UNIVERSITY OF CALGARY SPRING 2010

GLGY 209-20 INTRODUCTION TO GEOLOGY I

GEOLOGIC TIME SCALE

There are four eons:

•PHANEROZOIC (visible life forms);

•PROTEROZIC (early life forms);

•ARCHEAN (oldest rocks);

•HADEAN (no rock record).

Evaluation of the Geological Time

Studying the Biblical chronology, the Irish Bishop James Ussher concluded in 1654 that the Earth has been created in the year 4,004 BC.

Georges Louis Leclerc, Comte De Buffon estimated the age of the Earth at about 75,000 years. His major work, Les Epoques de la Nature has been published in 1778.

Radioactive Decay

Some of the isotopes are stable, other not. An unstable isotope nucleus can be

transformed spontaneously into an isotope with a stable nucleus configuration.

This process is known as radioactive decay.

Radioactive Decay Series

Radioactive decay series between Uranium 238 and Lead 206. There are eight alpha and six beta decay steps.

Half-Life

The half-life of a radioactive element represents the time it takes for one half of the atoms of the original unstable parent element to decay to atoms of a new and more stable daughter element.

Half-Life principle

Half-time Resolution

GEOLOGIC TIME SCALE

Explaining the fossil record. Theory of evolution

Living World Hierarchy

Karl Linnaeus yielded the first hierarchy of the living world.

In the 7th edition of his book ‘Systema Naturae’ (Lat.: Systema Naturae: Creationis telluris est gloria Dei ex opere Naturae per Hominem solum ) Linnaeus postulated that species are real & unchangeable entities.

Hierarchy as Proposed by Linnaeus

Linnaeus belief: “… if God created the World it is possible to understand God’s wisdom by studying his creation.”

His best known student Daniel Solander was Captain James Cook’s naturalist in his voyages around the world.

Kingdom > Class > Order > Genus > Species

Grouping Animals by Similarity

Species Names _ Binominal

Linnaeus established the first system of species naming, which is defined as binominal:

Name of the Genus + Name of the Species

Linnaeus Change of Opinions Linnaeus abandoned his

principle of the unchangeable species. He brought the argument of the plant hybridization.

The process of creating new species was not regarded as open-ended. He believed that all the new occurred species came from the primae species, namely those from the Garden of Eden.

Cuvier’s Catastrophism

Baron Georges Leopold Cuvier (1769-1832) is often remembered for the establishment of the comparative anatomy and vertebrate paleontology as sciences.

Vertical section of the cavern at Gaylenreuth in Franconia, from George Cuvier's Essay on the Theory of the Earth.

Cuvier’s Data & Interpretations

Cuvier discovered remains of quadrupeds to species now living in the Quaternary sediments of the Paris Basin. At lower levels are present extinct species of

elephant, hippopotamus, rhinoceros or mastodon or close relatives of those genera.

Still lower in the stratigraphic column, the bone debris belongs to the extant mammal genera and they are quite rare at the base of the Tertiary deposits.

Cuvier concluded that during the history whole populations of quadrupeds have been exterminated.

He also observed that the strata with terrestrial mammal bones are sandwiched between strata bearing typical marine fossils.

Therefore, recurrent flooding by the sea must have been an agency involved in the successive extinction.

Jean-Baptiste Lamarck (1744-1829)

In 1861 Darwin wrote about Lamarck: “Lamarck was the first man

whose conclusions on the subject excited much attention. This justly celebrated naturalist first published his views in 1801. . . he first did the eminent service of arousing attention to the probability of all changes in the organic, as well as in the inorganic world, being the result of law, and not of miraculous interposition”.

Intraspecific Variability

J.-B. Lamarck had to face a formidable challenge by studying invertebrate fossils: the large number of specimens of the same species.

Practically, he had to explain and to transform in systematic language the morphologic variability of various species.

It Started with a Voyage

Charles Darwin was a young naturalist at the board of H.M.S. Beagle in a five year voyage around the world.

His extensive observations on the South American mammal faunas as well as from the faunas of the Pacific Islands (distribution of living species on isolated islands) could be best observed by the heretical idea of transmutation.

First Hand Biological Data Darwin made systematical observations on the Galapagos Island

finches noting that “…one might really fancy that …one species had been taken and modified for different ends”.

First Hand Geological Interpretations

Darwin made quite accurate interpretations about the atol formation.

A New Definition for Evolution Evolution can be shortly described as

“descent with modification”.

The First Release

The most important work of Darwin has been published in 1859.

Four editions have been published during his lifetime.

Alfred R. Wallace

Wallace is nowadays regarded as a coauthor of the evolutionary theory.

In 1855 he published an article about the evolution of species from one another.

He lacked Darwin’s strong arguments.

EMERGENCE OF LIFE ON EARTH

CHON

The dominant elements in the life forms today are: Carbon; Hydrogen; Oxygen; Nitrogen.

Sulfur and phosphorus are present in smaller amounts.

Earth’s early atmosphere

Alexandr Ivanovic Oparin (1896-1980) postulated that it is possible that CHON molecules could have been formed before life begun to give rise to the first cells.

A starting point of Oparin’s model was the fact that the plant cells are too complex to have been formed without a long process of inorganic evolution.

Oparin model was one in which the Earth’s original atmosphere was a reducing one, without much free molecular oxygen.

CHON molecules could be accumulated in a reducing atmosphere.

“Primordial soup” was not alive!

Earth’s early atmosphere

Isua Supercrustal Group

The Greenland Isua Supercrustal Group contains some of the oldest sedimentary rocks on Earth (3.8 – 3.7 billion years).

Rare oxides and carbonates, which do not form layers!

Graphite levels indicate organic origin.

Experimental confirmation

Miller and Urey experiment (1953) demonstrated the possibility that simple elements can react chemically to form simple organic CHON molecules.

They obtained seven aminoacids (e.g., glycine, alanine, etc) – organic compounds.

Miller and Urey experiment

They started their experiment considering that all the gases in the Earth’s primordial atmosphere were hydrogenated: H2, CH4, NH3, H2O vapors.

Energy was produced by lightning and ultraviolet radiation.

Polymerization Monomers were not enough.

Examination of the simplest life forms on the modern Earth, mycoplasmas, present a part of DNA and several hundreds of complex molecules. Mycoplasmas are parasitic.

An ordinary bacterium has thousand of complex molecules, including approximately 500 kinds of RNA.

Polymerization

Polymerization Combining the simple CHON molecules

into larger molecules would result in the formation of polymers, a necessary step in the development of the life forms on Earth.

Example: Cellulose (carbohydrate polymer) is formed by repeating the glucose monomeric unit (C6H12O6).

MOLECULES DO NOT FOSSILIZE.

Metabolism Simple “alive” organisms existed before

they were packed into cells, which are extremely complex structures.

The metabolism of the primordial organisms was probably very simple: fermentation (more energy is required than it is produced) or anoxygenic photosynthesis (copious amount of glucose are produced but the process depends of the hydrogen sources, which are available only locally).

Metabolism

Other kinds of metabolism

Aerobic photoautotrophy (oxygenic photosynthesis) – higher algae and plants; huge amounts of hydrogen are produced.

Aerobic heterotrophy (respiration) – characteristic to the animals (much more energy is consumed than produced.

Hadean times conditions

Craters at the surface of the Moon, Mercury, Venus, demonstrate the existence of a severe meteoritic bombardment in the early history of the Earth.

Hadean times conditions

The early oceans at the Earth’s surface were probably boiled repeatedly during the primordial meteorite bombardment.

The craters on the terrestrial planets can be used for stratigraphy purposes.

Nature of data

Data from fossils.

Data from mineralogical composition of the rocks.

Chemical fossils as results of the organic activity.

The oldest life forms

Stromatolites - generalities

The first stromatolites were discovered in the New York State, in the surroundings of Saratoga, in the early 1880s.

The name of stromatolites was given long after.

Originally they were named Cryptozoon.

Organic nature of the stromatolites

The organic nature of the stromatolites was demonstrated long time after based on the discoveries from southern Ontario.

Cryptozoon structures were discovered in a point known as Schreiber Beach by Stanley A. Tyler (University of Wisconsin).

Schreiber Beach Cryptozoon

The first Precambrian fossils

Eosphaera

The living stromatolites

Living stromatolites were discovered in a salty lagoon of western Australia – the Shark Bay.

Fossil & living stromatolites

A stromatolite is best studied in polished sections.

Stromatolite morphology

Stromatolite characteristics

Accretionary organo-sedimentary structures;

Thinly layered, megascopic, calcareous;

Produced by the activity of mat-building communities of mucilage secreting microorganisms;

Consist mainly of photoautotrophic prokaryotes (e.g., cyanobacteria)

Stromatolite persistence

Stromatolite fossil record

Fig Tree Formation of South Africa 3.1 to 3.5 billion years old.

Just like in the Gunflint Formation of Ontario, the fossils were found in stromatolitic structures.

Stromatolite evolution

Stromatolites occurred in the Archean times. At the beginning of their evolution the distribution is patchy.

They are ubiquitous in the Proterozoic, when the lived in all the environments: streams and rivers, lakes and ponds, seas and oceans.

Major reduction in frequency at the Precambrian/Cambrian boundary.

Stromatolite evolution

Stromatolites represent the living witness of the evolution’s evolution.

Precambrian times: if not broken, don’t fix it!

Cambrian to Quaternary: extraordinary diverse morphological changes.

Isolated cells

Early Archean of western Australia (Pilbara Craton).

Apex Chert is a lithological unit in a volcano-sedimentary formation.

Earliest cyanobacteria debris.

Apex Chert cyanobacteria

Some of the cells from the Apex Chert show folded filament with cell-like structures made of carbon.

Similar to modern iron bacteria.

Strelley Pool Chert cyanobacteria

The chain-like structure is similar to that of the modern purple bacteria.

Earth’s rusting

Approximately 2.0 billion years ago a major phenomenon happened on Earth.

Oxides formed in vast amounts (Banded Iron Formation = BIF).

They document a huge increase in the molecular oxygen in the Earth’s atmosphere.

Prokaryote diversification

The first Precambrian fossils were discovered in the Gunflint Formation of southern Ontario.

Ex: Gunflintia and Huronipora.

Prokaryote

Eukaryote cells are much more complex than the prokaryotes.

First eukaryotes

The first eukaryotes were discovered in the Bitter Springs Formation of Australia.

Age: approximately 770 m. y.

Cell arrangement suggests meiotic cell division.

Chemical fossils: 1.8 billion years.

Eukaryotes - examples

Bangiomorpha

Filamentous thallus, similar to those of the modern red algae;

Primitive holdfast attached to the seafloor, allowing the alga to rise upward towards the sunlight.

Age: ~ 1.2 billion years; ST: Proterozoic-Quaternary.

Eukaryotes - examples

Torridonophycus

Algal microstructures escaping from a bag-like structure (acritarch), which helped them to survive the dry climate, cold, etc).

Clorophyte. Age: ~ 0.9 billion years. ST: Upper Proterozoic-

Quaternary.

Eukaryotes - examples

Melanocyrillium

Shows similarities with the modern group of testate amoebas. For this reasons it is included among the earliest animals.

Organic, sometimes with agglutinated particles.

Age: ~ 0.8-0.9 billion years.

ST: Upper Proterozoic-Quaternary.

Kingdoms 1. Bacteria (Prokaryotae, Procaryotae, Monera);

prokaryotic cells (lacking a nucleus and nuclear membrane).

2. Protoctista (Protista); single eukaryotic cell (with nucleus and nuclear membrane); include foraminifera and radiolaria.

3. Animalia (Animals); heterotrophic multicellular eukaryotes (phyla subdivided by cell organization level, symmetry, feeding structures, segmentation, presence of vertebrae or notochord…).

4. Plantae (Plants); autotrophic multicellular eukaryotes (algae or aquatic plants and tracheophytes or vascular terrestrial plants).

5. Fungi; (as endoliths in fossil record) heterotrophic eukaryotes with chitinous resistant fungal spores.

Ediacara Hills (southern Australia).

Precambrian Time Scale

Ediacara Animals

Animals imprints from Ediacara Hills are all metazoans. They document the transition from the unicellular to multicellular forms of life.

Ediacaran animals generally present a simple structure, being soft-bodied animals (there is not a trace of skeleton).

They are worm-like animals (flatworms, segmented worms), coelenterates and some totally unknown types.

Ediacara dominant fossils Parvancorina

Size: 1-2.5 cm; Shield-shaped front end; Central axis and weak

traces of segmentation; Up to 10 pairs of possible

appendages with distinct set of growth stages;

Interesting orientation: head shield(?) facing the direction of water current (feeding strategy?).

Ediacara dominant fossils

Tribrachidium Unknown affinities; 2-5 cm; Disk-shaped with

three raised arms and raised borders;

Triradial symmetry.

Ediacara dominant fossils

Dickinsonia 1-100 cm; Segmented, head,

tail (segmented worm?);

No gut or other internal organs have been found;

The tail(?) occurs only in the mature specimens.

Ediacara dominant fossils

Charnia 0.15-2 m; Strong similarities

with the modern sea-pens;

Bilateral symmetry; Feather-shaped

frond with a series of side branches.

Ediacaran Animals Today?

Living sea-pens from offshore NW Australia.

Ediacara dominant fossils

Spriggina Case

A worm-like animal of the Ediacara fauna presents an extraordinary feature.

In the (probably!) anterior part of its body there is a portion which apparently presents a thickened tissue.

First evidence of cephalization. See also Parvancorina.

Spriggina Case

Approximately 3 cm long. Australia, then Russia.

Controversial Way of Life

Seilacher & McMenamin suggested that the animals of Ediacara all lived in symbiotic relationships with algae in their tissues as the modern corals do today.

Practically the animals of Ediacara-type could get nutrients from the activity of the photosynthetic symbiotic algae.

Vendoza Controversy

Seilacher & McMenamin emphasized the dissimilarities between Ediacara-type and modern organisms.

They also proposed to include the animals of Ediacara into a distinct systematic category: Vendoza.

The name comes from Vendian, the terminal Neoproterozoic in Russia.

Ediacara Fauna Extinction

Ediacara fauna appeared approximately 630 M.y. ago and developed for about 50 M.y.

It represents the first adaptative radiation of the multicellular organisms.

Fossil record is patchy. Last record: in Ireland some about

510 M.y.

Interpretation dynamics

Aspidella case 0.1-5 cm; Canada, 1872; Originally was

considered a pseudofossil;

Reexamined after the Ediacara discovery;

Originally classified as jellyfish;

Anchoring system of Charnia?