Chapter 6

what is the difference between breccia and conglomerate?in what environment do you find each type?

Breccia- Angular Particles Conglomerate- Rounded Particles They exist in a water flowing moist environment that rounds them.

explain how carbonates can be formed organically (biochemically) and non organically. List some of examples of each.

Carbonates are formed from CaCO3 (limestone) Organically- Percipitated through actions of organisms. Inorganic- precipitated directly as the result.

explain how chert is often formed

Chert is formed when a fine-grained sedimentary rock is formed almost entirely of silica and formed from inorganic precipitation where underground water replaced part of the original rock

list from smallest to largest: boulder, clay, silt, cobble, pebble and sand. what is the difference among a sandstone, siltstone and shale

Clay, Silt, Sand, Pebble, Cobble Sandstone- Formed by the cementation of sand grains Shale- A fine-grained sedimentary rock notable for its ability to split into layers. Siltstone- Consisting of consolidated silt.

where do you commonly find sandstone? what is the difference between a quartz, sandstone, and arkose?

On the seafloor Quartz sandstone is 90% quartz grains. Arkose is 25% feldspar in its grains.

how are oolitic limestone, tufa and travertine formed? Explain in detail as we talked about in lecture. a) which is formed in tropical environment and looks like bird seeds b) which one might you find at mono lake in California c) which type has layered bands of different colors d)which ones are formed in fresh water environment?

Oolitic- Formed by the cementation of small spheres of calcite inorganically. Tufa- a percipitated solution in the water of continental spring/lake percolating water.

inorganic:

precipitate directly as the results of an inorganic process - oolitic limestone: cementation of calcite and sand grains -travertine: fresh water sources ( caverns) -tufa: fresh water lake source

cementation

results in the decrease of prosperity

ripples

small dunes of sand or silt that are at right angles to current. shallow streams , waves a beaches windswept dunes

what do geologist mean when they talk about source areas and rock types?

source are: locality that eroded and provided sediment rock type: composition of a sediments that can indicate the source area rock type

how does current strength and weathering affect particles?what is the difference between well sorted and poorly sorted deposits? why are some rocks rounded?

1) It affects the deposition and the lithification 2) Well-sorted deposits are preserved better and cemented better than poorly sorted deposits// poorly sorted all sediment sized in the same place 3) Some rocks are rounded because they are in a water source of some form and smaller sands and rocks grind it down.

what are the 3 types of sedimentary rocks? what are each of their characteristics?

1) detrital/clastic sediments: formed from weathered and eroded remains of bedrock or animals ex: granite 2)chemical sediments: precipitated from an aqueous environment (I.e. evaporates) 3)organic sediments: remains of organisms and plant match; halite "rock salt" (I.e. coal)

what is bedding? what is a bedding plane?

Bedding- A series of visible layers within rock. (visible horizontal layers) Bedding Plane- A nearly flat surface of deposition separating two layers of rock. (flat surface separating 2 layers of rock. change in grain size composition or pause during deposition can create bedding planes)

what are the differences among a shale, siltstone, clay stone and mudstone. what does a fissile mean?

Differences: Shale- fine-grained sedimentary rock that is very fissile. Siltstone- A rock that consists mostly of silt grains Claystone- rock composed of clay-sized particles but lacks fissility of shale. Mudstone- contains both silt and clay, the grain size and smooth feel of shale but not the as sleek and shiny. Fissile- A sedimentary rocks ability to split into layers.

what is a formation and contact?

Formation- A body of rock considerable thickness that is large enough to be mappable, and with characteristics . Contact- The boundary surface between two different rock types or ages of rocks.

Explain evaporites are formed. List at least 3 examples.

Evaporites are formed from the evaporation of seawater or a saline lake. Ex: Gypsum, Salt

list at least 3 different ways fossils are formed

Petrified Molds Trace

how can you determine the direction of current by studying cross-beds and rock types?

The way the bedding settles and the direction the sand usually settles and on what side tells the direction of current.

how does cross bedding, graded bedding ripples and mud cracks form? a)which of the above features may form when a body of water evaporates? b) which of the features may for in a river bed once a stream current decreases? c) which features can form in both wind and water movement

They form when sediments are deposited and are originally deposited as horizontal layers.

formation

a body of rock considerable thickness that is usually defined by rock type other recognizable characteristics

Lithification

a process that converts loose sediments into sedimentary rock due to 1) compaction ,2) cementation or crystallization

Consider a stream flowing from a mountains area downhill to a flat flood plain and then onto the coastline and eventually into ocean. a)In what area are you most likely to find large, angular rocks? b) In what area are you most likely to find breccia rocks formed? c) In what area are you most likely to find sand-sized particles? d) In what area are you most likely to find only clay and silt-sized particles?

a) The mountains b) Mountain Area and Coastline c) Coastline and Ocean d) Ocean

biochemical/bioclatic

accumulation of shells, algae and corals in a warm, shallow, reef enviorment - coquina: from shell fragments chalk: from tiny organisms

contact

boundary between 2 different rock types or ages of rocks ( or formation)

What are the effects of heat, pressure, and cementation when sediments undergo lithification? a) Name two types of "natural cements" b) Which type is commonly used in concrete to make sidewalks and buildings? c) What type of cement do you think would more easily erode in an acidic environment?

compaction a) breccia & conglomerate b) sandstone c) greywacke

limestone

composed of calcite; can be biochemical/ bioplastic or inorganic

graded bedding

deposited by a gradually slowing current coarse at bottom, Fine at top

cross bedding

deposited by wind or water and inclined at 35 deg. -show direction of wind or water current

mudcracks

dried fine-grained sediments

chert

fine grained, mainly silica (biochemical: tiny rich fossils or inorganic: lumpy nodules in other rocks)

evaporites

from evaporation of seawater or a saline lakes. crystalline texture

what types of deposits are observed in glacial, alluvial fan, river channel, lake, beach, shallow marine, reef, and deep marine sediments? ( review figure 6.35)

glacial: till poorly sorted; unweathered boulders, cobbles, sands, silts, and clays alluvial fan: river derived sediments; fan-shaped: often coarse, arkosic sandstone and conglomerate, cross bedding River channel: conglomerate to fine sands; cross beds, ripple marks lakes: thin bedded shales and evaporites beach: well sorted, rounded sandstone shallow marineL sands to shale offshore, ripple marks, low angle cross beds, marine fossils reefs: limestone deposits with beds of sands and fines (muds) deep marine sediments: shales

crystallization

interlocking crytal texture due to crystal growth

compaction

minerals percipitate in pores of sediments

sediments

name for loose (unconsolidated), solid particles that collect in layers on earth's surface.

deposition

occurs when transported sediments settle - enviorments of deposition included deep-sea floor, desert valley, a river channel, a coral reef, and a beach and a sand dune

fossils

plants, animals footprints burrows etc.