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Placement of Publication of
GSA TODAY | MARCH/APRIL 2016 Figure 3. Top of golden spike emplaced in bed that is the Global Standard
Stratotype Section and Point (GSSP) for the Thanetian Stage. Length of “rock
hammer” is 5 cm.
They are regarded as international geostandards, and their protec-
tion and future scientific study are encouraged. Each one serves as
the primary definition of a boundary, which is the succession of
stratigraphic signals in a boundary interval and the single signal at
the stratigraphic level at which the boundary is placed. Locating
the boundary in stratigraphic successions elsewhere is an interpre-
tation made to the standard reference, the GSSP, after evaluation
of all stratigraphic signals. The formal process of ratification of a
GSSP (Fig. 4) begins with preparation of a written proposal by a
working group comprised of specialists on the boundary interval.
Development of a formal proposal requires extensive investiga-
tions of candidate stratotype sections and boundary levels world-
wide. Following consensus approval of a proposal by the working
group, it is then considered by the voting members of the relevant
ICS subcommission. If approved by the subcommission, the
proposal is forwarded to the ICS executive for consideration and
voting by the ICS executive and the chairs of the 16 subcommis-
sions. If approved at this level, the proposal is forwarded to the
IUGS Executive Committee for ratification. Following ratifica-
tion, the GSSP proposal must be published and posted on the ICS
website, and the GSSP must be marked. The rigorous criteria on
which a GSSP proposal is evaluated and the several levels of evalu-
ation and consideration by which it is approved and ratified give
validity and authority to ratified GSSPs as international
geostandards.
A geochronologic unit (period, epoch, age) is the time interval
during which the strata of a chronostratigraphic unit accumulated
(Salvador, 1994). Geologic and biologic events and settings of the
past, recorded in and interpreted from the rock record, are
expressed in terms of geochronologic units. Once two successive
GSSPs have been ratified, all the rocks that can be correlated to
levels between the GSSPs are the stratigraphic record from which
past events in Earth’s history are interpreted for that interval of
time. Geochronologic terms yield a relative geologic time scale,
and calibrated ages make up a numerical geologic time scale.
Calibrated numerical ages do not define the boundaries; they are
subject to refinement and recalibration. It is the GSSP, a specific
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marker proposal
If ratified
IUGS Executive Committee
If ≥60% majority yes vote
ICS Bureau: ICS Executive + all Subcommission Chairs
If ≥60% majority yes vote
Subcommission
Working Group
GSSP Proposal: section and point
Figure 4. Workflow for approval and ratification of a Global Standard
Stratotype Section and Point (GSSP) proposal. Extensive discussion and
evaluation occurs at the level of the working group, subcommission, and
International Commission on Stratigraphy (ICS) Bureau. If approved at these
successive levels, a proposal is forwarded to the International Union of
Geological Sciences (IUGS) for ratification. This process is also followed for
other ICS decisions on standardization, such as approval of names of formal
units, of revisions to the units, and to revision or replacement of GSSPs.
stratigraphic level in a stratotype section, that defines the boundary
and to which numerical ages are calibrated to varying degrees
of certainty.
THE ANTHROPOCENE
The term Anthropocene is widely used. In its latest iteration, it
refers to the present, when human impact on Earth’s surface, atmo-
sphere, and hydrosphere has been deemed to be global. International
organizations; national, regional, and local governments; non-
governmental organizations; and industries have taken steps to
mitigate and remediate the impact where its nature is judged to be
deleterious. Nevertheless, human impact is immense and potentially
increasing. But, the question is: Should the Anthropocene be
approved by the ICS and ratified by the IUGS as an official unit of
the ICS International Chronostratigraphic Chart?
STRATIGRAPHIC RECORD OF THE ANTHROPOCENE
In contrast to all other units of the ICS chart, the concept of
the Anthropocene did not derive from the stratigraphic record.
It arose with Paul Crutzen (2002), a Nobel Laureate in Chemistry,
who suggested that because of a greatly increased human impact
on the Earth system, we had entered a new epoch, for which he
proposed the term Anthropocene. Zalasiewicz et al. (2008)
considered the effects referred to by Crutzen and raised the ques-
tion of whether the effects justified the need for a new term, and
if so, where and how its boundary might be placed. The ICS
Subcommission on Quaternary Stratigraphy established a