Promicroceras Calcite Ammonite Fossil Pebble Jurassic Lyme Regis Dorset UK Lower Lias

Description

Genuine Promicroceras Calcite Ammonite Pebble from the Jurassic Coast

Offered here is a genuine Promicroceras calcite ammonite fossil pebble from the famous Black Ven Marls, Black Ven, Charmouth and Lyme Regis, Dorset, part of England’s internationally protected Jurassic Coast. This specimen has been carefully selected for quality, clarity, and natural presentation, with the ammonite preserved within a compact pebble of original marine sediment. The photographs show the exact fossil you will receive, and full sizing details can be seen in the images.

This fossil is a genuine specimen and includes a Certificate of Authenticity lifetime guarantee generic card, ensuring long-term confidence in provenance and collectability.

Geological Formation and Age

This ammonite pebble originates from the Lower Lias Group, deposited during the Early Jurassic Period, approximately 199–191 million years ago, within the Sinemurian Stage. The Black Ven Marls were formed in a shallow epicontinental sea that once covered much of southern Britain. Fine muds and calcareous sediments accumulated slowly on the sea floor, creating ideal conditions for the preservation of ammonites. Black Ven is one of the most important Lower Jurassic fossil localities in Europe, renowned for its abundance, diversity, and stratigraphic continuity.

Fossil Type, Species, and Scientific Context

Promicroceras is a classic Early Jurassic ammonite genus belonging to the Order Ammonitida, Superfamily Eoderoceratoidea, and Family Echioceratidae. This genus is widely recognised as an index fossil and is closely associated with the Promicroceras planicosta Biozone, a key biostratigraphic marker within the Lower Lias. Specimens of Promicroceras are highly valued for their role in dating and correlating Early Jurassic marine sediments, making even small, well-preserved examples scientifically meaningful.

Morphology and Calcite Preservation

The ammonite within this pebble displays the characteristic planispiral, evolute coiling typical of Promicroceras, with visible whorls and distinct ribbing preserved through calcite mineralisation. The ribbing often appears bold and evenly spaced, gently curving across the flanks of the shell. Calcite replacement enhances durability and highlights surface detail, creating a strong contrast between the fossil and the surrounding matrix. The pebble form provides a naturally smooth, tactile finish while preserving the fossil’s original structure.

Depositional Environment

During the Early Jurassic, the Charmouth and Lyme Regis area lay beneath a warm, shallow marine environment rich in ammonites, fish, and marine reptiles. Fine sediments settled gradually on the sea floor, allowing shells to be buried before significant disturbance. Periodic low-oxygen conditions reduced scavenging and decay, contributing to the excellent preservation of ammonites within the Black Ven Marls. Subsequent coastal erosion has naturally rounded some fossils into pebbles, creating compact specimens such as this one.

Collecting, Display, and Educational Value

This Promicroceras calcite ammonite fossil pebble is ideal for collectors, educational use, gifting, or display. Its compact size, classic British provenance, and clear geological context make it an accessible yet scientifically important fossil. Pebble-preserved ammonites from Lyme Regis are particularly popular due to their natural finish and durability, making them suitable for both handling and long-term display. Each specimen we offer is individually chosen, ensuring you receive an authentic and carefully curated piece of Early Jurassic marine history from one of the world’s most celebrated fossil localities.