Deep Sea Life And Paleontology

[pinkpantherbeekeeper]

Another question I have been pondering. What was deep sea life like in the Paleozoic and Mesozoic? I understand that the continents shifted, rose, fell, and changed thus leaving us with sea fossils on the surface of the earth currently. However I wonder if we know anything about what life was like in deep oceans. Obviously we have deep ocean oil rigs. These from my understanding are pumping oil from what was once land or shallow oceans? Anyway I wondering if there is a good fossil representation of the deep?

[siteseer]

A lot of the marine rock that old has been destroyed by subduction or erosion (or too deeply buried to reach) so we will never know most of the deepwater environments that have ever existed. I think the Early Devonian Hunsruck Slate (Bundenbach, Germany material) is considered a deepwater deposit. Unusual fossils have been found there including a late-surviving relative of Anomalocaris and these fossils often show soft body details when X-rayed.

The Early Jurassic "Poseidon Shales" of Holzmaden, Germany is considered a deepwater deposit as well.

The Late Cretaceous Northumberland Formation of British Columbia, Canada represents a deepwater fauna. Many shark genera known to frequent deepwater today (Squalus, other squaloids, Pristiophorus,Echinorhinus, Chlamyoselachus) have been found in the unit.

Few such deposits of Cenozoic age are known as well. Many likely remain in deepwater.

Another question I have been pondering. What was deep sea life like in the Paleozoic and Mesozoic? I understand that the continents shifted, rose, fell, and changed thus leaving us with sea fossils on the surface of the earth currently. However I wonder if we know anything about what life was like in deep oceans. Obviously we have deep ocean oil rigs. These from my understanding are pumping oil from what was once land or shallow oceans? Anyway I wondering if there is a good fossil representation of the deep?

[Ridgehiker]

Interesting question. The above posting sums a lot of it up. 'Deep' is a subjective term. In general not a lot happening in the deepest depths. There is macro life but spotty. However, most important is very little life is fossilized. Ocean floors tend to be stable...few forces like slumping, big tsunamis, organic sediment, etc. to preserve anything. Then, as siteseer points out, what little that was preserved often destroyed by subduction. If things sit exposed in most water or land they are eaten by something.

The limited evidence today from the Paleozoic tends to be micro foraminifera. There are graptolites but these were fauna that were usually pelagic and died and sunk to be deposited on deeper ocean floors. These are often found in thin black shales sterile of other macro life.

[painshill]

It’s also worth noting that a mine in China has yielded fragile remnants of ancient “black smoker chimneys” up to three feet tall which contained fossil microbes dated to 1.43 billion years old [Kusky, 2007]. These chimneys are characteristic of very deep oceanic water where vents in the Earth’s crust spew out extremely high temperature water (up to 400 degrees Celcius) that is rich in minerals and can sustain primitive bacteria without the need for oxygen or sunlight.

There is still the distinct possibility that life evolved near deep-sea hydrothermal vents like this, as opposed to in shallow seas. The evidence for the latter comes from much older stromatolitic structures (around 3.5 billion years) which definitely formed in shallow seas. But we don’t know for sure if the overall picture has been distorted by the degree to which those are more likely to have survived in a recognisable form in the geological record.

[pinkpantherbeekeeper]

Thanks for the information everyone!