Page 37 - Introduction to Paleobiology and The Fossil Record

24 INTRODUCTION TO PALEOBIOLOGY AND THE FOSSIL RECORD

(a)

Top
poorly consolidated
Tertiary molasse
Tertiary eroded from rising
Alpine belt
cover sequence
Secondary of Mesozoic
sediment folded
during Alpine orogeny
Primary
Base Variscan
basement of
granites and
(b) metamorphics

Marl
Clay
Snowdon Mountains Coal vales Stonebrash vales Chalk Plains
tract
hills
hills
Arenig Aran Vawddry
Longmont Brown Clee
Snowdon Range
Caernarvon Dolgelle Llanfair Abberley Hills Broadway Witney Wendover Beaconsfield London
Berwyn Range
Killas Slate and Coal Worcester Blue Oolites Clunch Chalk Sands and
London Clay
other strata Red Rhab Measures Marl Lias Marl Clay Brickearth
Red
and Dunstone
(c)
Figure 2.1 (a) Steno’s series of diagrams illustrating the deposition of strata, their erosion and
subsequent collapse (25, 24 and 23) followed by deposition of further successions (22, 21 and 20).
These diagrams demonstrate not only superposition but also the concept of unconformity. (b) Giovanni
Arduino’s primary, secondary and tertiary systems, first described from the Apennines of northern Italy

in 1760. These divisions were built on the basis of Steno’s Law of Superposition of Strata. (c) Idealized
sketch of William Smith’s geological traverse from London to Wales; this traverse formed the template
for the first geological map of England and Wales. Data assembled during this horse-back survey were

instrumental in the formulation of the Law of Correlation by Fossils. (a, from Steno 1669; c, based on
Sheppard, T. 1917. Proc. Yorks. Geol. Soc. 19.)

succeeding the Cretaceous (Fig. 2.1b). These There is now a range of different types of
three divisions were used widely to describe stratigraphies based on, for example, lithol-
rock successions elsewhere in Europe showing ogy (lithostratigraphy), fossils (biostratigra-
the same patterns, but these three systems phy), tectonic units, such as thrust sheets
were not necessarily the time correlatives of (tectonostratigraphy), magnetic polarity
the type succession in the Apennines. (magnetostratigraphy), chemical composi-