Shallow upward
Shoal upward
As indicated by Hallock (1987), Hallock (1988), and Hine et al (1988), higher levels of nutrients adversely affect the productivity of carbonates. Conversely the major shallow water carbonate production areas of the Bahamas and the coast of the United Arab Emirates have high rates of carbonate accumulation and are best described as nutrient deserts. Lukasik & James, 2003 working in the Murray Basin (see attached link to animated gifs and a description of a deepening upward cycle) have established that varying rates of nutrient levels change combined with base level change together have controlled the character of the carbonate fill of this basin which built towards sea level but did not reach it:. The effect that Lukasik & James, 2003 describe is probably not uncommon in the many deepening upward cycles of the geological record.
Interestingly the terminology for levels of nutrient in waters of the depositional setting is derived from the literature associated with productivity of organic matter in lake systems; namely the terms:-
- Oligotrophic ("little food"): low in nutrients and in primary production of plants
- Mesotrophic: medium levels of nutrients
- Eutrophic ("well fed"): rich levels of nutrients
Nutrients are usually a mix of minerals that contain N, P, S, K, Mg, Ca, and organic materials that all boost the propagation of plant life, particularly algae. They reduce dissolved oxygen content causing eutrophism, or anoxia and/or causing water to be charged with CO2 often ending existence of other life (for more information click on thelink to John Holmes lecture notes).
References Cited
Hallock,
P. 1988. The role of nutrient availability in bioerosion: Consequences
to carbonate buildups. Palaeogeography, Palaeoclimatology, Palaeoecology.
63: 275-291.
Hallock, P. 1987. Fluctuations in the trophic resource continuum:
A factor in global diversity cycles? Paleoceanography. 2: 457-471.
Hine,
A.C., Hallock, P., Harris, M.W., Mullins, H.T., Belknap, D.F., and Jaap,
W.C., 1988. Halimeda bioherms along an open seaway: Miskito
Channel, Nicaraguan Rise, SW Caribbean Sea. Coral Reefs, v. 6,
p. 173-178.
[ Seismic reflection-based study of Halimeda buildups on the Nicaraguan
Rise. Publication includes several high-resolution seismic profiles to
document position and size of the buildups relative to the adjacent bank
margin. Good example of bank margin buildups.]
Lukasik,
Jeff J., and Noel P. James, (2003), Deepening-Upward Subtidal
Cycles, Murray Basin, South Australia, Journal of Sedimentary
Research, Vol. 73, No. 5, P. 653–671
[Mix of ichnology & faunal diversity are used to determine deepening
upward cycles, depositional setting & correlate lithofacies and chronostratigraphic
surfaces.].
