[MUSIC] Well, after seeing in the previous chapter, the corresponding section to terrigenous segmentation and littoral processes. Today we'll see the section that corresponds to what we call holomarine sediments. That is, those that occur in the sea, from primary education to sedimentation. Within this section we will see the two types of sediments holomarines, biogenics and hydrogen. And, from here, we will talk about what productivity is marine and the preservation of organic matter in the sediment. To conclude what we saw in other chapters about the carbon cycle. And finally, to conclude the chapter, some aspects of deposit resources of interest. We started with the holomarine sediments, which, as I said, are those that form you from the terrigenous contributions of nutrients, elements in solution, etc. are formed directly in fully marine conditions. A very spectacular example here of the formation of calcareous oolites in areas of tropical platforms, in this case, corresponds to the Bahamas, in which this precipitation is exclusively mineral. It forms some spectacular, like this satellite image we can appreciate, very transparent waters saturated. They help or facilitate the precipitation of aragonitic carbonate. Giving from the same marine dynamics, as these aspects of impressive structures. We will see then, within the elements of first category, which we call biogenic sediments. That is to say, those that are formed from the organisms, both the skeletal parts mainly, as the soft tissues of which we will speak later as organic matter. These form either individual organisms, or colonizing organisms, like for example the reef platforms, as the example we see here. also satellite image of the Great Barrier of Australia, of spectacular dimensions. In which these organisms produce you lithic formations, rocky habitats with highly productive habitats. From a huge proliferation of species, etc. But that not only are the builders or bioconstructors. These organisms may also be at the individual, ventonic, etc., such as the typical background colonization of the Mäerl type. In those that dominate calcareous algae and other organisms, even also corals, etc., giving some aspects of organic proliferation very interesting. Evidently these communities give rise, in depth, mainly continental shelf, to a carbonate sedimentation that reaches 100%. that is to say, the whole sediment is practically of organic origin, organogenic. In addition to these colonizing organisms, we also have unicellular organisms. For example seedlings, etc., with a huge species diversity that in this image some of them, evidently seen under a microscope, which are planktonic. And that, at the end when they die, precipitate this carbonate can reach the bottom, as long as the conditions chemical properties of the water do not produce dissolution as we shall see later. Obviously, all these organisms also carry a part of matter organic, soft tissue. Obviously they follow a different course, unless they are, let's say recycled on its precipitation path to the bottom. This is a graph in which we can see the contribution of carbonate on the one hand, horizontally and precipitation in depth. Up to a few, at 3000 and a few meters deep this precipitated carbonate, may begin to be dissolved. And finally it reaches a depth at which it is totally dissolved. Practically in the background this carbonate does not appear any more, but rather what appears are dissolution product type materials, clays, called red clays, etc. That is, it produces a diversity of funds depending on both the depth as of the climatology, to which the production of surface carbonate is found. And this gives rise to the distinct large-scale distribution of carbonate or mainly silica as we have seen in previous organisms. These differences we saw you the day before, in this cartography of the different types of deep sedimentation. And in which we can, we differentiate already the different proportion participation of silica and carbonate elements in the seabed, in the great depths. We then pass, seeing the elements of organogenic origin organic to hydrogen-type formations. That is, those materials that are formed directly by chemical processes of precipitation, concentration, etc., and which are, so to speak, the most historically known. Among them are those that are produced by evaporation of sea water, concentration and fractional precipitation of different salts produced by this evaporation of the water. The most typical example, more typical, is the in salines for the production of common salt and other salts. Here is an example of the delta Salinas of the Ebro in which we see the different lagoons. Obviously limited and managed. To progressively concentrate the outflow of water and to obtain the interesting end product being sodium chloride, the common salt. Evidently, this evaporation produces different materials progressively depending on the concentration, what in geology we call the virtual evaporite series. That at historical level we can contemplate in a real example of what may or may not happen in the past. In watersheds that are isolated from the open ocean and that progressively precipitate different materials. What would this evaporite series be? For we would start with the formations of carbonates, gypsum, anhydrite, gem salt, potassium-magnesium salts, etc. This would be the virtual sequence that we find in the fossil record, for example of the Mediterranean, about 6 million years ago, during the period Messinian. He was isolated from the Atlantic Ocean and the concentration of waters, the salinity of the waters, increasing progressively, produced this type of virtual sequence in repeated cycles. This is an example of this type of sedimentation process. Besides the salts known and you exploited of old, can be found and exploited in some sites, for example, phosphates, marine phosphors of marine origin and also of continental origin. But basically, for example, here we have an example of phosphorite nodules, extracted of the northwest margin of the Iberian peninsula in Galicia. And that can be exploited as it happens, for example at continental level, in the areas of West Africa etc. Let's move to the deep hydrogen deposits, that is, so far we have talked about coastal or more or less than the continental margin. But we go to the deep ones in which the origin chemical composition of the material forming the concentrations. They originate directly in the of the oceanic ridges of the hot spots of volcanic islands, etc. And they give way, you're directly in the volcanic building itself. For example, in the fumaroles giving place to oysters or to chimneys that can get to have a proportion, a very important metal content. Apart from that, we also speak of ferromagnesic coils, for example, ligation cobalt or you in the abyssal zones, in deep abyssal plains. Especially in the Pacific and part of the Atlantic, but mainly the Pacific called polymetallic nodules. In which you currently have several programs worldwide Exploration and exploitation of this rich source of metals. In the attached map, we see the distribution of the three typologies of this type of deep hydrogen formations. We can see them among polymetallic sulphides in yellow, as we have already mentioned, ferromagnesic crusts and nodules, the so-called manganese nodules, which are also polymetallic. This type of sedimentary material, what must be emphasized is that its production, for example the case of nodules, as you saw in the previous chapter talking about sedimentation rates. They are formations that take millions of years to form. That is, we are in a medium in which sedimentation is minimal, and in which the precipitation of these metals occurs in a slow, very slow process. already seen, these minerals, basically, we see the phenomenon of production in the abyssal zones of the nodules, here exemplified in this image. Or the particular case of smokers, or the mineralizing chimneys in the dorsal, or an example, a section of a polymetallic crust. These examples, then, are those that can become a source of certain minerals.
