Black Box of
a plane is perhaps the most significant hardware! It is the only witness
to the tragedy, in case of a plane crash. And interesting thing about
the black box is that it records too! Therefore, whether land or ocean
wherever the plane crashes the black box is much sought object.
Natural disasters for example in the abyss of the oceans are often
witnessed only by mute organisms. Matters become complex when we talk of
disasters that struck millions of years ago. For example we talk of
drifting of continents, continental collision, global chilling and
global sea level changes in the past. Such disasters have been
truthfully recorded by and particular species of fossils like the
sequence of events recorded in a Black Box. Geologists are able to
locate, identify and interpret such black boxes and use the information
to unfold the mysteries of nature.
It was a
windfall for Sabyasachi Shome of Geological Survey Of India, Kolkata
who discovered in the Kutch region of Gujarat few such ammonite
fossils that are now being considered as marine black boxes. Shome
along with a team of experts from the Department of Earth Sciences,
Jadavpur University and Indian Statistical Institute, Kolkata
published the findings in Current Science (January, 2004) and
described the significance of the fossils discovered.
It is indeed intriguing that some of the organisms of the bygone
eras appeared on the Planet only for a short while, yet their
bio-geographical spread was wide. It was as if these organisms were
trying to spend a 'little hour of grace on our Earth. Such fossils
are described as 'fleeting fossils' say Shome and his co-workers.
Ammonites are an extinct group of marine animals belonging to the
class Cephalopoda and Phyllum Mollusca. They are excellent index
fossils says the Wikipedia. In other words some species of ammonites
are such that one can establish the time period when a particular
layer of rock was deposited in the sea.
Many of the ammonites are fleeting fossils. Such fossils are sort of
biological stopwatches, with the help of which the paleontologists
are able to decipher the minute details of the earth's history.
Ammonites are environment sensors too. They are exclusively marine
organisms and many species are restricted to particular latitudes.
With the help of such fossils it is therefore possible to
reconstruct the past geography too.
Rifts and polarizations in the contemporary society are order of the
day. Reasons for such incidents could be many. It is an irony that
drifting and polarization of continents has been going on since
times immemorial. In the geological past when human evolution had
not taken place the forces of nature made the continents drift apart
or collide. The process of the last fragmentation of the earth's
continent began in the Jurassic period of the earth's history some
203 to 141 million years ago (Ma). India was then part of a
super-continent, the Gondwanaland and started drifting away nearly
120 Ma to make its solitary journey of approximately 8000 km before
hitting the Asian Plate. The wandering Indian continent carried all
the living and the dead (fossils) including the ammonites too like a
giant Noah's Arc.
At the beginning of the 'split', around 170 to 140 Ma, West Gondwana
that comprised of Africa and South America separated from East
Gondwana consisting of India, Antarctica and Australia.
Palaeontological evidences indicate that eastern part of Africa and
Madagascar and western coast of India support a fauna typically
endemic to Indo-Madagascar faunal province.
It is believed that India and the southern part of Africa were
land-locked till about 140 Ma. During this time sea level
fluctuations were galore on major continental shelves (land sloping
in to the sea). The region now called Kutch in Gujarat was facing a
regression of the sea. Thus while in India during end of Jurassic
period (about 141 Ma) and beginning of Cretaceous period there was a
steep fall in the sea level, Madagascar coast had open sea, meaning
regression was not there. Naturally this type of sea had a typical
ammonite fauna. At the end of Jurassic period there was a global
'flooding'. The sea level rose.
This facilitated many of the ammonite families to have a
circum-global distribution. Shome and his friends have been lucky in
locating ammonites belonging to the subfamily Himalayantinae. The
genera belonging to this subfamily had a greater bio-geographical
spread. Ammonites being highly sensitive to sea level changes
vanished from an area as soon as the sea level went down. This
character was common with the ammonites of the upper most Jurassic
that is 141 Ma. Prior to discovery made by Shome and his colleagues
the genera of the subfamily Himalayantinae were known only from the
Tethys (Himalayas), East Africa, Mediterranean and Pacific
provinces. The discovery of ammonites of this subfamily from Kutch
has created a history of sorts as because of them it is possible to
mark the palaeo-latitudinal position of Kutch. One of the fossil
genera Tethopeltoceras was earlier only known from the
Mediterranean.
Ammonite palaeobiogeographical distribution is controlled by
palaeoclimate and temperature says Shome and his co-workers. These
two factors are influenced by paleolatitudes. The fossil
Tethopeltoceras is latitudinally sensitive and its presence in Kutch
indicates that this part of the coast was near 300 latitude. The
find also suggests the presence of a sea connection between India
and Africa during the end phase of Jurassic period.
Not only fossils, even living organisms have interesting 'black
boxes' with in them. For example, Statoliths are calcareous
structures located in the equilibrium organs of cephalopods, which
serve to detect body accelerations during movement in water. They
are perfect 'black boxes' because they record a lot of information
about the lives of squid and cuttlefish. For instance, it is
possible to reveal the hatchling size and temperature of embryonic
development, estimate age and growth rates of the animal with daily
precision, date life transitions, analyze possible migratory routes
and population structure of squid using trace element analysis, and
even reveal how many spawning events a given animal has had by
analyzing statolith microstructure. Statoliths are usually one of
the few remains of squid in fossil records, and their features can
be used to infer ideas about the life styles of extinct species.
Man's inquisitiveness about the past and the future is boundless.
How the life came in to being on this Planet, what was the
configuration of past continents and oceans, what was the food for
the fauna and flora of those days etc are some of the questions that
haunt the paleo-biologists and paleo-geographers alike. Knowledge
about the past opens the windows to the future.
May be we find someday a 'black box' that might tell us the secrets
of longevity and happiness!
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Natural disasters for example in the abyss of the oceans are often
witnessed only by mute organisms. Matters become complex when we talk of
disasters that struck millions of years ago. For example we talk of
drifting of continents, continental collision, global chilling and
global sea level changes in the past. Such disasters have been
truthfully recorded by and particular species of fossils like the
sequence of events recorded in a Black Box. Geologists are able to
locate, identify and interpret such black boxes and use the information
to unfold the mysteries of nature.