New Zealand Journal of Geology & Geophysics abstracts
The ammonite genus Harpoceras (Early Jurassic) in New
Zealand
G. R. Stevens
GNS Science
PO Box 30368
Lower Hutt 5040, New Zealand
Abstract Harpoceras subplanatum (Oppel,
1856) is
recorded from two localities in the North Island of New Zealand. The
localities occur in strata of the Ururoan Stage of the New Zealand
local stage sequence, correlated internationally with the Pliensbachian
and Toarcian. Elsewhere in the world, notably in Europe and South
America, H. subplanatum occurs in the Bifrons Zone of the Early
Toarcian, ranging throughout the middle and upper parts of the
Fibulatum Subzone. The presence of H. subplanatum in New
Zealand provides an international correlation point for the middle of
the Ururoan Stage.
Harpoceras subplanatum
achieved a wide distribution in Europe, extending from England to the
Caucasus. It also became distributed in the circum-Pacific region with
occurrences in North and South America, Japan, and New Caledonia. The
New Zealand occurrences are considered to be a component of this
circum-Pacific distribution.
The widespread distribution of H.
subplanatum was probably facilitated by the availability of various
migratory seaways (e.g., Viking and Hispanic Corridors), made more
accessible by the Early–Middle Toarcian eustatic rise in sea level.
Keywords Harpoceras subplanatum
(Oppel, 1856); Early
Jurassic; Early Toarcian; Bifrons Zone; Fibulatum Subzone; Pacificum
Zone; Chilensis Zone; Ururoan Stage; Ururoa Formation; Dactylioceras;
Gondwana; Tethys; Murihiku Terrane; Rangitata Orogeny; Kawhia Harbour;
Taharoa; Awakino River; Kawhia Regional Syncline; Hispanic Corridor;
Viking Corridor; circum-Pacific migration routes; eustatic rises in sea
level.
G07017; Online publication date 30 October 2007; Received 12 July
2007; accepted 19 October 2007
New Zealand Journal of Geology & Geophysics, 2007, Vol. 50:
377–386
0028–8306/07/5004–0377 © The Royal Society of New Zealand 2007
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