Environmental Engineering Reference
In-Depth Information
Quaternary period it is essential to refer to sedimentary records of outcrops and
cores from the Mediterranean region and to the long sedimentary sequences of lakes
in Greece, Albania/Macedonia, Italy, Israel and southeast France. There is much
more local evidence for environmental change during the last glacial period and the
Holocene, that is, the last 100 000 years in the Mediterranean mountains. Much of
this comprises glacial deposits and landforms, which are examined by Hughes (see
Chapter 3) and to which only brief reference will be made here. In addition there
are numerous palaeoecological investigations of lake sediments and peats that relate
to the last 12 000-10 000 years. Pollen analysis in particular has been widely used
to reconstruct Holocene vegetation communities in these upland mainland regions
and in the Mediterranean Islands (see Mannion, 2008; Rackham, 2008, for reviews
of the latter).
2.2 The pre-Quaternary period
Towards the end of its 50
×
10
6
year existence the supercontinent of Pangea be-
gan to fracture, c. 200
10
6
years ago. The Atlantic Ocean came into existence as
the Americas moved westwards, while an extensive waterbody, the Tethys Ocean,
formed between the separating African and Eurasian plates. By c. 120
×
10
6
years
ago those same plates began to converge, gradually reducing the extent of the Tethys
so that only a remnant was present by 40
×
10
6
years ago. This was the Mediter-
ranean Sea. By this time the converging plates had also caused the uplift of sedi-
ments around the edge of the basin to produce the Mediterranean mountains, dis-
cussed herein, as well as the Alps. Denudation processes operative on land produced
sediment, which was deposited first in the Tethys Ocean and then in the Mediter-
ranean Sea. As these sediments consolidated they encapsulated physical, chemical
and biological components that reflected environmental conditions at the time of
deposition. The particle size, mineral and organic contents of the sediments (e.g.
black shales or sapropels) plus the remains of organisms such as foraminifera, os-
tracods, diatoms, radiolarians, coccolithophores, pollen grains and marine molluscs
all contribute to understanding past environmental change; chemical signatures in
the fossils, especially foraminifera, include oxygen isotopes, which have facilitated
the construction of stratigraphies for correlation between cores and for sea surface
temperature reconstruction (see Mannion, 1999; Anderson
et al.,
2007, for details
about theory, method and applications). Thus marine sediment cores plus a number
of uplifted sediments that are now dry land provide evidence on which to examine
late Tertiary and Quaternary environmental change in the region as a whole.
Of particular significance is the Messinian Salinity Crisis (see CIESM, 2008, for
a recent review of this contentious issue), which occurred c. 6
×
10
6
years ago. This
involved closure of the link between the Atlantic Ocean and the Mediterranean Sea,
that is, in the area of the Gibraltar arc (Warny
et al.,
2003), either due to volcanic
activity (Duggen
et al.,
2003) or through tectonic uplift (Jolivet
et al.,
2006) but
not because of climatic change (Fauquette
et al.,
2006). Erosion causing fluvial
×
