Charles Lyell, Historian of Time's Cycle - Time's Arrow, Time's Cycle: Myth and Metaphor in the Discovery of Geological Time - page 157

rather than sheets, then we cannot unravel them by superposition. (Many
Tertiary strata are, for example, impersistent stream channels rather than
broad sheets of shallow oceanic sediments so common in the Mesozoic.) And
if strata are confined to isolated local basins, then we cannot correlate them
easily from place to place.
Since Tertiary times had been marked by increasing continentality in Europe
(recall Lyell's second substantive argument; see pages 139-141), marine
sediments were deposited in shifting, isolated embayments, not as favored
broad sheets. Thus, Tertiary strata were a challenge to the stratigraphic
program, not its premier example, as logic (without history's peculiarities)
might have dictated. They were also something of an embarrassment, since a
good technique should snare its potentially easiest reward without difficulty.
Lyell therefore decided to bag the Tertiary with a different method, based on
his distinctive vision of time's cycle. Success would crown his abstract vision
as weighed in the empirical balance and found triumphant.
In the face of such difficult stratigraphy, fossil remains would unlock the
Tertiary sequence. The stratigraphic research program had congealed about
the paleontological criterion of temporal ordering. A chronometer of history
has one, and only one, rigid requirement—something must be found that
changes in a recognizable and irreversible way through time, so that each
historical moment bears a distinctive signature. Geologists had long
appreciated this principle in the abstract, but had not found a workable
criterion. Werner and the Neptunians had tried to use rocks themselves,
arguing that a distinctive suite "of compositions and densities had
precipitated in temporal sequence from a universal ocean. This idea was
sound in logic, but didn't work in practice because the earth's strata were not
deposited in order of density from one ocean in one great era of precipitation.
Moreover, rocks are simple physical objects formed by chemical laws and, as
such, do not bear distinctive temporal signatures. Quartz is quartz—
conjoined tetrahedra with a silicon ion in the center, surrounded by four
oxygen ions, each