Most probably may not be, except the cold water pristine calcitic skeletal corals; as the corals in trophic waters originally precipitate aragonite and get recrystallized/neomorphosed into calcite in a myriad zones and stages of paragenesis, the Sr isotopic values may reflect the transformation and the timing of youngest event rather than the original chemistry and age.

As your thin sections show, there are ample evidences of multiple stages of destructive neomorphism, the samples shown wouldn't qualify.

If you could collect larger foraminifera tests in sufficient quantity and powder them for Sr isotope analysis. Another way, just to compare the value difference, you can choose Coral fragments and benthic forams separately as two samples for analysis.

The sample seems affected by diagenessis and this is erase thier original depositional age and using it well give you a yonger age.

You have to be very careful with the material you use because of potential diagenetic effects. It is best to use skeletal material originally precipitated as low-magnesium calcite, such as oysters for example. Even with low-Mg calcite material you need to be careful to make sure it is pristine. There are a number of petrographic and geochemical steps that can be done to assure you are using unaltered samples. There are numerous papers out there. Here's a paper you can look at to get an idea of the steps done to get good Sr dates. Ortega-Ariza, D., Franseen,E.K., Santos-Mercado, Ramirez-Martinez, W.R., and Core-Suarez, E.E., 2015, Strontium-isotope stratigraphy for Oligocene-Miocene carbonate systems in Puerto Rico and The Dominican Republic: Implications for Caribbean processes affecting depositional history: The Journal of Geology, v. 123, p. 539-560.

Hi Wen-Huang Chen

Dating such ancient biotic carbonate is still challenging because of its sensitivity to diagenetic alteration processes, scarcity of well-preserved fossils, and low magnetic mineral content.

Here is a paper that closely deals with this question.

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/132/3-4/803/573114/Strontium-isotope-stratigraphy-and-paleomagnetic?redirectedFrom=fulltext

Best Regards,

SHA

Since Coral Limestone Rock considered to be One of the most highly porous rocks, these porosities gives a chance to be more saturated with fluids that precipitate some salts and minerals that affect your isotopes age dating and gives you unwanted results.