Nils Axel Morner: Neotectonics and the recent ice ages

My thanks to Hans Jelbring, who has sent me a copy of a paper by Nils Axel Morner. The paper introduces the concept of ‘Neotectonics’ and defines the epoch as beginning around 3M years ago, when we entered the current run of glacial interglacial cycles. Nils proposes the hypothesis that movements of the tectonic plates, especially in the uplift of mountainous plateaux and the closing of the strait between South america and Antarctica, amplified the effects of Milankovitch orbital cycles and resulted in a fall in Earth’s average surface temperature. I’ve provided a few excerpts here, but be sure to download and read the whole paper, it reads easily and isn’t too long.

Neotectonics, the new global tectonic regime during the last 3 ma and the initiation of ice ages
NILS -AXEL MÖRNER

Paleogeophysics & Geodynamics, S-10691 Stockholm, Sweden

Abstract
It recently became evident that the globe experienced a significantly changed tectonic
regiment from about 3.0 Ma onwards. This puts the term “neotectonics” in quite a new
perspective. We are now able to identify the last 3 Ma as characterized by generally
intensified tectonic activity. This period may hence be looked upon as a special
“neotectonic period”. Large areas were rapidly uplifted between 3.0 and 2.5 Ma. This led
to a seemingly more general lowering of the ocean floor due to an adjustment of the
geoid-oceanoid level. The tectonic reorganization 3.0-2.5 Ma ago led to the initiation of
global ice ages, the first one of which occurred at about 2.3 Ma.

Introduction
The term “neotectonics” originates from Russina nomenclature (Mescherikov, 1968;
Fairbridge, 1981), where it was used to denote crustal movements during the Neogene
and Quaternary periods (i.e. from the Miocene onwards). In the rest of the world the
term has been used to denote upper Cenozoic young and on-going tectonics (Mörner,
1989; INQUA 1978–1993; Vita-Finzi, 1986), or the period when tectonic conditions of
present-day-typ began (Mörner, 1989). In most cases, there were no real grounds for
separating a general lower boundary at which “neotectonics” could be said to have
commenced globally. In the Mediterranian region, however, a new prevailing tectonic
regiment seemed to have begun at about 3.0-2.5 Ma ago when the northward push of the

African plate seemed to have been significantly intensified inducing new tectonic
conditions not only within the Mediteranian region but also far up in northern Europe
(Mörner, 1989, 1986, 1987a). In a global context, the time base for a meaningful
application of the term “neotectonics” seemed to vary greatly over the globe and rather be
of local to regional character.

In recent years, the picture has changed rapidly and significantly. We are now able to
identify a thoroughly revised senario which puts the term “neotectonics” in quite new
perspectives.

Download and read the full paper.