188 POPULATIONS OF THE SEA 



representing a recurrent or time-transgressive paleoblogeographic 

 realm of major significance.* 



It is well known that aside from redeposited shelf assemblages, 

 occasional pelagic species, and the rare occurrence of unusual and 

 impoverished benthonic associations, the flysch biota is represented 

 almost exclusively by a relatively small variety of tracks and 

 feeding burrows of unusual regularity and distinctive form (e.g., 

 Seilacher, 1954, Fig. 2; Cloud, 1959b, Fig. 6). Two things besides 

 their regularity stand out about these Lehensspiiren or trace fossils. 

 First, they are pretty much the same all over the world and from 

 middle Paleozoic, or earlier, to late Cenozoic. Second, they 

 commonly cut across physical markings made by gravity emplaced 

 sediments that were moved rapidly across and dumped upon the 

 surface on which the organic markings were made later. 



We know, therefore, that the mobile benthonic fauna responsible 

 for the distinctive organic trackways and burrows of the flysch 

 facies lived largely within the sediments — that it was primarily an 

 injaiina. It is evident, too, although we have never knowingly 

 observed the makers of these particular markings, that the organ- 

 isms responsible for them maintained or adopted broadly similar 

 distinctive habits of feeding and movement, did not vary widely 

 in size, and had functionally similar locomotor, digging, and 

 feeding equipment through a remarkably wide range of space and 

 time, and despite the relative geographic isolation of many flysch 

 basins. If we assume that the animals as well as the tracks were 

 similar, we have in effect drawn a \ery close parallel between the 

 fauna of the flysch facies and the modern infauna of the cold 

 aphotic depths as described by Thorson (1957, pp. 463-466) and 

 indicated in Fig. 3. Even those species which worked at the 



* For purposes of this discussion I adopt an objective definition of flysch facies 

 which demands that the coarse layers possess four critical descriptive features 

 suggested to me by Prof. Ksiazkiewicz : (1) pronounced lateral continuity; (2) sharp 

 bottom contacts and commonly gradational tops; (3) generally well-defined internal 

 structure; (4) plentiful sole markings showing directional characteristics. It is only 

 fair to remark that Professor Ksiazkiewicz does not himself insist on so restrictive a 

 definition. 



For further discussion of the problem see also R. Trijmpy {Bull. Geol. Soc. Am., 

 71 (6), 873-880 (1960) or the comprehensive monograph of N. B. \'assoevich, 

 The Flysch and the Methods of Its Study (in Russian), Gostoptekhizdat, Leningrad, 

 1948. 



