be used for granodioritic to dioritic rocks and quartzdioritic rocks that intruded La Cristalina Formation, 158 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación and other names must be avoided. But, currently, is recommended to name those rocks as granodioritic to dioritic rocks.

With respect to the rhyodacitic porphyries, they look very similar to the “Felsic Porphyries to the east of the Otú Fault” (Feininger et al., 1970), hence the sample studied here is recommended to be provisionally considered as a part of that map unit. This proposal is supported by the hand-sample and thin-section descriptions, as well as the close proximity outcrops (Figure 2). Remains unknown, if all porphyries that intruded La Cristalina Formation can be actually be grouped in a single unit (do those belong to the same petrogenetic event?), or if those belong to another igneous units (Segovia Batholith or “Felsic rocks to the East of the Otú Fault”?) or if those rather should be considered different units and deserves another name. As well, it remains unclear the petrogenetic characteristics and the economic importance of those porphyries.

4.4.3 Critical aspects in relation with La Cristalina Formation

On the first hand, the intrusive contact with the granodioritic to dioritic rocks allows to conclude that La Cristalina Formation low grade metamorphism occurred earlier than the crystallization age of the gradioritic to dioritic rocks (Middle to Upper Jurassic if correspond to the Segovia Batholith) and after Middle Ordovician. On the second hand, likely, during Middle Jurassic Ordovician rocks were deep enough to allow the crystallization of a plutonic granodioritic to dioritic rocks; on the contrary, during Paleocene Ordovician rocks were shallow enough to crystallize porphyritic S-type granitoids.

Those igneous intrusions caused contact metamorphism in La Cristalina Formation, evidences are found in Las Iglesias Creek and some tributaries of La Miquera Creek (Figure 14). Las Iglesias white marbles have been formed from dark grey metamicrites, as well some andalusite porphyroblasts and red coarser muscovites have been re- crystallized in metamudstones. Whereas in La Miquera, coarser (1-2 mm sized) red biotites and white mica have been re-crystallized. Fonseca et al. (2011) also observed andalusite porfiroblasts due to contact metamorphism at the outcrops of the road Puerto Berrío-Medellín, and Fuquen et al. (2009) reported epidote and diopside. 4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 159

Figure 4-13 Contact metamorphism of La Cristalina Formation caused by igneous intrusions in Las Iglesias Creek and in one tributary of La Miquera Creek. a) Outcrop of marbles with green alteration minerals; b-c) light grey marbles that retain plane-parallel and wavy lamination formed from metamicrites and calcareous metasanstones; d) andalusite porphyroblasts in metamudstones, and e) coarser white mica re-crystallized in metamudstones, note pinky colours due to red biotites.

4.5 Conclusions

It was proposed that at least 3 different igneous rocks intruded La Cristalina Formation: granodioritic to dioritic rocks, rhyodacitic porphyries and S-type granitoids. Granitoids petrographic, geochemical and geochronological data indicate that correspond to Paleocene S-granitoids. Most of the inhered zircons ages can be associated to rock bodies surrounding the granitoids. With respect to the granodioritic to dioritic rocks can be associated with continental active margins, as is expected during Jurassic-time to the northwestern of Southamerican Andes, and could be associated with Middle to Upper Jurassic plutonic Segovia Batholith, U-Pb and isotopes measurements are missing in the granodioritic to dioritic rocks to confirm it. 160 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

Rhyodacitic porphyries might belong to the Feininger et al. (1970)´s “Felsic porphyries to the east of the Otú Fault”, but remains unknown the petrogenetic characteristics and the relation with other local igneous bodies.

It seems natural that as more detailed data are available and, above all, better cartographical and petrological studies of the local igneous rocks will be done, a better understanding of igneous rocks of the southeastern of Antioquia can be achieved, as well as the nomenclature could be meaningful, clear and correct.

Acknowledgments

I am grateful with GMAS Laboratories to support the zircons separation and thin section preparation. Thanks to the Facultad de Ciencias of the Universidad Nacional de Colombia (UN) for the Honor Degree Scholarship; to the Departmento de Bienestar of the UN for the partial-financial support during the academic exchange to the Johannes Gutenberg Universität (Germany), where valuable discussions improved this study, and to the Departamento de Geociencias of the UN for supporting some geochemical analyses. Lastly, I am grateful with the today´s geologists Francisco Javier Muñoz, Luis Miguel Vélez and Andrés Felipe Alvarado for their valuable help during field works.

4.6 References

Álvarez, J.A., 1983, Geología de la Cordillera Central y el occidente colombiano y petroquímica de los intrusivos granitoides meso-cenozoicos. Ingeominas, Boletín Geológico, 26(2):1-175. Bayona, G., Cardona, A., Jaramillo, C., Mora, a., Montes, C., Valencia, V., Ayala, C., Montenegro, O., Ibañez- Mejía, M., 2012. Early Paleogene magmatism in the northern Andes: Insights on the effects of Oceanic Plateau–continent convergence. Earth and Planetary Science Letters, 331-332: 97–111. Botero-Arango, G., 1940. Sobre el ordoviciano de Antioquia. VII congreso científico suramericano. Washington, Estados Unidos de América. Botero, G., 1941. Formaciones geológicas de Antioquia. Minería. Sección técnica. Conferencia en el Paraninfo de la Universidad de Antioquia. Medellín, Antioquia. Botero, G., 1963. Contribución al conocimiento de la zona central de Antioquia. Universidad Nacional de Colombia. Anales Facultad de Minas, 57:1–101 p. Medellín. Bustamante, C., Archanjo, C.J., Cardona, A., Vervoort, J.D. 2016. Late Jurassic to Early Cretaceous plutonism in the Colombian Andes: A record of long-term arc maturity. GSA Bulletin,128, 11-12, 1762-1779. DOI: 10.1130/B31307.1 http://www.accefyn.org.co/cientificos/pdf/07.Contribucion_Conocimiento.pdf Cuadros, F.A., Botelho, N.F., Ordóñez, O., Matteini, M., 2014. Mesoproterozoic crust in the San Lucas Range (Colombia): An insight into the crustal evolution of the northern Andes. Precambrian Research, 245, 186–206. DOI: http://dx.doi.org/10.1016/j.precamres.2014.02.010 Feininger, T., Barrero, D., Castro, N., Ramírez, O., Lozano, H., Vesga, J., 1970. Mapa Geológico del Oriente del Departamento de Antioquia, Colombia. Cuadrángulo I-9, y partes de los cuadrángulos H-9, H-10, I-10, J-9 y J-10. Instituto de Investigaciones Geológico Mineras-United States of America Geological Survey. Scale 1:100 000, Bogotá, Colombia Feininger, T., Barrero, D., Castro, N., 1972. Geología de parte de los departamentos de Antioquia y Caldas (subzona II-B). Boletín Geológico. XX(2). Instituto Nacional de investigaciones Geológico-Mineras (Ingeominas). Bogotá, Colombia. Feininger, T., Barrero, D., Castro, N., Ramírez, O., Lozano, H., Vesga, J., Hall, R.B., 1973. Geology and mineral deposits of an area in the departments of Antioquia and Caldas (Subzone IIB), Colombia, Project Report Colombia investigations (IR) CO-24. US Geological Survey. Feininger, T., Botero, G., 1982. The Antioquian Batholith, Colombia. INGEOMINAS. Publicaciones Geológicas Especiales del INGEOMINAS, (12): 1–150. Bogotá, Colombia. 4. Rhyolitic to andesitic rocks, granodioritic to dioritic rocks, rhyodacitic … 161

Fettes, D., Desmons J., 2007. Metamorphic rocks: A classification and glossary of terms. Recommendations of the International Union of Geological Sciences Subcomission on the systematics of Metamorphic Rocks (SCMR). Editores: Fettes Douglas and Desmons Jacqueline Cambridge University Press. 244p. United Kingdom. Fonseca, H.A., Fuquen, J.A., Mesa, L.D., Talero, C.A., Pérez, O.G., Porras, J.J., Gavidia, O., Pacheco, S.M., Pérez, J.F., Amaya, E., García, Y., Farfán, E., 2011. Cartografía geológica de la Plancha 133 Puerto Berrio. Universidad Pedagógica y Tecnológica-Servicio Geológico Colombiano, Sogamoso, Colombia, Scale 1:100 000, 1 sheet. Fuquen, J.A., Gómez, L.A., Quintero, C., Patiño, A., Beltrán, A., López, C., Lancheros, J. A., Renzoni, G., Manrique, M., 2009. Cartografía geológica y muestreo geoquímico escala 1:100.000 de la Plancha 149 Puerto Serviez Valle Medio del Magdalena. Scale 1:100 000, Servicio Geológico Colombiano, Bogotá, Colombia, 1 sheet. GRP., 2008. Geología de la plancha 149 Puerto Serviez. Escala 1:100 000. Servicio Geológico Colombiano. Bogotá, Colombia. Gómez, J., Almanza, M.F., editors, 2015. Compilando la geología de Colombia: Una visión a 2015. Servicio Geológico Colombiano, 429p., Bogotá, Colombia. González, H., 2003. Memoria explicativa de las planchas 129 Cañas Gordas y 145 Urrao . Ingeominas. At 1:100 000 scale, Bogotá, Colombia González- Iregui, H., Maya, M., Tabares, L.F., Montoya, A., Palacio, A.F., Sánchez, C., Barajas, A., Vélez Giraldo, W. 2015. Memoria de la plancha 118-San Francisco, Scale 1:100 000, Servicio Geológico Colombiano, Bogotá, Colombia, 1 sheet. Ibáñez-Mejía, M., Tassinari, C.C.G., Jaramillo, J.M., 2007. U–Pb zircon ages of the “Antioquian Batholith”: Geochronological constraints of late Cretaceous magmatism in the central Andes of Colombia. XI Congreso Colombiano de Geología. Memorias CD ROM, 11 p. Bucaramanga. Leal-Mejía, H., 2011. Phanerozoic gold metallogeny in the Colombian Andes: A tectono-magmatic approach. PhD. Theses, 989p. Universitat de Barcelona. Barcelona, Spain. Le Maitre, R. W., editor, 2002. Igneous rocks: A classification and glossary of terms. Recommendations of the International Subcommission on the systematics of Igneous Rocks. 2nd Edition. Cambridge University Press. 367p. United Kingdom. Ordóñez-Carmona, O., Pimentel, M.M., 2001. Consideraciones geocronológicas e isotópicas del Batolito Antioqueño. Revista de la Academia Colombiana de Ciencias Exactas, Físicas y Naturales, 25(94): 27–35. Bogotá. URL: http://www.accefyn.org.co/revista/vol_25.htm Ordoñez-Carmona, O., Pimientel, M.M., de Moraes, R., Restrepo, J.J., 1999. Rocas grenvilianas en la región de Puerto Berrío-Antioquia, Revista de la Academia de Ciencias, 23(87), 225-232, Bogotá, Colombia. Ordoñez, O., Restrepo, J. J., Pimentel, M.M., 2006. Geochronological and isotopical review of pre-Devonian crustal basement of the Colombian Andes. Journal of South American Earth Sciences. 21. Passchier, Cees W., Trouw, Rudolph A. J., 2005. Microtectonics. Springer. 2nd edition. 366p. Germany. Restrepo-Pace, P.A., Cediel F., 2010. Northern South America basement tectonics and implications for paleocontinental reconstructions of the Americas. Journal of South American Earth Sciences. 29(4): 764–771. Restrepo, J.J., Ordoñez, O., Armstrong, R., Pimentel M.M. 2011. Triassic metamorphism in the northern part of the Tahamí Terrane of the central cordillera of Colombia. Journal of South American Earth Sciences. 32. 497-507. DOI: 10.1016/j.jsames.2011.04.009. UPTC., 2012. Geología de la plancha 133 Puerto Berrío. Servicio Geológico Colombiano. Bogotá, Colombia. van der Lelij, R., Spikings, R., Ulianov, A., Chiaradia, M., Mora, A. 2016. Palaeozoic to Early Jurassic history of the northwestern corner of Gondwana, and implications for the evolution of the Iapetus, Rheic and Pacific Oceans. Gondwana Research, 31, 271-294. DOI: 10.1016/j.gr.2015.01.011 Villagómez, D., Spikings, R., Magna, T., Kammer, A., Winkler, W., Beltrán, A. 2011. Geochronology, geochemistry and tectonic evolution of the Western and Central cordilleras of Colombia. Lithos, 125(3–4): 875–896. URL: http://www.sciencedirect.com/science/article/pii/S0024493711001319 Villagómez, D., Spikings, R., 2013. Thermochronology and tectonics of the Central and Western cordilleras of Colombia: Early Cretaceous–Tertiary evolution of the northern Andes. Lithos, 160–161(0): 228–249. URL: http://www.sciencedirect.com/science/article/pii/S0024493712004999

5. Conclusions

—La Cristalina Formation is a very useful stratigraphic unit when considering the paleography of Gondwana and the tectonic location and its deformation meaning for the understanding of the tectonic processes that have occurred since Ordovician times.

—La Cristalina Formation is a polimetamorphic and low grade metamorphic unit that preserves its marine sedimentary characteristics and therefore was studied as a sedimentary unit.

—La Cristalina Formation was classified as lithostratigraphic unit with a formation rank, because tradition and fulfill all the recommendations of the ICS. Here was not recommended to split the unit, because usefulness in regional geologic understanding of the area, tradition and homogeneous lithological characteristics (metamorphism).

—The name “La Cristalina Formation” was suggested because tradition as is a well stablished name (used 72 years ago) and because of fulfil all the requeriments Chapter 3.B.3 and Chapter 5.F of the Guide.

—La Cristalina Formation overlies Precambrian paragneisses with observed faulted contacts and an unconformities. On the other hand La Cristalina Formation is intruded by the 1) granodioritic and dioritic rocks, 2) rhyodacitic porphyries and 3) some S-type granitoids. Lastly, La Cristalina is overlied by rhyolites and andesites, likely by either an unconformity or a fault; by Aptian-Albian marine rocks (bearing ammonites) according to Fuquen et al. (2009), and alluvial Cenozoic sequences with unconformable contacts.

—I was suggested that at least 4 different facies and facies association compose La Cristalina Formation: 1) metamudstones, 2) siliciclastic intercalations, 3) metamicrites and 4) calcareous intercalations.

164 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

—Facies analyses indicate the base of the Ordovician rocks correspond to a transgression that reached the off-shore settings and the top of the unit corresponds to shoreface settings, therefore the unit seems is a completely marine sequence.

—La Cristalina Formation has a Floian to Middle Darriwillian age according to the 7 occurrences published up-to-now, out of which the graptolite assemblage Didymograptus cf. murchisoni (Beck), Pseudamplexograptus latus (Bulman) and Glossograptus hincksii (Hopkinson) in adittion to phyllocarids remains are early middle Darriwillian in age. This assemblage was first reported here. This is the best age-resolution ever suggested to La Cristalina Formation.

—The first Ordovician foraminifera in Colombia and the second occurrence of South America were reported here. This occurrence has international interest. Fossils were determined as Astrorhiza? sp.

—The succession was considered as polymetamorphic, with a main regional low metamorphic grade, evidenced by foliation, mineral assemblage including biotite, besides textural, petrographic and field observations. On the other hand, the unit has a local contact metamorphism that forms white marbles (with granofelsic textures), and re- crystallization of andalusite porphyroblasts and coarser muscovite in metamudstones. Finally, the latest metamorphism corresponds to local dislocation.

—La Cristalina Formation was correlated with El Hígado Formation, 460 km to the south in the Upper Magdalena Valley, because both have at least part of the same stratigraphic position and similar lithology. Both units have mudstones bearing a Didymograptus murchisonii assemblage.

—Granodioritic to dioritic rocks that intrudued La Cristalina were related to the Middle to Upper Jurassic Segovia Batholith, whereas age-undetermined rhyodacitic porphyries can be related to “Hypabyssal felsic rocks to the east of the Otú Fault” (Feininger et al. 1970). Finally, the Paleocene granitoids were classified as S-type and could not be related with any other unit, but its U-Pb inherited ages were correlationed with many units in the Central Cordillera of Colombia. Conclusions 165

—Igneous rocks allowed concluding that the low grade regional metamorphism of La Cristalina Formation occurred before Middle Jurassic, that during Paleocene times La Cristalina was shallow enough to permit hypabbysal granitoids to crystallize, and that the granodioritic to dioritic rocks are the responsible of the most important contact metamorphism of La Cristalina Formation.

166 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) Título de la tesis o trabajo de investigación

6. Future researching opportunities

1. Mapping at scales 1:25 000 or 1:10 000 of the hole unit can improve many issues (especially structural and succession issues) 2. Improving the model of La Cristalina by using sub-surface information such as wells and high resolution seismic imagery can help to e.g. determine the complete succession, to know more about the nature of the contacts with adjacent units, etc. 3. Carring out petrogenesys studies, both metamorphic and sedimentary, are missing and could help to understand the roll of La Cristalina Formation in ptetrolleum systems and in calcareous minery. 4. Gechronological and thermochronological studies can help to determine provenance analyses, age-calibration (betonites?), numerical ages (sedimentary/metamorphic), uplifting ages, etc. 5. It seems of regional tectonic importance to prove the geological history similitude between La Cristalina Formation and other Colombian units such as El Hígado and Venado formations; La Uribe outcrops; Güejar Group; Ordovician sedimentary register in the Llanos Basin; Silgará Formation, Quetame Complex, Cajamarca Complex, as well as other units which could include Ordovician ages. 6. Finally, throught evaluating the formalization of some beds of geological interest some stratigraphical issues can be solved and make easy the mapping work (e.g. metasanstones beds both in siliciclastica intercalations and metamudstones facies; green metamudstones in metamicrites facies)

A. Supplemental Material 1: Stops, hand-samples and lineaments maps

SM_A_Figure 1 Stops Map of La Cristalina Formation. Legend can be seen in Figure 1 of the Introduction.

168 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

SM_A_Figure 2 Hand-Samples Map of La Cristalina Formation. Legend can be seen in Figure 1 of the Introduction. Supplemental Material 169

SM_A_Figure 3 Lineaments Map of La Cristalina Formation. Legend can be seen in Figure 1 of the Introduction. 170 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

B. Supplemental Material 2: Petrography Metasedimentary rocks. For paragneisses petrography see Supplemental Material 4 Supplemental Material 171

172 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Supplemental Material 173

174 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

Igneous rocks

Supplemental Material 175

C. Supplemental Material 3: X Ray Difraction

SM3_Figure 1 Selected measurements of X Ray Difraction. a) Metamudstones facies, b) metasandstone of metamudstones facies, c) metasandstone of the siliciclastic intercalations facies association, d) siliciclastic intercalations facies association, e) siliciclastic intercalations facies association, f) siliciclastic intercalations facies association, g) siliciclastic intercalations facies association, h) deformed metamudstones facies, i) deformed metamudstones facies, j) calcareous intercalations facies association and k) metamicrites facies. a

b

c

176 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) d

e

f

Supplemental Material 177 g

h

i

178 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia) j

k

Supplemental Material 179

D. Supplemental Material 4: Precambrian paragneisses

SM4_Figure 1. Likely a faulted contact between Precambrian paragneisses and La Cristalina Formation. It was not comproved satisfactorily because we were not shure the lighter unit corresponds to the Precambrian paragneisses.

SM4_Table 1 Petrography of Precambrian paragneisses showing evidences of peak metamorphic conditions at amphibolite facies, but greenschist facies retrograde metamorphism 180 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

E. Supplemental Material 5: Bentonites

SM5_Figure 1 Outcrops of which could be a bentonite. a) Siliciclastic intercalation facies of La Cristalina Formation in La Miquera Creek and b) bed of yellowish metamudstone that could be a bentonite.

SM4_Figure 2 X Ray Diffraction of the possible bentonite

SM5_Table 1 X Ray Fluorescence of the possible bentonite.

F. Supplemental Material 6: Gechrological data

SM6_Figure 14 Dating points in the measured circons

182 Stratigraphy of the Ordovician La Cristalina Formation, Puerto Berrío (Colombia)

SM6_Table 6-2 Geochronological data

Bibliografía 183

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