UNIVERSITY OF CALGARY SPRING 2010

GLGY 209-20 INTRODUCTION TO GEOLOGY I

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