Term

Definition

Aggradations

Surface build-up caused by deposition of sediment

Alga/Algae

Uni- or multi-cellular organisms (formerly classified as plants), which contain chlorophyll but lack true stems, roots, and leaves.  They can occur in either fresh or salt water.  They are now regarded as protoctists which include protozoans and slime moulds.

Alluvia/Alluvium/Alluvial deposits

accumulation of clay, silt, sand, gravel, and boulders deposited by fast-flowing mountain rivers when they reach flatter land, especially while they are in flood.

Alluvial plain

Extensive low lying area of alluvium

Aeolian erosion

Sediments which are deposited having been transported by wind

Anthrosol

Soil, the main characteristics of which are the result of human activity

Aquifer

A water-bearing stratum of permeable rock, sand, or gravel

Archaeosediment

Deposits which form a part of a sedimentary record deriving directly from human activity and are in primary context

Arid

Arid environments are characterized by very low rainfall and desert or semi-desert terrain

Articlast

Articlast is a term coined by Gladfelter to describe artefacts which have been found in sediments that are not in their original context (see Clastics)

Braided river

A river which has split into a series of interconnected channels that flow around small islands of sediment.

Chert

Chert is a fine-grained microcrystalline form of silica usually occurring as bands or layers of pebbles in sedimentary rock, (a variety of which is flint).  It is formed in ancient ocean sediments and often has a semi-glassy finish.  It can be one of several colours. From an archaeological point of view it has excellent fracturing properties producing good cutting edges.  Chert should not be confused with flint, although the difference between the two and how they should be defined is a source of some disagreement.

Clastics

Rock material transported mechanically (e.g. by river) fragmented and deposited in sedimentary context.

Deflation

Removal by strong winds of loose dry material from the surface, revealing earlier sedimentary layers.  Extensive deflation can form “deflation hollows” like Egypt’s Qattara Depression.

Delta

An area of low ground found at the mouth of a river discharging into the sea/a lake. As the river meets the sea it slows down and the sediment that it is carrying is deposited, filling in the mouth of the river and causing a braiding affect as the river splits into multiple channels. The Nile delta is characteristic of the triangular shaped delta.

Diatom

microscopic unicellular alga of the phylum Bacillariophyta

Diatomite

A soft very fine-grained whitish rock consisting of the siliceous remains of diatoms deposited in small ponds or lakes

Ecotone

A transitional area between two distinct, but adjoining, environments

Eluvial

Deposited by action of wind

Ferruginous limestone

Limestone (a sedimentary rock consisting mainly of calcium carbonate, deposited as the calcareous remains of marine animals or chemically precipitated from the sea) containing iron.

Flint

A hard, sedimentary crypto-crystalline silicate rock which beneath the cortex has a slightly glassy appearance, and is smooth to the touch. Flint is usually dark-grey, black, or deep brown in colour. It occurs chiefly as nodules in chalks and limestones. Its silicate structure and low granularity make it attractive for knapping tools, as fractures run without interruption, making them relatively easy to work. Related to chert.

Fluvial processes

The actions caused by a river

Fluvatile erosion

Erosion occurring as a result of the actions occurring in a river

Fossil Springs

The remains of a natural outflow of ground water, as forming the source of a stream (no longer active)

Geoarchaeology

Use of geological knowledge and techniques to solve archaeological problems and answer archaeological queries

Geofact

Natural object that appears to be an artefact

Geomorphology

The description and interpretation of landforms

Holocene

the second and most recent epoch of the Quaternary period, which began 10,000 years ago at the end of the Pleistocene

Hydromorphic soils

A general term for soils that develop under conditions of poor drainage in marshes, swamps, seepage areas, or flats

Hyperaridity

Areas where rainfall is extremely low and unpredictable -  some years there is no rainfall at all. Nearly 70 per cent of today’s hyperarid area is made up of the Sahara Desert in Africa

Inselberg

An eroded rocky hill rising abruptly from a flat plain, isolated when whind action erodes the surrounding landscape

Intercalated

Something inserted between existing layers

Inundation

Flood - a term often used for the annual Nile flood and the Ancient Egyptian season when flooding occured

Lacustrine

of or relating to lakes. Lacustrine deposits are Materials deposited in lake water and later exposed either by lowering of the water level or by uplifting of the land. These sediments range in texture from sands to clays

Lag

Coarse sediment left on the surface by wind action

Marl

Detrital muds that contain a significant amount of calcium carbonate, often originating as deposits in lakes and ponds

Nilotic

of or relating to the Nile

Quaternary

the most recent period of geological time, which succeeded the Tertiary period one million years ago divided into Pleistocene and Holocene (Recent) epochs or series

Oasis

a fertile patch in a desert occurring where the water table approaches or reaches the ground surface

Outcrop

The exposed surface of rock layers which have not been eroded or disintegrated

Palaeosol

 Buried soils or uncovered soils

Pediment

Gently sloping rock surface forming a ramp up to the front of upland ranges in arid regions produced by erosion

Pedimentation

The process that of erosion under arid conditions that causes the creation of a gently sloping rock surface called a Pediment

Pedestal rocks (mushroom rocks)

Rock formations like those in the White Desert, eroded at the base by abrasive action of sand carried by the wind

Playa

The floor of an inland basin in an arid region formerly home to a seasonal lake, and characterized by layers of lacustrine sediments.

Pleistocene

the first epoch of the Quaternary period, which lasted for about 990 000 years - characterized by extensive glaciations of the N hemisphere and the evolutionary development of man

Pluvial

Something that is the result of action by rain

Sahel (Sahelian)

The Sahel is a semiarid region of north-central Africa south of the Sahara Desert, which has suffered numerous droughts in modern times.  It is sometimes referred to as a transitional zone, as it sits between the arid Sahara to the north and the woodland savanna and tropical rainforests to the south at latitude 15-20°N and 15°W-15°E). The main countries which have Sahelian conditions are Senegal, Mauritania, Burkina Faso, Niger, Nigeria, and Chad.  For more information see:
http://www.eden-foundation.org/project/desertif.html

Savanna

A tropical or subtropical grassland containing scattered trees and drought-resistant undergrowth including small trees, shrubs and drought resistant grasses.Savanna regions experience dry periods and receiving more rainfall than desert areas but not enough to support complete ground cover or substantial tree growth.

Scarp

A steep slope or cliff, sometimes formed by erosion or faulting

Seif-dune

A dune which forms roughly parallel to the direction of the prevailing wind. These may be immense – as much as 100m tall and 50km long.

Semi-arid

characterized by scanty rainfall and scrubby vegetation, often occurring in continental interiors

Steppe

Temperate, semiarid areas of treeless short grass and shrubs, ideal for large herds.. 

Vertisol

A type of soil in which there is a high content of expanding and shrinking clay that forms deep cracks in certain seasons, and characterized by high levels of vertical mixing. They generally form under grasslands during dry seasons

Wadi

A valley, gully, riverbed or watercourse in North Africa or Arabia which is dry except in the rainy season. In the rainy season these channel an immense amount of loose desert matter.   Also known elsewhere as an arroyo.

Whaleback Dunes

Very large longitudinal dunes with flat tops on which other types of dune may be created. It is not known for sure how they are formed.