Calcium Isotopes and Carbonate Diagenesis

What similarities do C and Ca have

• Both major elements in carbonates

• Fluid-rock ratios required for alteration broadly match each other

Sources of Ca to the ocean

Continental weathering and hydrothermal inputs

Sinks of Ca in the ocean

Deposition and burial of carbonate minerals

What happens to the Ca isotopes if you double Ca input flux into the ocean

No significant change from changes in global fluxes once the output flux is scaled by omega. This is due to strong carbonate buffering.

What do steady state Ca isotopes respond to

Changes in BD44Ca

What controls the BD44Ca

Rate of precipitation impacts fractionation between Ca species. With faster precipitation creating a Larger fractionation (more negative Ca values)

What Ca isotopic value would primary aragonite have

Light d44Ca from faster precipitation and lack of alteration

What would Ca isotope value from a pore water mineral have

Heavier d44Ca due to slower precipitation rate causing a lower fractionation

How do Ca isotope values of the sediment change within the sediment profile

D44Ca increase with depth

How do Ca isotope values of the fluid change with depth into sediment

D44Ca decrease with depth into sediment

Why do Ca isotope values in a sediment profile converge at 100 mbsf

The system is reacting with the same pore fluid that the minerals precipitated from. When CaCO3 dissolves, the two mix back and then reprecipitation is the same for both the pore fluid and the sediment.

What is the trend of Ca isotope values with increasing F-R interaction

d44Ca values become heavier with more F-R interaction

If NeoP CIE were the result of diagenesis, what would the associated D44Ca values be

Positive excursions if diagenesis was present

How could two primary aragonite d44Ca signals not be reflective of global conditions

The signals have different environmental conditions (LST vs Max flooding surface) that result in different signals

What occurs when a platform is fluid buffered

More diagenesis occurs (higher d44Ca and low Sr/Ca), the greater fluid flow allows for more alteration within the rocks as more F-R interaction can occur

Is a sediment or fluid buffered system more likely to preserve the isotopic signal

Sediment buffered system