ABSTRACT In total, 33 and 65 chrome-spinel (Cr-spinel) grains in the >63 and 32–63 μm size fractions, respectively, were recovered from 12 beds in two stratigraphically separated groups along the 240-m-thick Monte Acuto section of the Maiolica limestone in central Italy, spanning from the Berriasian to the early Hauterivian. The chemistry of these detrital spinels suggests they may represent windblown ophiolitic detritus, showing the evolution of an ophiolite evolving from a mid-ocean-ridge basalt setting (Bosso section) to a suprasubduction-zone setting, including a backarc and an arc setting (Monte Acuto section). The source of the Maiolica detrital minerals may have been the obducting ophiolites of the Albanides and/or the Hellenides, which show a similar evolution. In this case, it is particularly important to note how the Cr-spinel detritus in the Maiolica limestone records this evolution over a relatively short period of time, lasting ~10 m.y.

Abstract The reservoir rock of the Schoonebeek oil field is formed by the sandstones of the Bentheim Sandstone Member. The sedimentology and depositional environment of this sandstone have been extensively studied, but the relationship between the geometry of the sandstone and tectonic activity in the Schoonebeek area remains poorly understood. 355 boreholes and two three-dimensional (3D) seismic surveys were used to study this relationship. An eroded zone in the west of the field and an area where the original depositional thickness is still intact were identified. Using the ezValidator software package it can be seen that uplift of a local anticline played an important role in the erosion of the sandstone. Deposition of the sands of the Bentheim Sandstone Member and the overlying Vlieland Sandstone and Claystone formations occurred on an unstable changing palaeotopography, whereby the instability was probably driven by halokinetic movement of the underlying Late Permian Zechstein salt. Syndepositional tectonic movements affected local thickness variations in the Bentheim Sandstone Member in the west of the field, leading to westwards thinning.

Abstract A biostratigraphical review of eight exploration boreholes located within the De Soto Canyon protraction area in the Gulf of Mexico yields a repeatable and predictive evolutionary and paleoecological sequence with implications to paleogeography. The Oxfordian section within these boreholes contains primitive planktic foraminifera such as Globuligerina oxfordiana. Near the end of the Kimmeridgian (or slightly above the nannofossil Calcivascularis cassidyi extinction), nannofossils are of low abundance, and dominated by Cyclagelosphaera spp. Weakly developed benthic foraminifera abundance gives rise to Reinholdella A which is coincident with a nannofossil dominance switch to Polycostella spp. Planktic foraminifera are not observed in this section In the overlying section, the extinction of nanno-fossil genus Polycostella , the origination and dominance of Nannoconus , and minute benthic foraminifera gradually increase. Here, the suggested datum, Polycostella beckmanii extinction, is observed consistently higher than the Reinholdella A extinction in the early Tithonian. The fossil assemblage change through this section suggests a change in water masses, which has implications to major reorganization in oceanic circulation. The Lower Cretaceous continues with multiple nannofossil originations that persist into the Valangin-ian. Here, a significant, diverse, and abundant benthic foraminifera and ostracod assemblage occurs in multiple, rapid abundance increases followed by gradual upward decreases, suggesting cyclical change in the shallower, upslope paleoenvironments. The cause of cyclical changes is unclear and may be the result of sea level change, progradation, and/or changes in ocean composition. The Hauterivian to Aptian section varies greatly in thickness with the maximum thickness in the northern De Soto Canyon area and thinning to the south. Nannoconus continues to dominate the nannofossil assemblage through the Aptian; benthic foraminifera and ostracods disappear rapidly during the Hauterivian and remaining sparse until the Albian when there is an increase of Nezzazata spp. The significance of these fossil sequences and respective assemblages are discussed in a paleoecological and paleogeographical context, which has implications to depositional history and correlation.

Abstract This study provides an assessment of two source-to-sink sediment routing systems of the Early Cretaceous and highlights sedimentologic changes that occurred in response to major tectonic reorganization of the eastern Gulf of Mexico during the Valanginian-Hauterivian stages. Depth-imaged 2D and 3D seismic data, well log correlation, sand grain size, and detrital zircon U-Pb data obtained from the Valanginian intervals of the cores of a key well, facilitates source-to-sink analysis of Early Cretaceous deep-water deposits, as well as construction of a new depositional model of Hosston equivalent-siliciclastics previously investigated only in the western Gulf of Mexico onshore areas. U-Pb dating of detrital zircon grains suggests that Hosston siliciclastics observed in the 200-km-long base-of-slope sandy progradational delta-fed apron at the Florida Escarpment originated in a peninsular Florida source terrane – the Ocala Arch. Interpretation of 3D seismic data with nearby well control also allows conclusions to be drawn about the Appalachian-sourced Hosston fan system in Mississippi Canyon. This Appa-lachian-sourced sandy fan is believed to have terminated updip of a series of salt-related asymmetric expulsion rollovers, although we know sediment accommodation in these inverted basins was not confined to the Valanginian-Hauterivian age Hosston interval and extended from the Jurassic Cotton Valley-Bossier supersequence to the Late Cretaceous Navarro-Taylor supersequence. Two plausible models of Appa-lachian-sourced fan length are considered, incorporating calculations of salt rafting to estimate a best-case scenario fan length of 90-km, while a more probable fan geometry is determined from seismic observations and well control, yielding a Valanginian-Hauterivian submarine fan of 70-km length. The study presents a new paleogeographic model, with special focus on the eastern Gulf of Mexico and the interpreted sand-prone fan and progradational delta-fed apron. It also provides a robust model for source to sink transport during a critical phase of Gulf of Mexico basin evolution. The shorter fan length calculated in this study suggest the majority of asymmetric expulsion rollovers in Mississippi Canyon are either sandstone-poor or were sourced from a different, likely younger, source-to-sink system ( e.g. , Late Cretaceous, Cenomanian-Turonian-age Tuscaloosa fluvial system).

Soft-sediment deformation structures crop out in the Lower Cretaceous succession of the Gubbio anticline in the Umbria-Marche Apennines of Italy. The deformation interval is ~13 m thick and occurs between the upper Hauterivian–lower Aptian Maiolica Formation and the Aptian Marne a Fucoidi Formation. It can be observed along the anticline for a distance of 12 km. Different types of deformation structures are distributed in several outcrops, with detachment extensional structures prevailing in the southeast sector. Imbricated slides, slump structures, and chaotic layers are distributed vertically and longitudinally in the middle and/or lower part of the deformed sediments. In the northwest sector of the anticline, compressional duplex structures can be considered the lower section of a large sediment failure. Geometrical and kinematic analysis of the fold axis trends and sliding surfaces have led to infer a single, large gravitational event possibly Albian in age. The synsedimentary deformation could be activated by several internal trigger mechanisms induced by external regional tectonic events such as earthquakes. An orthogonal system of calcite veins crossing the limestone layers represents the primary pathway for fluid-driven breaching of joint seals. These fluids can be related to the significant increase in the total organic carbon in the Hauterivian–Aptian layer of the Maiolica and Marne a Fucoidi Formations. This suggests the possibility that the limestone layer, sandwiched and sealed between clay of the organic-rich black shales, could have favored a pore pressure increase approaching lithostatic stress. With a thin overburden, lithostatic stress is more easily reached at low hydrostatic pressure. This slump sheet occurrence suggests the existence of a local paleoslope dipping toward the north-northwest, where the mass involved in the deformation is distributed over an estimated area of 60 km 2 for a volume of 0.8 km 3 of displaced sediments. The restoration and rotation of the slump fold hinges to the Early Cretaceous direction, in line with available paleomagnetic data, have shown that the strike of the slope corresponds to the main trend of the oldest Jurassic extensional lineaments and is linked to transform faults of the westernmost Tethys rifting systems.

Restoration of plate consumption recorded by Caribbean arc volcanism reveals probable plate movements that led to the emplacement of the proto–Caribbean plate into the present Caribbean region and provided the space necessary to accommodate the rotation of the Yucatán Peninsula concurrent with the opening of the Gulf of Mexico between ca. 170 Ma and 150 Ma. Fault movement of the Yucatán, caused by edge-driven processes, resulted in counterclockwise rotation, as shown by paleomagnetic studies. Restoration of Yucatán rotation necessitates the presence of a paleogeography different from the current distribution of the Greater and Lesser Antilles. During emplacement of the Caribbean plate region, four magmatic belts with distinct ages and different geochemical characteristics are recorded by exposures on islands of the Antilles. The belts distinguish the following segments of Cretaceous and Tertiary magmatic arcs: (1) an Early Cretaceous geochemically primitive island-arc tholeiite suite (PIA/IAT) typically containing distinctive dacite and rhyodacite that formed between Hauterivian and early Albian time (ca. 135–110 Ma); (2) after a hiatus at ca. 105 Ma of ∼10 m.y., a voluminous, more-extensive calc-alkaline magmatic suite, consisting mainly of basaltic andesite, andesite, and locally important dacite, developed beginning in the Cenomanian and continuing into the Campanian (ca. 95–70 Ma); (3) a second (calc-alkaline) suite, spatially restricted relative to the older belts, that consists of volcanic and intrusive rocks, which formed between the early Paleocene and the middle Eocene (ca. 60–45 Ma); and (4) a currently active calc-alkaline suite in the Lesser Antilles typically composed of a basalt-andesite-dacite series that began to develop in the Eocene (ca. 45 Ma). Plate convergence took place along northeastward- or eastward-trending axes during the formation of the Caribbean, which is outlined by the Antillean islands and Central and South America. Movements were facilitated by strike-slip faults, commonly trench-trench transforms, as subducting crust was consumed. Restoration of apparent displacements of at least several hundreds of thousands of kilometers along the inferred lateral faults of the Eocene and younger Cayman set separating Puerto Rico, Hispaniola, and the Oriente Province of southeastern Cuba brings together Eocene volcanic rocks revealing a magmatic domain along the paleo–south-southwestern margin of the Greater Antilles. The transforms along the southern margin of the Caribbean plate are mainly obscured by contractional deformation related to the northward motion of South America as it was thrust over the faulted plate margin. Restoration of the Caribbean plate also translates the Nicaragua Rise westward, thereby revealing a pathway along which Pacific oceanic lithosphere, mainly composed of a large, Late Cretaceous igneous province (Caribbean large igneous province), manifest as an oceanic plateau (Caribbean-Colombian oceanic plateau), converged toward and subducted beneath the southern flank of the Cretaceous Greater Antilles magmatic belt between 65 and 45 Ma. The Eocene arc rocks overlie or abut previously recognized Early and Late Cretaceous subduction-related units. Eocene consumption of Pacific lithosphere ceased with the arrival, collision, and accretion of buoyant lithosphere composed of Caribbean large igneous province. The Greater Antilles formed during Late Cretaceous subduction of Jurassic ocean crust beneath an Early Cretaceous arc formed at the eastern margin of the proto–Pacific plate. Formation of a volcanic edifice above Early Cretaceous arc rocks was followed by plate collision and coupling of the Greater Antilles belt against the Bahama Platform. The most straightforward path of the Greater Antilles into the Caribbean is along northeast-striking transforms, one of which coincided with the eastern margin of the Yucatán Peninsula. The transform appears to link the Motagua suture to the Pinar del Rio Province of western Cuba. To the southeast, the arc was transected by a second transform, perhaps coinciding with the present trace of the Romeral fault in northwestern South America and extending northeast to the eastern terminus of the Virgin Islands. During Late Cretaceous convergence, a segment of the extinct Early Cretaceous arc, developed at the Pacific margin, was carried northeastward.