Reconstructing the Siluro-Devonian coastline of Gondwana: insights from the sedimentology of the Port Stephens Formation,
Falkland Islands
M.A. Hunter
S.A. Lomas
10.6084/m9.figshare.3454163.v1
https://geolsoc.figshare.com/articles/dataset/Reconstructing_the_Siluro-Devonian_coastline_of_Gondwana_insights_from_the_sedimentology_of_the_Port_Stephens_Formation___Falkland_Islands/3454163
<p>Silurian and lower Devonian sedimentary successions are uncommon within the remnants of Gondwana. The Port Stephens Formation,
the basal unit of the middle Palaeozoic West Falkland Group, presents a rare opportunity to study Gondwanan material of Siluro-Devonian
age. The formation on West Falkland is <em>c</em>. 2560 m thick and consists of five members: Plantation, Albemarle, Mount Alice, South Harbour and Fish Creek. Thirty-five
lithofacies are defined using variations in grain size and bedding characteristics. The distribution of these lithofacies
and their associated ichnofacies between the various members lead us to suggest terrestrial and shallow marine deposition
on an extensive, gently shelving alluvial to coastal plain. Vertical facies trends through the Port Stephens Formation, and
into the base of the overlying Fox Bay Formation, record a complex superposition of subenvironments within a distinct overall
transgressive–regressive–transgressive pattern, with the bulk of sediment accumulating during the regressive phase. Palaeocurrents
indicate a basin to the present-day NE throughout. These results, together with lithostratigraphic correlations between the
Port Stephens Formation and the Nardouw Subgroup in South Africa, are consistent with a reconstructed position off eastern
South Africa and on the palaeo-Pacific margin of Gondwana, requiring a near-180° rotation of the Falkland Island microplate
during break-up, in agreement with previous models. We suggest that global changes in sea level during the mid–late Silurian
and early Devonian strongly influenced changes in the depositional environment. Enhanced erosion of the continental margin
and extensive sediment bypass during the regressive phase of this cycle could help to explain the low abundance of preserved
Gondwanan material of this age.
</p>
2016-06-21 11:56:48
Falkland Islands Silurian
study Gondwanan material
Fox Bay Formation
sediment
lithofacie
Vertical facies trends
Port Stephens Formation
Falkland Island microplate
NE
middle Palaeozoic West Falkland Group
Devonian
member
phase
South
Geology