Storm depositional systems. Dynamic stratigraphy in modern and ancient shallow-marine sequences

Abstract Late Devonian coarse-grained carbonate deposits in the Holy Cross Mountains were studied for possible storm depositional systems and catastrophic tsunami events, as it must be assumed that the investigated area was strongly affected by tropical hurricanes generated in the open ocean North of Gondwana. This assumption appears consistent with diagnostic features of carbonate tempestites at several places in the Holy Cross Mountains. Sedimentary structures and textures that indicate so are, among other evidence, erosional bases with sole marks, graded units, intra- and bioclasts, different laminations and burrowing at the tops of tempestite layers. It has been suggested before that a tsunami occurred during the Late Devonian, but the Laurussian shelf had an extensional regime at the time, which excludes intensive seismic activity. The shelf environment also excluded the generation of tsunami waves because the depth was too shallow. Additionally, the Holy Cross Mountains region was surrounded in the Devonian by shallow-marine and stable elevated areas: the Nida Platform, the Opatkowice Platform and the Cracow Platform to the South, and the elevated Lublin-Lviv area to the NE. Thus, tsunami energy should have been absorbed by these regions if tsunamites would have occurred.

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

Geological Survey of Denmark and Greenland Bulletin ◽

10.34194/geusb.v1.4693 ◽

2003 ◽

Vol 1 ◽

pp. 893-930 ◽

Cited By ~ 2

Author(s):

Michael Larsen ◽

Stefan Piasecki ◽

Finn Surlyk

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Upper Jurassic ◽

Sea Level Changes ◽

Relative Sea Level ◽

Western Basin ◽

Shallow Marine ◽

East Greenland ◽

Depositional Systems

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 coarsegrained 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.

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