New insight into old woods from Iceland

The absence of a description of fossil woods in the past was caused primarily by the absence of a unified terminology and descriptions of their internal structure. In modern times, solutions were brought by the lists of microscopic structures published by the International Association of Wood Anatomists (IAWA). These unified the commonly used terminology.

Simplified map of Iceland. Points on the map indicate all places where new (white) as well as old (grey) finds of fossil wood originate from.

Geology of Iceland – young and interesting

It was no doubt a surprise to many that during the Tertiary period, the environment of the then territories of Iceland and the Czech Republic looked quite similar. At the time, the young northern part of the Atlantic Ocean had not yet fully opened. In present-day Iceland, the so-called hot spot, a place with an increased accumulation of magma from the depths of the earth’s mantle, began to manifest itself more prominently. Initially, during its reduced surface manifestations, it caused and supported the formation and persistence of the land bridge between Scotland and Greenland. This created a corridor through which terrestrial organisms could migrate in both directions between the continents. It was only later, in the Miocene period, that Iceland as we know it today was created as a result of surface outpourings.

The parallel between the Czech Massif and Iceland lies, inter alia, in volcanism and the resulting landscape full of lakes and forests. The similarities between the two areas were mainly caused by the climatic conditions within the Miocene climatic optimum and a similar landscape mosaic and ecosystems. The Ohře Rift, which gave rise to the mountain range in northwestern Bohemia, is a smaller counterpart of the gigantic Mid-Atlantic Ridge on which Iceland lies. However, this rift did not lie on any hot spot. The fault was merely reactivated as a by-product of Alpine orogeny.

Due to less volcanic activity in the area at that time, conditions were more suitable for forming continental basins with coal-bearing horizons in the territory of the Czech Republic. To a lesser extent, coal was also formed in Iceland. Owing to this parallel, researchers from the recently founded Institute Julius von Payer for Arctic and Subarctic Research have examined the possible connections in more detail.

Fossil gems from coal

A team of geologists from Jan Evangelista Purkyně University and Charles University have created the first comprehensive work describing fossil wood finds from the coal-bearing strata of Iceland. For the first time, a modern methodological approach has been employed to describe the internal structures of these woods.

For instance, fossil wood Taxodioxylon aff. cryptomerioides Schönfeld from the North Atlantic island region (aff. = affinis; having affinity) was described. This fossil is the first ever preserved evidence of conifers from the group Cupressaceae s. l. from Iceland (English: cypresses; s. l. = sensu lato – in the broad sense of the word in Latin). The taxonomic group of conifers Cupressaceae s. l. consists of true cypresses and their closest relatives, Taxus and swamp cypress. Taxodioxylon cryptomerioides is usually associated with the foliage of Cryptomeria anglica Boulter, which is from the area identified in earlier research. Together, they may represent a single botanical species. However, this is only a scientific assumption and has not been supported by finding both fossils in direct association.

Taxodioxylon aff. cryptomerioides– wood detail (pitting, tracheids, etc.); scale 50 microns.

Representatives of the Pinaceae (pine-like) group of trees are also typical, with their anatomical structure close to that of today’s American larch (Larix laricina). These findings and other fossil remains of trees confirm that larches were a common element in Cretaceous and Tertiary arctic swamp forests dominated by Cupressaceae s. l.

Iceland is a jewel among the islands of the Atlantic Ocean, and not just because of its fantastic nature. It also provides ample opportunities for researchers wishing to advance the exploration and knowledge of fossil woods from the Tertiary coal-bearing strata.

Richard Pokorný, Vít Koutecký, and Marcel Štofik. “Fossil wood of Iceland: An overview and new finds in Miocene coal-bearing formations”, Review of Palaeobotany and Palynology 306, (2022): 104724. doi: 10.1016/j.revpalbo.2022.104724

Jan Geist