Allison Guyot

Allison Guyot: A Hidden Gem Beneath the Waves

Imagine a hidden treasure lying deep beneath the vast expanse of the Pacific Ocean—a tablemount named Allison Guyot that has been shaped by millions of years of geological history and natural processes. Have you ever wondered what secrets lie in these submerged mountains?

The Formation of Allison Guyot

Allison Guyot is a trapezoidal flat mountain, rising 1,500 meters above the seafloor, with a summit platform that measures 35 by 70 kilometers. Could you imagine how vast and expansive this area must be? The formation of Allison Guyot can be traced back to hotspots moving through plate tectonics, creating chains of volcanoes that became progressively older away from the currently active volcano.

Ancient Volcanic Activity

The volcanic activity that formed Allison Guyot occurred around 111-85 million years ago. Can you fathom how long ago this happened? This period saw the emergence of a volcanic island, which eventually subsided and transformed into an atoll-like structure. The platform on top of Allison Guyot was once home to crocodilians during a previous era, but it emerged above sea level in the Albian and Turonian ages before drowning around 99 ± 2 million years ago for unknown reasons.

Exploring Allison Guyot

In 1992, the Ocean Drilling Program drilled into the summit platform of Allison Guyot through core sample 865A. This exploration revealed a wealth of information about its composition and history. The seamount is part of Site 865 in the Ocean Drilling Program, providing scientists with valuable insights into its geological makeup.

The Composition and Layers

Allison Guyot’s composition includes limestone, pelagic sediments, and basalts. Imagine the layers of history preserved within these rocks! The component minerals have been altered to calcite, clays, gypsum, hematite, quartz, and other unidentified minerals due to exposure above sea level or hydrothermal fluids. Clays consist of various minerals such as berthierine, chlorite, feldspar, hydromica, illite, kaolinite, mica, serpentine, smectite, and possibly zeolite.

The Emergence and Submergence

During the Albian period, Allison Guyot began as a volcanic island with a relief of perhaps 1.3 kilometers. Can you picture this towering structure above the waves? As it rapidly subsided, a limestone platform grew on top, eventually becoming an atoll-like structure. The emergence and subsequent submergence of the platform may have terminated carbonate deposition, preventing it from beginning again.

The Fossil Record

Fossils found in Allison Guyot’s deposits include bivalves like rudists, corals, echinoderms, foraminifera, green algae, hydrozoans, red algae, and sponges. These fossils tell a story of the ancient marine life that once thrived here. Teeth of crocodilians have also been found on the seamount, making it one of the oldest known crocodilian habitats in the Pacific Ocean.

The Drowning of Allison Guyot

Allison Guyot’s carbonate platform ‘drowned’ when sedimentation could no longer keep up with relative rises in sea level. Can you imagine how this process unfolded over millions of years? The emergence and subsequent submergence may have terminated carbonate deposition, preventing it from beginning again.

The Legacy of Allison Guyot

Allison Guyot’s legacy lies not only in its geological history but also in the insights it provides into the dynamics of plate tectonics, volcanic activity, and the evolution of marine ecosystems. It serves as a reminder of the dynamic nature of our planet and the mysteries that lie beneath the ocean’s surface.

As we continue to explore and understand the wonders of our oceans, Allison Guyot stands as a testament to the enduring power of nature. Its story is one of transformation, resilience, and the intricate dance between land, sea, and time.