TY - JOUR
T1 - Middle Jurassic sandstone deposition in the Wandel Sea Basin
T2 - Evidence from cardioceratid and kosmoceratid ammonites in the Mågensfjeld Formation in Kilen, North Greenland
AU - Alsen, Peter
AU - Hovikoski, Jussi
AU - Svennevig, Kristian
N1 - Publisher Copyright:
© 2020, GEUS - Geological Survey of Denmark and Greenland. All rights reserved.
PY - 2020
Y1 - 2020
N2 - Age assessments from both palynostratigraphy and macrofossil biostratigraphy of the sandstone-dominated Mågensfjeld Formation, Wandel Sea Basin, North Greenland were hitherto hampered by post-burial thermal degradation of dinoflagellate cysts and a lack of well-preserved macrofossils. The formation was previously assigned to the Upper Cretaceous based on erroneous fossil identifications. Finds of cardioceratid and kosmoceratid ammonites during recent field work now provide the first age control of the unit, demonstrating it to be of late Bajocian – late Bathonian and perhaps Callovian (Middle Jurassic) age. This makes it among the oldest Jurassic units, perhaps even Mesozoic units, recorded in Kilen, North Greenland and eastern North Greenland. Previously, the complex structural and tectonic evolution of the area was poorly understood, and the structural relation of the Mågensfjeld Formation to the surrounding Mesozoic units was a puzzle. The new age assessment simplifies the structural situation in the area significantly. Further, the inference of a large reverse fault previously required to explain the proximity of the Mågensfjeld Formation to neighbouring Jurassic units is now unnecessary. The data show that the Wandel Sea Basin was influenced by the Middle Jurassic transgression and had sufficient accommodation space for marine deposition earlier than previously thought. The unit serves as a key datapoint and analogue for possible Middle Jurassic units in adjacent offshore basins.
AB - Age assessments from both palynostratigraphy and macrofossil biostratigraphy of the sandstone-dominated Mågensfjeld Formation, Wandel Sea Basin, North Greenland were hitherto hampered by post-burial thermal degradation of dinoflagellate cysts and a lack of well-preserved macrofossils. The formation was previously assigned to the Upper Cretaceous based on erroneous fossil identifications. Finds of cardioceratid and kosmoceratid ammonites during recent field work now provide the first age control of the unit, demonstrating it to be of late Bajocian – late Bathonian and perhaps Callovian (Middle Jurassic) age. This makes it among the oldest Jurassic units, perhaps even Mesozoic units, recorded in Kilen, North Greenland and eastern North Greenland. Previously, the complex structural and tectonic evolution of the area was poorly understood, and the structural relation of the Mågensfjeld Formation to the surrounding Mesozoic units was a puzzle. The new age assessment simplifies the structural situation in the area significantly. Further, the inference of a large reverse fault previously required to explain the proximity of the Mågensfjeld Formation to neighbouring Jurassic units is now unnecessary. The data show that the Wandel Sea Basin was influenced by the Middle Jurassic transgression and had sufficient accommodation space for marine deposition earlier than previously thought. The unit serves as a key datapoint and analogue for possible Middle Jurassic units in adjacent offshore basins.
KW - Ammonite stratigraphy
KW - Middle Jurassic
KW - North Greenland
KW - Sandstone deposition
KW - Wandel Sea Basin
UR - http://www.scopus.com/inward/record.url?scp=85100818783&partnerID=8YFLogxK
U2 - 10.34194/geusb.v44.5342
DO - 10.34194/geusb.v44.5342
M3 - Article
SN - 1604-8156
VL - 44
JO - Geological Survey of Denmark and Greenland Bulletin
JF - Geological Survey of Denmark and Greenland Bulletin
M1 - 5342
ER -