Micropaleontology 2

By Omar Mohamed • Micropaleontology (also sometimes spelled as micropalaeontology) is the branch of palaeontology that studies microfossils • Microfossils are fossils generally not larger than four millimeters, and commonly smaller than one millimeter, the study of which requires the use of light or electron microscopy. Fossils which can be studied with the naked eye or low- powered magnification, such as a hand lens, are referred to as macrofossils

• Microfossils are the remains of unicellular, multicellular micro-organisms and the dissociated elements and skeletal fragments of macro-organisms. • They consist of these types: Foraminifera, Ostracods, Coccolithophora, Diatoms, Radiolaria, Conodonts, Spores, Pollen grains and Dinoflagellates. • The oldest known and most familiar fossils, are from cyanobacteria in Archaean rocks. • Most are protists – unicellular plants and animals, some are multicellular or microscopic parts of macroscopic forms. • These are calcareous, siliceous, organic-walled and phosphatic in test composition. • Their morphology as well as genetic characters are different. • Thus, microfossils, unlike other kinds of fossils, are not grouped according to their relationships to one another, but only because of their generally small size and methods of study. For example, fossils of bacteria, foraminifera, diatoms, very small invertebrate shells or skeletons, pollen, and tiny bones and teeth of large vertebrates, among others, can be called microfossils. But it is an unnatural grouping. Benthic Foraminifera Planktonic Foraminifera Ostracods Click for more photos Click for more photos

Diatom Radiolaria Dinoflagellate Coccolithophora (Arachnoidiscus sp.) (Lamprocyclas sp.) (Cerodinium sp.) Spores and pollens (Emiliania huxleyi)

Conodonts Chirognathus & Erismodus • They are found in all the ecosystems in water (marine, river, estuarine) and on land • They live in shallow marine, bathyal and abyssal depths • Their minute size, abundant occurrence and wide geographic distribution in sediments of all ages and in almost every marine environment make them useful • They range from the Precambrian to the Recent • Some are planktic living in top 200 m making them useful in monitoring sea surface temperature, e.g. foraminifera, diatoms, radiolaria, coccoliths • Some are benthic (vagile/sessile) – foraminifera, bryozoa, ostracoda, diatoms • Some have both benthic and planktic phases in their reproduction • Spores and pollens derived from land plants, are strongly climate dependent • A small amount of sediment sample can give rise to thousands of specimens of foraminifera Importance:

• Microfossils are perhaps the most important group of all fossils, they are extremely useful in age-dating, correlation and paleoenvironmental reconstruction, all important in the oil, mining, engineering, and environmental industries, as well as in general geology • Billions of dollars have been made on the basis of microfossil studies • Because they usually occur in huge numbers in all kinds of sedimentary rocks, they are the most abundant and most easily accessible fossils • Indeed, some very thick rock layers are made entirely of microfossils. The pyramids of Egypt are made of sedimentary rocks, for example, that consist of the shells of foraminifera, a major microfossil group • Microfossils can also be very useful in teaching science at all levels. Students are commonly fascinated by things they cannot see with their naked eyes, especially when the objects are beautiful or interesting in their own right. • Processing of micropaleontological samples is usually easy and safe enough for students to do themselves, or at least to watch. • Although plants and animals are the most obvious life around us today, they are not the most numerous nor the most important contributors of microfossils. • Bacteria (prokaryotes) and protists far outnumber them, live in more diverse habitats, and leave a greater diversity of microfossils. • Today these organisms live from Antarctic ice deserts to steaming volcanic hot springs, and from the highest mountains to the deepest sea. Some cause diseases, such as malaria which infects 350-400 million people today; others are useful to humans. • Most simply live their lives unknown to us but contributing enormously to our well being through the production of oxygen, the degradation of waste materials, recycling of nutrients, production of food, and a multitude of other functions, some of which take place in our own bodies. Fungi, another group in modern environments that both benefit and plague humans, have a long, but mostly unstudied, microfossil record.

Applied Micropaleontology

Microfossils in Petroleum Exploration

• Paleontology for exploration • Paleontology continues to play a valuable role in petroleum industry exploration and production. Even as technological changes sweep the industry, integrating paleontologic data with these new technologies, such as 3-D seismic, has become a standard practice. • Along with seismic reflection profiles and well logs, paleontology is a key tool in correlation. It is the most useful tool for constructing age models necessary for all time-dependent modeling, such as thermal maturation of potential hydrocarbon source rocks. And paleontology helps characterize depositional environments for predicting the distribution and quality of reservoir, seal and source rocks. • Paleontologists must be part of any exploration team. Testing multiple hypotheses using all data, including paleontologic data, results in a significantly better geologic model and prevents “transom paleontology,” in which samples are sent to the paleontologists who must then generate reports without critical discussion and consideration of alternative interpretations. This isolation of critical thinking is particularly acute when geologists and geophysicists using the data are geographically isolated from paleontologic consultants. • Biostratigraphy, the study of the distribution of fossils in the stratigraphic record, is a valuable and inexpensive correlation tool, even in today’s era of 3-D seismic and advanced suites of well logs. The 1999 cost of the biostratigraphy group at Exxon, for example, was about equal to 10 days of drilling on an ultra-deepwater prospect.

The advantages of using microfossils for subsurface biostratigraphy

• Small Size • Abundance • Wide geographic distribution

Review of Techniques

• Correlation • Age determination • Unconformity Identification • Application to sequence stratigraphy analysis • Sequence stratigraphy models • Sequence analysis of well • Characterization of formations (“fingerprinting”) • Palaeoenvironmental interpretation Role of Micropaleontology in hydrocarbon exploration and development programmes

Requirements for hydrocarbon accumulation: • Reservoir: biostratigraphy + sedimentology • Trap: biostratigraphy + seismic mapping • Seal: lithostratigraphy + biostratigraphy • Source: geochemistry + biostratigraphy Appraisal of discoveries • Well correlation • Reservoir distribution and reserve estimation • Trap evaluation How can • Field development Micropaleontology Pitfalls in biostratigraphic correlation help to find oil? • Factors affecting data quality • Reworking and caving • Age Interpretations • Taxonomic nomenclature • Preparation techniques • Microfossil and zonal identification • Paleoenvironmental controls • Practical correlation and biostratigraphy Marine Environments Main Microfossil Groups Classified on the basis of test composition A. Calcareous Microfossils 1. Foraminifera (Cambrian to Recent) 2. Calcareous Nannoplanktons (Jurassic to Recent) 3. Ostracodes (Cambrian to Recent) 4. Pteropods (Late Cretaceous to Recent) 5. Calpionellids (Late Jurassic to Early Cretaceous) 6. Calcareous Algae (Precambrian to Recent) 7. Bryozoa B. Siliceous Microfossils 8. Radiolaria (Cambrian to Recent) 9. Marine Diatoms (Late Cretaceous to Recent) 10. Silicoflagellates (Late Cretaceous to Recent) and Ebridians (Tertiary to Recent) C. Phosphatic Microfossils 11. Conodonts and other phosphatic microfossils (Cambrian to Triassic) D. Organic-Walled Microfossils 12. Dinoflagellates (Silurian to Recent), Acritarchs (Precambrian to Recent) and Tasmanitids (Cambrian to Tertiary) 13. Spores and Pollens in the Marine realm 14. Chitinozoa (Ordovician to Devonian) Micropaleontology 2 • We will study the following: • 1. Palynology – Dinoflagellates – Spores and Pollen Grains • 2. Calcareous Nannoplankton • 3. Conodonts • 4. Ostracoda • Some nots on Sequence stratigraphy • Part 1 Applied micropalaeontology 1 • Chapter 1 Introduction 3 • Chapter 3 Microfossils in stratigraphy 16 • Chapter 4 Microfossils, stable isotopes and ocean-atmosphere history 25 • Part 3 Organic-walled microfossils 69 • Chapter 9 Acritarchs and prasinophytes 71 • Chapter 10 Dinoflagellates and ebridians 80 • Chapter 13 Spores and pollen 104 • Part 4 Inorganic-walled microfossils 127 • Chapter 14 Calcareous nannoplankton: coccolithophores and discoasters 129 • Chapter 20 Ostracods 219 • Chapter 21 Conodonts 249