At http://cosmictusk.com/plants-and-trees-in-hiawatha-crater/ … we learn that the Hiawatha Crater recently found in NW Greenland, has organic carbon in the glacio fluvial sand seeping from the crater. It originates from the bedrock – gneiss. Some of the sand contains impact grains such as shocked quartz, impure mineral glasses and micro breccias. There are grains (in the breccia) that contain organic carbons (and can be read in full at the above link). The article was read at the 50th Lunar and Planetary science conference in 2019. Larger pieces of charcoal contain irregular shrinkage cracks that taper out in all directions – confirming they are derived from thermal alteration of wood. In this instance, trees. Trees in Greenland. Many of the pieces are described as coalified wood fragments. Alternative layers of spring and summer wood and well preserved bark also occur – from conifers.
The inference is that the impact object created coalification. In other words, extreme heat was involved in the making of coal beds – or am I jumping to conclusions. The wood, however is dated 2.0 to 2.5 million years ago (and yes such trees did exist in northern Greenland at that time). The intriguing point made in the article is that doesn't necessarily mean the impact took place that long ago as tree trunks could have existed through subsequent glaciation, possibly embedded in sedimentary deposits (in this case sand). This fact appears to expand the range of dates of the impact event – from 2.5 million years ago to 50,000 years ago. The crater is described as barely eroded and very young – which means it could well be even more recent than 50,000 years ago,