Download Stratigraphy PDF

TitleStratigraphy
TagsStratigraphy Sedimentary Rock Geology Fossil Plate Tectonics
File Size20.2 MB
Total Pages192
Document Text Contents
Page 96

Precambrian Time 89

Fig. 64. Simplified mantle plume model for the origin and growth of primitive continental
crust. Arrows denote movements of convection (Kroner 1984, after Condie 1980)

Inner or telluric planets
Outer or gaseous planets

(and satellites)

Mercury
and Moon

Venus Earth Mars Jupiter Saturn Uranus Neptune

N2

O2

CO2

CO

H2O

H2

He

Ne

A

NH3 ----
CH4

Fig. 65. Principal atmospheric constituents of the planets in the solar system

temperatures at the surface (70-100°C in the oceans). The Earth is at the
moment the only inner planet to still have small amounts of the lighter
elements (hydrogen, helium). It has also been able to retain its nitrogen
derived from the dissociation of ammonia under the influence of solar

Page 97

90 The Major Stages of Earth History

radiation. The presence of free oxygen in large quantities, a condition
specific to the Earth, is due principally to the photosynthetic activity of
plants (see below), and slightly to the photo-dissociation of CO2 and H20
by UV radiation. In the high atmosphere, an ozone (03) layer makes a
protective screen against UV radiation.

Whatever the hypothesis for the origin of dissolved salts in seawater,
and their proportions, no real idea of the composition of primitive seawater
yet exists. It was probably very acid because of the very large quantities of
CO2 dissolved in it and the presence of strong acids. It was in this perhaps
ubiquitous oceanic environment, already containing most of the salts we find
today (except sulphates) and in the presence of a reducing atmosphere, that
the first organic compounds were synthesized. Later, by about 3500 m. y. or
earlier, these would lead to the emergence of life. Soils may also have
played a role in this emergence.

This first period corresponds to the Katarchean of Salop (1979, 1983). It
terminates, according to this author, with the Saamian orogeny (3750-
3500m.y.) characterized by deformations, plutonic and hypabyssal intru-
sions and metamorphism.

1.4.3 From the Archean to the Eocambrian:
the Establishment of a Dynamic System

1.4.3.1 Internal Dynamics
In the Archean, the first evidence of lithospheric activity is seen in the
greenstone belts i.e. the zones of sediments and volcanics, folded and
metamorphosed (chlorite, epidote, serpentine) with gneisses and granitic
plutons. The greenstones represent the fillings of old basins, and some
authors interpret them as the product of intraoceanic or marginal subduc-
tions analogous to those of the Phanerozoic. Others, like Kroner (1983a,
1984), propose an ensialic origin linked to continental rifting (Fig. 66); in
fact, the existence since 3600m.y. of fragments of continental crust up to
several hundred kilometers across is generally acknowledged. At point or
linear hot spots the still unstable crust broke up, thinned, and then sank
along elongate grabens widened by the classic mechanisms of tilted blocks.
Continental basins were so created and became filled with sediments and
essentially basaltic basic igneous rocks! from partial melting of the upper
mantle. Crustal melting can also lead to granitoid intrusions.

If the crust breaks completely, small oceanic basins appear. Their
closure, after disappearance of the point or linear hot spots, results in
deformation of the basin filling as recumbent folds and thrust faults.

In total, the formation of greenstone belts results in an enlargement of
continental crust as well as its thickening by magmatic differentiation and

1 In the Archean, many lavas were peridotitic komatiites derived from the deep mantle.
These types disappear in the Proterozoic.

Page 191

186

Ensialic tectonism 91, 121
Environment 5,26,65,66
Eocambrian 82, 84
Era 17
Erosion 77, 78
Eustasy 43, 44, 72, 78-81, 109, 143, 168
Evaporite 55, 96, 99, 111-113, 124, 125,

127, 128, 130, 146-149, 164
Event 1,3-5, 15, 16,55
Evolutive cartography 75

Facies 11, 12
Faunal barriers 27, 104, 105
- migration 5, 11
- Province 11, 67, 105
- renewal 17, 133
Fenno-Sarmatia 103
Flysch 92, 99, 106, 166
Formation 7, 8
Franciscan Basin 137, 139, 154

Geochronology 3, 12, 20
Glaciation 77,80,96,97,113,123-125,

129, 130, 167, 170
Glauconite 22
Global map 72
- Revolution 13, 35
Glossopteris 129, 131
Gneissic dome 94 - 95
Gondwana 92, 115, 129-131, 142, 148
Greenstone Belt 90
Grenville Belt 90, 92, 93
Griotte Marble 120
Group 7

Heat Flow 76, 77, 93, 100
Hellenides 147, 153, 158, 160
Hercynian Orogeny 100
Hercynides 119, 121
Himalaya 121, 159, 162
Hydrosphere 87, 90
Hypostratotype 33, 34

Iapetus 103
Ibero-Corso-Sardinian block 142, 157
Index fossil 10, 26
Indian Ocean 137
Indosinian Suture 135
Intercontinental bridge 72
Interprovincial exchange 78
Interval Zone 31
Iridium 143
Isochronism 4, 16, 43, 44
Isopic Map 65
Isostatic adjustment 77, 169, 170
Isotopic Age 21

- Stage 51
Israelski principle 43

Jasper 99
Jura 158, 160, 161
Jurassic 79, 134, 145

Karroo Formation 149

Lance Formation 149

Subject Index

Laramide Phase 80, 133, 140, 143, 156
Lateral continuity 3
Life assemblage 27
Liguro-Piemontais Ocean 136, 137
Lithoclinal sequence 42
Lithofacies 65
Lithohorizon 3
Lithomarker 35
Lower Continental beds 130

Maghrebids 148, 153
Magnetic anomaly 58-61
- reversal 56-58
Magnetozone 58
Mantle 88, 89
Marathon Mountains 122
Marl-Limestone alternation 44, 47
Mauritanides 118, 121
Mediterranean 159, 160, 161, 165, 166
Melanges 104, 107
Member 7
Meteorite 62, 82, 87, 94, 170
Michigan Basin 111
Microcontinent 106, 116
Middle Cretaceous Crisis 151
Mid-Oceanic ridge 77, 80
Milankovitch cycle 170
Mineral markers 47-49
Molasse 98, 127, 165, 166
Morrison Formation 148

Neocimerian Phase 138
Neogene 155, 159, 164
Neotectonism 164
Neotethys 135, 136
Nevadian Phase 80, 134, 137
New Red Sandstones 125, 130
North Sea 139, 158, 163
Nubian Sandstones 148
Numerical Age 31

Old Red Sandstones 114, 118, 124, 127, 130
Ophiolite 92, 120, 137, 141, 158
Ophite 136
Orbital Cycles 46
Ordovician 102, 107, 109-112

Page 192

Subject Index

Orogenic cycles 84
- Phase 15
Overlapping Range Zone 30

Pacific Ocean 137, 143, 158, 159, 168
Palatine Phase 133
Paleobiogeography 64, 67, 105
Paleocirculation 73, 75
Paleogene 156, 163, 167
Paleogeography 3
Paleomagnetism 72, 81, 102
Paleotethys 103, 118, 122, 127, 135
Palinspastic Map 70
Pan-African Orogeny 92, 95
Pangea 16, 76, 80, 92, 105, 114, 115, 128,

129
Paradox Basin 122
Paratethys 165
Passive margins 104, 152, 164
Permian 115, 128, 130
Permo-lrias 134
Phanerozoic 10, 17,83,88
Phyletic gradualism 31
Phylozone 30
Planets 82, 88, 89
Plate-tectonics 5, 87, 92, 100, 102, 121, 122,

158
Polar Wandering 81,82, 103, 123-125,

145
Principle of superposition 2, 85
Proterozoic 83, 91, 92, 94
Protoatlantic 103 -105, 108, 115
Protogondwana 102
Provincialism 11, 129, 131
Purbeckian 144
Pyrenean-Provencal Phase 158
Pyrenees 153, 158

Quaternary 155, 159, 168

Radiochronology 20-23, 85
Radiometric Age 21
Range zone 30
Rangitata Phase 138
Red Beds 86, 96, 99, 112
- Sandstones 65
- Sea 159
Reefs 111, 112, 127, 145
Remanent magnetism 56-58
Rhythm stratigraphy 42
Rocky Mountains 140, 158, 161, 164

Saalian phase 121

Saamian Orogeny 90
Salinity Crisis 160, 165
Sapropel 55, 66
Sardinian Phase 108, 113
Sedimentary rhythm 20, 37
Sedimentation 77, 78
Seismic method 38, 43
Sequence Stratigraphy 42-44
Shield 85, 86
Shoreline 70-72
Silinic Disturbance 108
Silurian 102, 108, 109, 111, 112
Stage 17
Stratotype 7, 13, 33-35
Stromatolite 85, 99, 110, 111
Subsidence 76
Sudetic Phase 121
Sundance Sea 144, 148
Suspect Thrranes 140
Synsedimentary tectonics 16
System 17

'Thchytely 10
Thconic Phase 107, 109, 113
Thphrostratigraphy 48
Thrminal Continental 164
Tethyan Province 67, 145
Tethys 12,132,135-139,141,144-146,

153, 158, 159, 163, 168
Tigillite Sandstones 111
Tillite 96-98
Time correlation 10
Tonstein 41, 48, 130
Torridonian 105
nace elements 51
lrias 3,48,65, 135, 145-147

Unconformable surface 41
Uniformitarianism 35, 49, 85, 86
Unitary association 32
Urals 115

Varve 20,47
Vocontian Basin 45-47, 151
Volcanism 108, 129, 135, 143, 155, 158,

160, 170

Wealdian 144, 151
Well logging 39-42
Wilson cycle 76, 79, 92

Zagros Chain 161
Zechstein Sea 127, 128

187

Similer Documents