Saturday, July 31, 2010

RUMINATIONS ON THE RELATIONSHIP OF ARCHITECTURE AND FOSSILS

Continuing with revelations uncovered during my visit to Mesa Verde, let’s reflect upon the relationship between fossils and architecture. At Dinosaur National Monument architecture has been placed in the service of fossils. The 1957 QVC was designed to enclose and protect the great wall of fossils of the Carnegie Quarry. Extensive walls of glass took advantage of ambient light to illuminate the bones. The V-shaped roof was intended to reflect the topography of hills and gullies in the area and at the quarry site specifically.

Architecture in the service of fossils. The natural order of things it seems to me. However, there are notable exceptions to this world view. In some areas of France farmers have long built walls using fossils of the giant rudist clams, one of the major reef building marine organisms from the time of the dinosaurs. Johnson (2002 fig. 2; http://www2.fiu.edu/~goldberg/coralreefs/Rudist%20Reefs.pdf ) contains a very nice photo of one of these amazing walls of fossils.

The Brazilian towns of Sao Carlos and Araraquara are extensively constructed of stone from quarries in the Lower Cretaceous Botucatu Formation. Literally thousands of fossil vertebrate footprints can be seen in the flagstone sidewalks, as well as walls of buildings, throughout these cities. As recounted by Leonardi et al. (1986), paleontologists have surveyed more than 200 miles of flagstone sidewalks in these towns and collected over 200 slabs of important fossil footprints from them.

Mesa Verde is another place where we can see expressed this most peculiar philosophy of fossils pressed into the service of architecture.



There are some 6000 cultural sites in Mesa Verde, although only about 10% of them are cliff dwellings. Here  we’ll concentrate on the cliff dwellings, where I spent most of my time. Sandstone blocks were gathered  by the Ancestral Pueblo peoples, shaped, and then usually mortared together to form a sturdy structure. Many of the complexes have long retaining walls along part or all of their front edges. On the top stones of these walls can be seen a pleasing diversity of paleontological curiosities, mostly in the form of invertebrate trace fossils. Here are a few examples.


BALCONY HOUSE

Nicely preserved section of an Ophiomorpha burrow. These tubular, pitted burrows were probably made by crustaceans. We will revisit a truly exceptional Mesa Verde Orphiomorpha deposit in a future post.


Also from Balcony House, a slab with abundant impressions of clam shells with ribbed ornamentation.


CLIFF PALACE

Narrow, curved, non-filled burrows in hypo-relief, crossing one another on bedding plane surfaces.


LONG HOUSE
 

Part of the rippled sandstone floor surface riddled with vertical burrows and with short segments of burrows running along bedding surfaces.

STEP HOUSE

This site is a veritable wonderland of Mesozoic marine trace fossils. Here is an Ophiomorpha burrow, about a meter in length, branching and cutting across bedding.


Two burrows in retaining wall. One is vertical, in hyporelief, about one-half inch in diameter. The other is an infilled non-meniscate burrow running diagnonally across bedding.


This is a very peculiar trace, or possibly multiple traces. In the center is a sinuous infilled burrow exposed in hyper-relief. This sinuous trace appears to be within a larger elongate burrow that may branch or be crossed by similar burrows. Maybe this is an oddly preserved Ophiomorpha.

SPRUCE TREE HOUSE

A sandstone block showing cross sections and natural external molds and infillings of various marine molluscs, mostly bivalves. The block is part of a retaining wall along the trail up from Spruce Tree House, near the bottom of the trail.

SUN POINT VIEW

Long, straight and gently curved, in-filled non-meniscate invertebrate burrows running along bedding planes. The burrows are exposed in hyper-relief on a sandstone block (red arrow) along the paved path leading to the viewpoint.

SEDIMENTARY STRUCTURES
In addition to fossils, sedimentary structures have also been pressed into service. Most notable of these are ripple marks that formed on the shallow Cretaceous ocean floors.


Here is a rippled slab used as the lentel of a doorway in a three story structure in Cliff Palace. It is situated such that the ripples are facing down in towards the doorway and facing whomever passes beneath it.


Sometimes these ancient rippled sea beds form large parts of the living floors and plazas of the dwellings. Here we can see ripples on the floor of the communal area of Long House. Similar extensive rippled surfaces can be seen on the floor of the southern part of Balcony House.

Photos: Dan Chure

Johnson, C. 2002. The rise and fall of rudist reefs. American Scientist 90(2):148-153 (freely available at http://www2.fiu.edu/~goldberg/coralreefs/Rudist%20Reefs.pdf)

Leonardi, G. and Sarjeant, W.A.S. 1986. Footprints representing a new Mesozoic vertebrate fauna from Brazil. Modern Geology 10: 73-84.

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