Geology Reference
In-Depth Information
Geological
Holmes' ages
Geological
Age range
period 1911
(millions of
period today
today (millions
years)
of years)
Carboniferous
340
Lower Carboniferous
362-330
Devonian
370
Upper Devonian
380-362
Silurian or Ordovician
430
Silurian
443-418
Precambrian
in:Precambrian
Late Proterozoic
900-544
1025
1270
Sweden
Middle Proterozoic
1600-900
1310
1435
United States
Middle Proterozoic
1600-900
Ceylon
1640
Early Proterozoic
2500-1600
Holmes' first geological time scale.
The correspondence of Holmes' values with those of today is
remarkable, given the limitations of the techniques available to
him in 1911.
with considerable suspicion. One of the foremost American
geologists of the time, George Becker, had recently published
his
Age of the Earth
, concluding, after having reviewed all the evi-
dence provided by the various hour glass methods, that the age
of the Earth 'must be between 70 and 55 million years', and that
consequently 'radioactive minerals cannot have the great ages
which have been attributed to them'. In similar vein John Joly,
in a serious attempt to reconcile radiometric ages with those
obtained from the sedimentary record, found it impossible to
accept the incredibly slow rates of deposition inferred by the
radioactive dates:
If the recorded depths of sediments have taken 1400 million years to
collect, the average rate has been no more than one foot in 4000 years!
This seems incredible: and if we double the depth of maximum sedimen-
tation it still remains incredible. But, if possible, still more incredible is
