11. Foraminifera are mostly one-celled, microscopic marine organisms that are co

Question

11. Foraminifera are mostly one-celled, microscopic marine organisms that are com- monly used in stratigraphy. Some foraminifera are benthic (bottom dwelling) and some are planktonic (loating). Which type could best be used for environmental analysis? Why? Which type could best be used for chronostratigraphy? Why? 12. Below is a sequence of Ordovician rocks, containing abundant trace fossils, ut few body fossils. Unit A is the lowermost rock layer and D is the uppermost rock layer. Use Table 3.3 to determine the environments of deposition for each unit. Unit A = siltstone to sandstone with brachiopod fossils, branching feeding Unit B = bioturbated calcareous shale with few trilobite fossils, many locomo- Unit C- limestone and thinly bedded shale with no body fossils but some very Unit D thinly bedded limestone with chert layers; few shallow dwelling burrows; deep, vertical dwelling burrows; few feeding burrows with funnel shaped tops tion trails; many branching and meandering feeding burrows shallow, curved feeding burrows burrows; feeding trails very close together and meandering, some trails show a polygonal pattern Rock Unit Depositional Environment Do these rocks represent a transgressive or regressive sequence?

Explanation / Answer

11. Benthic foraminifera helps in stratigraphy as they gets deposited on sand stone easier than the one which floats.

Paleontologist looks for benthic foraminifera when he is working on a delta region.

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