Logging Instructions

Elephant Seal hauled out by Walker Bay

The coordinates bring you to a stretch of beach at Walker Bay, along the southern edge of Byers Peninsula in the South Shetland Islands. This coastline exposes rocks from the sedimentary and volcaniclastic units of the Byers Group. As you explore the area around the GZ, you may encounter banded petrified wood with preserved grain and flat siltstone slabs that may contain leaf impressions

All specimens must remain in place under ASPA 126 regulations.

Please complete the following three tasks:

Task 1: Leaf Fossils

Search the area for a rock showing a leaf impression or preserved plant texture. Describe, the shape or outline, any visible veins or patterns and the type of rock it is preserved in (e.g., siltstone, fine sandstone)

If you cannot find a distinct impression, describe a rock that might contain plant material and explain why.

Task 2: Petrified Wood

Identify a piece of petrified or silicified wood. Without disturbing it, describe its colour and banding and any visible grain, rings, or fractures

Task 3: Proof of Visit Photo

Take a photo of yourself or something clearly showing your username, with the whalebones near the GZ visible somewhere in frame. Please avoid showing any fossils directly.

Email or message me the answers to the logging tasks, and attach the photo to your log. Each log must include a photo, even for team visits. Logs not meeting the requirements will be deleted.

Earthcache Description

Section 1: Location Description

Walker Bay is part of one of the largest ice-free coastal zones in the South Shetland Islands and forms the southern margin of Byers Peninsula, designated Antarctic Specially Protected Area No. 126. The modern setting appears stark, shaped by glacial retreat, frost action, and ocean waves, yet it preserves evidence of a much warmer Antarctic past.

Scattered along the terraces and among the beach cobbles are pieces of petrified wood, carbonised plant material, and leaf impressions preserved in ancient sediments. These belong to the Byers Group, a sequence of rocks laid down during the Late Cretaceous to early Paleogene (approximately 83–50 million years ago), when this part of Antarctica supported cool-temperate forests.

Section 2: Geological Setting

Sedimentary Environment

The Byers Group was deposited in rivers, floodplains, shallow lakes, and delta systems. The rocks you see at Walker Bay include fine siltstones and sandstones, volcanic ash layers (tuffs) and local conglomerates

These sediments record the influence of the ancient volcanic arc along the Antarctic Peninsula. Volcanic activity contributed both the ash that buried plant remains and the silica needed for their mineralisation.

Petrified Wood

Petrified wood in this area often displays preserved grain and growth rings, silica replacement of the original wood structure, carbonised zones from early burial and heating and fractures enhanced by freeze–thaw cycles

This fossilisation process begins with rapid burial, followed by the slow precipitation of silica minerals within the tissues, preserving fine anatomical detail.

Leaf Impressions

Leaf fossils appear in finely bedded siltstones, often retaining the outline and sometimes the veins of the original leaf. These formed in quiet-water settings — such as floodplain ponds or overbank deposits — where plant material could settle undisturbed and be covered by sediment.

Why Fossils Are Exposed Here

Byers Peninsula is unusual because it largely escaped deep glacial erosion during the last ice age. Its older sediments remain intact, and modern processes such as frost heave, seasonal meltwater flow, and coastal erosion continually expose new fossil-bearing rocks at the surface.

Section 3: Antarctica’s Warmer Past

The fossils at Walker Bay come from a time when Antarctica had cool-temperate forests, with conditions comparable to modern Tasmania or southern New Zealand. Research on fossil wood from the region suggests summer temperatures above freezing, mean annual temperatures of roughly 8–15°C and forests dominated by podocarps, araucarians, ferns, and early angiosperms

These environments reflect the global greenhouse climate of the Late Cretaceous and early Cenozoic, before Antarctica became isolated by modern Southern Ocean circulation.

References

• Crame, J. A., & Francis, J. E. (1993). The geology and palaeontology of Byers Peninsula, Livingston Island. British Antarctic Survey Bulletin 68.
• Torres Carbonell, P. J., González, R., & Medina, F. (2013). “Sedimentary environments and stratigraphy of the Byers Group.” Andean Geology, 40(2), 379–399.
• Smellie, J. L., Panter, K. S., & Geyer, A. (2021). Volcanism along the Antarctic Peninsula and South Shetland Islands. Geological Society, London, Memoirs 55.
• Francis, J. E. (1991). “Palaeoclimatic significance of Cretaceous–Tertiary fossil wood from high latitudes.” Palaeogeography, Palaeoclimatology, Palaeoecology, 86, 313–321.
• Francis, J. E., & Poole, I. (2002). “Cretaceous and early Cenozoic forests of Antarctica.”
• Cantrill, D. J., & Poole, I. (2012). The Vegetation of Antarctica Through Geological Time. Cambridge University Press.
• Dutra, T. L., & Batten, D. J. (2000). “Upper Cretaceous floras from King George and Livingston Islands.” Cretaceous Research, 21(2–3), 403–421.
• Antarctic Treaty Secretariat (2016). Management Plan for ASPA No. 126: Byers Peninsula.