Paul:

In non-marine facies Palynomorphs are generally considered as offering better biostratigraphic resolution than accompanying megafossils. In certain marine facies, megafossils like ammonites could offer much better resolution than marine palynomorphs. So it all depends on the age and facies of sedimentaries one is dealing with.

Best

Syed

Dear Paul,

Some macro fossils or megafossils such as Ammonoides or Brachiopods can be used for biozonation such as clymenids (Devonian system), Pseudogasterioceras (Permian/Triassic Boundary), some macrofossils had short time living range in phanerozoic, another point is the resolution of sampling and insitu point (in original place) of macrofossils. Best wishes 

As others have indicated, it depends on what you have. In the Jurassic if ammonites can be collected in sufficient quantity and quality estimated time resolution can be as low as 140ky, about o.1% of the age of the sediments !

I completely agree with the above said. It depends on what you have. If you only have an imprint macroflora, then you have to use the macrofossils.

but palynomorphs often get a better biozonation; and most of the ófficial' zonation is based on faunal remains such as ammonites, conodonts etc.

One of the great limitations of palynomorphs is that they are not preserved in the highest stages of diagenesis and in metamorphic rocks.  However, plant megafossils are preserved throughout the various stages of diagenesis and in metamorphic rocks.  

I agree with Sayed: in marine series macrofossils such as ammonites are better to use in biozonation but in continental series palynomorphs may be used for regional biozonation.

but if there are no palynomorphs, neither faunal remains, then Plant microfossils are the only way for biozonation.

Palynomorphs are important as environmental indicators and as biostratigraphic tools. Palynomorphs offers high biostratigraphy zonation than the accompany mega fossil.However both are very useful as a  biostratigraphy  tool.

Palynomorphs for its smaller size fossilize better than mega fossil. In addition, there are better environmental index, so there are offer preferable biostratigraphy zonation than mega fossil.

For biostrigraphy particularly in oil exploration, palynomorphs are better than plant megafossils, marine or continental. Although the sedimentary structures and age do influence the recovery, the regularity, ubiquity, abundance of palynomorphs make them better. Plant  megafossils are relatively difficult to indentify, fragmentary in nature and are not easily encountered.

One of the limitations of palynomorphs is they can be easily re-worked. Do you know of some examples?

Paul:

Besides limitations the advantage of palynomorphs lies in their small size and numbers. Reworking, leaking and contamination is a problem when dealing with exploratory well-cutting samples and the problem is overcome by taking frequent side-wall cores. Reworked palynomorphs are a blessing in mobile belts providing clue to the rocks which are subsequently discovered and mapped in difficult terrain.

Best

Syed

Dear Syed,

I am giving you an up vote on your answer. Best wishes, Paul.

Paul:

Thanks for your kindness.

Best

Syed

Palynomorphs are much better for dating resolution than megafossils. If a biozonation is based upon ammonoids or brachiopods, the latter is also facies dependant, the usual course of action is to sample the horizon where the megafossil was found. In Ordovician to Devonian sedimentary rocks a brachiopod biozone may be based on a single genus or even species. The same horizon may yield several dozen species of chitinozoans which are very good biostratigraphic tools from early Ordovician to late Devonian (Frasnian) as well as also yielding spores from Silurian right through the Devonian. In Cretaceous sediments the rocks adjacent to an ammonite could yield pollen, spores, coccoliths and dinoflagellates and the megafossil biozone could be subdivided further. With the variety of palynomorphs at a certain horizon a composite profile would provide a very good biostratigraphic profile..

The limitations for palynomorphss is often dependent on the worker. If there is a mixing of horizons such as with well cuttings the sample might be first separated on the basis of sediment type. If the original sediment that the palynomorphs was found in was reworked the palynomorphs could appear darker, or may appear to be a quite different age. Autoflorescence could help in that case. If reworking of a rock occurred, a composite biostratigraphic assemblage is determined and if there were two different biostratigraphic suites of palynomorphs that could indicate reworking.

Other kinds of reworking can also occur.  In a study of  Cretaceous waters contaminating the Prairies Evaporites I separated the salts from the clay layers using a rock saw. Processing the salts and clays separately I found that the clays contained Upper Givetian spores and megaspores while the salts contained Cretaceous palynomorphs such as pollen, spores and dinoflagellates from an Albian age. This suggested that flood waters from a lower Cretaceous source had invaded the Devonian Prairie evaporites. The clays did not contain any Cretaceous palynomorphs and had resisted reworking from the flood waters much better than the salts.   Based on the Devonian spores and Megaspores I was able to determine four different palynomorph assemblages based on complexity that suggested that climate change determined what sort of salt would accumulate. That is clays from sylvite had simple spores indicating arid conditions, while the halite layers contained complex spores and megaspores.

I have also used melanosclerites from flood waters in a potash mine to determine the source after processing core from adjacent wells. The corresponding core sample was Upper Givetian and had an extremely abundant assemblage of Melanosclerites (various juvenile stages) and a good assemblage of chitinozoans. Processing corresponding core can help confirm reworking. in many cases such as insolubles in water samples or well cuttings.  Megafossils are difficult to determine from cuttings although pieces of gastropods and trace fossils could be determined, but there is little information to gather from wellcuttings for megafossils. Reworking often destroys the megafossils especially if the megafossil is plants or calcareous in nature. Information from megafossils from core is also very limited.

Paul:

My RG account is hacked. Cant upload lengthy answers.

Best

Syed

Patrick,

I am giving you an  up-vote on your very thoughtful and informative answer to my question. Paul.