The Greenland‐Norwegian Seaway: A key area for understanding Late Jurassic to Early Cretaceous paleoenvironments

Abstract

[1] The paleoclimatology and paleoceanology of the Late Jurassic and Early Cretaceous are of special interest because this was a time when large amounts of marine organic matter were deposited in sediments that have subsequently become petroleum source rocks. However, because of the lack of outcrops, most studies have concentrated on low latitudes, in particular the Tethys and the ''Boreal Realm,'' where information has been based largely on material from northwest Germany, the North Sea, and England. These areas were all south of 40°N latitude during the Late Jurassic and Early Cretaceous. We have studied sediment samples of Kimmeridgian ($154 Ma) to Barremian ($121 Ma) age from cores taken at sites offshore mid-Norway and in the Barents Sea that lay in a narrow seaway connecting the Tethys with the northern polar ocean. During the Late Jurassic-Early Cretaceous these sites had paleolatitudes of 42-67°N. The Late Jurassic-Early Cretaceous sequences at these sites reflect the global sea-level rise during the Volgian-Hauterivian and a climatic shift from warm humid conditions in Volgian times to arid cold climates in the early Hauterivian. The sediments indicate orbital control of climate, reflected in fluctuations in the clastic influx and variations in carbonate and organic matter production. Trace element concentrations in the Volgian-Berriasian sediments suggest that the central part of the Greenland-Norwegian Seaway might have had suboxic bottom water beneath an oxic water column. Both marine and terrigenous organic matter are present in the seaway sediments. The Volgian-Berriasian strata have unusually high contents of organic carbon and are the source rocks for petroleum and gas fields in the region. The accumulation of organic carbon is attributed to restricted conditions in the seaway during this time of low sea level. It might be that the Greenland-Norwegian segment was the deepest part of the transcontinental seaway, bounded at both ends by relatively shallow swells. The decline in organic matter content of the sediments in the Valanginian-Hauterivian indicates greater ventilation and more active flow through the seaway as the sea level rose. The same benthic foraminifera assemblages are encountered throughout the seaway. Endemic assemblages of arenaceous foraminifera in the Volgian-Berriasian give way to more diverse and cosmopolitan ValanginianHauterivian benthic communities that include calcareous species. The foraminiferal assemblages also suggest low oxygen content bottom waters during the earlier Cretaceous, changing to more fully oxygenated conditions later. The calcareous nannoplankton, particularly Crucibiscutum salebrosum, which is rare at low latitudes and abundant in high latitudes, reflect the meridional thermal gradient. They indicate that the Greenland-Norwegian segment of the seaway was north of a subtropical frontal zone that acted as a barrier between the Tethyan and Boreal Realms. This implies the existence of stable climatic belts during the early Valanginian and Hauterivian, signif...

Paleoenvironment and sea-level change in the early Cretaceous Barents Sea?implications from near-shore marine sapropels

“…Espitalie´et al 1977;Peters 1986). Thermal immaturity of the organic matter is evident in T MAX values of 410-430°C (Langrock and Stein 2001;Mutterlose et al 2003).…”

“…In addition to the organic matter, all major and trace elements were determined by XRF and/or ICP-MS analysis (see Mutterlose et al 2003), but in this paper only Mo/Al ratios were used to indicate bottom-water anoxia. To support this, pyrite size distribution is used for evaluating bottom-water redox conditions in ancient sedimentary rocks (e.g., Wilkin et al 1996Wilkin et al , 1997.…”

“…This increased the prominence of shallow marine basins along the continental shelf, thereby promoting the development of restricted depositional environments, and favored the accumulation and preservation of organic matter (e.g., Demaison and Moore 1980). As a result, dark-colored, organic carbon-rich sediments, so-called black shales, occurred widely during this period, for example, in the marginal seas of the North Atlantic (e.g., Schlanger and Jenkyns 1976;Stein et al 1986;De Graciansky et al 1987), along the Norwegian-Greenland Seaway (e.g., Dore´1991; Smelror et al 2001;Mutterlose et al 2003), and in the adjacent Barents Sea (e.g., Bugge et al 1989Bugge et al , 2002. The formation of black shales is often attributed to ''oceanic anoxic events'' (OEAs) on a global scale, for example, during the Cenomanian/Turonian which is characterized by a relatively high sea-level stand (e.g., Arthur et al 1987;Erbacher et al 2001).…”

Exploring the long-term Cenozoic Arctic Ocean climate history: a challenge within the International Ocean Discovery Program (IODP)

“…One prerequisite of this extreme paleoenvironmental situation was the paleogeographic boundary setting, i.e., the early Arctic Ocean was isolated from the world ocean in terms of deep-water connections ( Fig. 5; [13,54,89,112]). Furthermore, the huge freshwater discharge has favored the development of widespread salinity stratification resulting in a poor ventilation of the subsurface, deeper water masses and causing the high OC preservation rate.…”

Allogenic and autogenic processes combined in the formation of shallow-water carbonate sequences (Middle Berriasian, Swiss and French Jura Mountains)

“…For the Middle Berriasian, a change from a semiarid, Mediterranean-type climate to more humid conditions has been postulated for Central Europe mainly based on clay mineralogy (Deconinck 1987;Hallam et al 1991;Pasquier 1995). This climate shift may have been related to changes of surface currents on the European archipelago and to the opening of the proto-North Atlantic Ocean (Abbink et al 2001;Mutterlose et al 2003). On the shallow Jura platform, organic and inorganic carbonate productivity was generally high, producing lagoonal and peritidal facies as well as bioclastic and oolitic shoals and coral patch reefs (Pasquier 1995;Hillgärtner 1999;Tresch 2007).…”