Abstract
The sedimentary sequence in the platform area (approx. 2500 km2) around Jørgen Brønlund Fjord, North Greenland, has been mapped, and sections through the Precambrian, Eocambrian and Lower Palaeozoic sequence are described. After a summary of the previous geological field work carried out in the area, a lithological description of a composite section through the sequence below the Lower Cambrian Brønlund Fjord Dolomite (Troelsen, 1949) is given. This sequence, which is about 1000 m thick, is divided into four formations – in ascending order: Inuiteq Sø Formation (sandstone), Morænesø Formation (tillite and dolomite), Portfjeld Formation (dolomite) and Buen Formation (sandstone and shale). The first three named formations are separated by two unconformities both representing a long period of erosion. The strata are cut by two dolerite sequences, of which the older (the Midsommersø dolerites) is of Precambrian age and intrudes only the Inuiteq Sø Formation. Intrusions of the younger sequence penetrate all the strata in the Jørgen Brønlund Fjord area and are regarded as post-Palaeozoic. In the last section the chronostratigraphy and the correlation with neighbouring areas are discussed. Special attention is given to the two newly discovered erosional unconformities, which together with the tillite occurrence and the radiometric K/Ar dated Midsommersø dolerites, throw new light on the stratigraphy of North Greenland.
Highlights
A S a member of the 4th and 5th Danish Peary Land Expeditions led 11... by Count EIGIL KNUTH in 1966 and 1968, the present writer carried out geological field work in the southern part of Peary Land around Jørgen Brønlund Fjord, Midsommersøer, and Inuiteq Sø
The sediments are cut by numerous basic intrusions, which ean be divided into an older Precambrian sequence and ayounger sequence, which is regarded as post-Palaeozoic
The Danish Bicentenary Expedition under the leadership of LAUGE KOCH stayed in Jørgen Brønlund Fjord and Independence Fjord in 1921
Summary
The Jørgen Brønlund Fjord area was first visited in 1907 by 3 members of the disastrous Danmark Expedition. Stratigraphy of Jørgen Brønlund Fjord area sequence, but he did not succeed in detecting an erosional unconformity between that sequence and the overlying Cryptozoon-Kalk. 71-72), he gave the pre-tiIIitic sandstone a Precambrian age Since he regarded the Thule Group as belonging to the Eocambrian, that group came to contain only those sediments between the lower boundary of the tillite and the lower boundary of the Lower Cambrian Brønlund Fjord Dolomite. During the stay of the Danish Peary Land expedition in the Jørgen Brønlund Fjord area ELLITSGAARD-RASMUSSEN carried out geological field work in the area during 1949-50, and a part of this work was concentrated on a petrological examination of the intrusions in the lower sandstone sequence (Midsommersøer, Independence Fjord) (ELLITSGAARD-RASMUSSEN, 1950). The bottoms of all the larger valleys have very few bedrock exposures, but the mountain sides are very well exposed, which makes the measuring and correlation of stratigraphical sections very easy
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