To the previous page of the Jurassic Reef Park?
The formation of reefs has many similarities with a real estate business. A "house-building approach" might illustrate why Jurassic reefs grew only at certain sites and why many reefs were quite different from each other. Not every plot of ground is suited for the construction of a reef building. The characteristics of the building site demand the strict adherence to building regulations and thus only allow the construction of certain types of reef buildings adapted to these properties. Very impressive and large-scale reef buildings can only be built up at very special sites and demand an enormous effort as well as the cooperation of many specialists. Every house owner knows that the construction of his house was very dependent on the availability of a suitable plot.
We present here some typical Jurassic building sites and their reef buildings. You will see that, in comparison with modern reefs, Jurassic reefs were more widespread but also more different from each other. This means that during the Jurassic Period more plots suitable for reef building were available than today. However, these plots were of fairly different quality.
A rarity: we found excerpts of the 150 million years old 'Northern Tethys Real Estate Advertiser'. Let's present some of these offers. The original exposés are, however, not preserved any more. This is why we compare these offers with modern real estate objects and then will show what are the actual relics of those Jurassic reef buildings.
We could compare it with this (Figs. 25, 26): A fantastic dream site directly at the beach. Enormous hotel beach resort with all the conveniences. Direct access to the open sea. Kids' pool, leisure facilities, biotope, diversified and eventful nightlife, repair installations, naturally biological-dynamic method of construction with solar energy and energy regeneration. Of course, only an international syndicate under the cooperation of many specialists could construct such an outstanding resort. And it took time! However, if you chose the right site and invested enough, the whole business will run almost by itself after some time.
During the Jurassic, highly diverse reefs (which are reefs composed of many different coral species) grew in such favorable sites. What is still preserved today from such reefs looks like this (Fig.27):
|Fig. 27 shows a Jurassic reef which is composed of many different coral species (and hence exhibits a high species richness or diversity). Coral colonies overgrow each other. Their outlines are highlighted with a pencil. Each number stands for a different species.
You do not have the necessary capital for such a gigantic building object? You anyway prefer to do it by yourself? Nevertheless, you would like to have a nice plot directly at the beach? Well, then take this offer (Fig. 28). The ground is somewhat unstable, sand shifts and storms endanger this site. So if you do not have the necessary capital for constructing a deep foundation and for high-quality building material, you can still compensate this by switching over to a simple, easy-to-repair one-story construction using cheap building material (Fig. 29). And who knows, if you have some luck with the storms and if you are a good home-mechanics, you might even be able to later enlarge and transform your fish-and-chips huts into a beach resort.
During the Jurassic, coral meadows and thickets composed of only one of very few species grew under such conditions. Mostly, growth was short-termed because storms or sudden deposition of mud and sand caused the death of these coral meadows. What's still left today from such coral meadows looks like this (Fig.30):
Fig. 30 shows a Jurassic coral meadow which was several times affected by storm events. Therefore most corals are fragmented. Only one bushy colony was preserved in life position.
Why to always struggle for these beach sites which either are awfully expensive or come along with problematic characteristics? How about a quiet, protected plot far away from the shoreline (Fig. 31)? Naturally it is more difficult here to make a decent living but if you are not too pretentious, you might want to open a small restaurant, hoping that some visitors might find you (Fig. 32). The lovely northern part of the Jurassic Tethys Sea (see Chap. VII) was particularly promising in this aspect.
During the Jurassic Period siliceous sponges dwelled in such sites far away from the beachline, in somewhat deeper waters than the corals did. They formed sponge meadows in settings where relatively few other organisms lived, mostly because there was often not enough food for them. Siliceous sponges were masters in living under very different, often fluctuating nutrient conditions. What is still left today from these deeper water reef meadows looks like this (Fig.33):
|Fig. 33 shows a siliceous sponge meadow with plate-shaped sponges growing close to each other (the inclined position is due to later displacement of the rocks)
Possibly, the small restaurant becomes well-known later on. If then the business runs all right, even more guests will come and you might be able to enlarge your place to a multistory building (Fig.34): :
|Fig. 34 shows a large siliceous sponge reef. Contrasting the sponge meadows from above, it developed a pronounced topography. This improved the nutrition situation because current will have to speed up and more food particles will pass by.
|Maybe you are an individualist, are not ready for compromises which would cramp your style (Fig. 35)? Here a small tower, there a cute verandah, over there a nice bay-window (Fig 36)? Naturally, not to bother anyone and not to be paralyzed by building regulations you will have to put up with some disadvantages. You can do whatever you wish if you build your home just next to a stinky garbage dump or in smog areas with little oxygen.
|Fig. 37 shows a small, conical crust reef which is completely composed of calcified microbial films. The largest reefs of this type grew up to 30 meters high.