One of the most problematic age determination of rock units is referred to change in stratigraphic range of some foraminifer taxa as endemic species and facies change in Cretaceous of the Zagros shallow water facies, probably it is assigned to paleobathymetric change. I will appreciate that anyone interpret presence and extinction of shallow water foraminifer and provincialism and Cretaceous sub stage.
Facies taxa occur everywhere that a given combination of bathymetry (CO2), water temperature, salinity, light penetration and trophic conditions appear. Such taxa are in principal cosmopolite, and they evolve following the rules of their own lineage, some of them have short ranges and may be age indicators. Among a given number of these taxa, some species may be relatively abundant and representing endimic species that are not found elsewhere. According to their importance they may be define a faunal province, as they appear to be limited in space, but heterochroneous in time. The Zagros may show more abundant faunas of Southern Tethyan affinity, whereas strata of the same age and facies in the Pontids may eventually yield different taxa that exhibit a rather Northern Tethys affinity, as originally a huge ocean separated the two. To estimate provinciality it is necessary to be in the presence of the same facies and approximately the same age.
Taphonomic analyses should be done previously to any paleobiogeographic or paleoecologic interpretation. Stratigraphic ranges are not paleobiologic ranges. That we have are taphoregisters. Vertical range does not correspond actually to temporal distribution of taxa, and preservation may be linked to taphonomic factors related to facies. Taphonomic processes such as necroplanctonic derivation, rejoining, or other biostratinomic displacements can also deeply modify geographic distribution of fossils, and some of the biostratinomic displacement mechanisms may be related to facies.
Firstly, you need a good sampling to observe the stratigraphic control on the distribution of the fossils. Maybe these papers could help you
Holland, S.M., 1995. The stratigraphic distribution of fossils. Paleobiology 21 (1), 92–109.
Holland, S.M., 2000. The quality of the fossil record: a sequence stratigraphy perspective.
Paleobiology 26 (4), 148–168.
Dear Massih,
I think provincialism is regional in extent, rather similar to present day natural or climatic regions. As indicated provincialism is mostly influenced by climatic factors, ie, all elements that are incorporated in climate -temperature, humidity, rainfall, wind, ice, ocean currents, sunshine, cloud, and so on. Indicator flora/fauna are commonly cosmopolitan types that are not restricted.
Within the provinces are obtained localized factors that give rise to facies. Thus within the Southern Tethys Province, as suggested by earlier contributors, there are places distinguished by special factors that are more or less local in extent, sustaining the specialized, well adapted biota. Within the province, shallow water dwellers associated with coarser sediments will differ from deep water dwellers in finer sediments. Even on land, the biota of forest lands will differ from those of the less watered inland areas away from the coast.
These specialized facies biota will occur with the cosmopolitan provincial forms even in low frequencies. Remember that those facies indicators could occur in large abundances because of specialized conditions, the "opportunistic" species..
All the best.
Obianuju P. Umeji.
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