DIAGENETIC HISTORY OF CARBONATES IN EAST SABAH

Rozen Revilene RaymondBachelor of Technology (Hons)Universiti Teknologi PetronasTronoh, Perak Darul Ridzuan

Email: zen.revilene@gmail.com

Abstract— During Oligocene – Miocene, there is a major tectonic deformation which cause a widespread of uplift followed by carbonate sedimentation (Gomantong Limestone Formation) when the depositional environment changed from deep to shallow marine. These onshore Gomantong Limestone formations are often isolated and only been exposed due to plantation development and quarrying activities, which lacks in detailed study done onto the carbonate in that area, particularly the diagenetic features. Therefore, this study will focus on the diagenesis of Gomantong Limestone Formation through comprehensive petrography analysis for evaluation of the fossils mineral structures, microfacies, cement stratigraphy and diagenetic features which is then followed by scanning electron microscopy (SEM) analysis and X-Ray Diffraction (XRD) analysis. The findings show that microfacies of Gomantong Limestone formations range from wackestone to boundstone, which is dominated by benthic foraminifera (Lepidocyclina sp. and Miogypsisna sp.) that deposited in open shelf to shallow marine environment. Gomantong Limestone formations had mostly undergone micritization, cementations and mechanical fracturing in shallow marine to shallow burial diagenetic environment. However, intense cementation occurred during the diagenesis of Gomantong Limestone, which resulted as poor potential of reservoir quality.

Keywords- Gomantong Limestone Formation, microfacies, diagenesis.

INTRODUCTION

1.1 BACKGROUND

Tertiary of carbonates in Southeast Asia are extensive and diverse particularly at the east side of Borneo. These carbonates deposit are some of the major hydrocarbon exploration target, including the exploration drilling that has been carried out in the Sulu Sea in offshore eastern part of Sabah (King and Morton, 1987). However, little study has been done about the onshore carbonate deposits in Sukau, East of Sabah, due to the lack of exposure in the past. The outcrops are only been exposed due to rapid plantation development and quarrying activities which made up of the Gomantong Limestone formation. The Gomantong Limestone outcrops are located in Sukau area at the Eastern Sabah, North of Borneo.

Series of isolated limestone exposures are found from the Lahad Datu Road to the proximal Kinabatangan Estuary over the distance of more than 50km, which have the trending of E-W. The limestone consist of detrital grey limestone with some been recrystallized, contain abundance of giant benthic foraminifera and also, macrofauna such as bivalves. According to Noad (2001), there might have some evidence from unpublished seismic data which is held by PETRONAS, stated that the Gomantong Limestone may continue to the offshore where it forms isolated limestone mounds occurring along the boundary between the Labang Formation and Tanjong Formation (Noad 2001). The limestone build-ups have become the exploration drilling targets for several exploration wells in the offshore Sandakan Basin area, whereby one of it has intersected the mid-Miocene reefal debris.

Understanding the diagenetic processes is important as diagenetic criteria in carbonate has accounted for many petrophysical properties and also determine its value as reservoir rock, which also are being use in the industry. Therefore, for this project, combination of various methods such as standard petrography analysis, SEM observations and XRD analysis is used for diagenetic assessment in East of Sabah.

1.2 PROBLEM STATEMENT

Due to the lack of exposure on Gomantong Limestone, there is lack of detailed study done particularly on the diagenetic features. Most of the study done only emphasis on the carbonate sedimentology, fossils and structural study at this area. Noad (2001) stated that generally the diagenesis of Gomantong Limestone is very little and restricted to recrystallized of many massive coral heads. Therefore, this study will focus on the diagenesis processes that occurred on the Gomantong Limestone Formation.

1.3 OBJECTIVE

The objective of this project is to study the microfacies of carbonate in north east of Sabah. Besides, the

diagenetic processes that occurred in Gomantong Limestone during Miocene is being acknowledged and further relate the diagenetic processes influence towards the reservoir quality of Gomantong Limestone.

1.4 SCOPE OF STUDY

The research will be focusing in Sukau area in East Sabah. In this research, road and river traversing will be conducted to produce a detailed geological map. Rock samples were taken for thin section and petrography analysis. In the second part, the microfacies and diagenetic analysis of the formation in Sukau will be analysed to understand the diagenesis of Gomantong Limestone Formation. This project requires a high understanding on carbonate sedimentology and their applications in the field, which is in Sukau, Sabah (Figure 1).

LITERATURE REVIEW

2.1 GEOLOGICAL HISTORY

During Oligocene, the tectonic uplifting of Crocker Formation and its eastern lateral equivalent Kulapis Formation began to occur. Later in the Late Oligocene, Labang Formation started to deposit in a deep marine environment with the flysch-type deposits which obtained their sediments supply form the north western part of Labang Formation area. The source of sediments may have been derived partially from the consolidated Kulapis Formation (which is in a subaqueous environment) and partially from some igneous rocks which intruded near the source area (Chuah, 1984).

In early Miocene, major tectonic events cause the formation of mélanges, major uplift and erosion. It then followed by the change of depositional environment from deep water to shallow deltaic. Unconformity was formed and the deposition of Labang Formation ended as this basin had become shallower, and no longer conducive for flysch-type deposition. However, some of the areas were completely exposed as unconformity surface while some as shallow sea.

During Aquitanian, there is a change in source or supply of sediment from the southward and thus, the Tanjong Formation

begin to deposit in the shallow marine especially in deltaic slope to pro-deltaic environment. The tuffaceous matrix of Tanjong Formation could have also been derived from active volcanoes nearby.

A reefal complex began to form in this shallow sea near the linear shoreline after the exposed surface has subsided after Aquitanian. Furthermore, there were large foraminifera that were dwelling in the shallow warm sea between the other reefal complexes and the pro-delta can be found. It is then followed by the formation of Gomantong Limestone which is lateral equivalent to Tanjong Formation. The Gomantong Formation was relatively under a stable environment when Tanjong Formation was depositing. Nevertheless, after a complete uplift of Crocker Formation during the Middle Miocene and overthrust from the South, both of these formations ceased their depositions due to the major regional unconformity, that occurred throughout this area (Chuah, 1984).

2.2 GOMANTONG LIMESTONE FORMATION

Gomantong Limestone Formation is a shallow water coralline limestone formed in the Late Oligocene-Early Miocene period when the sudden change or shallowing of environment, due to uplift event. The outcrops are located at the north of the lower Kinabatangan River in the Sukau area of the eastern Sabah and can be dated back to Early of Miocene where there was period of progressive tectonic deformation in the fore-arc region during the subduction and widespread mélange development in Sabah. There are series of isolated exposures of limestone from East-West trending belt of steep-sided hill stretching from the Lahad Datu Road (close to the Kinabatangan River) to the East of Sukau. Bands of limestone outcrops can be found extending around 15km in a North-South direction and some can be accessed by the Sukau Road. It is argued that the limestone of Gomantong may extend to the offshore, forming isolated limestone mounds occurring along the boundary between Labang Formation and overlying Tanjong Formation (Noad, J., 2001).

2.3 TECTONIC EVOLUTION OF GOMANTONG LIMESTONE FORMATION

Lim (1985) proposed that the formation of limestone occurred at the same period as the Ayer melanges. This can be seen in the Gomantong Caves, where the Gomantong Limestone reaches approximately of 300m in thickness. This cave suggested that the Gomantong Limestone Formation is apparently overlies the Oligocene Labang Formation unconformably. A detailed study on Gomantong Limestone by Noad (2001) suggested possibility of simultaneous deposition (Figure 2) of both clastic (Labang and Kulapis Formations) and carbonate rocks (Gomantong Formations) during Oligocene to Miocene period. This can be evidenced in one of the outcrops which contains well cemented Labang clast up to 25cm in diameter which in turn suggested an unconformable contact. On the contrary, the limestone is interbedded with

Figure 1: Geological map with overview of distribution of limestone in Sukau

Figure 1: Geological map with overview of distribution of limestone in Sukau

Figure 1: Geological map with overview of distribution of limestone in Sukau

Figure 1: Geological map with overview of distribution of limestone in Sukau

Figure 1: Geological map with overview of distribution of limestone in Sukau

Figure 1: Geological map with overview of distribution of limestone in Sukau

Figure 1: Geological map with overview of distribution of limestone in Sukau

Figure 1: Geological map with overview of distribution of limestone in Sukau

several thin, grey-green fissile, clastic mudstone beds which

also contain Labang Formation clast. Several other outcrop were found to have small clastic clast or fine-grained clastic material within the limestone deposits. However, this assumptions are still remained as a question which required a further study on the litho-stratigraphy of this area.

Wong (2013) stated that there might be three hypothesis in explaining the formation of the Gomantong Limestone and mélanges as shown in Figure 3. The first hypothesis is that the limestone is deposited above the mélange. The next hypothesis is limestone being deposited together with the mélanges. The third hypothesis is stating that the limestone might deposited below mélange. However, the interpretation on the three hypothesis on Gomantong Limestone may not be

supported by enough numbers and variation of rock samples and this will be done more precisely and detailed in this project in order to confirm the diagenesis history of Gomantong Limestone formation.

METHODOLOGY

Ten outcrops are identified across the 50km road of Sukau. Throughout the area of study, field observations, sedimentary logging, sample collection and facies mapping are undertaken. Logging sections are done in some of the outcrops due to the lack of structures and less variation of facies observed at some of the outcrops. Around 30 rock samples were collected during the field work and approximately only 20 were made into thin sections.

3.1 Petrography Analysis

Lithological components, microfacies, diagenetic processes and the relative timing of diagenetic events were determined through the comprehensive petrography analysis. All samples are stained with blue dyed epoxy using the vacuum technique to facilitate the recognition of pore spaces.

3.2 Scanning Electron Microscopy (SEM)

In carbonate, SEM is use for analysis of original depositional textures (eg: characteristics of carbonate grains), structures, and secondary features generated during diagenesis. Back scattered electron mode is particularly well suited to the study of diagenetic changes brought about by both the physical and chemical diagenetic processes such as cementation and dissolution. (Krinsley, 1998).

3.3 X-RAY DIFFRACTION (XRD) ANALYSIS

XRD analysis is a used for mineral identification and to make semi quantitative estimate of the crystalline mineral components of the sediments. When X-ray radiation passes through the matter, diffraction where X-rays are emitted at a certain angles are based on the spaces between the atoms organized in crystalline structures called planes. The XRD analysis required crushed rock sample taken from the outcrop in powder form. In terms of carbonate, it is useful in differentiating the dolomite from calcite mineral which helps in detecting whether the rock sample has undergone one of the diagenesis processes known as dolomititzation.

RESULT AND DISCUSSION

4.1 Microfacies and Depositional Environment of Gomantong Limestone in Sukau

The microfacies determined throughout 10 outcrops is summarized in the Table 1. The microfacies identified ranges from wackestone to boundstone that is dominated by large

Figure 3: Chronostratigraphic section of the Oligocene-early Miocene of eastern Sabah (Noad, 2001)

Figure 2: Hypothesis of deposition of limestone in relative to melanges by Wong (2013).

Table 1: Mircrofacies of Gomantong Limestone in Sukau

Figure 2: Hypothesis of deposition of limestone in relative to melanges by Wong (2013).

Figure 2: Hypothesis of deposition of limestone in relative to melanges by Wong (2013).

Figure 2: Hypothesis of deposition of limestone in relative to melanges by Wong (2013).

Figure 2: Hypothesis of deposition of limestone in relative to melanges by Wong (2013).

Figure 2: Hypothesis of deposition of limestone in relative to melanges by Wong (2013).

Figure 2: Hypothesis of deposition of limestone in relative to melanges by Wong (2013).

Figure 2: Hypothesis of deposition of limestone in relative to melanges by Wong (2013).

Figure 3: Chronostratigraphic section of the Oligocene-early Miocene of eastern Sabah (Noad, 2001)

Figure 3: Chronostratigraphic section of the Oligocene-early Miocene of eastern Sabah (Noad, 2001)

Figure 3: Chronostratigraphic section of the Oligocene-early Miocene of eastern Sabah (Noad, 2001)

Figure 3: Chronostratigraphic section of the Oligocene-early Miocene of eastern Sabah (Noad, 2001)

Figure 3: Chronostratigraphic section of the Oligocene-early Miocene of eastern Sabah (Noad, 2001)

Figure 3: Chronostratigraphic section of the Oligocene-early Miocene of eastern Sabah (Noad, 2001)

Figure 3: Chronostratigraphic section of the Oligocene-early Miocene of eastern Sabah (Noad, 2001)

Table 1: Mircrofacies of Gomantong Limestone in SukauTable 1: Mircrofacies of Gomantong Limestone in SukauTable 1: Mircrofacies of Gomantong Limestone in SukauTable 1: Mircrofacies of Gomantong Limestone in SukauTable 1: Mircrofacies of Gomantong Limestone in SukauTable 1: Mircrofacies of Gomantong Limestone in SukauTable 1: Mircrofacies of Gomantong Limestone in Sukau

benthic foraminifera (Lepidocyclina sp. & Miogypsina sp.). The depositional environment is found to be open shelf to shallow marine. The possibility of carbonate platform formed is rimmed platform due to the presence of siliclastic clast in certain samples indicating possibility of landmass nearby or it is near the continental highland. Moreover, the abundance of large benthic foraminifera and macrofauna found shows that the circulation might be restricted in the shelf lagoon which is located landward of the shelf margin.

4.2 Diagenetic Features from Petrography Analysis

Diagenetic features of Gomantong Limestone are described in their most common sequence of occurrence as implied from the thin section petrography analysis.

4.2.1 Micritization

The micritization features can be seen as light to dark brown micritic rims to the allochem. The size of micritic rim observed are generally between 20 and 30µm. This process is almost seen in all thin sections but the area of the rim is said to be less than 2-5%. Grain micritization is observed in all thin sections. Some samples particularly from Outcrop 1 and Outcrop 2 have the micritic envelopes cemented around grains which is up to almost 40µm thick surrounding mostly benthic foraminifera (Figure 4).

Micritization is the first alteration processes which cemented almost all of the samples. Moreover, it is consider pre-date of other diagenetic features as those features cross-cut the micrite envelopes and also micritic rims to the allochems. The micritic rim found is said to be due to infilling of micro-broings that formed by endolithic organisms as the micritization mostly are encroached into the bioclasts. Micritization are abundant in wackestone-packstone and also boundstone in top of the platform. It may due to the reason of high endolithic organism activity in shallow water influenced by low to moderate energy (refer Table 2)

4.2.2 Grain Alignment, Distortion Mechanical Grain Packing, Grain Breakage & Grain Suturing

This process started by grain distortion, mechanical grain breakage and closer grain packing which is then followed by tangential and concavo-convex grain contacts, is prevalent

throughout the samples which are made up of packstone-grainstone facies. However, the degree of closeness between grain packing, grain breakage and the sutured grain contacts are highly variable between samples from different outcrops. However, majority of this diagenetic process features are noticeable at samples from packstone-grainstone found in shallow marine and forams dominated grainstone, particularly samples from Outcrop 1 and Outcrop 2.

The burial compactional features are formed after micritization. Some range of the samples shows tangential, concavo-convex and also sutured contacts which might indicates the increased burial compaction relative to sedimentation. However, there might also be influenced by the lithology-influenced. It can be seen that the closer grain contacts and leads to pressure dissolution which occur over the shallow marine to moderate burial depth (Table 4) where the depth ranges are lower than those micrite dominated

matrix samples. The grain-related compactional features are prevalent in samples which contain grains or lithology which are prone to grain breakage, and strongly affected by burial prior to cementation and lithifications.

4.2.3 Cementations (Pore Filling Cements)

The most common cements found are granular mosaic calcite (Figure 8), blocky-equant (Figure 6) and some rare poikilotopic cements (Figure 7). All of the thin sections are highly cemented, where the granular mosaic calcite and blocky equant cements occlude both the inter- and intra- granular porosity. Blocky-Equant calcite cements can be seen as equidimensional crystal up to 200µm and euhedral. number of allochems and this cements are only be observed in one thin section from Outcrop 2.

However, no pore lining cements are observed in any of the thin sections. The cementations occur after grains-related compaction and mostly are blocky-equant cements. The diagenetic of shallow marine to shallow burial environment is

Figure 5: Grain-to-grain breakage observed in thin sections

Figure 6: Pore filling equant cements

Figure 4: Micritic envelopes cemented around grainsFigure 4: Micritic envelopes cemented around grainsFigure 4: Micritic envelopes cemented around grainsFigure 4: Micritic envelopes cemented around grainsFigure 4: Micritic envelopes cemented around grainsFigure 4: Micritic envelopes cemented around grainsFigure 4: Micritic envelopes cemented around grainsFigure 4: Micritic envelopes cemented around grains

Figure 6: Pore filling equant cementsFigure 6: Pore filling equant cementsFigure 6: Pore filling equant cementsFigure 6: Pore filling equant cementsFigure 6: Pore filling equant cementsFigure 6: Pore filling equant cementsFigure 6: Pore filling equant cements

Figure 5: Grain-to-grain breakage observed in thin sectionsFigure 5: Grain-to-grain breakage observed in thin sectionsFigure 5: Grain-to-grain breakage observed in thin sectionsFigure 5: Grain-to-grain breakage observed in thin sectionsFigure 5: Grain-to-grain breakage observed in thin sectionsFigure 5: Grain-to-grain breakage observed in thin sectionsFigure 5: Grain-to-grain breakage observed in thin sections

deduced as the granular mosaic and blocky equant calcite cements post-dates most of the grains breakage events.

4.2.4 Fracturing

Fractures which refer to the microscopic fractures observed in thin sections that cross cut more than individual grains (including the grain breakages mentioned before). The relative timing of fracturing varies with every samples and some samples may have undergone several phases of fracturing. Displacement results from fracturing are rarely been observed in the thin sections. Infill of the fractures is mostly commonly by blocky-equant cements with crystal size commonly <100µm.

The fracturing occur in two major phases which form a major fractures (Figure 9) and also a smaller fractures. The fracturing is mostly related to mechanical compaction which is formed in shallow burial depth as the diagenetic environment. Fractures filled by equant blocky cements may have burial or tectonic structuration origins depending on their relative timing and later cements fills. In this case, the relative timing is said to be post-date of micritization, grain breakage and cementations processes as it crosscut all of the features. Moreover, the filling of the fractures are mostly by blocky equant cements induced that this mechanical compaction

occurred further down the shallow burial depth and may have influenced by meteoric diagenesis after the sediments undergone an uplift.

4.2.5 Dissolutions & Stylolites

Stylolites with features of continuum of jagged like to ‘anastomosing’ dissolution seams (Arosi & Wilson, 2015) are observed at certain thin sections. The stylolites are mostly

postdate all other diagenetic features. Stylolites observed are mostly bed parallel and also some occur as circum-clast stylolites as seen in thin sections from Outcrop 2 (Figure 10). The stylolites and dissolution seams can be spotted as dark brown-black color. Stylolites which is the chemical compaction features post-date all the other diagenetic features based on the cross-cutting relationships. This features are

mostly form in moderate to deep burial environments.4.3 SEM results.

The SEM result show the presence of blocky equant cements which is the dominance cement types that filled up the pores and also fractures.

4.4 XRD analysis

XRD analysis was carried out to confirm the mineral constituents in the Gomantong Limestone formation and also to examine the possibility of dolomite presence in the rock samples. For this analysis, 4 powered form samples were submitted for the test. Based on the result from XRD analysis, most of the peaks from the diffraction are produced from the calcite mineral. This shows that the dominant minerals in the limestone is made of calcite and no presence of magnesium is found. It can be implied that all the samples do not have any dolomite or affected by any dolomitization processes.

4.5 Diagenetic Environment

From petrographical observations & geochemical analysis, the following diagenetic sequence with its relative diagenetic environment is proposed (Table 2). These studies reveal that

Figure 11: SEM image of blocky equant cements

Figure 9: Fractures crosscutting skeletal grains and other diagenetic features

Figure 8: Granular Mosaic Calcite infilling Intergranular Pores

Figure 7: Poikilotopic cements on upper left.

Figure 10: Stylolites due to chemical compactionFigure 10: Stylolites due to chemical compactionFigure 10: Stylolites due to chemical compactionFigure 10: Stylolites due to chemical compactionFigure 10: Stylolites due to chemical compactionFigure 10: Stylolites due to chemical compactionFigure 10: Stylolites due to chemical compactionFigure 10: Stylolites due to chemical compaction

Figure 9: Fractures crosscutting skeletal grains and other diagenetic features

Figure 9: Fractures crosscutting skeletal grains and other diagenetic features

Figure 9: Fractures crosscutting skeletal grains and other diagenetic features

Figure 9: Fractures crosscutting skeletal grains and other diagenetic features

Figure 9: Fractures crosscutting skeletal grains and other diagenetic features

Figure 9: Fractures crosscutting skeletal grains and other diagenetic features

Figure 9: Fractures crosscutting skeletal grains and other diagenetic features

Figure 11: SEM image of blocky equant cements

Figure 11: SEM image of blocky equant cements

Figure 11: SEM image of blocky equant cements

Figure 11: SEM image of blocky equant cements

Figure 11: SEM image of blocky equant cements

Figure 11: SEM image of blocky equant cements

Figure 11: SEM image of blocky equant cements

there are two main phases of diagenesis have affected the Gomantong Limestone Formation in Sukau; i) Pervasive shallow marine micritization and cementation, followed by ii) Moderate burial of fractures by mechanical compaction and deep burial chemical compactions and cementation. The diagenesis of Gomantong Limestone Formation is similar to other Tertiary platforms from neighboring island of Borneo such as Tonasa Platform which shows limited early diagenesis

(marine or meteoric) together with prevalent of neomorphism, compaction and cementations that is related to shallow to deeper burial diagenesis (Saller and Vijaya, 2002; Madden and Wilson, 2013; Arosi and Wilson, 2015).

4.6 Reservoir Quality

Diagenesis comprises a wide spectrum of geochemical, physical and biological post deposition events where the original sedimentary mineral assemblages and their interstitial pore waters interact in attempt to reach the textural and thermodynamic equilibrium with their environment (Worden and Burley, 2003). The porosity for the Gomantong Limestone generally decreases with the increasing depth due to compaction process. However, deep in burial diagenetic settings which also can cause dissolution between bioclasts can enhanced the porosity (Figure 12).

CONCLUSION

Ten outcrops have been investigated throughout Sukau where detailed field observations are recorded with selective of samples collection in each of the outcrop. Gomantong Limestone formations are generally well preserved and variation of lithofacies can be observed throughout the outcrops in Sukau. Post field trip is then followed by lab analysis comprising petrography analysis, scanning electron microscopy (SEM) and also X-Ray Diffraction analysis. Through the 23 thin sections done, microfacies of each of the outcrop is determined. It is found that the microfacies ranges from wackestone to packstone-grainstone, and boundstone. Moreover, the microfacies generally indicate depositional environment of open shelf to shallow marine where abundance of benthic foraminifera (mostly Lepidocyclina sp. and Miogypsina sp.) are found. Furthermore, the diagenetic processes and environment is determined through detailed petrography analysis which is supported by SEM and XRD analysis results. The diagenesis processes in Gomantong Limestone are mostly minimal due to the lack of sub-aerial exposure and restricted to shallow marine and also burial diagenetic environment. It is found that there is little variation of cements with dominant of blocky-equant cements type. Moreover, over 90% of the sample are seen with fractures indicating the shallow burial effects or tectonic activity. The potential of reservoir for Gomantong Limestone are very low due to the high cementations. However, a sample from outcrop 6 shows enhancement of reservoir quality where the dissolution processes created pores within the samples.

In conclusions, the microfacies, depositional environment and diagenetic history and also the effects of diagenesis on the reservoir quality of Gomantong Limestone Formation in Sukau have been understood.

FURTHER STUDY

Stable isotope analysis should be conducted to further reconfirm the proposed diagenetic history of Gomantong Limestone Formation in this study. Most of the thin sections are fractured and the fractures are crosscutting all other diagenetic features indicating the most recent events. Therefore, it is proposed to conduct a detailed study on relating the tectonic events and eustatic changes on the diagenetic features of the Gomantong Limestone Formation.

ACKNOWLEDGMENT

I would like to thank my supervisor, Ms Sara Bashah and Mrs. Norsyawani Zaini for the opportunity to conduct this study and their guidances and supports they provided throughout the course of my final year project. My sincere appreciation also goes to Mr Choong Chee Meng and Mrs Siti Nur Fathiyah Jamaludin for their advices and helpful comments on my works. Not to forget, my gratitude to all the lab technologists in assisting me with the lab works. Last but not least, I would like to thank all my family and friends for their endless moral support.

Table 2: Summary of Diagenetic Features and Diagenetic

Figure 12: Dissolution enhanced porosity in sample from Outcrop 6

Table 2: Summary of Diagenetic Features and Diagenetic Table 2: Summary of Diagenetic Features and Diagenetic Table 2: Summary of Diagenetic Features and Diagenetic Table 2: Summary of Diagenetic Features and Diagenetic Table 2: Summary of Diagenetic Features and Diagenetic Table 2: Summary of Diagenetic Features and Diagenetic Table 2: Summary of Diagenetic Features and Diagenetic

Figure 12: Dissolution enhanced porosity in sample from Outcrop 6

Figure 12: Dissolution enhanced porosity in sample from Outcrop 6

Figure 12: Dissolution enhanced porosity in sample from Outcrop 6

Figure 12: Dissolution enhanced porosity in sample from Outcrop 6

Figure 12: Dissolution enhanced porosity in sample from Outcrop 6

Figure 12: Dissolution enhanced porosity in sample from Outcrop 6

Figure 12: Dissolution enhanced porosity in sample from Outcrop 6

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