The clasts and matrix are typically cemented by calcium carbonate, iron oxide, silica, or hardened clay.

They are closely related to sandstones in origin, and exhibit many of the same types of sedimentary structures, such as tabular and trough cross-bedding and graded bedding.

[1][2][3] Fanglomerates are poorly sorted, matrix-rich conglomerates that originated as debris flows on alluvial fans and likely contain the largest accumulations of gravel in the geologic record.

[2][5] Conglomerates contain at least 30% of rounded to subangular clasts larger than 2 mm (0.079 in) in diameter, e.g., granules, pebbles, cobbles, and boulders.

Typically, the space between the gravel-size clasts is filled by a mixture composed of varying amounts of silt, sand, and clay, known as matrix.

In the sediments deposited by mature rivers, conglomerates are generally confined to the basal part of a channel fill where they are known as pebble lags.

At mountain fronts individual alluvial fans merge to form braidplains and these two environments are associated with the thickest deposits of conglomerates.

When such conglomerates accumulate within an alluvial fan, in rapidly eroding (e.g., desert) environments, the resulting rock unit is often called a fanglomerate.

The Crestone Conglomerate consists of poorly sorted fanglomerates that accumulated in prehistoric alluvial fans and related fluvial systems.

Conglomerate cliffs are found on the east coast of Scotland from Arbroath northwards along the coastlines of the former counties of Angus and Kincardineshire.

Dunnottar Castle sits on a rugged promontory of conglomerate jutting into the North Sea just south of the town of Stonehaven.

Copper Harbor Conglomerate is found both in the Keweenaw Peninsula and Isle Royale National Park in Lake Superior.

[13] In the nineteenth century a thick layer of Pottsville conglomerate was recognized to underlie anthracite coal measures in Pennsylvania.

[14] On Mars, slabs of conglomerate have been found at an outcrop named "Hottah", and have been interpreted by scientists as having formed in an ancient streambed.