absolute age

age measured in years and is usually determined by measuring isotopic decay

aggradation

growth either vertically or horizontally of morphological features. In coastal areas, these include the beach, dunes, sand banks, tidal flats, and salt marshes

alluvial fan

a landform shaped like a gentle mound or cone with its apex at the mouth of its sedimentary source, typically a mountain stream.

alluvium

unconsolidated detritus (clay, silt, sand, and gravel) deposited by streams and floods

ammonite

a cephalopod (similar to a nautilus) with a sutured shell; commonly it grows in a spiral form. They lived in the Jurassic and Cretaceous and are excellent for biostratigraphy and determining relative age

anhydrite

an anhydrous calcium sulfate mineral (CaSO4) that is formed in deeply buried evaporite deposits.  It absorbs water in near-surface environments to form gypsum.

anoxia

characterized by a lack of oxygen; thus, they do not support life such as burrowing or benthic organisms

arkose

a sedimentary rock consisting of sand or gravel with both feldspar and quartz; typically created by rapid weathering of granite

back arc basin

a basin formed near a volcanic arc on the side opposite the oceanic trench; this is the result of extension caused by mantle convection behind a subduction zone and its island arc

back reef

the area behind a reef that may include shallow marine sediments, shoreline, and evaporite sedimentary environments

backdune

a part of the system of dunes that is furthest from the ocean

Baltica

the northern craton of Europe underlying much of Scandinavia that was an independent continent that collided with northeastern North America in the early Paleozoic to form the Taconic, or Caledonian Mountains

barrier island

a coastal landform that is a barrier between the ocean and mainland generally running parallel to the main coastline. They typically occur in a chain and extend from several to 100's of kms

basin

a topographic or bathymetric low area. Structural basins have dipping strata toward the center. Depositional (sedimentary) basins have thick accumulations of sediment compared to adjacent regions

bed forms

the ocean bottom is seldom flat and often undulates from the interaction of currents and waves. These include ripples and sand ridges

benthic

related to the seafloor. Benthic organisms live on or in the substrate of the ocean floor

bentonite

a clay-rich rock made of smectite that formed from alteration of volcanic ash. It is mined as a major constituent of drilling mud.

caliche

a white to reddish brown material ranging from soil to rock produced in a soil in semiarid to arid environments. Caliche can have sand or gravel zones that are cemented by calcium carbonate.

coast

a strip of land from the coastline inland to an area that is not influenced by coastal processes

coastal area

both the land and the sea bordering a shoreline

continental shelf

the submerged portion of continent crust in relatively shallow water. It extends from the shoreline to the drop-off point marked by the shelf break.

correlation

process of relating either characteristics, time or stratigraphic position of separated rock units. This can be lithologic (similar rock types), biostratigraphic (similar fossil content), chronostratigraphic (similar ages), or chemostratigraphic (similar chemical signatures)

delta

a low, flat area near the mouth of a river typically with a triangular shape that is crossed by distributaries of the main river. It also includes the shoreline and off shore environments related to the delta plain. These form because the sediment load supplied by the river is too high to be washed away. They are classified by the main source of energy that supply the sediment load such as wave dominated, fluvial (river) dominated, or tide dominated.

depocenter

an area of maximum deposition in a stratigraphic unit

drainage basin

the area of land in which runoff feeds into a stream, lake, or reservoir. A first order drainage basin feeds directly into the ocean

fan delta

a type of alluvial fan that flows into lowlands that is reworked by shoreline and gravity processes

foredune

the part of a system of dunes closest to the ocean

graded beds

a sediment consisting of a mixture of coarse and fine detrital material

lagoon

a relatively shallow, narrow body of water that is parallel to the shoreline between a barrier bar or island and the mainland. It is connected to the ocean by narrow passes.  It may have high salinity and significant tides.

laterite

a soil rich in iron oxide and alumina, poor in silica, and depleted in alkali elements.  It forms by intense tropical weathering.

Laurentia

a continental block or craton consisting of most of North America and Greenland that has retained its integrity since late Proterozoic time. Since the collision of Baltica, the resulting continent is Laurasia.

logging

sometimes called well logging. Methods to identify characteristics of subsurface formations either by samples of physical responses (geophysical well logging) that are displayed as a function of depth of a borehole.

longshore current

the dominant current in the nearshore zone; typically runs parallel to the shore

lowstand

an interval of time when relative sea level is low and the continental shelf and carbonate platforms are exposed. Extensive deltas form at the margin and a lot of sediment can be transported into deep marine basins.

marl

sedimentary material that is a mixture of carbonate and clay; both present in subequal amounts

meandering

the tendency to scour the outer bend of a river channel and deposit sediment on the inner bend

member

a formal stratigraphic unit that is a part of a formation; these need not be mappable

minibasin

a small basin typically formed by subsidence in thick salt

mud

fine grained sediment with a high concentration of clay minerals

natural gas

a mixture of hydrocarbons generally with 1-5 carbon atoms with variable amounts of hydrogen atoms that is gaseous at the surface produced by degradation of organic matter in sedimentary rocks and microbial activity

nektonic

a organism that actively swims in the water column, compare with benthic and planktonic

novaculite

a sedimentary rock composed of finely crystalline quartz that may form from thermal alteration of bedded chert

offshore

this is not well defined, but is a zone beyond the nearshore. Typically it begins beyond where nearshore currents and waves affect the water column.

oolite

a type of limestone made of sand-size, well-rounded carbonate particles (oolith) with concentric layers formed in a shallow, wave agitated environment that are cemented together

Pangea

a supercontinent that existed from ~300 to 200 Ma and included almost all of Earth's continental crust

patch reef

a small carbonate reef that is moundlike and separated from other patch reefs or bioherms

pelagic

pertaining to the open ocean, often referring to organisms that do not need seafloor or continental environments

period

a unit of time such as the Cretaceous; a component of an era and composed of epochs

petroleum system

involves deposition, generation, migration, entrapment, and preservation of hydrocarbons in sedimentary basins

planktonic

an organism that drifts in the water column, compare with nektonic and benthic

plateau

a large flat area that covers a large region and is elevated above its surroundings. It is larger than a mesa.

playa

a dry, vegetation free flat area within a desert. It can be filled with ephemeral lakes (playa lakes) during wet seasons that evaporate during dry seasons

progradation

seaward movement of a shoreline and coastal area, occurs when the rate of sediment supply is more than the rate of relative subsidence

pumice

a vesicular felsic igneous extrusive rock with very low density such that it floats in water

radiocarbon dating

a method for determining absolute age by measuring the amount of carbon-14 remaining in organic material. Only used on rocks less than 70,000 years

reef

a mound or ridge built by calcite-secreting organisms such as coral, rudist mollusks, or sponges. They are resistant to waves and stand above the surrounding seafloor.

relative age

geologic age of an organism, rock, or event that is defined in relation to other rocks or events rather than in years before present or an absolute age

restricted shelf

a margin that has restricted flow of seawater, often associated with evaporites and arid conditions

retrogradation

landward retreat of a shoreline that occurs when the rate of sedimentation is slower than the rate of subsidence

Rodinia

a supercontinent formed in the Proterozoic eon (1000 to 700 million years ago)

rudist

a bivalve mollusk that existed from Late Jurassic to Cretaceous. The two valves (shells) were very unequal. This grew as solitary animals or in reefs.

scoria

a vesicular mafic igneous extrusive rock which often forms in cinder cones

sea level rise

a rise of the mean sea level; this causes coastline retreat and increased flooding

subsidence

downward motion of land; often related to soil compaction, extraction of natural gas or other mineral resources, and ground and water withdrawal. It can also occur with earthquakes, glacial isostatic adjustment, erosion, sinkhole formation, or sediment loading

U-Pb geochronology

a method of determining absolute age using isotopes of  uranium, thorium, and lead typically using the mineral zircon. Yields ages between 4,500 to 5 Ma

window

in structural geology, it is an eroded area that shows rocks beneath a thrust sheet

zircon

a zirconium silicate mineral, ZrSiO4, that is present in felsic and intermediate igneous rocks as well as metamorphic and sedimentary rocks.  Thus, it is invaluable for U-Pb geochronology

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The Story of Earth: An Observational Guide 2e Copyright © 2023 by Daniel Hauptvogel & Virginia Sisson is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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