The James Cresswell (UK) geologyof East Greenland ighty percent of Greenland is covered by ice and, in places, Ethis is up to 3.4km thick. So, Greenland might not immediately spring to mind as a place to go to observe rocks. However, it is a huge country and the ice-free area, at 410,000km2, is nearly twice the size of the UK. This is generally sparsely vegetated, leaving the rocks beautifully exposed and the geology incredibly easy to see. The area of East Greenland around Scoresby Sund, Kong Oscar and Kejser Franz Joseph Fjords is the largest ice-free area in Greenland. It also has incredible geodiversity, with basement rocks as old as three billion years, an almost complete sedimentary record of the last 1.6byrs and huge volumes of flood basalts from the splitting of the Atlantic. If you were an alien and wanted to try to piece together the geological story of Planet Earth - but could only visit one area - East Greenland would be the place to go. The geological history of Greenland is vastly long and spans 3.8byrs. Its oldest rocks are the 3.8byr-old Isua Complex, situated in West Greenland, near the capital Nuuk. These rocks are the Earth’s oldest, Fig 1. A simplified geological map of East Greenland. most well-preserved sedimentary granites) are continental crust and Greenland rifted apart again, only to and volcanic rocks, and they contain in all continental collisions, they are come back together 200myrs later. carbon particles that most likely not subducted due to their relative The final stages of basement building originate from the oldest known life buoyancy. Over time, the amount occurred from 1.8 to 1.725bya, when on the planet. To put into perspective of continental crust increased and Greenland was part of another super just how old these rocks are, try to when pieces of continental crust continent referred to as Columbia. imagine that the planet is only one collided, they welded together to These youngest basement rocks are year old. It would have formed on 1 form one block, and the immense seen in South Greenland. January, with the earliest known life forces involved thrust up chains of In East Greenland, basement rocks and these Greenlandic rocks forming mountains. During this process, are exposed, but, in most places, are in March. Multicellular life did not the rocks buckle and fold, with the covered by younger rocks. The oldest evolve until October, the dinosaurs intense heat and pressure causing exposed rocks in East Greenland are a few days before Christmas (going them to transform into metamorphic about 3byrs old and occur in the inner extinct on Boxing Day) and humans rocks such as gneisses. most regions of the Scorsby Sund, only appeared 15 minutes ago, with A large proportion of the rock exposed which is the largest fjord complex all of civilisation being in the last 10 in Greenland, particularly in the west in the world. Fig. 2 shows gneiss of seconds. and south, is made of these strongly this age from Hare Fjord, which is At the time these rocks formed, our folded gneissic rocks, which are the particularly rich in garnets (the large planet was a very different place and eroded roots of different mountain visible red minerals). There is then a the continents were still forming, belts, now welded together to form a time gap to the next oldest rocks in and there was less continental stable, coherent block. This block is East Greenland. These rocks are also crust than there is now. However, commonly known as ‘the basement’. basement gneisses and are 2byrs old. plate tectonics were taking place. The coming together of the basement They outcrop in Liverpool Land and Broadly, when one oceanic plate occurred over a huge period of time, the innermost reaches of Kong Oscar collides with another, one is forced spanning 3.8 to 1.75byrs. It was also Fjord (Fig. 3). Liverpool Land was to slide under the other in a process not a simple process. For example, named by the British whaler, William called ‘subduction’. Minerals in the by 2.7bya, most of West, East and Scoresby, who also lends his name to subducting slab dehydrate, causing South Greenland had formed and the Scoresby Sund fjord complex and the overlying mantle to melt and were probably part of a theorised Scoresbysund, the alternative name new rock types, like granites, to ancient continent referred to as for the settlement of Ittoqqortoormiit. be produced. The early granites of Kenorland. Two billion years ago, This town is one of the remotest East Greenland (and all subsequent this split up and parts of West settlements in Greenland and, in 7. 2010, had a population of just 469. sedimentary rocks. The red bands It was founded in 1925 by the Danish are very rich in garnets and are Government, which was keen to what geologists call a paragneiss. assert sovereignty over northeast The white bands occur where the Greenland. However, the area had metamorphism has gone one stage been the site of Inuit habitation in further, and the rock completely the past, as archaeological remains melted to form a granite. In this show. case the granite is an uncommon Overlying the ancient basement type called Augen granite, which is rocks of East Greenland are younger characterized by having very course sedimentary rocks. However many crystals. Dating of these granites of these rocks are themselves still show they formed 900mya (Leslie incredibly old. The oldest are named and Nutman, 2000). This would have the Krummedal supra crustal been due to yet further continental sequence, after a site in Scorbesby collisions that gave rise to yet another Sund, where it was first recognised super continent named Rodinia, Fig 2. 3byr-old basement gneiss, rich in that they are a separate unit. These which existed from 1.1bya to 750mya. garnets. rocks were lain down over a relatively The complexity of Øfjord does not end short period of time, just 50myrs, and here. There are also younger, igneous are 1byrs old. They were deposited rocks aged from 430 to 400myrs, and transported a considerable which were intruded into older rocks distance in a deep ocean environment during the Caledonian mountain after the breakup of Columbia. building phase. Fig. 8 shows a red Radiometric studies show that the dotted line that has been drawn on to sediments derive from two separate the photograph. This line highlights sources, with one probably being in one of these younger intrusions, what is now North America, with which is made up of darker rock than the other being Europe (Henriksen, the surrounding rock. This intrusion 2008). Today these rocks are only and has been identified by Leslie and found outcropping in the inner Nutman (2000) as a type of rock most sections of the fjord complex, called a hypersthene monzonite. Fig. except for one small outcrop on the 7 shows a line of darker rock rising northern tip of Liverpool Land. The from the bottom left hand corner sequence, which is up to 8.5 km thick of the photograph. This is the same in places, forms a great thrust sheet hypersthene monzonite, which cuts that has travelled westwards over through the older metamorphic rock, the basement rocks. In places, the and the top peak of the mountain is sediments are only lightly deformed, also made up of younger Caledonian but in other places they have been rock, which is a pink granite. Fig 3. 2byr-old basement gneiss in changed into schists which are types With the super continent of Rodinia Ittoqqortoormiit. of metamorphic rock. Figure 4 shows established, sedimentation began an erratic made up of Krummedal on Greenland’s eastern margin. The rock. This rock is a schist that scale of this sedimentation was vast. contains the minerals garnet, kynaite A staggering 18.5km thick succession and mica. Fig. 5 (a photograph taken of sediments was continuously laid in Hare Fjord) shows Krummedal down from 900 to 450mya. The sediments in the distant cliff, which oldest 14km of this sequence - the are beneath basement rocks that Eleonore Bay group - are the most have been trust over them. photogenic rocks in East Greenland Øfjord Fjord (Figs. 6 to 10) is and could well be in contention to be spectacular in its dimensions. It is the most photogenic rocks anywhere 4 to 6km wide, but doesn’t feel that in the world. The Eleonore Bay big due to the enormous height of sediments were lain down in shallow the valley walls. Grundtvigskirche water, shelf conditions from 900 to (Fig. 6), at 1,977m, towers above the 600mya. Figs. 11 and 12 show these giant iceberg below. The rocks of sediments forming a spectacular the fjord are so sheer because they stripy cliff in Segelsällskarpet are incredibly hard and have been Fjord, which is 1,900m high. The resistant to the glacial erosion that multicoloured sediments include fine calved out the main valley of the fjord. grained quartzites, mud rocks, and They are also very complex. The red different limestones and dolomites. and white rocks shown in Figs. 9 and Figs. 11 to 18 show various views Fig 4. Metamorphosed Krummedal rock; a 10 are heavily metamorphosed rocks of the Eleonore Bay sediments in schist that contains the minerals garnet, kyanite and mica. that were originally Krummedal Segelsällskarpet Fjord, while Figs. 19 8. Fig 6. Geotourists enjoy the scenery of Øfjord. Fig 5. Basement metamorphic rocks thrust over Krummedal Rocks in Hare Fjord. Fig 7. The 1,977m-high peak of Grundvigskirche in Øfjord.