context: Since 7500 yr ago, a situation with tides and currents, very similar to present has existed. Rates of sea-level rise had dropped so far, that natural sedimentation by the Rhine and coastal processes together, could compensate the transgression by the sea; in the last 7000 years, the coast line was roughly at the same location. In the southern North Sea, due to ongoing tectonic subsidence, the sea level is still rising, at the rate of about 1–3 cm (0.39–1.18 in) per century (1 metre or 39 inches in last 3000 years).
question: How old is the North Sea?