Microfossil Question In Need Of Help Please

[DE&i]

I’m about half way through my Introduction to Fossils and Palaeontology course now with my homework coming thick and fast.

Here’s an edited paragraph from my said homework of which ive pretty much nailed the answers. But one question in particular is giving me some bother.

(Microfossils in Triassic desert gravels?) Ive looked high and low but can’t seem to get a foot hold on it could anyone point me in the right direction please.

Homework paragraph below.

“This week we started to look at specific fossil groups, and in particular microfossils. I have a question for you is "Why do you think that microfossils are the most economically important fossils?"

“As a supplementary question ....." which microfossils would you look for in: i) The Cretaceous Chalk ii) Devonian marine mudstones iii) Jurassic freshwater lake sediments iv) Triassic desert gravels?" One word answers will do, with a short paragraph (at most) to explain why.”

Regards,

Darren.

Edited November 23, 2014 by DarrenElliot

[Herb]

microfossils are used by oil companies to locate strata that might contain oil. Microfossil ranges are limited, if you find a particular foram in an oil bearing strata, then it is likely that there is also oil in another strata that contains the same foram.

1. forams, ostracods, cocolthophores.

2. ostracods, conodonts, scolecodonts

3.freshwater diatoms , pollen, algae

4. pollen, micro vertebrate teeth and bones?

let me know how you do on the test.

[Oxytropidoceras]

It was stated,

"I have a question for you is "Why do you think that microfossils

are the most economically important fossils?"

Microfossils are are among the most economically important fossils

because they are both small enough and usually abundant enough

to be recovered intact and in the large numbers needed from very

small samples from either cores or cuttings of oil and gas wells to

be usable as guide fossils in biostratigraphy.

Megafossils can also be used as guide fossils for determining the

age of sedimentary rocks. However, they are impractical for use

in correlating sedimentary strata penetrated by oil and gas wells

and other drill holes because in cuttings they are typically reduced

to unrecognizable and unusable fragments. If present in

cores, they will typically occur in numbers too small to be useful

in biostratigraphy. This is a direct result of their size.

Biostratigraphic Correlation

1. http://www.priweb.org/ed/pgws/paleo/paleo_home.html

2. http://www.ucmp.berkeley.edu/fosrec/ONeill.html

3. http://www.geomore.com/biostratigraphic-correlation/

Microfossil Laboratory

http://www2.fiu.edu/~kpanneer/lab_assignment/Lab4_Microfossils.pdf

Yours,

Paul H.

Edited November 24, 2014 by Oxytropidoceras

[DE&i]

I’m about half way through my Introduction to Fossils and Palaeontology course now with my homework coming thick and fast.

Here’s an edited paragraph from my said homework of which ive pretty much nailed the answers. But one question in particular is giving me some bother.

(Microfossils in Triassic desert gravels?) Ive looked high and low but can’t seem to get a foot hold on it could anyone point me in the right direction please.

Homework paragraph below.

“This week we started to look at specific fossil groups, and in particular microfossils. I have a question for you is "Why do you think that microfossils are the most economically important fossils?"

“As a supplementary question ....." which microfossils would you look for in: i) The Cretaceous Chalk ii) Devonian marine mudstones iii) Jurassic freshwater lake sediments iv) Triassic desert gravels?" One word answers will do, with a short paragraph (at most) to explain why.”

Regards,

Darren.

Hi Herb and John H,

Thank you for the extended advice and suggestions these are the answers I’m going to submit..:

“The point of view I’d like to get across is that microfossils are very important for the never ending search for fossils fuels. Oil companies have a micropaleontologist as part of their drilling team who look for certain variations in sediments contain microfossils from core samples as the drilling progresses. To try to find some indication the fossil fuels are nearby.

The Cretaceous Chalk: Microfossil (Coccolithophores) Chalk is formed from lime mud, which accumulates on the sea floor in the right conditions. The lime mud is formed from the microscopic skeletons of plankton. The Coccolithophores are the most important group of chalk forming plankton.

Devonian marine mudstones: Microfossils (Scolecodonts) the predominantly Devonian slate mudstones were formed by deep burial of marine and non-marine mud with associated lime- stone, sandstone and volcanics

Jurassic freshwater lake sediments: Microfossils (Ostracods) there where many marine transgressional events occurring periodically in the Jurassic freshwater lakes around the world depositing many species of foraminifera.”

“Now for this last question I feel sure this could be a bit of a red herring, so this is the answer I’m going to give.”

“Triassic desert gravels: Ive been researching coast records especially the turning point between the Triassic and Jurassic eras. It used to be mountainous desert along some of these coasts. Would it be an incursion of Jurassic seas into a Triassic deserts, followed by a retreat would leave traces of Scolecodont-like microfossils...?”

Regards,

Darren.

[DE&i]

microfossils are used by oil companies to locate strata that might contain oil. Microfossil ranges are limited, if you find a particular foram in an oil bearing strata, then it is likely that there is also oil in another strata that contains the same foram.

1. forams, ostracods, cocolthophores.

2. ostracods, conodonts, scolecodonts

3.freshwater diatoms , pollen, algae

4. pollen, micro vertebrate teeth and bones?

let me know how you do on the test.

Hooray for me…not one to blow my own trumpet but my research paid off Tutor response below:

“Well done Darren- a very thorough answer!

The Triassic desert question is a bit if a trick question. The answer is pollen can be blown long distances and may be present in a desert BUT the deposition of sediment whether by wind or desert flood will deposit gravel, sand or silt sized particles of broadly similar size. Pollen is so small that it will only get deposited in very fine sediment, and so very unusual to find in gravel. The other problem in a desert sediment is that the grains tend to get strongly oxidized (i.e. they get reddened and organic particles degrade and so preservationof plant material is very rare.”

[Herb]

Well done!

[verydeadthings]

I can just imagine some poor palynologist spending days searching through Triassic sands for a single pollen

When you're dealing with microfossils you always have to consider the sedimentation rate. If there's too much inorganic stuff being deposited your tiny fossils are going to be so rarely found it's not worth looking for them.

[verydeadthings]

I should also add that in desert environments generally stuff is getting eroded, not deposited. They're a great place to find fossiliferous strata, but generally not a great place to form fossils.