SEDS: Conglomerate Flashcards
Consolidated grains of gravel-sized particles
Conglomerate
Conglomerate with particles that were 64-256mm in diameter
Cobble Conglomerate
Conglomerate wherein the clasts are angular
Breccia
conglomerate where the clasts are both rounded and angular
Breccio-conglomerate
Debris deposited directly by melting ice in a glacier
Till (tillite)
a non-glacial till-like deposit (olistostrome or grainflows)
Tilloid
composed of clasts of the same material as the matrix and is formed as a result of reworking of lithified sediment soon after
deposition
intraformational conglomerate
A conglomerate in which clasts are exotic (i.e., derived from outside the depositional basin). Clasts are normally very well-rounded and well-sorted—clasts derived from a distant source.
Extraformational Conglomerate
clast-supported conglomerate or
“true conglomerate
Orthoconglomerate
A conglomerate in which all clasts are in contact with other clasts (i.e., the clasts support each other). Such conglomerates may have no matrix between clasts (open framework) or spaces between clasts may be filled by a matrix of finer sediment (closed
framework).
Orthoconglomerate
Orthoconglomerate’s matrix is ___________
less than 15%.
suggests an efficient sorting mechanism that caused the selective removal of finer-grained sediment
Open framework
suggests that the transporting agent was less able to selectively remove the finer fractions or was varying in competence, depositing the framework-filling sediment well after the gravel-size sediment had been deposited.
Closed framework
more than 90% of the framework clasts
consist of fragments of only a few varieties of resistant rocks and minerals as
metaquartzite, vein quartz, and cherts.
oligomict (orthoquartzose)
clasts of many different compositions of metastable and unstable rocks are abundant; for example, basalt, slate, and limestone
petromict (polymict)
imply wholesale decomposition and disintegration of immense volumes of rocks,
reflecting climate and topography that promotes chemical decomposition and physical disintegration of all but the most resistant components.
Oligomict orthoconglomerates
much more abundant than oligomict orthoconglomerates and are mainly alluvium eroded from high-relief areas
Petromict
A conglomerate in which most clasts are not in contact; i.e., the matrix supports the clasts
Paraconglomerate
matrix-supported conglomerate
Paraconglomerate
Matrix of sand or finer is at least 15% to 50%
Paraconglomerate
Typical of the deposits of debris flows or water flows in which gravel size clasts were not abundant in comparison to the finer grain sizes
Paraconglomerate
containing a matrix of delicately laminated mudrocks
Paraconglomerates
coarser framework grains float in Paraconglomerate.
laminated pebbly (or cobbly, or bouldery) mudrock.
the matrix is disorganized and non-laminated are either tillite (only if glacial origin can be inferred) or tilloid (deposited by mass movement)
Paraconglomerates
A rudite composed of poorly sorted, mud to gravel-sized sediment, commonly with angular clast
Diamictite
Commonly refers to sediment deposited from glaciers or sediment gravity flows, particularly debris flows.
Diamictite
less susceptible to physical and chemical breakdown, and have a higher chance of being preserved as a clast in a conglomerate.
Resistant lithologies
Factors controlling the resistance of a rock type
minerals present ;
ease with which they are chemically or physically broken down in the environment.
