Abstract This chapter describes uppermost Middle Jurassic–lowermost Cretaceous second-order stratigraphic sequences J40, J50, J60 and J70, and their component third-order sequences J42–J46, J52–J56, J62–J66 and J71–J76. The latest Callovian–Berriasian was an interval of significant tectonism that led to the development of complex stratigraphy and highly variable successions, the elucidation of which is aided by the recognition of the correlation of the J sequences. Marine sedimentation dominated the Callovian–Berriasian interval, with the development of multiple sandstone members comprising reservoir units in many hydrocarbon fields, charged by marine source rocks (e.g. the Kimmeridge Clay Formation). Each of these units is subdivided and correlated by a succession of J sequences. Several sequences are renumbered (e.g. J54, J55, J65 and J66), some sequence definitions are amended or their basal boundaries recalibrated chronostratigraphically (J52, J54, J72, J73, J74 and J76) and new sequence subdivisions are recognized (J64a, J64b, J72a–J72c, J73a and J73b). Significant unconformities are recognized at the bases of the J54, J55, J62, J63, J64, J71 and J73 sequences. The top of J70 (J76) equates to the major ‘Base Cretaceous Unconformity’ seismic sequence boundary.

Abstract Extensional rift basin systems have been a focus of study for hydrocarbon exploration and have provided significant economic reserves in recent decades, which has led to advances in our understanding of their tectono-sedimentary evolution. However, with the increasing maturity of such settings, focus is shifting from pre-rift structures to the underexplored syn- and late-rift plays. This change in focus brings with it a significant increase in complexity when trying to develop an integrated understanding of the sedimentological, sequence stratigraphic and structural conditions that control the distribution of syn-rift reservoirs. Here we present a subsurface example from offshore Norway of a small, confined, syn-tectonic basin sourced from a local basement high. 3D seismic data, sedimentary facies analysis and stratigraphic correlations based on well and core data from six key wells constrain the local and regional tectonic controls. The PL586 licence partners drilled several wells between 2014 and 2015 targeting syn-rift Upper Jurassic stratigraphy on the southern Halten Terrace. The wells penetrated a complete syn-rift stratigraphic sequence, which provided an excellent subsurface record of the inherent complexities encountered in small, confined (3 by 5 km) syn-rift basins. Seismic data reveals that the Late Jurassic hanging-wall basin architecture and the footwall hinterland of the Frøya High were controlled by activity on the basin-bounding Vingleia Fault Complex. Facies analysis from well and core data reflects a complete syn-rift succession. The early-rift succession comprises mainly mud and siltstone with minor fine-grained sandstones interpreted to be deposited by sediment gravity flows in isolated mini-basins. The peak-rift deposits comprise coarse-grained sediment gravity flows that were sourced locally from the uplifting footwall and deposited as coarse-grained submarine fan systems in the immediate hanging wall. Significant footwall uplift during the peak-rift phase resulted in fault scarp instability and the emplacement of several large landslide complexes into the basin. The late-rift phase is dominated by a mud-rich sequence with minor coarse-grained apron fans shedding sediment off the basin bounding fault and shoreface deposits flanking the hanging-wall dip-slope and subtle intra-basinal highs. This subsurface study from the southern Halten Terrace is significant in the number of wells that have specifically targeted syn-rift stratigraphy and the level of detail at which it captures the stratigraphic variability of these deposits within a small, confined basin system. Integration of seismic geomorphology and well data with robust provenance, dating and stratigraphic correlation has enabled the development of a tectono-stratigraphic model specific to the scale and local tectonic setting. The model reveals that structural evolution ultimately controlled the development of sediment supply routes, their age and distribution, and allows several conclusions to be drawn: The stratigraphy of small, confined syn-rift basins is broadly comparable with more typically documented larger syn-rift settings, although lateral facies changes occur more rapidly. The cannibalistic nature of syn-rift systems, where a large volume of pre- and syn-rift sediments are uplifted and eroded then rapidly re-deposited makes determining the relative age of laterally variable depositional settings difficult. In order to adequately constrain the timing and depositional extent of syn-rift stratigraphy, it is essential to understand the structural evolution of the system and integrate this information with other disciplines and datasets. This integrated understanding will ultimately improve predictions of reservoir presence and quality.

Abstract Fossil clam shrimp are widely distributed in the Jurassic terrestrial sediments of China. The Yanliao Biota, consisting of abundant and diverse well-preserved fossil vertebrates and invertebrates, is one of the most famous Mesozoic terrestrial biotas from around the world. The border area between western Liaoning, northern Hebei and southeastern Inner Mongolia is the core area for the biota. Clam shrimp are abundant and widely distributed in different localities in the area. Research on these clam shrimp has been conducted for decades. However, with advances in research instruments and technologies, great changes have taken place in the taxonomy of these clam shrimp and, consequently, our understanding of the biota in recent years. The fossil content of the Yanliao Biota in the core area consists of an early assemblage and a late assemblage, which are characterized by distinctly different clam shrimp. These clam shrimp all belong to one family: Triglyptidae. Members of the family are widely distributed in the Bathonian to Kimmeridgian of northeastern, northwestern and southwestern China.