##  [Age-Depth Model (Marine Core)](/age-depth-model-marine-core-0) 

 Definition

A marine sediment concept defining how particles accumulate, are reworked, and change after burial on the seafloor. It governs depositional processes, physical properties, and post-depositional reactions measured through cores and laboratory analyses. It does not uniquely identify sources or processes without supporting stratigraphic, mineralogical, and geochemical evidence. It materially affects habitat, slope stability, and climate records by controlling the properties and composition of seabed deposits. The concept is generally stable, though analytical resolution and property measurement methods improve over time.



 

 

 

 

 

 





## Principle

Principle

Age-depth modelling enforces stratigraphic order (ages increase downcore) and reconciles discrete age controls with interpolation or stochastic models (linear, spline, Bayesian accumulation models) while incorporating hiatuses, variable sedimentation rates, reservoir corrections and dating uncertainties to produce probabilistic age estimates.

 

 

 

 

 





## Demonstration

Demonstration

Constructing a Bayesian age-depth model for a piston core using calibrated radiocarbon dates with reservoir correction, two tephra tie-points and a paleomagnetic reversal horizon; the model yields median ages and credible intervals at all depths, and highlights deeper intervals where age uncertainty widens due to sparse controls.

 

 

 

 

## Misapplication

Misapplication

Applying simple linear interpolation between sparse dates without accounting for reservoir offsets, reworking, bioturbation, or hiatuses; treating point ages as exact rather than probabilistic or ignoring stratigraphic order violations created by reworked material.

 

 

 

 

 





## Consequence

Consequence

A well-constrained age-depth model allows timing of paleoceanographic events, sedimentation-rate calculations, correlation across sites, and conversion of proxy records from depth to time space with explicit uncertainty bounds that inform paleoenvironmental interpretations.

 

 

 

 

## Reversal

Reversal

Using a depth-to-age inversion that assumes constant sedimentation or equidistant sampling ages (for example assigning equal time steps per centimeter) reverses the concept by imposing uniform rates and hides real variations in deposition and hiatuses.

 

 

 

 

 





## Boundary

Boundary

Valid within the recovered core interval and constrained by the density and quality of chronological tie-points; extrapolation beyond core ends or across major unconformities is speculative, and models are limited by method-specific biases (e.g., reservoir effect in radiocarbon) and mixed/reworked sediments.

 

 

 

 

 





## Semantic Tension

Semantic Tension

Tension exists between deterministic interpolation approaches (linear, spline) that give a single curve and probabilistic Bayesian methods that produce distributions — the choice affects reported uncertainty and downstream interpretations of rates and event timing.

 

 

 

 

 





## Synthesis

Synthesis

An age-depth model for a marine core is a stratigraphically consistent, often probabilistic map from depth to age built by integrating multiple chronological proxies and stratigraphic constraints; best practice quantifies uncertainty, accounts for hiatuses and reservoir effects, and uses independent markers to anchor the chronology.