In an attempt to interpret Ophiomorpha ichnofabrics observed in core, three ichnofabrics are described from outcrops where O. nodosa is a conspicuous element. These ichnofabrics enable sandy shoreline sedimentary environments to be characterized and differentiated: (1) shoreface with mottledOphiomorpha-Planolites ichnofabric generally without primary lamination; (2) offshore tidal shelf sand wave facies with Macaronichnus-Ophiomorpha ichnofabric associated with primary, mainly crosslaminated or cross-bedded sands; (3) estuarine facies with Ophiomorpha ichnofabric associated with primary lamination and, commonly, heterolithic sands and mudstones. Distinctions between the ichnofabrics are attributed to differences in primary stratification, the total ichnocoenoses, morphological features (such as burrow attitude, shaft restriction, pellet wall lining), to the nature of the substrate and, particularly, to the time available for colonization (larval settlement or relocation) and burrow construction, referred to here as the colonization window• The analysis is applied to an interval of core (Upper Jurassic, Central Graben, North Sea) and a sequence in Eocene sediments in southern England.Ophiomorpha nodosa Lundgren is one of the most widely quoted and widely known trace fossils. It is also a well-established and conspicuous trace fossil in shallow-marine sandy facies from the Mesozoic onwards. The principal account of its morphology and facies significance is by Frey et al. (1978).This pellet-lined burrow (Fig. 1) is today found over a range of~ nearshore environments, including lagoon and estuary floors, wherever the substrate consists mainly of sand grade sediment.

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The sedimentology and sequence stratigraphy of the Upper Jurassic (Upper Oxfordian — Middle Kimmeridgian) Fulmar Formation of the Kittiwake Field, Western Platform of the north Central Graben are investigated through an integrated study of core material and wireline logs. The Fulmar Formation, in this area, comprises largely finegrained sandstones which are intensely bioturbated such that the use of primary sedimentary structures for the identification of depositional environments is impractical. By using the approach of ichnofabric analysis presented here, the information provided by trace fossils can be fully utilized in the formulation of a depositional model for the Fulmar Formation. A depth and substrate-related succession of ichnofabrics was determined for the Fulmar Formation from more complete and progradational successions. This attached shoreface succession extends from a Chondrites ichnofabric (offshore), through Anconichnus (upper offshore), Anconichnus and spreiten burrows and ‘ Teichichnus zigzag ’ (upper offshore-offshore transition zone), bivalve tube ichnofabric (offshore transition zone to lower shoreface), Ophiomorpha irregulaire (lower shoreface), Ophiomorpha nodosa (middle shoreface) to a burrow mottling ichnofabric and associated high-energy laminated sandstones (upper shoreface). Anomalies in this succession form the basis for the identification of bounding surfaces, particularly omission surfaces ( Thalassinoides and Diplocraterion habichi ichnofabrics) and sequence boundaries. The distribution and evolution of the essentially retrogradational succession of the Fulmar sandstones is illustrated by analysis of a detailed core log of well 21/18-3, a general cross section through the Kittiwake Field and an Early-Mid-Kimmeridgian time slice facies distribution map.

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