A Giant Sand Injection Complex: The Upper Jurassic Hareelv Formation of East Greenland

A major intrusive sandstone complex of Late Jurassic age is spectacularly exposed in Jameson land, East Greenland. It is probably the largest in the World, and covers an area of 55x70 km with a thickness of 200–400 m, and forms the Upper Oxfordian–Volgian Hareelv Formation. The complex consists of black basinal mudstones and highly irregular sandstone bodies, dykes and sills. The sand was derived from collapse of the front of sandy shelf-margin wedges, which triggered hyperconcentrated to concentrated density flows, and deposited massive sands further down the slope, at the base-of-slope and in the basin. The sand of some flows was loaded into the slope muds while elsewhere it flowed in steep-sided gullies formed by retrogressive slumping of the slope muds. All sand bodies were liquefied subsequent to burial and the sand was intruded into the surrounding black compacted muds and mudstones. Intrusion took place repeatedly over a long time interval, in environments ranging from very shallow to relatively deep burial, and the primary sediment structures of the sands were generally lost during these processes. It is rarely possible to determine the degree of post-burial remobilization but it ranges from rather small-scale modifications to wholesale liquefaction and out-of-place intrusion of the sand over many tens of metres. Sandstone dykes and sills occur ubiquitously and were emplaced by all combinations of stoping and dilation. The intrusive sand bodies range in dimensions from centimetres to many hundreds of metres. Deposition took place during the most important Mesozoic rift event in East Greenland and the pervasive remobilization and liquefaction of all sand bodies in the Hareelv Formation is interpreted as having been caused mainly by cyclic earthquake shocks. Additional important factors were slope shear stress, build up of pore pressure due to loading, slumping, upwards movement of pore waters expelled from the compacting muds, and also possibly of biogenic and thermogenic gas. The Hareelv Formation is an excellent field analogue for deeply buried hydrocarbon reservoirs, which have been modified by remobilization and injection of the sands

Shelf-edge delta and slope deposition in the Upper Callovian – Middle Oxfordian Olympen Formation, East Greenland

The Upper Bajocian – Upper Volgian succession of the Jameson Land Basin in East Greenland forms an overall transgressive–regressive cycle. The Upper Callovian – Middle Oxfordian Olympen Formation represents the first regressive deposits after maximum flooding in the Middle to early Late Callovian. The formation was deposited during two southwards progradational phases separated by a major drowning event in the Early Oxfordian. The first phase was marked by incoming of massive slope and base-of-slope sand (Athene Member), but the delta front and top did not reach the area of present-day exposure. The second phase was initiated by deposition of a thick mud succession (Hades Member) indicating that the delta had shifted far to the north during the drowning event. Southwards progradation of the delta was heralded by gully erosion and the deposition of lenticular bodies of massive slope sand; on this occasion, medium- and largescale cross-bedded sand of the delta front and top (Zeus Member) reached the area. The boundary between Middle–Upper Callovian mudstones in the upper part of the underlying Fossilbjerget Formation and the Upper Callovian Athene Member sandstones formed at the turn-around point between sea-level rise and fall. The Athene Member sandstones are interpreted as an undifferentiated falling stage – lowstand systems tract and span a sequence boundary. The top of the Athene Member is the basinal correlative of the transgressive surface. The basal few metres of the overlying Hades Member mudstones represent the transgressive systems tract and a level with organic-rich mudstones is interpreted to represent the maximum flooding zone. The remainder of the Hades Member and the slope sandstones are assigned to the highstand systems tract. The succeeding cross-bedded delta front sandstones of the Zeus Member are placed in the falling stage systems tract and their sharp base is interpreted as a marine regressive surface of erosion. Comparison of this history with published sea-level curves suggests that the short term changes may be eustatic in origin including the Middle Callovian maximum flooding (K. jason – lower P. athleta Chronozones), Late Callovian regression (P. athleta – Q. lamberti Chronozones), latest Callovian – Early Oxfordian flooding (Q. mariae – C. cordatum Chronozones) and late Early – Middle Oxfordian regression (C. densiplicatum Chronozone)

Maximum Middle Jurassic transgression in East Greenland: evidence from new ammonite finds, Bjørnedal, Traill Ø

A Middle – lower Upper Jurassic sandstone-dominated succession, more than 550 m thick, with mudstone intercalations in the middle part is exposed in Bjørnedal on Traill Ø, North-East Greenland. A number of ammonite assemblages have been found, mainly in the mudstones. They indicate the presence of the Lower Callovian Cadoceras apertum and C. nordenskjoeldi Chronozones. The mudstones represent northern wedges of the Fossilbjerget Formation hitherto known only from Jameson Land to the south. In Bjørnedal they interfinger with sandstones of the Pelion and Olympen Formations. The presence of the Fossilbjerget Formation in this region indicates complete drowning of the Middle Jurassic sandstone-dominated Pelion Formation during maximum Middle Jurassic transgression. A new species, Kepplerites tenuifasciculatus, is described in the appendix by J.H. Callomon. The holotype and paratype are from Jameson Land, East Greenland, but the species is also found in Bjørnedal, Traill Ø, North-East Greenland

The fluviatile Bristol Elv Formation, a new Middle Jurassic lithostratigraphic unit from Traill Ø, North-East Greenland

A new lithostratigraphic unit, the Bristol Elv Formation, is erected in this paper. It is only known from Traill Ø, East Greenland, where it unconformably overlies Triassic redbeds of the Fleming Fjord Formation and is overlain by lithologically similar shallow marine Upper Bajocian sandstones of the Pelion Formation. The age of the formation is not well constrained but is probably Early Bajocian. The Bristol Elv Formation is at least 155 m thick and consists of conglomerates, coarse-grained pebbly sandstones and subordinate mudstones, deposited in braided rivers. A finer-grained lacustrine/floodplain unit, c. 37 m thick, is interbedded with the fluvial sandstones at one locality. Deposition of the fluvio-lacustrine Bristol Elv Formation marks a major change in basin configuration and drainage patterns, reflecting the onset of the important, protracted Middle–Late Jurassic rift event in East Greenland

Stratigraphy and sedimentology of a basement-onlapping shallow marine sandstone succession, the Charcot Bugt Formation, Middle–Upper Jurassic, East Greenland

A rocky shore developed in early Middle Jurassic times by transgression of the crystalline basement in Milne Land at the western margin of the East Greenland rift basin. The basement is onlapped by shallow marine sandstones of the Charcot Bugt Formation, locally with a thin fluvial unit at the base. The topography of the onlap surface suggests that a relative sea-level rise of at least 300 m took place in Early Bathonian – Middle Oxfordian times. The sea-level rise was punctuated by relative stillstands and falls during which progradation of the shoreline took place. Palynological data tied to the Boreal ammonite stratigraphy have greatly improved time resolution within the Charcot Bugt Formation, and the Jurassic succession in Milne Land can now be understood in terms of genetically-related depositional systems with a proximal to distal decrease in grain size. The sequence stratigraphic interpretation suggests that translation of the depositional systems governed by relative sea-level changes resulted in stacking of sandstone-dominated falling stage deposits in the eastern, basinwards parts of Milne Land, whereas thick, remarkably coarse-grained transgressive systems tract deposits formed along the western basin margin. The bulk of the Charcot Bugt Formation consists of stacked sandstone-dominated shoreface units that prograded during highstands. The overall aggradational to backstepping stacking pattern recognised in the Charcot Bugt Formation is comparable to that in the contemporaneous Pelion Formation of the Jameson Land Basin and in correlative units of the mid-Norway shelf and the Northern North Sea. We suggest that the long-term evolution of the depositional systems may have been controlled by long-term eustatic rise acting in concert with relative sea-level changes reflecting regionally contemporaneous phases of rift initiation, climax and gradual cessation of rifting