Gargano Geochemistry Laboratory

These are topics I have looked into that have more science to do. Each entry sketches the question, where the science stands, and the nuanced missing information that is limiting its advancement. They are working drafts and will grow as the science does. Discussion is open at the bottom of the page.

Body water and respiration

The oxygen isotope composition of body water, in both ¹⁸O/¹⁶O and ¹⁷O/¹⁶O, is set by a budget of drinking water, food moisture, atmospheric O₂ taken in through respiration, and metabolic water. That budget makes body water both a physiological recorder and a complication for every proxy built on biogenic minerals.

• Where it stands – steady-state body water models exist and are applied to biominerals.
• What’s limiting it – the respiration terms. The fluxes and kinetic fractionations tied to O₂ uptake and metabolic water production are loosely constrained, and their variability propagates directly into the δ¹⁸O and δ¹⁷O of body water.

Oxygen isotopes of CM chondrites and their carbonates

CM chondrites were altered by water on their parent bodies, and their carbonates precipitated directly from that fluid. Read together, carbonate δ¹⁸O and δ¹⁷O constrain the composition and temperature of the altering fluid, and with it the provenance of the accreted ice.

• Where it stands – carbonate oxygen isotope data exist across CM lithologies, and fluid compositions are inferred through alteration models.
• What’s limiting it – degeneracy. Water/rock ratio, temperature and the initial water composition trade off against one another, so the fluid composition stays model-dependent without co-genetic phase pairs or independent temperature constraints.

Presolar inheritance and the nucleosynthetic dichotomy

Nucleosynthetic isotope anomalies (Cr, Ti, Mo and others) split meteorites into the NC and CC groups, inner and outer solar system. The anomalies are carried by presolar phases, so the dichotomy is ultimately a statement about how presolar carriers were distributed and processed. I am interested in how much of the dichotomy is inherited directly from the carriers, in parallel with the presolar-oxide framework I apply to oxygen isotopes.

• Where it stands – the dichotomy is well mapped element by element, and disk models invoke spatial or temporal separation of reservoirs.
• What’s limiting it – carrier-scale accounting. Which presolar phases host each anomaly, their size distributions, and their susceptibility to thermal processing during accretion.

The diversity of dolomitizing fluids

Dolomite is abundant through the rock record yet resists low-temperature laboratory synthesis, and the fluids that made it span seawater, evaporated brines, hydrothermal waters and microbially mediated porewaters. The diversity of those fluids is itself the record.

• Where it stands – isotopic tools, including clumped isotopes and triple oxygen isotopes (δ¹⁸O with δ¹⁷O), can now separate some fluid classes.
• What’s limiting it – a systematic survey. Dolomitizing fluid compositions have not been mapped across settings and through time, so the recurring fluid types and their drivers remain anecdotal.

D and ¹⁷O excess as aridity proxies

Deuterium excess and ¹⁷O excess in waters and geological materials are widely read as aridity signals through humidity-dependent kinetic fractionation during evaporation. The fluid dynamics complicate that reading. Mixing of vapor sources, moisture recycling, re-evaporation below clouds and the structure of evaporating boundary layers can all move both parameters with no change in aridity.

• Where it stands – end-member evaporation models anchor most interpretations, and paired D and ¹⁷O excess measurements are increasingly routine.
• What’s limiting it – transport. Frameworks that separate mixing and moisture-recycling effects from the local humidity signal before an excess value is converted into climate.

Downwind and downstream, uranium in the Southwest

New Mexico produced 37.5% of US uranium, and the industry left 523 abandoned mines on the Navajo Nation, the Church Rock spill, and measurable uranium, arsenic, and chromium in the region’s water today. This entry is further along than the others. A full data brief with figures, photographs, and sources is up, and the open science is a proposal concept with Jose Cerrato at UNM to read the temporal record of mining contaminants in museum fish-bone collections.

• Where it stands – the spatial footprint is documented by EPA, DOE, and UNM groups, summarized in the full data brief.
• What’s limiting it – time. Monitoring postdates the peak releases by decades, so the temporal progression of contamination is the missing axis that archived museum specimens could supply.

Discussion

Comments are open below. If one of these topics is yours too, or you know of the measurement or framework that unsticks it, I want to hear about it.