Applied Palynology: Multidisciplinary Case Studies from Egypt, Gulf of Mexico and USA

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Applied palynology: Multidisciplinary case studies from Egypt, Gulf of Mexico and USA

Mohamed K. Zobaa

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Recommended Citation Zobaa, Mohamed K., "Applied palynology: Multidisciplinary case studies from Egypt, Gulf of Mexico and USA" (2011). Doctoral Dissertations. 2011. https://scholarsmine.mst.edu/doctoral_dissertations/2011

This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. APPLIED PALYNOLOGY: MULTIDISCIPLINARY CASE STUDIES FROM

EGYPT, GULF OF MEXICO AND USA

MOHAMED KAMAL ZOBAA

A DISSERTATION

Presented to the Faculty of the Graduate School of the

MISSOURI UNIVERSITY OF SCIENCE AND TECHNOLOGY

In Partial Fulfillment of the Requirements for the Degree

DOCTOR OF PHILOSOPHY

GEOLOGY AND GEOPHYSICS

2011

Approved by

Francisca E. Oboh-Ikuenobe, Advisor Mohamed G. Abdelsalam Robert C. Laudon J. David Rogers Michael S. Zavada Mohamed I. Ibrahim

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ABSTRACT

Various applications of palynology have been used to study case studies from four different parts of the world, namely northern Egypt, offshore Gulf of Mexico, eastern Tennessee (USA), and New Orleans, Louisiana (USA). In these case studies, palynomorphs (spores, pollen, dinoflagellate cysts, and algae) have been utilized to define zones of hydrocarbon potential, reconstruct paleoenvironmental and paleoclimatic conditions, constrain the ages of the studied rock sequences, and express its potential as a replacement proxy for some expensive organic geochemical analyses. The ability to detect past hurricane activities and their associated damage to the geologic record is here presented as a new application of palynology. The studied section from northern Egypt is Cenomanian to Turonian in age and records fluctuations between shallower and deeper marine conditions. The effect of these fluctuations was observed on the organic matter composition which alternates between oil and gas source rock intervals. The Cenomanian/Turonian oceanic anoxic event was identified within the Abu Roash “F” member. Palynofacies analysis of the offshore Gulf of Mexico section (DSDP Leg 10) enabled the recognition of two distinctive palynofacies units of mature organic matter content. The lower unit contained abundant terrestrial constituents indicative of kerogen type III (gas-prone material), while the upper unit was made up of marine components indicative of type II kerogen (oil-prone material). Palynomorphs, palynofacies, and geochemical analyses of the Gray Fossil Site, eastern Tennessee suggested the presence of asynchronous sub-basins with variable basin-fill histories. A Paleocene−Eocene age was proposed for the studied section based on palynomorphs. Recorded flora consisted primarily of Oak– Hickory–Pine woodland, with an herb/shrub understory. Palynologic analysis backed up by 14C dating of samples from New Orleans, Louisiana revealed an anomalous fossil record that is likely related to a catastrophic event that occurred ~6000 years ago. This was construed to represent a marine surge associated with increased runoff during a major hurricane activity. iv

ACKNOWLEDGMENTS

First and foremost, all praise and thanks be to ALLAH, the LORD of all that exists. It is only by HIS grace and guidance this work was accomplished. HE facilitated wonderful people who have greatly helped me throughout the various steps of this project. “And my guidance cannot come except from ALLAH; in HIM I trust and unto HIM I repent” (Quran 11:88). “And whatever of blessings and good things you have, it is from ALLAH” (Quran 16:53). Deep gratitude is expressed to Dr. Francisca Oboh-Ikuenobe, my principal advisor, for all what she has done for me. Her continuous support, academically, socially, and financially, has always pushed me forward in my career. I’m also very thankful to my other PhD committee members who have been very supportive and cooperative especially when it comes to administrative issues. The financial support received from the Department of Geological Sciences and Engineering has made it possible for me to successfully pursue and complete this project. The faculty members in the department have significantly contributed to my knowledge and my scientific personality through our daily interactions and courses I took with them. It is not possible to acknowledge all the people who have helped me in the course of finishing this project. However, I feel that the following people must be mentioned: Carlos Sanchez Botero, Cassandra Browne, Janet Raymer, Ahmed Elsheikh, Elamin Ismail, Carrie Bender, Ashley Shockley, Graham Cooke, Yu-Sheng Liu, Thomas Demchuk, Ron Waszczak, Eric Michael, Katherine Mattison, Patricia Robertson, Paula Cochran, and Vicki Hudgins. Last but not least, I’m so grateful to my late father, mother, wife, and family for being encouraging and sympathetic. Their patience and understanding have always strengthened me and helped me stay on track. Without their support it would have been very difficult to achieve any of my career goals. v

TABLE OF CONTENTS Page

ABSTRACT ...... iii ACKNOWLEDGMENTS ...... iv LIST OF ILLUSTRATIONS ...... viii LIST OF TABLES ...... x SECTION 1. INTRODUCTION ...... 1 2. KEROGEN AND PALYNOMORPH ANALYSES OF THE MID-CRETACEOUS BAHARIYA FORMATION AND ABU ROASH “G” MEMBER, NORTH WESTERN DESERT, EGYPT ...... 3

2.1. ABSTRACT ...... 3 2.2. INTRODUCTION ...... 3 2.3. STRATIGRAPHIC SETTING ...... 5 2.4. METHODS ...... 7 2.5. PALYNOSTRATIGRAPHY ...... 8 2.6. PALYNOFACIES AND PALEOENVIRONMENTAL RECONSTRUCTION ...... 12 2.7. HYDROCARBON POTENTIAL ...... 14 2.8. CONCLUDING REMARKS ...... 14 2.9. ACKNOWLEDGMENTS ...... 14 2.10. REFERENCES ...... 15 3. THE CENOMANIAN/TURONIAN OCEANIC ANOXIC EVENT IN THE RAZZAK FIELD, NORTH WESTERN DESERT, EGYPT: SOURCE ROCK POTENTIAL AND PALEOENVIRONMENTAL ASSOCIATION ...... 19

3.1. ABSTRACT ...... 19 3.2. INTRODUCTION ...... 19 3.3. MATERIAL AND METHODS ...... 23 3.4. RESULTS ...... 24 3.5. DISCUSSION ...... 28 3.5.1. C/T Oceanic Anoxic Event (OAE2) ...... 28 3.5.2. Source Rock Potential ...... 29 3.5.3. Paleoenvironmental Reconstruction ...... 31 vi

3.6. CONCLUSIONS ...... 33 3.7. ACKNOWLEDGMENTS ...... 33 3.8. APPENDIX ...... 34 3.9. REFERENCES ...... 34 4. TWO OIL AND GAS SOURCE ROCK ZONES AT THE YUCATAN PLATFORM, GULF OF MEXICO: A PALYNOFACIES STUDY OF THE DSDP LEG 10 (SITE 94) ...... 40

4.1. ABSTRACT ...... 40 4.2. INTRODUCTION ...... 40 4.3. PALYNOFACIES ANALYSIS ...... 42 4.4. PALEOENVIRONMENTAL INTERPRETATION ...... 44 4.5. CONCLUSIONS ...... 47 4.6. ACKNOWLEDGMENTS ...... 47 4.7. REFERENCES ...... 47 5. PALYNOLOGY AND PALYNOFACIES ANALYSES OF THE GRAY FOSSIL SITE, EASTERN TENNESSEE: THEIR ROLE IN UNDERSTANDING THE BASIN-FILL HISTORY ...... 48

5.1. ABSTRACT ...... 48 5.2. INTRODUCTION ...... 48 5.3. METHODS ...... 50 5.4. SEDIMENTOLOGY ...... 51 5.5. PALYNOLOGICAL ANALYSIS AND AGE DATING...... 53 5.6. PALYNOFACIES ANALYSIS ...... 61 5.7. PAST VEGETATION AND PALEOENVIRONMENTAL RECONSTRUCTION .. 62 5.8. DIACHRONOUS BASIN-FILL HISTORY...... 64 5.9. CONCLUSIONS ...... 68 5.10. ACKNOWLEDGMENTS ...... 70 5.11. APPENDIX ...... 70 5.12. REFERENCES ...... 72 6. INNOVATIVE PALYNOLOGICAL APPROACH TO DETECT PAST HURRICANE ACTIVITIES: EXAMPLE FROM NEW ORLEANS, LOUISIANA (USA) ...... 77

6.1. ABSTRACT ...... 77 vii

6.2. INTRODUCTION ...... 77 6.3. METHODS ...... 79 6.4. PALYNOMORPH ANALYSIS AND DISCUSSION ...... 79 6.5. RADIOCARBON DATING ...... 81 6.6. PALEOENVIRONMENTAL AND PALEOCLIMATIC INTERPRETATION ...... 84 6.7. CONCLUSIONS ...... 86 6.8. ACKNOWLEDGMENTS ...... 86 6.9. REFERENCES ...... 86 VITA ...... 87

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LIST OF ILLUSTRATIONS Figure Page

1.1. World map illustrating the approximate locations of the study areas of the different case studies included in the present project ...... 2

2.1. Location map of the Razzak Oil Field, Western Desert of Egypt ...... 4 2.2. Lithologic log and vertical ranges of selected palynomorphs in the Razzak #7 well ...... 6

2.3. All specimens were photographed under 100× magnification ...... 9 2.4. All specimens were photographed under 100× magnification ...... 11 2.5. Percentage distribution of particulate organic matter in the sediments ...... 13 3.1. Composite location map showing: A-the position of the Razzak Field along with other major oil and gas fields in the north Western Desert, Egypt; B- global reconstruction of the Late Cretaceous (90 Ma ago) demonstrating the approximate position of the north Western Desert (modified from Blakey, 2010) ...... 20

3.2. Generalized upper cretaceous lithostratigraphic column of the Western Desert, Egypt accompanied by primary geomagnetic polarity, transgression- regression cycles, short-term sea-level changes, and anoxic events ...... 22

3.3. Composite chart illustrating the lithologic composition of the Abu Roash “G”, “F”, and “E” members in the Razzak #7 oil well, the percentage distribution of particulate organic matter components, interpretation of hydrocarbon source rock potential, and the observed change in the δ13Corg and TOC profiles at the Cenomanian/Turonian boundary ...... 27

4.1. Location map of the DSDP Leg 10 (Site 94) ...... 41 4.2. Percent distribution of the different kerogen categories in the studied sequence ...... 43

4.3. Composite chart of the studied sequence showing sample positions, lithologic description, palynofacies and kerogen types, and thermal maturity . 45

4.4. Tyson’s (1995) Ternary AOM−phytoclast−palynomorph plots of Palynofacies A and B with their inferred paleoenvironment of deposition ...... 46

5.1. Aerial photograph of the GFS showing the location of the Paleogene GFS–1 core (36° 23' 9.3'' N; 82° 29' 55.6'' W), as well as the Neogene GFS–2 sub- basin ...... 49

5.2. Lithologic column of the GFS–1 core ...... 58 5.3. GFS–1 petrography; A shows the bioturbated sediments from the base of the GFS–1. B and C show the irregular clay capped laminations and thin (mm- scale) graded beds, respectively ...... 59

5.4. Percent distribution of the different recognized palynomorph families in the GFS−1 section ...... 60

5.5. Occurrence of the Paleocene Caryapollenites species in the United States (orange colored states) based on Palynodata, Inc. and White (2008) ...... 61

5.6. Observed ranges of some stratigraphically important taxa in North America based on Palynodata, Inc. and White (2008) ...... 62

5.7. Percent distribution of the different types of kerogen particles in the GFS−1 section ...... 63

5.8. Elemental C/N ratios and TOC values from the GFS–1 and GFS–2 sub-basins based on the present study and Shunk et al. (2006) ...... 66

5.9. Conceptual model of the geomorphic and stratigraphic development of multiple sub-basins of different ages at the GFS ...... 69

6.1. Location map of the study area showing category 3 to 5 hurricane tracks on the state of Louisiana since 1851 (Data source: National Oceanic and Atmospheric Administration (NOAA), Coastal Services Center, 2008) ...... 78

6.2. All specimens were photographed under 100× magnification ...... 82 6.3. All specimens were photographed under 100× magnification unless otherwise mentioned ...... 83

6.4. Radiocarbon dating data and percentage distribution of selected palynomorph categories recorded from 17th Street Canal section ...... 85

Plate Page

3.1. Specimen names are followed by sample number (Kr = kerogen), England Finder reference (if applicable), and magnification ...... 25

5.I. All specimens were photographed at 100× magnification ...... 52 5.II. All specimens were photographed at 100× magnification ...... 54 5.III. All specimens were photographed at 100× magnification except photos number 9 and 10 that were photographed at 20× magnification ...... 56 x

LIST OF TABLES Table Page

3.1. Palynofacies and geochemical data presented in Fig. 3.3 ...... 34 5.1. Detailed lithologic description of the GFS–1 core ...... 70 5.2. List of the recorded palynomorphs in the present study ...... 71 5.3. Geochemical analysis data for the GFS–1 core ...... 72 6.1. Radiocarbon (14C) dating data as obtained from NOSAMS ...... 80

1. INTRODUCTION

Palynology is an important multidisciplinary branch of paleontological sciences. Its applications include determining relative ages, reconstructing paleoenvironmental and paleoclimatic conditions, identifying and correlating rock sequences with hydrocarbon potential, and estimating the degree of thermal maturation of sediments. In addition, palynology provides a good, relatively inexpensive replacement proxy with a decent degree of accuracy for some more expensive organic geochemical analyses, such as vitrinite reflectance (Ro%), numerical thermal alteration index (TAI), total organic carbon (TOC), and Rock-Eval Pyrolysis. Fossil palynomorphs exist in all kinds of depositional environments, which makes them very useful when other types of environmentally restricted fossils (e.g., foraminifera and calcareous nannoplakton) are lacking in sedimentary rocks. The aim of this project was to demonstrate various applications of palynology using case studies from four different parts of the world, namely northern Egypt, offshore Gulf of Mexico, eastern Tennessee (USA), and New Orleans, Louisiana (USA) (Fig. 1.1). In these case studies, palynology has be used to: 1) define zones of hydrocarbon potential from inferred kerogen types and thermal maturation, 2) reconstruct paleoenvironmental and paleoclimatic conditions, 3) constrain the ages of the studied rock sequences, 4) demonstrate its ability as a replacement tool for some organic geochemical analyses, and 5) introduce the capacity of palynology to detect catastrophic events in the geologic record as an innovative application of palynologic analysis. Each case study in this project will be independently presented in a separate section. Each section will contain all of its pertained data (abstract, introduction, results and discussion, conclusions, etc.). References cited will also be given separately at the end of individual sections. All sections have already been disseminated to the scientific community through two published journal articles, one conference proceeding, and conference abstracts. Detailed publication citations are given in the footnote of the first page of each section. 2

Gray Fossil Site, eastern Tennessee New Orleans, Louisiana Razzak Well # 7, north Western Desert, Egypt

DSDP Leg 10 (Site 94), Gulf of Mexico

Figure 1.1. World map illustrating the approximate locations of the study areas of the different case studies included in the present project. Image source: http://ucatlas.ucsc.edu/graphics/world.gif

2. KEROGEN AND PALYNOMORPH ANALYSES OF THE MID-CRETACEOUS BAHARIYA FORMATION AND ABU ROASH “G” MEMBER, NORTH WESTERN DESERT, EGYPT*

2.1. ABSTRACT Bahariya Formation and Abu Roash “G” member sediments in the Razzak #7 well, north Western Desert, Egypt, contain abundant kerogen and fossil palynomorphs. In this study, we examined changes in these organic components and used them to interpret paleoenvironmental conditions and biostratigraphy. Terrestrial organic components dominate the Bahariya Formation and basal Abu Roash "G" member, in particular degraded phytoclasts. Because the dinoflagellate cysts in these units are dominantly peridinioids such as Subtilisphaera, the sediments were likely deposited in nearshore, moderate to high-energy conditions. In contrast, amorphous organic matter and marine palynomorphs are more abundant in the upper part of the Abu Roash "G" member, suggesting deeper depositional conditions. The overall palynomorph composition is typical of the mid- Cretaceous "African–South American" (ASA) Microfloral Province. There is a noticeable variation in the abundance of certain palynomorph taxa such as Afropollis jardinus and trilete spores, which are fewer toward the top of the Abu Roash “G” member. This variation may be a reflection of prevailing changes in the wet/dry conditions and sea level rise.

2.2. INTRODUCTION The search for exploitable hydrocarbon reserves in Egypt began in the early 1940s (Barakat et al., 1988) and led to the discovery of several oil and gas fields in the northern part of Western Desert. This region is approximately 250,000 km2 (97,000 mi2) and is characterized by simple surface geologic features contrary to its complicated subsurface image. The Razzak Oil Field was discovered in February 1972 and is among the many fields discovered in the early 1970s in the highly

* This section was published in 2008 in the Gulf Coast Association of Geological Societies Transactions. Cite as: Zobaa, M., C. Sanchez Botero, C. Browne, F.E. Oboh-Ikuenobe, and M.I. Ibrahim, 2008, Kerogen and palynomorph analyses of the mid-Cretaceous Bahariya Formation and Abu Roash “G” member, north Western Desert, Egypt: Gulf Coast Association of Geological Societies Transactions, v. 58, p. 933−943. 4

faulted Mesozoic sedimentary basins of the Western Desert. It is located 270 km (168 mi) northwest of Cairo and 60 km (37 mi) south of the Mediterranean Sea (Fig. 2.1). The subsurface Cretaceous sediments in the Razzak Basin are considered to be potential sources for oil and gas (Shahin et al., 1986). The siliciclastic strata of the lower Cenomanian Bahariya Formation are rich in palynomorphs and have been studied at several Western Desert localities (e.g., Urban et al., 1976; Saad, 1978; Sultan and Aly, 1986; Aboul Ela and Mahrous, 1992; El Beialy, 1993a, 1993b, 1995; Schrank and Ibrahim, 1995; Ibrahim, 1996, 2002).

Figure 2.1. Location map of the Razzak Oil Field, Western Desert of Egypt.

Fewer palynological studies have been undertaken for the Upper Cretaceous carbonate-rich Abu Roash and Khoman formations (El Beialy, 1994; Schrank and Ibrahim, 1995; Ibrahim et al., 2006), which have been dated using foraminifera (Abdel-Kireem and Ibrahim, 1987; Abdel-Kireem et al., 1993, 1995). The Razzak #7 well encounters the Bahariya and Abu Roash formations (A−G members). This

paper presents preliminary palynological data for the Bahariya Formation and basal Abu Roash “G” member sediments only. The objectives of this study are to identify and document the microfloral range for pollen, spores and dinoflagellates, in addition to characterizing palynofacies from particulate organic matter (kerogen) components. Palynomorph information is used to refine biostratigraphy (palynostratigraphy) and is integrated with palynofacies to interpret paleoenvironmental conditions. A preliminary assessment of particulate organic matter types is also used to indicate the hydrocarbon potential of the sediments.

2.3. STRATIGRAPHIC SETTING The sedimentary sequence in the north Western Desert ranges in age from Cambrian to Recent and is very thick, reaching more than 3 km (1.9 mi) (Abu El Naga, 1984; Barakat et al., 1987; Hantar, 1990). The Cenomanian to Santonian succession in the region is divided mainly into two lithostratigraphic units, the Bahariya Formation and the overlying Abu Roash Formation (Fig. 2.2). Stromer (1914) and Said (1962) described the Bahariya Formation, which is variously called the Razzak Sand, Meleiha Shale, and Medeiwar Member of the Abu Subeiha Formation by prospecting hydrocarbon companies and researchers (El Gezeery and O’Connor, 1975). The formation is composed of variegated shales alternating with sandstones, siltstones and limestones. The shales are varicolored, thinly laminated, grayish green to green, calcareous and silty in part, and the siltstones and sandstones are grayish white to yellowish white, glauconitic and pyritic. These rocks represent a gradational fining upward sequence that is conformable with the overlying Abu Roash. Dated as early to middle Cenomanian (Hantar, 1990; Schrank and Ibrahim, 1995; Ibrahim, 2002), about 170 m (560 ft) of the Bahariya Formation is encountered in the Razzak #7 well (Fig. 2.2).

of selected palynomorphs in the Razzak #7 well. #7 the in Razzak selected of palynomorphs

2. Lithologic log and ranges log vertical Lithologic 2.

ure ure Fig

Norton (1967) and Robertson Research International et al. (1982) subdivided the Abu Roash Formation into seven informal members designated as A to G from top to bottom. Schlumberger (1995) later subdivided the formation into seven members equivalent to the A−G members as follows: A = Ghorab, B = Rammak, C = Abu Sennan, D = Meleiha, E = Miswag, F = Mansour, and G = Abyad. Members B, D, and F are relatively clean limestones and dolomites, while members A, C, E, and G are largely fine-grained clastics. Specifically, the Abu Roash “G” member is composed of dark gray calcareous mudstone to pale gray calcareous shale. The Abu Roash Formation is conformable with the overlying Khoman Formation and has been dated as late Cenomanian to Santonian (Hantar, 1990; Schrank and Ibrahim, 1995; Abdel-Kireem et al., 1995). The Razzak #7 well drilled through approximately 555 m (1821 ft) of the Abu Roash Formation.

2.4. METHODS Thirty-one ditch cutting samples representing the Bahariya Formation and basal Abu Roash “G” member were analyzed for this preliminary study using standard laboratory processing techniques (Traverse, 2007). Each sample was digested in hydrochloric and hydrofluoric acids to remove carbonates, silicates and fluorides from the sediments. This residue was then used to prepare a kerogen slide before further centrifuging in heavy liquid (ZnBr2), screening through 10 μm sieves, and additional slide making. Slides were scanned using transmitted light microscopes for palynomorphs and particulate organic matter. However, palynomorphs have been studied in detail (minimum 200 grains per sieved slide) in ten representative samples so far. Selected palynomorph taxa, in particular those with biostratigraphic and paleoenvironmental value, are illustrated in Figs. 2.3 and 2.4. For palynofacies analysis, 200 particulate organic matter particles (each with a minimum size of 5 μm) were point counted per kerogen slide for a subset of 13 samples; however, we have scanned all 31 kerogen samples as well as several others in the upper part of the Abu Roash “G” member. These particulate organic matter components are shown in Fig. 2.4, and percentage data are illustrated in Fig. 2.5.

Nikon polarizing microscopes and Nikon Q-Imaging MicroPublisher 3.3 RTV digital camera were used in this study. All slides are currently housed in the palynological collection at Missouri University of Science and Technology.

2.5. PALYNOSTRATIGRAPHY The Bahariya and basal Abu Roash “G” units in Razzak #7 well yield a rich, diverse and well-preserved palynomorph assemblage comprising terrestrially derived sporomorphs (spores, gymnosperm and angiosperm pollen), freshwater algae, and marine palynomorphs (dinoflagellates, acritarchs, and foraminiferal test linings). Sporomorphs dominate the overall palynomorph assemblage, accounting for approximately 60−65% of total counts. The vertical ranges within the studied section of a select group of biostratigraphically and paleoenvironmentally significant taxa are shown in Fig. 2.2; Figs. 2.3 and 2.4 illustrate photomicrographs of some of these taxa. Most of the recorded palynomorphs are long ranging and were previously recorded from Jurassic and Cretaceous strata in Egypt and elsewhere (Palynodata, 2005). However, the co-occurrence and dominance of the well-known angiosperm pollen Afropollis jardinus with other sporomorph and dinoflagellate taxa, such as Alaticolpites limai, Araucariacites australis, Cicatricosisporites orbiculatus, Classopollis torosus, Crybelosporites pannuceus, Deltoidospora spp., Elaterosporites verrucatus, Ephedripites spp., Gleichiniidites senonicus, Kallosphaeridium?, and Spheripollenites psilatus, confirm the existence of the mid-Cretaceous "African – South American" (ASA) Microfloral Province proposed by Herngreen (1974). Herngreen et al. (1996) renamed this province as Albian-Cenomanian Elaterates Province.

Figure 2.3. All specimens were photographed under 100× magnification. All names are followed by slide number (SN), England Finder reference (EF), and scale bar length. A, Cicatricosisporites sp.,

SN 121/1, EF S43/2, 22.5 μm. B, Triplanosporites sp., SN 121/1, EF U44/3, 24 μm. C, Deltoidospora mesozoica (Thiergart) Schuurman 1977, SN 115/1, EF G45/4, 22.5 μm. D, Crybelosporites pannuceus (Brenner) Srivastava 1977, SN 115/1, EF J47, 16.5 μm. E-F, Stereisporites antiquasporites (Wilson and Webster) Dettmann 1963, SN 108/1, EF U43/1, 16 μm. G, Cicatricosisporites orbiculatus Singh 1964, SN 115/1, EF N46/3, 30 μm. H, Classopollis torosus (Reissinger) Balme 1957, SN 121/1, EF R43, 30 μm. I, Circulina parva Brenner 1963, SN 115/1, EF J46, 30 μm. J, Spheripollenites psilatus Couper 1958, SN 108/1, EF P47/1, 15 μm. K, Ephedripites sp., SN 121/1, EF H39, 22.5 μm. L, Alaticolpites limai Regali et al. 1975, SN 121/1, EF P43/2, 30 μm. M, Elaterosporites verrucatus (Jardiné and Magloire) Jardiné 1967, SN 115/1, EF M46, ~17 μm. N, Afropollis jardinus (Brenner) Doyle, Jardiné, and Doerenkamp 1982, SN 115/1, EF L46/3, 30 μm. O, Pennipollis peroreticulatus (Brenner) Friis et al. 2000, SN 121/1, EF K40, 24 μm. P, Tricolpites sp., SN 115/1, EF N46/4, 26 μm.

Recovered dinoflagellates in the Bahariya Formation and basal Abu Roash “G” member include Coronifera oceanica, Cyclonephelium vannophorum, Florentinia cooksoniae, Palaeoperidinium cretaceum, and Subtilisphaera perlucida, and these also confirm this age range. However, the presence of the spore species Cicatricosisporites orbiculatus and the dinoflagellate Cyclonephelium vannophorum indicates an age not younger than middle Cenomanian for the Bahariya Formation (Palynodata, 2005). No palynostratigraphic zones are proposed in this preliminary study.

Figure 2.4. All specimens were photographed under 100× magnification. All names are followed by slide number (SN), England Finder reference (EF), and scale bar length. A, Milloudodinium sp., SN

108/1, EF H43/1, 15 μm. B, Kallosphaeridium? sp., SN 121/1, EF H39/2, 15 μm. C, Coronifera oceanica? Cookson and Eisenack emend. May 1980 , SN 108/1, EF H43, 19.5 μm. D, Florentinia sp., SN 108/1, EF O44, ~21 μm. E, Cyclonephelium vannophorum Davey 1969, SN 109/1, EF J48/3, 9 μm. F-G, Micrhystridium spp., SN 108/1, ~24.5 μm. H-I, Structured phytoclasts; H, SN 109/2kr, 7.5 μm; I, SN 109/2kr, 12 μm. J, Opaque (black) debris, SN 109/2kr, 15 μm. K, Amorphous organic matter (AOM), SN 109/2kr, 10.5 μm. L, AOM (left) and degraded and comminuted phytoclasts (right), SN 109/2kr, 15 μm. M- N, General views showing different types of particulate organic matter, SN 109/2kr, 7.5 μm. O, Foraminiferal test lining (uniserial form), SN 115/1, EF M46/3, 9 μm.

2.6. PALYNOFACIES AND PALEOENVIRONMENTAL RECONSTRUCTION Palynofacies analysis identified types of kerogen: palynomorphs, structured phytoclasts, degraded and comminuted phytoclasts, amorphous organic matter (AOM), and opaques (black debris). Unstructured and degraded phytoclasts account for 75−90% of the kerogen components in the sediments, followed by structured phytoclasts (2−12%), opaques (3−8%), AOM (1−7%), and palynomorphs (1% or less) (Fig. 2.5). We note here that the overwhelming amounts of degraded and comminuted phytoclasts cover up palynomorphs and other components on the slides. The presence of a diverse marine dinoflagellate assemblage in comparison to terrestrially derived sporomorphs in the sieved slides indicates a shallow marine depositional paleoenvironment in general for the studied sedimentary sequence. The majority of the dinoflagellates (e.g., Coronifera and Kallosphaeridium?) have short and thin processes, suggesting a near shore, moderate to high-energy paleoenvironment. This environment experienced a high input of phytoclasts. These results show that there is no discernible change in depositional environment for the Bahariya and basal Abu Roash “G” member, which is in contrast to the lagoonal environment inferred for the latter unit by Hantar (1990). Differences in interpretation may be due to prevailing local conditions within the juxtaposed basins in the Western Desert.

Figure 2.5. Percentage distribution of particulate organic matter in the sediments.

The high abundance of Afropollis indicates an arid to semi arid warm climate (Herngreen et al., 1996; Ibrahim, 2002; Mahmoud and Moawad, 2002). However, the occurrence of fern spores, mainly produced by hygrophilous plants, associated with freshwater algae suggests the possibility of local or seasonal humid conditions (Schrank and Mahmoud, 2000 ). A quick slide scan of samples from the upper part of the Abu Roash “G” member shows an increase in AOM and marine palynomorphs in comparison with samples from the lower Abu Roash “G” and Bahariya. This suggests a deepening in the marine environment upsection.

2.7. HYDROCARBON POTENTIAL Oil was discovered in the Razzak Field in seven separate reservoirs (Jurassic– upper Cenomanian) in the structure on the northeast plunging anticlinal nose of one of a series of structural highs forming the Qattara Ridge (Ezzat and Dia El Din, 1974; El Ayouty, 1990). This structure is dissected by a number of faults, both parallel to the structure and perpendicular to it, mostly without large displacement. Oil was found in the Bahariya Formation sands; a less conspicuous pay is the Abu Roash "G" dolomite unit. Our palynofacies analysis shows that type III kerogen is overwhelmingly dominant in these units, confirming results by Ibrahim (2002) in the Abu Gharadig Basin. Type III kerogen is phytoclast-rich and is considered gas- prone (Tyson, 1995). Pending total organic carbon (TOC%) analysis of the sediments will likely confirm these findings. Qualitative analysis of palynomorph colors indicates that these sediments are mature. A more detailed analysis using the Pearson (1990) color scale will be undertaken later.

2.8. CONCLUDING REMARKS This preliminary study of the Bahariya Formation and basal Abu Roash “G” member in the Razzak #7 well has documented the presence of a rich, diverse and well-preserved palynomorph assemblage characteristic of the Albian−Cenomanian Elaterates province of Herngreen et al. (1996). The depositional environment for both of the studied units was near shore, moderate to high energy with high terrestrial input. Palynofacies analysis indicates the dominance of gas-prone type III kerogen. Ongoing study of the Abu Roash “A-F” and upper “G” members will provide more robust data to enhance the interpretations made in this preliminary study.

2.9. ACKNOWLEDGMENTS We would like to thank the Egyptian General Petroleum Corporation (EGPC) for providing the samples and well log for Razzak #7 well. This study is funded by a National Science Foundation grant (OISE- 0707183) to Francisca Oboh-Ikuenobe.

2.10. REFERENCES Abdel-Kireem, M.R., and M.I.A. Ibrahim, 1987, Late Cretaceous biostratigraphy and palaeobathymetry of the Betty Well No. 1, Western Desert, Egypt, in G. Matheis and H. Schandelmeier, eds., Current research in African earth sciences: Balkema, Rotterdam, The Netherlands, p. 1157−1188.

Abdel-Kireem, M.R., A.M. Samir, E. Schrank, and M.I.A. Ibrahim, 1993,Cretaceous palaeoecology, palaeoclimatology and palaeogeography of the northern Western Desert, Egypt, in U. Thorweihe and H. Schandelmeier, eds., Geoscientific research in northeast Africa: Balkema, Rotterdam, The Netherlands, p. 375−380.

Abdel-Kireem, M.R., A.M. Samir, and M.I.A. Ibrahim, 1995, Upper Cretaceous planktonic foraminiferal zonation and correlation in the northern part of the Western Desert, Egypt: Neues Jahrbuch für Geologie und Paläontologie Abhandlungen, v. 198, p. 329−361.

Abu El Naga, M., 1984, Paleozoic and Mesozoic depocenters and hydrocarbon generating areas, northern Western Desert: 7th Egyptian General Petroleum Corporation Exploration Seminar, Cairo, p. 1−8.

Aboul Ela, N. M., and H.A. Mahrous, 1992, Albian-Cenomanian miospores from the subsurface of the north Western Desert, Egypt: Neues Jahrbuch für Geologie und Paläontologie Monatshefte, v. 10, p. 595−613.

Barakat, M.G., M. Darwish, and M.L. Abdel Hamid, 1987, Hydrocarbon source rock evaluation of the Upper Cretaceous (Abu Roash Formation), east Abu Garadig area, north Western Desert, Egypt: Ain Shams University Middle East Research Center Earth Sciences Series, Cairo, Egypt, v. 1, p. 120−150.

Barakat, M.G., M. Darwish, and M.F. Ghanim, 1988, Evolution of sedimentary environments and hydrocarbon potential of Kharita Formation (Albian) in the north Western Desert, Egypt: 9th Exploration and Production Conference, Egyptian General Petroleum Corporation, Cairo, 16 p.

El Ayouty, M., 1990, Petroleum geology, in R. Said, ed., Geology of Egypt: Balkema, Rotterdam, The Netherlands, p. 567−599.

El Beialy, S.Y., 1993a, Aptian to Cenomanian palynomorphs from the Qarun 2-1 borehole, Western Desert, Egypt: Qatar University Science Journal, v. 13, p. 152−160.

El Beialy, S.Y., 1993b, Dinoflagellate cysts and miospores from the Albian−Cenomanian sequence of the Qarun 2-1 borehole, Western Desert, Egypt: Qatar University Science Journal, v. 13, p. 301−307.

El Beialy, S.Y., 1994, Palynostratigraphy and palynofacies analysis of some subsurface Cretaceous formations in the Badr El Dein (Bed 1-1) borehole, north Western Desert, Egypt: Neues Jahrbuch für Geologie und Paläontologie Abhandlungen, v. 192, p. 133−149.

El Beialy, S.Y., 1995, Datation and palaeoenvironmental interpretation by microplankton and miospore assemblages of the Razzak Oil Field sediments, Western Desert, Egypt: Geobios, v. 28, p. 663−673.

El Gezeery, M.N., and T.E. O’Connor, 1975, Cretaceous rock units of Western Desert, Egypt: Proceedings of the 13th Annual Meeting of the Geological Society of Egypt, Cairo, 2 p.

Ezzat, M.R., and M. Dia El Din, 1974, Oil and gas discoveries in the Western Desert- Egypt (Abu Gharadig and Razzak fields): 4th Exploration Seminar, Egyptian General Petroleum Corporation, Cairo, p. 1−16.

Hantar, G., 1990, North Western Desert, in R. Said, ed., Geology of Egypt: Balkema, Rotterdam, The Netherlands, p. 293−320.

Herngreen, G.F.W., 1974, Middle Cretaceous palynomorphs from northeastern Brazil: Sciences Géologiques, v. 27, p. 101−116.

Herngreen, G.F.W., M. Kedves, L.V. Rovnina, and S.B. Smirnova, 1996, Cretaceous palynofloral provinces: A review, in J. Jansonius and D. C. McGregor, eds., Palynology: Principles and applications: American Association of Stratigraphic Palynologists Foundation, Dallas, Texas, p. 1157−1188.

Ibrahim, M.I.A., 1996, Aptian−Turonian palynology of the Ghazalat-1 well (GTX-1), Qattara Depression, Egypt: Review of Palaeobotany and Palynology, v. 94, p. 137−168.

Ibrahim, M.I.A., 2002, Late Albian–middle Cenomanian palynofacies and palynostratigraphy, Abu Gharadig-5 well, Western Desert, Egypt: Cretaceous Research, v. 23, p. 775−788.

Ibrahim, M.I.A., D. Dilcher, and S.E. Kholeif, 2006, Palynology and paleoenvironment of the Upper Cretaceous rocks from Abu Gharadig Oil Field, north Western Desert, Egypt: Geological Society of America Abstracts with Programs, v. 38, no. 7, p. 444.

Mahmoud, M.S., and A.M.M. Moawad, 2002, Cretaceous palynology of the Sanhur-1X borehole, northwestern Egypt: Revista Española de Micropaleontologia, v. 34, p. 129−143.

Norton, P., 1967, Rock stratigraphic nomenclature of the Western Desert, Egypt: General Petroleum Corporation of Egypt internal report.

Palynodata, 2005, Palynological literature information collection—Windows program: Palynodata Inc., Springfield, Massachusetts.

Pearson, D.L., 1990, Pollen/spore color “standard,” version 2: Phillips Petroleum Company Geology Branch, Bartlesville, Oklahoma.

Robertson Research International and Associated Research Consultants, 1982, Petroleum potential evaluation, Western Desert: Report prepared by Associated Research Consultants, in association with Scott Pickford and Associates Limited and Energy Resource Consultants Limited, for the Egyptian General Petroleum Corporation, Cairo, 8 vol.

Saad, S.I., 1978, Palynological studies in the Egyptian Western Desert: Umbarka IX borehole: Pollen et Spores, v. 20, p. 261−301.

Said, R., 1962, Geology of Egypt: Elsevier Publishing Company, Amsterdam, The Netherlands, 337 p.

Schlumberger (Middle East S.A.), 1995, The Western Desert: Well evaluation conference, Egypt, p. 56−71.

Schrank, E., and M.I.A. Ibrahim, 1995, Cretaceous (Aptian−Maastrichtian) palynology of foraminifera-dated wells (KRM-1, AG-18) in northwestern Egypt: Berliner Geowissenschaftliche Abhandlungen, Reihe A, v. 177, 44 p.

Schrank, E., and M.S. Mahmoud, 2000, New taxa of angiosperm pollen, miospores and associated palynomorphs from the early Late Cretaceous of Egypt (Maghrabi Formation, Kharga Oasis): Review of Palaeobotany and Palynology, v. 112, p. 167−188.

Shahin, A.N., M.M. Shehab, and H.F. Mansour, 1986, Quantitative evaluation and timing of petroleum generation in Abu Gharadig Basin, Western Desert, Egypt: 8th Exploration Conference, Egyptian General Petroleum Corporation, Cairo, p. 1−18.

Stromer, E., 1914, Die Topographie und Geologie der Strecke Gharaq-Baharije nebst Ausführungen über die geologische Geschichte Ägyptens: Bayerische Akademie der Wissenschaften Abhandlungen, Mathematisch-Physikalische, v. 26, p. 1−78.

Sultan, I.Z., and S.M. Aly, 1986, Palynological zonation of Albian−Cenomanian sediments in the northern part of the Western Desert of Egypt: Bulletin of the Faculty of Science, Alexandria University, Egypt v. 26, no. 3, p. 80−101.

Traverse, A., 2007, Paleopalynology, 2nd ed.: Springer, Dordrect, The Netherlands, 813 p.

Tyson, R.V., 1995, Sedimentary organic matter—Organic facies and palynofacies: Chapman and Hall, London, U.K., 615 p.

Urban, L.L., L.V. Moore, and M.L. Allen, 1976, Palynology, thermal alternation and source rock potential of three wells from Alamein area, Western Desert, Egypt: Proceedings of the 5th Egyptian General Petroleum Corporation Exploration Seminar, Cairo, p. 1−31.

3. THE CENOMANIAN/TURONIAN OCEANIC ANOXIC EVENT IN THE RAZZAK FIELD, NORTH WESTERN DESERT, EGYPT: SOURCE ROCK POTENTIAL AND PALEOENVIRONMENTAL ASSOCIATION*

3.1. ABSTRACT The Western Desert of Egypt is one of the world’s most prolific Jurassic and Cretaceous hydrocarbon provinces. It is one of many basins that experienced organic-rich sedimentation during the late Cenomanian/early Turonian referred to as oceanic anoxic event 2 (OAE2). The Razzak #7 oil well in the Razzak Field in the northern part of the Western Desert encountered the Upper Cretaceous Abu Roash Formation. This study analyzed 23 samples from the upper “G”, “F”, and lower “E” members of the Abu Roash Formation for palynomorphs, particulate organic matter, total organic carbon (TOC) and δ13Corg in order to identify the OAE2, determine hydrocarbon source rock potential, and interpret the depositional environment. The studied samples are generally poor in palynomorphs, but show a marked biofacies change between the lower “E” member and the rest of the studied samples. Palynofacies analysis (kerogen quality and quantity) indicates the presence of oil- and gas-prone materials (kerogen types I and II/III, respectively), and implies reducing marine paleoenvironmental conditions. Detailed carbon stable isotopic and organic carbon analyses indicate that fluctuations in the δ13Corg profile across the Abu Roash upper “G”, “F”, and lower “E” members correspond well with changes in TOC values. A positive δ13Corg excursion (~2.01‰) believed to mark the short- term global OAE2 was identified within the organic-rich shaly limestone in the basal part of the Abu Roash “F” member. This excursion also coincides with the peak TOC measurement (24.61 wt.%) in the samples.

3.2. INTRODUCTION Egypt has a very long history of oil exploration and production. It is now known that ancient Egyptians used oil from seeps for mummification and coffin protection (Schlumberger, 1995). Today, the Mesozoic strata in the Western Desert

* This section was published in 2011 in Marine and Petroleum Geology. Cite as: Zobaa, M.K., Oboh- Ikuenobe, F.E., Ibrahim, M.I., 2011. The Cenomanian/Turonian oceanic anoxic event in the Razzak Field, north Western Desert, Egypt: Source rock potential and paleoenvironmental association. Marine and Petroleum Geology. doi:10.1016/j.marpetgeo.2011.05.005 20

are among the world’s major hydrocarbon producers. The Razzak Field is located in the northernmost part of the Western Desert (Fig. 3.1), and represents one of several hydrocarbon discoveries located in this highly faulted sedimentary basin (Shahin et al., 1986).

Figure 3.1. Composite location map showing: A-the position of the Razzak Field along with other major oil and gas fields in the north Western Desert, Egypt; B-global reconstruction of the Late Cretaceous (90 Ma ago) demonstrating the approximate position of the north Western Desert (modified from Blakey, 2010).

About 70% of total world petroleum resources are concentrated in the Tethys realm where the basin is located (Ulmishek and Klemme, 1990). During the Cenomanian/Turonian (C/T), organic-rich shales, marls and limestones with TOC contents of locally up to 40% were deposited on the oxygen-deprived shelf and

slope regions across North Africa and in deep-sea basins of the adjacent oceans (Herbin et al., 1986; Lüning et al., 2004). Klemme and Ulmishek (1991) pointed out that Aptian_Turonian strata, which include layers attributed to the short-term global oceanic anoxic events OAE1a, OAE1b, and OAE2, have sourced almost one-third of the world’s hydrocarbon reserves. The Razzak #7 well penetrates the Upper Cretaceous carbonate rich Abu Roash Formation (the subject of this paper) as well as the Bahariya Formation. The Abu Roash Formation (Fig. 3.2) is subdivided into seven informal members (“G” to “A”) and was previously dated late Cenomanian to Santonian based on microfossils such as foraminifera and palynomorphs (Norton, 1967; Robertson Research International and Associated Research Consultants, 1982; Hantar, 1990; Schrank and Ibrahim, 1995; Abdel-Kireem et al., 1995, 1996). Issawi et al. (1999) stated that the Abu Roash Formation is mainly represented by a sequence of limestone with shale and sandstone interbeds that has easily recognizable and well defined members in the subsurface. “B”, “D”, and “F” members are relatively clean carbonates, while “A”, “C”, “E”, and “G” members are largely fine clastics. South of the Razzak Field, in the Abu Gharadig Field (Fig. 3.1), Khaled (1999) reported that the “G” member is composed of interbedded limestones, gray to grayish green shales, and siltstones, whereas the “E” member is made up of interbedded gray to greenish gray shales and limestones. The Abu Roash Formation conformably overlies the Bahariya Formation; and underlies the Khoman Formation where the contact is sharp lithologically and paleontologically (Fig. 3.2). The Abu Roash “G”, “F”, and “E” members are considered to be the most outstanding and prolific source rocks in the Western Desert (Schlumberger, 1995).

Figure 3.2. Generalized upper cretaceous lithostratigraphic column of the Western Desert, Egypt accompanied by primary geomagnetic polarity, transgression-regression cycles, short-term sea-level changes, and anoxic events. Lithostratigraphic units are after Schlumberger (1995). This figure was created using the TSCreator software of Lugowski et al. (2009).

Several palynological and organic geochemical studies have been published on the Abu Roash Formation at many localities in the Western Desert (Barakat et al., 1987; El Beialy, 1994, 1995; Schrank and Ibrahim, 1995; Ibrahim, 1996, 2002; Zobaa et al., 2008; Ibrahim et al., 2009; El Beialy et al., 2010). A majority of these studies have focused on the palynomorph contents, palynostratigraphy and palynofacies of the strata. However, very few of these palynological studies (Barakat et al., 1987; Zobaa et al., 2008; El Beialy et al., 2010) have addressed hydrocarbon source rock potential of the sediments. This paper focuses on the palynofacies and organic geochemistry of the Abu Roash upper “G”, “F”, and lower “E” members with the aim of identifying the OAE2 interval in the Razzak Field, which can subsequently be utilized 1) as a unique marker for correlation, and 2) in constructing a robust chronostratigraphic and/or chemostratigraphic framework for the Razzak Field. Particulate organic matter

(kerogen), palynomorph, TOC and δ13Corg analyses provide data used for interpreting source rock potential and paleoenvironmental conditions, thereby contributing to our understanding of the hydrocarbon and geological evolution of the Western Desert in general, and the Razzak Field in particular.

3.3. MATERIAL AND METHODS Twenty-three cutting samples from the Abu Roash upper “G”, “F”, and lower “E” members were processed for palynological contents and organic geochemistry. Palynological processing involved digestion of samples in hydrochloric and hydrofluoric acids to remove carbonates, silicates, and fluorides (resulting from hydrofluoric acid treatment) from the sediments (Traverse, 2007). Acid digestion was followed by preparation of kerogen slides for palynofacies analysis. The remaining residues were centrifuged in heavy liquid (ZnBr2), screened through 10 µm nylon sieves, and used to prepare additional slides to identify palynomorphs in the samples. Transmitted light microscopy was used to scan the slides for their palynological contents. Two-hundred particulate organic matter particles (each with a minimum size of 5 µm) were point counted per kerogen slide and used for

palynofacies analysis. All palynological slides and residues used for this study are stored in the palynological collection at Missouri University of Science and Technology. Carbon isotopic and TOC analyses were performed at the Stable Isotope Mass Spectrometer Laboratory, University of Florida. Samples were acidified with hydrochloric acid to remove the inorganic carbon fraction. They were then rinsed with water three times, dried at 50 °C, and ground. Percentage of the organic carbon was measured using a Carlo Erba NA1500 CNS elemental analyzer. Carbon (δ13Corg) isotope was measured using a Thermo Finnigan DeltaPlus XL isotope ratio mass spectrometer with a ConFlo III interface linked to a Costech ECS 4010 Elemental Combustion System with Zero Blank autosampler (elemental analyzer).

3.4. RESULTS The types of particulate organic matter identified are palynomorphs, phytoclasts, opaques, and amorphous organic matter (AOM) (Plate 3.1). Marine and terrestrially derived palynomorphs are mostly absent in the Abu Roash upper “G” and lower “F” members, increasing very slightly up-section (up to 2.7% in sample 49). Phytoclasts are common constituents (14.3−51.3%) of the upper “F” and lower “E” members, mainly as degraded and comminuted clasts (Fig. 3.3; Appendix Table 3.1). However, some structured terrestrial plant fragments such as cuticle, wood tracheid and cortex tissues are also preserved (Plate 3.1). Opaques (black debris) are oxidized or carbonized brownish-black to black woody tissues, and are very minor components in the studied interval.

Plate 3.1. Specimen names are followed by sample number (Kr = kerogen), England Finder reference (if applicable), and magnification. Scale bar equals 10 µm unless otherwise noted. 1-3. Coenobia of Pediastrum (a freshwater Chlorococcalean green alga of the Family

Hydrodictyaceae: 1, sample 51/1, F33/0, 100×; 2, sample 51/1, N43/0, 100×; 3, sample 50/1, L46/2, 100×. 4, 5. Compound colonies of Tetrastrum (a freshwater Chlorococcalean green alga of the Family Scenedesmaceae); sample 48/1, H40/1 and N38/0 respectively, 100×. 6. Odontochitina sp.; sample 63/1, O37/4, 40×. 7. Subtilisphaera sp.; sample 66/1, K45/1, 40×. 8. Oligosphaeridium pulcherrimum; sample 51/1, T36/0, 40×. 9. Bennettiteaepollenites minimus; sample 50/1, Q44/4, 100×. 10. Ephedripites tortuosus; sample 51/1, D28/3, 100×. 11. Ephedripites regularis; sample 64/1, P27/4, 100×. 12. Foveotricolpites sp.; sample 50/1, Q46/2, 100×. 13. Scolecodont fragment; sample 64/1, R34/0, 100×. 14. Well preserved diffused edged AOM particle; sample 66/1kr, 40×. 15, 16. Structured phytoclasts (cuticles); sample 49/1kr, 40×. 17, 18. Dark brown structured phytoclasts (tracheids); samples 50/1kr and 49/1kr respectively, 40×. 19. Opaque phytoclast; sample 49/1kr, 40×. 20. Abundant AOM facies; sample 66/1kr, 20×; scale bar equals 50 µm. 21. AOM and phytoclast facies; sample 49/1kr, 20×; scale bar equals 50 µm.

AOM comprises all particulate organic components that appear structureless at the scale of light microscopy, including bacterially derived AOM, degraded marine phytoplankton remains, and amorphous diagenetic products of macrophyte tissues (Tyson, 1995). AOM dominates the upper “G” and lower “F” members, and constitutes ≥94% of the kerogen assemblage in these sediments (Fig. 3.3; Appendix Table 3.1). An up-section decrease in AOM in the studied interval correlates with an increase in phytoclasts and palynomorphs. Detailed carbon stable isotopic and organic carbon analyses across the C/T boundary in the Razzak #7 well indicate that the δ13Corg profile fluctuations across the upper Abu Roash “G”, “F”, and basal “E” members correspond well with changes in TOC abundance (Fig. 3.3; Appendix Table 3.1). A Positive δ13Corg excursion (~2.01‰) exists in the basal part of the Abu Roash “F” member, which is also characterized by high TOC values (10.43−24.61 wt.%), and is predominantly organic-rich, black shaly limestone.

org

ion ion potential,rock of hydrocarbon source the and observed change in the

.3. Composite chart illustrating the lithologic composition of the Abu Roash “G”, “F”, and “E”

Figure Figure members in the components, interpretat Razzak #7 oil boundary. at the profiles Cenomanian/Turonian and TOC well, the percentage distribution of particulate organic matter

Palynomorph analysis revealed that the studied interval is poorly fossiliferous, as noted by previous workers (Ibrahim et al., 2009; Zobaa et al., 2009a; El Beialy et al., 2010). The few palynomorph species recovered in this study are long-ranging and did not allow for precise age dating. Moreover, Cenozoic taxa attributed to caving were common, making biostratigraphic analysis very difficult and unreliable. It was evident, however, that well preserved in-situ specimens of the freshwater green alga Pediastrum overwhelmingly outnumbered and diluted all other types of palynomorphs in the lowermost “E” member (samples 48−50). Specimens of the freshwater green alga Tetrastrum were also common within the same interval. The presence of these algae has significant implications in terms of paleoenvironmental reconstruction (discussed later). Other palynomorphs identified in the studied interval include dinoflagellate cysts such as Odontochitina sp., Oligosphaeridium pulcherrimum, Cyclonephelium sp., Subtilisphaera sp., and Florentinia sp. Pteridophytic spores, and gymnosperm and angiosperm pollen include taxa of genera such as Gleicheniidites, Triplanosporites, Bennettiteaepollenites, Ephedripites, Spheripollenites, Foveotricolpites, Psilatricolporites, and Retimonocolpites. A single scolecodont fragment was recovered in sample 64 (Plate 3.1).

3.5. DISCUSSION

3.5.1. C/T Oceanic Anoxic Event (OAE2). Oceanic anoxic events represent intervals of globally increased organic carbon sequestration associated with pervasive marine anoxia. Earth has witnessed several oceanic anoxic events during its history that have been preserved in the sedimentary record. Among these, the most prominent and best identified is the OAE2 that occurred at approximately 93.5 million years ago (Turgeon and Creaser, 2008). Several scenarios/mechanisms have been proposed to explain what actually initiated the OAE2. Some authors have attributed it to massive magmatic activity (Sinton and Duncan, 1997; Kerr, 1998; Turgeon and Creaser, 2008). Others, such as Arthur et al. (1988), have related it to

increased nutrient upwelling and high primary productivity leading to significant carbon burial and CO2 depletion. The OAE2 can be easily distinguished by a sharp positive excursion in the δ13C profile of carbonates (2−3‰) and bulk organic matter (3−6‰) (Jenkyns et al., 1994; Turgeon and Creaser, 2008). This excursion has been observed in various parts of the world and has been used as a stratigraphic tool for high-resolution correlation (Gale et al., 1993; Hasegawa, 1997).

In the Razzak #7 oil well, an abrupt positive δ13Corg excursion (~2.01‰) was identified within the basal part of the Abu Roash “F” member (sample 61; depth 1566.7 m) (Fig. 3.3). This is interpreted here to represent the OAE2 in that well and is supported by two pieces of evidence: 1) the lithologic composition of that interval is predominantly organic-rich, black shaly limestone; and 2) the corresponding increase in TOC content, with the highest measured value (24.61 wt.%) occurring at the same depth of the maximum δ13Corg shift (Fig. 3.3). Both lines of evidence suggest prevailing reducing conditions. The precise identification of the OAE2 is significant because this is the first time it has been recognized in the Razzak Oil Field, and the third time in the Western Desert (Ibrahim et al., 2009; El Beialy et al., 2010), thus providing impetus for using it as a key horizon for subsurface correlation in the Razzak Field.

3.5.2. Source Rock Potential. Source rock horizons are considered to be among the most important play elements in any hydrocarbon system. Exploration geologists always pay attention to source rock layers and meticulously study their characteristics in order to fully understand them. Among the crucial aspects studied for any source rock are the amounts of organic matter accumulated during deposition, postdepositional alterations (diagenesis), and degree of thermal maturation. These are fundamental to identifying the hydrocarbon type and potential yield of a given source rock. Palynofacies (kerogen) analysis has successfully been used to provide valuable source rock information. It has an excellent degree of accuracy when compared to instrumental geochemical analyses such as TOC, vitrinite reflectance

(Ro%), and Rock-Eval Pyrolysis (Zobaa et al., 2007, 2009a,b; El Beialy et al., 2010). Kerogen is a diagenetic product of the original organic matter preserved in the sediments as a result of increased burial under favorable conditions of temperature and pressure. Further alteration (catagenesis) converts kerogen to bitumen, which ultimately transforms into either oil or gas, depending on the type of organic matter present and the prevailing environmental alteration setting. In the present study, we primarily followed the methodology of Tyson (1993, 1995) who discussed four kerogen assemblages (I−IV) that can be routinely used to study hydrocarbon source rock potential. It is worth noting that the term kerogen refers to the dispersed particulate organic matter contained in sedimentary rocks that are resistant to the inorganic (mineral) acids HCl and HF (Tyson, 1995). Two distinct zones of kerogen material have been identified (Fig. 3.3). The lower zone occurs within the upper “G” and much of the “F” members (samples 69−55) and is AOM-rich (≥94% of the total kerogen count). This is characteristic of type I kerogen and indicates highly oil-prone materials (Tyson, 1993, 1995; Ibrahim et al., 1997; Ibrahim, 2002). Based on visual and instrumental analyses, El Beialy et al. (2010) reported that Abu Roash “F” member in the GPTSW-7 well, north Western Desert contained immature oil-prone material composed of 100% percent AOM. Their observation supports our results and suggests similar depositional conditions for the Razzak #7 and GPTSW-7 wells. The upper zone occurs within the uppermost “F” and lower “E” members (samples 54−48) and is dominated by both phytoclasts and AOM (average 63% AOM and 36% phytoclasts of the total kerogen count). Type II to III kerogen is suggested for this zone, which is indicative of oil- to gas-prone materials. We note here that Schlumberger (1995) indicated that in the Western Desert, the Abu Roash “F” member is gas-prone, which is partially supported by our findings from the Razzak #7 oil well. However, the statement by Schlumberger (1995) is an oversimplification that should be taken with caution since the Western Desert contains many basins with variable depositional, burial, and thermal histories.

Previous authors (e.g., Khaled, 1999; El Beialy et al., 2010) have documented similar findings about the “E” member in other basins within the Western Desert. TOC analysis of the sediments confirms our palynofacies findings. The highest recorded TOC value occurred within the AOM abundant lower zone (Fig. 3.3), indicating a plethora of organic matter preserved under adequately reducing conditions. This is also in agreement with Tyson (1989) who indicated that the percentage values obtained for TOC correlated well with variations in AOM abundance. There is an agreement among organic geochemists that a rock can be considered as a source of hydrocarbon if it contains more than 0.5% TOC for shales, and at least 0.3% TOC for carbonates (Hasegawa, 1997; Wood et al., 1997; Ibrahim et al., 2002). The TOC values reported here for these Abu Roash carbonates vary from a minimum of 1.10 wt.% in the lower “E” member to a maximum of 24.61 wt.% in the basal “F” member, suggesting that they contain sufficient organic matter for significant generation and expulsion.

3.5.3. Paleoenvironmental Reconstruction. Paleoenvironmental reconstruction is primarily based on kerogen composition and geochemical data. Palynomorphs, when applicable, played a secondary role in our interpretation due to their inadequate and unreliable representation in most of the analyzed samples. The upper “G” and much of the “F” members in the Razzak #7 oil well (depth 1591.1−1545.3 m) contain enormous amounts of marine AOM and are almost barren of other kerogen constituents and palynomorphs (Fig. 3.3). This argues for anoxic deep marine conditions, which are known to be advantageous for AOM preservation (Tyson, 1995). Terrestrially derived kerogen and palynomorphs were either not transported into the deeper basin, or simply masked by the large amounts of AOM. The absence of marine palynomorphs such as dinoflagellates and acritarchs can be attributed to low sedimentation rates, which promoted adequate circumstances for anaerobic microbial degradation. This consequently converted marine palynomorphs to AOM. The associated high TOC values in that interval

confirm the inferred anoxic low sediment contribution setting which allowed more organic matter to accumulate, increasing the organic/inorganic ratio of the sediments. Arthur et al. (1988) stated that the OAE2 took place during a major global sea-level rise. Since the north Western Desert, including the Razzak Field, was part of the Tethyan realm, the region most likely experienced this sea-level rise (Figs. 3.1 and 3.2). The occurrence of the OAE2 approximately in the middle of this interval (upper “G” and much of the “F”) further confirms the suggested deep marine anoxic conditions. Some studies have previously noted that the “F” member in the Western Desert was deposited under deep marine depositional conditions (Alsharhan and Abd El-Gawad, 2008; El Beialy et al., 2010). This is, however, in contrast to the shallow marine to brackish water conditions indicated by Ibrahim and Al-Saad (2000) from the Khalda-21 borehole in the Western Desert, based primarily on abundant freshwater algae Pediastrum and Scenedesmus that were not observed here from the “F” member. This could be related to different local depositional settings between the Razzak #7 oil well and the Khalda-21 borehole. The decline in AOM abundance accompanied by phytoclast enrichment in the uppermost “F” and lower “E” members (depth 1545.3−1527 m) evidently points to a change in the depositional environment. The upward decrease in TOC content, although still relatively high, confirms that change and indicates comparatively less reducing conditions. Tyson (1995) interpreted increased phytoclast contents in conjunction with moderate TOC values as being indicative of proximity to sources of terrestrial organic matter. We agree with this explanation and suggest shallower marine conditions relative to the lower part of the section. These shallower conditions might have been a result of sea-level drop, which allowed more terrestrial components (phytoclasts) to be transported deeper into the basin. This interpretation is in accordance with the global sea-level model that shows a period of sea-level fall soon after the OAE2 (Fig. 3.2). Increased terrestrial input is also clearly reflected in the palynomorph composition, as noted by the overwhelming abundance of the freshwater chlorococcalean green algae (Pediastrum and

Tetrastrum) in the uppermost part of the studied section (“E” member, depth 1533.1−1527 m). Shallow marine freshwater influenced conditions for the “E” member were earlier indicated by Khaled (1999) and Ibrahim and Al-Saad (2000).

3.6. CONCLUSIONS Palynofacies and organic geochemical analyses of 23 samples from the upper “G”, “F”, and lower “E” members of the Abu Roash Formation have yielded the following information: 1. The sediments are palynomorph-poor, especially in the upper “G” and “F” members with an assemblage of spores, gymnosperm and angiosperm pollen, freshwater algae, dinoflagellate cysts, and one scolecodont specimen. 2. AOM- and TOC-rich, oil-prone type I kerogen occurs in the upper “G” and much of the “F” members, in contrast with phytoclast- and AOM-dominated, oil- to gas-prone type II to III kerogen in the uppermost “F” and lower “E” members.

3. A positive excursion (~2.01‰) is present in the δ13Corg profile within the organic-rich black shaly limestone of the basal “F” member and coincides with the highest recorded TOC value (24.61 wt.%). It marks the short-term global OAE2, which is identified for the first time in the Razzak Field. 4. The upper “G” and most of the “F” members were deposited under deep marine anoxic conditions, whereas the uppermost “F” and lower “E” member were deposited in relatively shallower, less reducing conditions.

3.7. ACKNOWLEDGMENTS The authors would like to thank the Egyptian General Petroleum Corporation (EGPC) for providing the samples and well log for the Razzak #7 oil well. Reviews by Nicholas Harris, Associate Editor, and an anonymous reviewer have greatly improved this manuscript. This study was funded by a National Science Foundation grant (OISE-0707183) to Francisca Oboh-Ikuenobe and US-Egypt grant (OTH11- 008-001) to Mohamed Ibrahim.

3.8. APPENDIX

Table 3.1. Palynofacies and geochemical data presented in Fig. 3.3.

3.9. REFERENCES Abdel-Kireem, M.R., Samir, A.M., Ibrahim, M.I.A., 1995. Upper cretaceous planktonic foraminiferal zonation and correlation in the northern part of the Western Desert, Egypt. Neues Jahrbuch fur Geologie und Palaontologie Abhandlungen 198, 329−361.

Abdel-Kireem, M., Schrank, E., Samir, A., Ibrahim, M., 1996. Cretaceous palaeoecology, palaeogeography and palaeoclimatology of the northern Western Desert, Egypt. Journal of African Earth Sciences 22, 93−112.

Alsharhan, A.S., Abd El-Gawad, E.A., 2008. Geochemical characterization of potential Jurassic/cretaceous source rocks in the Shushan basin, northern Western Desert, Egypt. Journal of Petroleum Geology 31, 191−212.

Arthur, M.A., Dean, W.E., Pratt, L.M., 1988. Geochemical and climatic effects of increased marine organic carbon burial at the Cenomanian/Turonian boundary. Nature 335, 714−717.

Barakat, M.G., Darwish, M., Abdel Hamid, M.L., 1987. Middle East Research Center Earth Sciences Series. Hydrocarbon Source Rock Evaluation of the Upper Cretaceous (Abu Roash Formation), East Abu Garadig Area, North Western Desert, Egypt, vol. 1. Ain Shams University, Cairo, Egypt. 120−150.

Blakey, R., 2010. Global Late Cretaceous (90 Ma) Paleogeographic Map. Colorado Plateau Geosystems, Inc. http://jan.ucc.nau.edu/wrcb7/90moll.jpg.

El Beialy, S.Y., 1994. Palynostratigraphy and palynofacies analysis of some subsurface cretaceous formations in the Badr El Dein (Bed 1-1) borehole, north Western Desert, Egypt. Neues Jahrbuch fur Geologie und Palaontologie Abhandlungen 192, 133−150.

El Beialy, S.Y., 1995. Datation and palaeoenvironmental interpretation by microplankton and miospore assemblages of the Razzak oil field sediments, Western Desert, Egypt. Geobios 28, 663−673.

El Beialy, S.Y., El Atfy, H.S., Zavada, M.S., El Khoriby, E.M., Abu-Zied, R.H., 2010. Palynological, palynofacies, paleoenvironmental and organic geochemical studies on the upper cretaceous succession of the GPTSW-7 well, north Western Desert, Egypt. Marine and Petroleum Geology 27, 370−385.

Gale, A.S., Jenkyns, H.C., Kennedy, W.J., Corfield, R.M., 1993. Chemostratigraphy versus biostratigraphy: data from around the Cenomanian−Turonian boundary. Journal of the Geological Society 150, 29−32. London.

Hantar, G., 1990. North western desert. In: Said, R. (Ed.), The Geology of Egypt. Balkema, Rotterdam, The Netherlands, pp. 293−320.

Hasegawa, T., 1997. Cenomanian−Turonian carbon isotope events recorded in terrestrial organic matter from northern Japan. Palaeogeography, Palaeoclimatology, Palaeoecology 130, 251−273.

Herbin, J.P., Montadert, L., Muller, C., Gomez, R., Thurow, J., Wiedmann, J., 1986. Organic-Rich Sedimentation at the Cenomanian−Turonian Boundary in Oceanic and Coastal Basins in the North Atlantic and Tethys, vol. 21. Geological Society, London, Special Publications, pp. 389−422.

Ibrahim, M.I.A., 1996. Aptian−Turonian palynology of the Ghazalat-1 well (GTX-1), Qattara Depression, Egypt. Review of Palaeobotany and Palynology 94, 137−168.

Ibrahim, M.I.A., Abul Ela, N.M., Kholeif, S., 1997. Paleoecology, palynofacies, thermal maturation and hydrocarbon source-rock potential of the Jurassic−Lower Cretaceous sequence in the subsurface of the north Eastern Desert, Egypt. Qatar University Science Journal 17, 153−172.

Ibrahim, M.I.A., Al-Saad, H., 2000. Late Cenomanian−early Turonian low-salinity tolerant agglutinated foraminifera from the Khalda-21 borehole, Western Desert, Egypt. Neues Jahrbuch fur Geologie und Palaontologie Abhandlungen 216, 67−87.

Ibrahim, M.I.A., Al-Saad, H., Kholeif, S.E., 2002. Chronostratigraphy, palynofacies, source-rock potential, and organic thermal maturity of Jurassic rocks from Qatar. GeoArabia-Manama 7, 675−696.

Ibrahim, M., 2002. Late Albian−middle Cenomanian palynofacies and palynostratigraphy, Abu Gharadig-5 well, Western Desert, Egypt. Cretaceous Research 23, 775−788.

Ibrahim, M., Dilcher, D., Kholeif, S., 2009. Palynomorph succession and paleoenvironment in the Upper Cretaceous Abu Gharadig oil field, north Western Desert, Egypt. Micropaleontology 55, 525−558.

Issawi, B., El Hinnawi, M., Francis, M., Mazhar, A., 1999. The Phanerozoic Geology of Egypt: A Geodynamic Approach. Egyptian Geological Survey, Cairo.

Jenkyns, H.C., Gale, A.S., Corfield, R.M., 1994. Carbon-and oxygen-isotope stratigraphy of the English chalk and Italian scaglia and its palaeoclimatic significance. Geological Magazine 131, 1−34.

Kerr, A.C., 1998. Oceanic plateau formation: a cause of mass extinction and black shale deposition around the Cenomanian−Turonian boundary? Journal of the Geological Society 155, 619−626. London.

Khaled, K.A., 1999. Cretaceous source rocks at the Abu Gharadig oil-and gasfield, northern Western Desert, Egypt. Journal of Petroleum Geology 22, 377−395.

Klemme, H.D., Ulmishek, G.F., 1991. Effective petroleum source rocks of the world: stratigraphic distribution and controlling depositional factors (1). AAPG Bulletin 75, 1809−1851.

Lugowski, A., Ogg, J., Gradstein, F., 2009. TSCreator PRO software. https:// engineering.purdue.edu/Stratigraphy/tscreator/index/index.php.

Lüning, S., Kolonic, S., Belhadj, E.M., Belhadj, Z., Cota, L., Baric, G., Wagner, T., 2004. Integrated depositional model for the Cenomanian−Turonian organic-rich strata in North Africa. Earth-Science Reviews 64, 51-117.

Norton, P., 1967. Rock Stratigraphic Nomenclature of the Western Desert, Egypt (Internal Report). General petroleum Corporation of Egypt.

Robertson Research International and associated Research Consultants, 1982. Petroleum Potential Evaluation, Western Desert. Report Prepared by associated Research Consultants, in Association with Scott Pickford and Associates Limited and Energy Resource Consultants Limited, for the Egyptian General Petroleum Corporation Cairo.

Schlumberger, 1995. Well Evaluation conference, Egypt.

Schrank, E., Ibrahim, M., 1995. Cretaceous (Aptian−Maastrichtian) Palynology of Foraminifera-Dated Wells (KRM-1, AG-18) in Northwestern Egypt. Selbstverlag Fachbereich Geowissenschaften, FU Berlin.

Shahin, A.N., Shehab, M.M., Mansour, H.F., 1986. Quantitative evaluation and timing of petroleum generation in Abu Gharadig basin, Western Desert, Egypt. In: 8th Exploration Conference. Egyptian General Petroleum Corporation, Cairo, pp. 1-18.

Sinton, C.W., Duncan, R.A., 1997. Potential links between ocean plateau volcanism and global ocean anoxia at the Cenomanian−Turonian boundary. Economic Geology 92, 836−842.

Traverse, A., 2007. Paleopalynology. Topics in Geobiology, second ed. Springer, Dordrecht, Netherlands.

Turgeon, S.C., Creaser, R.A., 2008. Cretaceous oceanic anoxic event 2 triggered by a massive magmatic episode. Nature 454, 323−326.

Tyson, R.V., 1989. Late Jurassic palynofacies trends, Piper and Kimmeridge clay formations, UK onshore and northern North Sea. In: Batten, D.J., Keen, M.C. (Eds.), Northwest European Micropalaeontology and Palynology, British Micropalaeontological Society Series. Ellis Horwood, Chichester, UK, pp. 135−172.

Tyson, R.V., 1993. Palynofacies analysis. In: Jenkins, D.J. (Ed.), Applied Micropalaeontology. Kluwer Academic Publishers, Dordrecht, The Netherlands, pp. 153−191.

Tyson, R.V., 1995. Sedimentary Organic Matter: Organic Facies and Palynofacies. Chapman and Hall, London.

Ulmishek, G.F., Klemme, H.D., 1990. Depositional Controls, Distribution, and Effectiveness of World’s Petroleum Source Rocks. U.S. Geological Survey Bulletin 1931, pp. 59.

Wood, G.D., Miller, M.A., Sofer, Z., Krebs, W.N., Hedlund, R.W., 1997. Palynology, palynofacies, paleoenvironments and geochemistry of the Lower Cretaceous (pre-salt) Cocobeach group, north Gabon Subbasin, Gabon. Africa Geoscience Review 4, 481−498.

Zobaa, M., Sanchez Botero, C., Browne, C., Oboh-Ikuenobe, F.E., Ibrahim, M.I., 2008. Kerogen and palynomorph analyses of the mid-Cretaceous Bahariya Formation and Abu Roash “G” member, north Western Desert, Egypt. In: Gulf Coast Association of Geological Societies Transactions, pp. 933−943.

Zobaa, M.K., Oboh-Ikuenobe, F.E., Ibrahim, M.I., Arneson, K.K., Browne, C.M., Kholeif, S., 2009a. The Cenomanian/Turonian oceanic anoxic event in the Razzak #7 oil well, north Western Desert, Egypt: palynofacies and isotope analyses. In: 2009 GSA Annual Meeting, Abstracts with Programs, Portland, Oregon, USA, pp. 513.

Zobaa, M.K., Oboh-Ikuenobe, F.E., Zavada, M.S., 2009b. Applications of palynology for hydrocarbon exploration: case studies from Egypt, Eastern Tennessee (USA) and the Gulf of Mexico. In: AAPG Annual Convention and Exhibition, Abstract Volume, Denver, Colorado, USA, pp. 238.

Zobaa, M.K., Zavada, M.S., Whitelaw, M.J., 2007. Palynofacies analysis, source rock evaluation and organic thermal maturation of the Gray Fossil Site, Gray, Tennessee. In: Eastern Section, AAPG 36th Annual Meeting, Abstract, Lexington, Kentucky, USA, pp. 60.

4. TWO OIL AND GAS SOURCE ROCK ZONES AT THE YUCATAN PLATFORM, GULF OF MEXICO: A PALYNOFACIES STUDY OF THE DSDP LEG 10 (SITE 94)*

4.1. ABSTRACT The kerogen content and thermal maturation of samples recovered from the DSDP Leg 10 (Site 94) were studied in order to assess the hydrocarbon potential of the sediments. The studied samples cover ~126 m of section and are Middle Eocene to Early Miocene in age based on foraminifera and calcareous nannofossils. Two distinctive organic facies were recognized. Palynofacies A represents the lower part of the section and is dominated by terrestrial phytoclasts with common opaque particles. Kerogen type III (gas-prone material) is proposed for this facies. Palynofacies B occupies the upper part of the studied section. It is dominated by amorphous organic matter but has few amounts of terrestrial phytoclasts and marine phytoplankton. Kerogen type II (oil-prone material) is suggested for this facies. Exine color of bisaccate pollen grains reflects fair to good thermal maturity (2 to 2+ TAI), indicating that each palynofacies is likely to produce the corresponding hydrocarbon type.

4.2. INTRODUCTION According to the Shipboard Scientific Party (1973), Site 94 of the DSDP Leg 10 is located on the continental slope of the Yucatan platform (Fig. 4.1). It was drilled in March of 1970 under 1793 m water depth and encountered 660 m of section, from which 40 cores were taken. Logan et al. (1969) stated that the Yucatan shelf is the submerged part of a low limestone plateau that gently slopes from south to north and is bounded on the west, north, and east by extremely steep continental slopes that extend from the plateau margin to the abyssal terrains of the Gulf of Mexico and the Caribbean Sea. The Gulf of Mexico is an area noted for its pioneering hydrocarbon production, and always need better constraints on their stratigraphy, burial and

* In 2009 results from this project were presented at: the AAPG Annual Convention & Exhibition, Denver, Colorado (Abstract Volume, p. 238), and the Second International Conference on Geologic Problem Solving with Microfossils (Microfossils II), University of Houston, Houston, Texas (Abstracts with Program, p. 72). 41

thermal history, and hydrocarbon potential. In the present study, palynofacies analysis was carried out on nine samples recovered from the DSDP Leg 10 (Site 94), Gulf of Mexico. Palynological samples were prepared following the technique discussed in Section 2. The studied samples cover ~126 m of section and are Middle Eocene to Early Miocene in age based on foraminifera and calcareous nannofossils (Shipboard Scientific Party, 1973).

Figure 4.1. Location map of the DSDP Leg 10 (Site 94).

Based on description and data obtained from the Shipboard Scientific Party’s report on the Site 94, the analyzed interval can be informally subdivided into two sedimentologically variable units. The lower unit is composed of greenish white

foraminiferal, nannofossil chalky sediments that are more carbonate-rich, commonly 100% calcite. The upper unit consists of light greenish gray to very light greenish gray, strongly burrowed, and rarely vaguely laminated foraminiferal, nannofossil ooze. The main focus of the present study was on using palynofacies analysis as a proxy to evaluate and asses the hydrocarbon potential as well as the degree of thermal maturation of the studied sequence, in addition to providing insights on the paleoenvironment of deposition.

4.3. PALYNOFACIES ANALYSIS The distribution of different Kerogen components throughout the studied sequence show a clear organic facies shift from a lower terrestrially influenced organic facies to an upper strongly marine dominant facies (Fig. 4.2). Based on this shift the studied section was subdivided into two palynofacies units. Playnofacies A occurs in the lower part of the section (depth from 420.31 to 379 m) and is composed predominantly of opaques as well as structured and degraded phytoclasts. Terrestrial and marine palynomorphs were also observed in this facies as accessory constituents. Palynofacies B occupies the upper part of the section (depth from 379 to 294.5 m) and consists primarily of amorphous organic matter (AOM) with common structured and degraded phytoclasts that reached in one sample up to 36.5% of the total kerogen count. Marine palynomorphs are more represented than their terrestrial counterparts, although both of them are rare. The above mentioned data about kerogen quality and quantity were used to identify two distinctive source rock zones corresponding to the observed organic facies shift from opaque and phytoclast dominant to AOM dominant facies. Following the kerogen classification scheme of Tyson (1995), kerogen type III (gas- prone material) is interpreted for Palynofacies A, while Kerogen type II (oil-prone material) is suggested for Palynofacies B (Fig. 4.3).

Percent distribution of the different kerogen categories in categories studied the kerogen different the sequence. Percentdistribution of

2. 2.

ure 4. ure Fig

The exine colors of the recorded bisaccate pollen grains of the family Pinaceae were examined to infer the thermal maturity of the identified palynofacies zones and hence, their enclosing sediments. Pearson’s (1984) pollen/spore color standard calibrated to other organic thermal maturity parameters as presented by Traverse (2007) was utilized to theoretically estimate thermal alteration index

(TAI) and vitrinite reflectance (Ro%) (Fig. 4.3). Observed pollen colors ranged from light brown in Palynofacies A to Orange in Palynofacies B. This is corresponding to

TAI of 3- to 2+ and vitrinite reflectance (Ro%) of 0.9% to 0.5% for both Palynofacies A and B respectively (Fig. 4.3). Therefore, the studied sediments contain organic matter that is mature enough to generate their respective hydrocarbon type (oil and gas) as pointed out earlier.

4.4. PALEOENVIRONMENTAL INTERPRETATION Paleoenvironmental deductions are based primarily on the nature and composition of the recorded kerogen categories as well as their distribution throughout the studied interval. Tyson’s (1995) AOM−phytoclast−palynomorph ternary plot and its associated interpretation were adopted. The lithologic composition and the presence of other types of microfossils (foraminifera and calcareous nannofossils) as indicated by the Shipboard Scientific Party (1973) were also taken into account. The presence of different kinds of marine fossils in the studied interval indicates deposition in a marine setting in general. This is further backed up by the predominantly carbonaceous composition of these sediments. The documented organic facies shift reflects a change in the paleoenvironmental conditions with regard to sea level changes and sediment contribution to the basin.

positions, lithologic description, palynofacies description, positions, lithologic

showing sample showing

of the studied the of sequence

, and thermal maturity. thermal , and

Composite chart Compositechart

. .

ure 4.3 ure

Fig types andkerogen

Palynofacies A, which contains enormous amounts of terrestrial opaques and phytoclasts, is believed to have been deposited in a shallow marine setting proximal to active fluvial streams or channels. The AOM−phytoclast−palynomorph ternary plot of Palynofacies A (Fig. 4.4) supports this interpretation and shows that its samples occupied palynofacies fields I and II that were interpreted by Tyson (1995) as to represent highly proximal to marginal dysoxic-anoxic shelf or basin.

Figure 4.4. Tyson’s (1995) Ternary AOM−phytoclast−palynomorph plots of Palynofacies A and B with their inferred paleoenvironment of deposition.

Palynofacies B, on the other hand, contains a plethora of AOM with common opaques and phytoclasts reflecting deeper depositional setting which the terrestrial elements could not effectively reach. This may be attributed to a period of sea level rise as strongly indicated by the deep marine lithologic composition of this interval (foraminiferal and nannofossil ooze). This assumption is also confirmed by the AOM−phytoclast−palynomorph ternary plot of Palynofacies B (Fig. 4.4), which

shows that its samples occupied palynofacies field IX that was interpreted by Tyson (1995) as to represent distal suboxic-anoxic basin.

4.5. CONCLUSIONS Palynofacies analysis of the Middle Eocene−Early Miocene section of the DSDP Leg 10 (Site 94) enabled the identification of two distinctive palynofacies. Palynofacies A occupies the lower part of the section and contains kerogen type III material (gas-prone), and Palynofacies B occurs in the upper part of the section and contains kerogen type II material (oil-prone). Pollen colors suggest that the organic matter in both palynofacies units is mature enough to generate their corresponding hydrocarbon type.

4.6. ACKNOWLEDGMENTS The author wishes to thank the Integrated Ocean Drilling Program (IODP) for providing the samples necessary to conduct this project. Dr. Alfred Spreng Research Award at Missouri University of Science and Technology funded the presentation of this project at two international scientific meetings.

4.7. REFERENCES Logan, B.W., Harding, J.L., Ahr, W.M., Williams, J.D., Snead, R.G., 1969. Carbonate Sediments and Reefs, Yucatan Shelf, Mexico. AAPG Memoir 11, Tulsa, Oklahoma, pp. 1–198.

Pearson, D.L., 1984. Pollen/Spore Color “Standard”, Version 2. Phillips Petroleum Company, privately distributed.

The Shipboard Scientific Party, 1973. Site 94. DSDP 10, 195−258. doi:10.2973/dsdp.proc.10.111.1973

Traverse, A., 2007. Paleopalynology. Topics in Geobiology, second ed. Springer, Dordrecht, Netherlands.

Tyson, R.V., 1995. Sedimentary Organic Matter: Organic Facies and Palynofacies. Chapman and Hall, London.

5. PALYNOLOGY AND PALYNOFACIES ANALYSES OF THE GRAY FOSSIL SITE, EASTERN TENNESSEE: THEIR ROLE IN UNDERSTANDING THE BASIN-FILL HISTORY*

5.1. ABSTRACT The Gray Fossil Site (GFS) includes multiple karst sub-basins that are filled with lacustrine sediments. Early paleontologic work on one of the sub-basins (GFS– 2) indicates a late Miocene/early Pliocene age based on an assemblage of well- preserved vertebrate fossils. However, detailed palynological analysis of the 38.7 m deep GFS–1 core recovered from another sub-basin indicates an older age. The presence of Caryapollenites imparalis, C. inelegans and C. prodromus association suggests a Paleocene to Eocene age for the GFS–1 core section. This age is also supported by the absence of pollen of the Poaceae, the grass family that is not commonly present until the Neogene. Age constraints from palynologic data suggest that the GFS has a more complex basin-fill history than previously suspected, and that multiple depo-centers within the basin may have been periodically active through the Cenozoic. Palynofacies analysis of the GFS–1 core indicates that phytoclasts and opaques are the most abundant organic constituents and have diluted both the palynomorph population and amorphous organic matter. Two possible scenarios can account for this observation: 1) an oxidizing depositional paleoenvironment; and 2) a localized high flux of charcoal following wildfires and subsequent increased runoff.

5.2. INTRODUCTION The Gray Fossil Site (GFS) is located in Washington County, northeast Tennessee (Fig. 5.1). The site was discovered in 2000 by the Tennessee Department of Transportation during a road improvement project. Early auger coring completed at the GFS encountered a complex bedrock geometry, which included multiple deep sub-basins separated by elevated bedrock blocks (Clark et al., 2005). This was later confirmed by Whitelaw et al. (2008) who conducted a high-resolution gravity study

* This section was published in 2011 in Palaeogeography, Palaeoclimatology, Palaeoecology. Cite as: Zobaa, M.K., Zavada, M.S., Whitelaw, M.J., Shunk, A.J., Oboh-Ikuenobe, F.E., 2011. Palynology and palynofacies analyses of the Gray Fossil Site, eastern Tennessee: Their role in understanding the basin-fill history, Palaeogeography, Palaeoclimatology, Palaeoecology. 49

on the 4000 m² GFS area of the Cambro-Ordovician Knox Group carbonates. They detected the presence of 11 depo-centers (or sub-basins) that are aligned along a northwest (joint) and northeast (strike) structural trends. This pattern of karst development is common within Knox Group strata. Similar patterns of deep, near vertical, karst solution pipes formed along stratigraphic or structural trends have been reported by Redwine (1999) in these strata.

Figure 5.1. Aerial photograph of the GFS showing the location of the Paleogene GFS–1 core (36° 23' 9.3'' N; 82° 29' 55.6'' W), as well as the Neogene GFS–2 sub-basin. This image was captured before building the ETSU’s Natural History Museum at the GFS. Scale bar is approximate.

Well-preserved faunal and floral materials were recovered from the GFS during the initial roadwork and subsequent paleontological excavation remediation. One of the large sub-basins (GFS–2, Fig. 5.1) includes a lacustrine fill succession with more than 40 vertebrate taxa (Parmalee et al., 2002; Wallace and Wang, 2004) that includes the rhinoceros Teleoceras and the short-faced bear Plionarctos and a diverse assemblage of Neogene fauna, which collectively constrain the age of this

deposit to between 7–4.5 Ma (late Miocene/early Pliocene) (Wallace and Wang, 2004). Shunk et al. (2006) studied the stratigraphy of the Neogene GFS–2 sub-basin. Their primary objective was to reconstruct the paleoenvironments and paleoclimate history of northeastern Tennessee using field stratigraphic relationships, petrographic analysis, stable carbon isotope values (δ13C) of organic matter, total organic carbon (TOC), and carbon–nitrogen ratios (C/N). Their results suggest that a distinct sedimentary facies shift exists within the GFS–2 section, in which a lower organic-poor facies grades upward into the organic-rich sediments encasing the abundant vertebrate fossils. The main goal of this study is to demonstrate how palynological, palynofacies, geochemical, and sedimentological analyses can be integrated to reconstruct the complex history of asynchronous multiple sub-basins in a karst system with emphasis on vegetational history and paleoenvironment.

5.3. METHODS The GFS–1 core was lithostratigraphically described and representative facies were sampled for petrographic analysis. Twenty-eight core samples were taken at approximately one meter intervals from a 38.7 m core (GFS–1) drilled to basement. About 25 grams of clay from each sample were processed following conventional palynological techniques, which include HF and HCl digestion for silicate and carbonate removal, respectively, followed by sieving the residue at 125 µm and 10 µm to eliminate the remaining clay particles. After this step, kerogen slides were made for palynofacies studies. The residues were then oxidized using

Shultz's solution [HNO3 (conc.) + KClO3] in order to remove the unwanted organic material. The remaining organic constituents were stained with Safranin to improve appearance and contrast for the microscopic examination and photographing processes (Plates 5.I, 5.II, and 5.III). After the oxidation process, permanent slides were made for palynomorph counting and identification. Canada Balsam was used as a mounting medium for both kerogen and oxidized slides. Prepared slides were

examined in transmitted light using an Olympus BX41 microscope. A total of 200 kerogen particles and 200 palynomorph grains were counted from each scanned kerogen and oxidized slide respectively. Samples used for geochemical analyses were collected at 1 m sampling intervals, and sent to the Keck Paleoenvironmental and Environmental Stable Isotope Laboratory at the University of Kansas. Samples were dried and powdered, then treated with 10% HCl for 2 h before being rinsed several times until they reached a neutral pH. TOC, and carbon and nitrogen stable isotopes were measured using a Costech 4010 elemental analyzer (EA) in conjunction with a Thermo Finnigan MAT 253 IRMS. Samples were flash combusted at roughly 1800oC to produce various carbon and nitrogen compounds, among them, CO, CO2, NO, and

NO2. Typical R2 values are better than 0.9990, and standards used include USGS-25, USGS-26, IAEA-N1 ammonium sulfates, USGS-24 graphite, ANU Sucrose, and Atropine (Costech Analytical Technologies #031042).

5.4. SEDIMENTOLOGY The GFS-1 sediments are unlithified and appear very well-preserved with the original depositional fabric intact. The overall lithology of the section is characterized by gray to dark gray silty clays of lacustrine origin, which have a high concentration of organic material. Intermittent sand layers do exist. Strong laminations in the form of organic rich and organic poor laminae are present. These laminae occur irregularly with a variable spacing between them. Mottled massive clays occur in some areas of the cored interval. Angular gravel stringers dominated by chert and dolostone are common. Quartz sand lenses also occur. A detailed lithologic description is shown in Fig. 5.2 and Appendix Table 5.1.

Plate 5.I. All specimens were photographed at 100× magnification. Scale bar equals 10 µm. 1, 2. Ligulifloridites sp. 3-7. Asteraceae spp. These species are present in rare amounts and are believed to be younger contaminants that leaked through cracks and fractures into the studied section (cf. Fisk et al., 2009). 8. Cluster of Asteraceae grains indicating very short distance of transportation. 9. Triatriopollenites triangulus Frederiksen 1979. 10, 11. Chenopodipollis granulata (Martin) Mildenhall and Pocknall 1989. 12,

13. Chenopodipollis sp. 14, 15. Cupuliferoipollenites spp. 16. Porocolpopollenites sp. 17. Ranunculacidites sp. 18. Syncolporites marginatus Van Hoeken-Klinkenberg 1964. 19. Tricolporopollenites kruschii (Potonié) Thomson and Pflug 1953 sensu Elsik 1968. 20. Quercipollenites sp.

The GFS–1 sediments appear to intermittently shift between variable sediment types, including relatively short (decimeter-scale) intervals of thinly (mm- scale) laminated sediments, non-laminated occasionally bioturbated sediments, and quasi-laminated sediments with irregular organic-rich beds. Preliminary petrographic analysis of thin-sections indicates that the GFS–1 sediments are dominated by clastic, sand- to clay-sized material and include abundant quartz and dolostone grains, with minor amounts of feldspar (Fig. 5.3). Nearly all laminated layers are composed of individual normally sized graded beds with abundant organic materials at their bases (Fig. 5.3C). The quasi-laminated sediments tended to be irregularly graded beds or zones of partial bioturbation. Zones of non- laminated sediment are likely disturbed depositional fabric with remnant portions of the original depositional fabric (graded beds) intact (Fig. 5.3A).

5.5. PALYNOLOGICAL ANALYSIS AND AGE DATING High-resolution palynological analysis led to the recognition of 13 pollen families, 21 genera, and 32 species. In addition, one species of freshwater algae and one fungal spore species were identified (Appendix Table 5.2). There was no evidence of fern spores in the studied section. Pollen grains of the Pinaceae and Juglandaceae are of very high abundance, followed by those of the Fagaceae and Asteraceae. Other families are represented in minor proportions. There is no remarkable change in the distribution of the different recognized families, genera and species throughout the investigated core interval (Fig. 5.4). This has hindered the ability to propose palynological zonations for the studied section, although good precision age dating is still achievable.

Plate 5.II. All specimens were photographed at 100× magnification. Scale bar equals 10 µm. 1, 2. Quercoidites sp. 3, 4. Juglanspollenites nigripites Wingate and Nichols 2001. 5. Caryapollenites imparalis Nichols and Ott 1978. 6. Caryapollenites inelegans Nichols and Ott 1978. 7. Caryapollenites prodromus Nichols and Ott 1978. 8. Caryapollenites simplex (Potonie 1931) Raatz 1937. 9. Caryapollenites veripites (Wilson and Webster) Nichols and Ott 1978. 10. Cluster of

Caryapollenites indicating close proximity to source area. Such Caryapollenites clusters were occasionally recorded throughout the GFS–1 core. 11, 12. Malvacearumpollis mannanensis Wood 1986. 13. Malvacearumpollis sp. 14. Fraxinus columbiana Piel 1971. 15, 16. Corsinipollenites warrenii Frederiksen 1989. 17, 18. Pinuspollenites strobipites Wodehouse 1933. 19. Pinuspollenites sp. 20. Polygonum sp.

The GFS sediments were dated as late Miocene to early Pliocene based on an association of well-preserved vertebrate fossils (Parmalee et al., 2002; Wallace and Wang, 2004). However, the lowest stratigraphic occurrence of these vertebrates is located stratigraphically higher than the stratigraphic highest sample analyzed in the present study. Moreover, we propose that the GFS–1 core sediments were deposited under different paleoenvironmental conditions and/or in a different sub- basin based on lithologic, petrographic, and geochemical criteria (see below). In the present study, many of the recovered and identified palynomorphs have long stratigraphic ranges and cannot help constrain the age of the GFS–1 core sediments. Among these are Ulmipollenites undulosus and Cupuliferoipollenites pusillus with a known stratigraphic range of Cretaceous to Quaternary (Palynodata and White, 2008). Some of the other identified pollen grains are good markers and can be used for age determination. Nichols and Ott (1978) formally re-described the genus Caryapollenites and recognized four new species (C. prodromus, C. imparalis, C. inelegans and C. wodehousei) and one new combination species (C. veripites) from the early Paleogene (Paleocene) of the Wind River Basin, Wyoming. They also proposed six Paleocene biostratigraphic zones based on selected species of the genera Momipites and Caryapollenites. Subsequently, these five species have been recovered and identified in strata of the same age range in several locations all over the United States (Fig. 5.5). Nichols (2003) and Nichols and Ott (2006) also demonstrated the stratigraphic usefulness of these pollen as important Paleocene zonal fossils in the Rocky Mountain and Great Plains regions. Moreover, Nichols (2005) pointed out that the well-documented palynostratigraphic zones established for the Rocky

Mountain region, largely based on Caryapollenites species, are also applicable to the Gulf Coast region.

Plate 5.III. All specimens were photographed at 100× magnification except photos number 9 and 10 that were photographed at 20× magnification. Scale bar equals 10 µm for all photos except that for 9 and 10, which equals 50 µm. 1, 2. Milfordia hungarica (Kedves) Krutzsch and Vanhoorne in Krutzsch 1970. 3, 4. Periporopollenites hexaporus Macphail and Hill 1994. 5, 6. Ulmipollenites undulosus Wolff 1934. 7. Cinctiporipollis? sp. 8. Pseudoschizaea ozeanica Thiergart and Frantz 1962. 9, 10. Small equidimensional opaques and dark colored phytoclasts facies. This facies overwhelmingly dominates the studied samples.

The electronic database Palynodata and White (2008) was used to survey the previous records of these stratigraphically important Caryapollenites species as well as others with the same stratigraphic value that are recorded in the present work. The results of this comprehensive survey are summarized in Fig. 5.6. Caryapollenites imparalis has 32 records, all of them in North America, except one from the Faroe Islands in the North Atlantic. It has an age range of early Paleocene to middle Eocene (e.g., Wingate, 1983; Pocknall, 1987). Caryapollenites prodromus was recorded 24 times in North America with an age range of Late Cretaceous to middle Eocene. Edwards et al. (1999) recovered this species from the upper Paleocene of South Carolina, an age confirmed by an association of calcareous nannofossils, dinoflagellate cysts and invertebrates. It was also recorded from the middle Eocene of western Tennessee (Hackley et al., 2006). Caryapollenites inelegans has 34 records in North America and Europe, and all of them fall within a Paleocene to Eocene age range (e.g. Demchuk, 1990; Jolley and Spinner, 1991; Nichols, 2005). Other stratigraphically important taxa include Juglanspollenites nigripites, Pinuspollenites strobipites and Triatriopollenites triangulus, all of which have North American age range of early Paleocene to early Oligocene (e.g. Penny, 1969; Frederiksen, 1979; Frederiksen et al., 1983). These occur in association with Milfordia hungarica, which has even a shorter stratigraphic range of early Eocene to early Oligocene in North America (e.g., Kimyai, 1993; Oboh and Morris, 1994), but a wider age range (Late Cretaceous to late Neogene) elsewhere. In North America, fossil grass pollen did not appear in high abundance until the Miocene and became more abundant from the Miocene to present (Cerling, 2001; Retallack, 2001). The absence of this pollen group in our samples, if not due to environmental factors, supports the suggested pre-Miocene age. In summary, we believe that the studied samples are not younger than the Paleogene in general and that a Paleocene to Eocene age can be assigned to them.

Figure 5.2. Lithologic column of the GFS–1 core.

Figure 5.3. GFS–1 petrography; A shows the bioturbated sediments from the base of the GFS–1. B and C show the irregular clay capped laminations and thin (mm-scale) graded beds, respectively. These microfabrics occur at various intervals within the GFS–1.

Figure 5.4. Percent distribution of the different recognized palynomorph families in the GFS−1 section. The category “Others” includes all other families reported in Appendix Table 5.2.

Figure 5.5. Occurrence of the Paleocene Caryapollenites species in the United States (orange colored states) based on Palynodata, Inc. and White (2008).

5.6. PALYNOFACIES ANALYSIS Kerogen counting shows that small equidimensional opaques and dark colored phytoclasts overwhelmingly dominate the studied samples. Other kerogen components like amorphous organic matter (AOM) and palynomorphs are rarely represented (Fig. 5.7). The contribution of organic matter, especially opaques and phytoclasts, to GFS−1 sediments was not consistent and took place over successive cycles of varying magnitudes (Fig. 5.7). Also noticeable was the fact that palynomorphs decreased in numbers when the opaques increased. These two phenomena can be related to periodic fluctuations of the lake level that exposed bottom sediments to oxygenated surface water during low water-level periods. This could have created oxidizing conditions that reduced the abundance of palynomorphs preserved in the sediments. Other types of deposited organic matter were altered to opaques creating these repeated high opaque values as seen in Fig.

5.7. Another possible explanation is that the high opaque values represent periods of high charcoal contribution to the basin as a result of recurring wildfires in the local surrounding area which were followed by increased runoff (cf. Tyson, 1995). In this latter scenario, the associated decrease in palynomorphs may be attributed to either partial or complete burning of palynomorph-producing organs in plants, burning of the palynomorphs themselves, or palynomorph dilution by increased sedimentation.

Figure 5.6. Observed ranges of some stratigraphically important taxa in North America based on Palynodata, Inc. and White (2008).

5.7. PAST VEGETATION AND PALEOENVIRONMENTAL RECONSTRUCTION High percentages of small equidimensional opaques associated with dark brown phytoclasts of total kerogen strongly suggest oxidizing paleoenvironmental conditions. This inference is supported by the extremely low numbers of palynomorphs in relation to total kerogen; palynomorphs are less resistant to oxidizing conditions than some other kerogen components such as opaques and some types of structured phytoclasts. Observed low TOC values (Fig. 5.8), typical of oxidizing settings (Tyson, 1995), may further support the suggested oxidizing conditions. As proposed earlier, these oxidizing conditions occurred periodically

because of either fluctuating lake level or recurring wildfires, which were probably triggered by cyclic droughts.

Figure 5.7. Percent distribution of the different types of kerogen particles in the GFS−1 section.

The GFS flora is characterized by a combination of woodland with an herb/shrub understory. The absence of fern spores may be due to the prevailing oxidizing conditions, which selectively destroyed them because of their relatively low sporopollenin content (Traverse, 2007). Alternatively, predominantly dry climatic conditions may not have been favorable for fern growth.

The dominant pollen types (up to ~92%) include Pinuspollenites, Caryapollenites, Juglanspollenites, Quercipollenites, and Quercoidites (pine–hickory– oak). It is hard to know if the high frequency of Pinuspollenites species is due to actual abundance in the area, or a result of long-distance atmospheric transport (cf. de Vernal and Hillaire-Marcel, 2008). However, it is not uncommon to find clusters of large numbers of grains of Pinuspollenites, which indicates deposition more proximal to the source area(s) (c.f. Martin et al., 2009). This association indicates a southern dry–mesic woodland/savanna, which generally lacks the strong stratified forest structure of a closed canopy mesic forest (moderate moist habitat). The woodland may have had a patchy canopy as indicated from the presence of taxa that form an herbaceous layer, or are indicative of disturbed habitat (Appendix Table 5.2; Bray, 1960). This type of forest is often associated with the occurrence of fire, which may have played an important role in the GFS−1. The herb/shrub community is mainly represented by the Asteraceae, which in some samples, contributes up to ~20% of the total palynomorph count. Other rarely represented herb/shrub families are Onagraceae, Malvaceae, Oleaceae, and Restionaceae. Asteraceae and Malvaceae have almost worldwide distributions, although Asteraceae is frequently associated with disturbance, e.g., fire. Therefore, the GFS–1 flora was probably the high elevation variation of the Paleocene–Eocene seasonally dry warm temperate to cool subtropical flora recovered from western Tennessee ball clays, which were deposited in more proximal fluvial environments on the margin of the Mississippi Embayment (Dilcher, 1973).

5.8. DIACHRONOUS BASIN-FILL HISTORY Shunk et al. (2006) stratigraphically subdivided the Neogene sediments of the GFS–2 sub-basin into: i) lower graded facies composed of individual, cm-scale, normal graded beds with minimal amounts of TOC, and ii) upper laminated facies that conformably transitions into organic-rich sediments deposited as rhythmites. The lacustrine rhythmites were not size graded and were interpreted to represent annual varves corresponding to seasonal variations of sediment deposition into the

basin (Shunk et al., 2009). The lithology of the GFS–1 core does not show a similar facies change indicating that these sediments were deposited under different sedimentological and environmental conditions. Furthermore, preliminary petrographic analysis of the GFS–1 core sediments reveal that individual layers are composed of graded beds that generally vary in thickness from ~1 mm (Fig. 5.3B) to >0.5 cm (Fig. 5.3C) and are occasionally bioturbated (Fig. 5.3A). The graded beds might have formed by delivering pulses of sediments of variable amounts to the GFS–1 sub-basin over successive episodes, which argues for the cyclicity inferred earlier. Observed bioturbation may be attributed to periods of lower sediment supply under unstratified shallow lake water conditions, supporting the suggested prevailed oxidizing conditions. Unlike the individual graded beds in the Neogene GFS–2 graded facies, the GFS–1 sediments include abundant organic debris. No laminations with similar petrography or depositional fabric to the rhythmites interpreted as annual varves were discovered within the GFS–1 core, suggesting deposition under different climatic conditions as would be expected from sediments of different ages. Thus, sediment-stacking patterns and depositional fabric vary considerably between these two GFS sub-basins. The geochemical analysis of the GFS–1 and GFS–2 sub-basins vary substantially. The distinct sedimentary facies shift in the GFS–2 section is marked by a major change in the amount of TOC. The lowermost graded facies averages ~0.5 wt.% TOC, while the uppermost laminated facies averages ~8 wt.% TOC. On the other hand, the GFS–1 section has an average TOC of ~0.7 wt.% and lacks the organic-rich rhythmites present within the GFS–2 section (Fig. 5.8). In addition, C/N ratios vary considerably between the two sub-basins. The two facies present within the GFS–2 sub-basin have distinct differences in C/N ratios; the graded facies has C/N ratios averaging 2.0, whereas the laminated facies average 34.6. The C/N ratios within the GFS–1 sub-basin are intermediate between the two facies preserved within the GFS–2 sub-basin (Fig. 5.8).

Figure 5.8. Elemental C/N ratios and TOC values from the GFS–1 and GFS–2 sub-basins based on the present study and Shunk et al. (2006). A distinct facies shift is preserved in the Neogene GFS–2 section, which is characterized by a transition from a lower facies with low TOC and C/N ratios to an upper facies characterized by higher values (Shunk et al., 2006). This facies shift is not observed at GFS–1 section. It is clear that the two sub-basins were not subject to the same sedimentological and environmental conditions.

Elemental C/N ratios from sediment TOC provide useful information for reconstructing the sources of organics deposited in lacustrine paleoenvironments. Meyers (1994) indicated that in appropriate environments (not diagenetically altered), C/N ratios retain paleoenvironmental information for millions of years. C/N ratios can differentiate between organic material derived from algae and

vascular land plants because land plants include abundant support tissue that increases their C/N ratios to values above 20, whereas, algae lack abundant support tissue and typically have C/N ratios between 4 and 10. C/N ratios from the GFS−1 sub-basin indicate a dominant vascular land plant contribution, which is consistent with our palynological data. Moreover, the apparent cyclicity in the C/N curve of the GFS−1 core (Fig. 5.8) looks similar to that observed from the palynofacies curves of the same core (Fig. 5.7). This similarity is considered to be an independent evidence on the suggested episodic contribution of sediments and organic matter to the GFS−1 section. It is clear that the geochemistry and stratigraphy of the two sections collected from adjacent locations within the GFS do not correlate. Neither the organic-rich laminated facies nor the organic-poor graded facies of the GFS–2 section exists in the GFS–1 section. This conspicuous difference suggests that sedimentation into the sub-basins was not contemporaneous. Instead, each sub-basin may have received sediment from differently configured sources. Smith’s (2003) analysis of the Neogene section suggests sediment input from as far away as southwestern Virginia. C. Liutkus (personal communication, 2008) identified nine distinct sand layers in the GFS–1 core and proposed that the source may be the Cambrian Copper Ridge Formation and the Ordovician Chepultepec Formation, both of which outcrop north and northwest of the Gray Fossil Site. This suggests a much more restricted basinal input than determined by Smith for the Neogene sediments. Both sub-basins likely originated as deep karst solution cavities with varying basin geometries and fill histories. This is reasonable considering that the GFS occurs on the SE limb of a NE-SW striking syncline within the Knox Group. Redwine (1997) indicates that the Knox Group rocks represent an atypical karst host rock because: 1) solution cavities in the Knox Group rocks commonly form very deep cavities with a relatively small area compared to traditional karst basins that form in limestone; 2) the location of solution cavity formation within the Knox Group rocks is not random and cavities tend to form along faults, joints, and fold limbs; and 3) karst features are commonly

oriented at near vertical geometries. Thus, it is plausible that multiple sub-basins formed within the GFS during different time intervals when base-level (water table) dropped substantially, creating deep solution cavities that formed in a joint system created by regional folding stresses. The presence of lacustrine sediments in each basin indicates that base-level likely increased after karst development and formation. Fig. 5.9 depicts a conceptual model for the complex and diachronous geomorphic and stratigraphic development of the GFS−1 and GFS−2 sub-basins. The model suggests that the GFS−1 was opened and filled with sediments during the Paleogene (Fig. 5.9A). The GFS−2 was formed in a second interval of karst dissolution during the Neogene (Fig. 5.9B) and then filled with a second succession of lacustrine sedimentation (Fig. 5.9C).

5.9. CONCLUSIONS 1- The Gray Fossil Site is composed of multiple sinkholes/sub-basins that are believed to be asynchronous events preserving multiple basin-fill histories. 2- The GFS depositional basin changed configuration through the Cenozoic as individual sub-basins became active and were filled in a series of overprinting sinkhole events. 3- The GFS–1 core is from an independent sub-basin (karst solution pipe) that contains Paleocene–Eocene palynomorphs. Thus, it predates the late Miocene/early Pliocene GFS–2 sub-basin which was infilled with lacustrine sediments capped by fluvial deposits and paleosols, that covered and preserved the entire site. 4- The interpretation of the GFS–1 flora indicates that a periodically dry Oak– Hickory–Pine Woodland or Woodland/Savanna occupied the site during GFS–1 time. The understory was dominated by a variety of herbaceous forbs (broad-leaved herbs other than grass that grow in fields, prairies, or meadows). 5- Based on the abundance of charcoal (opaques), fire appears to have been an important disturbance factor.

Figure 5.9. Conceptual model of the geomorphic and stratigraphic development of multiple sub-basins of different ages at the GFS. A) Deep, near vertical solution cavity (GFS–1 sub-basin) forms along a fold limb and begins filling with lacustrine sediments during the Paleogene. Pollen records indicate that the Paleogene flora was characterized by a combination of southern dry–mesic woodland/savanna, with an herb/shrub understory. This type of

forest is often associated with the occurrence of fire, which may have been an important element in the GFS−1 ecosystem. B) Another deep solution cavity (GFS–2 sub-basin) forms adjacent to the previously filled cavity during a period of low base-level. C) Late Miocene/early Pliocene sediments fill the second basin.

5.10. ACKNOWLEDGMENTS Deep gratitude is expressed to Yu-Sheng Liu for giving access to his Olympus microscope. We are also thankful to Graham Cooke for his continuous help and assistance in the laboratory. Reviews from Finn Surlyk (Editor), Henrik Petersen, and an anonymous reviewer have greatly improved this manuscript.

5.11. APPENDIX

Table 5.1. Detailed lithologic description of the GFS–1 core.

Table 5.2. List of the recorded palynomorphs in the present study.

Table 5.3. Geochemical analysis data for the GFS–1 core.

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6. INNOVATIVE PALYNOLOGICAL APPROACH TO DETECT PAST HURRICANE ACTIVITIES: EXAMPLE FROM NEW ORLEANS, LOUISIANA (USA)*

6.1. ABSTRACT Palynologic analysis of samples recovered from New Orleans, Louisiana (USA) showed the presence of a mixture of fossil palynomorphs from different ages (Cretaceous to Holocene) and different paleoenvironments within a certain interval. This did not result from sampling collection error, since samples were collected carefully from a borehole drilled in 2006, in the aftermath of Hurricane Katrina. A possible long history of strong hurricanes striking the region and dramatically affecting the fossil record is proposed. Palynomorph and 14C analyses were successfully utilized to prove this hypothesis by documenting an anomalous record of fossil palynomorphs and 14C dating, in addition to its associated paleoenvironmental and paleofloristic changes.

6.2. INTRODUCTION Southern United States is a region noted for its frequent hurricane activity. In the past two decades, the state of Louisiana alone was hit by hurricanes twenty eight times; eight of them were classified as category 3 and 4 (Internet Reference 1) (Fig. 6.1). This hurricane pattern might have existed over a longer period of time in the geologic past. Moreover, it should have dramatically affected the fossil record in this region. In order to examine the validity of these hypotheses, a borehole from New Orleans, Louisiana was drilled early in 2006. Nine samples were processed to examine their fossil palynomorph content. Seventeen samples were also independently selected for 14C dating to backup the palynological analysis. The borehole is located in the east bank of the 17th Street Canal Levee just south of the Hammond Highway Bridge over the canal along Bellaire Street. It is just east of an intact translated levee fragment with a large Cypress stump nearby.

* In 2009 preliminary results from this project received the Best Student Poster Award during the 42nd Annual Meeting of the American Association of Stratigraphic Palynologists (AASP)−The Palynological Society, which was held in Kingsport, Tennessee. 78

Figure 6.1. Location map of the study area showing category 3 to 5 hurricane tracks on the state of Louisiana since 1851 (Data source: National Oceanic and Atmospheric Administration (NOAA), Coastal Services Center, 2008).

Palynology is known for its wide applications in Earth and environmental sciences. It has long been used in paleoenvironmental and paleoclimatic reconstructions. Although it showed an excellent degree of accuracy and reliability, no attempts have been made to use palynology to detect historical natural disasters. In the present study, fossil palynomorphs were used, for the first time, as a proxy for studying past hurricane activities and their associated damage to the fossil record using the New Orleans area as an example.

6.3. METHODS A total of 27 slides were made (three slides from each of the nine samples) following the standard palynological techniques for sample preparation and processing as mentioned in Section 2. The three slides include one kerogen, one sieved unstained, and one sieved stained for each sample. Sieved unstained slides were chosen for counting, from which the first 200 palynomorph specimens were counted, recorded and identified for paleoenvironmental and paleoclimatic interpretations. Sixteen samples were selected for 14C dating that was carried out at the National Ocean Sciences AMS Facility (NOSAMS), Woods Hole Oceanographic Institution, Woods Hole, Massachusetts (Table 6.1). This is in addition to one sample that was previously dated independently. Detailed NOSAMS 14C dating procedure can be found on their website at: http://www.whoi.edu/nosams/home

6.4. PALYNOMORPH ANALYSIS AND DISCUSSION Careful analysis of the studied samples revealed a palynomorph association of gymnosperm and angiosperm pollen, monolete and trilete fern spores, fresh water algae, and fresh water and marine dinoflagellate cysts. The identified fern spores include monolete spores of the family Thelypteridaceae and trilete spores such as Triplanosporites sp., Deltoidospora minor, Deltoidospora mesozica, Verrucosisporites sp. and Rugulatisporites sp. (Fig. 6.2). These spores have darker exine colors than what would be expected from a Holocene assemblage, suggesting

that they are of older age (presumably Cretaceous to Paleogene). This argues for an abnormal and complex sediment contribution to the area that has an element of reworking and re-deposition of older rocks.

Table 6.1. Radiocarbon (14C) dating data as obtained from NOSAMS.

NOSAMS Depth NOSAMS F Age Age Process d13C F Error d14C Receipt # (ft) Accession # Modern (YBP) Error 80783 10-12 OC OS-81342 -19.1 0.5839 0.0024 4320 35 -420 80784 15 OC OS-81703 -20.38 0.4707 0.0025 6050 40 -532.46 80836 16.5 OC OS-81269 -21.3 0.4602 0.0021 6230 35 -542.9 80785 18 OC OS-81350 -24.4 0.1976 0.0022 13000 90 -803.7 80837 19-20 OC OS-81270 -23.82 0.2382 0.0016 11500 50 -763.4 80786 21.5 OC OS-81249 -23.49 0.2585 0.0019 10850 60 -743.2 80787 24 OC OS-81700 -23.4 0.2965 0.0028 9760 75 -705.47 80838 25 OC OS-81271 -23.02 0.3012 0.0024 9640 60 -700.8 80839 26 OC OS-81272 -23.79 0.2352 0.0017 11600 60 -766.3 80788 27 OC OS-81687 -23.28 0.3388 0.0019 8690 45 -663.44 80840 28 OC OS- 81273 -22.85 0.3395 0.0019 8680 45 -662.8 80789 30 OC OS-81701 -23.09 0.371 0.002 7960 45 -631.47 80841 31 OC OS- 81274 -21.75 0.4013 0.0018 7330 35 -601.4 80842 32 OC OS- 81275 -21.87 0.4296 0.0025 6790 45 -573.3 80790 33 OC OS-81702 -21.94 0.4262 0.0023 6850 45 -576.7 80843 34.5 OC OS- 81276 -21.72 0.4775 0.0026 5940 45 -525.7

The identified dinoflagellate cysts include marine and non-marine morphotypes. They include Bosidinia sp., Polyspaeridium zoharyi, Cyclonephelium spp., Spiniferites spp., Alisogymnium sp., Trithyrodinium suspectum, Hystrichosphaeridium tubiferum, Anthosphaeridium sp., Dinogymnium sp. and Oligosphaeridium pulcherrimum (Fig. 6.3). Pediastrum is the only fresh water alga recorded. Some of the recorded dinoflagellate cysts show the same dark wall color phenomenon that was noticed in the fern spores. It is known that walls of dinoflagellate cysts, amongst other palynomorph types, require the greatest length of time to darken with geothermal maturation (Traverse, 2007). Accordingly, these cysts are believed to be originally deposited in a different environment and were

subjected to a totally different thermal history than the remaining majority of dinoflagellate cysts which have light wall colors (many were even colorless) and are believed to be Recent in age. These dark colored cysts were likely reworked during a catastrophic storm/hurricane as a result of high amounts of precipitation and copious runoff to end up in the study area. This process was likely very rapid and occurred over a short distance as indicated from the good preservation of these dark walled dinoflagellates. Otherwise, oxidation and degradation would have destroyed them. Among the recorded angiosperm pollen grains is the genus Aquilapollenites which is represented by at least three different species (Fig. 6.3). These taxa show the same dark exine color character. Moreover, Aquilapollenites attenuatus is known to be of Cetaceous to Paleogene age (Palynodata, Inc. and White, 2008). This is also taken as another evidence of the complex geologic history that strongly supports the suggested past hurricane background of the area. The same reworking mechanism as that of the recorded fern spores and dark colored dinoflagellate cysts is also suggested for these pollen grains.

6.5. RADIOCARBON DATING Radiocarbon (14C) data show that a major distortion in the sedimentary sequence of the 17th Street Canal borehole took place around 6000 years before present (YBP) (Fig. 6.4). This distortion is interpreted here to be in the form of reworking of large quantities of older sediments from adjacent areas, which dumped them quickly into the location of this studied section. About 16.5 ft (5.03 m) of section (depth from 17−33.5 ft) were deposited during this process. The present 14C data perfectly correlated with the palynologic results obtained independently earlier, which strongly suggest that a major marine surge accompanied by high amounts of rain fall was likely responsible for the observed distortion in the sedimentary sequence of the 17th Street Canal section. This caused recent marine palynomorphs associated with reworked older terrestrial and marine morphotypes to co-exist within this particular 16.5 ft (5.03 m) interval of the 17th

Street Canal section. Normal sedimentation conditions then resumed until around 1300 YBP with an average sedimentation rate of about 2 feet (0.61 m) per thousand years.

Figure 6.2. All specimens were photographed under 100× magnification. 1. Thelypteridaceae. 2. Deltoidospora mesozoica 40×. 3. Triplanosporites sp. 4, 5. Betulaceae. 6. Alismataceae. 7. Typhaceae. 8, 9. Cyperaceae. 10, 11. Juglandaceae. 12. Chenopodiaceae. 13. Tricolpate angiosperm pollen. 14. Pinaceae. 15. Taxodiaceae. 16. Fagaceae. 17. Asteraceae.

Figure 6.3. All specimens were photographed under 100× magnification unless otherwise mentioned. 1, 2. Aquilapollenites spp. 3. Aquilapollenites attenuates. 4. Anthosphaeridium sp. 40×. 5. Operculodinium sp. 6, 7. Spiniferites spp. 8. Cyclonephelium sp. 40×. 9, 10. Dinogymnium spp. 11. Polysphaeridium sp. 40×. 12. Unidentified palynomorph. 40×. 13. Freshwater dinoflagellate cyst of the genus Bosedinia. 14. Pediastrum sp. 40×. 15. Unidentified palynomorph. 16, 17. Wodehousea sp.

6.6. PALEOENVIRONMENTAL AND PALEOCLIMATIC INTERPRETATION Palynomorph count and composition clearly indicate that the studied sequence was deposited in a terrestrial paleoenvironmental setting that was likely a flood plain swamp. This is based on the presence of very high abundance of Holocene pollen grains (terrestrial element) that made up more than 93% of total count in the majority of the studied samples (Fig. 6.4). The recorded pollen grains reflect woodland vegetation of the families Pinaceae, Taxodiaceae, Juglandaceae, and Fagaceae associated with small number of sparsely distributed small trees and shrubs of families like Casuarinaceae and Asteraceae. Grasses were not uncommon as indicated by the presence of Cyperaceae and Poaceae. Pollen grains of Taxodiaceae decrease in number down section while those of Pinaceae increase in the same direction indicating a gradual change in flora with the replacement of Pine forest by Taxodium forest with time (Fig. 6.4). This could be related to anthropogenic effect or climatic or environmental change. If it is due to climate, a gradual warming, or change from subtropical-temperate to tropical conditions is suggested. The presence of common marine dinoflagellate cysts (up to ~14% of the total count in some samples) within the anomalous 16.5 ft (5.03 m) interval (depth from 17−33.5 ft) indicates an obvious marine influence. The majority of these dinoflagellate cysts are Holocene morphotypes with some older specimens as indicated from their wall colors. This combination of recent and older marine fossils is believed to be a result of a strong marine surge during a severe storm/hurricane activity that invaded the area and brought these recent dinoflagellates from the ocean. Older fossils were likely reworked from older rocks by the associated high amounts of rainfall and increased runoff as discussed earlier.

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6.7. CONCLUSIONS Palynologic analysis integrated with 14C dating was innovatively used to detect a major storm/hurricane activity in the New Orleans area around 6000 YBP. This approach is based on the presence of a mixture of fossil palynomorphs that belong to different ages and paleoenvironments within a particular interval of the studied sequence. Palynomorph nature and composition reflect a probable flood plain swamp depositional setting that was invaded by a powerful marine surge during a catastrophic storm/hurricane activity.

6.8. ACKNOWLEDGMENTS The author wishes to thank J. David Rogers for providing the samples and data necessary to carry out this project. He also funded the 14C dating and palynologic preparation and processing of the samples. Sincere appreciation is expressed to Mohamed Abdelsalam for allowing full access to his GIS and Remote Sensing lab.

6.9. REFERENCES Internet Reference 1: Http://maps.csc.noaa.gov/hurricanes/index.jsp

Palynodata, Inc., White, J.M., 2008. Palynodata datafile: 2006 version, with Introduction by White, J.M. Geological Survey of Canada Open-File 5793, 1 CD-ROM.

Traverse, A., 2007. Paleopalynology, second ed. Springer, Dordrecht.

VITA

Mohamed Kamal Zobaa was born in Benha, Egypt. He received his Bachelor’s degree in Geology in 2000 from the Geology Department, Benha University, Egypt. In 2006, he received his Master’s degree in Geology (emphasis: Palynology) from the Geology Department, Benha University, Egypt. Mohamed received his PhD degree in Geology and Geophysics (emphasis: Palynology) in 2011 from the Department of Geological Sciences and Engineering, Missouri University of Science and Technology, Rolla, Missouri, USA. Mohamed’s professional appointments include: Demonstrator of Geology, Department of Radioactive Sedimentary Deposits, Nuclear Materials Authority of Egypt (2001−2002), Demonstrator of Geology, Geology Department, Benha University (2002−2006), Assistant Lecturer, Geology Department, Benha University (2006−2011), Research Associate, Department of Biological Sciences, East Tennessee State University (2006−2008), and Teaching Assistant, Department of Geological Sciences and Engineering, Missouri University of Science and Technology (2008−2011).