grains. SEM examination of muds of this modal size indicated skeletal fragments of 
mollusks and forams. Grains >10 4> have plate, bun and prismatic shapes consistent with 
a mixed skeletal origin. Strontium vs. aragonite values do not vary with different mud 
sizes, and, together with SEM evidence, indicate mud generation through local 
breakdown of available shelly faunas. Three end member sources for the muds are 
suggested: high aragonite- low strontium mollusks, low aragonite- low strontium; 
forams, Thalassia epibionts and lithoclasts, and high aragonite-high strontium green 
algae. Surface sediments and thin sections indicate that deposition is often in the form 
of mm sized fecal pellets. These biodetrital mud-mounds are therefore characterized by 
progradational geometries, physical erosional and depositional sedimentary structures, 
associated facies with coarser biogenic textures, silt-sized skeletal mud of mixed 
mineralogy and geochemistry and an absence of microbial textures and structures. 
1990 0 
Bosence, D., and D. Waltham (1990) Computer modeling of the internal architecture of 
carbonate platforms. Geology . 18:26-30. 
[NO COPY OF PAPER AVAILABLE. ABSTRACT FROM SCHMIDT (1991).] A numerical 
computer model is described that calculates the internal architecture of carbonate 
platforms in response to varying values of carbonate production, subaerial and 
submarine erosion, sediment redeposition, and sea-level changes. The computer¬ 
generated sections closely resemble large-scale outcrops and interpreted seismic 
profiles through carbonate platforms. Stillstand and transgressive sequences have 
prograding and downlapping platform geometries with lagoons developing in 
transgressive systems. Regressive sequences have downlapping clinoforms and 
erosional upper surfaces. Carbonate erosion rates are varied and have an important 
effect on the morphology of floodback surfaces. Data for lagoonal and back-reef 
production rates are taken from Bosence (1989). The computer program gives a visual 
picture of the quantitative effects of the many parameters controlling carbonate 
geometrices, and it aids quantitative analysis of the architectures and time scales of 
ancient outcrop or seismic sequences. 
1990 0 
Rude, P. D., and R. C. Aller (1990) Fluorine and strontium mobility during carbonate 
mineral diagenesis. EOS. Transactions . 71 (43): 1421. 
[ABSTRACT ONLY. DATE OF SAMPLING UNKNOWN OR NOT APPLICABLE.] The F content 
of biogenic marine carbonates varies with mineralogy (calcite: 20 - 1200 ppm; 
aragonite: 650 - 1600 ppm), positively correlates with the Mg content of calcite, and 
occurs in similar abundance to Sr (high-Mg calcite F/Sr = 2.4 mol mol* 1 ; aragonite: 
0.53 - 0.79; low-Mg calcite: 0.22). Models of pore water over the upper 0 - 15 cm of 
sediment in the shallow water carbonate muds of Florida Bay give fluxes of Ca 2+ , Sr 2 + 
and F* out of the sediment due to carbonate dissolution which should produce measurable 
compositional changes to the deposit. The flux ratio of F/Sr (0.71 mol mol* 1 ) is 
consistent with a biogenic carbonate source but the F/Ca and Sr/Ca are 3-10% that of 
the bulk sources. Selective dissolution of a high F and Sr content phase or concurrent 
dissolution and precipitation of phases with different F and Sr contents are possible 
explanations for this discrepancy. The sediment deposit is -50% aragonite, -40% high- 
Mg calcite and -10% low-Mg calcite. The sediment F/Ca and Sr/Ca are lower than that 
of the source material, and this difference could be produced in a few tens of years by 
the preferential loss of F and Sr predicted by pore water distribution-derived fluxes. 
These measurements demonstrate that significant mineralogical diagenesis occurs on 
rapid time scales in nearshore carbonate sediment and that F is probably extremely 
mobile in other carbonate environments undergoing diagenetic alteration on short and 
longer time scales. Although phosphatic phases and fluorite may play a role in 
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