According to the post at https://en.wikipedia.org/wiki/Hallstatt_plateau … the Hallstatt Plateau is a term used in archaeology that refers to a flat area in radiocarbon dating (as opposed to calendar dates). The C4 methodology is said to be hampered by this huge plateau – the point where the calibration curve swings away from raw carbon dating. This concerns C14 dates clustering around 2450BP (before present), which always calibrate between 800 and 450BC, no matter the measurement precision involved in the laboratory. Archaeologists, we are told, are hampered by this plateau and dendrochronologists use wiggle matching to provide calendar dates – otherwise they would be stumped. The wiki entry quotes Peter James (historian), the author of Centuries of Darkness (1993) and Van der Plicht, Radiocarbon, the Calibration Curve (link provided by the Wiki).
The period 800-450BC overlaps with where Velikovsky placed his series of close encounters (relatively speaking) with Mars (probably a comet or meteors rather than a planet). Was there an injection of C14 into the atmosphere at this time which took 350 years to fall back down again – or was there a series of cosmic encounters that kept the plateau high. On the other hand, how many other plateaus occur in the past. Lots of them apparently. There was even a brief episode in the 13th century AD. One might imagine plateaus coinciding with catastrophic events (such as exploding meteors in the atmosphere) – at anomalous periods such as the end of Early Bronze, Middle Bronze and Late Bronze periods in western Asia – and going back further still into the Holocene at 5000 years ago and 8000 years etc. What is the situation at the Younger Dryas boundary? Do such events weaken the magnetosphere surrounding the Earth and allow more solar radiation to penetrate the atmosphere – and reach the surface. Has it anything to do with a hyper active Sun – or the reverse, an extended solar minimum? Or is the Hallstatt Plateau unique and may it reflect an error in the creation of the calibration curve? Was there a period where the years have been replicated, creating an anomaly, the error within tree rings (dated with the help of C14) and C14 (calibrated by those tree rings). Lots of possibilities. However, if the plateau is not unique one would wonder out loud if plateaus are more common than usually assumed (by the great and the good as much as by Joe Public).