Geology Flashcards

Flashcards for Paleontology, Stratigraphy, and Paleoenvironment lecture review.

Fossil

The naturally preserved remains or traces of animals or plants that lived in the geologic past.

Body fossils

Actual physical remains of ancient organisms preserved in the rock record.

Trace fossils

Represent the activities of ancient organisms as preserved in the rock record.

Chemical fossils

Chemical compounds secreted by organisms, preservable in the rock record, unique to a particular group and used as evidence of their existence.

Rapid burial/entombment

Isolates remains from scavengers and long-term physical disturbance.

Low oxygen

Allows remains to be isolated from scavengers and slows down bacterial decay.

Calcium carbonate (CaCO3)

Principal mineral components of most seashells, can be unstable over geological time.

Aragonite

Unstable calcium carbonate mineral, often dissolves or transforms to calcite.

Calcite

Stable calcium carbonate mineral; calcitic shells tend to be well-preserved.

Silica (SiO2)

Usually amorphous hydrated silica transforms to quartz and other silica minerals following death.

Calcium phosphate (apatite)

Stable component of bones, teeth, and some shells; tends to be well-preserved.

Carbonization

Removal of volatile constituents from the organic compound leaving only Carbon as a thin black film.

Permineralization/Petrification

Addition of secondary mineral matter to most vertebrate bones and invertebrate shells, makes them denser and more durable than the original unaltered hard parts.

Replacement

Original skeleton is removed and replaced by other mineral substances such as silica, pyrite, iron or carbonates.

Recrystallization

Alteration of less stable inorganic compounds into more stable ones without any chemical change.

Imprints

Impression formed when an organism is pressed into soft sediment and later removed.

Mould

Impression of skeletal remains on rocks, representing the external or internal surface of the organism.

Cast

Filling of shell cavities by minerals or other sediments.

Ichnology

Study of tracks, trails, and burrows of organisms.

Tracks

Traces of feet made by quadrepedal or bipedal vertebrates during movement on soft sediments.

Trails

Traces made by animals during crawling on sediments.

Burrows

Pathways made by animals in soft sediments.

Excrements (Coprolites)

Solid excretory waste products of animals preserved in the geologic record.

Uniformitarianism

The present is the key to the past.

Index fossils

Fossilized animals and plants are used to determine the relative geologic age of sediments, the nature of paleoenvironments, and the palaeogeography that characterized a particular area.

Foraminifera

Unicellular organisms belonging to the Protozoa with a mineralized skeleton or test formed from chambers interconnected by openings.

Benthonic

Bottom-dwelling organisms that live either on or below the ocean floor.

Sessile benthos

Benthos that attach themselves to the substrate.

Vagrant benthos

Benthos that either creep or swim over the bottom or burrow into the bottom.

Planktonic

Floating organisms that live suspended in the upper water column with only a very weak or limited control of their mobility.

A- Form (Megalospheric form)

Has a large first formed chamber (Proloculus), and a small test size; reproduces sexually to give B- Form.

B- Form (Microspheric form)

Has a small first formed chamber (Proloculus), and a large test size; reproduces asexually to give A- Form.

Porifera (Sponges)

Sac-like organisms that represent the simplest group of multicellular animals.

Sessile benthonic animals

Animals that live fixed to the substrate and extract organic particles from water entering through sponge pores.

Coelenterata (Cnidaria)

Exclusively aquatic organisms, which live either sessile (polyp) or free swimming (medusa).

Bryozoa

Bryozoa (moss-like invertebrates), are colonial animals living mostly in marine water, a few types inhabit fresh water.

Zooid

The bryozoan animal.

Zooecium

The skeleton of one individual.

Zoarium

The skeleton of colony.

Brachiopoda

Sessile marine animals that secrete an external shell consisting of two dissimilar but equilateral valves.

Pedicle

The fleshy stalk by which the brachiopod is attached to the sea floor.

Mollusca

Soft-bodied invertebrate creatures, most of them secreting a hard external shell.

Bivalvia (Pelecypoda)

Bivalves are characterized by the presence of two valves enclosing the body.

Gastropoda

Gastropods are mollusca having a shell consisting of a single piece, usually sealed apically and coiled helically, and lacking serial muscle scars.

Whorl

Complete coil of a shell

Suture

Line along which successive whorls meet.

Dextral coiling, right lateral coiling

Genera are coiled in a clockwise direction so that the aperture is on the right

Sinistral coiling, left lateral coiling

Shells are coiled in an anti-clockwise direction, and in this case the aperture lies on the left

Cephalopoda

Cephalopods are characterized by a single shell, which may be straight, curved, or coiled planispirally, but a few species are trochospirally coiled.

Septa

Transverse partitions that divide the shell into chambers

Siphuncle

Tube that extends from the mantle to the apex of the shell

Suture

Impression of septa on the exterior of the shell

Phragmocone

The chambered part of the shell

Belemnites

An extinct group called Belemnites whose shell was enclosed by the soft body

Echinodermata

They are exclusively marine animals which live free like family and the test consists of many interlocking plates, arranged in 10 double columns

Ambulacrae

Columns that carry tube feet

Interambulacra

Columns with no tube feet

Apical system

Consists of 10 small plates, five ocular plates and five genital plates at the apex of the test

Madreporite

One of the genital plates is modifies into a large number of pores for the passage of water to the water vascular system

Trilobita

A group of extinct fossils belonging to the arthropods and their body is segmented