Sedimentation at the Jurassic–Triassic boundary, south-west Barents Sea: indication of climate change - From Depositional Systems to Sedimentary Successions on the Norwegian Continental Margin - page 187

Sedimentation at the Jurassic-Triassic boundary, south-west
Barents Sea: indication of climate change

ALF RYSETH
Statoil Exploration and Production, Norway, PO Box 10, N-9414 Harstad
(E-mail: [e-mail])

ABSTRACT

Facies analysis of Upper Triassic to Lower Jurassic (Carnian to Sinemurian) strata in the
Barents Sea area shows that deposition took place in two widespread, fluvial-dominated,
delta plain settings, separated by a regional pro-deltaic mudrock of Early Norian age.
Comparison of alluvial architectural trends, combined with mineralogical data and other
published data, indicates that subsidence rates decreased across the Triassic to Jurassic
boundary in the south-west Barents Sea area, accompanied by palaeogeographic
re-configurations and rejuvenation of hinterlands to the south. Comparison with age-
equivalent strata in the North Sea and on the Halten Terrace to the south allows for a
discussion of possible regional climatic effects on deposition. It is inferred that the Late
Triassic climate comprised two zones; a dry and hot zone to the south and a much more
humid zone to the north. The Early Jurassic climate appears to be equable and generally
humid. It is suggested that hinterland rejuvenation, larger annual precipitation and
reduced subsidence rates combined to increase the grain size and sandstone content of
Early Jurassic delta plain deposits relative to the Late Triassic units in the Barents Sea area.

Keywords: Triassic, Jurassic, sedimentology, climate, Barents Sea.

INTRODUCTION evolution of the North Atlantic rift system, of

which the basins listed above are integral parts
(e.g. Doré, 1992). However, the Barents Sea area
(Fig. 2A) differs from the basins in the North Sea
and on the mid-Norway shelf by being influenced
by the younger (Late Palaeozoic to Mesozoic) fold-
ing in the Uralides to the east (Smelror et al . 2009).
Subsidence and sedimentation in the Barents
Sea area (Fig. 2A) commenced after the Caledonian
phase, with a general flow of sediment from west-
erly hinterlands to basins located to the east
(Worsley, 2008). By Carboniferous times, exten-
sional basins had started to form (Gudlaugsson
et al ., 1998; Worsley, 2008; Smelror et al ., 2009),
with possible initiation of several basins, includ-
ing the Tromsø and Bjørnøya basins to the west
and the Hammerfest and Nordkapp basins to the
east (Nilsen et al ., 1995; Breivik et al ., 1998;
Gudlaugsson et al . 1998). However, to the east,
continent collision between Baltica and the West
Sibirian Craton commenced during the Middle

Late Triassic to Early Jurassic strata on the
Norwegian shelf (Fig. 1) are documented in the
North Sea to the south (e.g. Vollset & Doré, 1984),
from basins offshore mid-Norway (Jacobsen & van
Veen, 1984; Dalland et al . 1988), and from the
Barents Sea to the north (Dalland et al . 1988;
Dallmann et al . 1999). Currently, the northern
North Sea (59º N to 62º N) and the south-west
Barents Sea (approximately 71º N to 72º N) are sep-
arated by more than 1500 km and by approximately
11º to 13º in latitudinal distance (Fig.1). However,
these basins are linked in time and space; particu-
larly, the Early Palaeozoic Caledonian collision
between Laurentia and Baltica (Gee et al ., 2008)
led to the development of a fold belt between
Norway and Greenland, with an arm extending
towards Svalbard (Worsley, 2008). Subsequently,
Late Palaeozoic collapse of the Caledonian Orogen,
followed by rift-related subsidence, led to the