Eustatic, tectonic and climatic controls on an early syn-rift mixed-energy delta, Tilje Formation (Early Jurassic, Smørbukk field, offshore mid-Norway) - From Depositional Systems to Sedimentary Successions on the Norwegian Continental Margin - page 353

(A) (B) (C)

10

15

15

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5

5

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P

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(D) (E) (F)

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Ar

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5 Ch

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Fig. 6. Sandstone-dominated and mixed sandstone/mudstone heterolithics in the Smørbukk field. Sandstone-dominated
heterolithics (Facies 5.1): (A) Thin conglomerate layers interbedded with cross-bedded and ripple cross-laminated sand-
stones and 2 cm to 3 cm thick homogeneous mudstone layers (white arrows) that are interpreted as fluid-mud deposits;
(B) Ripple-cross laminated sandstone showing stylolites, interbedded with thin mudstone laminae showing double-mud-
stone drapes (white arrows); (C) Ripple cross-laminated sandstone interbedded with 0.2 cm to 0.3 cm thick double mudstone
layers (white arrows) with scarce bioturbation mainly dominated by Planolites ( P ). Mixed sandstone/mudstone heterolithics
(Facies 5.2.1): (D) Ripple cross-laminated sandstone interbedded with 0.5 cm to 1 cm thick mudstone showing sparse
(BI 0-1), moderate-diversity bioturbation, predominantly showing Chondrites ( Ch ), Planolites ( P ), Palaeophycus ( Pa ),
Rhizocorallium ( Rh ) and Teichichnus ( Te ); (E) Wavy-bedded heterolithics showing current-ripple and combined-flow ripple
cross-laminated sandstone interbedded with 1 cm to 3 cm thick homogeneous mudstone; notice the vertical gradation from
the fine-grained ripple cross-laminated sandstone into laminated siltstone to homogeneous unbioturbated mudstone (fluid
muds; white arrows). Mixed sand/mud heterolithics (Facies 5.2.2): (F) Round-crest ripples and ripple cross-laminated sand-
stone with basal coarse sand lenses and/or dispersed coarse sand grains (white arrows) and 0.5 cm to 2 cm thick poorly lami-
nated to homogeneous mudstone showing weakly bioturbated tops (BI 1) suggesting river flood periods, interbedded with
moderately to intensely (BI 3-4) bioturbated sandstones and laminated mudstone representing inter-flood deposits. Common
trace fossils include Chondrites ( Ch ), Planolites ( P ), Palaeophycus ( Pa ), Skolithos ( Sk ), Teichichnus ( Te ), Arenicolites ( Ar )
and 'mantle and swirl (ms)' structures (cf. Bhattacharya & MacEachern, 2009). Such alternation between weakly bioturbated
and moderately bioturbated intervals is interpreted to have a seasonal origin (see text for discussion).