Stromatolites and its stratigraphic implications

2. Seminar Content
Introduction to stromatolites
Origin and evolution
Evolution of precambrian stomatolites
Stratigraphic significance of stromatolites
paleozoic stromatolites
mesozoic stromatolites
cenozoic stromatolites
Conclusions
Reference

3. Introduction to stromatolites
Stromatolites are the oldest known fossil Algae
dating back approx. more than 3 billion years
They are in the form of colonial structures formed by
photosynthesizing cyanobacteria and other microbes
Cyanobacteria are prokaryotes which are primitive
organisms
Stromatolites are in fresh water environment.
 They are chorophyllus, having simple thallus body
They are responsible for the changing of Earths
oxygen atmosphere.

4. contd
They are dominated as the primary lifeform on earth
for over two billion years
Presently stromatolites are rare nearly extinct

6. Modern Stromatolites
Very rare
Found in the waters Shark Bay of W.A.
(Australia)

7. ORIGIN & EVOLUTION of Stromatolites
The fossil algae originated from the lower plants.
varieties of algae are green in colour some have
brown, red ,blue in colour
They are unicellular , multicellular
,nonfilament,filament,unbranched,branched
microscopic actritards
They formed in the proterozoic rocks and perfectly
preserved in the precambrian rocks

8. Evolution of Precambrian
Stromatolites
It laterally, within a given basin,stromatolitic units may
be time transgressive as is the case for so many
lithological units.
The recorded appearance of new microstructural types
of stromotalites cannot be explained in terms of
different preservation
Algal evolution itself is not so much important in terms
of the progressive changes affecting the morphology
of the filament or of the cells
In terms of extinction emergence and radiation of
individual algal taxa

9. Relative stratigraphic significance of stromatolites

10. STROMATOLITES FROM PROTEROZOIC
SEDIMENTARY BASINS OF PENINSULAR INDIA
KALADGI- LOKAPUR FORMATION
Chandrashekara Gowda, M.J and Govindarajulu,B.V.
DODDAGUNI CHERT- TUMKUR
M.Basavaraju and V.Venkatachalapthy
PUBLISHED REPORTS FROM
DOS IN EARTH SCIENCE
UNIVERSITY OF MYSORE

11. Paleozoic stromatolites
Effects of the rise of Invertebrates:
The rise of the invertebrates had both positive and
negative effect upon the blue green algae .The hard
parts of invertebrates ,including individual skeletons
as well as the stony communities represented by the
successive types of reefs ,constituted a new and ever
changing substrates for blue algae and other algae
Blue green algae were most probably an source of food
for the successive animals which had realized the
required physiological adaptations

12. Mesozoic stromatolites
These have been relatively poorly studied .
Although they are still found in various marine and
peri marine habitats ,marine stromatolites more
confined to the margins of their prospective niche
furthermore competition other algal groups become
stronger in Mesozoic times than during the Paleozoic
Mesozoic stromatolites are most abundantly reported
from inter – to supratidal settings where they
withstood severe conditions they constituent a
unique facies of cyclothymiacs formations ,capping a
deeply weathered and prism –cracked limestone
member

13. continued
Many mesozoic subtidal stromatolites record similar
conditions .first of all they seem to have developed in most
extreme shallow water positions , secondly stromatolitics
thin beds frequently occur at the base of a transgressive
sequence where they over grow a basal conglomerate .
finally they accompany statigraphical gaps in the later
case ,they are often associated with a rich faunna as
opposed to most stromatolitic beds the associated fossils
are obviously reworked .
All these occurrence reflect once more the marginal
ecological situations to which the bulk of blue green algae
were now confined.

14. Cenozoic and recent stromatolites
As for the geological record of stromatolites their
realized niche changed drastically from the beginning
of the cenozoic onward
Fossilizable stromatolites are indeed very rare in
cenozoic sediments but extremely abundant in
lacustrine deposits from all over the world
Many of these recent formations are represented in
cenozoic sediments by algal limestones
The spread of highly competitive red algae , plus the
ecological pressure that have traced from the
paleozoic onward

15. continued
And that kept driving blue green algae towards the
margin of their prospective niche
Account for the present day situation i e the poor
representation of cyanophyta in marine environment

16. Conclusion
Blue green algae are a rather conservative group
showing limited morphological evolution during
precambrian times
The process of speciation and extinction may have been
quite effective in the modification of stromatolites
properties
Although mesozoic stromatolites were still found in a
wide range of environments ,from the supratidal flats
down to deep waters , they no longer built impressive
deposits in the sea where their individual size remains
quite small

17. continued
Stromatolites hve only been discussed in terms of blue
green algal coenoses ,we have indeed good reasons to
believe that the bulk of fossil stromatolites was due to
the activity of blue green algae

18. 1973 ,L.V MONTY,
PRECAMRIAN BACKGROUND AND PHANEROZOIC HISTORY OF
STROMATOLITIC COMMUNITIES AN OVERVIEW,Tome 96 -1973-
Fascicules 111(pg:590-592),(607-614)
WIKIPEDIA
Chandrashekara Gowda, M.J and Govinda Rajulu, B.V (1980)
Stromatolites of the Kaladgi Basin and their significance in
paleoenvironmental studie J .G.S.I. Miscilaneous Pubn.No.44,
Pp.220-239.