Mare Fecunditatis is a lunar mare

Lunar mare

The lunar maria are large, dark, basaltic plains on Earth's Moon, formed by ancient volcanic eruptions. They were dubbed maria, Latin for "seas", by early astronomers who mistook them for actual seas. They are less reflective than the "highlands" as a result of their iron-rich compositions, and...

 which is 840 km in diameter. The Fecuditatis basin formed in the Pre-Nectarian

Pre-Nectarian

The Pre-Nectarian Period of the lunar geologic timescale runs from 4533 million years ago to 3920 million years ago, when the Nectaris Basin was formed by a large impact. It is followed by the Nectarian period...

 epoch

Epoch (geology)

An epoch is a subdivision of the geologic timescale based on rock layering. In order, the higher subdivisions are periods, eras and eons. We are currently living in the Holocene epoch...

, while the basin material surrounding the mare is of the
Nectarian

Nectarian

The Nectarian Period of the lunar geologic timescale runs from 3920 million years ago to 3850 million years ago. It is the period during which the Nectaris Basin and other major basins were formed by large impact events...

 epoch. The mare material is of the Upper Imbrian

Upper Imbrian

In the Lunar geologic timescale, the Late Imbrian epoch occurred between 3800 million years ago to about 3200 million years ago. It was the epoch during which the mantle below the lunar basins partially melted and filled them with basalt...

 epoch and is relatively thin compared to Mare Crisium

Mare Crisium

Mare Crisium is a lunar mare located in the Moon's Crisium basin, just northeast of Mare Tranquillitatis. This basin is of the Pre-Imbrian period, 4.55 to 3.85 billion years ago. This mare is in diameter, and 176,000 km2 in area. It has a very flat floor, with a ring of wrinkled ridges...

 or Mare Tranquillitatis

Mare Tranquillitatis

Mare Tranquillitatis is a lunar mare that sits within the Tranquillitatis basin on the Moon. The mare material within the basin consists of basalt formed in the intermediate to young age group of the Upper Imbrian epoch. The surrounding mountains are thought to be of the Lower Imbrian epoch, but...

. This basin is overlapped with the Nectaris, Tranquillitatis, and Crisium basins. Fecunditatis basin meets Nectaris basin along Fecunditatis' western edge, with the area along this zone faulted by arcuated graben

Graben

In geology, a graben is a depressed block of land bordered by parallel faults. Graben is German for ditch. Graben is used for both the singular and plural....

s. On the eastern edge of Fecunditatis is the crater

Impact crater

In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

 Langrenus

Langrenus (crater)

Langrenus is a prominent impact crater located near the eastern lunar limb. The feature is circular in shape, but appears oblong due to foreshortening. It lies on the eastern shore of the Mare Fecunditatis...

. Near the center lie the interesting craters Messier A and B

Messier (crater)

Messier is a relatively young lunar impact crater located on the Mare Fecunditatis. The crater has a discernible oblong shape that is not caused by foreshortening. The longer dimension is oriented in an east–west direction....

.

Sinus Successus

Sinus Successus

The lunar feature Sinus Successus lies along the eastern edge of Mare Fecunditatis. It is an outward bulge that forms a type of bay. The selenographic coordinates of Sinus Successus are 0.9° N, 59.0° E, and the diameter is 132 km.Along the eastern edge of the bay is the flooded crater Condon,...

lies along the eastern edge of the mare.