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This Was Wood 140 Millions Years Ago !! EarthCache

Hidden : 12/02/2008
1 out of 5
1 out of 5

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Geocache Description:

This EarthCache takes you to a fossilised tree located in the Nazaré region which was later transformed into a "pelourinho" (a Pelourinho is a column of stone usually located in the centre of a town square where the criminals were shown and punished) by the local people in substitution of an earlier Manueline (in reference to King D. Manuel I of Portugal, 1469-1521) pelourinho.

                         Pelourinho Da Pederneira

Local setting

This pelourinho, locally known as the Pederneira pelourinho (Pelourinho-fóssil da Pederneira) is a portion of the trunk of a petrified Gymnosperm (which are a group of spermatophyte seed-bearing plants with ovules on the edge or blade of an open sporophyll, which are usually arranged in cone-like structures - ie. Pine trees) of Cretaceous age (145.5 – 65.5 M.a.) that was erected in place of the old Manueline pelourinho.
It presents an important taphonomic history and is one of the most important monuments in Nazaré. The name of this town of Pederneira may have had its origin from this conifer trunk that was found fossilized in the region. This petrified fossil may have been used by Neolithic man as menhir, integrating a number of regional alignments with magical-religious significance.

This old landmark was found by early settlers and the original location of the find, sacralised by the pagan symbol, has been preserved as a cemetery thereby maintaining its religious significance. Around 1514, when D. Manuel I granted new charter to the town of Pederneira , a Manueline style pelourinho was erected in the main square. The town preserved the municipal status until 1855, when due to a demographic decline in the face of recent developments in the cosmopolitan beach of Nazaré, it was anexed to the municipality of Alcobaça before the
establishment of the municipality of Nazaré in 1912. In 1886, the fossilized trunk was transported to the Bastião Fernandes Square from the old cemetery, replacing the old Manueline pelourinho that had been destroyed. Thus, from 1912 this has become the only known example in the world where a fossil was used directly as a symbol of local popular sovereignty. The fossilised tree trunk was classified in 1933 as Public Interest Property with historical and cultural significance by Law Decree No. 23122, DG231.

Petrification of wood: the process Petrified wood (from the Greek root "petro" meaning "rock" or "stone", literally "wood turned into stone") is a type of fossil: it consists of fossil wood where all the organic materials have been replaced with minerals (most often a silicate,such as quartz), while retaining the original structure of the wood.
The petrifaction process occurs underground, when wood
becomes buried under sediment and is initially preserved due to a lack of oxygen. After rapid burial, the tree reacts to percolating water. Mineral-rich water flowing through the sediment deposits minerals in the plant's cells and as the plant's lignin and cellulose decay away, a stone mould forms in its place. It has been estimated that it probably takes less than 100 years for wood to petrify. However, this process does not always produce fossilized wood.After burial two other things may happen:

1 - The log may disintegrate and not be fossilized;
2- The log may be reduced by compression to a coal or it may become petrified.

 Elements such as manganese, iron and copper in the water/mud during the petrification process give petrified wood a variety of colour ranges. Pure quartz crystals are colourless, but when contaminants are added to the process the crystals take on a yellow, red or other tint.

Following is a list of contaminating elements and related colour hues observed in fossilised wood:
* carbon - black
*cobalt - green/blue
* chromium - green/blue
* copper - green/blue
*Haematite – red/pink
* iron oxides, eg. goethite - red, brown, and yellow
* manganese - pink/orange
* manganese oxides - black/yellow
* Pure silica – White
* Pyrite - Black Petrified wood can preserve the original structure of the wood in all its detail, down to the microscopic level.

Structures such as tree rings and the various tissues are often observed features.
Petrified wood has a Mohs hardness of 7, the same as quartz.

The Cache
In order to log your found for this cache you must measure the longest diameter of the fossilised tree trunk and see which is the color of the fossilized tree and identify the contaminant.
I also be very happy if you can put a photo of you and the Gpsr with the tree trunk , this is not mandatory to reclaim the Found log.
. Send me the answers via my geocaching profile before logging the cache.
Thank you.

ATTENTION: the diameter is the line between two points of a circunference that it pass in the center in this case its a eclipse and i demand the longest Diameter.


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Thank you for your visit We hope that you like it .

A Special Thanks to Daniel Oliveira for all the Help.

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