The Aymestry Limestone is an inconstant limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

  deposited in a warm shallow sea near the eastern margin of the Iapetus Ocean

Iapetus Ocean

The Iapetus Ocean was an ocean that existed in the Neoproterozoic and Paleozoic eras of the geologic timescale . The Iapetus Ocean was situated in the southern hemisphere, between the paleocontinents of Laurentia, Baltica and Avalonia...

. It occurs in England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

 in the Ludlow series of Silurian

Silurian

The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...

 rocks, between the Upper and Lower Ludlow Shales. It derives its name from Aymestry, Herefordshire

Herefordshire

Herefordshire is a historic and ceremonial county in the West Midlands region of England. For Eurostat purposes it is a NUTS 3 region and is one of three counties that comprise the "Herefordshire, Worcestershire and Gloucestershire" NUTS 2 region. It also forms a unitary district known as the...

, where it may be seen on both sides of the river Lugg

Lugg

- Geographical names :* River Lugg in Wales and England* Moreton-on-Lugg, a village in Herefordshire, England- People :* Milton DeLugg , an American composer and arranger* William Lugg , a British actor and singer- Fiction :...

. It is well developed in the neighborhood of Ludlow

Ludlow

Ludlow is a market town in Shropshire, England close to the Welsh border and in the Welsh Marches. It lies within a bend of the River Teme, on its eastern bank, forming an area of and centred on a small hill. Atop this hill is the site of Ludlow Castle and the market place...

 (it is sometimes called the Ludlow limestone) and occupies a similar position in the Ludlow shales at Woolhope

Woolhope

- Location :Woolhope is located about 7 miles east of Hereford.- History :The manor of Woolhope in Herefordshire, along with three others, was given to the cathedral at Hereford before the Norman Conquest by the benefactresses Wulviva and Godiva, local Anglo-Saxon landowners before the Norman...

, the Abberley Hills, May Hill

May Hill

May Hill is a hill between Gloucester and Ross-on-Wye, whose summit is on the western edge of Gloucestershire, though its northern slopes are in Herefordshire....

 and the Malvern Hills.

In lithological character, this limestone varies greatly; in one place it is a dark grey, somewhat crystalline limestone, elsewhere it passes into a flaggy, earthy or shaly condition, or even into a mere layer of nodules. When well developed it may reach 50 ft. in thickness in beds of from I to 5 ft.; in this condition it naturally forms a conspicuous feature in the landscape because it stands out by its superior hardness from the soft shale

Shale

Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...

s above and below.

The most common fossil

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 is Pentamerus knightii

Pentamerus

Pentamerus is a prehistoric genus of brachiopod that lived from the Silurian to the Middle Devonian in Asia, Europe, and North America.-External links:* in the Paleobiology Database...

, which is extremely abundant in places. Other brachiopod

Brachiopod

Brachiopods are a phylum of marine animals that have hard "valves" on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection...

s, coral

Coral

Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...

s and trilobite

Trilobite

Trilobites are a well-known fossil group of extinct marine arthropods that form the class Trilobita. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period , and they flourished throughout the lower Paleozoic era before...

s are present, and are similar to those found in the Wenlock limestone.