Carbon dating is only valid for less than 50,000 years - there are other methods of dating past the 50,000 year mark. Like for volcanic eruptions argon 49 decay test.
Anyone who claims to use carbon dating is putting you on.
Dating ancient sediment involves using radiometric methods based on the natural radioactive decay of certain elements such as potassium and carbon. Geologists also use other methods - such as electron spin resonance and thermoluminescence.
See my post 14.