12 Introduction
mation of the theory of sea-floor spreading: sediments overlying the "basement"
basalt showed the exact age predicred by the geophysicists from counting magnetic
anomalies (Fig. 1.18). Occasionally, sediments were somewhat younger, which
means that the basaltic rock was bare for a while, before it collected sediments. Other
major results were more subtle, but have had far-reaching implications for our understanding of the co-evolution of life and climate, and for the role of the ocean in
climatic change over long periods of time.
In the early years of deep-sea drilling, present sedimentation patterns were assumed to be static, so that changes down-core would be interpreted mainly in terms
of motions of the sea floor. It soon became clear, however, that the ocean's productivity changed markedly through geologic time, which produced large changes in sedimentation patterns. Also, it became evident that changes in ocean conditions (as
reflected in sediments) were quite sudden at certain times, and that such "steps" in
climatic change were associated with reorganizations of the marine biosphere, including extinctions and subsequent radiations. The most intriguing period in the ocean's
history, in this regard, proved to be the transition between the Cretaceous and the
Tertiary, which witnessed large-scale extinction of tropical planktonic organisms.
The importance of the deep-sea record for the reconstruction of Earth's history for
the last one hundred million years or so became obvious very quickly. The record on
land is patchy and incomplete by nature - land is eroded and delivers sediment to the
sea. This renders suspect all arguments about the pace of evolution that depend on a
continuous record. (Darwin pointed this out a long time ago). Only the record in the
deep ocean can promise complete sequences, and even here gaps prove to be quite
common in many settings. The gaps are not distributed randomly, but occur preferentially just where conditions change. This illustrates a certain obstinacy of the ocean in
yielding up the secrets of its history, something that many marine geologists have
come to appreciate.
One of the most notable aspects of deep-ocean drilling - now with the larger
drilling vessel JOIDES Resolution (Fig. 0.7) - is the creation of an international
community of marine geologists - hundreds of scientists from around the world who
were shipmates at one time or another, eagerly listening for the driller's call "core-ondeck", and sharing the thrill of exploring where nobody had gone before.
Further Reading
General Background
(least specialized literature first)
Press F, Siever R (1982) Earth, 3rd edn. Freeman, San Francisco
Emiliani C (1992) Planet Earth: cosmology, geology, and the evolution of life and environment.
Cambridge University Press
Glen W (1975) Continental drift and plate tectonics. Merrill, Columbus
Open University Course Team (1989) The ocean basins: their structure and evolution. Pergamon
Press. Oxford
mation of the theory of sea-floor spreading: sediments overlying the "basement"
basalt showed the exact age predicred by the geophysicists from counting magnetic
anomalies (Fig. 1.18). Occasionally, sediments were somewhat younger, which
means that the basaltic rock was bare for a while, before it collected sediments. Other
major results were more subtle, but have had far-reaching implications for our understanding of the co-evolution of life and climate, and for the role of the ocean in
climatic change over long periods of time.
In the early years of deep-sea drilling, present sedimentation patterns were assumed to be static, so that changes down-core would be interpreted mainly in terms
of motions of the sea floor. It soon became clear, however, that the ocean's productivity changed markedly through geologic time, which produced large changes in sedimentation patterns. Also, it became evident that changes in ocean conditions (as
reflected in sediments) were quite sudden at certain times, and that such "steps" in
climatic change were associated with reorganizations of the marine biosphere, including extinctions and subsequent radiations. The most intriguing period in the ocean's
history, in this regard, proved to be the transition between the Cretaceous and the
Tertiary, which witnessed large-scale extinction of tropical planktonic organisms.
The importance of the deep-sea record for the reconstruction of Earth's history for
the last one hundred million years or so became obvious very quickly. The record on
land is patchy and incomplete by nature - land is eroded and delivers sediment to the
sea. This renders suspect all arguments about the pace of evolution that depend on a
continuous record. (Darwin pointed this out a long time ago). Only the record in the
deep ocean can promise complete sequences, and even here gaps prove to be quite
common in many settings. The gaps are not distributed randomly, but occur preferentially just where conditions change. This illustrates a certain obstinacy of the ocean in
yielding up the secrets of its history, something that many marine geologists have
come to appreciate.
One of the most notable aspects of deep-ocean drilling - now with the larger
drilling vessel JOIDES Resolution (Fig. 0.7) - is the creation of an international
community of marine geologists - hundreds of scientists from around the world who
were shipmates at one time or another, eagerly listening for the driller's call "core-ondeck", and sharing the thrill of exploring where nobody had gone before.
Further Reading
General Background
(least specialized literature first)
Press F, Siever R (1982) Earth, 3rd edn. Freeman, San Francisco
Emiliani C (1992) Planet Earth: cosmology, geology, and the evolution of life and environment.
Cambridge University Press
Glen W (1975) Continental drift and plate tectonics. Merrill, Columbus
Open University Course Team (1989) The ocean basins: their structure and evolution. Pergamon
Press. Oxford