FACULTYOFSCIENCE ASSIUT UNIVERSITY DEPARTMENT OF GEOLOGY
PROCEEDINGS OF THE EIGHTH INTERNATIONAL CONFERENCE ON THE GEOLOGY OF AFRICA
24-26 November 2015 ASSIUT-EGYPT
FACULTYOFSCIENCE ASSIUT UNIVERSITY DEPARTMENT OF GEOLOGY
PROCEEDINGS
OF THE EIGHTH INTERNATIONAL CONFERENCE ON THE GEOLOGY OF AFRICA
24-26 November 2015 ASSIUT-EGYPT
Preface
The Eighth International Conference on The GEOLOGY OF AFRICA (Africa-8) is a major biennial meeting organized under the auspices of President of Assiut University by the Department of Geology, Faculty of Science. Since the first conference in 1999, this event has been hosted regularly.
It is our pleasure to welcome you in the Geology Department-Assiut University and to thank all the participants, especially those who offered their scientific contributions from African countries, Egyptian universities and organizations and those interested in its spectacular Geology. No doubt that the achieved success in the previous six conferences was, indeed, the driving force for the organizers of this eighth meeting. We do hope that the conference will provide a unique opportunity for exchanging new ideas and information on multidisciplinary geological perspectives, including their impact on the geo-environment of the continent, future plans and efforts aiming at sustainable development and conservation of natural resources.
It is also our pleasure to offer this abstract collection including 105 titles covering almost all branches of geology. We hope that the conference days will permit and offer the chance for all participants gathered in Assiut to exchange experience through plenary talks, oral research presentations and panel discussions. In addition to six general invited talks, 71 contributions will be discussed in fifteen sessions for oral presentation beside 28 papers are presented as posters in parallel manner during the two and half days. Finally We wish all the attendants, a pleasant stay and fruitful discussion and may Almighty God lead our way to gain a sustainable collaboration for the sake of African people and humanity everywhere.
The Organizing Committee
FACULTY OF SCIENCE ASSIUT UNIVERSITY DEPARTMENT OF GEOLOGY
تقرير عن مؤتمر جيولوجيا أفريقيا الدولى الثامن
تم افتتاح الدورة الثامنة من "المؤتمر الدولى الثامن عن جيولوجية أفريقيا" فى الساعة العاشرة من صبااح الثالثاء 42 نبوفمار حضوبور أ.د. أحمبد عابدج جعبيل القباعم حعمبس رعبيم ال،امعبة أ.د. حسبن مضمبد حسبن الهوارى عميد كلية العلوم ورعيم شرف المؤتمر أ.د. جالل حامد الضااك رعبيم سسبم ال،يولوجيبا ورعبيم المؤتمر أ.د. حسن عاد الضميد سليمان رعيم الل،نة المنظمة أ.د. مصبفىى مضمبود يوسبك سبررتير عبام المؤتمر وذلك فى القاعة الثمانية حالمانى اإلدارى ل،امعة أسيوط وحعد االفتتاح الرسمى حدأت أعمال المؤتمر ح،لسة ممتدة القى فيها ستة مضاضرات مدعوة لعدد من الخاراء المتميزين فى العلوم ال،يولوجيبة وم،باالت الاترول والتعدين. وسد تم توزيع الارنامج العلمى وكتاب ملخصات الاضوث وعددها 402 حضثا لرس المشاركين فى حقياة المؤتمر الذى شارك فيه حاالحضاث زمالء من ال،امعات المصرية ومراكز ومعاهد الاضوث وحعض الهيئات والشركات العاملة فى حقبس الاتبرول والتعبدين حاإلضبافة البى عبدد مبن حضبوث المشباركين مبن البدول األفريقية ) 33 حضث( تم مناسشة هبذج األحضباث التبى تطفبى جميبع فبروع العلبوم ال،يولوجيبة علبى مبدى ايبام المؤتمر من خالل 41 جلسة علمية لإللقاء الشىهى و6 للمعلقات .
وعلى هامش المؤتمر تم تنظيم ورشة عمس تضت عنوان " أخالسيات علوم األرض" أدارها العالم ال،ليس األستاذ الدكتور/ مضمد رجاعى الفضالوى األستاذ المتىرغ ح،امعبة أسبيوط ورعبيم ال،امعبة ومضبافو أسبيوط األساق
توصيات المؤتمر الدولى الثامن عن جيولوجية أفريقيا أسيوط 42- 46 نوفمار 4041
اجتمع المشاركون فى المؤتمر البدولى الثبامن عبن جيولوجيبة أفريقيبا المنعقبد فبى سسبم ال،يولوجيبا – كليبة العلببوم جامعببة أسببيوط فببى الىتببرة 42- 46 نببوفمار 4041 حعببد اإلنتهبباء مببن ال،لسببات العلميببة وذلببك فببى ال،لسة الختامية للمؤتمر ظهر يوم الخمبيم الموافبق 46 نبوفمار 4041 حيبث نباسش الضاضبرون المسبتوى العلمى ووساعع وخفوات تنظيم المؤتمر كما توصس الم،تمعون إلى عدد من التوصيات نوجزها فى اآلتى: 4 - يتقدم الم،تمعون لسعادة األستاذ الدكتور/ رعيم جامعبة أسبيوط والسبيد األسبتاذ البدكتور / حسبن مضمبد الهوارى عميد كلية العلوم ورعيم شرف المؤتمر حخالل التضية واإلمتنان على دعمهم وتذليس العقاات أمام انعقاد المؤتمر فى دورته الثامنة كما يعرب المشاركون عن خالل التقدير والعرفان ألعواء الل،نة المنظمة وأسرة سسم ال،يولوجيا حأسيوط على ال،هود العظيمة من أجس ن،اح المؤتمر تنظيميا وعلميا. 4 - يالحو المشاركون االست،احة الىعالة من المؤسسات العلمية األفريقية ورغاتها فى المشاركة فى المؤتمر حيث تومن كتاب ملخصات الاضوث عدد 33 حضثا لل،يولوجيين األفارسة ولم تستفع الطالاية العظمى مبنهم الضوبور للمشبباركة لببذا يسب،س أعوبباء المببؤتمر توصبيتهم حزيببادة التواصببس مبع وزارة الخارجيببة المصببرية لتسهيس حصول المشاركون من الدول األفريقية على تأشيرات الدخول حتى يتضقق أحبد أهبم أهبداف المبؤتمر لتوسيع داعرة التعارف والمشاركة والتعاون العلمى على نفاق أكار عدد ممرن من الدول األفريقية. 3 - استمرار التواصس مع الوكالة المصرية للشراكة من أجس التنمية – وزارة الخارجية والعمس علبى اعتابار المؤتمر نظرا إلنتظام انعقادج كس عامين أحد وساعس التواصس حين أركان القارة وأحد أسم التنمية المستدامة فى م،االت علوم األرض و الثروة المعدنية والعلوم الايئية. 2 - الدعوة إلى توثيق الرواحط العلمية وتابادل الخابرات حبين العباملين فبى الضقبس ال،يولبوجى فبى العديبد مبن الدول األفريقية والعمس على تش،يع الم،موعات اإلسليمية على التعاون للوصبول إلبى الترامبس وإعبداد ساعبدة حيانات وخراعط حديثة ودسيقة لرافة الموارد الفايعية وإحتياطاتها فى القبارة األفريقيبة . وفبى هبذا الموبمار يوصى الم،تمعون حإلضاح على تروين الم،موعات الاضثية اإلسليميبة التبى ت،مبع التخصصبات المتقارحبة معبا حهدف رحط ومواهاة األحداث حين األساليم وحعوها وعدم التوسك عند الضدود السياسية حين دول القارة. 1 - دعوة ال،امعات ومراكز الاضوث العلمية فى كافة الدول األفريقية إلى إسامة ت،معبات أفريقيبة علميبة فبى م،ال علوم األرض عن طريق توثيق عرى التعاون العلمى والىنى وتاادل المعارف وتوسيع داعبرة اإلتىاسبات الثناعية واإلسليمية. 6 - يالحو المشاركون كثرة اإلعتذارات من الااحثين األفارسة عن حوورالمؤتمر على الرغم من ملخصات الاضببوث التببى أرسببلوها وتأكيببدهم الرغاببة فببى المشبباركة وأوضببضت الل،نببة المنظمببة حببأن السبباه داعمببا هببو إرتىاع أسعار الفيران حين الدول األفريقية وعدم وجود دعم مالى يساهم فى حوور العديبد مبن المشباركين لذلك يوصى المشاركون فى المؤتمر الدولى الثامن على ضروروة العمس على إي،باد وسبيلة دعبم للمشباركين من الدول األفريقية التى تعانى من ضيق الساس للضوور والمشاركة فبى المبؤتمرات المسبتقالية عبن طريبق اإلتصال المارر حاعض الهيئات المانضة أو وزارة الخارجية. 7 - يوصى الم،تمعون الادء المارر فبى اإلعبالن وتنظبيم المبؤتمر التاسبع ووضبع اسبتمارات التسب،يس علبى شارة المعلومات الدولية. 8 - يوصى الم،تمعون حزيادة الدعوات الماررة إلى المهتمين ح،يولوجية أفريقيا من خارج القارة األفريقية ) أوروحا - الواليات المتضدة – أستراليا – وآسيا ( للتأكيد على الصاطة الدولية للمؤتمر. 9 - انعقاد المؤتمر حشرس دورى مع تشريس ل،نة داعمة دورية ووضع آليه لعملها وتوسيع داعرة المشاركة فى المؤتمر وذلك عن طريق وضع معلومات المؤتمر فى المواسع المتخصصة حالمؤتمرات على شارة المعلومات الدولية.
40 - الاضث عن آليه لتقديم الدعم العلمى والمادى للاضوث التفايقية ومتاحعة تنىيذها. 44 - ترليك ل،نة من الل،نة المنظمة للمؤتمر حعد انتهاء اعمالبه لطبرض اسبتقراء الاضبوث التبى شبارك حهبا الروادر األكاديمية والتى تستضق الدراسة فى سفاع ال،يولوجيا عامة والتوصية حتنىيذها. وعلى هامش المؤتمر تم عقد ورشة عمس تضت عنوان "أخالسيات علوم األرض" وحدعم من مرته اليونسرو حالقاهرة تم خاللها القاء مضاضبرة للبدكتورج / إينبا أحمبد – مبن المتضبك ال،يولبوجيى حالقباهرة: عبن Geoethicsوالمنظمة الدولية ألخالسيات علوم األرض ) International Association )IAGETH for Geoethics وتاعها مضاضرة لألستاذ الدكتور / مضمد رجاعى الفضالوى عن الخارات المتراكمة والتتاحعبات التبى تراكمبت عار االجيال من افرار اخالسية خاطئه اورثتنا عائا ثقيال ي،ه المابادرة لتصبضيضه مبن اجبس االجيبال القادمبة . تلى ذلك مناسشات على كافه المستويات حين االجيال والقفاعات المختصة حعلوم االرض على كافه المستويات وكانت من نتاع،ها التوصيات التالية: 4- ضرورة تررار الورش من هذا النوع على مستوى ال،امعات 4- كتاحببه وتببدريم فصببس يخببتل حأخالسيببات علببوم األرض فببى كتبباب اخالسيببات المهنببة الببذى يدرسببه طببالب مستوى الارالوريو 3- عمس ساعدة حيانات لرس التخصصبات فبى علبوم االرض مبن خبالل االكباديمين والاباحثين والعباملين حنفباق علوم االرض وفروعها على مستوى مصر للتعرف على المشاكس فى كس م،ال ووضع التوصبيات او الضلبول لمعال،تها تاعا لمىهموم التنميه المستدامه من خالل التواصس عار شارة المعلومات الدولية . 2- كتاحة تلك التوصيات فى ال،زء الخاص حمصر ليرون Code of Geoethics الخاص حمصر فى المنظمه الدوليه IAGETH ومشاركته دوليا والعمس على إنشاء صىضه خاصه حالمنظمه خاصة حمصر عابر وسباعس التواصس االجتماعى.
أسيوط : 46 نوفمار 4041
سررتير عام المؤتمر رعيم الل،نة المنظمة رعيم المؤتمر ورعيم سسم ال،يولوجيا أ.د.مصفىى مضمود يوسك أ.د. حسن عاد الضميد سليمان أ.د. جالل حامد الضااك Recommendations of the Eighth International Conference on the Geology of Africa Assiut, 24 to 26 November 2015
The Participants of the Eighth International Conference on the Geology of Africa, held in the Department of Geology - Faculty of Science - University of Assiut, in the period 24 to 26 November 2015 were gathered at the closing session after the completion of the scientific program, on the afternoon of Tuesday, November 26th, 2015. They discussed the scientific level and the facts and steps of organizing the conference. Participants have reached a number of recommendations can be summarized as follows: 1- Participants offer their sincere greetings and gratitude to Prof. Dr. President of Assiut University and Prof. Dr. Hassan Mohamed Hawary Dean of the Faculty of Science and Honorary President of the conference for their continuous support during the organization of the conference in its eighth session at this time. Participants also express their sincere appreciation and gratitude to the members of the organizing committee and the family of the Department of Geology at Assiut for the great efforts pertaining to the success of the conference organizationally and scientifically. 2- Participants noticed an effective response from the African scientific institutions and the desire to participate in the conference where book summaries of the research included the number 33 search of African geologists, has been unable vast majority of them come to participate, so registered members of the Conference their recommendation to increase communication with the Egyptian Foreign Ministry to facilitate the access of participants from countries African and who are acceptable to the listeners or throwing them visas research even one of the main objectives of the conference achieved to expand the circle of acquaintance and participation and scientific cooperation across the largest possible number of African countries. 3- Continuity of cooperation with the Egyptian Agency for Partnership for Development - Ministry of Foreign Affairs and work on the Conference due to irregular held every two years of scientific communication between the continent and one of the foundations of sustainable development in the fields of Earth Sciences and Mineral Resources and Environmental Sciences. 4- Participants call for closer ties and scientific exchange of experiences between workers in the field of earth sciences in African countries and to encourage regional groups to cooperate to reach the integration and development of a database of the natural resources and reserves in the African continent. In this regard, the conferees urgently recommended the formation of regional research groups which combine disciplines converged together with the aim of linking and matching events between different regions, and do not stop at political borders between the countries of the continent. 5- Call of universities and scientific research centers in all the African countries to establish an African scientific communities in the field of earth sciences through closer scientific and technical cooperation and the exchange of knowledge and expand the circle of bilateral and regional agreements. 6- Participants noticed frequent apologies of African researchers to attend the conference, although the abstracts, which they sent and confirm the desire to participate, and explained by the organizing committee that the reason is always the high price of aviation between African countries and the lack of financial support contributes to the presence of many of the participants. It is strongly recommended to actively work on finding a way to support participants from African countries suffering from shortness of ways to attend and participate in future conferences, through early contact with some donor agencies or the State Department. 7- The participants recommended early start in advertising and organizing the conference and to raise the registration forms for The Eighth conference on the international information network early. 8- The participants recommended increasing the early invitations to those interested in geology Africa from outside the African continent (Europe - the United States - Australia - Asia) to emphasize the international character of the conference.
On the sidelines of the conference; a workshop entitled "Ethics of Earth Sciences" was organized with the support of the UNESCO Cairo office and chaired by Prof. Dr. M. R. El Tahlawi – Assiut University and Dr. Enas Ahmed - Geological Museum, Cairo followed by an open discussion and reached by following recommendations: a- To organize such events on the Geoethics in other Egyptian universities b- Write and teach chapter about ethics in Earth Sciences for under graduate university students. c- Construct a data base for the Egyptian academics and researchers in different fields of Earth Sciences and strengthen communication via international social media. d- Cooperate with the IAGETH as International Organization to have a section for “Egyptian Code of Geoethics” and maintain continous information dissemination.
Assiut; November, 26th 2015
General Secretary Organizing Committee Prof. Dr. Moustafa M. Youssef Prof. Dr. Hassan A. Soliman
Chairman Prof. Dr. Galal H. El Habbak
Africa-8, Assiut 24-26 November 2015 UNDER THE AUSPICES OF
Prof. Dr. President of Assiut University
Prof. Dr. Hassan Mohamed El-Hawary; Dean of Faculty of Science Prof. Dr. Galal Hamed El Habaak Head of Geology Department
Editor: Prof. Dr. Moustafa M. Youssef
Organizing Committee: Prof. Dr. Hassan A. Soliman Chairman Prof. Dr. Moustafa M. Youssef General Secretary Prof. Dr. Fawzi F. Abu El-Ela Member Prof. Dr. Ahmed R. El Younsy ,, Prof. Dr. Mohamed A. Hassan ,, Prof. Dr. Nageh A. Obaidalla ,, Prof. Dr. Mohamed Abdel Moneim ,, Assoc. Prof. Dr. Mohamed M. A. Ali ,, Dr. Amr S. A. Deif ,, Scientific Committee: Prof. Dr. Hassan A. Soliman Prof. Dr. Samir R. Ismail Prof. Dr. Alia El Husseiny Prof. Dr. Emad R. Philobbos Prof. Dr. Abdel Mohsen Abbas Prof. Dr.Mohamed E. Habib Prof. Dr. Moustafa M. Youssef Prof. Dr.Mohammed A. Soliman Prof. Dr. Adel A. Hegab Prof. Dr.Ezzat A. Ahmed Prof. Dr. Ali A. Khudeir Prof. Dr.Mervat M. El Haddad Prof. Dr. Khaled A. Ouda Prof. Dr. Wageh W. Bishara Prof. Dr. Fawzi F. Abu El-Ela Prof. Dr. Hamza A. Ibrahim Prof. Dr. Nadia Sharara Prof Dr. Esmat Keheila Prof. Dr. Awad A. Omran Prof. Dr. Hussein A. Hegazi Prof. Dr. Ahmed R. Elyounsy Prof. Dr. Ali Helmy Abd El-Atti Prof. Dr. Abdel Hay Farrag Prof. Dr. Elsayed M. Abu El-Ela Prof. Dr. Magdy S. Mahmoud Prof. Dr.Abdel Azim Ibrahim Prof. Dr. Mahmoud Senosy Prof. Dr. Galal H. El-Habbak Prof. Dr. Mohammed Abdel Raouf Prof. Dr. Nageh A. Obaidalla Prof. Dr. Yasser M. Abd el-Aziz Prof. Dr. Assem El-Haddad Prof. Dr. M. Abdel Moneim Prof. Dr.Mamdouh F.Soliman
CONTENTS
Page
(I) SEDIMENTOLOGY
_ Karst Hazards Around Sohag City, Egypt: Distribution, Investigation, Causes And Impacts I-1 By: Bosy A. El-Haddad, Ahmed M. Youssef, Abdel-Hamid El-Shater ,
and Mohamed H. El-Khashab Field Characterization Of Fracture Aperture And Fill In A Limestone _ I-17 Quarry, Yorkshire, United Kingdom By: Aisha Abubakar KANA, Ahmad Abubakar KANA and K’tso
NGHARGBU Engineering Evaluation Of Some Lower Eocene Carbonate Rocks As Raw _ I -33 Materials, Sohag Governorate, Egypt By: Ahmed K. Abd El-Aal Petrography And Diagenetic Features As Indicators To Predict The Depth Of _ I -51 Burial Of The Paleozoic Sandstones, Gulf Of Suez Province, Egypt By: Salma Abdelmalek , Amir Said and Mohamed Darwish
(III) ENVIRONMENTAL GEOLOGY AND HAZARDS
- Characterizing Ancient Gold Of The Eastern Desert, Egypt III- 1 By: Thomas Faucher Impact And Ranking Of Five Salt Weathering Regimes On Oolitic Limestone, _ III-13 Of North Western Desert Of Egypt, Using Two Sulfate Salts By: Kamh, G. M. E. Monitoring Geomorphological Changes And Desertification InNorthwestern _ III-33 Coastal Zone, Egypt Mamdouh M. M. El-Hattab
(IV) HYDROGEOLOGY & WATER MANAGEMENT
_ Evaluation The Quality Of Groundwater At Fares, Kom Ombo, Aswan, Egypt IV-1 By: M. Abdel-Moneim, E. Keheila, , M. Saber, O. Yehya Utilization Of Hydrogeophysics In Assessment Of The Groudwater Aquifer At _ IV- 13 Wadi Dara Area, Eastern Desert, Egypt By: Sayed Bedair _ Evaluation Of Groundwater Aquifers Potentiality To Delineate Temporal Changes In Landuse In Nag-Hammadi Area,Qena, Egypt , Using GIS And IV- 27 Remote Sensing Techniques By: A. A. Farrag, H. A. Megahed, E. A. El Sayed and A. M. El Sayed Hydrogeochemical Assessement Of The Carbonate Rocks Of The Eocene Age _ IV- 43 In The Eastern Nile Valley, Egypt By: Esam A. El Rahman , Gad M. A. and Saad A. Groundwater Level-Rise Monitoring And Recharge Determination At An Old _ IV- 67 Archaeological Site: Abydos, Sohag, Egypt By: Sefelnasr A., Abdel Moneim A., Abu El-Magd Sh. Hydrochemical Analyses Of Groundwater And Its Suitability For Drinking _ IV- 83 And Agricultural Uses At Siwa Oasis, Western Desert Of Egypt By: Farrag A. A. and H. A. Megahed _ 3D-Groundwater Flow Modeling For Water Level-Rise Detection And Recharge Determination At An Old Archaeological Site: Abydos, Sohag, IV- 101 Egypt By: Sefelnasr A., Abdel Moneim A., Abu El-Magd Sh.
(V) PETROLEUM GEOLOGY AND MINERAL RESOURCES
Reservoir Characteristics Of Nubian Sandstone Reservoir In Edfu And _ V-1 Saqqara Oil Fields, Gulf Of Suez, Egypt By: Nader El-Gendy, Moataz Kh. Barakat and Hamed Abdallah Petrophysical Evaluation And Petrographic Description For The Upper _ V-15 Rudeis Sandstone In North Central Gulf Of Suez, Egypt By: Moataz Kh. Barakat, Nader El-Gendy and Ahmed Emara
(VI) GEOPHYSICS
_ Liquefaction Potential Of Nile Delta, Egypt VI-1 By: Elsayed Fergany and Khaled Omar
(VII) STRATIGRAPHY AND PALEONTOLOGY
_ The Danian/Selandian (D/S) Boundary Event At Gabal Serai,Nile Vally, Egypt VII-1 By: Soliman, H. A.; Faris, M. , Obaidalla .N. A. and Metwally, A. A. Biostratigraphic Zonation And Eocene Chlorophytal Algae, Assiut-Minia _ VII-27 Stretch, Nile Valley, Egypt By: Sobhi A. Helal and Ahmed W. Hussein Litho-Stratigraphy And Petroleum Source Rock Potential Of The Southern _ VII-55 Bida Basin, Nigeria By: Usman, H.O., Obaje, N.G. and Nghargbu, K. Stratigraphy Of The Paleocene-Eocene Succession At Darb Gaga Area, Baris _ VII-77 Oasis, Western Desert, Egypt By: Nageh A. Obaidalla, Mostafa H. El Dawy, Kamel H. Mahfouz and Samar A. Abdel-Wahed Macro-Biostratigraphy Integration Of The Cenomanian - Turonian _ VII-99 Transition At North Eastern Desert And Southwestern Sinai, Egypt Mahmoud H. Darwish, Mohamed S. Zakhera, Nasr A. Abdel-Maksoud and Nageh A. Obaidalla Comparative Studies Of Recent And Fossil Echinoid Jacksonaster Depressum _ From The Northern Bay Of Safaga And Late Pliocene Rocks Of The Red Sea VII-125 Coast, Egypt Atef Abdelhamied Elattaar
(VIII) BASEMENT AND GEOCHEMISTRY
Proposed Geological Map For The Basement Rocks In The Eastern Desert _ VIII-1 And Southern Sinai By: Abdelmohsen A. Ahmed
THE EIGHTH INTERNATIONAL CONFERENCE ON THE GEOLOGY OF AFRICA P-P VII-1 - VII-26 (NOV. 2015) ASSIUT-EGYPT
THE DANIAN/SELANDIAN (D/S) BOUNDARY EVENT AT GABAL SERAI, NILE VALLY, EGYPT
Soliman, H. A.; Faris, M. , Obaidalla .N. A. and Metwally, A. A. Geology Department, Faculty of Science, Assiut University, Assiut, Egypt Geology Department, Faculty of Science, Tanta University, Tanta, Egypt
ABSTRACT
This work depends on high resolution stratigraphic investigations, including litho- and bio-stratigraphic studies on the Danian-Selandian (D-S) sediments at Gabal Serai, Nile Valley, Egypt. Lithostratigraphically, the D-S sediments are represented by the upper part of the Dakhla Formation. A marker beds (Qreiya Beds) of ~30 cm thick, represent the D/S boundary. These beds consist of four alternative beds of dark grey and brown-organic rich shales. These beds are thinly laminated, phosphatic and organic-rich. Biostratigraphically, six planktonic foraminiferal and four calcareous nannofossils zones are defined at the studied section representing the D-S transition. The D/S boundary is defined at the contact between the Igorina albeari/Praemurica carinata and the I. albeari planktonic foraminiferal zones at the base of P3b subzone which can be correlated with the NP4a/NP4b nannofossil sub-zonal boundaries. The D-S transition is divided into three main intervals based on the change in the floral and faunal assemblages: pre-D/S boundary, D/S boundary and post-D/S boundary. This reflects that the surface water paleotemperature is the cool below and above the D/S boundary to warm condition at the boundary. The paleoenvironment settings are outer neritic-upper bathyal environment for the Danian and Selandian sediments and middle neritic for the D/S boundary (Qreiya Bed). Keywords: Danian, Selandian, planktonic foraminifera, calcareous nannofossils, Gabal Serai, Nile Valley, Egypt.
1. INTRODUCTION
During the last decades, there is a wide agreement that the early Paleogene was marked by short warming (hypothermals) episodes (e.g. Zachose et al. 2001). These episodes have been recognized during the early Paleogene between 60 and 50Ma. The first was probably occurring near to the D/S boundary and second was at the Paleocene/Eocene boundary (Speijer 2003; Bornemann et al. 2009; Westerhold et al. 2011). Numerous studies using different criteria have been published to define the Global Statotype Section and Point (GSSP) of the Danian/Selandian boundary (e.g. Arenillas and Molina 1997; Schmitz et al. 1998; Speijer and Schmitz 1998; Speijer 2003; Clemmensen and Thomsen 2005; Guasti et al. 2006; Ortiz et al. 2006; Rodríguez and Aubry 2006; Orue-Etxebarria et al. 2007; Obaidalla et al. 2009; Schmitz et al. 2011 and Monechi et al. 2013). Schimtz et al. (2011) defined formally the D/S boundary at the Zumaia section (Basque Basin, northern Spain), at the base of the red marls of the Itzurun Formation. They defined this boundary at a level close to the lowest occurrence (LO) of F. tympaniformis near the calcareous nannofossil NP4/NP5 zonal boundary. In the North Sea Basin, Clemmensen and Thomsen (2005) placed this boundary between the calcareous nannofossil zones NP4 VII- 2 The Danian/Selandian (D/S) Boundary Event At Gabal Serai,…… {{{{{{{{{{{{ and NP5 within the lower part of planktonic foraminifera P3b Subzone of Berggren and Pearson (2005). In Egypt, the D-S transition is represented by the upper part of the Dakhla Formation, which is widely distributed and well-exposed all over the Egyptian provinces. The D/S boundary is marked by unique organic-rich sediments recorded in several sites in Egypt (Abdel-Halim, A. 2009; Obaidalla et al. 2009; Soliman and Obaidalla, 2010). This interval is coupled with an anomaly of the shallow water benthic foraminiferal species Neoponides duwi. This event was referred to as the “Neo-Duwi Event” by Guasti et al. (2005), and as the “Latest Danian Event (LDE)” by Sprong et al. (2011) and ‘‘Neo-Duwi beds” by Aubry et al. (2012). This distinct interval was named el-Qreiya Bed by Soliman and Obaidalla (2010) which reaches its maximum thickness (~30cm) at Gabal el-Qreiya section (Soliman and Obaidalla, 2010; Aubry et al, 2012). The purpose of this study is; (1) to provide a high resolution litho-stratigraphy and bio- stratigraphy based on the calcareous nannofossils and planktonic foraminifera. (2) Quantitative analysis of the calcareous nannofossils and planktonic foraminifera in order to understand the nature and the paleoenvironmental interpretations of the D-S transition in the studied section.
2. LOCATION AND MATERIALS
The materials of the present study were obtained from Gabal Serai, Eastern Desert, Egypt. The studied section (Latitude 26° 14` 06.9`` N, Longitude 33 ° 04 ` 16.6``E) is located about 13km East Qena City at road marker km35 at Qena-Safaga road (Fig. 1).
Fig. 1: Location map shows the studied section Soliman, H. A.; Faris, M., Obaidalla .N. A. and Metwally, A. A. VII- 3
Gabal Serai section is a composite section comprise two parts; subsurface and outcrop succession. The Serai core (NLH 32) was drilled by El-Nahda Cement Factory in January 2012. The cored succession is about 46m thick includes representative of two formations in stratigraphic order: Dakhla and Tarawan formations. The outcrop succession represented by Esna and Thebes formations. The present study is focused only on the Dakhla Formation where is the D-S transition is located. The samples were collected continuously from the Qreiya Beds (D/S boundary) and at different stratigraphic intervals (20-100cm) below and above Qreiya Beds from the Dakhla Formation. For calcareous nannofossils studies, the samples were processed by standard smear slide preparation from raw sediment as described by Perch-Nielsen (1985). Smear slides were examined using a polarized microscope with 1250 X magnification. Calcareous nannofossils are generally abundant and well preserved, which assist comprehensive quantitative and semi-quantitative analyses of the assemblages. Quantitative analysis has been performed across the D/S boundary of the studied section. Semi-quantitative analysis was carried out on the entire studied D-S transition. Relative abundances of calcareous nannofossils were applied following the criteria used by Bralower and Mutterlose (1995): A=Abundance>10 specimens/field of view (fov); C=common 9-1 specimens/fov; F=few 9-1 specimens/ 1-9 fov; R= rare 1 specimen/>10 fov. For nannofossil taxa preservation the following descriptions are used; G (Good): little or no overgrowth and no dissolution; M (Moderate): species show partly dissolution and overgrowth and P (Poor): species exhibit severe overgrowth and/or destruction of species. The most important calcareous nannofossils species illustrated in plate 1. For foraminiferal studies, the counting technique of Buzas (1990) applied, which is based on random splits of about 400 specimens in the size fraction larger than 125 µm. All specimens were picked, identified and mounted on microslides for permanent record. Planktonic/benthic percentages (P/B%) and relative abundances of planktonic foraminiferal genera were determined in the same size fraction. The relative abundances of planktonic foraminiferal groups (genera and species) are also determined. The number of total foraminiferal species (planktonic and benthic) per one gram of residue is determined. The identified planktonic foraminiferal species are photographed using the Scanning Electron Microscope (JSM 5400 LD) at Assiut University. The index species of planktonic foraminifera are illustrated in plate 2.
3. RESULTS
3.1. Lithostratigraphy The investigated D-S transition sediments encompass 28m from the upper part of the Dakhla Formation (Text-Fig. 2). The Dakhla Formation was introduced by Said (1961) to describe the shale succession, overlying the phosphate beds of the Duwi Formation and underling the chalk and chalky limestone of Tarawan Formation at the long scarp north of Mut, Dakhla Oasis, Western Desert, Egypt. The Dakhla Formation is comprised of a thick succession of greenish gray, dark gray to black shales, with marl, marly limestones and calcareous fossiliferous mudstone intercalations that distinguish the middle parts. Dakhla Formation was subdivided by Abdel razik (1972) into two members the lower Hamama (Marl) Member (Maastrichtian in age) and the upper Beida (Shale) Member (latest Maastrichtian-early Paleocene in age). In the study area the drilling did not penetrate the Hamama Member, so that this unit is not concerning. The studied section is represented by Beida Member (Fig. 2) which belongs to Danian and Selandian in age. It is composed of a thick succession of greenish gray, dark gray shale below and above the event bed (Qreiya Beds). VII- 4 The Danian/Selandian (D/S) Boundary Event At Gabal Serai,…… {{{{{{{{{{{{
The Danian sediments are separated from the Selandian sediments by the presence of alternating four organic-rich shale beds (Qreiya Beds; event beds). These beds are composed of ~30cm thick of alternating gray and brown organic-rich shale and representing the D/S boundary (Fig. 3). The lithology of these beds is as follows: Bed 1 (~5.5 cm): It spans the stratigraphical interval from sample no. 30 to sample no. 33. It is consisting of dark gray laminated shale. Bed 2 (~8 cm): It consists of organic-rich brown laminated gypsiferous shale with a robust fish skeleton on the bedding plane (Fig. 3). It spans the stratigraphic interval from sample no. 34 to sample no. 36. Bed 3 (~6 cm): It is similar to Bed 1, whereas it consists of dark gray laminated shale with oxidized pyrite concretion (~1 cm in diameter). It spans the stratigraphic interval from sample no. 37 to sample no. 38. Bed 4 (~11cm): It is similar to Bed 2, whereas it consists of organic-rich brown laminated gypsiferous shale rich in fish remains and Mollusca mould. It spans the stratigraphic interval from sample no. 39 to sample no. 40. The Qreiya Beds (D/S event Beds) are sandwiched within the shale of Beida Member at Gabal Serai.
Fig. 2: Lithostratigraphic section of the D/S boundary sediments showing the different lithostratigraphic units at G. Serai section Soliman, H. A.; Faris, M., Obaidalla .N. A. and Metwally, A. A. VII- 5
Fig. 3: (A) Photograph shows the Qreiya Beds. (B) Close-up view shows the phosphatic remains (fish skeleton) in Bed 2 at G. Serai
VII- 6 The Danian/Selandian (D/S) Boundary Event At Gabal Serai,…… {{{{{{{{{{{{ 3.2. Biostratigraphy The Paleocene calcareous nannofossil zonal scheme of Martini (1971) and the planktonic foraminifera zonal scheme with abbreviated P, for the Paleogene Zones of Berggern and Pearson (2005) are applied in the present study. The biostratigraphic interpretations are based mainly on the Lowest Occurrence (LO) and Highest Occurrence (HO). The stratigraphic distributions of the identified calcareous nannofossils and planktonic foraminifera are presented in Figs. 4-5.
3.2.1. Calcareous nannofossil zonation Three calcareous nannofossil zones are defined in the present study. These zones are arranged from base to top as follow:
Ellipsolithus macellus Zone (NP4) E. macellus Zone was defined by Martini (1971) as the biostratigraphic interval from the LO of the nominate taxon to the LO of Fasciculithus tympaniformis (Hay and Mohler). Faris et al. (2005 a, b) subdivided the NP4 Zone into two subzones; NP4a and NP4b based on the LO of Sphenolithus primus which coincides with the LO of Igorina albeari. In the present study, this classification is not relevant due to the LO of Igorina albeari at G. Serai (where the D/S boundary is more complete) at a depth of about 38m (Sample no. 20) while the LO of S. primus at about 34m (Sample no. 33). This indicates that the LO of S. primus is at high stratigraphic level than the LO of I. albeari. It was also difficult to subdivide the NP4 Zone into several subzones according to Varol (1989). It covers the stratigraphic interval from sample no. 1 to sample no. 44 and attains about 15m thickness (Fig. 5).
Fasciculithus tympaniformis Zone (NP5) The F. tympaniformis Zone was introduced by Mohler and Hay in Hay et al. (1967). This zone comprises the biostratigraphic interval from the LO of the nominate taxon to the LO of Heliolithus kleinpellii (Sullivan). It covers the stratigraphic interval from sample no. 45 to sample no.61 and attains about 10m thickness (Fig. 5).
Heliolithus kleinpellii Zone (NP6) It was defined by Mohler and Hay in Hay et al. (1967) as the biostratigraphic interval from the LO of the nominate taxon to the LO of Discoaster mohleri (Bukry and Percival). The H. kleinpellii (NP6) Zone is not represented in several localities in Egypt (e.g. Ain Dabadib, northwestern Kharga Oasis, Bassiouni et al. 1991; Gabal El-Teir, Kharga Oasis, Faris et al. 1999; El Hassana section, North Central Sinai, El-Deeb et al. 2000 and Gabal El-Bruk, North Central Sinai, Faris and Zahran, 2002) suggesting most probably a minor hiatus around Selandian/Thanetian boundary. This zone comprises the stratigraphic interval from sample no. 61 to sample no. 65 and attains about 3m thickness (Fig. 5).
3.2.2. Planktonic foraminiferal zonation The planktonic foraminiferal zones are arranged in stratigraphic order as follow:
Praemurica uncinata Zone (P2) The P. uncinata Zone was defined by Bolli (1966) as the partial range of the nominate taxon between its LO and the LO of Morozovella angulata (White). These datum events were also used by Berggren et al. (1995) and Berggren and Pearson (2005). Eoglobigerinids, parasubbotinids, subbitinids and praemuricids comprise about 80 % of the total planktonic foraminiferal assemblage within this zone (Fig. 6).
Soliman, H. A.; Faris, M., Obaidalla .N. A. and Metwally, A. A. VII- 7
Morozovella angulata Zone (P3a) This Zone was defined by Hillebrandt (1965) as the partial range of the nominate taxon between its HO and the HO of Planorotalites pusilla pusilla (Bolli). Berggren and Norris (1997) and Berggren et al. (1995) subdivided the biostratigraphic interval between the HO of M. angulata (White) and the HO of Globanomalina pseudomenardii (Bolli) into two subzones. The important planktonic foraminiferal species in this Zone are the praemuricid genera (e.g., P. inconstans, P. carinata and P. uncinata). These species constitute ~55% of the total assemblage (Fig. 6).
Igorina albeari/Praemurica carinata Zone (partim of P3b) This Zone was originally defined by Obaidalla et al. (2009) as a Concurrent-Range Zone from the LO of I. albeari (Cushman and Bermùdez) to the HO of P. carinata (EL-Naggar). It is equivalent to the lowermost part of P3b Subzone of Berggren et al. (1995) and Berggren and Pearson (2005) (Table 1). In the present study, the first appearance of I. albeari at sample number 20, ~3m below the base of the Qreiya Beds which indicate that the I. albeari/P. carinata Zone represents the uppermost Danian sediments. The most important planktic foraminiferal groups in this Zone are subbotinids, praemuricids and morozovellids. These groups comprise ~80 % of the assemblage (Fig. 6).
Igorina albeari Zone (partim of P3b) In the present study the definition of this zone is follow to Obaidalla et al. (2009). The I. albeari Zone was defined to cover the stratigraphic interval from the LO of the nominate taxon to the LO of G. pseudomenardii (Bolli). Obaidalla et al. (2009) emended this zone to cover the interval from the HO of P. carinata (EL Naggar) to LO of G. pseudomenardii (Bolli). It is equivalent to the main part of P3b Subzone of Berggren et al. (1995) and Berggren & Pearson (2005) (Table 1). The I. albeari Zone represent the basal part of the Selandian sediments (Qreiya Beds and ~ 5m above it). The dominance occurrences of subbotinids, morozovellids, igorinids and acarininids groups characterize this zone. These groups constitute about 80% of assemblage. Praemuricids group is completely disappeared in the basal part of this Zone (Event Beds) which in turn marks the basal surface of the D/S boundary (Fig. 6).
Globanomalina pseudomenardii/Parasubbotina variospira Zone (P4a) It was originally defined by Berggren et al. (2000) as a Concurent-Range Zone from the LO of G. pseudomenardii (Bolli) to the HO of P. variospira (Belford). This Zone is comparable to the P4a (lower most part) of Berggren et al. (1995). The most distinctive planktonic foraminiferal groups within this Zone are subbotinids morozovellids, igorinids and acarininids (Fig. 6).
Acarinina subsphaerica Zone (P4b) This Zone was originally defined by Berggren et al. (2000) as Partial-Range Zone from the HO of P. variospira (Belford) to the LO of Acarinina soldadoensis (Brönnimann). This Zone is comparable to the P4b Subzone of Berggren and Pearson (2005). The planktonic foraminiferal groups within this zone are similar to those of P4a Zone (Fig. 6).
VII- 8 The Danian/Selandian (D/S) Boundary Event At Gabal Serai,…… {{{{{{{{{{{{
Fig. 4: Stratigraphic distribution chart of the recorded calcareous nannofossil species throughout the D-S transition at the studied section
Soliman, H. A.; Faris, M., Obaidalla .N. A. and Metwally, A. A. VII- 9
Fig. 4: Continued…
VII- 10 The Danian/Selandian (D/S) Boundary Event At Gabal Serai,…… {{{{{{{{{{{{
Fig. 5: Stratigraphic distribution chart of the identified planktonic foraminiferal species throughout the D-S transition at the studied section
Soliman, H. A.; Faris, M., Obaidalla .N. A. and Metwally, A. A. VII- 11
3.3. Discussion
3.3.1. DANIAN/SELANDIAN BOUNDARY Several studies have been conducted to define the GSSP of the D/S boundary. The type locality of the D/S boundary in Denmark is marked by stratigraphic hiatus between the Danskekalk and Lellinge formations (Thomsen and Heilmann-Clausen, 1985). Berggren et al. (1995, 2000) suggested that the D/S boundary can be placed at the P2/P3 planktonic foraminiferal zonal boundary within calcareous nannofossil Zone NP4 at the base of magnetic Chron C26r (Guasti et al. 2005). In terms of calcareous nannofossils, the occurrence of the calcareous nannofossil N. perfectus used by Thomsen & Heilmann- Clausen (1985), Perch-Nielsen (1994) to define the top of the Danian Stage in Denmark. This event is recorded in the upper part of NP4 Zone, close to the NP4/NP5 boundary. Recently, the Zumaya section (Basque Basin, northern Spain) was accepted by the Paleocene Working Group (2007) to host the Global Stratotype Section and Point (GSSP) for the D/S boundary at the base of the red marls of the Itzurun Formation, below the NP4/NP5 zonal boundary. The D/S boundary was placed at stratigraphic level close to the LO of F. tympaniformis immediately below the NP4/NP5 zonal boundary (Schmitz et al., 1998; Bernaola et al., 2009). A dramatic event was recorded by Guasti et al. (2005) within the D/S transition in Egypt and Jordan termed the “Neo-duwi event”. This event is placed within the basal part of planktonic foraminiferal Zone P3b, close to the top of calcareous nannofossil Zone NP4. This event is located at stratigraphic interval between the LOs of Fasciculithus spp. and LO of F. tympaniformis. The end of acme of the nannofossil family Braarudosphaeraceae is used as a marker to define the GSSP of the D/S boundary in Zumaia section. This event seems to be applicable in these regions, but it is not relevant to tropical and subtropical regions (Tethyan sections) because the presence of Braarudosphaera in the Tethyan sections is extremely scarce or absent (Bernaola et al. 2009; Youssef 2009; Faris and Farouk 2012; Monechi et al., 2013). Schmitz et al. (2011) and Monechi et al. (2013) have placed the base of the Selandian Stage at Zumaia at the “second radiation of the fasciculiths” which marked by the LO of Lithoptychius ulii. Aubry et al. (2012) have recognized a major radiation marked by the appearance of two genera, Diantholitha and Lithoptychius at Qreiya, Egypt. This event is coinciding with the Neo-Duwi event which probably correlates with the D/S boundary in Spain (Bornemann et al. 2009; Sprong et al. 2011). Aubry and Salem (2013) believed the observations of Aubry et al. (2012) and estimated the base of the Selandian Stage by means of the Diantholitha and Lithoptychius sequence and subdivided the NP4 Zone into NP4a and NP4b subzones based on the LO of Diantholitha mariposa. Following the criteria of Aubry and Salem (2013), the NP4 Zone in the present study is subdivided into two subzones; NP4a and NP4b on the basis of the LO of D. mariposa which defined the base of the Selandian Stage. In the present study, the LO of D. mariposa is corresponding to the HO of Praemurica carinata (I. albeari /P. carinata planktonic foraminiferal Zone of Obaidalla et al. 2009) which defined the D/S boundary at the studied section. This inconsistency to identify the D/S boundary is due to the differences between the bioevents (planktonic foraminifera and calcareous nannofossils) in different latitudes which in turn resulted in differences in the relative positions of the D/S boundary. These differences are most probably owing to the taxonomical concept and/or different climatic changes across different latitudes (Farouk and Faris, 2013).
VII- 12 The Danian/Selandian (D/S) Boundary Event At Gabal Serai,…… {{{{{{{{{{{{
transition thein present study and their comparison the with other zonal schemes 1: Table
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3.3.2. PALEOENVIRONMENTAL INTERPRETATION ACROSS THE DANIAN/SELANDIAN BOUNDARY
The D-S transition in the present study is subdivided into three main intervals on the basis of the changes in the composition of sediments and the content of microfossil assemblages (planktonic foraminifera and calcareous nannofossil) as the following: Soliman, H. A.; Faris, M., Obaidalla .N. A. and Metwally, A. A. VII- 13
3.3.2.1. Pre-D/S boundary (Danian sediments) The pre-D/S boundary interval consists of grey shale sediments. This interval is characterized by the dominance of praemuricids taxes, which have a relative abundance reach to ~ 55% of the total foraminiferal assemblages (Fig. 6). Parasubbotinids and subbotinids taxa were found to be in a relatively high abundance during this interval; 15- 25% and 10-20%, respectively. Upward, these taxa show a gradual decrease in abundance, particularly praemuricids which disappeared just below the D/S boundary. The gradual decrease of these taxa coincides with gradual increase in morozovellids toward the D/S boundary (Fig. 6). The presence of parasubbotinids and subbotinids taxa, which considered as cool-water species (Boersma and Premoli, 1983; Boersma and Premoli, 1991; Pearson et al., 1993; Norris, 1996; Berggren and Norris, 1997; Soliman and Obaidalla, 2010) in relatively high percentages in the Danian sediments reflect cool climate conditions that time. In contrast the warm-water foraminiferal taxa particularly morozovellids (Boersma and Premoli, 1983; Pearson et al., 1993; Kelly et al., 1996; Norris, 1996; Berggren and Norris, 1997; Quillévéré and Norris, 2003) show relatively low percentages during this interval. The cool climate trend during the pre-D/S boundary at the studied section is supported by the relatively high abundance of the cool-water calcareous nannofossil indicators especially Placozugus sigmoides, while the warm-water Ericsonia subpertusa and Coccolithus pelagicus species are represented by relatively low percentages (Fig. 8). Placozygus sigmoides is considered typical cool-water species due to its blooms were recorded from high latitude sites (Pospichal and Wise, 1990). The increased abundance of P. sigmoides was noted in lower Paleocene section in Central Egypt, Eastern Desert by Tantawy (2003). In the present study, P. sigmoides ranges from 10 to 25% during the Danian sediments reflect cool climate conditions (Fig. 8).
3.3.2.2. D/S boundary (Qreiya Beds) The D/S boundary is marked by the presence of Qreiya Beds. These beds composed of thinly laminated phosphatic and organic-rich shale. These beds are characterized by sharp decrease in planktonic foraminiferal percentage, species richness and the relative abundance of foraminiferal species as well as calcareous nannofossil species (Text-figs. 7 and 8). Moreover, it is marked by dominance of the warm-water planktonic foraminiferal assemblages such as morozovellids (~60%), acarininids (~ 20%), and igorinids (~10%) (Boersma and Premoli, 1983; Boersma and Premoli, 1991; Pearson et al., 1993; Norris, 1996; Berggren and Norris, 1997; Soliman and Obaidalla, 2010). This faunal pattern is coinciding with low percentages of the cool-water species of parasubbotinids and subbotinids and other planktonic foraminiferal species (Fig. 6). The planktonic foraminiferal assemblages during this interval indicate warm climate during the deposition of the Qreiya Beds. The base of Qreiya Beds is marked by the abrupt incursion of Neoponides duwi which considered shallow water benthic foraminifera (e.g. Speijer, 2003; Guasti et al. 2005, 2006; Soliman and Obaidalla, 2013). Neoponides duwi was found to be in relatively low percentages below the event bed ~10-15% and abruptly increase to reach ~60% of total benthic foraminiferal assemblages during Qreiya Beds and decreased again in their abundance above these beds. This most probably indicate a sea level regression during the deposition of Qreiya Beds. The sea level regression during the D/S boundary was recorded in several sites worldwide (Knox, 1996; Mudge and Bujak, 1996; Lüning et al., 1998; Michelsen et al., 1998; Speijer, 2003; Clemmensen and Thomsen, 2005; Guasti et al., 2006). This might indicate that the VII- 14 The Danian/Selandian (D/S) Boundary Event At Gabal Serai,…… {{{{{{{{{{{{ fluctuation of the sea level during the D/S boundary due to eustatic change of the global sea level rather than tectonics (Obaidalla et al., 2009). In terms of calcareous nannofossil assemblages, the Qreiya Beds are marked by a warm climate during their deposition. This trend is indicated by the dominance of warm-water calcareous nannofossils species Ericsonia subpertusa (40-60%) and Coccolithus pelagicus (30-40%) while the cool-water indicators recorded a sharp decrease during this time interval (Fig. 8).
Fig. 6: Relative abundance of the planktonic foraminiferal genera throughout the D-S transition at the studied section According to Raffi and Rio (1981), Coccolithus pelagicus is considered dissolution- resistant species. This might explain its high abundance in the carbonate dissolution intervals during the deposition of the Qreiya Beds (Sprong et al., 2011) where the other calcareous nannofossil species are represented in very low percentages (Fig. 8). Coccolithus pelagicus is one of the incoming Paleogene species which evolved after the K/P mass extinction event. Coccolithus pelagicus is recorded nowadays in high abundance Soliman, H. A.; Faris, M., Obaidalla .N. A. and Metwally, A. A. VII- 15
in high productivity area of river mouths (Cachao and Moita, 2000) and in upwelling region (Okada and McIntyre, 1979). Ericsonia subpertusa has a similar structure to Coccolithus pelagicus and recorded in relatively high abundance during the same intervals of increasing abundance of Coccolithus pelagicus. On the basis of these criteria Ericsonia subpertusa might be also considered dissolution-resistant species (Monechi et al., 2013) and warm-water species (Aubry, 1998). A remarkable nannofossil turnover during the Qreiya Beds was noticed. It is represented by the first and relatively rare occurrence of Lithoptychius spp. Shortly after the FO of Lithoptychius spp. a second nannofossil turnover was recorded. This is represented by the first occurrence of Sphenolithus spp. which recorded at Bed 2 (sample no. 34) with relative abundance ranging between ~5 to 10% (Fig. 8). The presence of these taxa indicates warm surface water conditions (Haq and Lohman, 1976; Wei and Wise, 1990; Bralower, 2002; Tremolada and Bralower, 2004; Flores et al. 2005; Gibbs et al. 2006; Fuqua et al. 2008). However, the incursion of Neoponides duwi, high abundance of morozovelloids, Ericsonia subpertusa and Coccolithus pelagicus indicate that the Qreiya Beds in the present study at G. Sera were deposited in warm, shallow water with high productivity and upwelling activity.
3.3.2.3. Post-D/S boundary (Selandian sediments) This interval is marked by the recovery of planktonic foraminiferal and calcareous nannofossil assemblages. It is characterized by the replacement of praemuricids by morozovellids and acarininids and by the increased abundance of parasubbotinids and subbotinids to constitute about 50% of the total assemblages. This is indicating return to the normal conditions prior to the D/S boundary event (Fig. 6). The percentages of Neoponides duwi decreased during the Selandian time interval to the pre D/S boundary event probably indicating sea level transgression. Nannofloral assemblages during this time interval show increased in species richness (15- 23 species/sample). The relative abundance of the cool-water species Placozygus sigmoides, which ranging from 5 to 10% during the D/S boundary (Qreiya Beds) to reach ~20% above these beds, as well as the other cool-water indicators (Fig. 8). The cool-water Chiasmolithus spp. (Wei and Wise, 1990; Firth and Wise, 1992, Bralower, 2002) shows a marked increase in their relative abundance above the Qreiya Beds. It is ranging between ~10% below these beds and less than ~5% during the Qreiya Beds to reach about 20% above the D/S boundary (Fig. 8). However, the relative abundance of the warm-water nannofossil species in particular Ericsonia subpertusa and Coccolithus pelagicus notably decreased above the boundary event, suggesting a return to the cool climate conditions which prevailed during the pre D/S boundary.
VII- 16 The Danian/Selandian (D/S) Boundary Event At Gabal Serai,…… {{{{{{{{{{{{
Fig. 7: Planktonic/Benthonic (Planktonic %) ratio, foraminiferal abundance percentage and planktonic species richness of foraminiferal species throughout the D-S transition at the studied section
Soliman, H. A.; Faris, M., Obaidalla .N. A. and Metwally, A. A. VII- 17
Fig. 8: Relative abundance of selected calcareous nannofossil species and nannofossils species richness across the D-S transition at the studied section
VII- 18 The Danian/Selandian (D/S) Boundary Event At Gabal Serai,…… {{{{{{{{{{{{
CONCLUSION
A high resolution litho- and bio-stratigraphic investigation of the D-S transition of Gabal Serai cored section, Nile Valley resulted in: 1- The D/S boundary is located within the upper part of Dakhla Formation at the base of unique marker beds (Qreiya Beds) of ~30cm thick. The Qreiya Beds encompass four alternating gray and brown organic-rich shale. 2- Biostratigraphically, the D-S transition covered by six planktonic foraminiferal zones from P2 to P4b and four calcareous nannofossils zones/subzones from NP4a to NP6. The base of Qreiya Beds lies between the I. albeari/P. carinat /I. albeari planktonic foraminiferal zones boundary which equivalent to the nannofossil NP4a/NP4b subzonal boundaries. These zones indicate a continuous sedimentation across the D-S transition. 3- Quantitative analysis of microfossils assemblages (calcareous nannofossils and planktonic foraminifera) leads to recognition of three main intervals on the basis of microfossils change; pre-D/S (Danian), D/S boundary and post-D/S (Selandian). These intervals indicate that there is cool, normal marine conditions were prevailed below and above the D/S boundary. While warm, shallow water with high productivity and upwelling activity mark the deposition of Qreiya Beds at the D/S boundary.
ACKNOWLEDGEMENTS
We are especially grateful to Geologist Ahmed S. Marey, Quarry Manager, El-Nahda Cement Factory, Qena Government for his grateful help to obtain the Serai Core samples.
REFERENCES
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VII- 24 The Danian/Selandian (D/S) Boundary Event At Gabal Serai,…… {{{{{{{{{{{{
Plate 1 (Scale bar is 5 μm for all specimens)
(1) Placozygus sigmoides (Bramlette and Sullivan), Sample no. 39. (2) Ericsonia subpertusa (Hay and Mohler), Sample no. 6. (3) Ericsonia cava (Hay and Mohler), Sample no. 6. (4) Coccolithus pelagicus (Wallich), Sample no. 44, Gabal Serai. (5) Chiasmolithus danicus (Brotzen), Sample no. 19. (6) Chiasmolithus edentulus (van Heck and Prins), Sample no. 34. (7) Cruciplacolithus tenuis (Stradner), Sample no. 29. (8) Ellipsolithus macellus (Bramlette and Sullivan), Sample no. 12. (9) Neochiastozygus perfectus (Perch-Nielsen), Sample no. 43. (10) Diantholitha mariposa (Rodriguez and Aubry), Sample no. 30. (11) Lithoptychius collaris (Aubry and Rodriguez), Sample no. 38. (12) L. ulii (Perch-Nielsen), Sample no. 55. (13) L. stegastos (Aubry and Bourd), Sample no. 38. (14) L. felis (Aubry and Bourd), Sample no. 38. (15) Fasciculithus involutus (Bramlette and Sullivan), Sample no. 42. (16) Lithoptychius janii (Perch-Nielsen), Sample no. 40. (17) Fasciculithus bitectus (Romein), Sample no. 44. (18) Fasciculithus clinatus (Bukry), Sample no. 63. (19) Lithoptychius billii (Perch-Nielsen), Sample no. 40. (20) Fasciculithus tympaniformis (Hay and Mohler), Sample no. 45. (21) Sphenolithus primus (Perch-Nielsen), Sample no. 41. (22) Heliolithus kleinpellii (Sullivan), Sample no. 62. (23) Heliolithus cantabriae (Perch-Nielsen), Sample no. 62. (24) Zygodiscus bramlettei (Perch-Nielsen), Sample no. 61.
Soliman, H. A.; Faris, M., Obaidalla .N. A. and Metwally, A. A. VII- 25
Plate 1 VII- 26 The Danian/Selandian (D/S) Boundary Event At Gabal Serai,…… {{{{{{{{{{{{
Plate 2
(Scale bar is 100 μm for all specimens and 50μm for specimens 11 and 12) (1, 2) Parasubbotina variospira (Belford), Sample no. 50. (3,4) Praemuric carinata (El Naggar), Sample no. 15. (5,6) Praemurica inconstans (Subbotina), Sample no. 20. (7, 8) Praemurica uncinata (Bolli), Sample no. 3. (9, 10) Globanomalina pseudomenardii (Bolli), Sample no. 51. (11, 12) Igorina albeari (Cushman and Bermúdez), Sample no. 48. (13, 14) Morozovella angulata (White), Sample no. 16. (15, 16) Neoponides duwi (Nakkady) Sample no. 30.
EIGHTH INTERNATIONAL CONFERENCE ON THE GEOLOGY OF AFRICA P-P VII-27 - VII-54 (NOV. 2015) ASSIUT-EGYPT
BIOSTRATIGRAPHIC ZONATION AND EOCENE CHLOROPHYTAL ALGAE, ASSIUT-MINIA STRETCH, NILE VALLEY, EGYPT
Sobhi A. Helal* and Ahmed W. Hussein Geology Department, Faculty of Science, Fayoum University, Fayoum, Egypt *Corresponding author: [email protected]
ABSTRACT
The Early and Middle Eocene rocks at Assiut-Minia stretch are shallow marine limestones. These rocks consist of three rock units namely, Drunka, Minia and Samalut formations. Four algal and larger foraminiferal zones are recorded from these rocks namely in stratigraphic order Ovulites pyriformis/Ovulites arabica, Nummulites planulatus, Alveolina oblonga/Orbitolites complanatus and Nummulites gizehensis zones. Also, these rocks are characterized by high-diversified green algal floras (both Bryopsidales and Dasycladales). Nine Dasycladales taxa are identified (six of species-level and three of genus-level). They are Belzungia silvestrii (Pfender) Massieux, Cymopolia elongata (Defrance), Furcoporella diplopora Pia, Niloporella subglobosa Dragastan & Soliman, Clypeina cf. rotella Yu-Jing, Acicularia robusta Dragastan & Soliman, Dissocladella sp., Cymopolia sp. and Neomeris sp. A total of nine Bryopsidales (seven of species-level and two of genus-level) are recorded. They are represented by Ovulites pyriformis Schwager, Ovulites arabica (Pfender), Ovulites morelleti Elliott, Ovulites marginulata (Lamarck), Ovulites elongata Lamarck, Halimeda nana Pia, Halimeda praemonilis Morellet, Halimeda sp. and Ovulites sp. The paleoecological importance of the described algae is also discussed and deduced. Keywords: Biostratigraphy, green algae, Eocene, Nile Valley, Egypt.
1. INTRODUCTION
The area under study skirts the Nile Valley from the west in the vicinity of Assiut between Abu-Tig and Mallawi between latitudes 26º 27΄ & 27º 42΄ N. and longitudes 30º 41΄ & 31º 15΄ E. (FIG.1). The studied sequence belongs to the Early and Middle Eocene age. The recorded fossils are mainly belonging to the large foraminifera (e.g. Alveolinids, Orbitolites and Nummulites) and the benthonic fossil calcareous algae (chlorophytes and rhodophytes). The biostratigraphy of the surrounding areas was studied by several authors among them; Bishay (1966), Kenawy and El-Baradei (1977), Philobbos and Keheila (1979), Boukhary et al. (1982), Youssef et al. (1982), Boukhary and Abdel Malik (1983), Keheila (1983), Keheila et al. (1990) and Helal (1999). The main goals of this work is to make a biostratigraphic classification of this Early-Middle Eocene succession and to provide a detailed paleontologic study of the well-preserved fossil green algae. As the calcareous algae are most conveniently studied in thin sections, three hundreds and fifty thin sections were paleontologically analyzed for their microfloral content. VII- 82 Biostratigraphic Zonation And Eocene Chlorophytal Algae, …….
Fig. 1: Geological map of the study area (modified after EGPS and Conoco, 1987)
2. MATERIALS AND METHODS
About 300 rock samples were collected from four stratigraphic sections within the study area (FIG.1) from south to north; (1) El-Zarabi (south of Abu-Tig), (2) Ismail Bey (southwest of Assiut), (3) Gebel Gibeil (southwest of El-Qussiya) and (4) Mallawi (southwest of Mallawi). The carbonate succession of the present area is subdivided into Drunka (Early to Late Ypresian), Minia (Late Ypresian) and Samalut (Lutetian) formations (TABLE 1). The main lithologic characteristics of the recognized rock units and the proposed depositional environments are summarized in TABLE 2. As the calcareous algae are most conveniently studied in thin sections, three hundreds and fifty thin sections were paleontologically analyzed for their microfloral content. Sobhi A. Helal and Ahmed W. Hussein VII- 82
3. BIOSTRATIGRAPHIC ZONATION
On the basis of the distribution pattern of the recorded floral and faunal content, four zones are proposed (TABLE.3). These floral and faunal zones are correlated as shown in FIG.2. The distribution charts of the recognized taxa building up these zones are presented in FIGS.4-7.
Fig. 2: Biostratigraphic correlation of the fauni and flori zones.
Fig. 3 Legend for the carbonate constituents of the studied sections.
VII- 03 Biostratigraphic Zonation And Eocene Chlorophytal Algae, …….
3.1 Ovulites arabica/O. pyriformis algal Zone (acme zone): It is the oldest zone recognized in the Eocene succession of the study area. This zone (34 m) is defined by the high percentages of both Ovulites arabica (Pfender) and O. pyriformis Schwager. It is conformably underlies the Nummulites planulatus Zone. This zone is equivalent to the lower algal zone (Early Ypresian) described from the Drunka Formation in the Nile Valley by Dragastan & Soliman (2002). The fossil content of this zone is essentially composed of Ovulites arabica (Pfender) and O. pyriformis Schwager. Other fossil associated within this zone are O. morelleti Elliott, Acicularia robusta Dragastan & Soliman, Halimeda praemonilis Morellet, Niloporella subglobosa Dragastan & Soliman, Lithoporella melobesioides Fosile, Ovulites sp., Halimeda sp. and Cymopolia sp. The associated foraminiferal assemblage is represented by Orbitolites complanatus Lamarck, Quinqueloculina sp., Nummulites sp. Besides the previous fossils, the coprolite Favreina sp. is also recognized. On the basis of the fossil association and its stratigraphic attitude, the age of this zone is suggested herein as late Early Ypresian.
3.2 Nummulites planulatus foraminiferal Zone (total range zone): The Nummulites planulatus Zone is defined by the total range of the N. planulatus (Lamarck). The lower boundary of this zone coincides with the upper boundary of the lower unit of the Drunka Formation. It is underlain by the Ovulites arabica/O. pyriformis algal zone at El-Zarabi section and overlain by the Alveolina oblonga/Orbitolites complanatus foraminiferal zone of the Minia Formation at Gebel Gebeil. It measures about 99.75 m at El-Zarabi section, 35.5 m at Ismail Bey section and 48.5 m at Gebel Gibeil section. This zone is correlated with the Nummulites planulatus Zone of Bishay (1966) described from Wadi El-Assiuti area, N. planulatus Zone of Aref (1982) from the area southeast of Assiut and N. planulatus/N. burdigalensis Zone of Keheila et al. (1990) from the area southeast of Sohag. The fossil assemblage of this zone comprises the following foraminiferal taxa: Nummulites planulatus (Lamarck), Orbitolites complanatus Lamarck, Nummulites sp. and Quinqueloculina sp., while the associated algae includes Ovulites arabica (Pfender), O. pyriformis Schwager, O. marginulata (Lamarck), O. elongata Lamarck, O. morelleti Elliott, O. sp., Niloporella subglobosa Dragastan & Soliman, Acicularia robusta Dragastan & Soliman, Halimeda praemonilis Morellet, H. sp., Cymopolia sp., Neomeris sp. and Lithoporella melobesioides Fosile. Nummulites planulatus was defined from the Late Ypresian of Switzertland (Schaub, 1951) and France (Pomerol, 1973). It was described from the Late Ypresian from different localities of Egypt (Kenawy & El-Baradei, 1977; Kenawy et al., 1988; Keheila, 2000; Sheleby et al., 2000 and Dragastan & Soliman, 2002). According to the above discussion beside its stratigraphic position, the N. planulatus zone is assigned to the Late Ypresian age. The vertical variation in the distribution of the associated calcareous algae within the N. planulatus Zone allows its subdivision into three algal acme subzones; the Niloporella subglobosa Subzone (lower), Ovulites elongata Subzone(middle) and the Acicularia robusta/Ovulites spp. Subzone (upper).
3.2.1 Niloporella subglobosa algal subzone: This subzone is defined as the interval enriched with the Niloporella subglobosa Dragastan & Soliman. This subzone is recorded from the upper unit of the Drunka Formation exposed at El-Zarabi section (88m), where it conformably overlies the Sobhi A. Helal and Ahmed W. Hussein VII- 03
Ovulites arabica/O. pyriformis algal zone and underlies the O. elongata algal subzone. It is also recorded from the middle part of Ismail Bey section with a total thickness of 9.5m, where it is conformably overlain by the Acicularia robusta/Ovulites spp. algal subzone. This subzone is correlatable with the Carpathoporella occidentalis Zone described from the environs of Sohag (Keheila et al., 1990).
3.2.2 Ovulites elongata algal subzone: This subzone is recognized as the interval characterized by the high abundance of Ovulites elongata Lamarck beside the Nummulites planulatus (Lamarck). The Ovulites elongata Subzone is represented by the uppermost 11.75 m of the upper unit of the Drunka Formation exposed at El-Zarabi section. The lower boundary of this subzone is delineated at the upper part of the Niloporella subglobosa Subzone, while the upper boundary is delineated at the end of El-Zarabi section. This subzone is correlatable with the Ovulites elongata Zone of Keheila (1983 & 2000).
3.2.3 Acicularia robusta/Ovulites spp. algal subzone: This subzone is defined by the high abundance of the Nummulites planulatus (Lamarck), beside the dominance of Acicularia robusta Dragastan & Soliman and Ovulites spp. It is identified from the uppermost 14.5 m of the upper unit of the Drunka Formation exposed at the Ismail Bey section. This subzone overlies conformably the Niloporella subglobosa algal subzone at Ismail Bey section.
3.3 Alveolina oblonga/Orbitolites complanatus foraminiferal zone (interval zone): This zone is confined to the Minia Formation and attains about 31.5 m. It is marked by the first appearance of Alveolina oblonga d’Orbigny. It conformably overlies the Nummulites planulatus Zone of the upper unit of the Drunka Formation at Gebel Gibeil. The foraminiferal fossil assemblage of this zone is composed mostly of Alveolina oblonga d’Orbigny and Orbitolites complanatus Lamarck. The algal assemblage is represented by Belzungia silvestrii (Pfender) Massieux, Furcoporella diplopora Pia, Cymopolia elongata (Defrance), Clypeina cf. rotella Yu-Jing, Acicularia robusta Dragastan & Soliman, Cymopolia sp., Neomeris sp., Dissocladella sp., Halimeda praemonilis Morellet, Halimeda nana Pia, H. sp., Ovulites morelleti Elliott, O. sp., and Lithoporella melobesioides Fosile. This zone can be correlated with the Late Ypresian Alveolina oblonga, Orbitolites complanatus and Belzungia borneti zones proposed by Keheila (1983) from the area northeast of Assiut. Hottinger (1974) recorded the Alveolina oblonga d’Orbigny from the Late Ypresian of the main Tethyan sea (Southern Spain, Italy, Turkey and Egypt). Kuss & Herbig (1993) assigned the Alveolina oblonga Zone recorded from the area northeast of Egypt to the Late Ypresian (Cuisian) age. The Orbitolites complanatus Zone recorded from the Minia Formation outcropped northeast of Assiut was dated to the Late Ypresian (Keheila, 1983). According to the fossil content, this zone is assigned to the Late Ypresian age.
3.4 Nummulites gizehensis s.l foraminiferal zone (total range zone): This zone is defined to cover the stratigraphic interval of the nominate taxon. The stratigraphic range of the Nummulites gizehensis s.l confines to the Samalut Formation. It is the youngest zone recorded from the study area. It is confined to the Samalut Formation. The associated foraminifera are mainly Assilina sp., Discocyclina sp. and Quinqueloculina sp. The fossil algae are represented by VII- 08 Biostratigraphic Zonation And Eocene Chlorophytal Algae, …….
Lithoporella melobesioides Fosile, Lithothamnium sp. and Halimeda sp. The present Nummulites gizehensis s.l Zone can be correlated with that recognized from the Samalut Formation of the Nile Valley (Assiut-Minia) by Khalifa et al. (1986). The N. gizehensis Zone was dated back to the Lutetian age (Mansour & Philobbos, 1983 and Kenawy et al., 1993). In the present study, the zone is assigned to the Middle Eocene (Lutetian) in accordance with the previous studies.
4. TAXONOMY AND DESCRIPTION OF THE GREEN ALGAE
Eighteen chlorophytal algal taxa are identified and systematically studied as summarized in TABLE (4). The systematics of the chlorophytal green algae is based on the classification of Pia (1920) that was subsequently modified by Deloffre & Génot (1982), Bassoullet et al. (1983), Deloffre & Granier (1991 & 1993), Dragastan & Soliman (2002) and Granier et al. (2012). The Generic and specific distinction of the studied taxa are based on criteria including the shape and type of the thalus, the shape of the central stem and the shape and size of the first and second order branches.
Divsion CHLOROPHYTA Class CHLOROPHYCEAE Order DASYCLADALES Family THYRSOPORELLACEAE Granier & Bucur in Granier et al., 2012 Tribe THRYSOPORELLIDAE Pfender &Massieux, 1966 Genus BELZUNGIA Morellet, 1908 Belzungia silvestrii (Pfender, 1940) (FIG.8 A-E) 1960 Thrysoporella silvestrii Pfender- Elliott, p.227-230. 1966 Thrysoporella silvestrii Pfender- Pfender & Massieux, p.113, pl.1, figs.1,2. 1978 Belzungia silvestrii (Pfender)- Elliot, p.690. 1983 Belzunngia borneti Morellet- Keheila, pl.3, figs.5&6 and pl..4, figs.5&6. 1985 Trinocladus sp.- Khalifa, p.585, pl.1, fig.8. 1987 Belzungia silvestrii (Pfender) Massieux- Bandel & Kuss, p.24, pl.5, fig.8. 1987 Thyrsoporella silvestrii (Pfender)- Khalifa, p.87, pl.2, figs.17,18. 1989 Belzungia silvestrii (Pfender) Massieux- Kuss & Lepping, p.315, figs.9a,b. 1990 Belzungia silvestrii (Pfender) Massieux- Strougo et al., p.68, pl.2, fig.2. 1993 Belzungia silvestrii (Pfender) Massieux- Kuss & Herbig, p.272, pl.2, figs.1-3. 1997 Neomeris Johnsoni Khalifa- Basta, pl.8, fig.3. 2000 Belzungia silvestrii (Pfender) Massieux- Keheila, p.166, pl.3, fig.H. Occurrence: The dasycladacean green alga Belzungia silvestrii is recognized only from the Alveolina oblonga/Orbitolites complanatus Zone that was delineated from the Minia Formation. It is rare (<2.5%) to predominant (>40%) through Gebel Gibeil. The highest percentage of Belzungia silvestrii (55%) is recorded from the middle part of Gebel Gibeil. Description and dimensional data: The genera Belzungia, Thyrsoporella and Trinocladus are structurally similar. The discrimination between them depends upon general characters of the thallial tissue, the details of the branching and the dimentional data (d/D). Massieux (1966) stated that the Belzungia silvestrii is characterized by the irregular arrangement of its secondary branches. In the present work, thin sections of diverse orientations showing that the length (L) of the thallus of Belzungia silvestrii is reaching up to 2.6 mm. The average external diameter of the thallus (D) is 0.72 mm. It consists of elliptical to spherical unsegmented bodies Sobhi A. Helal and Ahmed W. Hussein VII- 00 with medium, spherical to cylindrical and slightly-calcified central stem. The average diameter of the central stem (d) in the transversal sections is 0.39 mm. The ratio d/D = 54%. The central stem exhibits a rounded edge with a moderately thick wall. It bears a series of parallel to semi-parallel primary branches. The primary branches are thick and their diameter (p1) ranges from 0.046 to 0.06 mm. They are occurring in regular whorls. Each of them ends with a package of irregular secondary branches. The secondary branches, in turn, end in a terminal hair representing clusters of tertiary branches. The diameter of the secondary branches (p2) ranges from 0.021 to 0.033 mm (i.e. the primaries are thicker than the secondaries). The sporangia are mainly globular and surrounded by the secondary branches. The average diameter and height of sporangia are 0.12 and 0.25 mm respectively. Perforation is sharp. Calcification is strong around the sporangia and envelopes the second order branches. Distribution and stratigraphic range: Belzungia silvestrii was first defined by Pfender (1940) from the Lower Eocene succession of the Nile Valley. It was also recorded from the Lower Eocene rocks of Egypt by Pfender & Massieux (1966), Bandel & Kuss (1987), Kuss & Lepping (1989), Strougo et al. (1990) and Kuss & Herbig (1993) recorded this species from the Lower Eocene sediments of the Eastern Desert of Egypt. Outside Egypt, this species was recorded from the Eocene rocks of Bretagne and Contentin (Morellet, 1917 & 1940), from the Eocene of Somali (Pfender & Massieux, 1966) and from the Paleocene rocks of Kurdistan (Elliott, 1978). Deloffre & Genot (1982) stated that the stratigraphic range of the Belzungia silvestrii ranges from the Paleocene to the Lower Eocene. Family TRIPLOPORELLACEAE Pia, 1920 Genus DISSOCLADELLA Pia, 1936 Dissocladella sp. (FIG.8 F-H) Occurrence: It is rare at the middle part of the Alveolina oblonga/Orbitolites complanatus Zone (Minia Formation) at Gebel Gibeil. Description and dimensional data: The thallus is elongate to cylindrical with L reaches up to 2 mm and average D = 0.48 mm and with elliptical to spherical central stem (average d = 0.27 mm), from which two orders of branches are arisen. The ratio d/D = 56%. Such branches arrange perpendicular to the central stem. The diameter of the primary branches (p1) = 0.025-0.047 mm and that of the secondary branches (p2) = 0.008-0.15 mm. The present Dissocladella spp. may be segments of Dissocladella longijangensis Mu & Wang. Distribution and stratigraphic range: Dissocladella sp. was discerned from Egypt by Kuss & Herbig (1993) from the Cuisian of the Northern Galala, Eastern Desert.
Family DASYCLADACEAE Kützing, 1843 Tribe CYMOPOLIEAE Valet, 1968 Genus CYMOPOLIA Lamouroux, 1816 Cymopolia elongata (Defrance, 1825) (FIG.8 I&J) 1974 Cymopolia elongata (Defrance)- Genot & Poignant, p.70, pl.2, figs.1-6. 1978 Cymopolia kurdistanensis Elliott- Elliott, p.154, pl.10, fig.3. 1980 Cymopolia elongata (Defrance)- Genot, p.17, pl.1, figs.1-12 & pl.3, figs.6-9. 1987 Cymopolia pacifica Johnson- Khalifa, p.90, pl.1, fig.11. 1989 Cymopolia elongata (Defrance)- Kuss & Leppig, p.317, figs.9d,e. VII- 03 Biostratigraphic Zonation And Eocene Chlorophytal Algae, …….
1991 Cymopolia sp. –Herbig, pl.1, figs.5-7. 1993 Cymopolia elongata (Defrance)- Kuss & Herbig, p.272, pl.2, figs.4-8. 2000 Cymopolia elongata (Defrance)- El-Gamal & Youssef, p.1425, pl.2, fig.E, pl.3, figs.A-C. Occurrence: Cymopolia elongata is restricted to the Minia Formation, whereas it is rarely observed in the middle part of the Alveolina oblonga/Orbitolites complanatus Zone at Gebel Gibeil. Description and dimensional data: The cross sections of the Cymopolia elongata show that the thallus develops as branching segmented bodies that are elliptical to spheroid in shape with well-rounded peripheries. It exhibits average D = 0.55 mm. The plant consists of an elliptical central stem (average d = 0.31 mm) (d/D = 56%), from which short and thick-walled primary and secondary branches arise. The hollow of the central stem is usually filled with micrite that may be converted into micro- and pseudospar due to the aggrading neomorphism. Each primary branch (average p1 = 0.03 mm) has usually two second order branches (average p2 = 0.017 mm), surrounding the ovoid to spheroidal sporangia (average diameter = 0.28 mm). Sporangia are ovoid, spherical or pyriform, growing at the end of the pronounced secondary branches. Calcification is almost absent around the central stem. Distribution and stratigraphic range: Elliott (1968) reported that the Cymopolia elongata was identified from the Upper Paleocene-Lower Eocene of the Middle East Genot (1980) described the C. elongata from the Thanetian carbonates of the Parisian Basin. From Egypt, the C. elongata was identified from Upper Paleocene to Lower Eocene carbonate sequence of northeast Egypt (Kuss & Leppig, 1989; Kuss & Herbig, 1993 and El-Gamal & Youssef, 2000). Cymopolia sp. (FIG.8K) Occurrence: It is predominant in the basal part of the Nummulites planulatus Zone (Niloporella subglobosa Subzone) of El-Zarabi section and the middle part of Ismail Bey section and rare in the Alveolina oblonga/Orbitolites complanatus Zone. Description and dimensional data: The strongly-calcitized thallus (average D = 1 mm) of the transversal sections is cylindrical to elliptical with ovoidal central stem (average d = 0.5 mm). The ratio d/D = 50%. The primary branches are long and thick (average p1 = 0.52 mm), from which thick secondary branches arise (average p2 = 0.28 mm). The intensive recrystallization results in obliterating the details of the thallus, thus the specific name of the taxa is impossible to be defined.
Family TRIPLOPORELLACEAE Pia, 1920 Tribe MACROPORELLINEAE Pfender & Massieux, 1966 Genus FURCOPORELLA Pia, 1918 Furcoporella diplopora Pia, 1918 (FIG.8 L&M) 1940 Furcoporella diplopora Pia- Pfender, pp.242-243 1956 Furcoporella diplopora Pia- Elliott, p.331, pl.2, figs.5,6. 1966 Furcoporella diplopora Pia- Pfender & Massieux, p.128, pl.4, figs.8,9. 1979 Furcoporella diplopora Pia- Racz, p.721, fig.2. 1987 Furcoporella diplopora Pia- Khalifa, p.88, pl.2, figs.9, 13, 14. 1993 Furcoporella diplopora Pia- Kuss & Herbig, p.274, pl.6, figs.4-5 & 7-8. Occurrence: Furcoporella diplopora is restricted to the middle part of the Alveolina oblonga/Orbitolites complanatus Zone (Minia Formation), whereas it is recorded with percentage not exceed than 2.5% of the rock. Sobhi A. Helal and Ahmed W. Hussein VII- 03
Description and dimensional data: Gymnocodium nummuliticum, Furcoporella diplopora and Griphoporella arabica are closely related. Elliott (1956) noticed that the Furcoporella diplopora has the largest dimensions among the three above- mentioned species. In the studied Furcoporella diplopora, the thallial tissue (L = up to 2.3 mm and average D = 0.44 mm) is cylindrical, unsegmented and strongly calcified around the hollow central stem. The average diameter of the center stem (d) = 0.2 mm. The ratio d/D = 45%. Short and thick primary branches (average p1 = 0.06 mm) are developed, which pass into two thin secondary branches (average p2 = 0.017 mm). Globular sporal verticlis with average diameter = 0.05 mm are horizontally arranged with short primary canals. These pores are found at right angles to the axial area. Distribution and stratigraphic range: Furcoporella diplopora was recorded from the ?Middle Eocene carbonates of Gebel El-Teir, opposite Minia (Khalifa, 1987) and from the Lower Eocene of the north Eastern Desert (Kuss & Leppig, 1989 and Kuss & Herbig, 1993). Outside Egypt, Pia (1918) was the first to identify this species from the Upper Paleocene to Middle Eocene of Austria. Bassoullet et al. (1983) defined and described this species from the Middle East and China.
Family TRIPLOPORELLACEAE Pia, 1920 Tribe DASYCLADEAE Pia, 1920 Genus NILOPORELLA Dragastan & Soliman, 2002 Niloporella subglobosa Dragastan & Soliman, 2002 (FIG.8 N-Q) 1983 Carpathoporella occidentalis Dragastan- Keheila, pl.5, fig.12. 1986 Sarfatiella sp.- Segonzac et al., p.506, pl.2, fig.2. 1990 Carpathoporella occidentalis Dragastan- Keheila et al., p.163, figs. 11D-G. 1990 Sarfatiella sp.- Radoičić, pl.10, figs.5-7. 1993 Acicularia sp.- Kuss & Herbig, pl.6, fig.16. 2002 Niloporella subglobosa n.sp.-Dragastan & Soliman, pp.7-9, pl.3, fig.1-12. Occurrence: Niloporella subglobosa is rare in the lower unit of the Drunka Formation at El-Zarabi section (Ovulites arabica/Ovulites pyriformis Zone). Its percentage ranges from 2.5% to > 40% in the upper unit of the Drunka Formation exposed at El-Zarabi, Ismail Bey and Gebel Gibeil sections (Nummulites planulatus Zone). The highest percentage of Niloporella subglobosa (40%) is recorded at the basal part of the upper unit of the Drunka Formation at El-Zarabi section. Description and dimensional data: Dragastan & Soliman (2002) mentioned that the new species Niloporella subglobosa is correlated with Morelletopora nammalensis Varma and Piania niniyurensis Gowda but with some difference in the shape and arrangement of the ampoules. In the present work, the thallus (L = up to 1.5 mm and average D = 0.75 mm) is well-developped, unsegmented, cylindrical, crossed by axial siphons bearing numerous euspondyle verticils, sometimes heavily- recrystallized. In the transversal sections, the axial siphon is surrounded by 6-10 globular ramifications. The central stem (axial cavity) is spheroidal in cross sections and exhibits average d = 0.35 mm. The ratio d/D = 47%. The supposedly fertile laterals ramifications (ampullae) are globular to subglobular and present in widely- spaced whorls. Their average diameter is about 0.2 mm. They are flattened in the longitudinal sections and widen at the tips and support a cortical membrane. Distribution and stratigraphic range: Niloporella subglobosa was introduced by Dragastan & Soliman (2002) from the Lower Eocene Drunka Formation exposed in the area between Qena and Sohag, Egypt. VII- 03 Biostratigraphic Zonation And Eocene Chlorophytal Algae, …….
Family DASYCLADACEAE Kützing, 1843 Tribe NEOMEREAE Pfender & Massieux, 1966 Genus NEOMERIS (Pia, 1920) Bassoulet et al., 1979 Neomeris sp. (FIG.9 A) Occurrence: It is predominant from one bed at the middle part of the Nummulites planulatus zone of the upper unit of the Drunka Formation at both Ismail Bey and Gebel Gibeil sections. Also, it is rare from the middle part of the Alveolina oblonga/Orbitolites complanatus Zone of the Minia Formation.
Description and dimensional data: The test is strongly recrystallized, subcylindrical with no annular narrowing. The thallus is characterized by its egg- shaped, globular, calcreous capsules (sporangia) with average diameter = 0.16 mm. Such sporangia are separated by infertile branches that are often overprinted by the diagenetic alterations. Distribution and stratigraphic range: Different species of Neomeris (N. avellanensis, N. plagnensis, N. cf. reticulata, N. scrobiculata, N. cf. tyrrhenica, N. budaense, N. johonsoni and N. mirensis) were identified from the Upper Paleocene to Lower Eocene limestones of the Nile Valley and north Eastern Desert of Egypt (e.g. Khalifa, 1985; Khalifa et al., 1986; Mansour et al., 1987 and Kuss & Hebrig, 1993). Such species was noticed from the Late Paleocene to Ypresian of Morocco, Sardinia and Iran (Deloffre et al., 1977 and Granier et al., 2012). Family POLYPHYSACEAE Kützing, 1843 Tribe CLYPEINEAE Elliot, 1968 Genus CLYPEINA (Michelin, 1845) Bassoulet et al., 1978 Clypeina cf. rotella Yu-Jing, 1976 (FIG.9 B) 1990 Clypeina haglani Radoičić- Radoičić, pl.3, figs.1-5. 2002 Clypeina cf. rotella Yu-Jing- Dragastan & Soliman, p.9, pl.2, fig.2. Occurrence: It is rare and defined from the Alveolina oblonga/Orbitolites complanatus Zone of the Minia Formation. Description and dimensional data: Thallus is recrystallized showing about 18-20 sporangial ramifications. It shows small disc with average D = 0.96 mm, average d = 0.5 mm and d/D = 52% with globular fertile capsules (sporangia) with average diameter = 0.15 mm. Distribution and stratigraphic range: Dragastan & Soliman (2002) identified this species from the Lower Eocene Drunka Formation of south Assiut (Egypt).
Tribe ACETABULARIEAE Decaisne, 1842 Genus ACICULARIA d'Archiac, 1843 Acicularia robusta Dragastan and Soliman, 2002 (FIG.9 C) 1990 Acicularia sp.- Radoičić, pl.12, fig.6. 1994 Acicularia sp.- Herbig & Fechner, figs.5&6C. 2002 Acicularia robusta n.sp.- Dragastan & Soliman, p.12, pl.1, figs.4&5. Occurrence: Acicularia robusta was perceived from all the studied sections. The highest percentage of this species (45%) was recorded in the lowermost bed of Acicularia robusta/Ovulites spp. Subzone (Nummulites palnulatus zone), that is recognized from the upper part of the Drunka Formation at Ismail Bey section. Sobhi A. Helal and Ahmed W. Hussein VII- 03
Description and dimensional data: Acicularia robusta was first named by Dragastan & Soliman (2002) who stated that the species of the genus Acicularia are identified by the shape of their fertile ampoules. Numerous sporangiphore bioclasts are recorded herein. They are calcified and rounded in the transversal sections to elongated in the other sections with flattened tops and bottoms. Such sporangiphores are composed of 6-20 spherical fertile ampoules (cyst cavities) with average diameter = 0.014 mm. These cyst cavities are thick and concentrically arranged around the periphery. Distribution and stratigraphic range: The new species Acicularia robusta was distinguished from the Upper Ypresian carbonates of the Drunka Formation of the Nile Valley, Egypt (Dragastan & Soliman, 2002).
Class BRYOPSIDOPHYCEAE Order BRYOPSIDALES Family UDOTEACEAE Feldman, 1946 Genus OVULITES Lamarck, 1816 Ovulites pyriformis Schwager, 1883 (FIG.9 D-F) 1989 Ovulites pyriformis Schwager- Kuss & Leppig, p.324, fig.10c. 1990 Ovulites maillolensis Morellet- Keheila et al., p.163, figs.11Q-S. 2000 Ovulites maillolensis Morellet- El-Gamal & Youssef, p.1427, pl.4, fig.f. 1993 Ovulites pyriformis Schwager- Kuss & Herbig, p.277, pl.5, fig.11. 2002 Ovulites pyriformis Schwager- Dragastan & Soliman, p.14, pl.4, figs.4-7. Occurrence: This species is recorded frequently from the Drunka Formation at both El-Zarabi and Ismail Bey sections. The highest percentage of Ovulites pyriformis (45%) is recorded at the lower part of the lower unit of the Drunka Formation at El-Zarabi section (Ovulites arabica/Ovulites pyriformis algal zone). Description and dimensional data: Ovulites pyriformis exhibits the largest diameter among the other species of Ovulites (Kuss & Herbig, 1993). In the present study, Ovulites pyriformis is characterized by its pear shape (average D = 1.6 mm). It has a thin cortex (0.02 mm), which is pierced by very short siphons. The average diameter of the central cavity (d) = 1.3 mm. The ratio d/D = 81%. Distribution and stratigraphic range: Kuss & Herbig (1993) identified the Ovulites pyriformis from the Upper Paleocene to Lower Eocene strata of the lagoonal facies of Sinai and the Southern Galala on both sides of the Gulf of Suez. Dragastan & Soliman (2002) described this species from their lower algal zone described from the Drunka Formation exposed at the Nile Valley and dated this zone to the late Early Ypresian.
Ovulites arabica (Pfender, 1938) (FIG.9 G & H) 1966 Ovulites arabica (Pfender)- Massieux, pp.240-242, tab.1. 1968 Griphoporella arabica (Pfender)- Elliott, p.51, pl.12, figs.1&3. 1989 Ovulites arabica (Pfender)- Kuss & Leppig, p.323, fig.11a. 1991 Ovulites arabica (Pfender)- Herbig, p.33, pl.8, fig.5. 1992 Ovulites sp.- Radoičić, pl.8, fig.10. 1993 Ovulites arabica (Pfender)- Kuss & Herbig, p.277, pl.5, figs.10, 13-14 & pl.8, fig.6. 2002 Ovulites arabica (Pfender)- Dragastan & Soliman, p.12, pl.4, figs.1-3. VII- 02 Biostratigraphic Zonation And Eocene Chlorophytal Algae, …….
Occurrence: This species is realized from the Drunka Formation at both El-Zarabi and Ismail Bey sections with variable percentages. The highest percentage of Ovulites arabica (55%) is recorded at the upper part of the lower unit of the Drunka Formation at El-Zarabi section (Ovulites arabica/Ovulites pyriformis algal zone). Description and dimensional data: Ovulites arabica is characterized from O. pyriformis by its thicker cortex. In oblique sections, the plant is circular with average diameter D = 1.2 mm. It has a thin calcitizied cortex (0.075 mm). This cortex is perforated by vertical crossing minute canals (short siphons). The average diameter of the central cavity (d) = 0.82 mm. The ratio d/D = 68%. Distribution and stratigraphic range: Ovulites arabica was defined firstly by Pfender (1938) from the Middle Eocene of Egypt and Lower Eocene of Morocco. It was recognized from the Upper Paleocene/Lower Eocene of north Eastern Desert, Egypt (Kuss & Leppig, 1989). Also, it is identified from the Illerdian limestones of south Assiut, Nile Valley, Egypt (Dragastan & Soliman, 2002).
Ovulites morelleti Elliott, 1955 (FIG.9 I & J) 1986 Ovulites morelleti Elliott- Khalifa et al., pp.152&153, pl.1, figs.6-9. 1987 Ovulites morelleti Elliott- Bandel & Kuss, p.25, pl.5, fig.5. 1987 Ovulites morelleti Elliott- Khalifa, p.89, pl.2, figs.1&2. 1987 Ovulites morelleti Elliott- Mansour et al., p.132, pl.1, fig.6. 1989 Ovulites morelleti Elliott- Kuss & Leppig, p.323, figs.10f&g. 1990 Ovulites morelleti Elliott- Radoičić, pl.11, figs.2&3. 1993 Ovulites morelleti Elliott- Kuss & Herbig, p.277, pl.5, figs.9&12. 2000 Ovulites morelleti Elliott- El-Gamal & Youssef, p.1428, pl.2, fig.A & pl.4, figs.D&E. Occurrence: This species is discerned from both the Ovulites arabica/Ovulites pyriformis algal zone (<2.5%) and the Nummulites palnulatus zone (up to 5%) of the Drunka Formation exposed at El-Zarabi and Ismail Bey sections. Also, it is recorded with percentage < 2.5% from the Alveolina oblonga/Orbitolites complanatus zone of the Minia Formation. Description and dimensional data: Thallus is segmented. It is elongate in the longitudinal sections and circular to tabular in the cross sections. The wall of the thallus is insignificantly perforated with straight and radial pores. The average L reaches up to 2.5 mm, the average outer diameter (D) = 1.4 mm, the average inner diameter (d) = 0.6 mm and d/D = 43%. Distribution and stratigraphic range: Ovulites morelleti was distinguished from the Upper Ypresian Drunka Formation of the Nile Valley, Egypt (Mansour et al., 1987). It was described from the ?Middle Eocene Minia Formation of the Nile Valley (Khalifa et al., 1986 and Khalifa, 1987). Also, it is recorded from the Upper Paleocene to Lower Eocene of north Eastern Desert (Bandel & Kuss, 1987 and Kuss & Herbig, 1993 and El-Gamal & Youssef, 2000). Outside Egypt, Elliott (1955) and Radoičić (1990) identified this species from the Upper Paleocene to Middle Eocene of the Middle East and the subsurface of the Western Iraq Desert respectively.
Ovulites marginulata (Lamarck, 1801) Lamarck, 1816 (FIG.9 K) 1966 Ovulites marginulata Lamarck- Massieux, pp.241-244, pl.1, figs.1-4. 1970 Ovulites marginulata Lamarck- Deloffre, p.355, pl.1, figs.1-8. Sobhi A. Helal and Ahmed W. Hussein VII- 02
1993 Ovulites marginulata Lamarck- Kuss & Herbig, p.277, pl.8, figs.7&8. 2002 Ovulites marginulata Lamarck- Dragastan & Soliman, p.14, pl.4, figs.8-11 & pl.6, fig.5. Occurrence: It is constrained to the Nummulites planulatus Zone of the Drunka Formation. Its highest percentage (10%) was observed at the middle part of Ismail Bey section. Description and dimensional data: The thallus segment is of ovoid to pear shape with average outer diameter (D) = 0.85 mm and average inner diameter (d) = 0.78 mm and d/D = 92%. Such thallus is walled by thin cortex with diameter = 0.014- 0.025 mm. The cortical film is cut by very fine, tabular siphons. In the oblique tangential section, it is obvious that the siphons are arranged in rows. Distribution and stratigraphic range: Deloffre (1970) ascertained this species from the Lower Eocene of the French Pyreneés. Ovulites marginulata was known from central High Atlas region of Morocco (Trappe, 1992). Kuss & Herbig (1993) and Dragastan & Soliman (2002) defined this species from the Ypresian limestones of north Eastern Desert and Nile Valley respectively.
Ovulites elongata Lamarck, 1816 (FIG.9 L-N) 1966 Ovulites elongata Lamarck- Massieux, pp.241&241, tab.1. 1983 Ovulites elongata Lamarck- Bassoullet et al., p.540, pl.12, figs.1&2. 1990 Ovulites elongata Lamarck- Keheila et al., p.163, figs.11O&U. 1990 Ovulites elongata Lamarck- Strougo et al., p.68, pl.1, figs.1&2. 2000 Ovulites elongata Lamarck- Keheila, p.166, pl.3, fig.H. 2002 Ovulites elongata Lamarck- Dragastan & Soliman, p.16, pl.5, figs.1-6. Occurrence: Ovulites elongata is limited to the Nummulites planulatus Zone of the Drunka Foramation at El-Zarabi section. The highest percentage of Ovulites elongata (25%) is recorded at the uppermost part of this section (Ovulites elongata algal subzone). Description and dimensional data: In longitudinal sections, the thallus is long, cylindrical and intensely calcitizied with average L = up to 1.7 mm. The cross sections are heavily micritized exhibiting circular shape with average diameter (D) = 0.225 mm. The average diameter of central cavity (d) = 0.175 mm. The ratio d/D = 78%. The cortical layer is very thin, that is punctured by short siphons (0.05 mm). Distribution and stratigraphic range: This species was apprehended from the Ypresian-Lutetian carbonates of the Nile Valley and north Eastern Ddesert (Keheila et al., 1990; Strougo et al., 1990; Keheila, 2000 and Dragastan & Soliman, 2002). It was identified from the Ypresian of Morocco (Bassoulett et al., 1983).
Ovulites sp. Occurrence: It is recognized from the Ovulites arabica/Ovulites pyriformis algal zone of the Drunka Formation at El-Zarabi section with percentage not exceed 2.5%. It is also noticed from the Nummulites planulatus Zone at El-Zarabi, Ismail Bey and Gebel Gibeil sections with highest percentage reaches up to 45% at the middle part of Gebel Gibeil. Also, it is rarely recorded (<2.5%) from the Alveolina oblonga/Orbitolites complanatus Zone of the Minia Formation. Description and dimensional data: Thallus is segmented with small globular to cylindrical bodies. In cross sections, it is differentiated into dark central stem and thin outer cortex. Thallus is perforated by numerous fine pores. The dimensional VII- 33 Biostratigraphic Zonation And Eocene Chlorophytal Algae, ……. data of this genus doesn't correspond to any of the aforementioned Ovulites species, therefore, no specific name can be attained.
Family HALIMEDACEAE Link, 1832 Genus HALIMEDA Lamouroux, 1812 Halimeda nana Pia, 1932 (FIG.9 O-Q) 1955 Halimeda nana Pia- Elliott, p.131, pl.1,fig.3. 1983 Halimeda nana Pia- Bassoulett et al., pp.499-490, pl.7, figs.5&6. 1986 Halimeda nana Pia- Segonzac et al., p.502, pl.I, figs.1,2, 5,7&8. 1993 Halimeda nana Pia- Kuss & Herbig, p.277, pl.5, figs.1-5&8 &pl.8, figs.4- 5&9-10. Occurrence: It is rare (<2.5%) from the middle part of Alveolina oblonga/Orbitolites complanatus Zone of the Minia Formation. Description and dimensional data: Thallus is segmented with L reaches up to 2.2 mm and average outer diameter D = 0.9 mm. It is heavily recrystallized (calcitizied and/or micritized). In cross sections, the segment has a discoidal shape with undulating edges and cut by circular to ovoidal medullar filaments. In vertical sections, the central cavity consists of thick, tabular filaments (0.07 mm), which continue to bifurcated threads of the cortex. Distribution and stratigraphic range: Halimeda nana was recorded from the Upper Paleocene to Lowe Eocene of Egypt and Morocco (Kuss & Leppig, 1989 and Kuss & Herbig, 1993).
Halimeda praemonilis Morellet, 1940 (FIG.9 R & S) 1968 Halimeda praemonilis Morellet- Johnson, p.43, pl.30, fig.3. 1977 Halimeda praemonilis Morellet- Deloffre et al., p.43, pl.6, figs.1&2. 1986 Halimeda praemonilis Morellet- Khalifa et al., p. 153, pl.1, figs.15,20&22. 1990 Halimeda praemonilis Morellet- Keheila et al., p.163, figs.11A,M&T. 1990 Halimeda praemonilis Morellet- Radoičić, pl.12, figs1&2. Occurrence: Halimeda praemonilis is present (2.5-5%) to abundant (10-20%) from the Nummulites planulatus zone of the Drunka Foramation at El-Zarabi section and is rare (<2.5%) from the Alveolina oblonga/Orbitolites complanatus of the Minia Formation at Gebel Gibeil. Description and dimensional data: Thallus is composed of tufts of segmented branching stems with L reaches up to 5.5 mm and average diameter (D) = 1 mm. The segment is leaf-like, subcylindrical to subconical, which is strongly micritized. The internal structure is composed of medullar, tabular filaments in the longitudinal sections. The filaments are finer and shorter towards the outer surface of the segment. Distribution and stratigraphic range: Halimeda praemonilis was comprehended from the Lower-Middle Eocene of the Nile Valley and Eastern Desert (Khalifa et al., 1986 and Keheila et al., 1990).
Halimeda sp. (FIG.9 T) The highest percentage of Halimeda sp. (25%) was recorded from the middle part of Alveolina oblonga/Orbitolites complanatus of the Minia Formation. It is also Sobhi A. Helal and Ahmed W. Hussein VII- 33 identified from the Nummulites planulatus Zone of the Drunka Foramation at El- Zarabi section and the Nummulites gizehensis s.l Zone of the Samalut Formation with percentage not exceed than 10%. The thallus is heavily calcitized, accordingly, the specific name is impossible to be determined.
5. PALEOECOLOGICAL PARAMETERS
The most suitable conditions for the growth of green algae are the shallow to very shallow, semi-restricted to restricted, clear water and warm marine limy platform areas (Elliott, 1955 and Neumann & Land, 1975 and Granier, 2012).
5.1 Salinity: The Bryopsidales are living in an environment of normal marine to slightly variable salinity (Wilson, 1975 and Wray, 1977), while the Dasycladales are living in an environment of variable salinity (Wilson, 1975), mostly normal marine with less extent hypersaline to brackish (Wray, 1977). The carbonate succession of the area under consideration is believed to be deposited under normal marine to slightly hypersaline conditions as indicated by the dominance of the calcareous green algae.
5.2 Water depth: Living Bryopsidales thrive best in shallow depths of the subtidal environment from low tide level and down to a range from 10-20 m (Wilson, 1975 and Wray, 1977). The alga Halimeda could not grow beyond the photic zone (70-90 m depth) (Roberts et al., 1987 and Phipps and Roberts, 1988). It can grow and calcify at depths below 100m (Granier, 2012). Dasycladales flourish in shallow marine conditions (Elliott, 1968) with depth ranging from low tide to about 12 m (Pia, 1920 and Horowitz and Potter, 1971), 13-15 m (Wilson, 1975) and below the low tide to about 30 m, commonly < 5 m (Flugel, 1977 and Wray, 1977). Milliman (1974) stated that the dasycladacean algae are growing in depth not greater than 15-20 m. In the present work, the presence of high percentage of calcareous green algae within the studied carbonate sequence indicates that the water depth is shallow (average depth of about 20 m) within the photic zone below the turbulence zone. In this zone, the well-oxygenated water and the photosynthetic zone were available.
5.3 Temperature: Most of the Bryopsidales live in warm water in the tropical area (25oC + isotherm) (Johnson, 1961 and Wray, 1977). Few species of Halimeda live in the subtropical regions (Wray, 1977). In this respect, Roux (1985) revealed that the codiacean green algae are thriving best in warm conditions (minimum 18oC). Living dasycladales are distributed in warm waters of tropical and subtropical areas and few species are living in temperate water (Flugel, 1977 and Wray, 1977). The dominance of green algae within the studied rock units suggests that they were deposited under warm and tropical to subtropical conditions.
5.4 Water energy: The dominance of the calcareous green algae and unwinnowed thick micrite indicate a short lived current with low energy (Folk, 1962). Ginsburg et al. (1971) and Wilson (1975) revealed that the flourishing of the Bryopsidales does not require strong circulation. They are flourishing under low energy conditions below the intense water agitation (Wray, 1977). Living Cymopolia and Neomeris can be found in high energy (reef) environments (Granier, 1988). The Dasycladales are flourishing in an environment of low energy level below intense wave agitation VII- 38 Biostratigraphic Zonation And Eocene Chlorophytal Algae, …….
(Wray, 1977). Consequently, the studied carbonates are seemed to be deposited in quiet water conditions.
6. CONCLUSION
The Lower and Middle Eocene carbonate sequence of the Assiut-Minia stretch can be subdivided into one algal zone and three large foraminiferal zones. The Ovulites arabica/Ovulites pyriformis Zone (Early Ypresian) is confined to the lower unit of the Drunka Formation. The foraminiferal zones are represented by the following zones (from older to younger); Nummulites planulatus and Alveolina oblonga/Orbitolites complanatus zones of Late Ypresian age and Nummulites gizehensis Zone of Lutetian age. Furthermore, the Nummulites planulatus zone is subdivided into three algal subzones. These are (from base top); Niloporella subglobosa Subzone. Ovulites elongate Subzone and Acicularia robusta/Ovulites spp. Subzone. A total of thirteen green algal species and five genera were identified, described, measured and discussed. They are Belzungia silvestrii (Pfender), Cymopolia elongata (Defrance), Furcoporella diplopora Pia, Niloporella subglobosa Dragastan & Soliman, Clypeina cf. rotella Yu-Jing, Acicularia robusta Dragastan & Soliman, Dissocldella sp., Cymopolia sp. and Neomeris sp., Ovulites pyriformis Schwager, Ovulites arabica (Pfender), Ovulites morelleti Elliott, Ovulites marginulata (Lamarck), Ovulites elongata Lamarck, Halimeda nana Pia, Halimeda praemonilis Morellet, Halimeda sp. and Ovulites sp. The paleoecological conditions of the studied rock units are deduced depending upon the ecology of the cholorophytal algae. Hence, the studied carbonate sequence was probably deposited in normal marine to slightly hypersaline conditions with shallow water depth (about 20 m) and warm and quiet water.
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Pfender, J., Massieux, M., 1966. Les algues du Nummulitique Égyptien et des terrains Cretacées-Éocènes de quelques régions mésogéennes. Revue de Micropaleontologie, 9 (2), 111-135. Philobbos, E.R., Keheila, E.A., 1979. Depositional environments of the Middle Eocene in the area southeast of Minia, Egypt. Ann. Geol. Surv., Cairo, Egypt, IX, 523-550. Phipps, C.W., Roberts, H.H., 1988. Seismic characteristics and accretion history of Halimeda bioherms on Kalukalukaung Bark, Eastern Java Sea (Indonesia). Coral Reef, 6, 149-159. Pia, J., 1918. Tthallophyta, dasycladaceae. In: Trauth, F. Das Eocänvorkommen bei radstadt in Pongau, Denkschr. Akad. Wiss. Wien, 95, Wien. Pia, J., 1920. Die Siphoneae verticillatae vom Karbon bis Zur Kreide: Abhandlungen. Zool. - Bot. Gessell. Wien, 11, 1-263. Pomerol, C., 1973. Ere Cènozoique (Tertiaire et Quaternaire). Stratigraphie et paleogeographie, Ere Cènozoique (Tertiaire et Quaternaire), Doin ed., Paris, 269 p., 235 text figs. Radoičić, R., 1990. Paleogene dasyeladecean algae from the subsurface of the Western Iraqi Desert. Bull. De l’Académie serbe des sciences et des arts (sciences mathematiques et naturelles), Beograd, T. CII, 32, 91-103. Roberts, H.H., Phipps, C.W., Effendi, L., 1987. Halimeda bioherms of the Eastern Java Sea, Indoensia. Geology, 15: 371-374. Roux, A., 1985. Introduction, l’etude der algues fossiles paleozoiques (de la bacterie a la tectonique des plaques. Bull. Centres Rech. Explor. - Prod. Elf. Aquitaine, 9 (2), 465-499. Schaub, H., 1951. Stratigraphie and paläontologie des Schlierenflysches mit besonderer Berücksichtigung der Paleocaenen und untereo Caenen Nummuliten und Assilinen. Schweiz. Paläont. Abh., 68, 11-217. Sheleby, A.I., Said, M.M., Eid, M.A., 2000. Paleogene Lithostratigraphy of the area west of the Nile Valley between Qena and south Assiut. Annal. Geol. Surv., Cairo, Egypt, XXIII, 563-578. Strougo, A., Bignot, G., Abdallah, A.M., 1992. Biostratigraphy and paleoenvironments of Middle Eocene benthic foraminiferal assemblages of northcentral Eastern Desert, Egypt. M. E. R. C. Ain Shams Univ., Cairo, Egypt, Earth Sci. Ser., 6, 1-12. Trappe, J., 1992. Microfacies zonation and spatial evolution of a carbonate ramp: marginal Moroccan phosphate sea during the Paleogene. Geologische Rundschau, 81 (1), 105-126. Wilson, J.L., 1975. Carbonate facies in geologic history. Springer-Verlag, Berlin, Heidelberg, New York, 471 p. Wray, J.L., 1977. Calcareous algae. Elsevier Scientific Publishing Co., Amsterdam, Oxford, New York, 185 p. Youssef, M.M., Mansour, H.H., Philobbos, E.R., Osman, Z.L., 1982. Contribution to the geology of the area northwest of Assiut, Egypt. Bull. Fac. Sci. Assiut Uni., Egypt, 11(1), 335-354.
VII- 33 Biostratigraphic Zonation And Eocene Chlorophytal Algae, …….
CAPTION OF FIGURES
Fig. (1) Geological map of the study area (modified after Conoco, 1987). Fig. (2) Biostratigraphic correlation of the fauni and flori zones. Fig. (3) Legend for the carbonate constituents of the studied sections. Fig. (4) Distribution chart of algae and foraminifera at El-Zarabi section. Fig. (5) Distribution chart of algae and foraminifera at Ismail Bey section. Fig. (6) Distribution chart of algae and foraminifera at Gebel Gibeil section. Fig. (7) Distribution chart of algae and foraminifera at Mallawi section. Fig. (8) A-E. Belzungia silvestrii; A & B. transversal sections, C. oblique transversal section, D. longitudinal section, E. tangential section. F-H. Dissocladella sp.; F. (ov) oblique vertical section, (t) Tangential section, G. transversal section, H. oblique longitudinal section. I & J. Cymopolia elongata; cross sections. K. Cymopolia sp.; transversal section. L & M. Furcoporella diplopora; L. oblique transversal section, M. oblique longitudinal section. N-Q. Niloporella subglobosa; N. cross section, O. axial section, P. group of different sections, Q. oblique tangential section. Fig. (9) A. Neomeris sp.; bioclasts. B. Clypeina cf. rotella Yu-Jing; cross section. C. Acicularia robusta Dragastan & Soliman; oblique section of gametophore with fertile ampoules. D-F. Ovulites pyriformis Schwager; cross sections. G & H. Ovulites arabica (Pfender); oblique sections. I & J. Ovulites morelleti Elliott; I. longitudinal section, J. horizontal section. K. Ovulites marginulata Lamarck; cross to tangential section. L-N. Ovulites elongata Lamarck; L & M. group of different sections (N.B. the effect of calcitization in L and micritization in M), N. oblique vertical section. O-Q. Halimeda nana Pia; O. vertical section, P & Q. oblique horizontal sections. R & S. Halimeda praemonilis Morellet; longitudinal sections. T. Halimeda sp.; tangential section.
CAPTION OF TABLES
Table 1. Lithostratigraphic classification of the Eocene carbonate succession within the area under consideration. Table 2. The main characteristics of the studied rock units and their depositional environments. Table 3. Biostratigraphic zonation of the Early-Middle Eocene sequence of the study area. Table 4. The identified green algal genera and species and their systematic classification.
Sobhi A. Helal and Ahmed W. Hussein VII- 33
VII- 32 Biostratigraphic Zonation And Eocene Chlorophytal Algae, …….
Sobhi A. Helal and Ahmed W. Hussein VII- 32
VII- 33 Biostratigraphic Zonation And Eocene Chlorophytal Algae, …….
Sobhi A. Helal and Ahmed W. Hussein VII- 33
VII- 38 Biostratigraphic Zonation And Eocene Chlorophytal Algae, …….
Sobhi A. Helal and Ahmed W. Hussein VII- 30
Table 1 SECTION EL-ZARABI ISMAIL BEY GEBEL MALLAW GIBEIL I AGE
MIDDL LUTETIA ------Samalut E N Formation
EOCEN (36.5 m) E
------Minia Formation ------(31.5 m) EARLY LATE -- EOCEN YPRESIA Drunka Uppe Drunka Upper Drunka Upper ------E N Formatio r unit Formatio unit Formatio unit -- n n n EARLY Lowe ------(133.75 (35.5 m) (48.5 m) YPRESIA r unit m) - - -- N ------not recorded Table 2 AGE EL-ZARABI ISMAIL BEY GEBEL MALLAWI GIBEIL SECTION MIDDLE LUTETIAN Nummulites EOCENE ------gizehensis s.l zone
Alveolina ------oblonga / ------Orbitolites EARLY LATE complanatus EOCENE YPRESIAN zone
Ovulites Acicularia elongata robusta/ Nummulites subzone Nummulites Ovulites Nummulites ------planulatus planulatus spp. planulatus zone zone subzone zone
Niloporella Niloporella subglobosa subglobosa subzone subzone EARLY Ovulites arabica/Ovulites ------YPRESIAN pyriformis zone ------not recorded VII- 33 Biostratigraphic Zonation And Eocene Chlorophytal Algae, …….
Table 3
ROCK LITHOLOGY SEDIMENTARY FOSSIL MAJOR TEXTURES DEPOSITIO UNIT STRUCTURES TAXA NAL ABUNDANCE ENVIRONM ENT Burrowing, ripple Green algae, Lime mudstone, marks, wavy and echinoids, wackestone, Drunka Porous algal lenticular bedding Medium nummulites packstone and Restricted Formation limestone with and massive to & miliolids grainstone shelf lagoon chert thick-bedded Minia Aleveolinid and Massive to thick- Alveolines, Wackestone, Alveolina- Formation orbitiolinid bedded and orbitolites packstone and orbitolites- limestone burrowed High & green grainstone green algae algae bank Samalut Nummulitic Unbedded massive Nummulites Wackestone, Formation limestone of mound shape , bryozoa, packstone and Very high discocycline grainstone Nummulitic & red algae bank
Table 4
DIVISION CLASS ORDER FAMILY TRIBE GENERA & SPECIES Thyrsoporellidae Belzungia silvestrii
Dissocldella sp.
Cymopolieae Cymopolia elongata
Cymopolia sp.
Cholorophyceae Dasycladales Dasycladaceae Macroporellineae Furcoporella diplopora
Dasycladeae Niloporella subglobosa
Neomereae Neomeris sp.
Acetabulariaceae Clypeineae Clypeina cf. rotella
Acetaburlarieae Acicularia robusta
Ovulites pyriformis
Ovulites arabica Cholorophyta Udoteaceae ------Ovulites morelleti Ovulites marginulata Bryopsidophyceae Bryopsidales Ovulites elongata Ovulites sp. Halimeda nana Halimedaceae ------Halimeda praemonilis Halimeda sp.
EIGHTH INTERNATIONAL CONFERENCE ON THE GEOLOGY OF AFRICA P-P VII-55 - VII -75 (NOV. 2015) ASSIUT-EGYPT
LITHO-STRATIGRAPHY AND PETROLEUM SOURCE ROCK POTENTIAL OF THE SOUTHERN BIDA BASIN, NIGERIA
Usman, H.O.1, Obaje, N.G.2 and Nghargbu, K.1 1Department of Geology and Mining, Nasarawa State University, Keffi, Nasarawa State, Nigeria 2Department of Geology and Mining, Ibrahim Badamasi Babangida University, Lapai, Niger State 1Department of Geology and Mining, Nasarawa State University, Keffi, Nasarawa State, Nigeria Emails: [email protected], [email protected], [email protected]
ABSTRACT
The study area is the Southern Bida Basin (Lokoja Sub-basin), extending from Gada-Biyu in the Federal Capital Territory to the Agbaja Plateau in Kogi State of Nigeria. This area is geologically underlain by three rock units namely: the Lokoja, Patti and Agbaja Formations. The Lokoja formation composes of fine to medium coarse grained sandstone, poorly sorted associated with sedimentary structural features ranging from parallel lamination to cross bedding (herring bone structures) indicating continental environment of deposition with marine tidal influxes. Suspension settling in a low energy setting was attributed to the deposition of the Patti Formation with a lithologic composition of shales and siltstones which are rhythmically interbedded with concretional to massive bioturbated ironstones. The Agbaja Formation composes of oolitic ironstones beds. The micropaleontological studies of the rocks in this area show that the foraminiferal assemblages in Patti Formation are lowly diversified and dominated by four (4) genera, namely: Ammbaculites, Milliammina, Trochamina and Textularia. This agglutinated benthonic foraminiferal assemblage indicates deposition of the Patti Formation in an anoxic shallow marine environment. Keywords: Sandstone, foraminifera, biotubation, cross-bedding, oolitic, shales, siltstones, biostratigraphy.
INTRODUCTION
The Bida Basin (Lokoja Sub-basin) is one of the inland sedimentary basins in Nigeria located in the North-Central geographical region (Fig.1). Inland sedimentary basins in Nigeria comprise the Anambra , Dahomey in the South, the lower, middle and upper Benue Trough, the Chad (Bornu) in the Northeast, and the Bida Basin and the Sokoto basins in the Northwest. Explorations of these inland basins have not been commercially successful to date, principally because their lithostratigraphical configurations have not been well documented. For this reason, many investors have turned their focus away from the onshore to frontier deep- water and ultra deep water offshore. This work focuses on the general geology of the southern Bida Basin with special emphasis on the litho-bio-stratigraphy and petroleum source rock potential. It also involves a review of previous literature available in the area, and laboratory studies, VII- 56 Litho-Stratigraphy And Petroleum Source Rock Potential ………. which were carried out after the geological mapping. This paper therefore discusses the litho-and bio-stratigraphy of the Lokoja, Patti and Agbaja Formations in the southern Bida Basin. The result from the laboratory analysis on the foraminiferal studies, and the lithologic description enabled an evaluation of the petroleum source rock potentials in the basin.
Fig. 1: Geologic Sketch Map of Nigeria showing the sedimentary basins with locations of the Bida basin and other Inland basins (After Obaje, 2009)
PREVIOUS WORK
The preliminary geological studies of the Bida Basin were by Falconer (1911) and Jones (1955, 1958). However, the first major works that focused mainly on stratigraphy and sedimentology were those of Adeleye (1971, 1973, 1974). Jan du Chene et al. (1978) reported the occurrence of few palynomorphs in the southern Bida Basin. Kogbe et al. (1981, 1983) and Ojo (1984) have advanced geophysical evidence supporting a rift model for the origin of the Bida Basin. Braide (1992a), Olaniyan and Olobaniyi (1996) and Olugbemiro and Nwajide (1997), described some aspects of sedimentological characteristics of the Lokoja Formation and Bida Sandstone which they interpreted to be a predominantly continental deposit. Ladipo et al. (1994) and Abimbola et al. (1994) described and interpreted the origin of the Agbaja ironstone on the basis of their lithologic characteristics, petrography and mineralogy. Only few investigations have been on the hydrocarbon potential of the basin (Idowu and Enu, 1992; Akande and Ojo, 2002). Vrbka et al. (1999) reported the hydraulic characteristics of the Cretaceous sandstone facies in the south-eastern Bida Basin.
LOCATION AND ACCESSIBILITY
The mapped areas were basically around Abaji, Ahoko, Felele, Lokoja and Agbaja Plateau which are well located in Kogi State. Outcrop sections of the Lokoja Usman, H.O., Obaje, N.G. and Nghargbu, K. VII- 75
Formation were logged and interpreted. Samples were collected for biostratigraphical studies from Patti Formation around the Ahoko area along the Lokoja-Abuja express way located on coordinates N08o18’18” and E06o51’30”. The area is generally accessible by tarred road except for Agbaja Plateau.
Fig. 2: Geologic map of the Southern Bida Basin (after Agyingi, 1991)
GEOLOGICAL FRAMEWORK AND STRATIGRAPHY
The Bida Basin is a NW-SE trending depression perpendicular to the main axis of the Benue Trough. Several authors have expressed different views on the genesis of the Bida Basin. King (1950) and Kennedy (1965) described the basin as a rift- bounded tensional structure produced by faulting associated with the Benue Trough system the drifting apart of the African and Brazilian plates. They noted the possibility that the bounding rift faults of this asymmetrical rift structure may have been obliterated by subsequent erosion. The existence of the faults along the margins has not been conclusively proven from gravity studies across the Basin. However, an interpretation of Landsat imagery as well as other geophysical data across the Bida Basin suggests that the basin is bounded by a system of linear NW- SE faults (Kogbe et al. 1981) which support a rift model. Gravity data (Ojo and Ajakaiye, 1989) also confirmed a central positive anomaly flanked by negative anomalies typical of rift structures. Whiteman (1982) suggested that the basin was formed from simple cratonic sag whilst Braide (1992a) advanced a wrench fault tectonic model for the basin. This model may be supported also by the idea that the entire Benue Trough which comprises of series of basins and sub-basins each of which has been defined as constituting the tectonic framework of Nigerian sedimentary basins compiled from aeromagnetic and other data. Modeling of geophysical data (Adeniyi 1985; 1986) VII- 58 Litho-Stratigraphy And Petroleum Source Rock Potential ………. suggest that up to 3.5km of sediments may have accumulated in the deepest part of the Bida Basin. The basin is divided into northern and southern Bida Basin, geographically from the north to the south.
STRATIGRAPHY OF THE BIDA BASIN
The stratigraphy and sedimentation of Upper Creataceous (Campanian – Maastrichtian) succession of the Bida Basin have been documented by Adeleye (1971) as well as Adeleye and Dessauvagie (1972). In the central parts of the basin around Bida, four mappable stratigraphic units are recognizable in this area comprising the Bida (including the Doko and Jima Members),Sakpe, Enagi and Batati formations that were correlated with the stratigraphic units in the southern Bida i.e the Lokoja sub- basin around Lokoja (Fig.3).
Fig. 3: SE-NW Stratigraphic relationships from the Anambra Basin to the Bida Basin. The Upper Cretaceous formations and their laterial equivalents in the Bida and Lokoja areas thicken in the Anambra Basin overlying the older Pre-Santonian sediments (after Obaje, 2010)
STRATIGRAPHY OF THE SOUTHERN BIDA BASIN
The formational units in the southern Bida Basin comprise the Lokoja, the Patti and the Agbaja formations, which are lateral equivalents of the Bida Sandstone Group, Sakpe Ironstone, Enagi Siltstone and Batati Ironstone, respectively. Figure 3 shows the revised correlation of the stratigraphic succession across the northern and central sub-basin into the Lokoja area to the south. These are largely based on the observed lithologic and depositional characteristic and have been extended into the Anambra Basin to the south. These lateral equivalents represent continuous depositional phases from the south to the north and north-west, controlled by major sea level rise and falls in the uppermost cretaceous. The age of the stratigraphic succession in the Usman, H.O., Obaje, N.G. and Nghargbu, K. VII- 75 basins is thought to be middle to upper Maastrichtian, and on the lateral equivalence and depositional continuity from north to north –west.
GEOLOGY OF THE STUDY AREA
Lokoja Formation The basal unit overlying the Basement Complex unconformably is the Lokoja Formation and it is the lateral equivalent of the Bida formation (Fig. 3). It consists of sub-angular to sub-rounded quarts pebbles in a clay matrix. Lithologic units in this formation range from conglomerates, fine to very coarse-grained facies vary in colour from milky to purple and massive to cross-stratified. They are generally poorly sorted and composed mainly of quartz and feldspar thus texturally and mineralogical immature (Ojo, 1992). This formation is not fossiliferous exposed between Lokoja and Koton Karfe and has been interpreted as continental (alluvial fan) deposit (Adeleye, 1989, Braide, 1992a). Patti Formation The deposition of Patti Formation is attributed to the beginning of the marine transgression in the early to middle Maastrichtian. This deposition took place presumably by suspension settling in a quiet low energy setting probably in a restricted body of water (Braide, 1992; Maill, 1990). The Patti Formation is generally made up of black carbonaceous fissile shale with interbed of claystone, siltstone, concretional ironstone, other outcrop sections have also been described. This formation is very fossiliferous, containing mainly foraminifera. These foraminifera assemblage include; Ammobaculites, Milliamina, Trochamina and Textularia (Jan du Chene, 1978; Asepo, 2001). Agbaja Formation This is the youngest oolitic ironstone unit in the southern Bida Basin overlying the Patti Formation. The Agbaja formation forms the protective lateritic capping for the Campanian-Maastrichtian desposits. It is well exposed at Agbaja where sub-facies, i.e. oolitic, concretional and massive ironstones have been described (Abimbola et al., 1994), with a thickness of 20m. It forms the lateral equivalence of the Batati formation of the central Bida Basin. Ladipo et al. (1994) reported the environment of deposition of the ironstones appeared to have been influence by marine wave actions which reworked kaolinitic mud into concentric oolites often with nuclei of Pyrite or siderite that have now become replaced by iron oxides. This formation is not fossiliferous.
MATERIALS AND METHOD
In the field, sampling of geological units was carried out where there are exposures of surface outcrops. Sections were measured using measuring tape and samples were collected at different locations, road cuts and within some mining sites. At each location, samples were numbered serially with locality number and their lithologic description was noted in the field notebook. Each sample was properly labeled and placed in polythene/sample bags. Sample from Patti Formation were collected and washed for foraminiferal study. The rock sample was crushed to an optimum size, using pistol and mortar. 40g of each ground sample was placed in a dish and wash with water to remove the dust and later treated with hydrogen peroxide/kerosene and left for 48 hours. The hygrogen peroxide/disaggregate and dissolve the rock material and frees the fossils. After 48 hour, the sample was made loss using the hand, the resulting sample was sieved using 220um, and 65um, sieve meshes with a bottom pan all arranged VII- 60 Litho-Stratigraphy And Petroleum Source Rock Potential ………. together. Samples were collected in each of sieve including the bottom pan, after which they were taken for microscopic studies to identify the type of foraminifera present.
RESULTS
Lokoja Formation The outcropped Lokoja Formation consists entirely of conglomerates, pebbly sandstone and claystone beds which shows variable sedimentary structure and textures that graded upward form parallel lamination to planar and cross bedding (herring bone), with variations in their grain size which also ranges from fine to medium and medium to coarse grained sandstone at the bottom and top respectively. In section 1, Felele, near Lokoja, the lithofacies description consists of a fining upward thick sequence of conglomerates, sandstones and claystones. The basal unit consists of conglomeratic sub-facies (A1) about 0.3m thick, and it is largely grain supported (Figs.4 and 5). The clasts comprise mainly of angular to subrounded quartz pebbles, few types of feldspar and rock fragments indicating the low maturity of the sediment. A pebbly ferruginised and weakly stratified sandstones unit (about 0.7. thick) separates the basal grain-supported conglomerate from the overlying predominantly matrix supported conglomerate sub-facies (A2). Here, the angular to subrounded clasts are larger, and float within a poorly sorted sand matrix this unit grades finely into milky, weakly stratified pebbly sandstone and massive medium t coarse-grained sandstone at the middle part of the section (Fig.5). Towards the upper part of the section, another Conglomerate sub-facies (A3), about 3m thick occurs. Graded bedding defined by segregated bands of clast is characteristic of this sub-facies (Fig.5). The clasts of varying sizes (pebble to cobble) are angular to subrounded and matrix-supported, float within the sandstone. This passes transitionally into a sandy claystone.
Fig. 4: Basal conglomerate facies of the Lokoja at Felele (note the grain supported fabric) Usman, H.O., Obaje, N.G. and Nghargbu, K. VII- 16
Fig. 5: Lithologic section and interpretation of the Lokoja Formation exposed at Felele
In section 3, 2.5km north of Lokoja New Market, the lithologic description of section in this area is lithologically similar to preceding sections and is about 24m thick. The basal part consists of conglomeratic sandstone which is differentiated into three subunits on the bases of texture and sedimentary structures. At the base is the massive, poorly sorted conglomeratic sandstone (about 1m thick). The cobbles to pebble size, angular to subrounded clasts show no preferred orientation and floats within a quartz and feldspar-rich purplish matrix. This passes gradually into a conglomeratic sandstone unit (about 2m thick) in which the pebbles and cobbles are separated into bands that are parallel to the bedding plane. The third conglomeratic sandstone unit is cross-stratified, displaying herringbone cross bedding (Fig.6) this is overlain sharply by alternating brownish to purple coarse-grained sandstone and creamy to white fine grained sandstone at the middle part of the section (Fig. 7). VII- 62 Litho-Stratigraphy And Petroleum Source Rock Potential ……….
Fig.6: Herringbone cross bedding in conglomeratic sandstone of the Lokoja Formation exposed at 2.5km north of Lokoja new market
Fig. 7: Lithologic section and interpretation of the Lokoja Formation exposed at 2.5km north of Lokoja new market along the Lokoja- Abuja highway Usman, H.O., Obaje, N.G. and Nghargbu, K. VII- 16
In section 4, 1.8km north of Lokoja New Market, a section of about 13 m thick was seen (Fig. 8). It protrudes from the base of about 4m thick conglomeratic sandstones which are strongly bioturbated, containing abundant Ophiomorpha and Thalassonoides burrows towards the northern edge of the outcrop. This unit also contains weakly preserved cross-stratification. Towards the middle part of the section is a conglomerate sub-facies which overlies coarse-grained sandstone. Four segregated bands of pebble to cobble materials are recognized in this unit. This unit gets finer upwards, into coarse to medium-grained sandstone and claystone.
Fig. 8: Lithologic section and interpretation of the Lokoja Formation exposed at 1.8 north of Lokoja new market. Patti Formation Section 1 (Fig. 9) at Ahoko, the argillaceous units of the Patti Formation are well exposed. About 26m thick section consists predominantly of shales and siltstones which are rhythmically interbedded with concretional to massive, bioturbated ironstones (Fig. 9). At the basal part of the section, a shale bed with an average thickness of 0.05m is prominent. It is essentially dark to light grey, carbonaceous and fissile. At the depth interval 4-10m, the dark grey shales are vertically fractured with the fractures filled with strongly ferruginised siltstone. It is observed that the ironstone interbeds are not fractured; probably the fracturing preceded the formation VII- 64 Litho-Stratigraphy And Petroleum Source Rock Potential ………. of the ironstone beds. The silty shale unit within depth interval 6-8m contains abundant woody fragments and plant remains. The ironstones have an average thickness of 0.20m and are predominantly concretional, though some few beds are massive and contain vertical and horizontal burrows.
Fig.9: Lithologic section and interpretation of Patti Formation exposed at Ahoko Usman, H.O., Obaje, N.G. and Nghargbu, K. VII- 17
Fig.10: Parallel bedding of the Patti Formation which characterizes the unit.
Fig.11: Bioturbated ferruginated siltstone bed of the Patti Formation at Ahoko In section 2 (Fig.14) at Abaji, this section consists predominantly of sandstone facies of the Patti Formation. The sandstone varies from conglomeratic sandstone, massive to cross-bedded, fine to coarse-grained sandstones. The basal part of the section consists of massive, poorly sorted sandstone and massive sandy claystone with an average thickness of 1m. These are overlain by thick pebbly to very coarse, cross-stratified sandstone (about 4m thick) and they grade finely through medium to coarse-grained sandstone into small-scale cross-bedded ferruginated sandstone. At the middle part of the section, the small-scale cross-bedded sandstone is sharply overlain by thick, massive conglomeratic about 0.5m thick which passes sharply into a cross-bedded and ripple –laminated sandstone. The upper part of the section consists of siltstone, fine-grained wavy laminated massive sandstone and claystone (Fig.13). Generally the sandstone facies displaying parallel bedding in this location (Fig.14) are more mineralogical mature compared to the sandstone facies of the Lokoja Formation. VII- 66 Litho-Stratigraphy And Petroleum Source Rock Potential ……….
Fig.12: Sandstone facies of the Patti Formation exposed at Abaji.
Fig.13: Wavy ripples laminated features of the Patti Formation at the top part of the section exposed at Abaji Usman, H.O., Obaje, N.G. and Nghargbu, K. VII- 15
Fig. 14: Lithologic section and interpretation of the Patti Foramtion exposed at Abaji
Agbaja Formation Based on the field observations on the outcropped section of the Agbaja Formation at the Agbaja Plateau, three different rock types lithofacies (Fig.18) which are the poorly sorted sandstone lithofacies of the Lokoja Formation, the fine-grained sandstone lithofacies of the Patti Formation and oolitic ironstone beds of the Agbaja Formation are overlain in this sequence towards the upper part of the section. It was also observed that the influence of marine reworked the kaolinitic mud into oolites forming the ironstone of the Agbaja Formation. VII- 68 Litho-Stratigraphy And Petroleum Source Rock Potential ……….
Fig. 15: Well sorted friable sandstone unit displaying internal stratification such as herringbone cross bedding
Fig. 16: Massive, silty, kaolinitic claystone bed and in some places sandy exposed on the Agbaja Plateau
Fig. 17: Concretional ironstone overlying oolitic ironstone on the Agbaja Plateau. Usman, H.O., Obaje, N.G. and Nghargbu, K. VII- 15
Fig. 18: Lithologic section and sedimnetological interpretation of the Lokoja and Agbaja formations exposed on the Agbaja Plateau
DISCUSSION
LITHOSTRATOGRAPHY
Lokoja Formation Based on field observations on colour and texture, the Lokoja Formation in section (Figs.4 and 5) could be assigned to the rock type sandstone, The lower member is a clast supported conglomerate with angular to subrounded clasts which are poorly sorted deposited under continental environment .The upper member is a matrix supported conglomerate with segregated bands of clasts and a sandy claystone, massive and ferruginised, deposited under continental environment dominated by mass flow turbidity current and bed load deposits within an alluvial fan and braided stream. The prevalent alternation of this formation occurred during the Campanian/Maastrichtian regressive processes which took place in the Bida Basin. As the sea retreated back from the land (i.e. regression), it brought along with its VII- 70 Litho-Stratigraphy And Petroleum Source Rock Potential ………. sand particles and silt from the continent and as this load become heavy for the water to carry, it was deposited, forming the sandstone of the Lokoja Formation. However, in Figs.5,7 and 8 as notably observed, the Lokoja Formation is distinguished based on their sedimentary structural features, colour, and texture. The lower member consists of matrix supported conglomerate with segregate bands of clasts. Upward through the section, there is variation in the colour of the sandstone from milky-whitish to purple-reddish, massive, poorly sorted medium to coarse grained sandstone (Fig.5). These portions are deposited under fluvial condition during the Campanian/ Maastrichtian regressive period, when the water movement from the land to the sea has reduced drastically and with a change in the direction of flows, resulted to different stratified current bedding sedimentary structural features (herring bone, cross and massive bed) that ranges from planar to trough cross bedding on these sandstone units. The presence of ferrugination process on these rocks was due to the oxidation that prevailed as a result of exposure.
Patti Formation The outcropped section 1 (Fig.9) of this formation can be distinguished mainly into two members, based on their colour intensity, texture, and thickness of the shale beds and the ironstone, the lower member consist of a highly laminated dark grey shale beds with intercalation of thin ferruginised layers, shale contain foraminifera. The thickness of the shale and the ferruginised layer is variable. Towards the upper part of the section, it is made up of carbonaceous shales (with woody fragments) interbedded with concretional ironstone. Further upward, the ironstone is bioturbated and the shale are fractured and colour changes to light grey silty shales. Also, in section 2 (Fig.14) three distinct lithologic members could be assigned to the three different lithofacies based on field studies and observations on colours, texture and identified rock types, these are: the sandstone, siltstone and claystone lithofacies. The basal part of the section consists of massive, poorly sorted sandstone and, massive sandy claystone. At the middle part of the section the small- scale cross-bedded sandstone grades transitionally into ripple-laminated fine- grained sandstone. The upper part of the section consists of siltstones, fine-grained wavy laminated massive sandstones and claystones. Generally, considering the lithologic composition, it shows that there was a rapid change in the depositional environments of this formation. This also indicates that the Patti Formation was deposited under different marine environments during the middle to late Maastrichtian and is generally fossiliferous. Samples from the Patti Formation at Ahoko shows that it is made up predominantly of benthic foraminifera composed of agglutinated (arenaceous) taxa (Fig. 19) in the shales at the lower part of the section with no calcareous form. This foraminifera assemblage include: Ammobaculites, Milliamina, Trochamina, Textularia, and Haplophragmoides. Among which Ammobaculites seem to be the most abundant followed by other agglutinated taxa. The presence of this agglutinated foraminiferal forms recovered from the shale are indicative of marshy, marginal marine setting.
Usman, H.O., Obaje, N.G. and Nghargbu, K. VII- 56
2
1. Ammobaculites sp. 2. Textularia sp.
3
3. Trochamina sp.
4
4. Haplophragmoides sp. Fig. 19: Agglutinated Benthic Foraminifera
VII- 72 Litho-Stratigraphy And Petroleum Source Rock Potential ……….
Agbaja Formation Based on the field observations on the outcropped section of the Agbaja Formation at the Agbaja Plateau, three different rock types (Fig. 18) which are the poorly sorted sandstone lithofacies of the Lokoja Formation, the fine-grained sandstone lithofacies of the Patti Formation and oolitic ironstone beds of the Agbaja Formation overlie this sequence towards the upper part of the section. The oolite is associated with laterite which is up to 13m thick in places. Most of the ironstone consists of goethite, but locally unweathered horizons near Lokoja are rich in chlorite and siderite, suggesting origin under reducing conditions. The oolites are probably of lateritic origin in view of their massive nature the restriction of their occurrence to high- lying plateaus. However, they contain siderite and magnetite which may suggest sedimentary origin.
Table 1: Foraminiferal population per 40g of washed samples of section of Patti Formation, at Ahoko, along the Lokoja- Abuja highway.
SPECIES SAMPLE NUMBER 1 2 3 4 Milliamina sp. 15 2 3 5 Ammobaculites sp. 24 7 9 12 Trochamina sp. 7 1 2 Textularia sp. 1 1 3
Haplophragmoides 1 1 2
Total number of 49 12 17 19 individuals (abundance)
Table 2: Diversity and abundance of foraminiferal population of table above Number of genera Number of individuals Sample number (simple diversity) (abundance) 1 5 49 2 5 12 3 4 17 4 3 19
PETROLEUM POTENTIAL A proper evaluation of the petroleum potential of the southern Bida Basin will need to access the source rock maturity, migration pathways reservoir, seals, and possible trap configuration. Although no specific studies have addressed all of these characteristics and information on each of them is generally scanty. This section will evaluate the source rock facies, potential reservoir and traps, based on the descriptive and interpretative information of available data.
Source Rock Potential Source rock facies in the field areas consist of dark carbonaceous and grey shale facies of the Patti Formation exposed at Abaji and Ahoko. The shale facies, commonly interbedded with parallel stratified siltstones and claystones, have been interpreted as deposit within a marginal marine swamp environment.
Usman, H.O., Obaje, N.G. and Nghargbu, K. VII- 56
Reservoir Rocks Tectonic elements developed from basement fragmentation, block faulting, and subsidence and rifting have direct impact on the structures confining the reservoir rocks and traps. The fluvial Lokoja Sandstone with the prevalence of alluvial fans, which contain poorly sorted, matrix supported conglomeratic sandstone (proximal to basement margins) represent the major sub facies with reservoir potential, these proximal fans seen mostly around Lokoja. Although sub facies is quartz rich, the conglomeratic sandstone is contains abundant clay matrix. Their continental nature and humid climatic influences have led to a complete diagenetic alteration of the feldspars to kaolinte in many instances. The obvious clogging of the pore throats by clays and pore filling clayey minerals have reduced the porosity and permeability of the Lokoja Sandstone. However, the relatively well sorted sandstone unit especially tidal bars in the Patti Formation observed in the Abaji and Agbaja areas have better reservoir characteristics. This tidally influenced facies (confirmed from observed herring bone cross stratifications) are deposited within the marginal marine environments. This can form potential reservoirs rocks if preserved in deeper sections especially where the mudstone and claystone interbeds become thick enough to form effective top and bottom seals. Indeed, sands interbeds with silty clays in the basal parts of the Patti Formation are good aquifers for portable water presently noteworthy that both the Lokoja and Patti sandstone facies are variably ferruginised, compacted and lithified with concretionary structures in the flood plain environments. The diagenetic process resulting in the concretionary ironstones and variably ferruginised structures may have reduced the porosity and permeability of the sandstone and siltstone facies even in places where there are obvious seals of clays and shale.
Traps Traps in the basin could be in the form of drapes of sands overlying uplifted blocks of basement, faulted basement in-filled by proximal alluvial fans and especially, the tidally influenced sand bodies. Braide (1992) summarized the possibility of four different trap configurations, which include: 1. Traps within uplifted basements, 2. Traps in drapes or compaction structures over deep horsts, 3. Traps in structures developed along major faults and lineaments, 4. Stratigraphic traps along flanks or periphery of uplifted basement blocks.
CONCLUSION
The lithostratigraphic units identified in the area were the Campanian/Maastrichtian Lokoja Formation deposited under continental environment, as indicated by the presence of coarse, medium to fine grain, poorly sorted sandstone units. The Maastrichtian Patti Formation was deposited under shallow marine environments and the Campanian/Maastrichtian Agbaja Formation was deposited under continental environment. to Late Maastrichtian sequence of the Patti Formation is characterised by low diversity and high abundance of predominantly agglutinated taxa that are known to tolerate anoxic condition. This indicates deposition in an anoxic shallow marine environment. The deeper parts of the basin may constitute appreciable volumes of mature source rocks (shale), therefore, it may have started generating gas at the deeply buried sections. The poorly sorted sandstone of the Lokoja Formation can form potential reservoir rocks if preserved in deeper sections, VII- 74 Litho-Stratigraphy And Petroleum Source Rock Potential ………. especially where mudstone and claystone form effective top and bottom seals. Potential stratigraphic and structural traps also occur as alluvial fans, fractured uplifted basement blocks and strata arched over uplifted basement blocks.
REFERENCES
Adeleye, D.R. (1971): Stratigraphy and Sedimentation of the Upper Cretaceous Strata around Bida, Nigeria. Ph.D. Thesis, University of Ibadan (Unpublished). Adeleye, D.R. and Dessauvagie, T.F.J. (1972): Stratigraphy of the Mid-Niger Embayment near Bida, Nigeria. In: Dessauvagie, T.J.F. and Whiteman, A.J (Eds), Proceedings of the Conference on African Geology, Ibadan University Press, Ibadan, pp. 181 – 186. Adeleye, D.R. (1973): Origin of Ironstone: An Example from the Middle Niger Valley, Nigeria. Journal of Sedimentary Petrology, vol. 43, pp. 709 – 727 Adeleye, D.R. (1974): Sedimentology of the Fluvial Bida Sandstones (Cretaceous), Nigeria. Sedimentary Geology, vol.12, pp. 1 – 24. Adeniyi, J.O. (1985): Ground Total Magnetic Intensity in Parts of the Nupe Basin and the Adjacent Basement Complex, Niger State, Nigeria. Nigerian Journal of Applied Science, vol.3, pp. 67 – 78 Adeniyi, J.O. (1986): Polynomial Regional Surfaces and Two Dimensional Models in Parts of the Nupe Basin and the Adjacent Basement Complex, Niger State, Nigeria. Nigerian Journal of Applied Science, vol. 4, pp. 25 – 34 Akande, S.O., Ogunmoyero, I.B., Peterson, H.I. and Nytoft, H.P. (2007): “Source rock evaluation of coals from Mamu Formation, South Eastern Nigeria”. Journal of Petroleum Geology, V.30, pp. 303-342. Benton, M. and Harper, D. (1997): Basin Paleontology. Addison Wesley Longman, Harlow, Essex 1997, 342 pp. Braide, S.P. (1992a): Geologic Development, Origin and Energy Mineral Resource Potential of the Lokoja Formation in the Southern Bida Basin. Journal of Mining and Geology vol. 28, pp. 33 – 44. Braide, S.P. (1992b): Syntectonic Fluvial Sedimentation in the Central Bida Basin. Journal of Mining and Geology, vol. 28, pp. 55 – 64. Douglas, D.J. (1962): The Structure of Sedimentary Deposits of Braided Rivers. Sedimentology, vol. 1, pp. 167 – 190. Falconer, J.D. (1911): The Geology and Geography of Northern Nigeria. MacMillan, London. 295 pp. Jan du Chene, Adegoke, O.S. and Adeniran, S.A. (1978): Palynology and Foraminifera of the Lokoja Sandstone (Maastrichtian), Bida Basin, Nigeria. Revista Espanola De Micro-paleont,vol. X, pp. 379 – 393. Jones H.A. (1955): The Occurrence of Oolitic Ironstones in Nigeria: Their, Geological History and Petrology. D. Phil. Thesis Oxford. 244 pp. Jones, H.A. (1958): The Oolitic Ironstones of Agbaja Plateau, Kabba Province. Records of Geological Survey, Nigeria. pp. 20 – 43. Kennedy, W.Q. (1965): The Influence of Basement Structure on the Evolution of the Coastal (Mesozoic and Tertiary) Basins, in Salt Basin around Africa. Proceedings of the Institute of Petroleum Geologists Society, London, Amsterdam: Elservier, pp. 35 – 47. King, L.C. (1950): Outline and Distribution of Gondwanaland. Geological Magazine, vol. 87, pp. 353 – 359. Kogbe, C.A. (1981): Geological Interpretation of Landsat Imagery of Part of Central Nigeria. Journal of Mining and Geology, vol. 18, pp. 66 – 69. Kogbe, C.A. (1981): Cretaceous and Tertiary of the Iullemmeden Basin of Nigeria (West Africa). Cretaceous Research, vol. 2, pp.129 – 186. Usman, H.O., Obaje, N.G. and Nghargbu, K. VII- 57
Kogbe, C.A. Ajakaiye, D.E. and Matheis, G. (1983): Confirmation of Rift Structure along the Middle Niger Valley, Nigeria. Journal of African Earth Science, vol. 1, pp. 127 – 131. Ladipo, K.O., Akande S.O. and Mucke, A. (1994): Genesis of Ironstones from the Mid-Niger Sedimentary Basin: Evidence from Sedmentological, Ore Microscopic and Geochemical Studies. Journal of Mining and Geology Vol. 30, 161 – 168. Nwajide, C.S. (2013): Geology of Nigeria’s Sedimentary Basins. CSS Press Bookshop Ltd. First Published. pp.183 – 204. Obaje, N. G. (2009): Cretaceous-Cenozoic Magmatism and Volcanism. Journal of Earth Sciences, Pp.49-53. Obaje, N.G. (2010): Geology and Mineral Resources of Nigeria. Elsevier, Heidelberg. 221 pp. Obaje, N.G., Musa, M.K., Odoma, A.N. and Hamza, H. (2011): The Bida Basin in North – Central Nigerian: Sedimentology and Petroleum Geology. Journal of Petroleum and Gas Exploration, Vol. 1(1), pp. 1 – 13. Ojo, S.B (1978): Middle Niger Basin Revisited: Magnetic Constraints on Gravity Interpretations. Abstract, 20th Conference of the Nigeria Mining and Geosciences Society, Nsukka, pp. 52 – 53. Ojo, S.B. and Ajakaiye, D.E. (1989): Preliminary Interpretation of Gravity Measurements in the Mid-Niger Basin area, Nigeria. In: Kogbe, C.A. (Ed.), Geology of Nigeria 2nd edition, Elizabethan Publishers, Lagos, pp. 347 – 358. Olaniyan, O. and Olobaniyi, S.B. (1996): Facies Analysis of the Bida Sandstone Formation around Kajita, Nupe Basin, Nigeria. Journal of African Earth Science, vol. 2, pp. 23 – 256. Olugbemiro, R.O. and Nwajide, C.S. (1997): Grain Size Distribution and Particles Morphogenesis as Signatures of Depositional Environments of Cretaceous (non-ferrugenous). Facies in the Bida Basin, Nigeria.Journal of Mining and Geology, Vol. 33. pp. 89 – 101. Petters, S.W. (1986): Foraminiferal Biofacies in the Nigerian Rift and Continental Margin Deltas. A.A. Balkena, Ritterdam, pp. 219-235. Petters, S.W. (1995): Southeastern Benue Trough and Ikom-Mamfe Embayment. Elizabethan Publishers, Lagos, pp. 17–45. Ratccliffe, N.M. and Burton, W.C. (1985): Fault Reactivation Models for Origin of the Newark Basin and Studies Related to Eastern U.S. Seismicity. Proceedings of the Second U.S. Geological Survey Workshop on the Early Mesozoic Basins of the Eastern united States. U.S. Geological Survey Circular 946, pp. 36 – 45. Russ, W. (1957): The Geology of Parts of Niger, Zaria and Sokoto Provinces. Geology Survey of Nigeria Bulletin, vol. 27, pp. 1 – 24. Steel, R., Siedlecka, A. and Robert, D. (1985): The Red Sandstone Basins of Norway and their Deformation: A Review, In: Gee, D.G. and Sturt, B.A. (Eds). The Calcedonite Orogen – Scandinavian and Related Areas. John Wiley and Sons Ltd., Pp. 293 – 315. Whiteman, A. (1982): Nigeria: Its Petroleum Geology, Resources and Potential. Graham and Trotman, London, 381 pp. Internet Research: @ http://en.wikipedia.org/wiki/ichnofacies.html http://iapetan.wordpress.com/graded_bedding.htm http://www.google.com/cross_bedding.htm EIGHTH INTERNATIONAL CONFERENCE ON THE GEOLOGY OF AFRICA P-P VII-77 - VII-97 (NOV. 2015) ASSIUT-EGYPT
STRATIGRAPHY OF THE PALEOCENE-EOCENE SUCCESSION AT DARB GAGA AREA, BARIS OASIS, WESTERN DESERT, EGYPT
Nageh A. Obaidalla*, Mostafa H. El Dawy**, Kamel H. Mahfouz*** and Samar A. Abdel-Wahed** *Geology Department, Faculty of Science, Assiut University, Assiut, Egypt ** Geology Department, Faculty of Science, Minia University, Minia, Egypt *** Geology Department, Faculty of Science, Al-Azhar University, Assiut Branch, Egypt ABSTRACT High resolution litho- and bio- stratigraphic analyses for the Paleocene-Eocene sequence at Darb Gaga area, Baris Oasis, Western Desert, Egypt have been conducted. Lithologically, the study sequence consists of two rock units, Esna Formation at bottom and Thebes Formation at top. Esna Formation is differentiated into four distinguished members. These are, from bottom to top: El-Hanadi, El- Dababiya Quarry, Darb Gaga and Abu Had. Darb Gaga Member is new and is introduced for the first time here. The thickness of this member is about 11 m and consists of alternative well bedded shale and marl. Darb Gaga Member is chrono- stratigraphically equivalent to El-Mahmiya Member of Aubry et al. (2007). It may represent partly the lateral changes in the sedimentary facies between the siliciclastics of Esna Formation and the carbonate of Garra Formation. The lowermost beds 1 and 2 of El-Dababiya Quarry Member, at the type locality, are absent in Darb Gaga area, where the basal sediments contain glauconite grains. Biostratigraphically, six planktonic foraminiferal zones are identified, one for the latest Paleocene and five zones for the early Eocene. The latest Paleocene zone is Morozovella velascoensis (P5), and the early Eocene zones are Acarinina sibaiyaensis (E1) at base, Pseudohastegerina wilcoxensis/Morozovella velascoensis (E2), Morozovella subbotinae (E3), Morozovella formosa (E4) and Morozovella aragonensis/Morozovella subbotinae (E5) at top. The P/E boundary is characterized by the occurrence of a minor inter-zonal hiatus at the P5/E1 zonal boundary. This hiatus is supported by the occurrence of glauconitic sediments at the base of El- Dababiya Quarry Member and the absence of beds 1and 2.
INTRODUCTION
The Paleocene-Eocene successions are widely distributed in southern Western Desert, Egypt. They are represented by interbeds of siliciclastics and carbonate facies distributed in central and southern parts of Egypt (upper Dakhla, Tarawan, Esna and Thebes formations); which change laterally into predominant carbonate facies (Kurkur, Garra and Dungul formations) at the Southwestern part of the Western Desert. The study area (Darb Gaga area) is located at borders between two facies, at 20 km north of Baris Oasis, Western Desert, at latitude 24° 54' 32" N and longitude 30° 57' 30" E (Fig. 1). Darb Gaga area represents the western face of the Nile Valley of the western Plateau of Baghdad- Luxor road. The Global Stratotype Section and Point (GSSP) of the Paleocene/Eocene (P/E) boundary was defined at Dababiya Village, south Luxor, Egypt (Aubry et al., 2002). Many complete P/E sections have been subsequently defined in Egypt such as El-Qreiya VII- 78 Stratigraphy Of The Paleocene-Eocene Succession At Darb Gaga Area, …….
(Berggren & Ouda, 2003b; Knox et al., 2003), Wadi Tarfa (Obaidalla, 2006) and Gabal Umm El- Ghanayim (Mahfouz, 2008). Several stratigraphic studies on Kharga area have been carried out by different workers (e.g. Nakkady, 1959; Said, 1961 & 1962; Hermina, 1967; Faris, 1974, 1982 & 1993; Tantawy, 1998; Mahfouz, 2008; and El-Azabi and Farouk, 2010). The main aims of the present study are to study the lithostratigraphic units of the Paleocene-Eocene succession and discuss their vertical and lateral changes and detect the nature of the P/E boundary using high resolution planktonic foraminiferal biostratigraphy at Darb Gaga area. To achieve these goals; Darb Gaga section was measured, described, and sampled in detail (Fig. 1), where 99 rock samples are collected, at variable intervals reaching up to 5 cm around the P/E boundary. The rock samples are prepared for foraminiferal analyses. The planktonic foraminiferal species were picked, identified and mounted on micro slides for permanent record. The identified planktonic foraminifera are photographed using the Scanning Electron Microscope (JSM 5400 LD), at Assiut University.
Fig. (1): Geologic map of the study area, modified after Said, 1990. N.A. Obaidalla, M.H. El Dawy, K.H. Mahfouz and S.A. Abdel-Wahed VII- 79
LITHOSTRATIGRAPHY
Generally, The Paleocene/Eocene boundary lies within the Esna Formation in Egypt (Dupuis, et al., 2003; Obaidalla, 2006), except in the south of Egypt at Wadi Abu Ghurra, where it lies within the Garra Formation (Berggren, et al., 2003). At Kharga-Baris district, Western Desert, Esna formation is well defined and wide distributed. Toward the south of Kharga area, the Esna Formation changes laterally from siliciclastics facies to carbonate facies of Garra Formation. At Darb Gaga area, the Paleocene-Eocene successions are differentiated into Esna Formation at base and Thebes Formation at top (Figs 2). In this study, Darb Gaga Member is introduced for first time within Esna Formation to represente lateral facies change between Esna Formation and Garra Formation, and it is equivalent to the Mahmiya Member of Aubry, et al., (2007).
Esna Formation
The Esna Formation was originally introduced by Beadnell (1905) to define the shale between Duwi Formation (Phosphate) at the base and Thebes Formation (Limestone) at the top. Said (1962) emended Beadnell’s nomenclature and subdivision and referred the Esna Formation only to the interval from Tarawan Formation (Chalky limestone) to the Thebes Formation (Limestone). Said (op. cit) erected the Dakhla Formation for the shales underlying Tarawan Formation (Chalky limestone). Aubry et al., (2007) used the definition of Said (1962) at the GSSP, and subdivided the Esna Formation into four members arranged from base to top as follows, El-Hanadi, El- Dababiya Quarry, El-Mahmiya and Abu Had. At Darb Gaga area (this study), the Esna Formation is subdivided into four members: El-Hanadi, El-Dababiya Quarry, Darb Gaga (New) and Abu Had.
El-Hanadi Member
This member was introduced by Abdel Razik (1972), to describe the lower part of the Esna Formation from Tarawan/Esna formational boundary to the top of a phosphatic bed in the lower part of the Esna Shale. According to Aubry et al. (2007), El-Hanadi Member is restricted to the lower part of Esna Formation below El Dababiya Quarry Member. El- Hanadi Member is equivalent to the Esna Unit 1 of Dupuis et al., (2003) (Table 1). At Darb Gaga area, El-Hanadi Member is well recorded, and consists essentially of light gray shale with interaction of limestone in its upper part. In the present study, only the uppermost 6 meters are analyzed.
VII- 80 Stratigraphy Of The Paleocene-Eocene Succession At Darb Gaga Area, …….
Thebes Formation Darb Gaga Member Abu Had Member
Dababiya Quarry Member
A
Dababiya Quarry Member
El-Hanadi Member
B C
Thebes Formation
Abu Had Member Darb Gaga Member D E
Fig. (2): A. General view of Darb Gaga area show the different lithostratigraphic units, B. Field photograph shows El-Hanadi Member at base and Dababiya Quarry Member at top, C. Field photograph shows glauconitic bed at the basal part of Dababiya Quarry Member, D. Field photograph shows Darb Gaga Member, E. Field photograph shows sharp contact between Abu Had Member at base and Thebes Formation at top.
N.A. Obaidalla, M.H. El Dawy, K.H. Mahfouz and S.A. Abdel-Wahed VII- 81
Fig. (3): Lithostratigraphic columnar section of the Paleocene-Eocene succession at Darb Gaga area, Western Desert, Egypt.
El-Dababiya Quarry Member This member was defined by Aubry et al. (2007), to describe about 3.68 m thick of five distinctive beds which characterizes the P/E boundary at the GSSP section at Dababiya Village, about 35 km south of Luxor. Aubry et al. (2007) used high lithostratigraphic untis member instead of Dababiya Quarry Beds of Dupuis et al. (2003) (Table 1). At Kharga
VII- 82 Stratigraphy Of The Paleocene-Eocene Succession At Darb Gaga Area, ……. area, El-Dababiya Quarry Member is recoded at Gabal Umm El- Ghanayim section (Mahfouz, 2008). At Darb Gaga area, El Dababiya Quarry Member is well represented. It is about 3.75 meters thick. Beds no. 1and 2 are absent, but the remainder three top beds are well represented (Figs. 3 & 4). These beds are differentiated from base to top as follow: 1) 105 cm of creamy laminated phosphatic shale. The base of this bed is rich with glauconitic sediments; it contains fish debris and coprolites. The presence of glauconitic sediments and the absence of beds no. 1 (clay bed) and no. 2 (phosphatic shale rich with fish skeleton) indicating the occurrence of short hiatus at the P/E boundary. 2) 95 cm of calcareous shale; this sediments contains rare of fish remains. 3) 175 cm of calcarenitic marly limestone, this sediment consists mainly planktonic foraminiferal ooze.
Darb Gaga Member (New): Name: From Darb Gaga area, 20 km North of Baris Oasis, Western Desert, Egypt. Type section: Darb Gaga section, at latitude 24° 54' 32" N and longitude 30° 57' 30" E Lithology: Darb Gaga Member consists of alternative well bedded shale and marl. Boundaries: The lower boundary is the top of the calcarenitic marly limestone bed of El- Dababiya Quarry Member. The upper boundary is the base of Abu Had Member. Thickness and distribution: The thickness of Darb Gaga Member is about 11 meters at Darb Gaga area. It is distributed at the east of Baris Oasis (Fig. 1). Regional correlation: Darb Gaga Member is equivalent to El-Mahmiya Member of Aubry et al. (2007), which cover the main part of the Esna Unit 2 of Dupuis et al. (2003) at GSSP section (Fig. 5 & Table 1).
Biostratigraphic characterization and age: According to the planktonic foraminiferal zones, this member belongs to Pseudohastegerina wilcoxensis/ Morozovella velascoensis (E2) Zone and Morozovella subbotinae (E3) Zone, which assign that, Darb Gaga Member is of early Eocene age. Genetic interpretation: this member may represent the lateral changes in the sedimentary facies between the siliciclastics facies of Esna Formation at north and the carbonate facies of Garra Formation at south (Fig. 5).
N.A. Obaidalla, M.H. El Dawy, K.H. Mahfouz and S.A. Abdel-Wahed VII- 83
Fig. (4): Field photograph showing the beds of El Dababiya Quarry Member and their stratigraphic relationship with El-Hanadi Member, Darb Gaga, Western Desert, Egypt (for legend, show figure 3).
Fig. (5): Hypothetical diagram shows the lateral lithological facies changes between Esna Formation at north and Garra Formation at south.
VII- 84 Stratigraphy Of The Paleocene-Eocene Succession At Darb Gaga Area, …….
Abu Had Member The Abu Had Member was introduced by Abdel Razik (1972) as part of the Thebes Formation for the alternating shales and limestone at the transition between the monotonous shales of the Esna Formation and the massive limestones of the Thebes Formation. Aubry et al. (2007) assign the Abu Had Member to the Esna Formation because of the clear-cut contact between the massive limestones and the shale facies. The Abu Had Member corresponds to the Esna Unit 3 of Dupuis et al., (2003) (Table 1). At Darb Gaga area, Abu Had Member is well defined, it is about 74 meters thick. This member mainly consists of shale, which contains operculinida at base and interacted with Nummulitic bank at several levels toward top. Thebes Formation The Thebes Formation was introduced by Said (1960) to describe 290 meters thick limestone section with many flint bands that overlies the Esna Formation at Gabal Gurnah, in the western side of the Nile facing Luxor. At Darb Gaga area, the Thebes Formation consists of thick succession of massive limestone papery at the base. The measured section of Thebes Formation is about 16.60 meters thick at the present study. Table (1): Correlation of the rock units of the present work with some pervious works in Egypt.
BIOSTRATIGRAPHY Although, the lower part of the Dababiya Quarry Member (beds 1& 2) is absent due to a short hiatus at the P/E boundary at Darb Gaga area, the Paleocene/Eocene Thermal Maximum (PETM) foraminiferal excursion taxa (Acarinina africana (El Naggar), A. sibaiyaensis (El Naggar) and Morozovella allisonensis (Kelly, Bralower & Zachos)) are well represented within the upper parts (beds 3, 4 &5) of this member. The foraminiferal assemblage is nearly similar to the Global Stratotype Section and Point (GSSP) of the P/E N.A. Obaidalla, M.H. El Dawy, K.H. Mahfouz and S.A. Abdel-Wahed VII- 85
boundary at Dababiya section. According to the important planktonic foraminiferal species (Plate 1 & 2), six zones for the late Paleocene-early Eocene interval are recognized in the studied section. The planktonic foraminiferal zonal scheme of Berggren and Pearson, (2005) and its categories for the Paleocene and early Eocene are here applied with minor modification. The proposed planktonic foraminiferal zones arranged from base to top are as follows:
1- Morozovella velascoensis Zone This zone was originally defined by Bolli (1957, 1966) to characterize the interval from the HO of Globanomalina pseudomenardii (Bolli) to the HO of M. velascoensis (Cushman) in the latest Paleocene. Berggren & Ouda (2003 a, b) subdivided P5 Zone into three subzones namely P5a (latest Paleocene), P5b to recognize the Carbon Isotope Excursion (CIE) and Paleocene/Eocene Thermal Maximum (PETM) interval and P5c to recognize the post CIE and PETM interval (earliest Eocene). Recently, Berggren & Pearson (2005) used P5 Zone (=P5a Subzone of Berggren & Ouda, 2003 a,b) to recognize the latest Paleocene before the CIE & PETM interval. At the same time, they used E1 and E2 zones (=P5b & P5c subzones of Berggren & Ouda, 2003 a,b) to recognize the CIE & PETM and post CIE & PETM intervals respectively. In the present work, the M. velascoensis (P5) Zone is defined as a partial range zone from the HO of G. pseudomenardii (Bolli) to the LO of Planktonic Foraminiferal Excursion Taxa such as: A. africana (El Naggar), A. sibaiyaensis (El Naggar) and M. allisonensis Kelly, Bralower & Zachos at the P/E boundary (Table 2). Age: latest Paleocene Remarks: M. velascoensis Zone is equivalent to P5 Zone of Berggren & Pearson (2005) and Wade et al. (2011). This zone covers the uppermost part of El Hanadi Member (Fig. 6).
2- Acarinina sibaiyaensis Zone
This zone is defined as a Lowest-Occurrence Zone from the LO A. sibaiyaensis (El Naggar) to the LO of Pseudohastigerina wilcoxensis (Cushman & Ponton). Pardo et al. (1999) subdivided the P5 Zone of Berggren et al. (1995) into two subzones namely: P5a (latest Paleocene) and P5b (earliest Eocene) according to the LO of A. sibaiyaensis (El Naggar) and/or A. africana (El Naggar). Later, Berggren & Pearson (2005) used this zone to recognize the earliest Eocene which covers the CIE & PETM interval. Acarinina sibaiyaensis (E1) Zone is well represented at Darb Gaga section. Age: Earliest Ypresian. Remarks: A. sibaiyaensis Zone is equivalent to E1 Zone of Berggren & Pearson, (2005) and Wade et al. (2011). This zone comprises the Dababiya Quarry Member, except for the uppermost part of bed 5 (Fig. 6).
3- Pseudohastigerina wilcoxensis/Morozovella velascoensis Zone
P. wilcoxensis/M. velascoensis Zone was originally defined as a Concurrent-Range Zone from the LO P. wilcoxensis (Cushman & Ponton) to the HO of M. velascoensis (Cushman)
VII- 86 Stratigraphy Of The Paleocene-Eocene Succession At Darb Gaga Area, ……. by Dupuis et al., 2003; Berggren & Ouda, 2003 a &b. It is here completely equivalent to P. wilcoxensis Subzone of Molina et al. (1999) and the upper part of M. velascoensis (P5) Zone of Berggren et al. (1995) (Table 2). Age: early Ypresian. Remarks: P. wilcoxensis/M. velascoensis Zone is equivalent to E2 Zone of Berggren & Pearson, (2005) and Wade et al. (2011). It covers the uppermost part of bed 5 (Dababiya Quarry Member) and the lower part of Darb Gaga Member (Fig. 6).
4- Morozovella subbotinae Zone
M. subbotinae Zone was defined as Partial-Range Zone from the HO M. velascoensis (Cushman) to the LO of M. formosa (Bolli) by Obaidalla (2006). Berggren & Pearson (2005) used M. marginodentata (Subbotina) to mark the E3 Zone as a partial range zone from the HO of M. velascoensis (Cushman) to the LO of M. formosa (Bolli). In the present study, M. marginodentata (Subbotina) is rarely represented within this interval. So, M. subbotinae (Morozova) is used to mark this zone instead of M. marginodentata (Subbotina) (Table 2). Age: early Ypresian. Remarks: M. subbotinae Zone is equivalent to E3 Zone of Berggren & Pearson, (2005) and Wade et al. (2011). It comprises the upper part of Darb Gaga Member (Fig. 6).
5- Morozovella formosa Zone
M. formosa Zone is defined as Lowest-Occurrence Zone from the LO of M. formosa (Bolli) to the LO of M. aragonensis (Nuttall). Age: late Ypresian. Remarks: M. formosa Zone is equivalent to E4 Zone of Berggren & Pearson, 2005 and Wade et al. (2011). It comprises the lowermost part of Abu Had Member (Fig. 6).
6- Morozovella aragonensis/Morozovella subbotinae Zone
It was originally defined as Concurrent-Range Zone from the LO of M. aragonensis (Nuttall) to the HO of M. subbotinae (Morozova) by Berggren & Pearson, 2005. This zone is equivalent to the M. aragonensis/M. formosa formosa Zone (P7) of Berggren et al. 1995 (Table 2). Age: Ypresian. Remarks: M. aragonensis/M. subbotinae Zone is equivalent to Zone E5 of Berggren & Pearson, 2005 and Wade et al. (2011). This Zone covers the Abu Had Member and the lower part of Thebes Formation (Fig. 6). N.A. Obaidalla, M.H. El Dawy, K.H. Mahfouz and S.A. Abdel-Wahed VII- 87
Fig. (6): Biostratigraphic distribution chart of the planktonic foraminiferal species recorded throughout the Paleocene-Eocene succession at Darb Gaga section, Western Desert, Egypt.
VII- 88 Stratigraphy Of The Paleocene-Eocene Succession At Darb Gaga Area, …….
Table (2): Comparison of the present planktonic foraminiferal zones with some local and international ones.
THE PALEOCENE/EOCENE BOUNDARY
The Paleocene/Eocene boundary is one of the most effective catastrophic events on various groups of organisms. At about 55 Ma a global warming event led to produce an anoxic environment. This event believed to have initialized in marine and transited into terrestrial environments. It is coincident with an abrupt Carbon Isotope Excursion (CIE) and abrupt extinction of deep-sea benthonic foraminifera known as Benthonic Formainiferal Extinction Event (Kennett & Stott, 1991; Pak & Miller, 1992; Kaiho et al., 1996). Several scenarios were proposed to interpret the P/E event: 1) tectonism, due to the collision of the Indian Plate with Asia (Beck et al., 1998), 2) volcanism, due to the increased volcanic and submarine hydrothermal activity (Owen & Rea, 1985; Sttott & Kennett, 1990; Eldholm & Thomas, 1993; Schmitz et al., 2004), 3) continental slope failure due to the increased current strength in north Atlantic Ocean (Katz et al., 1999), 4) sea-level lowering and high productivity, especially in the Tethys region (Spijer & Wagner, 2002), and 5) impact of comet (Kent et al., 2003; Cramer & Kent, 2005). One or more of these scenarios caused a thermal dissociation of sea floor methane hydrates (Dickens et al., 1995; Dickens, 2000), which led to greenhouse warming due to the increased atmospheric-oceanic CO2, H2S and CH4 (Owen & Rea, 1985; Sttott & Kennett, 1990; Eldholm & Thomas, 1993). This massive release and oxidation of CH4 from oceanic gas hydrates may have produced an anoxic environment for the benthonic dwellers (Sloan et al., 1992; Dickens et al., 1995; Dickens, 1998). On the other hand, the planktonic foraminiferal fauna show good diversification and turnover before and after the P/E event (Canudo & Molina, 1992; Lu & Keller, 1995; Canudo et al., 1995; Arenillas & Molina, 1996; Lu et al., 1996; Arenillas et al., 1996). Formally, the Global Stratotype Section and Point (GSSP) of the P/E boundary is selected and defined at Dababiya Village, south Luxor (Egypt) during the meeting of the "Subcommission on Stratigraphy" at Luxor, Egypt (Aubry et al., 2007). The P/E boundary is marked by the occurrence of five distinctive beds within the Esna Formation at Dababiya section. These beds were named as Dababiya Quarry Beds by Dupuis et al. (2003). In 2007, Aubry et al. raised the stratigraphic rank of these beds from Dababiya Quarry Beds into Dababiya Quarry Member. This member consists of five beds arranged N.A. Obaidalla, M.H. El Dawy, K.H. Mahfouz and S.A. Abdel-Wahed VII- 89
from base to top as follow: bed 1 (63 cm thick) clay; bed 2 (50 cm thick) phosphatic shale; bed 3 (84 cm thick) cream-colored, laminated phosphatic shale; bed 4 (71 cm thick) grey shale and bed 5 (100 cm thick) marly calcarenitic limestone. The P/E boundary was defined at the base of clay (Bed no. 1) at a level coincident with the Paleocene/Eocene Thermal Maximum (PETM) and the CIE. In addition to the GSSP, there are some complete stratigraphic sections for the P/E boundary in Egypt such as: Wadi Matulla, southwestern Sinai (Obaidalla, 1999), Qreiya (Knox et al., 2003), and Wadi Tarfa, north Eastern Desert (Obaidalla, 2006). At Darb Gaga, the P/E boundary is well defined within the Esna Formation at the base of El-Dababiya Quarry Member (Fig. 4). Here El-Dababiya Quarry Member consists of only three beds (beds 3, 4 and 5) whereas, beds 1&2 are absent due to a short hiatus. This hiatus is marked by the presence of glauconitic grains at the basal part of this member (Fig. 2 b&c). Biostratigraphically, the P/E boundary is defined at Morozovella velascoensis (P5)/Acarinina sibaiyaensis (E1) zonal boundary. Accordingly, the P/E boundary at Darb Gaga is characterized by the occurrence of interzonal hiatus due to the missing of lowermost part of Dababiya Quarry Member, which is covered by the lowermost part of zone E1 and the uppermost part of El Hanadi Member which is covered by the uppermost part of zone P5. The planktonic foraminiferal excursion taxa (e.g. Acarinina africana (El Naggar), A. sibaiyaensis (El Naggar) and Morozovella allisonensis Kelly et al.) are well represented, where the foraminiferal assemblages are more or less as the same of these assemblages at the Global Stratotype Section and Point (GSSP).
CONCLUSIONS
The litho- and biostratigraphic studies on the Paleocene-Eocene succession at Darb Gaga, Baris Oasis, Western Desert, Egypt has led to: 1- The Paleocene-Eocene succession at Darb Gaga area is differentiated into two rock units: Esna (at base) and Thebes (at top) formations. Esna Formation is subdivided into four members: El-Hanadi, El-Dababiya Quarry, Darb Gaga and Abu Had members. 2- Darb Gaga is here introduced for the first time to describe the sedimentary sequence which consists of alternating marl and shale beds. The thickness of each bed ranges from 20 to 30 cm. This member is conformably underlain by El-Dababiya Quarry Member and is conformably overlain by Abu Had Member. The thickness of Darb Gaga Member reaches about 11 m thick. 3- Darb Gaga Member is here interpreted as lateral facies change from the Nile valley siliciclastics Esna facies and the carbonate Garra facies. 4- El-Dababiya Quarry Member which marks the P/E boundary is well represented at the study area. The basal part (beds 1&2) is absent, while the upper part consists of three beds (beds 3, 4 & 5). These beds are as follow: i- laminated phosphatic shale rich with glauconitic sediments at base and contains fish debris and coprolites, ii-calcareous shale and iii-calcarenitic marly limestone. The thickness of this member reaches about 3.75 m thick. 5- Biostratigraphically, six planktonic foraminiferal zones are identified, one for the latest Paleocene and five for the early Eocene. The latest Paleocene zone is Morozovella velascoensis (P5), and the early Eocene zones are Acarinina sibaiyaensis (E1) at base, Pseudohastegerina wilcoxensis/Morozovella velascoensis (E2), Morozovella subbotinae (E3), Morozovella formosa (E4) and Morozovella aragonensis/Morozovella subbotinae
VII- 90 Stratigraphy Of The Paleocene-Eocene Succession At Darb Gaga Area, …….
(E5) at top. The P/E boundary is defined at (P5)/(E1) zonal boundary. 6- The P/E boundary is marked by the occurrence of a minor interzonal hiatus at the (P5)/(E1) zonal boundary. This hiatus is supported by the occurrence of glauconitic sediments at the base of El-Dababiya Quarry Member and the absence of beds 1and 2.
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Pardo, A., Keller, G. and Oberhansli, H., 1999. Paleoecologic and paleoceanographic evolution of the Tethyan realm during the Paleocene-Eocene transition. Journal of Foraminiferal Research, vol. 29 (1), 37-57. Said, R., 1960. Planktonic foraminifera from the Thebes Formation, Luxor, Egypt. Micropaleontology, 6 (3), 277-286. Said R., 1961. Tectonic framework of Egypt and its influence on the distribution of foraminifera. American Association of Petroleum Geologists Bulletin, 45, 198-218. Said R., 1962. The geology of Egypt. Amsterdam: Elsevier, 377 p. Said R., 1990. Editor, The geology of Egypt. Rotterdam: Balkema, 734p. Schmitz, B., Peucker-Ehrenbrink, B., Heilmann-Clausen, c., Aberg, G., Asaro, F. and Lee, A. C-T, 2004. Basaltic explosive volcanism, but no comet impact, at the Paleocene-Eocene boundary: high-resolution chemical and isotopic records from Egypt, Spain and Denmark. Earth and Planetary Science Letters, 225, 1-17. Sloan, L C., Walker, J. C. G., Moore, T. C. JR., Rea, D. K. and Zachos, J. c., 1992. Possible methane induced polar warming in the early Eocene. Nature, 357, 320-322. Speijer, R. P. and Wagner, T., 2002. Sea-level changes and black shales associated with the late Paleocene thermal maximum: organic¬geochemical and micropaleontologic evidence from the southern Tethyan margin (Egypt-Israel). In: Koeberl C. and Macleod, K. G. Eds. Catastrophic events and mass extinctions: Impacts and beyond. Geological Society of America (Special Paper), 356, 533-549. Stott, L. D. and Kennett, J. P., 1990. Antarctic Paleocene planktonic foraminifera biostratigraphy: ODP Leg 113, Site 689 and 690: Proceedings ODP, Scientific Results, 113, 549-569. Tantawy A. A., 1998. Stratigraphical and paleoecological studies on some Paleocene- Eocene successions in Egypt. Unpublished Ph. D. Thesis, South Valley University, Aswan, Egypt, 273 p., 27 pls. Toumarkine, M., and Luterbacher H. P., 1985. Paleocene and Eocene Planktic Foraminifera. In H. M. Bolli, J. B. Saunders, and K. Perch-Nielsen, editors, Plankton Stratigraphy, pages 87-154. Cambridge: Cambridge University Press. Wade B. S., Pearson P. N, Berggren W. A., & Pälike H., 2011. Review and revision of Cenozoic tropical planktonic foraminiferal biostratigraphy and calibration to the geomagnetic polarity and astronomical time scale. Earth-Science Reviews, 104, 111-142.
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Plate (1):
N.A. Obaidalla, M.H. El Dawy, K.H. Mahfouz and S.A. Abdel-Wahed VII- 95
Plate (1): (Scale bar is 100 μm) 1-2 Morozovella aequa (Cushman & Renz), Sample no. 47, 3-4 Morozovella subbotinae (Morozova), Sample no. 47, 5-6 Morozovella velascoensis (Cushman), Sample no. 31, 7-8 Morozovella aragonensis (Nuttall), Sample no. 48, 9-10 Morozovella gracilis (Bolli), Sample no. 47, 11-12 Morozovella formosa (Bolli), Sample no. 45, 13-14 Morozovella allisonensis Kelly, Bralower & Zachos, Sample no. 23, 15-16 Morozovella edgari (Premoli Silva & Bolli), Sample no. 35, 17-18 Acarinina sibaiyaensis (El Naggar), Sample no. 22, 19-20 Acarinina africana (El Naggar), Sample no. 22.
VII- 96 Stratigraphy Of The Paleocene-Eocene Succession At Darb Gaga Area, …….
Plate 2:
N.A. Obaidalla, M.H. El Dawy, K.H. Mahfouz and S.A. Abdel-Wahed VII- 97
Plate (2): (Scale bar is 100 μm) 1-2 Acarinina soldadoensis (Brönnimann), Sample no. 27, 3-4 Acarinina esnaensis (LeRoy), Sample no. 47, 5-6 Acarinina esnehensis (Nakkady), Sample no. 47 , 7-8 Acarinina triplex Subbotina, Sample no. 45, 9-10 Acarinina wilcoxensis (Cushman & Ponton), Sample no. 45, 11-12 Parasubbotina varianta (Subbotina), Sample no. 5 , 13-14 Subbotina hornibrooki (Brönnimann), Sample no. 31, 15-16 Subbotina patagonica (Todd & Kniker), Sample no. 31, 17-18 Globanomalina luxorensis (Nakkady), sample no. 6, 19-20 Pseudohastigerina wilcoxensis (Cushman & Ponton), Sample no. 27.
EIGHTH INTERNATIONAL CONFERENCE ON THE GEOLOGY OF AFRICA P-P VII- 99 - VII-124 (NOV. 2015) ASSIUT- EGYPT
MACRO-BIOSTRATIGRAPHY INTEGRATION OF THE CENOMANIAN - TURONIAN TRANSITION AT NORTH EASTERN DESERT AND SOUTHWESTERN SINAI, EGYPT
Mahmoud H. Darwish, Mohamed S. Zakhera, Nasr A. Abdel-Maksoud and Nageh A. Obaidalla Geology Department, Faculty of Science, New Valley Branch, Assiut University, New Valley, Egypt Geology Department, Faculty of Science, Aswan University, Aswan, Egypt Geology Department, Faculty of Science, Assiut University, Assiut, Egypt E-mail: [email protected]
ABSTRACT
The Cenomanian-Turonian successions are well exposed at north Eastern Desert (Wadi Tarfa and Wadi El Dakhl) and southwestern Sinai (Wadi Abu Qada and Wadi Feiran). These successions are composed of siliciclastic and carbonate sediments belonging to the Raha (at the base), Abu Qada and Wata formations (at the top). These sediments yield a diverse and well preserved macro-fauna. Based on the vertical distribution of the macro-fauna, the Cenomanian–Turonian successions has been subdivided into five bivalve zones, and four echinoid zones coeval with eight ammonite zones. The bivalve zones are Ceratostreon flabellatum, Exogyra (Costagyra) olisiponensis, and Pycnodonte (Phygraea) vesiculosa for the Cenomanian age, Arca passyana and Crassatella sequenzai for the Turonian age. The echinoid zones are Mecaster cubicus, Mecaster pseudofourneli and Mecaster batnensis for the Cenomanian age and Mecaster turonensis for the Turonian age. The ammonite zones are Neolobites vibrayaenus, Metoicoceras geslinianum and Vascoceras cauvini for the Cenomanian age, Watinoceras praecursor, Vascoceras proprium, Mammites nodosoides, Choffaticeras segne and Coilopoceras requienianum for the Turonian age. The index ammonite Watinoceras devonense is here recorded for the first time in Egypt. This species was used as a marker for the base of the Turonian Stage at Pueblo, Colorado, U.S.A. (GSSP). The Cenomanian/Turonian (C/T) boundary is located within the Abu Qada Formation, coinciding with the base of the ammonite Watinoceras praecursor Zone, the bivalve Arca passyana Zone and the echinoid Mecaster turonensis Zone. It is characterized by the occurrence of irregular surface, which indicates the occurrence of a short hiatus at this boundary. Keywords: Cenomanian; Turonian; ammonites; bivalves; echinoids; Wadi Tarfa; Wadi El Dakhl; Wadi Abu Qada; Wadi Ferian; Eastern Desert; Sinai.
INTRODUCTION
The Cenomanian-Turonian (Upper Cretaceous) successions are well exposed at the north part of Egypt, including beds extremely rich in macro-fauna. The Cenomanian-Turonian outcrops occur bording the northern-most Cretaceous belt, extending from northern and western Sinai, through the north Eastern Desert (between Gebel Shabrawet and Wadi Qena), and Western Desert (Baharya Oasis and Abu Roash). VII- 100 Macro-Biostratigraphy Integration Of The Cenomanian – Turonian,…
Generally, the Upper Cretaceous successions of the north Eastern Desert and Sinai have been studied by many authors. The Cenomanian-Turonian successions were studied separately or with these studies of Upper Cretaceous successions. Some relevant paleontologic and stratigraphic publications about these important areas of Egypt are those of: Kora and Hamama (1987a,b), Lüger and Gröschke (1989), Klitzsch and Hermmina (1989), Hamama and Kassab (1990), Malchus (1990), Kassab and Hamama (1991), Abdel-Gawad and Gameil (1992), Kora et al. (1993, 1994), Kassab and Zakhera (1999, 2002), El- Shiekh et al. (1998), Abdel-Gawad (1999), Zakhera (2001, 2002), Abdallah et al. (2001), Kassab and Obaidalla (2001), Abdel-Gawad and Gameil (2002), Abdel-Shafy et al. (2002a,b), Kora et al. (2002), Zakhera et al. (2002), Hewaidy et al. (2003), Abdel- Gawad et al. (2004a,b), El-Hedeny (2002), Abdel-Gawad et al. (2006, 2007), Kassab and Abdel-Maksoud (2007), El Qot (2004, 2006, 2008, 2010), Nagm (2009), Gertsch et al. ( 2010), Nagm et al. (2010), El-Sabbagh et al. (2011), Nagm and Wilmsen (2012), and Saber (2012). The aim of the present work is to study the macro-fauna of Cenomanian –Turonian succession exposed at four columnar sections, Wadi Tarfa and Wadi El-Dakhl at North Easrern Desert and Wadi Abu Qada and Wadi Ferian at West Central Sinai (Fig. 1) to construct an integrated macro-biostratigraphical scheme for a precise definition of the Cenomanian–Turonian boundary. The intercalibration method has been used for the integration of the proposed macro-fossil zones; the first occurrence datum (FOD) and last occurrence datum (LOD) of the identified fossils have been used for a precise definition of the biostratigraphical zonal limits.
LITHOSTRATIGRAPHY
By comparing the lithostratigrphic framework of the fossiliferous Cenomanian-Turonian successions exposed in the studied sections with the stratotypes of the lithostratigrphic units established for this stratigraphic interval in the Stratigraphy of Egypt, three rock units are advocated, namely: the Raha Formation of late Cenomanian age (at the base), Abu Qada Formation, late Cenomanian- early Turonian age (at the middle) and Wata Formation of middle–late Turonian age (at the top). Stratigraphical details of these formations are given in figures 2-5.
Fig. (1): Location map of the studied sections.
M. H. Darwish, M. S. Zakhera, N. A. Abdel-Maksoud and N. A. Obaidalla VII - 101
BIOSTRATIGRAPHY
Based on the vertical distribution of the macro-fossils (Figs.2-5), the Cenomanian– Turonian successions exposed at the studied sections were subdivided into eight ammonite zones coeval to five bivalve zones and to four echinoid zones. The intercalibration method has been used for the integration of the proposed macrofossil zones (Tab. 1), the first occurrence datums (FOD) and last occurrence datums (LOD) of the identified fossils have been used for a precise definition of the biostratigraphical zonal limits. The zones are correlated with those established by previous authors for the same time interval of other Egyptian areas. Moreover, they are correlated with other inter-regional zonal schemes (Tabs. 2-4). The different invertebrate macro-fossils zones are discussed in the following:
I- The ammonite Zones: In an ascending order, the proposed ammonite zones are: A1- Neolobites vibrayeanus Total-Range Zone Boundaries: This zone is defined by the total range of the nominate taxon. It represents the oldest identified ammonite zone in the studied sections. Occurrence: This zone is recorded from the upper part of the Raha and lower part of the Abu Qada formations at Wadi Feiran section. At the remainder sections, the Raha Formation is unexposed, so that, Neolobites vibrayeanus Zone is only represented by the lower part of Abu Qada Formation. Faunal Assemblage: Neolobites fourtaui Pervinquiére and Angulithes mermeti (Coquand), are recorded from the stratigraphic interval of this zone (Figs. 2-5). Correlation: This zone is equivalent to the late Cenomanian N. vibrayeanus Zone of Abdel- Gawad (1999), Kassab & Obaidalla (2001), Zakhera (2001), Zakhera & Kassab (2002), Abdel- Gawad et al., (2004), and Kassab & Abdel-Maksoud (2007). Inter- regionally, this zone correlates with the Neolobites vibrayeanus Zone of Niger (Meister et al., 1992), occupied Palestine (Freund & Rabb, 1969), the Eucalycoceras pentagonum Zone of Tunisia (Robaszynski et al., 1993, and Abdallah & Meister, 1997), the Calycoceras guerangeri Zone of Europe (Wright & Kennedy, 1981, Gale et al., 2005) and the M. mosbyense of USA (Bengtson, 1996) (Tabs. 2,3). Age: Late Cenomanian. A2- Metoicoceras geslinianum Total-Range Zone Boundaries: It is defined by the total range of the nominate taxon. The Metoicoceras geslinianum Zone rests conformably on the Late Cenomanian Neolobites vibrayeanus Zone. Occurrence: This zone is recorded from the middle part of Abu Qada Formation at all the studied sections. Faunal Assemblage: Pseudaspidoceras pseudonodosoides (Choffat) are recorded from the stratigraphic interval of the zone (Figs. 2-5). Correlation: The Metoicoceras geslinianum Zone is equivalent to the M. geslinianum Zone of Kassab (1999,), Galal et al. (2001), Zakhera & Kassab (2002), and Kassab & Abdel-Maksoud (2007); and to part of Vascoceras cauvini - Pseudaspidoceras pseudonodosoides - R. alatum Zone of Abdel-Gawad et al. (2004a). Inter-regionally, it can be correlates with the M. geslinianum Zone of Tunsia and Europe (Wright & Kennedy, 1981; Lehmann, 1999 and Gale et al., 2005) (Tabs. 2,3). Age: Late Cenomanian.
VII- 102 Macro-Biostratigraphy Integration Of The Cenomanian – Turonian,…
A3- Vascoceras cauvini Total-Range Zone Boundaries: It is defined by the total range of nominate taxon. It is conformably rest on the Late Cenomanian Metoicoceras geslinianum Zone. Occurrence: It is recorded from the upper part of Abu Qada Formation at all the studied sections. Faunal Assemblage: Vascoceras gamai Choffat, Spathites (Jeanrogericeras) subconciliatus (Choffat) and Pseudaspidoceras pseudonodosoides (Choffat), are recorded from the stratigraphic interval of this zone (Figs. 2-5) Correlation: The Vascoceras cauvini Zone is equivalent to the Vascoceras gamai, Vascoceras rumeaui and Vascoceras cauvini zones of Lüger & Gröschke (1989), the V. cauvini Zone of Kassab (1999), Kassab & Obaidalla (2001), Zakhera (2001), El-Hedeny (2002), Zakhera & Kassab (2002), and Abdelhady (2007) and to V. cauvini / Pseuda. pseudonodosoides Zone of Kassab & Abdel-Maksoud (2007). Inter-regionally, it can be correlates with the V. cauvini Zone of Niger (Meister et al., 1992 and Pascal et al., 1993), Kanabiceras sp. and V. cauvini zones of occupied Palestine (Freund & Rabb, 1969), Pseudaspidoceras pseudonodosoides Zone of Tunisia (Robaszynski et al., 1993, Abdallah & Meister, 1997), Neocardioceras juddii Zone of Europe (Wright & Kennedy, 1981, Lehmann, 1999) and Buttoceras clydense, Neocardioceras juddii and Nigericoceras scotti of USA (Bengtson, 1996) (Tabs.2,3). Age: Latest Cenomanian. A4- Watinoceras praecursor Total-Range Zone Boundaries: This zone is defined by the total range of the nominate taxon. At Wadi El Dakhl section this zone is characterized by the occurrence of W. devonense taxon which was used by Bengtson, 1996 to define the C/T boundary at the GSSP. The later taxon is here recorded for the first time in Egypt. It represents the Earliest Turonian ammonite zones at the studied sections. It rests unconformably (short hiatus) on the V. cauvini Zone of the Latest Cenomanian age at Wadi Tarfa, Wadi El Dakhl and Wadi Feiran sections. At Wadi Abu Qada section the W. praecursor Zone is absent which indicates the occurrence of a long hiatus at the C-T boundary. Occurrence: This zone is recorded from the upper part of Abu Qada Formation at Wadi Tarfa, Wadi El Dakhl and Wadi Feiran sections, but it is missing at Wadi Abu Qada section. Faunal Assemblage: Watinoceras devonense, Vascoceras durandi (Thomas & Peron), Vascoceras obessum (Taubenhaus), Vascoceras rumeaui (Collignon), Pseudaspidoceras paganum Reyment, Kamerunoceras calvertense (Powell), Paramammites polymorphus (Pervinquiére), Thomasites cf. rollandi (Thomas & Peron), Paravascoceras compressum (Powell), Fagesia superstes (Kossmat), and Neoptychites cephalotus (Courtiller) are recorded from the stratigraphic interval of the zone (Figs. 2-5). Correlation: This zone is equivalent to a part of the earliest Turonian V. durandi Zone of Lüger & Gröschke (1989); a part of the Pseudaspidoceras flexuosum/V. proprium Zone of Kassab (1999), and Zakhera & Kassab (2002); with a part of the V. proprium/V. obessum Zone of Kassab & Obaidalla (2001); with a part of Choffaticeras segne Zone of Abdel- Gawad (1999), Abdel–Gawad et al. (2004a); with a part of Vascoceras Proprium/Choffaticeras segne Zones of Khalil & Mashaly (2004); and a part of V. proprium/Watinoceras praecursor Zone of Kassab and Abdel-Maksoud (2007). Inter- regionally, it correlates with a part of the V. proprium Zone (Meister et al., 1992., Pascal et al., 1993); a part of the V. pioti Zone (Freund & Rabb, 1969., Lewy et al., 1984); a part of with the Pseudaspidoceras flexuosum Zone (Robaszynski et al., 1993; Abdallah & M. H. Darwish, M. S. Zakhera, N. A. Abdel-Maksoud and N. A. Obaidalla VII - 103
Meister, 1997; Cobban & Hook, 1983; Kennedy et al., 1987); with a part of the Watinoceras cloradoense Zone (Wright & Kennedy, 1981; Lehmann, 1999., Gale et al., 2005) and with the Watinoceras devonense Zone (Kennedy & Cobban, 1991, Hancock et al., 1993) of USA (Bengtson, 1996) (Tabs. 2,3). Age: Earliest Turonian. A5- Vascoceras proprium Total-Range Zone Boundaries: It is defined by the total range of the nominate taxon. It rests conformably on the Watinoceras praecursor Zone. Occurrence: This zone is recorded from all the studied sections. Faunal Assemblage: Vascoceras durandi (Thomas & Peron), Vascoceras obessum (Taubenhaus), Vascoceras pioti (Peron & Fourtau), Kamerunoceras calvertense (Powell), Paramammites polymorphus (Pervinquiére), Fagesia peroni Pervinquière, Neoptychites cephalotus (Courtiller), Thomasites cf. rollandi (Thomas & Péron), Choffaticeras securiforme (Eck) and Choffaticeras quaasi (Péron), are recorded from the stratigraphic interval of this zone (Figs. 2-5). Correlation: This zone is equivalent to a part of the Early Turonian V. durandi Zone of Lüger & Gröschke (1989); a part of the Pseudaspidoceras flexuosum/V. proprium Zone of Kassab (1999), Zakhera (2001) and Zakhera & Kassab (2002); a part of the V. proprium/V. obessum Zone of Kassab & Obaidalla (2001); a part of Choffaticeras segne Zone of Abdel- Gawad (1999), Abdel–Gawad et al. (2004a); and a part of V. proprium/W. praecursor Zone of Kassab and Abdel-Maksoud (2007). Inter-regionally, it correlates with a part of the V. proprium Zone (Meister et al., 1992; Pascal et al., 1993); a part of the V. pioti Zone (Freund & Rabb, 1969;); a part of the Pseudaspidoceras flexuosum Zone (Robaszynski et al., 1993; Abdallah et al., 1995; Abdallah & Meister, 1997; Kennedy et al., 1987); a part of the Watinoceras cloradoense Zone (Wright & Kennedy, 1981; Wright et al., 1984; Lehmann, 1999; Gale et al., 2005) and Pseudaspidoceras flexuosum Zone of (Caron et al.; 2006, Robaszynski et al., 2010) of USA (Bengtson, 1996) (Tabs. 2,3). Age Early Turonian. C6- Mammites nodosoides Total-Range Zone Boundaries: This zone is defined by the total range of the nominate taxon. It rests conformably on the Vascoceras proprium Zone. Occurrence: This zone is recorded from the upper most part of Abu Qada Formation at all the studied sections sections. Faunal Assemblage: Vascoceras durandi (Thomas & Peron), Paramammites polymorphus (Pervinquiére), Neoptychites cephalotus (Courtiller), Choffaticeras quaasi (Peron), Choffaticeras securiforme (Eck), Fagesia peroni (Pervinquière) and Thomasites rollandi globosa (Thomas & Peron) are recorded from the stratigraphic interval of this zone (Figs. 2-5). Correlation: This zone is more or less equivalent to the Choffaticeras segne Zone of Kora & Hamama (1987), Kassab & Obaidalla (2001), El- Hedeny (2002), Abdel–Gawad et al. (2004a), and El- Sabbagh et al., (2011); and to Mammites nodosoides Zone of Zakhera (2001), Zakhera & Kassab (2002), and Kassab & Abdel-Maksoud (2007). Inter-regionally, the Mammites nodosoides Zone can be correlates partially or completely with Mammites nodosoides Zone Wright & Kennedy, 1981; Wright et al., 1984; Robaszynski et al., 1993; Abdallah et al., 1995; Abdallah & Meister, 1997; Lehmann, 1999; Gale et al., 2005; Caron et al., 2006; V. birchbyi Bengtson, 1996; Watinoceras coloraddoense Zone (Kennedy & Cobban 1991; Hancock et al. 1993; Abdallah et al. 2000); Thomasites rollandi (Caron et al. 2006) (Tabs.2,3). Age: Early Turonian.
VII- 104 Macro-Biostratigraphy Integration Of The Cenomanian – Turonian,…
C7- Choffaticeras segne Total-Range Zone Boundaries: It is defined by the total range of the nominate taxon. It rests conformably on the early Turonian Mammites nodosoides Zone. Occurrence: This zone covers the interval sediments from the uppermost part of the Abu Qada Formation to the lower part of the Wata Formation at all the studied sections. Faunal Assemblage: Vascoceras durandi (Thomas & Peron), Choffaticeras securiforme (Eck), Choffaticeras pavillieri Pervinquiére and Choffaticeras luciae (Pervinquiére) are recorded from the stratigraphic interval of this zone (Figs.2-5). Correlation: The present zone is equivalent to the Turonian Choffaticeras segne Zone of Zakhera (2001), Zakhera & Kassab (2002) and Kassab & Abdel-Maksoud (2007), it correlates to the Mammites nodosoides Zone of Aly & Abdel-Gawad (2001) and El- Sabbagh (2008) (Tabs.2,3). Age: Middle Turonian. C8- Coilopoceras requienianum Partial-Range Zone Boundaries: This zone is defined by the partial range of the nominate taxon from its FOD to the top of the successions (Figs.4&5). It rests conformably over the Middle Turonian Choffaticeras segne Zone. Occurrence: The Coilopoceras requienianum Zone is recorded from the upper part of Wata Formation at Wadi Abu Qada and Wadi Feiran sections. It is missing at north Eastern Desert (Wadi Tarfa and Wadi El Dakhl sections) due to the absence of the upper part of Wata Formation at this area. Correlation: The present zone is equivalent to the Turonian Coilopoceras requienianum Zone of Kora & Hamama (1987), Kassab (1999), Abdel-Gawad (1999), Kassab & Obaidalla (2001), Zakhera (2001), Zakhera & Kassab (2002), Abdel-Gawad et al. (2004a), El-Sabbagh (2008) and El-Sabbagh et al. (2011). It can be correlates with the Coilopoceras inflatum Zone of Meister et al. (1992) and Pascal et al (1993) (Tabs.2,3). Age: Late Turonian.
II-The bivalve Zones
B1- Ceratostreon flabellatum Interval Zone Boundaries: This zone is delineated to cover the interval from the base of the studied sections to the LAD of the nominate taxon. Occurrence: This Zone is recorded from the Raha and Abu Qada formations at all the studied sections. Faunal Assemblage: Ilymatogyra (Afrogyra) africana (Lamarck), Exogyra (Costagyra) olisiponensis (Sharpe), Rhynchostreon mermeti (Coquand), Gyrostrea delettrei (Coquand), Exogyra pseudoafricana (Choffat), Maghrebella forgemoli (Coquand), Curvostrea rouvillei (Coquand), Plicatula auressensis Coquand, Plicatula batnensis Coquand, Venericardia (Venericardia) deserti (Douvillé), Arctica picteti (Coquand), Granocardium productum (Sowerby), Acesta ( Acesta) hoernesi (Zittel), Protocardia hillana (Sowerby), Dosinia delettrei, (Coquand), Cucullaea (Idonearca) diceras (Seguenza), Plectomya humei (Fourtau) and Glossus (Glossus) solimani,are recorded from the stratigraphic interval of this zone (Figs.2-5). Correlation: This zone is equivalent to a part of Ilymatogyra (Afrogyra) africana and Exogyra (Costagyra) olisiponensis zone of Kassab & Ismael (1996) (Tab.4). Age: Late Cenomanian.
M. H. Darwish, M. S. Zakhera, N. A. Abdel-Maksoud and N. A. Obaidalla VII - 105
B2- Exogyra (Costagyra) olisiponensis Interval Zone Boundaries: It is delineated to define the interval from the LOD of the Ceratostreon flabellatum to the FOD of the Pycnodonte (Phygraea) vesiculosa. Occurrence: This zone is recorded from the Abu Qada Formation at all the studied sections. Faunal Assemblage: Ilymatogyra (Afrogyra) africana (Lamarck), Gyrostrea delettrei (Coquand), Exogyra pseudoafricana (Choffat), Astarte (Astarte) tenuicostata (Seguenza), Plicatula auressensis Coquand, Plicatula batnensis Coquand, Plicatula (Plicatula) reynesi Coquand, Plicatula fourneli Coquand, Neithea (Neithea) aequicostata (Lamark), Arctica picteti (Coquand), Rastellum carinatum (Lamark), Cucullaea (Idonearca) diceras (Seguenza), Arctica humei (Cox), Meretrix plana (Sowerby), and Granocardium productum (Sowerby), are recorded from the stratigraphic interval of this zone (Figs.2-5). Correlation: This zone is equivalent to Pycnodonte vesiculosum, Exogyra (Costagyra) olisiponensis, Ilymatogyra (Afrogyra) africana and Ceratostreon flabellatum zones of Abdel-Gawad (1999 Exogyra (Costagyra) olisiponensis, , Ilymatogyra (Afrogyra) africana zones of Khalil & Mashaly (2004) (Tab.4) . Age: Late Cenomanian. B3- Pycnodonte (Phygraea) vesiculosa Total-Range Zone Boundaries: It is delineated to define the interval which is covered by the total stratigraphic range of the nominate taxon. Occurrence: It is recorded from the Abu Qada Formation of all the studied sections. Faunal Assemblage: Plicatula auressensis Coquand, Plicatula (Plicatula) reynesi Coquand, Plicatula fourneli Coquand, Neithea (Neithea) aequicostata (Lamark), Glossus aquilina (Coquand), Liopistha (Liopistha) aequivalves Goldfuss, Arctica orientalis (Hamlin), Granocardium hassani Abbass, Arca (Barbatia) gigantea Abbass, Falventia plana (Sowerby), Cucullaea (Idonearca) diceras (Seguenza), Granocardium productum (Sowerby) and Anatina jetti Coquand are recorded from the stratigraphic interval of this zone (Figs.2-5). Correlation: This zone is equivalent to Ostrea olisiponensis Zone of Hume (1911), a part of Exogyra suborbiculata Zone of Awad & Issawi (1975), Exogyra olisiponensis /Ilymatogyra africana Zone of Kora & Hamama (1987a), Exogyra olisiponensis/ Hemiaster pseudofourneli Zone of Shahin (1988), Exogyra olisiponensis Zone of Kora et al. (1993), Ilymatogyra africana/Costagyra olisiponensis Zone of Kassab & Ismael (1996), Pycnodonte vesiculosum/Exogyra olisiponensis Zone of Abdel-Gawad (1999), Acesta obliquistriata Zone of Kassab & Zakhera (1999), Exogyra olisiponensis Zone of Kora et al., (2001), and Khalil & Mashaly (2004), Pycnodonte vesicularis Zone of Abdelhady (2007), and Exogyra (Ceratostreon) olisiponensis Zone of El-Sabbagh (2008) (Tab.4). Age: Latest Cenomanian. B4- Arca (Eonavicula) passyana Interval Zone Boundaries: This zone is delineated to cover the interval LOD of Pycnodonte (Phygraea) vesiculosa to the LOD of the nominate taxon. Occurrence: It is recorded from the upper part of Abu Qada Formation at all the studied sections. Faunal Assemblage: Plicatula auressensis Coquand, Plicatula (Plicatula) reynesi Coquand, Plicatula fourneli Coquand, Plicatula batnensis Coquand, Plicatula instabilis Stoliczka, Neithea (Neithea) aequicostata (Lamark), Arctia cordata (Sharpe), Liopistha (Liopistha) aequivalves Goldfuss, Flaventia plana (Sowerby), Flaventia faba (Sowerby), Flaventia brongniartina (Leymerie), Linearia (Linearia) subtenuistriata (ďOrbigny), VII- 106 Macro-Biostratigraphy Integration Of The Cenomanian – Turonian,…
Septifer (Septifer) samiri, (Abbass), Schedotrapezium trapezoidale (Römer), Cucullaea (Idonearca) thevestensis (Coquand), Pteria (Electroma) hadhirensis Abbass, Pholadomya vignesi Lartet, Pholadomya pedernalis Römer, Priscomactra angulata (Sowerby) are recorded from the stratigraphic interval of this zone (Figs.2-5). Correlation: This zone is equivalent to Mytiloides opalensis elongate and Arca passyana zones of Zakhera (2001), Crassatella incurva Zone and a part of Inoceramus labiatus- Arca passyana Zone of Kassab and Zakhera (1999), Neithia (Neithia) dutrugei Zone of Abdelhady (2007) and Durania humei Zone of Awad and Issawi (1975) (Tab.4). Age: Early Turonian. B5- Crassatella (Crassatella) seguenzai Interval Zone: Boundaries: This zone is delineated to cover the interval from the LOD of Arca (Eonavicula) passyana to the LOD of the nominate taxon. Occurrence: This zone is recorded from the lower part of Wata Formation at all the studied sections. Faunal Assemblage: Plicatula (Plicatula) reynesi Coquand, Plicatula fourneli Coquand, Plicatula instabilis Stoliczka, Flaventia plana (Sowerby), Flaventia faba (Sowerby), Flaventia brongniartina (Leymerie), Pholadomya pedernalis Römer, are recorded from the stratigraphic interval of this zone (Figs.2-5). Correlation: This zone is equivalent to Inoceramus (Mytiloides) labiatus Zone of Zakhera (2001) and a part of Inoceramus labiatus-Arca passyana Zone of Kassab and Zakhera (1999) (Tab.4). Age: Middle-Late Turonian.
III -The echinoid Zones
E1- Mecaster cubicus Total-Range Zone Boundaries: This zone is delineated to define the interval which is covered by total stratigraphic range of the nominate taxon. Occurrence: This zone is recorded from the Raha and Abu Qada formations at all the studied sections except for Wadi Abu Qada. Correlation: It is equivalent to the Hemiaster cubicus Zone of Khalil & Mashaly, (2004) and Abdel-Gawad et al. (2006, 2007). Age: Late Cenomanian. E2- Mecaster pseudofourneli Interval Zone Boundaries: It is delineated to cover the interval from the LOD of Mecaster cubicus to the LOD of the nominate taxon. Occurrence: The Mecaster pseudofourneli Zone is recorded from the Abu Qada Formation at all the studied sections except for Wadi Abu Qada. Faunal Assemblage: Coenholectypus pulvinatus (Desor) and Mecaster batnensis (Coquand) (Figs.2-5). Correlation: This zone is equivalent to the Ilymatogyra africana- Heterodiadema libycum- Hemiaster (Mecaster) pseudofourneli Zone of Abdel-Gawad et al., (2006). Age: Late Cenomanian. E3- Mecaster batnensis Interval Zone Boundaries: This zone is delineated to cover the interval from the LOD of Mecaster pseudofourneli to the FOD of Mecaster turonensis. Occurrence: It is recorded from all the studied sections except for Wadi Abu Qada. M. H. Darwish, M. S. Zakhera, N. A. Abdel-Maksoud and N. A. Obaidalla VII - 107
Faunal Assemblage: Mecaster pseudofourneli (Peron and Gauthier), Heterodiadema libycum (Agassiz and Desor), Coenholectypus pulvinatus (Desor) and Micropedina olisiponensis (Forbes) (Figs.2-5). Correlation: This zone is equivalent to the Mecaster batnensis Zone of Kassab & Abdel- Maksoud, (2007). Age: Latest Cenomanian. E4- Mecaster turonensis Total-Range Zone Boundaries: This zone is delineated to define the interval which is cover by the total range of the nominate taxon. Occurrence: This zone is recorded from the upper part of Abu Qada Formation at all the studied sections except for Wadi Abu Qada. Faunal Assemblage: Coenholectypus turonensis (Desor) (Figs.2-5). Correlation: This zone is equivalent to the Hemiaster (Mecaster) heberti turonensis – Coenholectypus turonensis Acme Zone of Abdel-Gawad et al. (2004a, 2007) and Hemiaster heberti turonensis Zone of Kassab and Abdel-Maksoud (2007). Age: Early Turonian.
VII- 108 Macro-Biostratigraphy Integration Of The Cenomanian – Turonian,…
Fig. (2): Stratigraphic-range of the identified macro-fossils and zonation of the Cenomanian–Turonian successions at Wadi Tarfa section
Fig. (3): Stratigraphic-range of the identified macro-fossils and zonation of the Cenomanian–Turonian successions at Wadi El Dakhl section
M. H. Darwish, M. S. Zakhera, N. A. Abdel-Maksoud and N. A. Obaidalla VII - 109
Fig. (4): Stratigraphic-range of the identified macro-fossils and zonation of the Cenomanian–Turonian successions at Wadi Abu Qada section
VII- 110 Macro-Biostratigraphy Integration Of The Cenomanian – Turonian,…
Fig. (5): Stratigraphic-range of the identified macro-fossils and zonation of the Cenomanian–Turonian successions at Wadi Feiran section
M. H. Darwish, M. S. Zakhera, N. A. Abdel-Maksoud and N. A. Obaidalla VII - 111
THE CENOMANIAN/TURONIAN (C/T) BOUNDARY
The C/T boundary at north Eastern Desert and southwestern Sinai is marked by the occurrence of thin bed consists of silty shale which is intercalated within the marl and limestone rocks of the upper part of Abu Qada Formation (Fig. 6). This interval is rich in ammonites belonging to the Latest Cenomanian - Earliest Turonian time, and is occurred at all the studied sections except for Wadi Abu Qada section due to a hiatus at the C/T boundary. The boundary is characterized by the occurrence of irregular surface at Wadi Tarfa, Wadi El Dakhl and Wadi Feiran. This irregular surface indicates the occurrence of interzonal hiatus (short hiatus) at these sections. The C/T boundary coincides with the contact between the Late Cenomanian ammonite Vascoceras cauvini and the basal Turonian Watinoceras praecursor zones at Wadi Tarfa, Wadi El Dakhl and Wadi Feiran sections. At Wadi Abu Qada section the basal Turonian sediments are missing due to the occurrence of a long hiatus than the remainder sections. This hiatus is evidenced by the absence of the Earliest Turonian ammonites taxa (e.g. Watinoceras praecursor). The C/T boundary corresponds to the contact between the late Cenomanian bivalve Pycnodonte vesiculosa Zone and the basal Turonian Arca (Eonavicula) passyana Zone and the contact between the Late Cenomanian echinoid Mecaster batnensis Zone and the basal Turonian echinoid Mecaster turonensis Zone. The important bioevent which mark the C/T at the studied sections are (Fig.6): 1- The LOS of the ammonite Vascoceras cauvini, the bivalve Pycnodonte vesiculosa and the echinoid Mecaster batnensis taxas. 2- The FOS of the ammonite Watinoceras praecursor and Watinoceras devonense, the bivalve Arcca (Eonavicula) passyana and the echinoid Mecaster turonensis taxa.
VII- 112 Macro-Biostratigraphy Integration Of The Cenomanian – Turonian,…
Turonian
Cenomanian
Fig. (6): Bioevents at the Cenomanian-Turonian boundary at the studied sections
M. H. Darwish, M. S. Zakhera, N. A. Abdel-Maksoud and N. A. Obaidalla VII - 113
BIOSTRATIGRAPHY INTEGRATION
The integrated biostratigraphy is a technique that applied to establish simultaneous biostratigraphical zonal schemes of multi-fossil groups based on integrated sampling. At the present study, integration of the proposed ammonite, bivalve, and echinoid zones has been achieved using the inter-calibration method of Koutsoukos and Bengtson (1993). Integration of the established zones has revealed the following (Tab.1): 1- The late Cenomanian ammonite Neolobites vibrayeanus (A1) Zone is coeval to the bivalve Ceratostreon flabellatum (B1) and Exogyra olisiponensis (B2)(lower part) zones and to the echinoid Mecaster cubicus (E1)(upper part) and Mecaster pseudofourneli (E2)(lower part) zones. 2- The Late Cenomanian ammonite Metoicoceras geslinianum (A2) Zone is correlate with the middle part of the bivalve Exogyra olisiponensis (B2) Zone and with the upper part of the echinoid Mecaster pseudofourneli (E2) Zone. 3- The Latest Cenomanian ammonite Vascoceras cauvini (A3) Zone is coeval to the bivalve Exogyra olisiponensis (B2)(upper part) and Pycnodonte vesiculosa (B3) zones and moreless to the echinoid Mecaster batnensis (E3) Zone. 4- The early Turonian ammonite Watinoceras praecursor (A4), Vascoceras proprium (A5) and Mammites nodosoides (A6) zones are moreless coeval to the bivalve Arca (Eonavicula) passyana (B4) Zone and to the echinoid Mecaster turonensis (E4)(main part) Zone. 5- The middle Turonian ammonite Choffaticeras segne (A7) Zone is correlate to bivalve Arca (Eonavicula) passyana (B4) (upper part) Zone and Crassatella seguenzai (B5) Zone and upper part of the echinoid Mecaster turonensis (E4) Zone. 6- The stratigraphic interval which is covered by the Turonian ammonite Coilopoceras requienianum (A8) zone is nearly characterized by the absence of both bivalve and echinoid fauna. CONCLUSIONS
The Cenomanian–Turonian transition exposed at north Eastern Dersert and southwestern Sinai, Egypt, has been classified lithostratigraphy into three formations, namely: Raha (at base), Abu Qada (at middle) and Wata (at top). Based on vertical distribution of the macrofauna, 8 ammonite zones coeval with 5 bivalve and 4 echinoid zones have been established. The ammonite zones are: Neolobites vibrayaenus, Metoicoceras geslinianum, Vascoceras cauvini, Watinoceras praecursor, Vascoceras proprium, Mammites nodosoides, Choffaticeras segne and Coilopoceras requienianum. The bivalve zones are Ceratostreon flabellatum, Exogyra (Costagyra) olisiponensis, Pycnodonte (Phygraea) vesiculosa, Arca passyana and Crassatella sequenzai. The echinoid zones are Mecaster cubicus, Mecaster pseudofourneli, Mecaster batnensis and Mecaster turonensis. The established cephalopod, bivalve and echinoid zones have been integrated based on the inter-calibration method and correlated with zonal schemes established in literature for other well dated regional and inter-regional sections. The proposed zonal schemes have been used to define the C/T boundary which has been located at the upper part of the Abu Qada Formation at the contact between the late Cenomanian Vascoceras cauvini and the earliest Turonian Watinoceras praecursor ammonite zones. In general, the C/T boundary is characterized by the occurrence of a short hiatus at Wadi Tarfa, Wadi El Dakhl and Wadi Feiran. This hiatus is recorded within Abu Qada Formation and lies within irregular surface. This irregular surface lies at the Vascoceras cauvini (latest Cenomanian) and Watinoceras praecursor (earliest Turonian) zonal boundary. On the other hand, the C/T boundary at Wadi Abu Qada section is marked by the absence of the earliest Turonian ammonite Zone (Watinoceras praecursor Zone). VII- 114 Macro-Biostratigraphy Integration Of The Cenomanian – Turonian,…
This indicates that the hiatus at Abu Qada section is longer than that at the remainder sections. The important bioevents at the C/T boundary are the LOS of ammonite Vascoceras cauvini, the bivalve Pycnodonte vesculosa and echinoid Mecaster batnensis taxa, and FOS of ammonite Watinoceras praecursor, Watinoceras devonense, the bivalve Arca (Eonavicula) passyana and the echinoid Mecaster turonensis taxa.
Table (1): Integration of the cephalopod, bivalve and echinoid zones proposed for the Cenomanian–Turonian in the studied sections.
Age Formation Cephalopod Zones Bivalve Zones Echinoid Zones Coilopoceras Barren Barren requienianum
Total - Range Zone (A8) Crassatella seguenzai Wata Choffaticeras segne Interval Zone (B5) Total - Range Zone (A7)
Mammites nodosoides Mecaster turonensis Total - Range Zone (A6) Total - Range Zone (E4)
Turonian Arca (Eonavicula) passyana Vascoceras proprium Interval Zone (B4) Total - Range Zone (A5)
Watinoceras praecursor Total - Range Zone (A4) Pycnodonte vesiculosa Vascoceras cauvini Total - Range Zone (B3) Mecaster batnensis Abu Qada Total - Range Zone (A3) Interval Zone (E3)
Metoicoceras geslinianum Exogyra olisiponensis Total - Range Zone (A2) Interval Zone (B2) Mecaster pseudofourneli
Cenomanian Interval Zone (E2)
Neolobites vibreanus Ceratostreon flabellatum Total - Range Zone (A1) Mecaster cubicus
Raha Interval Zone (B1) Total - Range Zone (E1)
Table (2): Possible regional Cenomanian–Turonian zones correlations proposed of this study with other localities in Egypt
Kora & Luger Kassab Kassab & Galal et al.,2001 Kora et al., Kassab, Kora et al., Hamama, & Gröschke, & Abdel-Gawad, Obaidalla, The present )north 1993 1999 2001
Age 1987 1989 Ismael, 1996 1999(Sinai) 2001 study Eastern Desert) (Sinai) (Gulf of Suez) (Gulf of Suez)
(Sinai) (Wadi Qena) (Sinai) (Sinai) Coilopoceras Coilopoceras Coilopoceras requenianum Coilopoceras Coilopoceras Coilopoceras requienianum requienianum Coilopoceras requienianum requienianum requienianum
newelli
M. nodosoides Mammites Choffaticeras Thomasites sp nodosoides segne Choffaticeras Fagesia cf. segne
segne segne superstes Choffateceras
Turonian
Choffaticeras Choffateceras Choffateceras segne Mammites segne nodosoides Choffaticeras segne Vascoceras P.flexuosum Mammites P.flexuosum V. proprium Mammites Vascoceras Vascoceras proprium / nodosoides / / nodosoides durandi proprium V. proprium V. proprium V. obesum Watinoceras praecursor P.vesiculosum V. cauvini
Vascoceras - Exogyra Vascoceras Vascoceras
V. rumeaui E. (C.) Vascoceras olisiponensis cauvini Exogyra cauvini cauvini V. gamai olisiponensis cauvini olisiponensis
E. (C.) Ilymatogyra Il. africana olisiponensis Metengo. cf Metoicoceras Barren Metoicoceras Il. africana- Metoicoceras africana / / acutum geslinianum Interzone geslinianum C. flabellatum geslinianum / Neolobites Ilymatogyra vibrayeanus
Costagyra Neolobites Cenomanian
africana Neolobites Il. africana olisiponensis vibrayeanus vibrayeanus Neolobites Neolobites Neolobites / vibrayeanus vibrayeanus vibrayeanus Hemiaster Neolobites Costagyra Hemiaster cubicus vibrayeanus cubicus olisiponensis
VII- 116 Macro-Biostratigraphy Integration Of The Cenomanian – Turonian,…
Table (2): Continued.
Gertsch et al., Aly & Zakhera & Kassab & Abdel- Abdel-Gawad et Zakhera, El-Hedeny, Abdel-Gawad et Khalil & 2010 (Sinai) & Abdel- Kassab, Maksoud, al., 2006, 2007 & The present 2001 2002 al., 2004a Mashaly, El-Sabbagh et
Age Gawad, 2001 2002 2007 Saber, 2012 (north study (Sinai) (Sinai) (Sinai) 2004 (Sinai) al., 2011 (NE (Sinai) (Sinai) (Sinai) Eastern Desert) Egypt) Coilopoceras Coilopoceras Coilopoceras Coilopoceras Coilopoceras Coilopoceras Coilopoceras requienianum requienianum requienianum requienianum requienianum requienianum requienianum
Choffaticeras Choffaticeras Choffateceras Choffaticeras Choffaticeras Mammites segne segne sinaticum segne segne nodosoides Choffaticeras
segne
ras
segne
Mammites Choffaticeras Mammites Mammites Mammites
Choffatice
/
Turonian nodosoides segne nodosoides nodosoides nodosoides
segne
Choffaticeras Vascoceras
P. flexuosum P. flexuosum segne V. proporium P. flexuosum Pseuda. Vascoceras Choffaticeras proprium
/ / / Vascoceras
flexuosum proprium segne Choffateceras Watinoceras Vascoceras proprium Vascoceras
V. proprium V. proprium W. praecursor proprium praecursor V. Cauvini
Vascoceras Vascoceras Vascoceras Vascoceras Exogyra / Vascoceras Vascoceras Vascoceras Vascoceras cauvini cauvini cauvini cauvini olisiponensis P. cauvini cauvini cauvini cauvini pseudonodosoides
P. Metoicoceras Metoicoceras Il. africana Metoicoceras pseudonodosoides Metoicoceras geslinianum geslinianum / geslinianum / geslinianum Neolobites R.alatum vibrayeanus Neolobites Neolobites vibrayeanus
Neolobites Neolobites Cenomanian
vibrayeanus vibrayeanus vibrayeanus Amphidonte Neolobites Neolobites Neolobites Neolobites flabellatum Neolobites vibrayeanus vibrayeanus vibrayeanus vibrayeanus Acanthoceras vibrayeanus Hemiaster amphibolum cubicus
M. H. Darwish, M. S. Zakhera, N. A. Abdel-Maksoud and N. A. Obaidalla VII - 117
Table (3): Possible zones correlations proposed for the Cenomanian–Turonian successions of this study with other well Inter- regional. Wright & Cobban & Hook, Robaszynski et al., Freund & Kennedy, 1981, 1983, Cobban, Meister et al., 1993, Abdallah et Raab, 1969 Bengtson, Wright et al., Robaszynski et 1984, 1986 (New 1992 al., 1995 and Caron et al., 2006 he present and Lewy et 1996 1984, Lehmann, al., 2010
Age Mexico & USA) and Pascal et Abdallah & (Tunisia & USA) study al., 1984 (GSSP) 1999 and Gale et (Tunisia) and Kennedy et al., al.,1993 (Niger) Meister, 1997 (Negev) al., 2005 1987 (W. Texas) (Tunisia) (Europe) Coilopoceras Coilopoceras
inflatum requienianum
Collignoniceras Collignoniceras Collignoniceras Choffaticeras woollgari woollgari Woollgari segne
Mammites Mammites Mammites Mammites Choff. luciae nodosoides nodosoides nodosoides nodosoides
onian trisellatum Mammites
Tur Pseudotissotia Mammites Choff. quaasi Vascoceras Vascoceras nodosoides Thmasites rollandi
nigeriensis nodosoides birchbyi birchbyi Choffaticeras Watinoceras securiforme coloraddoense Pseudaspidoceras Pseudaspidoceras Pseudaspidoceras Vascoceras Vascoceras Pseudaspidoceras Vascoceras flexuosum Pseudaspidoceras flexuosum flexuosum proprium pioti flexuosum proprium Watinoceras flexuosum Watinoceras Watinoceras sp. Watinoceras sp. devonense praecursor Vascoceras Neocardioceras Nigericeras scotti Neocardioceras Pseudaspidaceras Pseudaspidaceras cauvini juddi Vascoceras Pseudaspidaceras Vascoceras Neocardioceras juddi juddi pseudonodosoids pseudonodosoids cauvini pseudonodosoids cauvini Kanabiceras Vascoceras Buttoceras clydense sp. cauvini Calycoceras Sciponoceras Nigericeras Sciponoceras sp. gracile gadeni gracile Euomphaloceras Metoicoceras Metoicoceras Metoicoceras Metoicoceras septemseriatum geslinianum geslinianum
Cenomanian geslinianum
Neolobites mosbyense Neolobites Metoicoceras vibrayeanus vibrayeanus mosbyense Calucoceras Eucalycoceras Calucoceras Neolobites
guerangeri pentagonum guerangeri vibrayeanus VII- 118 Macro-Biostratigraphy Integration Of The Cenomanian – Turonian,…
Table (4): Possible correlation of the bivalve zones proposed for the Cenomanian–Turonian successions of this study with other localities in Egypt.
Kora & Abdelhady, Zakhera, 1999 Kassab and Awad & Issawi, Shahin, Zakhera, Hume, 1911 Hamama, 2007 And Kassab & Abdel- El-Sabbagh, The present 1975 1988 2001
Age (Egypt) 1987a (N. Wadi Zakhera, 1999 Maksoud 2007 2008 study (Egypt) (Sinai) (Sinai) (Sinai) Qena) (N. E. Desert) (Sinai) Inoceramus Crassatella (Mytiloides) Hemitissotia sp. seguenzai Inoceramus labiatus / labiatus Pseudotissotia sp. Neithia Meretrix / (Neithea) Arca passyana dutrugei Mammites Arca passyana Arca dutrugei Turonian nodosoides Mytiloides (Eonavicula) Crassatella Durania humei opalensis passyana incurva elongata P. vesiculosum Ostrea Exogyra Pycnodonte Acesta Pycnodonte Pycnodonte Exogyra / olisiponensis suborbiculata vesicularis obliquistriata vesiculosa Exogyra (C.) vesiculosa olisiponensis Ex. olisiponensis / / olisiponensis Ostrea mermeti Exogyra (C.) Ostrea Hemiaster Costagyra olisiponensis Exogyra flabellata Exogyra africana pseudofourneli Ilymatogyra olisiponensis Barren / Ilymatogyra olisiponensis / africana Ilymatogyra africana Neolobites fourtaui Il. africana Exogyra (C.) / Ostrea africana / Ilymatogyra africana Exogyra / olisiponensis Aporrhais (A.)africana Cenomanian Ceratostreon Rhynchostreon olisiponensis Cer. flabellatum dutrugei flabellatum Mermeti - Ceratostreon / / -Opis Ostrea Ceratostreon Ceratostreon flabellatum Hemiaster Rh. sub- haldonensis suborbiculata flabellatum flabellatum pseudo-fourneli orbiculatum
M. H. Darwish, M. S. Zakhera, N. A. Abdel-Maksoud and N. A. Obaidalla VII - 119
Plate 1 1, 2 Neolobites vibrayeanus (ďOrbigny); 3, 4 Metoicoceras geslinianum (ďOrbigny); 5, 6 Vascoceras cauvini Chudeau; 7- 9 Watinoceras praecursor Wright & Kennedy. Scale bar = 1cm.
1 2 33
5 66 4 4
7 8 9 7 8 Plate 2 1, 2 Vascoceras proprium (Reyment); 3, 4 Mammites nodosoides (Schlüter); 5, 6 Choffaticeras segne (Solger); 1.2; Scale bar = 3cm; 3-6, Scale bar = 1cm.
1 3 1 2 2
5 6 4 VII- 120 Macro-Biostratigraphy Integration Of The Cenomanian – Turonian,…
Plate 3 1, 2 Coilopoceras requienianum (ďOrbigny); 3, 4 Ceratostreon flabellatum (Goldfuss); 5, 6 Exogyra (Costagyra) olisiponensis (Sharpe); 7, 8 Pycnodonte (Phygraea) vesiculosa (Sowerby); 9, 10 Arca (Eonavicula) passyana d’Orbigny. 1, 2; Scale bar = 3cm; 3- 10, Scale bar = 1cm.
1 2
3 4 5 6
9 7 8 10
Plate 4 1- 4 Crassatella (Crassatella) seguenzai (Thomas & Peron); 5, 6 Mecaster cubicus (Desor); 7, 8 Mecaster turonensis (Fourtau); 9, 10 Mecaster batnensis (Coquand); 11 Mecaster pseudofourneli (Peron & Gauthier). Scale bar = 1cm.
1 22 3 4
77 55 6 5 6 6 6 8
99 101
0 111
1
M. H. Darwish, M. S. Zakhera, N. A. Abdel-Maksoud and N. A. Obaidalla VII - 121
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COMPARATIVE STUDIES OF RECENT AND FOSSIL ECHINOID JACKSONASTER DEPRESSUM FROM THE NORTHERN BAY OF SAFAGA AND LATE PLIOCENE ROCKS OF THE RED SEA COAST, EGYPT
Atef Abdelhamied Elattaar Geology Department, Faculty of Science, Sohag University (Sohag), Egypt, D- 82524, Sohag, Egypt (e-mail: [email protected])
ABSTRACT
Statistical correlation, ontogenetic development and sexual dimorphism have been studied in recent and fossil specimens of Jacksonaster depressum (L. Agassiz, 1841). A large number of dead and living tests of this species have been collected from bottom sediments of the Safaga Bay, Red Sea, Egypt. Out of two hundred specimens, one hundred and seventy seven (20 living and 157 dead, including 25 females and 95 males) were measured, analyzed statistically and correlated with measurements of 61 fossil tests (32 females and 29 males) collected by Elattaar (2003) from the Late Pliocene sediments of Wadi Wizr, south of Quseir City, along the Red Sea coast. Morphological and statistical differences between recent and fossil tests and gender include test shape, apical system, length, width and number of pore pairs of petals, and position and shape of periproct and peristome; these are discussed in detail. Scatter diagrams for ontogenetic development of both recent and fossil tests are plotted and discussed in detail. Sedimentary facies of the recent and fossil tests are explained. Keywords: Echinoidea, Jacksonaster depressum, Pliocene, Safaga Bay, Red Sea coast, Egypt. INTRODUCTION
The present study is based on a large number of recent (live and dead) and fossil tests of Jacksonaster depressum (L. Agassiz, 1841). The recent samples of this species were collected from twenty sites from the Northern Bay of Safaga, Red Sea, Egypt, at depths ranging from10-50 m. (Fig. 1) (Nebelsick, 1992b, 1999). The recent tests of J. depressum were correlated statistically with other fossil tests (32 males and 29 females) collected from one bed and one locality of Late Pliocene sediments (Sharm El-Arab Member of Philobbos & El Haddad, 1983, Shagra Formation of El Akkad & Dardir, 1966) at Wadi Wizr, 40 km south of Quseir City, Red Sea coast, Egypt (Figs.1, 2) by Elattaar (2003). The Northern Bay of Safaga area lies on the west coast of Red Sea on the Egyptian territory between 33° 56' and 34° 00' eastern longitude and 26° 37' and 26° 52' northern latitude. It measures approximately 10 km in north-south and 7 km in west-east directions, separated from the open marine sea by a broad submarine ridge, with greatest depth 55 m. (Fig. 1). The water temperature annually ranges between 21°C in winter and 29°C in summer, salinity ranges between 40 ‰ to 46 ‰. (Piller & Pervesler (1989)). Several works on the Red Sea and the Northern Bay of Safaga includes information about the topography of sea floor and bottom facies (Piller & Pervesler, 1989), VII-126 Comparative Studies Of Recent And Fossil Echinoid Jacksonaster Depressum,… sedimentary facies (Piller & Mansour, 1990, 1994; Piller, 1994) and echinoids (Dollfus & Roman, 1981; Nebelsick,1992a, b,1996; Nebelsick & Kampfer, 1994; Nebelsick & Kowalewski, 1999; Rasul & Stewart, 2015; Nebelsick & Elattaar, 2009). Nebelsick (1992a, b) studied the distribution of fragments and complete tests of J. depressum in the Northern Bay of Safaga. He found it living very shallowly buried in silty sands, and its fragments found in a wide variety of sediments ranging from poorly sorted medium sands from the edge of muddy basins to coral carpets within the basins in the muddy sand bottom facies and molluscan sedimentary facies.
Suez 100 Km
Aqaba Sinai EGYPT
Hurghada EGYPT
Safaga Bay
El-Quseir Wadi Wizr
Fig. 1: Location map showing the Safaga Bay in the western side of the Red Sea and Wadi Wizr on the Red Sea coast of Egypt.
Legend
Wadi Wizr
Formation Member logic Units logic Geochrono- Collected fossils Quater- R*.C.
nary Reefs Reefal Limestone Conglomerates
Late Cross-bedded Arab El S*. Sandstone
Shagra Sandstone
Limestone D*. ElDabaa ElDabaa D*.
e n e c o i l P Unconformities Early Early 10 m *R: Raised Coral Reefs
*S: Sharm El Arab Mb. Gabir
*D: Dashet ElDabaa Mb. Marsa Alam Marsa
Fig. 2: Measured columnar section showing the vertical lithology and location of the collected fossils at Wadi Wizr, 40 km south of Quseir City, Red Sea coast, Egypt. (modified after Elattaar, 2003). Atef Abdelhamied Elattaar VII-127
Nebelsick (1992a, 1996) explained the methods used for collecting the echinoid remains from the Sea bottom of Safaga Bay: (1) intensive collecting of both live and dead tests during numerous diving trips throughout the study area; (2) disinterment of the sediment with a stout garden rake in order to collect infaunal irregular echinoids. The material from coral carpet and coral reefs was collected from sediment pockets. The present work is intended to throw light on two aspects of recent and/or fossil J. depressum: (1) a detailed systematic description of recent and fossil J. depressum and their ontogenetic variation. (2) study of the statistical differences between the recent and fossil tests and between males and females.
SYSTEMATIC DESCRIPTION
All specimens of the studied echinoid species were measured in millimeters with an ocular micrometer scale in the small tests and a caliper in the larger ones. The classification of Durham (1966) has been followed here.
A Wps W B
Was Wgp 2
Las
Lps L
D.pr-ps
Lpr
D.pr-pm Lpt Wpt 5 mm Wpr
Fig. 3: Measurement protocol used for biometric analysis on oral (A) and aboral (B) surfaces of recent Jacksonaster depressum (L. Agassiz, 1841).
Abbreviations: D.pr-pm: Distance of periproct to posterior margin. D.pr-ps: Distance of periproct to peristome. L: Length of test. Las: Length of apical system. Lpr: Length of periproct. Lps: Length of peristome. Lpt: Length of petals. Npp: Number of pore pairs in single poriferous zone. Pr: Periproct. Ps: Peristome. W: Width of test. Was: Width of apical system. Wgp2: Width of genital pore 2. Wpr: Width of periproct. Wps: Width of peristome. Wpt: Width of petals.
VII-128 Comparative Studies Of Recent And Fossil Echinoid Jacksonaster Depressum,…
Phylum Echinodermata Klein, 1734 Subphylum Echinozoa Haeckel, 1895 Class Echinoidea Leske, 1778 Subclass Euechinoidea Bronn, 1860 Superorder Gnathostomata Zittel, 1879 Order Clypeasteroida L. Agassiz, 1872 Suborder Laganina Mortensen, 1948 Family Laganidae A. Agassiz, 1873 Genus Jacksonaster Lambert & Thiery, 1914 Type species Laganum depressum L. Agassiz, 1841 Jacksonaster depressum (L. Agassiz, 1841) (Figs. 1, 8, 9, 10)
1841 Laganum depressum L. Agassiz, p. 110, pl. 23, figs. 1-7. 1893 Laganum delicatum Mazzetti, p. 241, text-figs. a-d. 1894 Laganum fragile Mazzetti, p. 217, text-figs. a-d. 1909 Laganum mazzetti, Thiéry, p.137. 1948 Laganum depressum, Mortensen, p. 313 (complete synonymy), pl. 52, figs. 12, 14, pl. 53, figs. 3, 4, 6-32, 31, 32, pl. 70, fig. 20, text-figs. 153b, 157, 161b, 162c, 163b, 165, 167, 196a. 1948 Laganum depressum, vare. delicatum, Mortensen, p. 318, pl. 53, figs. 6, 10, 11, 13, 15-20, 22, 23. 1951 Laganum depressum, Tortonese, p. 240. 1955 Jacksonaster depressum, Durham, p. 143, 144, text-figs.1h, 5j, 7a, 26h, 31c. 1966 Jacksonaster depressum, Durham, text-figs. 336/1h, 348/10, 351/ 8, 352/1. 1968 Laganum depressum, Nisiyama, p. 74, (complete synonymy), pl. 15, figs. 11-16; p. 375. 1971 Laganum depressum, Clark & Rowe, p.144, 162, text-fig. 77, pl.25, fig. 10. 1972 Laganum depressum, Kier, p.13, 94, 95. 1975 Laganum depressum, Abed, p.173, pl. 1, fig. 1. 1975 Laganum depressum n. var. A., Abed, p. 173, pl. 1, figs. 4, 5. 1981 Laganum depressum, Dollfus & Roman, p. 89, pl. 28, figs. 6-7; pl. 31, figs.1-10; pl. 33, fig.7. 1981 Laganum depressum var. elliptica, Dollfus & Roman, pl. 31, figs. 9, 10. 1985 Laganum depressum, Ali, p. 288. 1989 Laganum depressum, Al-Rifaiy & Cherif, pl. 8, figs. 7a, b. 1992a Laganum depressum, Nebelsick, p. 319, fig.3 j. 1992b Laganum depressum, Nebelsick, p. 28, pl. 7, figs. 7-10. 2000 Laganum depressum, Kora & Abdel-Fattah, pl. 3, figs. 8a, b. 2001 Laganum depressum, Elattaar, p. 654, pl. 4, figs. 4-6. 2003 Jacksonaster depressum, Elattaar, p. 285, pl. 1, figs.1-6; pl. 2, figs. 1-6; pl. 3, figs.1- 14, pl. 4, figs. 1-8; pl. 5, figs. 1-10; pl. 6, figs. 1-16; text-figs.3-8. 2003 Laganum depressum sinaiticum, Lindley, p. 133, figs. 3c-d. 2003 Laganum depressum delicatum, Lindley, p. 134, figs. 3e-h. 2009 Jacksonaster depressum, Nebelsick & Elattaar, p.397, 398.
Material Examined: Out of two hundred recent tests, 177 tests, including 95 males and 25 females collected from the Northern Bay of Safaga were measured. In addition to re- measuring of 61 fossil tests (29 males and 32 females) collected from the Late Pliocene Atef Abdelhamied Elattaar VII-129 sediments of the Red Sea coast of Egypt (Tables 1, 2, 3). All recent specimens studied in this work belong to the Institute of Geology and Paleontology, University of Tübingen, Germany. Shape: Test small to large in size, variable in shape, often elongate, smoothly rounded to elliptical in most specimens, especially in the smaller ones, rarely pentagonal to polygonal especially in the larger specimens; greatest height and width located at apical system. Margin somewhat thick, thicker anteriorly than posteriorly. Aboral surface somewhat with swollen thick margin, then sunken and depressed, and rising again gently towards apical system. Oral surface is flat to slightly concave toward the peristome, with well-developed food grooves, reaching about 65 % percent of the distance to the ambitus. In fossil tests, there are well-developed food grooves, reaching to 2/3 the distance to the test edge. Apical system: Raised, positioned centrally to slightly anteriorly, longer than wide, with five large and circular genital pores and five small ocular ones in a monobasal apical system; the anterior pair of genital pores closer together than the posterior ones. The madreporic pores are slightly deeply sunken and variable in shape from S, C, star, radial to meandering. The positioning of the genital pores with respect to the ocular pores within the apical system in the males is clearly different from that in the females (Figs. 9/A, B; 10/A, B).
Petals: Large, closing distally, extended almost to the thickened edge of test; maximum width lies at mid-length of petals or displaced slightly toward apical system; all petals mostly the same in width; petals I, III and V are the longest and mostly equal in length, whereas petals II & IV are the shortest. The number of pore pairs of petals I, III and V are mostly the same, become fewer in petals II & IV (Tables 2, 3). Pore pairs conjugated, lie diagonally to the length of petals; the outer pore slightly larger and more elongated than the inner one.
Peristome: Positioned centrally, as wide as long, varies in shape from ovoid to polygonal. The recent tests have a slightly larger (wider and longer) peristome than fossil ones. The average relative length and width of peristome relative to length of test are 0.104 and 0.105 respectively, in recent tests and 0.100 and 0.098 in fossil ones; also they are 0.103 and 0.104 respectively in females and 0.094 and 0.096 in males. (Tables 2, 3).
Periproct: Oral and transversely elongate; opening between first and second paired post- basicoronal interambulacral plates, close to the posterior margin, at distance 14% of the test length and 25% of the distance of peristome to posterior margin. The average relative width of periproct to its length is 1.23 percent. The recent tests have a slightly larger (wider and longer) periproct than the fossil ones; the average relative length and width of periproct relative to length of test are 0.075 and 0.092, respectively in recent tests and 0.073 and 0.085 in fossils ones, also these averages are 0.075 and 0.088 respectively in females and 0.070 and 0.085 in males (Tables 2, 3).
Discussion: The name Laganum depressum has been changed to Jacksonaster depressum by Durham (1966), Elattaar (2003), Kroh (2015) and in the present study. Genus Jacksonaster is easily distinguished from other closely similar genera, such as Peronella, Hupea and Laganum. It is easily distinguished from Peronella by having five gonopores (Peronella has only four), and the much longer petals distinguish it from Hupea. Jacksonaster is closely similar to Laganum. It differs by having more nearly marginal periproct, fewer basicoronal plates on the oral surface, more elongated first pair of post- basicoronal plates in interamb 5, in addition to the differences in the shape and the VII-130 Comparative Studies Of Recent And Fossil Echinoid Jacksonaster Depressum,… direction of elongation of periproct (transverse in Jacksonaster, elongated longitudinally in Laganum (Mortensen, 1948; Nisiyama, 1968). Several species belong to genus Jacksonaster: J. depressum (Agassiz, 1841) from Upper Miocene-Recent, Indo-West Pacific, J. fudsiyama (Doderlein, 1885) from Miocene- Recent, Indo West Pacific and J. pachycraspedum Nisiyama, 1968, from the Miocene of Japan. The first two species were listed by Mortensen (1948) under Laganum. J. fudsiyama is easily distinguished from J. depressum by having nonconjugate pore pairs, shorter oral ambulacral furrows and naked periproct (Mortensen, 1948; Nisiyama, 1968). J. pachycraspedum is distinguished from J. depressum by having much thicker margin and by the position of the periproct, which is much closer to the peristome than in J. depressum (Nisiyama, 1968). Mortensen (1948) established several varieties of J. depressum; alienum (Mortensen, 1948), delicatum (Mazzetti, 1894), tenue (Mortensen, 1948) and tonganense (L. Agassiz, 1841) in addition to the typical J. depressum. Kroh (2015) raised these varieties, to the subspecies level, i.e., Jacksonaster depressum alienum, J. depressum delicatum, J. depressum tenue, J. depressum tonganense, in addition to the typical J. depressum depressum. In Mortensen (1948, p. 308, 318), the varieties of recent forms of J. depressum are distinguished from each other as follows: Margin of test usually thickened in the typical form of J. depressum. Margin of test thin in J. depressum tenue. Test small, rather high, rising gradually direct from the margin, in J. depressum alienum. Oral ambulacral furrows short but distinct and the position of periproct more forward in J. depressum delicatum. Test low, not conically elevated and the periproct has more inward position in J. depressum tonganense. In Mortensen (op. cit., p. 308), the variety delicatum is restricted to the Red Sea and Western part of Indian Ocean. Nisiyama (1968, p.75), regarded J. depressum delicatum as a synonym of the typical J. depressum. The critical characters which led to the creation of this variety are: short oral ambulacral furrows and more forward position of periproct. Exactly the contrary in the present work, the periproct is located more forward in fossil tests than in recent ones, or the distance of periproct from the posterior margin is longer in fossil tests than recent ones (average percentage distance periproct from the posterior margin relative to the test length is 0.133 in recent tests, instead of 0.143 in the Pliocene fossil forms (Fig. 7A; Table 2). This is contrary to the opinion of Mortensen (1948, p. 318). He (op. cit) refers the forms of J. depressum in the Red Sea, which have a periproct in a more forward position to J. depressum delicatum. Based on this result, the J. depressum delicatum is a synonym of typical J. depressum. These differences between the typical J. depressum and the variety delicatum are regarded as intra-specific variation, side effect of ecological and paleoecological changes or sexual dimorphism, in the present study. Kier (1972, p. 95) compared Laganum tumidum and Jacksonaster depressum statistically, and presented a statistical analysis of 29 recent specimens of J. depressum coming from the British Museum (Natural History). Some statistical differences between the recent specimens of both Red Sea (our specimens) and those of Kier (1972) of J. depressum include width of test, length, width and pore pairs of petals, width of the peristome and periproct, and the distance from periproct to the posterior margin. Although the two last collections are recent specimens, our specimens have a wider test, longer petal I, shorter petal III, the same length of petal II, wider peristome and periproct, periproct lies more forward, more number of pore pairs in poriferous zones of petals than Atef Abdelhamied Elattaar VII-131 those of Kier (1972). These differences between the two recent collections (Table 1) of different localities reflect intra-specific variation and large influence by the surrounding environment. Table 1: Statistical differences between collection of Kier (1972) and present study of recent tests of J. depressum. Mean measurements of Jacksonaster depressum All measurements are in mm Collection of Red Sea specimens- Kier, 1972 Present study Length of test (L) 37.6 16.9 Percent width of L 81.1 91.0 Percent L Length of Petal I 23.0 30.0 Percent L Length of Petal II 27.0 27.0 Percent L Length of Petal III 31.8 29.0 Percent L width of Petal I 11.7 12.0 Percent L width of Petal II 11.8 11.4 Percent L width of Petal III 11.2 11.9
Percent L width of peristome 7.9 10.5 Percent L width of periproct 7.3 9.2 Percent L of distance from 11.1 13.3 periproct to the posterior margin Percent L of number of porepairs 1.13 1.4 in single poriferous zone of Petal I Percent L width width of Petal II 0.94 1.32 Percent L width width of Petal III 1.08 1.42
Ecology and paleoecology: J. depressum lives today in marine water, on sandy and fine sandy to muddy bottom sediments, from the intertidal zone down to a water depth of 85 m. (Mortensen, 1948; Kier, 1972; Dollfus & Roman, 1981; Nebelsick & Elattaar, 2009). It lives today in tropical and subtropical regions having an average salinity between 34.37‰ and 35.49‰, and temperature ranges between 23.28°C- 28.75°C (Kroh, 2015). J. depressum lives very shallowly buried in silty sands of the basinal areas of Safaga bay, whereas the dead, complete or fragmented tests are found in a wide variety of sediments ranging from poorly sorted medium sands from the edge of muddy basins adjacent to coral carpets within the basins in the muddy sand bottom facies and molluscan sedimentary facies. Both adults and juveniles of J. depressum tests are found in the same environment (Nebelsick, 1992b). The Safaga Bay is characterized by a large variability and rapid transition of twelve bottom sediments distinguished by Piller & Pervesler (1989); Coral reef, Coral carpet, Sand, Sand with coral patches, Sand with seagrass, Seagrass, Muddy sand, Mud, Rock bottom, Sand with macroids, Intertidal flat, and Mangrove. Eight sedimentary facies were also investigated by Piller & Mansour (1990, 1994), and Piller (1994): coralgal, mud, molluscan, operculina, soritid, terrigenous, compound grain, and halimeda (Nebelsick, 1992b, figs. 20, 24 and 29) within a relatively small area. The fossil specimens of J. depressum of this work were collected from a Pliocene bed characterized by low-angle planar cross-bedded sandstone with laminated heavy minerals concentrations of typical beach environment (Purser & Philobbos, 1993). This bed VII-132 Comparative Studies Of Recent And Fossil Echinoid Jacksonaster Depressum,… includes shallow water foraminifera characteristic of a near shore, well agitated environment and an inner neritic facies of 10 m depth (Selima, 1998). Out of twenty echinoid species collected from this bed (Elattaar, 2001), nine of them are living today. Elattaar (op. cit.) ascribes the presence of clastic sediment (sandstones) and fragments of abraded echinoid tests in this bed to a highly agitated shallow marine environment of about 10-15 m depth.
Stratigraphical, geographical and paleogeographical distribution: Miocene: Saudi Arabia, Zululand, Java and Fiji?. Pliocene: Egypt, Yanbo, Kenya, Zanzibar, east coast of Africa, Java, Fiji Islands, Japan. Pleistocene: Gulf of Suez and Egyptian coast of Red Sea, Farsan Islands, Kamaran, Somalia, Persian Gulf, Billiton Island, and Japan and the adjacent regions. Recent: tropical and subtropical parts of the Indo-West Pacific, none being found in the Atlantic or along American West Coast (Mortensen, 1948; Tortonese, 1951; Nisiyama, 1968; Clark & Rowe, 1971; Kier, 1972, Ali, 1985; Dollfus & Roman, 1981; Ghiold & Hoffman, 1986; Ghiold, 1989; Nebelsick, 1992a, b; Elattaar, 2001, 2003 and Kroh, 2015). ONTOGENETIC DEVELOPMENT Out of more than two hundred specimens of recent J. depressum collected from several localities, depths and bottom and sedimentary facies of the Northern Bay of Safaga, 177 specimens, in addition to 61 fossil one of Late Pliocene sediments of the Red Sea coast of Egypt were measured and analyzed statistically. Twenty-six characters were measured and examined statistically. Twenty-four scatter diagrams are plotted and discussed to diagnose the ontogenetic development of each morphological character of both recent and fossil tests during growth (Figs. 4-7). These diagrams reveal the following: 1- The relative width to length of test slightly decreases through growth. So that, there is a slight elongation in test during growth. (Figs. 4/A, B). 2- Percent length and width of all petals relative to the length of test slightly increases through growth (Figs. 4/C, D, E; 5/C, D, E). 3- Percent number of pore pairs of all petals relative to length of test decrease through growth (Figs. 4/F; 5/A, B). 4- Percent width and length of periproct relative to length of test slightly decreases through growth, so that the periproct relative to the length of test is larger in the small specimens. (Figs. 5/F; 6/A). 5- Percent width of periproct to its length relative to length of test is constant through growth, (Fig. 6/B). 6- Percent width and length of peristome relative to length of test decrease through growth, so that the peristome relative to the length of test is larger in the smaller specimens (Figs. 6/C, D). Figure 6B shows that the peristome is larger in recent tests than in fossil ones. 7- Percent width of peristome to its length relative to the length of test is constant through growth (Fig. 6/E). 8- Percent distance of periproct to peristome relative to length of test increases through growth (Fig. 6/F). The increasing of the relative distance between the periproct and the peristome through growth does not mean a migration of peristome forward or a migration of periproct backward, but it is due to the relative reduction in size of both the periproct and the peristome through growth.
Atef Abdelhamied Elattaar VII-133
9- Percent distance of periproct to the posterior margin relative to the length of test is constant through growth (Fig. 7/A). 10- Percent width and length of apical system relative to length of test decreases through growth, so that the apical system is relatively larger in the smaller specimens (Figs. 7/B, C). Figures 7/B, C shows that the apical system is wider and longer in fossil tests than recent one. 11- Percent width of apical system to its length relative to the length of test is constant through growth (Fig. 7/D). 12- Percent width of genital pore 2 relative to length of test slightly decreases through growth (Figs. 7/E, F).
There is a great similarity between the recent and fossil tests in the general trends of the ontogenetic development of J. depressum through growth in the morphological characters and statistical analysis (see figs .4/A, B; 5/C-F; 6/A, b, E, F; 7/A, D-F), whereas there are slight differences between them: Figure 6C shows that the peristome is wider in recent tests than fossil one. Figures 7/B, C show that the apical system is wider and longer in fossil tests than recent one.
STATISTICAL COMPARISON 1- Statistical comparison between fossil and recent tests of J. depressum: Some statistical differences and similarities between recent and fossil tests of J. depressum are recorded here (Table 2). These differences can be summarized as follows: 1- The recent tests of J. depressum reach length of up to 3 cm, whereas they reach up to 5.72 cm in the Pliocene fossil tests. 2- Average width relative to length of test is 0.91 in recent tests, but 0.88 in fossil ones. 3- Average length of petals I, II, III relative to length of test in recent specimens is 0.29, whereas, it is 0.28 in fossil ones. 4- The average number of pore pairs of petals I, II, III relative to length of test is 1.40, 1.32, and 1.42, respectively in each 1 mm length of test in recent specimens, whereas, it is 1.31, 1.18, and 1.30 in fossil ones, respectively. 5- The average width of petal II relative to length of test in both recent and fossil specimens is 0.114. 6- The average width of petals I, III relative to length of test in recent tests are 0.120 and 0.119, respectively, instead of 0.114, and 0.108 in fossil ones. 7- Average of length and width of periproct relative to length of test in recent individuals is 0.075 and 0.092 respectively, instead of 0.073 and 0.085 in fossil ones. 8- Average of length and width of peristome relative to length of test in recent individuals is 0.104 and 0.105 respectively, instead of 0.100 and 0.098 in fossil ones. 9- Average of distance of periproct to peristome relative to length of test in both recent and fossil individuals is 0.25. 10- Average distance of periproct to posterior margin relative to length of test is 0.133 in recent tests, instead of 0.143 in fossil one. The distance of periproct to posterior margin is longer in fossil tests than in recent one, that is because the recent tests have larger periproct and peristome, which expand backward while keeping a fixed distance between them. 11- Average of length and width of apical system relative to length of test is 0.072 and 0.069 in recent tests respectively, instead of 0.076 and 0.072 in fossil ones.
VII-134 Comparative Studies Of Recent And Fossil Echinoid Jacksonaster Depressum,…
12- Average width of genital pore 2 relative to length of test is 0.0076 in recent tests, instead of 0.0062 in fossil ones. Statistically, the recent specimens have wider tests, slightly wider petals, greater number of pore pairs in petals, larger periproct and peristome, wider genital pore 2 and smaller apical system than fossil ones.
A B 60 1.4 50 1.3 1.2 40 1.1 30 1.0 0.9 20 mm (W/L) 0.8 10 Width of Test (W) mm (W) Test of Width 0.7 Test of width Percent 0 0.6 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Length (L) mm Length (L) mm c D 0.5 0.5 0.4 0.4 0.3 0.3
II/L 0.2 0.2 I/L petal 0.1
Percent length of of length Percent 0.1
petal of length Percent 0.0 0.0 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Length (L) mm Length (L) mm
E F 0.5 5.0
0.4 4.0
0.3 3.0
III/L 0.2 2.0
0.1 I/L petal of pairs 1.0 Percent length of petal petal of length Percent 0.0 pore of number Percent 0.0 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Length (L) mm Length (L) mm
Fig. 4: Jacksonaster depressum (L. Agassiz). Scattergrams of recent and fossil tests showing the length of test (L) relative to: A- width of test (W); B- percent width of test (W/L); C- percent length of petal (I/L); D- percent length of petal (II/L); E- percent length of petal (III/L); F- percent number of pore pairs of petal (I/L).
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B A 4.0 4.0 Recent 3.0 Fossils 3.0
2.0 2.0
1.0 1.0
pairs of petal III/L
Percent number of pore pairs of petal II/L
Percent number of pore 0.0 0.0 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Lenght (L) mm Length (L) mm
c D 0.20 0.20
0.15 0.15
0.10 0.10 II/L
petal I/L 0.05 0.05
Percent width of Percent width of petal 0.00 0.00 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Length (L) mm Length (L) mm
E F 0.20 0.20
0.15 0.15
0.10 0.10
petal III/L
0.05 0.05 Percent width of
periproct Wpr/L Percent width of 0.00 0.00 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Length (L) mm Length (L) mm
Fig. 5: Jacksonaster depressum (L. Agassiz). Scattergrams of recent and fossil tests showing the length of test (L) relative to: A- percent number of pore pairs of petal (II/L); B- percent number of pore pairs of petal (III/L); C- percent width of petal (I/L); D- percent width of petal (II/L); E- percent width of petal (III/L); F- percent width of periproct (Wpr/L). VII-136 Comparative Studies Of Recent And Fossil Echinoid Jacksonaster Depressum,…
2-Statistical and morphological comparison between female and male of both recent and fossil tests of J. depressum: Sex type in the present study can be diagnosed only in 120 specimens of recent tests (25 females and 95 males) and 61 in fossil ones (32 females and 29 males). (Figs. 4-7; Tables 2, 3). The arrangement of both genital and ocular pores within the apical system as well as the size of the genital pores are important criteria for the determination of the gender of the individual tests of J. depressum. Thus, in females the gonopores are larger and placed further apart than in males (Figs. 9, 10). Furthermore, several other morphological parameters, particularly the length and width of test, distance of periproct to posterior margin, distance of periproct to peristome, length and width of apical system, length and width of periproct, length and width of peristome, length and width of petals, number of pore pairs in single poriferous zone of petals I, II, III, and width genital pore 2, have been analyzed statistically to detect possible additional sexual differences between males and females (Table 3). The statistical results are as follows: 1- Genital pore 2 is distinctly smaller than the other genital pores or even absent in the initial growth stage in male tests, whereas it is larger in female ones (Fig. 8/A, B). 2- Average of width of female and male tests relative to test length is 0.90 and 0.91 respectively. 3- Average length and width of petals I, II and III relative to test length, in both females and males are similar. 4- Average number of pore pairs of petals I, II and III relative to test length are 1.40, 1.29, 1.41, in females respectively and 1.35, 1.27, 1.36, in males, respectively. That indicates, the females have a greater number of pore pairs in petals than male ones. 5- Average length and width of periproct relative to test length is 0.075 and 0.088 in females and 0.070 and 0.085 in males, respectively. That indicates the periproct is larger in females than males. 6- Average length and width of peristome relative to test length is 0.103 and 0.104 in females, and 0.094 and 0.096 in males, respectively. That indicates the peristome is larger in females than males. 7- Average distance of periproct to peristome relative to test length is 0.250 in females and 0.256 in males. 8- Average distance of periproct to the posterior margin relative to test length is 0.138 in females and 0.135 in males. 9- Average length and width of apical system relative to test length is 0.081, 0.078 in females, and 0.070 and 0.067 in males, respectively. That indicates the apical system is larger in females than males. 10- Average width of genital pore 2 of the apical system relative to test length is 0.0075 in females and 0.0067 in males. That indicates the genital pore2 is larger in females than males. Statistically, the female tests have greater numbers of pore pairs in petals, larger periproct and peristome, larger apical system, and larger genital pore2.
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A B 0.20 2.5
2.0 0.15 1.5 0.10 Wpr/Lpr 1.0
0.05 of width Percent 0.5
periproct Lpr/L periproct
periproct to its length length its to periproct Percent length of of length Percent 0.00 0.0 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Length (L) mm Length (L) mm
c D 0.25 0.25
0.20 0.20
0.15 0.15
0.10 0.10
peristome Lps/L peristome Percent width of of width Percent peristome Wps/L peristome 0.05 0.05 of length Percent
0.00 0.00 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Length (L) mm Length (L) mm
E F 2.5 0.50
2.0 0.40
1.5 0.30
Wps/Lps 1.0 0.20 (Dpr-ps)/L
Percent width of of width Percent Recent Percent distance of of distance Percent peristome to its length length its to peristome 0.5 0.10
Fossils peristome to periproct
0.0 0.00 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Length (L) mm Length (L) mm
Fig. 6: Jacksonaster depressum (L. Agassiz). Scattergrams of recent and fossil tests showing the length of test (L) relative to: A- percent length of periproct (Lpr/L); B- percent width of periproct to its length (Wpr/Lpr); C- percent width of peristome (Wps/L); D- percent length of peristome (Lps/L); E- percent width of peristome to its length (Wps/Lps); F- percent distance of periproct to peristome (D.pr-ps/L). VII-138 Comparative Studies Of Recent And Fossil Echinoid Jacksonaster Depressum,…
A B 0.40 0.20
0.30 0.15
0.20 0.10
0.10 Wap/L system 0.05
margin(D.pr-pm)/L
Percent distance of of distance Percent
Percent width of apical width apical of Percent periproct to posterior posterior to periproct 0.00 0.00 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Lenght (L) mm Length (L) mm
c D 0.20 2.00
0.15 1.50
0.10 1.00
0.05 (Wap/Lap)/L 0.50
Percent length of of length Percent
system to its length length its to system
apical system Lap/L system apical Percent width of apical width apical of Percent 0.00 0.00 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Length (L) mm Length (L) mm
E F 0.60 0.03 0.50 0.40 0.02 0.30
0.20 0.01
Width of genital genital of Width (Wgp2)/L
pore 2 (Wgp2) mm (Wgp2) 2 pore 0.10
Recent 2 pore genital 0.00 Fossils width of Percent 0.00 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Length (L) mm Length (L) mm Fig. 7: Jacksonaster depressum (L. Agassiz). Scattergrams of recent and fossil tests showing the length of test (L) relative to: A- percent distance of periproct to posterior margin (D.pr-pm/L); B- percent width of apical system (Wap/L); C- percent length of apical system (Lap/L); D- percent width of apical system to its length (Wap/Lap); E- width of genital pore2 (Wgp2); F- percent width of genital pore 2 (Wgp2/L).
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SEXUAL DIMORPHISM IN Jacksonaster depressum (L. AGASSIZ, 1841) Sexual dimorphism in echinoids has attracted the attention of several authors (Kier (1967, 1968, 1969), David et al. (1988), Pearse & McClintock (1990), David & Mooi (1990), Schatt & Feral (1991), Kassab & Ahmed (1991), Elattaar (2003), Arab & Vaziri (2010) and others. The sexes can be distinguished on the basis of: (a) gonopores which are larger and placed further apart in females than males; (b) Females in some brooding species have depressed zones (pouches) varying both in shape and position on the test in which the young are brooded; in some clypeasteroids there is an anterior pair of oral interambulacral pouches; (c) Females usually grow considerably larger than males and, within a population of females significantly outnumber males (Kier, 1969; Philip & Foster, 1971; Smith, 1984; Neraudeau, 1993). Sexual dimorphism is found in species that brood their young (Smith, 1984). Elattaar (2003) studied the sexual dimorphism in Pliocene Jacksonaster depressum and he found that the apical system is larger and wider in females than males, gonopores are larger and placed further apart in females than males, and the tests are slightly wider in females than males. In our material, the genital pores of J. depressum are generally closed and invisible in tests smaller than 5.4 mm in length, which can then be considered as sexually immature juveniles individuals. Morphologically, the sexual dimorphism can be noticed in the apical system of male and female of both recent and fossil tests of J. depressum as follows: the apical system has different positions of the genital pores with respect to the ocular pores; both are placed in a single circle in males (Figs. 9/A3, A4), while the genital pores are placed far outside the ocular pores within the apical system in females (Figs. 9/ B3, B4). Statistically, the sexual dimorphism can be noticed in the biometrical variation between male and female tests of J. depressum; the female tests have a greater numbers of pore pairs in the petals, larger periproct and peristome, longer distance of periproct to the posterior margin, larger apical system and generally larger genital pores (especially genital pore 2) than the male (Figs. 9, 10; Table 3); delay growth occurs in genital pore 2 in male tests only (Fig. 8).
VII-140 Comparative Studies Of Recent And Fossil Echinoid Jacksonaster Depressum,…
Table 2: Statistical differences between recent and fossil tests of J. depressum.
Characters Recent 177 specimens Fossils 61 specimens (All measurements are in mm) Range average Range average Length of Test ( L ) mm 2.70-29.33 16.92 5.4-57.2 22.08 Width of Test ( W ) mm 2.35-26.60 15.54 4.8-50.3 19.20 W/L 0.81-0.97 0.91 0.82-0.95 0.88 I 1.25-9.54 5.97 2.9-18.5 7.02 Length of Petals (Lpt) II 1.25-8.60 5.50 2.6-15.0 6.20 III 1.30-9.40 5.90 2.54-17.0 6.84 I/L 0.22-0.36 0.30 0.24-0.35 0.29 Length of Petals (Lpt)/length of Test (L) II/L 0.20-0.32 0.27 0.22-0.29 0.26 III/L 0.24-0.35 0.29 0.23-0.33 0.28 Number of pore pairs in single I 11 - 40 26.8 16-59 30.04 poriferous zone of Petal (Npp) II 11 - 38 25.7 14-57 27.00 III 12 - 42 27.3 16-60 29.74 Number of pore pairs in single I/L 1.02-2.03 1.40 0.97-1.76 1.31 poriferous zone of Petal (Npp) II/L 0.95-1.79 1.32 0.87-1.67 1.18 /length of Test (L) III/L 0.95-2.21 1.42 0.94-1.76 1.30 I 0.75-3.50 2.34 1.5-5.2 2.64 Width of Petal (Wpt) II 0.70-3.30 2.23 1.35-5.3 2.66 III 0.70-3.50 2.34 1.3-4.7 2.49 I/L 0.094-0.145 0.120 0.079-0.152 0.114 Width of Petal (Wpt)/length of Test (L) II/L 0.083-0.141 0.114 0.084-0.148 0.114 III/L 0.096-0.149 0.119 0.074-0.153 0.108 Length of periproct (Lpr) Lpr 0.25-2.05 1.21 0.50-2.40 1.52 Length of periproct (Lpr)/length of test (L) Lpr/L 0.049-0.159 0.075 0.039-0.104 0.073 Width of periproct (Wpr) Wpr 0.35-2.60 1.50 0.55-3.20 1.79 Width of periproct (Wpr)/length of test (L) Wpr/L 0.068-0.136 0.092 0.050-0.127 0.085 Width/Length of periproct Wpr/Lpr 0.92-1.56 1.250 0.89-1.40 1.177 Length of peristome (Lps) Lps 0.55-2.40 1.74 0.80-3.00 1.99 Length of peristome (Lps)/length of test (L) Lps/L 0.071-0.206 0.104 0.051-0.157 0.100 Width of peristome (Wps) Wps 0.50-2.50 1.82 0.75-2.90 2.01 Width of peristome (Wps)/length of test (L) Wps/L 0.067-0.237 0.105 0.050-0.164 0.098 Width/length of peristome Wps/Lps 0.90-2.55 1.05 0.80-1.17 1.00 Distance periproct to peristome (D.pr-ps) D.pr-ps 0.45-8.20 4.64 1.05-18.90 5.81 Distance periproct to peristome (D.pr-ps)/L 0.15-0.30 0.25 0.19-0.34 0.25 (D.pr-ps) /length of test (L) Distance periproct to posterior D.pr-pm 0.35-4.70 2.35 0.85-7.30 3.12 margin (D.pr-pm) Distance periproct to posterior (D.pr-pm)/L 0.09-0.17 0.133 0.109-0.169 0.143 margin/length of test (L) Length of apical system (Las) Las 0.80-2.10 1.40 1.25-2.81 1.83 Length of apical system (Las)/ Las/L 0.046-0.147 0.072 0.041-0.135 0.076 length of test (L) Width of apical system (Was) Was 0.80-2.10 1.38 1.10-3.10 1.75 Width of apical system (Was)/ Was/L 0.046-0.137 0.069 0.036-0.123 0.072 length of test (L) Width of genital pore 2 (Wgp) Wgp2 0.020-0.240 0.153 0.100-0.330 0.155 Width of genital pore 2 (Wgp)/ Wgp2/L 0.0046-0.0117 0.0076 0.0036-0.0120 0.0062 length of test (L)
Atef Abdelhamied Elattaar VII-141
Table 3: Statistical differences between males and females of both recent and fossil tests of J. depressum. Characters Recent and Fossil specimens (All measurements are in mm) Females 57 specimens Males 124 specimens Range average Range average Length of Test ( L ) mm 5.40-57.20 19.22 5.43-55.70 21.45 Width of Test ( W ) mm 4.80-50.30 17.27 5.05-45.40 19.35 W/L 0.82-0.97 0.90 0.82-0.96 0.91 I 2.30-16.80 6.03 1.25-18.50 6.56 Length of Petals (Lpt) II 2.10-15.00 5.54 1.25-14.50 5.92 III 2.40-16.10 6.01 1.30-17.00 6.39 I/L 0.24-0.35 0.29 0.23-0.36 0.30 Length of Petals (Lpt)/length of Test (L) II/L 0.21-0.32 0.27 0.22-0.32 0.27 III/L 0.23-0.35 0.29 0.24-0.34 0.29 Number of pore pairs in single I 16-59 27.60 12-59 28.38 poriferous zone of Petal (Npp) II 14-57 25.44 11-50 26.89 III 16-60 27.63 12-60 28.68 Number of pore pairs in single I/L 1.03-1.86 1.40 0.97-2.21 1.35 poriferous zone of Petal (Npp) II/L 0.97-1.73 1.29 0.87-1.82 1.27 /length of Test (L) III/L 1.05-1.93 1.41 0.94-2.21 1.36 I 1.15-5.20 2.39 0.75-4.40 2.49 Width of Petal (Wpt) II 1.10-5.30 2.30 0.70-4.70 2.43 III 1.10-4.70 2.32 0.70-4.10 2.45 I/L 0.09-0.15 0.12 0.08-0.16 0.12 Width of Petal (Wpt)/length of Test (L) II/L 0.08-0.15 0.11 0.08-0.14 0.11 III/L 0.08-0.15 0.12 0.07-0.15 0.12 Length of periproct (Lpr) Lpr 0.50-2.40 1.35 0.55-2.30 1.47 Length of periproct (Lpr)/length of test (L) Lpr/L 0.042-0.104 0.075 0.04-0.10 0.070 Width of periproct (Wpr) Wpr 0.55-3.20 1.63 0.60-2.80 1.79 Width of periproct (Wpr)/length of test (L) Wpr/L 0.06-0.13 0.088 0.05-0.13 0.085 Width/Length of periproct Wpr/Lpr 0.89-1.54 1.20 0.92-1.55 1.23 Length of peristome (Lps) Lps 0.80-2.90 1.82 1.00-3.00 1.94 Length of peristome (Lps)/length of test (L) Lps/L 0.05-0.16 0.103 0.05-0.17 0.094 Width of peristome (Wps) Wps 0.75-2.90 1.87 0.80-2.80 1.99 Width of peristome (Wps)/length of test (L) Wps/L 0.051-0.164 0.104 0.05-0.13 0.096 Width/length of peristome Wps/Lps 0.88-1.17 1.02 0.80-1.23 1.03 Distance periproct to peristome (D.pr-ps) D.pr-ps 1.05-18.40 4.91 1.35-18.90 5.60 Distance periproct to peristome (D.pr-ps)/L 0.19-0.32 0.250 0.19-0.34 0.256 (D.pr-ps) /length of test (L) Distance periproct to posterior D.pr-pm 0.85-7.30 2.62 0.65-7.10 2.90 margin (D.pr-pm) Distance periproct to posterior (D.pr-pm)/L 0.109-0.169 0.138 0.101-0.169 0.135 margin/length of test (L) Length of apical system (Las) Las 1.10-2.81 1.65 0.80-2.40 1.47 Length of apical system (Las)/ Las/L 0.049-0.135 0.081 0.041-0.147 0.070 length of test (L) Width of apical system (Was) Was 1.00-3.10 1.61 0.80-2.30 1.42 Width of apical system (Was)/ Was/L 0.054-0.123 0.078 0.036-0.128 0.067 length of Test (L) Width/Length of apical system Was/Las 0.85-1.14 0.97 0.72-1.21 0.97 Width of genital pore 2 (Wgp 2) Wgp 2 0.080-0.330 0.163 0.050-0.210 0.147 Width of genital pore (Wgp 2)/ Wgp 2/L 0.0044-0.0120 0.0075 0.0036-0.0105 0.0067 length of test (L) VII-142 Comparative Studies Of Recent And Fossil Echinoid Jacksonaster Depressum,…
Fig. 8: Recent small tests of J. depressum. A, B: Close-up of (arrowed) apical system of small sizes of dead tests; A: Delay growth in genital pore 2 in male. B: Incorrect position of genital pore 5 (displaced to the right) in female.
Genital Pore
Ocular Pore
A 4 B 4 Fig. 9: Sexual dimorphism in the apical system of recent dead J. depressum. A: male. B: female. A1, B1: oral surfaces; A2, B2: aboral surfaces of the same; A3, B3: close-up of apical system of the same; A4, B4: explanatory models showing positions of both genital and ocular pores relative to each other within the apical system; they are placed together in a single circle in male test (A3, A4), and the genital pores are placed far outside the ocular pores in females (B3, B4). Atef Abdelhamied Elattaar VII-143
Genital Pore
Ocular Pore
A 4 B 4 Fig. 10: Sexual dimorphism in the apical system of fossil Jacksonaster depressum. A: male. B: female. A1, B1: oral surfaces; A2, B2: aboral surfaces of the same; A3, B3: close-up of apical system of the same; A4, B4: explanatory models showing positions of both genital and ocular pores relative to each other within apical system; they are placed together in a single circle in male test (A3, A4), and the genital pores are placed far outside the ocular pores in females (B3, B4).
VII-144 Comparative Studies Of Recent And Fossil Echinoid Jacksonaster Depressum,…
EXPLANATION OF THE DIFFERENCES BETWEEN RECENT AND FOSSIL TESTS AND MALES AND FEMALES OF J. DEPRESSUM
Two questions impose themselves, and require answer are; the first question is: why do recent forms of J. depressum have a smaller and wider tests, slightly wider petals, greater number of pores pairs in petals, larger periproct and peristome, shorter distance of periproct to posterior margin, wider genital pore2 and smaller apical system than fossil ones ?. The second question is; why do female tests have a greater numbers of pore pairs in petals, larger periproct and peristome, larger apical system and generally larger genital pores2 than males?. To the second question, the answer is as follows: Generally, the growth rate in the echinoids is affected by a variety of different factors including temperature, reproductive state, availability and type of food, and weather. Seasonal variation in these factors imparts annual cyclicity in growth rate (Smith 1984). The non-locomotor podia on the aboral surface of clypeasteroids are believed to serve a respiratory function (Hyman, 1955). Nichols (1959) and Fenner (1973) presented the histology of the respiratory podia (petaloids) of the clypeastroid Echinocyamus. Increasing the number of pore pairs in petals means increasing the respiratory tube feet to compensate shortage of oxygen. The lack of food from plants and algae leads to shortage of oxygen. It is believed that the females of J. depressum digged deeper into the sediments than the males in order to brood their young in a safer environment, away from predators and, hence, were more exposed to oxygen deficiency; they then had to increase the number of pore pairs in the petals in order to overcome this shortage in oxygen. When the individuals live deeper in the sediments they change somewhat their natural habitat, and in order to get enough food, they have to swallow a greater amount of sediments; as a consequence the females had to increase the size of the peristome; furthermore, in order to get rid of the extra amount of sediments passing through the gut they had to increase also the size of the periproct. Theses J. depressum reach length of up to 3 cm in the recent Sea, whereas, it reach up to 5.72 cm in the Pliocene Paleoenvironment. The availability of sufficient oxygen and food in the paleoenvironment of the Red Sea during the Pliocene Epoch, led to grow to a larger size. Oxygen and food shortages forced the recent J. depressum to expand the mouth (peristome) and anus (periproct) and increase respiratory devices (pore pairs) in order to adapt to the surrounding environment.
ACKNOWLEDGEMENTS All the appreciation and thanks to Prof. J. Nebelsick (Institute for Geosciences, Tübingen University, Germany) for helping me to get the recent samples of J. depressum of this study from the Institute for Geosciences, Tübingen University, Germany. REFERENCES
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