Sed Strat MIDTERM v.2

Particles derived from preexisting rocks

lithic fragments

Minerals that grow as crystals in a depositional environment

authigenic

The numerical representation of the Wentworth scale

phi

A conglomerate that contains clasts of many different lithologies

polymict

A conglomerate with two or three clastc types of gravel present

oligomict

A conglomerate composed of clasts and matrix made of the same material from reworking on formation

intraformational conglomerate

Clasts are all touching each other throughout the rock, so it is…?

clast supported

What is a conglomerate made of angular pieces

breccia

Small pieces of calcium carbonate made of broken shells of organisms

biogenic fragments

Phyllosilicate minerals that are composed of very small crystals

clay minerals

The process of turning loose sediments into “rock”

lithification

The classification system of sandstones

Pettijohn classification

Finer grained material between clasts

matrix

Distribution of clast sizing within a rock

sorting

The extent to which material has changed compared to starting material

maturity

In Dunham’s classification, a rock formed from the encrustation of organisms binding particles together

Bindstone

Iron Carbonate FeCO₃

Siderite

A less stable form of calcium carbonate that commonly recrystallizes

Aragonite

In the subsurface gypsum is usually this different mineral because it loses the water in the crystalline structure under pressure

Anhydrite

Calcium magnesium carbonate

Dolomite

A spherical body of calcium carbonate with concentric layers less than 2mm in diameter

Ooid

Concentrically layered carbonate particles over 2mm in diameter

Pisoid

A shallow marine plant that has a skeleton that contributes A LOT of carbonate to limestones

calcareous green algae

The sequence of evaporate minerals that precipitate out of seawater

CaCO₃→CaSO₄→NaCl→KCl

Small, round particles made of fine-grained calcium carbonate that were commonly fecal pellets of marine organisms

Peloid

Fragments of calcium carbonate material that has been eroded and reworked and deposited as a particle of limestone within a limestone

Intraclast

Irregular concentric structures formed by cyanobacteria like a round stromatolite that rolled around during growth

Oncoid

In Dunham’s classification, a rock containing some sand-sized particles >10% that are separated from one another and floating in carbonate mud

Wackestone

In Dunham’s classification, a rock containing very few sand-sized particles <10% and is mostly carbonate mud

Mudstone

In Dunham’s classification, a rock made of reef forming organisms that form a framework

Framestone

In Dunham’s classification, a rock containing sand sized fragments that has no carbonate mud, only cement between the grains

Grainstone

In Dunham’s classification, a rock containing sand sized particles that are grain supported that the spaces between the grains are filled with carbonate mud

Packstone

Some of the organisms that might contribute the silica for chert

Radiolarian and diatoms

The sediment composed mainly of the skeletons of very tiny siliceous sediments at the bottom of the deep ocean

Siliceous ooze

A type of boundstone that forms because flimsy, tall organisms stall the current causing particles to settle and make a mound around them

Bafflestone

When the rate of addition of sand is high and the ripple accumulates on the stoss side

Climbing ripples

The steeper, narrower side of the ripple mark

Lee side

Curved cross laminae that occur because the trough-shaped low areas between adjacent ripples

trough cross laminae

Flow in which molecules move in all directions, but with a net movement downstream because of high velocity or low viscosity

Turbulent

Flow in which molecules move parallel to each other in the direction of transport because of low velocity or high viscosity

laminar flow

Change in grain size within a bed going from coarse at the base to fine at the top, indicating waning energy

normal grading

The name of the diagram that is a graph of grain size and velocity that shows a line that particles are deposited and a line that shows when particles are eroded

Hjulstrom

The speed at which a current will be moving when a grain of a certain size is lifted or eroded from a substrate

critical velocity

The equation or concept that describes how lift happens

Bernoulli

The bouncing action of particles or “jumping” as part of the bedload

saltation

The portion of the sediment load that is kept up in the water column

suspended load

The pile of angular rocks at the base of a mountain

talus cone

Alternating layers of ripples with layers of mud that indicate that there is just enough sand to form ripples, then a period of quiet energy

starved ripples

the small scour between ripples, or the lowest spot between two crests

trough

Curved or arcuate ripples that are “tongue” shaped

linguoid ripples

What are the two general types of sedimentary rocks?

clastic & non-clastic

What are the types of clastic rocks?

volcaniclastic

clastic

carbonates

What are the types of non-clastic rocks?

carbonates

evaporites

others (coal, siliceous…)

What is the classification system for terrigenous clastic sedimentary rocks?

Udden-Wentworth Scale

What is the size for clay particles?

<4μm

What is the size for silt particles?

4-63μm

What is the size ranges for sand particles?

63μm (0.063 - 2.0 mm)

What is the size for gravel/aggregates?

(>2.0 mm)

What does the phi scale describe?

logarithm base 2 of the grain sizes to better represent inventory of grain sizes graphically

What is sedimentology?

the study of processes of formation, transport, and deposition of material that accumulates as sediment in continental and marine environments

What is stratigraphy?

the relationship between rocks and time

What is missing?

Gravel, Conglomerate

What is missing?

Sandy gravel, Sandy conglomerate

What is missing?

Gravelly sand, Gravelly sandstone

What is missing?

Sand, Sandstone

What is missing?

Muddy sand, Muddy sandstone

What is missing?

Sandy mud, Sandy mudrock

What is missing?

Mud, Mudrock

What is missing?

Muddy gravel, Muddy conglomerate

What is missing?

Muddy sandy gravel, Muddy sandy conglomerate

What is missing?

Gravelly mud, Gravelly mudrock

What is missing?

Gravelly muddy sand, Gravelly muddy sandstone

What is orthoconglomerate?

indicates a rock is clast-supported

What is paraconglomerate?

Indicates that a rock is matrix-supported

Define sand

sediment consisting primarily of grains in the size range 63μm - 2mm

What minerals can potentially make up detrital sand grains?

quartz, feldspar, mica, olivine, pyroxene, amphibole…

What is the Pettijohn classification system?

A system through which sandstones are categorized based on texture, proportion of muddy matrix, and the percentages of the three commonest components of sandstone: quartz, feldspar, and lithic fragments. Utilizes multiple ternary (QFL) diagrams going from a matrix of mostly sand grains to mudrock.

What are clay minerals?

phyllosilicates with a layered crystal structure similar to that of micas and compositionally they are aluminosilicates

What are the four main clay minerals?

1. kaolinite

2. montmorillonite

3. illite

4. chlorite

What are some properties of kaolinite?

ONLY TWO-LAYER CLAY formed in warm, humid environments and it the commonest member of the kandite group

What are some properties of montmorillonite?

an expandable or swelling clay, forms under alkaline conditions in arid climates

What are some properties of illite?

three-layer clay minerals related to the mica group; forms in soils in temperate areas

What are some properties of chlorite?

three layer clay forms most commonly in soils under fairly acidic groundwater conditions

What is fabric?

used to describe the tendency to break in a certain direction or sows a strong alignment of elongate clasts

What are the minerals that make up limestones?

1. Calcite

2. Aragonite

3. Dolomite

Describe Calcite

CaCO₃, very soft, most commonly has a biogenic origin and comes in two types:

1. hi mag calcite

2. lo mag calcite

Describe Aragonite

orthorhombic crystal form

more densely packed lattice than calcite

Describe Dolomite

(CaMg(CaCO₃)₂)

largely diagenetic, no fizz

What are some carbonate forming animals that produce skeletal fragments that are included in some limestones?

bivalve molluscs, gastropods, echinoids, arthropods, bryozoa

What fossil groups are made of aragonite?

ammonites, belemnites, bivalves, gastropods

What fossil groups are made of hi mg calcite?

echinoderms, bryozoans, foraminifera, red algae

What fossil groups are made of lo mg calcite?

brachiopods, trilobites, rugose corals

What is an ooid?

spherical bodies of calcium carbonate <2mm in diameter with concentric layers

What is a pisoid?

concentrically layered carbonate particles >2mm

What is a peloid?

fecal pellets of marine organisms that are very abundant in some carbonate deposits

What is an oncoid?

irregularly shaped concentrically layered calcium carbonate deposit >2mm

What is the Dunham Classification System?

A system where limestones are classified by whether their allochthonous components were are were not not bound together during deposition - based on grain size, is it is grain-supported or not, and the percentage of skeletal inclusions

Dunham: What is a carbonate mudstone?

<10% clasts, mud-supported