Recolonisation theory differs from the standard view of Earth history in two respects. One concerns the interpretation of the fossil record, the other the length of time over which that history was played out. In both cases the response has been to argue that the rock record is incomplete – even in places where sedimentation appears to have been continuous.
This cannot be the most comfortable of positions. In the following articles (click on the headings for links or use the panel left) we show how it is possible to test the geological timescale and generally take a less dogmatic stance on questions of age. The paragraphs below give summaries.
How does one date the coming into existence of anything? In the case of the solar system, there are two approaches. One rests on the observation that stars, like animals, go through a cycle of birth, youth, middle age, old age and death. Thus, if we could quantify how long a star the size of the Sun takes to go through such a cycle and determine what stage the Sun is at now, we could estimate the solar system’s age. That would require determining the proportion of hydrogen to helium and then calculating how long it would take for nuclear fusion to convert one into the other. Not surprisingly, the proportion cannot be reliably quantified, because most of the helium lies in the core and estimates based on spectroscopy are only as good as models describing how the interior convects.
A potentially more accurate approach is to assume that meteorites date back to the beginning of the solar system. In an article setting out the limits of solar modelling Christensen-Dalsgaard et al state,
The age of the sun, since the onset of core hydrogen burning, is estimated at (4.52 ± 0.04) x 109 years .
Science 272:1286-92 (1996)
Four and a half billion years. The crucial point here is the footnote:
 The age of the sun can be estimated from the ages, obtained from radioactive dating, of the oldest meteorites. G. J. Wasserburg [ref.] obtained a meteoritic age of (4.57 ± 0.01) x 109 years.
In other words, the approach is only as good as the assumption that meteorites are the remains of an original solar nebula. As discussed elsewhere, most meteorites do not conform to that assumption and it doubtful whether any do. They are probably the remains of shattered planets.
If Earth had a natural origin, it too must have accreted from a solar nebula. However, its origin cannot be dated for the simple reason that all its oldest rocks have been swallowed into the mantle. There is thus nothing from that earliest time to investigate, and to attribute to it a natural origin is a matter of philosophical world-view. The Earth cannot be directly dated.
Its age is put at 4.55 billion years – 500 million years earlier than its oldest surviving rocks – on the three-fold assumption that (i) it must be the same age as meteorites, (ii) meteorites are the remains of a cloud of dust and gas from which the whole solar system was born, and (iii) the rate of radioactive decay has always been the same. Clues in the rocks themselves suggest a younger age – a point that geologists were acutely aware of before the 1950s, when radioisotope dating was in its infancy. This in-depth article looks at the time required to account for the chalk beds of the Cretaceous, a period allocated 80 million years on the geological timescale. Sedimentation rates appear to have been thousands of times faster than those required by radioisotope dating.
This short discussion, based on outcrops from the Isle of Wight, provides photographic illustrations for the preceding article.
It is often the most obvious features that get overlooked. Two obvious facts about chalk-marl sequences are: (i) that the animals that burrowed through them, leaving traces that can still be seen, did not homogenise the differently coloured beds into a monotonous, unbedded grey, and (ii) that some of the body fossils are quite well preserved. The beds must therefore have accumulated rapidly, consistent with the interpretation that each chalk-marl couplet reflects the warm-cool cycle of one year, not the much longer astronomical cycles (at least 20,000 times longer) postulated by geologists unwilling to question the standard timescale. Such a rate would still be less than one metre a year.
The challenge of tidal beds
Orthodox geology will not countenance any interpretation which calls its timescale of billions of years into question. Where possible, it will call upon astronomical cycles 20,000 or 40,000 years long to explain rhythmic bedding, regardless of the burrowing evidence. However, some beds reflect a type of cyclicity where only one interpretation is possible, and it must be accepted that sedimentation rates were very much faster: the ebb and flow of tides, expressed in herring-bone cross-bedding, packages of silt-mud couplets and rhythmic laminae. There is, of course, nothing catastrophic about the work of tides. This was normal, background sedimentation. Yet rates of accumulation were up to 4 metres a year: up to 100,000 times faster than isotope dating indicates. The interpretation of chalk beds as annual deposits is thus wholly in keeping with the way tidal beds are uncontroversially interpreted.
There are many examples of tidal beds throughout the geological record. This one may be found in the European Geopark around the town of Dignes-les-Bains, in Haute Provence. A roadside exposure some 70 metres thick preserves beds that took around 6 years to accumulate.
Limestone/marl couplets are common in Jurassic as well as Cretaceous successions, and are susceptible to much the same explanation. The preservation of the bedding planes and of the fossils within the beds suggest deposition rates orders of magnitude faster than those assumed. However, whether the marls were the product of winter rains or summer depends on the climate and hence the latitude. Britain’s Dorset coast – a World Heritage Site – is as good a place as anywhere to study Jurassic deposits, but at that time Britain lay in the tropics. Consequently, as in tropical regions today, the wettest season was the summer. The annual cyclicity reflected by the alternating limestones and marls was that of winter and summer rather than the other way round.
A fundamentalist approach to the book of Genesis reads it as originating in a literate culture little different from our own. Only ten generations are recorded between Adam and Noah, plus a further ten between Noah and Abraham. Since the genealogies record the age at which the father gave birth to the next in line, it is argued, the genealogies can – indeed must – be taken as complete, and equivalent to a chronology going all the way back to Creation. Linked to the fairly well-established date of Solomon’s accession c. 971 BC, they allow us to date the Flood to around 2500 BC – or even 2300 BC if Israel’s sojourn in Egypt was only 215 years (as per Gal 3:17). So is the credibility of the Bible undermined by its most ardent defenders.
In reality, however, the genealogies from Adam to Abraham originated in an oral culture. While they might initially have included a chronological function, their main purpose was to define the identity of the individual in relation to his forbears. As time went on, the chronological function became impossible to maintain; to remain manageable, the lists had to be repeatedly trimmed. Thus, while Genesis indicates that man was in existence from the beginning, it does not allow us to say when that beginning was.