What it is
Samples drawn as pie charts, not symbols: wedge size is the share of grains at a given lag time, wedge colour is the lag bin. Short lag means an active arc nearby; long lag means an old craton. Built from ~987,000 grain ages across 19,564 samples.
A sample shows only within 5 Myr of deposition, then goes. The page is about when a rock was laid down.
Contents
- PiesWedges by lag-time bin, sized by share of grains.
- LifespanVisible within 5 Myr of deposition, then gone.
- BoundariesReconstructed ridges, trenches and transforms, 0–1000 Ma.
Controls
- Drag to rotate, scroll to zoom.
- Scrub or press play.
- Hover a pie for the sample detail, click to pin.
Lesson sketches
Convergent, collisional or extensional?
- Find a sample dominated by short-lag wedges. Describe the tectonic setting around it.
- Find one dominated by long lags. Same again.
- Find a mixed one and argue for a setting.
- Check each against what the reconstruction shows.
What kind of basin would break this rule?
Where did this sand come from?
- Read the pie for a sample near a mountain belt.
- Read one on a passive margin far from mountains.
- Describe the difference without using the words "lag time".
If you dated the sand on your nearest beach, what would the pie look like?