Aswien Dwarkasing: BTA/GE/12-14 Joëlla Lie-A-Fat : BTA/GE/12-15

Identification of the members of the Formation in Valkenburg, the July 2012

II

Title : Identification of the members of the Maastricht Formation in Valkenburg, the Netherlands.

Author(s) : Aswien Dwarkasing Joëlla Lie-A-Fat

Date : July 2012 Supervisor(s) : Dr.ir. D.J.M. Ngan-Tillard Ir. Ad Verweij TA Report number : BTA/GE/12-14 BTA/GE/12-15

Postal Address : Section for Geoscience and Engineering Department of Applied Earth Sciences Delft University of Technology P.O. Box 5028 The Netherlands Telephone : (31) 15 2781328 (secretary) Telefax : (31) 15 2781189

Copyright ©2012 Section for Geosciences and Engineering

All rights reserved. No parts of this publication may be reproduced, Stored in a retrieval system, or transmitted, In any form or by any means, electronic, Mechanical, photocopying, recording, or otherwise, Without the prior written permission of the Section for Geosciences and Engineering

III

Abstract

In the city of Valkenburg a new underground parking garage is being built next to the Hema. For this project four boreholes were drilled in the . These cores were described and tested at the laboratory of the department of Geoscience and Engineering of Delft University of Technology to obtain the geotechnical properties of the limestone that are relevant to the car park construction. In this thesis, the cores are analyzed to obtain information about the local (structural) geology. This geological information is necessary to determine in which member of the Maastrichtian limestone the car park will be build and if there are faults in this area that can influence the project. The Maastricht Formation is divided into six members, each having its own characteristics. To determine from which member of the Maastricht Formation the cores are, data from various sources has been interpreted and integrated. The geotechnical description and testing of the cores made by TU Delft have been used. Gamma-ray logs have been recorded (by others) in three of the boreholes made for the car park project. They have been segmented, by the authors of this report, in the hope to determine boundaries between the different members. Also XRF analyses for the mineral content; analyses of fossil remains, limestone color and cherts have been conducted. Their results have been correlated with information found in the literature for each member.

The following conclusions have been drawn. Very few macro-fossils have been found in the cores. From this information, the presence of members known for their high content in fossils is excluded, so this conclusion confirms that the cores are not drilled in the Meerssen member. The specific characteristics of the cherts confirmed the occurrence of some members of the Maastricht Formation in the Valkenburg cores. The pipe shaped cherts confirmed the Emael member, and the brown grey cherts confirmed the Gronsveld or the Valkenburg. From the XRF results the percentages of silica was less than 15% for the deepest samples taken in the core linings and according to literature the Valkenburg member has a silica content of approximately 15%, confirming that the Valkenburg member is not reached. The XRF analysis gave unexpected results. Some limestone cores were found to contain gypsum and/or have a silica content higher than what has been reported in the literature. The patterns observed on the gamma logs could not be explained by the XRF results. They are not well understood. Some could be observed in two boreholes and not in the third one. The authors concluded that the cores have been drilled in the Emael to the Gronsveld member. They did not reject the possibility that the members of the Maastrichtian found in Valkenburg do not have the same characteristics as the members found elsewhere in , for example, Maastricht.

IV

During the interpretation of the provided gamma ray logs, some difficulties were encountered. The XRF results stated that the high gamma ray peaks are not caused by higher potassium contents, which is often expected. If higher potassium contents are excluded, the expectation is that the peaks are due to the presence of organic matter, but this was not confirmed by the XRF either. Because of variations in the gamma ray logs and the core descriptions, it is difficult to reject the presence of any small fault intersecting the future car park. Note that the observed variations could well be due to local variations in the sedimentation conditions.

V

Preface In Valkenburg, in the province Limburg, Hurks Vastgoedontwikkeling and the Community of Valkenburg aan de Geul, signed a contract for the realization of the new shopping center in the city. For this project, shops, houses and an underground car park will be built. As no much information is known about the subsurface of Valkenburg's town centre, a site investigation was designed. Four cores were drilled in the center of Valkenburg and brought to the TU Delft for geotechnical testing. The authors of this thesis, Aswien Dwarkasing and Joëlla Lie-A-Fat, BSc students of the Department of Geoscience and Engineering TU Delft were asked to segment the cores in terms of geological members of the Maastricht Formation. Their work has been carried out under the supervision of Dr.ir. D.J.M. Ngan-Tillard. Ir. Ad Verweij from Deltares kindly accepted to co-examine this thesis. Ad is also involved in the site investigation of the project as consultant. The authors of this thesis are thankful to everyone who contributed to the realization of this project. Dominique Ngan-Tillard, who gave us the opportunity to participate in this project and supervised the research. Ad Verweij and Lieven Spits, employees at Deltares, for sharing data recorded by authors. Special thanks to Ad Verweij for co-examining this BSc thesis. Arno Mulder, employee at the TU Delft, who helped throughout the project with the preparation of samples and laboratory testing. Hans Huisman and Bertil van Os, employees at the Cultural Heritage Agency in Amersfoort, who allowed us to use their XRF device and macroscope, and helped with the processing of the XRF data. Ron Penners, employee at TU Delft, who accepted to test the new XRF device available at the Faculty of Civil Engineering and Geosciences on the Valkenburg limestone. Paul Kisters, geologist at the Natuurhistorisch Museum Maastricht, for teaching us how to log Maastrichtian cores in geological terms. John de Jagt, paleontologist at the Natuurhistorisch Museum Maastricht, for identifying fossils retrieved from the cores. Bjorn Vink, employee at Grontmij, for arranging for a tour of outcrops made in Maastrichtian through Valkenburg and Oud Valkenburg and for helping in the identification of the cherts of the different members of the Maastrichtian. Maaike van Tooren, employee at the TU Delft, who helped with the identification of the minerals visible in the pictures taken with the camera from the macroscope of the Cultural Heritage Agency in Maastricht. Joost van Meel, employee at the TU Delft, for helping with microstructural observations with the Leica 3D microscope at the TU Delft. The authors of this thesis appreciated working on a project where a better understanding of the subsurface could only be obtained by combining the expertise of several types of geoscientists.

Hopefully this thesis reveals new information about the geology of Valkenburg!

Aswien Dwarkasing Joëlla Lie-A-Fat

Table of Contents Abstract ...... III Preface ...... V Table of Contents ...... 1 Introduction ...... 1 Chapter 1: Geological history ...... 4 Chapter 2: Approach and methods ...... 8 Section 2.1: The UCS test and the needle penetration test...... 8 2.1.1: The UCS test ...... 8 2.1.2: The needle penetration test ...... 9 Section 2.2: gamma ray...... 10 Section 2.3: XRF-analysis ...... 10 Section 2.4: macroscopy ...... 15 Section 2.5: chert ...... 16 Section 2.6: fossils ...... 18 Chapter 3: Results and interpretation ...... 21 Section 3.1: UCS and needle penetration test results and interpretation ...... 21 3.1.1: The UCS test results ...... 21 3.1.2: The needle penetration test results ...... 22 Section 3.2: gamma ray, results and interpretation ...... 24 3.2.1: gamma ray, interpretation of results ...... 24 Section 3.3: XRF results and interpretation ...... 27 Section 3.4: macroscopy ...... 32 Section 3.5: cherts...... 33 3.5.1: MB-01 ...... 33 3.5.2: MB-02 ...... 34 3.5.3: MB-03 ...... 36 3.5.4: MB-04 ...... 37 Section 3.6: Fossils ...... 39 Chapter 4: Correlation of gamma ray logs with other results ...... 42 Conclusions and recommendations ...... 46 References ...... 48 Appendix ...... 49

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Introduction Authors: Joëlla Lie-A-Fat Aswien Dwarkasing

Context of the research Hurks Vastgoedontwikkeling Zuid bv is building a new underground car park in the center of Valkenburg, the Netherlands, with Deltares as consultant. The floor of the building pit will be at approximately 10 m below the ground surface (Verweij, pers. com., 2012). Around this level, the interface between the gravels of the Houtem Formation and the Maastrichtian limestones is expected. Little is known about the limestones present in Valkenburg’s subsurface. Valkenburg lies at the transition between the Maastrichtian and Kunrader facies of the Maastricht Formation at about 1.5 km from two faults: the Schin op Geul fault and the Klauwpijp (see Figure 1). Only part of the limestone sequence is visible in outcrops and mines in Valkenburg and at its vicinity. Rotary core drilling boreholes were drilled for a viaduct project about 30 years ago (Spits, pers. com., 2012). The viaduct is located at a distance of 2.1 km from the future car park1 (Spits, pers. com., 2012). Variation in the subsurface between both projects cannot be excluded. Therefore, a thorough site investigation was needed for the construction of the car park to limit geo-hazards related to the limestones. Four boreholes have been drilled through the limestone: MB-01, MB-02, MB-03 and MB-04. The limestone cores have been drilled from around 8 to 26 meters below the ground surface. MB-01 and MB-02 have been partly drilled by pulse boring and partly by rotary core drilling. MB-03 and MB-04 have been drilled by rotary core drilling. MB-01 has a poor core recovery. Part of the material has been provided in buckets. The cores have been brought to the laboratory of the Department of Geoscience and Engineering of Delft University of Technology for logging and geotechnical description. The borehole cores have been characterized from a geotechnical point of view. Information on the material type and strength, degree of fracturing, and chert fractions can be found in Ngan-Tillard & Mulder, 2012. Even if the four boreholes have not encountered a fault, it is possible that a fault intersects the project. A fault would increase the complexity of the project as it is likely to be associated to weaker and weathered limestone, possibly carbonate sands and have a high permeability susceptible to increase water ingress into the building pit.

Goal of the research The goal of this thesis is to use geological knowledge to reject the assumption according to which a fault intersects the project. The Maastricht Formation consists of six members (see Figure 3). Each member has characteristic limestone colors, fossil types and cherts. If the members can be tracked in the cores and no vertical shift between the members is identified in the different boreholes, one can reject with confidence the assumption that a fault is present at the location of the future car park.

1 https://maps.google.com/maps?ll=50.873541,5.8163701&z=16&t=h&hl=en

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Methodology Deltares allowed the authors of this thesis, Aswien Dwarkasing and Joëlla Lie-A-Fat, BSc students of the Department of Geoscience and Engineering to investigate the geological origin of the cores. Deltares kindly accepted that data gathered by other parties for their client, Hurks Vastgoedontwikkeling Zuid bv are used for this thesis under one condition: the results obtained by others must remain strictly confidential.

The authors of this thesis used different methods to reach their goal, as explained below.

First, a literature study has been conducted to learn more about the geological history from Valkenburg. Outcrops have been selected and visited with Bjorn Vink (Projectbureau A2 Maastricht) as a guide in Valkenburg and Oud-Valkenburg to better appreciate the in situ characteristics of some members of the Maastrichtian limestone.

Second, as limestones of the older members are expected to be stronger and stiffer than the younger limestones, the results of the factual geotechnical report produced by Ngan-Tillard and Mulder (2012) have been interpreted to detect the transition to stronger rocks.

Third, gamma rays recorded by others in boreholes MB-02, MB-03 and MB-04 have been segmented based on pattern recognition and correlated to each other in the hope to distinguish the different members.

Fourth, according to literature (Felder & Bosch 2000, p.131), one expects a higher silica content in the Valkenburg member. Limestones of the Younger members contain at least 95% calcium carbonate. Based on the gamma rays, and the borehole logs, samples were chosen. Their mineralogy was examined using the XRF equipment of the Cultural Heritage Agency in Amersfoort and interpreted with the help of Hans Huisman and Bertil van Os. Some results have been double-checked at TU Delft with the help of Ron Penners.

Fifth, the cores have been examined by Paul Kisters, geologist of Maastricht Natural History Museum. Paul mainly focused on fossils and cherts characteristics to identify members of the Maastricht formation in the cores. The authors of this thesis assisted Paul in his survey.

Sixth, the authors of this thesis have further characterized the shape and color of the cherts and extracted manually all cherts from the upper limestone cores to determine with accuracy the chert content per core lining. The chert content is known to vary from one member to another.

In this thesis, first the geology of the Maastrichtian is explained. Then, methods are described (Chapter 2). Then, results obtained with each method are presented and interpreted in Chapter 3. These results are being integrated in Chapter 4. Conclusions and recommendations are given at the end of this thesis.

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Figure 1: geological overview of Zuid-Limburg. Note the location of Valkenburg at proximity to various geological formations and facies and two two faults: the Klauwpijp and Schin op Geul fault2

2 From “Krijt van Zuid-Limburg”, p.12

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Chapter 1: Geological history Authors: Joella Lie-A-Fat Aswien Dwarkasing

In this chapter the development of the Maastricht Formation is briefly explained. The Maastricht Formation was deposited in the era of the geological scale. The Maastricht Formation is on top of the Gulpen Formation. It was formed in a shallow marine environment under a tropical climate. The tropical climate had a positive effect on sea life. Fossils can be found in the Maastricht Formation. After the Gulpen Formation was eroded by uplift of the area, sedimentation of the Maastricht Formation started. The age interval of the Maastricht Formation is 65 to 99 million years (Ma). Its thickness is according to literature (Felder &Bosch, 2000) approximately 45 meters.

The Maastricht Formation (Figure 3) is divided into six members, which are the following, from old to young: the Valkenburg, Gronsveld, Schiepersberg, Emael, Nekum and Meerssen members. The Maastricht Formation has two main facies, in the eastern part the facies of the Kunrader limestone and in the western part, the facies of the Maastrichtian limestone. These facies are shown in Figure 2.

Figure 2: schematic view of the Kunrader facies in the Maastricht Formation3

These two facies can be distinguished based on their color, mineral content, grain size, distribution of cherts and strength. The Kunrader limestone is characterized by alternating strong and soft limestone layers which are light- grey colored (Felder & Bosch 2000, p.71). The Maastrichtian limestone is yellow white. It is a fine to coarse grained limestone which is predominantly very weak to weak (Felder & Bosch

3 From “Krijt van Zuid-Limburg”, p. 73

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2000, p.71). It can contain (proto)cherts ( Felder & Bosch 2000, p.72-74). Proto-cherts are not completely developed cherts. The members in the Maastricht Formation are separated by hardgrounds which are called ‘’horizons’’. In the upper part, the Vroenhoven Horizon separates the Houtem Formation and the Maastricht Formation. The lower boundary between the Maastricht Formation and the Gulpen Formation is formed by the Lichtenberg Horizon. Each member of the Maastricht Formation is segmented by their own characteristic horizons, named in Figure 3.

Figure 3: Overview of the Maastricht Formation members4

The six members of the Maastricht Formation are briefly described below. - Valkenburg member In the western part of the formation, the limestone can have the following colors: white yellow to yellow grey. The limestone contains cherts which can be light grey or grey brown. The chert content is between 5%-9% (Felder & Bosch 2000, p.74). The percentage of calcium-carbonate is between 75%-95% (Felder & Bosch 2000, p.74). The percentage of silica is higher than in other members. A mineral characteristic of the Valkenburg member is glauconite. The boundary between Valkenburg member and Gronsveld is determined by Horizon van St. Pieter.

4 From “Scripta Geologica”.

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- Gronsveld member The limestone is fine grained, yellow-white and contains large nodular to small cherts. The color of the cherts is brown grey. There are no or few fossils in the limestone. The thickness of the limestone is between 4 and 10 meter (Felder & Bosch 2000, p.77). The boundary between the Gronsveld and Schiepersberg is formed by the Horizon of Schiepersberg. - Schiepersberg member The limestone of the Schiepersberg member is fine grained and weak. The color is yellow- white to light yellow in which light-grey to brown-grey chert nodules are distributed. The calcium carbonate content is approximately 96% (Felder & Bosch 2000, p.80). The thickness of the Schiepersberg varies from 4 to 6 meters (Felder & Bosch 2000, p.80). The Horizon of Romontbos forms boundary between the Schiepersberg member and Emael member. - Emael member The limestone is weak, fine grained and light yellow colored. In its lower part, it contains large light-grey chert nodules. The cherts have a pipe and plate shaped geometry. The calcium carbonate content is approximately 97% (Felder & Bosch 2000, p.82). The thickness of the Emael Member can be between 2 and 10 meters. The horizon dividing the Emael and the Nekum is the Laumont horizon, characterized by a hardground. - Nekum member The limestone of the Nekum member is weak, fine- to coarse grained with brown-grey cherts. The calcium carbonate content is between 94%-99% (Felder & Bosch 2000, p.85). The thickness of the layer varies from 5 to 15 meter. There is about 1% of cherts (Felder & Bosch 2000, p.85) in the lower part of this member. The Horizon of Caster forms the boundary between the Nekum and Meersen member. - Meersen member The limestone is weak, fine- to very coarse grained. It contains irregular hard and soft limestone layers. The calcium carbonate content varies between the 95% and 99% (Felder & Bosch 2000, p.88). The thickness is approximately 18 meters (Felder & Bosch 2000, p.88). The Meersen member is easily distinguished based on its high content in macro-fossils.

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Table 1: table of mineral content of the Maastricht Formation5

Faults in Valkenburg Valkenburg is located between two faults. The Klauwpijp fault and the Schin op Geul fault. The origin of the faults has not been investigated thoroughly within this BSc project. Three tectonic phases took place in the Cretaceous. In the last phase the plates started to converge causing uplift, faulting and erosion of sediment layers.

Figure 4: geological map of the faults in Valkenburg6

5 From “Krijt van Zuid-Limburg”, p. 131

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Chapter 2: Approach and methods

Section 2.1: The UCS test and the needle penetration test

2.1.1: The UCS test

The UCS test is applied to determine the uniaxial compressive strength of the rock material. For the UCS test, specimens from drill cores are cut to form a cylinder with a specific length and diameter. The flatness of the end surfaces is important for even distribution of the load. The quality of the weakest cores did not allow the selection of long samples for UCS testing. As a result, flatter samples were tested than recommended by ISRM or ASTM (Ngan-Tillard & Mulder, 2012). The presence of imperfections and cherts did not allow sub-coring to obtain slender samples. At some occasions, a dental plaster was cast at the extremities of the sample to improve their end conditions.

In UCS testing, the cylindrical samples are subjected to axial compression (shortening) between two flat plates. During the test, the vertical displacement is controlled and the axial force is recorded. The radial displacement can be measured to determine the Poisson’s ratio of the material. That was not done for the series of tests conducted on the Valkenburg samples. The test was continued until, at least, failure occurred. Unloading / reloading loops can be made to assess the elasticity of the material. That was not done during the tests on the Valkenburg cores.

Figure 5: UCS test

6 From “Krijt van Zuid-Limburg”, p.21.

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The load at failure is related to the UCS of the material. The E50 is the tangent modulus of deformation at

50% of the UCS. It was derived from the UCS graphs by the authors of this thesis. The E50 includes both the permanent and elastic deformability of the material. Elasticity refers to the property of reversibility and instantaneity of deformation in response to load (Goodman, 1989).

Figure 6: reading the UCS of the rock material7

2.1.2: The needle penetration test

This test is done with a Eikelkamp handpenetrometer, type 1B.

Figure 7: Eijkelkamp handpenetrometer8

7 From the course Rock Mechanics.

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Because the Maastrichtian limestone is very weak, it is difficult to find material to prepare samples which fulfill international standards for UCS testing, so it was decided to assess material strength using the Needle Penetrometer test. The test is a non-destructive index strength test. A modified version of the 06.06 surface hand penetrometer, which is a name of equipment manufactured by Eijkelkamp, the Netherlands (http://www.eijkelkamp.com/Portals/2/Eijkelkamp/Files/P1-53e.pdf) is used. The standard Eijkelkamp cone has been replaced by a short needle made of hardened steel. Needles with a diameter of 1 or 1.4 mm and with a flat or a conical tip are available. The needle with a 1.4 mm diameter and a cone angle of 60o was used to test the Valkenburg cores. The needle of the modified Eijkelkamp penetrometer is pushed until a constant compression of the spring is observed or the maximum needle penetration (8.5 mm) is reached. The spring compression is read with the help of an indicator ring on the millimeter scale of the penetrometer. The maximum spring compression is 8.5 cm. By similarity with cone tip resistance, the needle resistance, NPRE is calculated by multiplying the spring stiffness by the observed spring compression and by dividing this calculated force by the needle cross section. The sensitivity of the Eijkelkamp penetrometer can be optimized by adjusting the spring stiffness. Springs with a capacity of 50, 100, and 150 N are available. The 50 and 150 N springs were used to test the Valkenburg cores. The results obtained with the 50 N were translated into readings made with the 100 N spring. Please refer to Ngan-Tillard et al., 2011 for more information on the needle penetration test and correlation between needle resistance to penetration and UCS for the Maastrichtian limestones.

Section 2.2: gamma ray Author: Joëlla Lie-A-Fat

Gamma radiation is caused by three natural elements. These are: potassium (K), uranium (U) and thorium (Th). These three elements can be found in granites, volcanic rocks, igneous rocks and clays. The tool which measures the gamma ray is called a gamma-ray tool. The unit of a gamma log is the Count Per Second (CPS) or the American Petroleum Institute (API). The interpretation of the log is the same for both units. If gamma ray values are high, it could mean that the clay mineral content is high, as clay is rich in potassium. It could also mean that the ground contains elements such as Thorium or that it contains Uranium. Uranium usually indicates material of an organic origin as organisms are extremely good at concentrating and storing uranium. The presence of potassium without thorium (with or without uranium) is usually an indicator of the remains of algal mats in the carbonate, or of glauconite (Glover, P.). Contents in K, U and Th can be distinguished when a spectral gamma ray log is recorded.

Section 2.3: XRF-analysis Author: Aswien Dwarkasing

The X-ray Fluorescence (XRF) analysis allows to determine the percentage of chemical elements present in a material. The material can be in powder, liquid or solid form. A XRF -spectrometer sends a x-ray beam. This beam is called the ‘’incident beam’’. When the x-ray beam reaches the atoms in the sample, the atoms get excited. Each atom has its own characteristic wavelength or X-ray. The back scattering of

8 From “Application of the needle penetration test to a calcarenite, Maastricht, the Netherlands”

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x-ray is recorded. It is displayed on a computer screen. The measurements need to be processed to be able to obtain the content in different chemical elements and convert these contents to mineral content, for example silica (SiO2) or calcium carbonate (CaCO3). XRF analysis can help to identify the limestone of Valkenburg. This limestone contains in average 15% of SiO2 (

Table 1), against only 2% for the other members of the Maastricht Formation (Felder & Bosch 2000, p.131).

The backscattering of atoms is explained below in more details. The atoms in the sample absorb the x- ray beam by ionization, ejecting electrons from the lower energy levels. The ejected electrons are replaced by electrons from the outer shell, a higher energy orbital (see Figure 8). When the replacement of electrons take place, energy is released due to the decreased binding energy of the inner electron compared to the outer one. The release of energy is in the form of emission of x-ray. The major elements which can be measured by x-ray fluorescence are: Silicon (Si), Titanium (Ti), Aluminum (Al), Sodium(Na), Calcium (Ca), Magnesium (Mg), Manganese (Mn), Iron (Fe) and Potassium (K).

Figure 8: Schematic view of a portable XRF-spectrometer

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Several Valkenburg samples were analyzed using two XRF-machines. The first apparatus was from the Cultural Heritage Agency in Amersfoort (Rijksdienst voor het Cultureel Erfgoed) (Figure 9) and the other, a fixed device, Epsilon 3 XL from the TU-Delft (see Figure 12). There are differences in measuring between the two devices. - The sample must have a flat surface to be analyzed with the portable XRF device. A flat surface was obtained by sawing the cores (figure 12). The portable XRF measures 2mm into the sample and has a 8mm lens to measure the surface. There is no restriction regarding the size of the sample. The measuring time was set at 80 seconds for one measurement. The duration of a measurement influences the quality of the results. Measurements were made and processed by Bertil van Os, employee at the Cultural Heritage Agency.

- The sample must have a maximum diameter of 25 mm (Figure 13) to fit into the sample holder of the TU-Delft apparatus (Figure 12). Up to ten samples can be measured simultaneously. Samples analyzed with the TU Delft machine were sub-cored from samples analyzed with the portable device. The XRF machine of the TU-Delft can also be set to different measuring times. It measures at the surface of the sample. It is difficult to know which surface has been measured. The measurements were done and processed by Ron Penners, employee at the TUD. The equipment is new and experience with it is being gained. The units of XRF results are in Parts Per Million (ppm). They are then converted to percentages.

Figure 9: the XRF-spectrometer from Cultural Heritage Agency in Amersfoort.

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Figure 10: Sample holder of the portable XRF spectrometer

Figure 11: sawing of the samples for the portable XRF device

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Figure 12: the Epsilon 3 XL XRF device of the TU-Delft

Figure 13: samples for the XRF device of the TU-Delft

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Section 2.4: macroscopy Author: Aswien Dwarkasing

The Valkenburg samples have been observed with a Leica/Wild M420 macroscope. Microscopes are used for very small scale sized objects. Macroscopes are optical precision instruments for studying objects in their entirely in conjunction with large working distances and large fields of view. The optical system involves a vertical beam path. This is split into two parts in the binocular tube, just for comfort (Handbook of the Lyca/Wild M420 macroscope). The zoom ranges from 58x (22mm) to 350x (3mm). This macroscope has a camera, with which pictures of the samples are taken.

Figure 14: the Leica/wild M420 macroscope

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Section 2.5: chert Author: Joëlla Lie-A-Fat Aswien Dwarkasing

In the six members of the Maastricht Formation, different amounts of cherts with specific shapes and colors are found. In this section, the chert characteristics are depicted for each member and the percentage of chert per member is indicated based on published values. Cherts bigger than 1 cm were sieved or manually picked out of each core lining of the Valkenburg boreholes. After weighting them, their volume was calculated using a density of 2650 kg/m3 (quartz density). With the chert volume and the volume of the core lining, the volumetric percentage of chert was calculated. The cores also contained a lot of proto-cherts. The colors of the cherts were determined using a color chart found in Appendix B.

Figure 15: sieved chert and proto-chert from MB-02

The first member of the Maastricht Formation is the Meerssen, but this member is found more N-W of Valkenburg, not in Valkenburg (Felder & Bosch 2000, p.88). The second member of the Maastricht Formation, the Nekum member, has less than 1% (volume %) brown-grey chert nodules. The third member, the Emael, has more (9%) big light grey chert nodules. The cherts in this member have more specific shapes; plate shaped or pipe shaped cherts (Figure 16) are common.

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Figure 16: plate and pipe shaped cherts, which are typical of the Emael member9

The fourth member, the Schiepersberg, has regularly occurring layers of chert, but light grey and brown grey nodules occur also. Around 7.5% of the total volume should be chert. In the sixth member of the Maastricht Formation, the Gronsveld, the volume of cherts is between 5 and 10% of the total volume. The cherts can be small or big, brown-grey and arbitrary in shape. The last member, the Valkenburg, has some light-grey to grey-brown nodules (6%).

9 From “Krijt van Zuid-limburg”, p.83

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Section 2.6: fossils Author: Joëlla Lie-A-Fat

The boundaries of the members of the Maastricht Formation are called horizons. In Table 2, the horizons can be found.

Table 2: layers with their horizons10

Most of the horizons in the Maastricht Formation are recognized by a thin fossil debris layer at the base of the upper layers and hardgrounds at the top. The horizon of Lichtenberg, at the base of the Maastricht Formation, consists of a bioturbation layer in the top of the underlying Gulpen Formation and a glauconite-rich fossil debris layer at the base of the Maastricht Formation. Some characteristic fossils of the different members will be given below: Limestone of Valkenburg The Valkenburg is not rich in fossils. The debris layers in the Valkenburg member, are coprolite (=fossilized feces) layers and they are mixed with fossils from underlying layers (Felder & Bosch 2000, p.74).

10 From “Krijt van Zuid-Limburg”, p.72

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The limestone of Gronsveld The Gronsveld is not rich in fossils either, except for a few laminated fine grained fossil debris layers. In the laminated fossil debris layers a few sea lilies, snakes, sea stars or parts of these could be found. (Felder & Bosch 2000, p.77). Limestone of Schiepersberg Just like the Valkenburg and the Gronsveld, the Schiepersberg does not have a lot of fossils except for the fossil debris layer at the base. Limestone of Emael The top of this member has a lot of fossil debris near Emael, to the south of Maastricht. But in Valkenburg, there is just a thin layer of fossil debris at the base. Limestone of Nekum The horizon of Laumont shows fossil debris layers at the base of the Nekum. This layer is rich in tube worms and oysters which are sickle-shaped instead of oval. Higher in the formation, the sea urchins are the dominant fossils, but ammonites are also found.

Figure 17: sea urchin Hemipneustes striatoradiatus in the Maastricht Formation11

11 From http://museumboekenberg.skynetblogs.be/archive/2005/12/index.html

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Figure 18: tube worm remains in the Maastricht Formation12

12 From “Campanian-Maastrichtian serpulids from Thermae 2000Borehole (Valkenburg a/d geul)”.

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Chapter 3: Results and interpretation In this chapter the results of the test are given and their interpretation.

Section 3.1: UCS and needle penetration test results and interpretation

3.1.1: The UCS test results 25 UCS tests were conducted on the Valkenburg cores. Results are listed below.

Table 3: UCS and E50

Borehole sample length/diam Remark UCS E50 m below ground surface - MPa GPa MB01 10.00 1.3 Irregular sample 0.07 0.003 MB01 11.08 1.5 Irregular sample 0.08 0.005 MB01 11.71 1.1 0.07 0.003 MB01 12.25 1.1 0.35 0.005 MB02 10.20 1.1 Irregular sample 0.27 0.013 MB02 10.82 1.6 0.04 0.003 MB02 11.30 1.5 0.07 0.006 MB02 11.98 1.5 Irregular sample 0.16 0.012 MB02 12.15 1.4 0.08 0.05 MB02 13.68 2.0 5.02 1.767 MB02 14.93 1.1 0.25 0.02 MB02 15.15 1.2 0.29 0.019 MB02 19.74 1.4 0.05 0.001 MB03 10.40 1.2 0.81 0.09 MB03 12.83 0.9 Irregular sample 0.64 0.0326 MB03 13.25 0.8 Irregular sample 0.89 0.136 MB03 14.10 1.4 0.24 0.0201 MB03 16.02 1.3 0.24 0.0143 MB03 18.40 1.5 pieces missing 2.43 0.625 MB03 18.70 1.4 1.1 0.22 MB04 10.10 0.9 1.88 0.3883 MB04 12.20 1.1 2.27 0.468 MB04 13.45 0.9 1.61 0.1 MB04 14.90 1.5 pieces missing 0.12 0.0062 MB04 21.35 1.6 0.96 0.1096

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Interpretation In most occasions, the weakest material was targeted for UCS testing. Due to sample imperfections, the UCS tests provided a low estimation of the material strength. The presence of sub-horizontal discontinuities in the samples increased the deformability of the material without affecting its strength.

3.1.2: The needle penetration test results

The needle penetrometer logs are displayed in Figure 19 and Figure 20.

Figure 19: Pocket penetrometer results MB-01 and MB-02

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Figure 20: Pocket penetrometer results MB-03 and MB-04

Interpretation The needle penetrometer logs are interpreted here qualitatively. The needle penetrometer logs indicate a significant increase in strength at 18, 17 and 15.5 m below ground level in boreholes MB-02, MB-03 and, respectively MB-04. At greater depths extremely and very weak limestones are found, but over very limited depths and at a low frequency. At shallower depths, the limestone presents a variable strength at the centimetric to the metric scale. This is due to variations in degree of silicification, cementation, weathering and fracturation. Some fracturation and weakening of the limestones have occurred during drilling when the drill bit went through materials of contrasting strength encountered at the same depth.

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Section 3.2: gamma ray, results and interpretation Author: Joëlla Lie-A-Fat

For the Hurks car park project, gamma ray logs have been recorded in boreholes MB-02, MB-03 and MB- 04 up to 23 m below the ground surface. The three gamma ray logs have been kindly provided by Deltares, under the condition that they are used internally and remain confidential. They are displayed below.

Figure 21: Segmented gamma ray logs. The limestone starts from about 10 m below ground level.

3.2.1: gamma ray, interpretation of results The publication by Felder and Boonen (1988) is expected to give insight into gamma ray patterns in the different members of the Maastrichtian limestone. Unfortunately, the publication could not be found. Similarities and divergences between the three gamma ray logs are described below. The segmentation of the logs is indicated in Figure 21.

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Limestone was found at 9.82, 9.70 and respectively 8.85 m below ground surface in boreholes MB-02, MB-03 and, respectively MB-04. Gamma ray patterns observed at shallower depths are not considered here. The CPS values increase significantly at a depth of 10.2, 10.6 and respectively 10.3 meters below ground surface in MB-02, MB-03 and MB-04. These depths correspond to 59.8, 58.4 and 60.2 m NAP.

An overview of the segmentation of the logs recorded in MB-02, MB-03 and MB-04 is given in Table 4.

Table 4: Intervals with homogeneous CPS values and vertical shift between these intervals

Depth Interval Compared below Vertical shift boreholes ground Averaged CPS with respect to ground Vertical shift with respect surface surface to NAP 1 MB-02 10.2-12.50 55 MB-02 to MB-03: -0.4 m MB-02 to MB-03: +0.60 m MB-03 10.6-12.60 45 MB-03 to MB-04: +0.3 m MB-03 to MB-04: -1.20 m MB-04 10.3-12.40 44 MB-02 to MB-04: -0.10 m MB-02 to MB-04: -0.60 m

2 MB-03 12.60-15.00 37 MB-03 to MB-04: -0.2 m MB-03 to MB-04: -1.30 m MB-04 12.40-15.00 34

3 MB-03 15.00-18.20 25 MB-03 to MB-04: 0 m MB-03 to MB-04: -1.50 m MB-04 15.00-18.40 25

4 MB-02 18.50-23.00 37.5 MB-02 to MB-04: -0.1 m MB-02 to MB-04: +0.40 m MB-04 18.40-23.00 44

Table 4 indicates that the Gamma ray zones identified in the logs of MB-02, MB-03 and MB-04 are not very different from each other. Zone 1 is found in each borehole, at approximately the same depth and shows the same CPS values. The maximum vertical shift is 1.50 meters when differences in surface level with respect to NAP are considered. MB-02 and MB-04 are almost the same except for the fact that the transition around 15 meters is not clearly found in MB-02. The obvious gradual decrease in CPS starting from approximately 18.4 meter is clear in MB-02 and MB-04. The maximum vertical shift between the zones found in these two boreholes is 60 cm. With these results the conclusion can be drawn that there are no faults of significant importance between these two boreholes. The gradual decrease in CPS value in MB-02 (zone 3) and MB-04 (zone 4) is not found in MB-03, which may lead to the conclusion that the last zone of MB-03 is not the same. From 18.20 meter downward the composition of the layer(s) found in MB-03 is different, but the zones recognized from 18.20 meter and up are similar to the zones found in MB-04. The biggest differences are found between MB-02 and MB-03. The only similar zone is between 10.50 and 12.50 meter. It is difficult to conclude what causes this difference. This difference can be caused by

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a fault or maybe by local differences in sedimentation. The boreholes are located at a short distance from each other nearby the Hema in Valkenburg town center.

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Section 3.3: XRF results and interpretation Author: Aswien Dwarkasing

The XRF analysis provides the fraction of chemical elements present in the material in % and in mg/kg. Some concentrations are below the detection limit of the equipment and cannot be used. This is the case for Pb, Zn, As en Cu. From the results, the percentage of limestone (CaCO3), quartz (SiO2) and gypsum (CaSO4) are calculated. The gypsum percentage is calculated assuming that all sulfur is in gypsum. The sum of gypsum, quartz and limestone percentages is found to be higher than 100% due to a wrong correction in the percentage of Calcium (Ca). The percentages were corrected to obtain a sum equal to 100%.

After the measurements the results of gypsum (CaSO4.2H2O), limestone (CaCO3) and Silica (SiO2) are calculated.

The results are given in bar charts below. The results from both XRF-machines are plotted first. Some samples were measured twice with the hand held XRF (HH-XRF), because of different observations on the flat surfaces.

Figure 22: measurement results of chert sample from MB-02 at 13 meter depth. The blue and red bars indicate the results obtained at the RCE and respectively, TU-Delft.

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Figure 23: the blue and green bars are the results from the handheld-XRF (HH-XRF) from which the same sample has been measured at different surfaces. The red bars indicate results obtained at TU Delft.

Figure 24: the blue and green bar represent the results from the handheld-XRF from which the same sample has been measured at different surfaces. The red bar represents a result obtained at TU Delft.

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Figure 25: the blue and green bar are the results from the handheld-XRF from which the same sample has been measured at different surfaces. The red bar represents a result obtained at TU Delft.

The percentages of CaSO4, CaCO3, and SiO2 obtained in Amersfoort are shown as function of depth for boreholes MB-02, MB-03 and MB-04 in Figure 26, Figure 27 and Figure 28.

Figure 26: overview of gypsum, calcium carbonate and silica content with increasing depth for MB-02.

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Figure 27: overview of gypsum, calcium carbonate and silica content with increasing depth for MB-03.

Figure 28: overview of gypsum, calcium carbonate and silica content with increasing depth for MB-04

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Interpretation The samples analyzed using XRF were chosen to better understand the trends observed on the gamma ray logs. The insight gained into the meaning of the gamma logs with the help of the XRF analyses is presented in section 3.2 and section 3.2.1.

The charts displayed in figure 22-25 indicate a discrepancy between the measurements made in Amersfoort and Delft. Much less gypsum is found in Delft. From the chart of MB-04, it can be seen that limestone (CaCO3) content measured in Delft is 89% against approximately 75% in Amersfoort. The percentages of silica (SiO2) obtained in Delft and Amersfoort are almost the same, approximately 5%. The first measurement was 7% silica. This means that the XRF of the TU-Delft has detected a higher percentage of limestone. The observed discrepancies can have several causes ranging from error measurements, differences in technique (for example, exposure time) to variations in the surface and volume of material tested. It is recommended to investigate the differences. Thin sections or XRD analysis could be made to detect the presence of gypsum.

The following interpretation of the XRF results obtained in Amersfoort (figure 22-25) is made with the help of Hans Huisman: - The content in Potassium (K), Iron (Fe) and Aluminum (Al) is low. This indicates that the samples do not contain pyrite and have a very low percentage of clay and glauconite. - Some samples are rich in Sulfur (S). They contain up to 33% gypsum. This is the case for MB-02 at 17.95 - 18.15 meter depth (see Figure 23). The presence of gypsum in Valkenburg’s limestones is not surprising. The limestones were formed under tropical weather in shallow waters. To the knowledge of the authors, gypsum has not been reported in Maastricht. Valkenburg was located closer to the coast of the Cretaceous Sea than Maastricht. Its water depth was lower, evaporites such as gypsum are more likely to be found in Valkenburg than Maastricht.

- The quartz content is variable. A very high percentage of SiO2 (quartz) (98%) was obtained for cherts as expected (see Figure 22). Proto-cherts contain about 58%

of limestone (CaCO3) and 42% of SiO2 (result from MB-03 at 25.90-26.00 meter).

- The highest percentage of SiO2 measured for limestone samples (13% for MB-02, 15% for MB-03 and 10% for MB-04) are not obtained at the greatest depths where the limestone of the Valkenburg member, which is richer in silica than the younger members, is expected. The measured percentages of silica in the limestone are higher than values reported in the literature (

-

-

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- Table 1); only 0.2 to 1.3% in the members younger than the Gronsveld member, and 1.7% in the Gronsveld limestone. It is possible that these results presented by Felder and Bosch (2000) do not apply for the Maastrichtian members in Valkenburg.

Section 3.4: macroscopy Author: Aswien Dwarkasing

The main purpose of the microscopic observations was to determine the grain size of the limestone. However, grains could not be seen in the solid limestone, even at the highest magnification of the Leica/Wild M420 macroscope. The material appeared like a compact mass with some pores under the macroscope. Cemented and loose grains could not be distinguished in the material reduced to powder. For the determination of the grain size, thin sections are needed. Taking into consideration the limited duration of the BSc project, making thin sections was not possible.

With the Leica/Wild M420 macroscope, we were, nevertheless, able to identify some minerals and get a better look at the boundaries between (proto) chert and limestone.

Figure 29: MB-04 at 18.68 meters depth

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Figure 30: MB-03 at 16.31 meters depth

The green mineral found in Figure 29 can be glauconite but the XRF did not show a particularly higher content of iron.

Figure 30 shows cavities in the limestone. In the cavity a mineral, which can be calcite, has formed. But the mineral looks cubic while calcite is a trigonal mineral (Maaike van Tooren, personal communication, june 2012). We cannot conclude on the mineral type. Cavities were visible in a few other samples too.

Section 3.5: cherts Authors: Joëlla Lie-A-Fat Aswien Dwarkasing

In this section, the color of the cherts (Appendix B1), the shape and the amounts per core are shown. In Appendix B, the values used to do the calculations can be found.

3.5.1: MB-01

For MB-01 we did not calculate the chert volume percentage, but we have an estimate of a mass percentage. The core from 9.40-10.40 was not recovered properly, so it came in a bucket. We sieved the material (with water) with a 2mm sieve to estimate the amount of chert. In Figure 32 the remaining cherts are shown. The mass percentage of chert in the core was 22%. Most of the cherts present in MB- 01 were dark brown but there were black ones too. These cherts did not have a particular shape.

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Figure 31: chert from slurry MB-01

Figure 32: cherts from MB-01

3.5.2: MB-02 The chert percentage in MB-02 was calculated from 9.40 till 15.90 meters. An average of 6% was found. In Table 5 the chert percentage is given according to depth.

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Table 5: chert percentage in MB-02

Chert Core depth amount Meter below ground surface % 9.40-10.40 2.8 10.40-11.40 7.8 11.40-12.40 3.1 11.40-13.00 5.6 13.00-14.40 12.7 14.40-15.90 3.8

At 9.40 meters small light brown cherts were found. Slightly deeper (9.70 meters), brownish grey small pieces of chert were found. At greater depths, more proto-cherts are found.

Figure 33: light brown chert in MB-02 at 9.40 meters (left) and brownish grey cherts at 9.70 m (right).

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Figure 34: proto-chert in MB-02

The shape of the cherts is variable. The only shape we recognized was a pipe shaped proto-chert. Bjorn Vink confirmed this.

Figure 35: pipe shaped proto-chert in MB-02 at 11.90 meter

3.5.3: MB-03 In MB-03 the chert volume percentage was calculated from 9.50 to 12.50 meters. The amount per core is shown in Table 6.

Table 6: chert amount in MB-03

Core Chert amount Meter below %

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ground surface 9.50-11.00 11.3 11.00-12.50 9.9

The cherts in the cores were light brown, dark brown and bastion grey (Appendix B: the color chart and Appendix B1: the cherts).

Figure 36: light and dark brown chert in MB-03 between 9.50 and 11.00 meters

Just like MB-02 the shapes were very variable, but the pipe shaped proto-chert was also found.

Figure 37: pipe shaped proto-chert in MB-03

3.5.4: MB-04 For MB-04 the chert percentage was calculated from 8.00 – 15.50 meters. The average amount of chert is 11.6%. The amount per core is shown in Table 7: chert amount in MB-04 .

Table 7: chert amount in MB-04

Chert Core amount

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Meter below ground surface % 8.00-9.50 12.18 9.50-11.00 12.59 11.00-12.50 8.11 12.50-14.00 22.37 14.00-15.50 2.69

The analyzed cherts were mostly brown, with some dark grey ones.

Figure 38: dark brown chert at 25.70 meters, MB-04

Just like MB-02 and MB-03, the only recognizable shape is a pipe shaped proto-chert.

Figure 39: pipe shaped proto-chert in MB-04

Interpretation

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The pipe shaped cherts found in MB-02 (11.90m), MB-03 (13.00-14.50 m) and MB-04 (13.00-14.50 m) are mostly found in the Emael limestone (Felder & Bosch 2000, p. 83). The color of the cherts of the upper part of the cores also indicates the Emael member (Bjorn Vink, personal communication, June 2012). Based on the color (brown-grey) of the cherts found in the deeper part of the cores, no particular conclusion can be drawn. The cherts can be from the Valkenburg member or the Gronsveld member (Bjorn Vink, personal communication, June 2012).

According to literature the Nekum member has less than 1% chert (Felder & Bosch 2000, p.132). From our calculations, the volume percentage of chert is greater than 1%. We conclude from these observations that the Nekum member is not present in MB-02, MB-03 and MB-04. To draw this conclusion, we assume that chert percentages published in the literature (

Table 1) for the different members of the Maastricht Formation are valid for limestones in Valkenburg.

Section 3.6: Fossils

Author: Joëlla Lie-A-Fat

As described in the literature, the cores of the members of the Maastricht Formation that were examined were not rich in fossils. The few macro-fossils found in the cores are described below using expertise provided by John Jagt, paleontologist at the NHMM and Paul Kisters, geologist at the NHMM.

In MB-01, at depth 18.90 meters, a weathered fishbone was found (Figure 40). Based on the shiny character of this bone, it could be a finfish. The size of the bone suggests that it could be a predatory fish which belong to the family of the Enchodontidae.

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Figure 40: weathered fish bone of the type Enchodontidae of the Upper Cretaceous13

In MB-02, at a depth 13.90 m, a part of the belemnite was found (Figure 41).

Figure 41: belemnite remains

In MB-02, at a depth of 25 m, a snail was found (Figure 42). It may be a naticidae, i.e., a moon snail, a predatory sea snail. Such snails are common in Cretaceous limestones.

13 From Wikipedia

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Figure 42: gastropod (snail)

In MB-04, at a depth of 23.40 m, remains of belemnites were found (Figure 43).

Figure 43: belemnite remains

Interpretation In brief, in all the cores only three macro-fossils were found in the limestone. After identification of the three fossils, no conclusion could be drawn on their appurtenance to a given member of the Maastricht Formation.

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Chapter 4: Correlation of gamma ray logs with other results Authors: Joëlla Lie-A-Fat Aswien Dwarkasing

Integration of gamma-ray and XRF results

Samples were picked from the cores for XRF analyses, to determine whether the higher gamma ray values were caused by higher clay content. Clay minerals are rich in Potassium and associated with high gamma ray values. XRF results revealed that the higher gamma ray values are not caused by higher potassium content. The potassium content is very low for all samples. It can be concluded that there is a low concentration of clay present in the limestone.

Huisman (personal communication, May 2012) formulated the following interpretation. The only other elements that are picked up by the gamma log are U and Th. Their concentrations are too low, however, to be detected by the hand-held XRF. It would be most likely that the gamma-profile is caused by elevated uranium contents. Some of the samples had higher iron (Fe) contents, maximum 0.5% from the handheld XRF-analyzer and 0.9% for borehole MB-02 at 17.95 meter depth, probably because of organic matter. If these samples are from the zones with higher gamma-ray intensities, that would be the most likely cause. However, the authors of this report observed that is not the case. The only other option is that Th levels are elevated in those zones. This is less likely, since Th usually occurs mainly in the heavy mineral fractions, and the other elements that are associated with this fraction (Zr, Ti) did not seem to vary much. The maximum percentage of Zr and Ti measured in all samples from the hand held XRF are respectively 0.0079% (Zr) and 0.068% (Ti).

Wolf (personal communication, 2012) explained that uranium is commonly associated with strontium in Dutch Carbonate rocks. Strontium has been detected using XRF. However, its percentage does not vary significantly in the limestone samples and its fluctuations are not associated with given CPS zones.

Table 8: CPS values compared to the strontium (Sr) percentage with respect to depth in MB-02

MB-02 Average Depth(meter) Sr(%) Sr (%) TU-Delft CPS 18.60 46.0 0.05 17.95-18.15 26.0 0.06 17.95-18.15 26.0 0.06 0.16 22.40-22.55 30.0 0.06

26.00 0.15

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Table 9: CPS values compared to the strontium (Sr) percentage with respect to depth in MB-03

MB-03 Average Depth(meter) Sr(%) CPS 12.00 40.0 0.05 12.00 40.0 0.07 16.25-16.40 22.00 0.00 16.25-16.40 22.00 0.05 19.00-19.10 53.20 0.04 21.10-21.20 15.60 0.06

Table 10: CPS values compared to the strontium (Sr) percentage with respect to depth in MB-04

MB-04 Average Sr (%) TU- Depth(meter) Sr(%) CPS Delft 14.00-14.15 42.2 0.06 14.00-14.15 42.2 0.06 16.50-16.60 29.7 0.06 16.50-16.60 29.70 0.06 18.60 65.60 0.05 17.35-17.55 29.70 0.05 17.35-17.55 29.70 0.05 21.95-22.05 25.00 0.06 0.17

To conclude, the same patterns can be recognized in the gamma ray logs of MB-02, 03 and 04. However, they are not linked to the presence of clay, glauconite, organics or strontium in the limestone.

Integration of gamma ray results and core description in terms of color and material type

- The significant increase in CPS values observed at a depth of 10.2, 10.6 and respectively 10.3 meters below ground surface in MB-02, MB-03 and, respectively MB-04 was first thought to indicate the interface between gravels and limestone. However, limestone was found in the boreholes at 0.4 to 1.4 m above the depth at which the CPS values increase. - All three gamma ray logs show a change in trend around 12.5 m below ground surface. In MB-03, this change corresponds to the transition to a limestone which is less easily crushable by hand and is finer grained. In MB-02, it falls within a zone of (man-made) fractured and crushed limestone rich in cherts. In MB-04, it falls just 10 cm above such a zone. - All three gamma ray logs show a change in trend around 18.5 m depth. In both MB-02 and MB-03, the change is located at about 30 cm above the passage from the grey limestone to the yellow limestone with grey proto-cherts. In MB-04, the change falls within the yellow

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limestone. There is no grey limestone at proximity. Note that the grey limestone is about 5 m thick in MB-03 against about 1 m in MB-02.

In brief, no insight into the interpretation of the gamma ray patterns is gained from the correlation of the core description in terms of colors and the gamma ray logs. Moreover, limestone was retrieved from shallower depths than the depths at which the CPS values increase significantly around 10 m depth below ground surface. This increase was first thought to correspond to the passage from gravels to limestone.

Integration of gamma rays, grain size and porosity.

Variations in gamma rays could be related to changes in grain size and porosity. The number of gamma rays returning to the detectors is inversely related to the number of hydrogen atoms, which is highly related to the porosity of the rock (Crain’s Petrophysical handbook). In formations with a large amount of hydrogen atoms, the neutrons are slowed down and absorbed very quickly and in a short distance. The count rate of slow neutrons or capture gamma rays is low in the tool. Hence, the count rate will be low in high porosity rocks (Glover, P.). It is recommended to investigate such relations. Identification of fine grained materials at the naked eye is subjective, when clay size and silt size particles are mixed. Grains could not be detected using a macroscope. Thin sections are needed. Micro-CT scans can provide a detailed 3D view of the limestone microstructure, at least for the coarser limestones.

Integration of gamma rays and strength profiles. The needle penetrometer logs indicate a significant increase in strength at 18.0, 17.0 and 15.5 m below ground level in boreholes MB-02, MB-03 and respectively MB-04. The change in trend of the gamma logs around 18.0 m depth correspond approximately to the transition to stronger limestone for MB-02 and MB-03, not for MB-04.

Integration of gamma ray results and results of fossil study.

Very few macro-fossils have been found in the cores. One cannot explain patterns in the gamma logs by zones rich or poor in macrofossils. The rarity of macro-fossils in the cores indicates that the Meerseen member has not been encountered in boreholes MB-02, 03 and 04.

Integration of gamma ray results and results from the chert study

More than 1% of chert is encountered in the shallowest cores. This indicates that the Nekum member has not been encountered in boreholes MB-02, 03 and 04.

Note that the above conclusions have been made assuming that the results published by Felder and Bosch (2000) for the Maastrichtian members are relevant in Valkenburg.

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This might not be the case. The XRF analyses show higher SiO2 percentages than expected at least in the members younger than the Valkenburg member.

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Conclusions and recommendations Authors: Joëlla Lie-A-Fat Aswien Dwarkasing

For this project the cores of four boreholes drilled in Valkenburg were provided for analysis. Different methods were used to distinguish which members of the Maastricht Formation the cores were drilled in. The UCS test and the needle penetration test were used to determine the strength of the material. The gamma ray logs were provided and used to determine transitions in the formation. The XRF analysis was used to look at the mineral content. The fossils found in the cores were analyzed.

The following conclusions were drawn from the results of the applied methods:

- The information from the macroscope and the fossils did not lead to any significant conclusions. The difference between loose grains and cemented grains is not visible. From all the four core linings, only three macro-fossils were found: a fishbone, gastropod and remains of belemnites. But according to literature, these fossils are not characteristic for the last four members of the Maastricht Formation.

- From the UCS test, the authors of this thesis can conclude that the calculated values are low estimate of the material strength, because of imperfections found in the samples. The imperfections can be of natural or man-made origin.

- The gamma ray logs showed some patterns which could be tracked in at least two logs. In MB- 02, three zones were identified, while in MB-03 and MB-04 four zones were identified at approximately the same depths. The variations noticed in the three boreholes can be caused by local variations in sedimentation conditions or by minor faulting.

- The zones were defined based on CPS values. Usually high CPS values indicate higher clay content. If correlated to the XRF results this should show higher potassium contents. But the correlations between the results of the gamma ray and the XRF show that the high CPS values do not correspond with higher potassium contents. The potassium contents do not exceed 1% . If the higher CPS values are not caused by an elevated K content, organic matter is expected to be found, which must correspond to higher uranium concentrations. The dark spots in the limestone can indicate organic matter. However the correlation between visual observations and XRF results indicates that this is not the case. Uranium is thought to be commonly associated with strontium in Dutch carbonate rocks. However 0.07% is the maximum percentage of Strontium measured by the hand held XRF. The XRF machine at the TU-Delft measures higher strontium percentages varying from 0.11% to 0.17%.

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- The correlation between the gamma ray and the core analysis indicates that there is a difference in depth of the interface between gravel and the limestone. The interface is between 0.4 and 1.4 meter higher in the boreholes.

- With the volume percentage, shape and color of the cherts two members of the Maastricht Formation are recognized. These are the Emael and the Gronsveld. The Emael is based on the pipe shaped cherts found in MB-02, MB-03 and MB-04. The color of the cherts (light grey) match with the literature (Felder & Bosch 2000, p. 83). The Gronsveld was based on the color of the cherts. Brown-grey cherts can be from the Gronsveld member or from the Valkenburg member.

- Based on results from the XRF we conclude that the Valkenburg member is not reached. The

Valkenburg limestone has a high SiO2 content (15.2%). From the XRF the highest percentage measured for silica is 12% in borehole MB-02 at 26 meter. In MB-04 at depth 21.95 meter the percentage is approximately 7%, which means that there is not enough data to draw the conclusion that the Valkenburg member is reached. If the Emael and Gronsveld are recognized, probably the Schiepersberg must be in between. In the cores no fossil debris layers (transition zones) were seen. There is a possibility that the sea was very rough at certain locations and the fossil debris layers were washed away (Bjorn Vink, personal communication, June 2012).

From the results mentioned earlier, the authors of this thesis can conclude that the cores were drilled from the Emael to the Gronsveld member, but the transitions from the Emael to the Schiepersberg and from the Schiepersberg to the Gronsveld are not found.

Recommendation

For further research some other tests can be considered. Make thin sections of the samples to get a better understanding of the mineral content and grain size. For a better view of the structure of the limestone, micro-ct scans can be made. More XRF measurements can be done on samples in powder form. XRD-analyses could be conducted to be sure that the sulfur content is from gypsum. Considering the fact that very few macro-fossils were found, a thorough investigation of the micro-fossils is recommended, to characterize the members of the Maastricht Formation found in Valkenburg.

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References Bless, M.J.M. et al. (1981). Mededelingen rijks geologische dienst volume 35-15. Preliminary report on lower tertiary-upper cretaceous and Dinantien-Famennien rocks in boreholes heugem-1/1a and kastanjelaan-2 (Maastricht, the Netherlands). Crain, E.R. Crain’s Petrophysical handbook. Dreesen, R. & Dusar, M. (2004). Historical building stones in the province of Limburg (NE ): role of petrography in provenance and durability assessment. Elling, R. et al (2004). Rapportagetechniek. Groningen: Wolters-Noordhof bv. Felder, W.M. & Bosch, P.W. (2000). Krijt van Zuid-Limburg. Rotterdam: PlantijnCasparie. Glover, P. Petrophysical Msc course notes. Goodman, R.E. (1989). Introduction to Rock Mechanics. 2e edition. Inpijp-Blokpoel Ingeniuersbureau (2011). GeoControl Notitie M0115. Geologie van de kalksteen- ondergrond ter plaatse van de nieuwbouw van het centrumplan in Valkenburg. Jäger, M. (1987). Campanian-Maastrichtian serpulids from Thermae 2000 borehole (Valkenburg a/d geul, the Netherlands). Molenaar, N. & Zijlstra, J.J.P. (1996). Differential early diagenetic low-Mg calcite cementation and rhytmic hardground development in Campanian-Maastrichtian . Ngan-Tillard, D.J.M., Verwaal, W., Mulder, A., Engin, H.K.,Ulusay, R. (2011). Application of the needle penetration test to a calcarenite, Maastricht, the Netherlands. Ngan-Tillard, D.J.M., Mulder, A. (2012). Logging of Valkenburg cores and strength determination - factual report. Stemmerik, L. et al. (2006). Shallow core drilling of the Upper Cretaceous Chalk at Stevns Klint, Denmark. http://infohost.nmt.edu/~petro/faculty/Engler370/fmev-chap7-GR.pdf http://www.ndt-ed.org/EducationResources/CommunityCollege/Radiography/Physics/xrays.htm http://ipec.utulsa.edu/Conf2006/Papers/Billingsley.L.68.pdf http://www.sp.se/en/index/services/rockmechanicaltesting/uniaxial/Sidor/default.aspx

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Appendix