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Classroom presentations to accompany Understanding Earth, 3rd edition:

Classroom presentations to accompany Understanding Earth , 3rd edition prepared by Peter Copeland and William Dupré University of Houston Chapter 7 Sediments and Sedimentary Rocks

Sediments and Sedimentary Rocks:

Sediments and Sedimentary Rocks Tom Bean/DRK

Processes of the rock cycle:

Processes of the rock cycle Weathering Erosion Transportation Deposition (sedimentation) Burial Diagenesis

Sedimentary Stages in the Rock Cycle:

Sedimentary Stages in the Rock Cycle Fig. 7.1

Sedimentary rock:

Sedimentary rock (a) Rock resulting from the consolidation of loose sediment that has been derived from previously existing rocks and accumulated in layers ( detrital or clastic ) (b) Rock formed by the precipitation of minerals from solution by either organic or inorganic processes ( chemical )

Sedimentary rocks:

Sedimentary rocks 5 % by volume of the upper crust 75% by area of continental areas Often the only record of geologic events: e.g. The Himalayas will someday be sandstone

Transport and deposition of clastic sediments:

Transport and deposition of clastic sediments Movement of sediment by wind, ice or water. Mode of transport produces distinctive deposits.

Transport affects the sediment in several ways:

Transport affects the sediment in several ways Sorting : measure of the variation in the range of grain sizes in a clastic rock or sediment Well-sorted sediments indicate that they have been subjected to prolonged water or wind action. Poorly-sorted sediments are either not far-removed from their source or deposited by glaciers.

Slide 10:

Sorting Well-sorted Poorly-sorted

Transport affects the sediment in several ways:

Transport affects the sediment in several ways Roundness : measure of how rounded the corners are Sphericity : measure of how much it is like a sphere Sorting, roundness, and sphericity all increase with amount of transport.

Well-sorted Sand:

Rex Elliott Fig. 7.2 Well-sorted Sand

Poorly-sorted Sand:

Poorly-sorted Sand Rex Elliott Fig. 7.2

Roundness and sphericity:

Roundness and sphericity Fig. 7.3

Types of detrital rocks :

Types of detrital rocks Largely based on the size of the particles, which may be anything. Conglomerate Breccia Sandstone (quartzite, arkose, greywacke) Shale Mudstone Siltstone

Sedimentary structures:

Sedimentary structures stratification = bedding = layering Produced due to differences in 1. size of particles 2. kinds of particles

Clues to interpreting sedimentary environment:

Clues to interpreting sedimentary environment • Sedimentary structures • Sorting, roundness, sphericity • Sequence of beds

Types of chemical sedimentary rocks :

Types of chemical sedimentary rocks Limestone CaCO 3 Chert SiO 2 Salt NaCl, KCl, K 2 SO 4 Gypsum CaSO 4 • 2H 2 O Coal altered organic debris

Chemical environments: Carbonates:

Chemical environments: Carbonates Clear water — away from big rivers (or volcanoes) Warm water — subtropical to tropical shallow water, two reasons: Organic : sunlight only penetrates to about 100 m Inorganic : CCD (dissolution CaCO 3 dependant on P )

Chemical environments: Evaporites:

Chemical environments: Evaporites Restricted environments (Mediterranean Sea, Texas coast) Minerals precipitate according to solubility. Gypsum Halite 50% 90% CaSO 4 •2H 2 O NaCl

Sedimentary structures:

Sedimentary structures Particular structural features can give information about the environment of deposition. Structures also help determine if a bed is right-side-up. — this is important in deformed rocks

Graded bedding:

Graded bedding Scale may be mm to m

Turbidity currents:

Turbidity currents Suspension of water, sand, and mud that moves downslope (often very rapidly) due to its greater density than that of the surrounding water (often triggered by earthquakes) Speed of turbidity currents first appreciated in 1920 — breaking of phone lines in the Atlantic; also gave indication of distance traveled by a single deposit

Other up indicators:

Other up indicators Cross-bedding Ripple marks Mudcracks Raindrop impressions Fossils (some may have been preserved in growth position)

From sediment to sedimentary rock (lithification):

From sediment to sedimentary rock (lithification) Compaction : reduces pore space Clays and muds are up to 60% water; 10% water after compaction. Cementation : chemical precipitation of mineral material between grains (SiO 2 , CaCO 3 , Fe 2 O 3 ) binds sediment into hard rock Recrystallization : P and T increase with burial 30°C/km or 1°C/33 m 2

Unconformity:

Unconformity Buried surface of erosion

Characteristics of a Sedimentary Environment:

Fig. 7.4 Characteristics of a Sedimentary Environment

Common Sedimentary Environments:

Fig. 7.5 Common Sedimentary Environments

Cross-bedded Sandstone:

Peter Kresan Fig. 7.6 Cross-bedded Sandstone

Formation of Cross-beds:

Formation of Cross-beds Fig. 7.7

Modern Rippled Sand:

Raymond Seiver Fig. 7.8 Modern Rippled Sand

Ancient Ripple-marked Sandstone:

Reg Morrison/Auscape Fig. 7.8 Ancient Ripple-marked Sandstone

Slide 35:

MODERN ANCIENT Mudcracks

Slide 36:

Fig. 7.9

Bioturbation Tracks and Tunnels:

Chip Clark Bioturbation Tracks and Tunnels

Typical Alluvial Cycle Deposited by a Migrating River:

Typical Alluvial Cycle Deposited by a Migrating River Fig. 7.11

Partial Alluvial Cycles in China:

Fletcher & Baylis/Photo Reseaerchers Fig. 7.11 Partial Alluvial Cycles in China

Products of lithification:

Products of lithification

Slide 41:

Fig. 7.12 Compaction (Primarily of Muds) Precipitation of new minerals or additions to existing ones

Slide 42:

Fig. 7.12 Dissolution of More Soluble Minerals Recrystallization of Unstable Minerals

Slide 43:

Fig. 7.13 Quartz grain Calcite cement Peter Kresan

Relative Abundance of Sedimentary Rock Types :

Fig. 7.14 Relative Abundance of Sedimentary Rock Types

Conglomerate:

Fig. 7.15a Conglomerate Breck Kent

Sandstone:

Fig. 7.15b Fig. 7.15a Sandstone Breck Kent

Shale:

Fig. 7.15c Shale D. Cavagnaro/Visuals Unlimited

Four Major Groups of Sandstones:

Four Major Groups of Sandstones Fig. 7.16

Quartz Arenite: Pure Quartz:

Fig. 7.16a Quartz Arenite: Pure Quartz

Slide 51:

Fig. 7.16b Arkose: Feldspar-rich

Lithic Sandstone: Rock Fragment-rich:

Fig. 7.16c Lithic Sandstone: Rock Fragment-rich

Graywacke: Matrix-rich:

Fig. 7.16d Graywacke: Matrix-rich

Foraminifer in the Eye of a Needle:

Foraminifer in the Eye of a Needle Fig. 7.17 Chevron Corporation

Coral Reef Surrounding Volcanic Island:

Coral Reef Surrounding Volcanic Island Fig. 7.18 Jean-Marc Truchet/Tony Stone Worldwide

Limestone:

Breck Kent Fig. 7.19a Limestone

Gypsum:

Breck Kent Fig. 7.19b Gypsum

Halite:

Breck Kent Fig. 7.19c Halite

Chert:

Breck Kent Fig. 7.19d Chert

Fossiliferous Limestone:

Fossiliferous Limestone Peter Kresan

One Model for the Formation of Evaporites:

One Model for the Formation of Evaporites

Rifting can create a sedimentary basin:

Rifting can create a sedimentary basin