Darriwilian

The Darriwilian is the upper stage of the Middle Ordovician. It is preceded by the Dapingian and succeeded by the Upper Ordovician Sandbian Stage. The lower boundary of the Darriwilian is defined as the first appearance of the graptolite species Undulograptus austrodentatus around 469.4 million years ago. It lasted for about 10.8 million years until the beginning of the Sandbian around 458.2 million years ago. This stage of the Ordovician was marked by the beginning of the Andean-Saharan glaciation.

Darriwilian
469.4 ± 0.9 – 458.2 ± 0.7 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Chronology
−485 — – −480 — – −475 — – −470 — – −465 — – −460 — – −455 — – −450 — – −445 — – P a l e o z o i c Ꞓ O r d o v i c i a n S F E a r l y M i d d l e L a t e L Stage 10 Tremadocian Floian Dapingian Darriwilian Sandbian Katian Hirnantian Rhuddanian       ← First land plant spores ← Ordovician meteor event Subdivision of the Ordovician according to the ICS, as of 2024. Vertical axis scale: Millions of years ago
Etymology
Name formality	Formal
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Age
Stratigraphic unit	Stage
Time span formality	Formal
Lower boundary definition	FAD of the Graptolite Undulograptus austrodentatus
Lower boundary GSSP	Huangnitang Section, Huangnitang Village, Changshan, Zhejiang, China 28°51′14″N 118°29′23″E / 28.8539°N 118.4897°E / 28.8539; 118.4897
Lower GSSP ratified	1997
Upper boundary definition	FAD of the Graptolite Nemagraptus gracilis
Upper boundary GSSP	Fågelsång section, Sularp Brook, Skåne, Sweden 55°42′49″N 13°19′32″E / 55.7137°N 13.3255°E / 55.7137; 13.3255
Upper GSSP ratified	2002

Naming

The name Darriwilian is derived from Darriwil, a parish in County of Grant, Victoria (Australia). The name was proposed in 1899 by Thomas Sergeant Hall.

GSSP

Huangnitang Section

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Map of China showing the GSSP location.

The GSSP of the Darriwilian is the Huangnitang Section (28°51′14″N 118°29′23″E / 28.8539°N 118.4897°E / 28.8539; 118.4897) near the village Huangnitang, 3.5 km southwest of Changshan County Town (Zhejiang, China). It is an outcrop of the Ningkuo Formation, consisting of mainly black shale. The lower boundary of the Darriwilian is defined as the first appearance datum of the graptolite species Undulograptus austrodentatus in that section.

A secondary fossil marker is the graptolite Arienigraptus zhejiangensis.

Biostratigraphy

The base of the Darriwilian is also the base of the Undulograptus austrodentatus graptolite zone. This zone lies just above the North Atlantic Microzarkodina parva conodont zone. The base also lies in the upper part of the North American Histiodella altifrons conodont zone.

The Undulograptus austrodentatus graptolite zone is known from outcrops around the world, making the base of the Darriwilian easily correlatable.

Regional stages

The Darriwilian overlaps with the upper Arenig and the Llanvirn. The base of the Darriwilian can be correlated with a level in the Fennian stage of the Arenig.

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