IGCP Board; 10th session; Report of the ... - unesdoc - Unesco

Activities planned. A working group meeting is
being proposed by the Mineral Resources Section
of ESCAP, to be held sometime in 1982,
however funding is uncertain and the proposal is
mainly to get an agreement in principle to hold
one. The meeting would review a work programme
on correlation between basins; and with respect
to all proposed activities, components covering
economics, resources, and training.
Contributions to the atlas are expected from
Afghanistan, China, Korea, and Vietnam and
further contributions are likely from Australia
and India; and it is envisaged that another volume
of the atlas can be produced.
The immediate future will see the publication of
the third volume of the Atlas.
No. 41 NEOGENE-QUATERNARY BOUNDARY
K. V. Nikiforova, Geological Institute, USSR
Academy of Sciences, Pyzhevsky per. 7,
109017 Moscow, USSR.
Description. Complex study of biostratigraphy,
magnetostratigraphy, radiometric-age determination,
etc., and correlation of Pliocene and
Lower Quaternary marine and continental deposits
on a global scale. Stratigraphie and palaeomagnetic
study of the Neogene-Quaternary
boundary stratotype.
Summary of activities. The state-of-the-art of
the N/Q boundary study can be summarized
briefly as follows:
At present there are four main proposals
on the position of the N/Q boundary:
(1) at the base of the Plaisance-Astian of the
Italian sequences, corresponding in the continental
facies to the Late Rustsinian (Charnotian)
and Early Villafranchian of West Europe; coinciding
in the oceanic sequences with the base of
the Globorotalia miocenica zone and the lower
boundary of the Gilbert palaeomagnetic zone
(about 3.3 Ma); (2) at the base of the Middle
Villafranchian of West Europe, near the Gauss-
Matuyama epoch boundary (about 2. 4-2. 5 Ma);
(3) at the base of the Calabrian of Italy, with
Arctic immigrants in the fauna of molluscs and
foraminifers: corresponding to the base of the
Upper Villafranchian in the continental facies of
• West Europe and the base of Globorotalia truncatulinoides
zone in the oceanic sequences; within
or near the Olduvai palaeomagnetic episode
(1. 91-1.72 Ma); (4) at the base of the Cromerian
of West Europe, near the Matuyama-
Brunhes epoch boundary (about 0. 7 Ma).
In addition, some scientists think that the N/Q
boundary coincides with the Kaena episode of
the Gauss palaeomagnetic epoch (2.8 Ma).
The Quaternary system should be taxonomically
equal toother Phanerozoic systems, and thus
22
its lower boundary should be defined in conformity
with general stratigraphie principles. It should
have a stratigraphie substantiation, based first of all
on marine fauna changes; detailed correlation with
the Quaternary established in marine deposits is
then required for establishing the boundary in the
continental sequences, based on palaeontological,
climatostratigraphical and magnetostratigraphical
data, isotope-oxygen analysis and radiometric dating.
Its stratotypical section should be universal, timefixed
standard, which can be traced globally.
The base of the G. tosaensis zone does not have
any correspondent marker in the palaeomagnetic
scale, and therefore is unsuitable for broad correlation.
The base of the Middle Villafranchian
of West Europe passes inside the G. miocenica
zone and thus can not be identified in the oceanic
deposits. Moreover, the base of the Cromerian
lies near the Matuyama-Brunhes boundary inside
the G_. truncatulinoides and, not coinciding with
any subzone boundary, also will be lost in the
oceanic sequences.
Hence, among the aforementioned four proposals
only two bases can qualify for the final selection
of the N/Q boundary: the base of the G. miocenica
zone (boundary of the Gilbert-Gauss palaeomagnetic
epochs, 3. 3 Ma) and the base of the G.
truncatulinoides zone (near the base of the Olduvai
palaeomagnetic event, about 1.9 Ma). The
latter, coinciding with the base of the Calabrian
layers of Italy, which is recommended by the IGC
and accepted by most of the countries as the standard,
has been considered by the majority of
scientists concerned to be the suitable N/Q boundary.
The Vrica section was proposed by the Italian
scientists in 1975 for the N/Q boundary stratotype
and was approved preliminarily by the Project
WorkingGroup and the INQUA Subcommission on
the Pliocene-Pleistocene boundary. The final
solution to this problem should be adopted by the
Project WorkingGroup at the XI INQUA Congress,
which is to be held in Moscow, in 1982, and
should then be submitted for approval to the 27th
IGC which will take place in Moscow in 1984.
In 1981, an international meeting of the Project,
followed by a field excursion to the Pliocene-
Quaternary key sections in Arizona and California,
was held in Tuscon, Arizona, USA from
28 March to 5 April. It was organized jointly
with IGCP Project 128 "Late Cenozoic Magnetostratigraphy"
and the INQUA Subcommission on
Pliocene-Pleistocene boundary. Thirty-six
scientists from 10 countries attended the session.
The complete record of climatic, sedimentary
and tectonic changes of the marine and non-marine
sediments was studied. The planktonic microfossil
biostratigraphy, vertebrate palaeontology,
radiometric dates and magnetostratigraphy made
it possible for a correlation to be made between
marine and terrestrial sequences of the continental
margin of the western part of the USA. The urgent
necessity for studies on the Vrica potential strato-