Full resolution (JPEG) - On this page / på denna sida - Sidor ...
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
39
men det er neppe muligt at, bringe dens amorfe Partikler
i eu tilstækkelig fint fordelt Tilstand.
Det kunde synes naturligt at antage, at den Grad af
Finhed, hvori Lerets mineralske Blandingsdele befinder sig,
maatte staa i et lovmæssigt Forhold til Afstanden fra Land.
I det store taget er dette ogsaa ganske rigtigt, nemlig naar
der er Tale om længere Strækninger, eller hvis man altsaa
sammenligner Bundprøver, der er optagne fjernt fra
hinanden og paa forskjellige Dyb (f. Ex. paa Kystbankerne
og i det egentlige Havbasin), men indenfor det graa Lers
eget Omraade er den ovenanførte Regel neppe anvendelig.
Kystsedimenternes Foranderlighed og Ubestemthed i denne
Retning er tidligere paavist ved talrige Observationer, og
Buudprøverne fra den norske Expedition tjener til
Bekræftelse herpaa.
Jeg skal saaledes exempelvis nævne, at vi ved
Expeditionen sydligste Rute — fra Sognefjordens Munding til
Island — paa Stationerne 8 og 9, der ligger 4—5 Mile
fra Land, finder en .fin ensartet Prøve, der udelukkende
bestaar af amorft Ler, medens derimod Stationerne 14 og
18- — omkring 7 og 18 Mile længere ud i Havet — viser
et grovkornigt Ler, der ved Slemning gav et betydeligt
Residuum (30—40 pCt.) af grovere mineralske Partikler.
Det samme Forhold møder os ved Betragtningen af
Bundproverne fra Expeditionens nordligere Snit. Paa
Stationerne 110, 114, 116, 117, 118 og 123 (15—30 Mile fra
Land), har jeg saaledes ogsaa fundet fint- og grovkornigt
Ler i et vexlende Forhold, der ikke synes at rette sig efter
Afstanden fra Kysten. Denne Uregelmæssighed viser sig
i det Hele taget overalt paa Kystbankerne, hvor
Expeditionen har foretaget Dybdemaalinger fra Land og udover
mod Havet i planmæssig Rækkefølge.
Af de Dyr, hvis uorganiske Rester forekommer i
Kystleret, gives der naturligvis en Mangfoldighed af Arter,
ligesom de ogsaa optræder i vexlende Antal, men sjelden
udgjør de nogen væsentlig Del af Bundprøverne. Blandt
de almindeligste af de Foraminiferer, der er fundne i
Bundprøverne fra de norske Kystbanker, er Slægten
TJvige-rina1. Denne Foraminifer er sjeldnere i det graa Ler
langs Spidsbergens Kyst, der i det Hele taget synes at
være fattigere paa Dyrelevninger. Det kan nævnes, at jeg
her paa enkelte Stationer har fundet Discorbina i et stort
Antal.
Prøverne af graat Ler fra Færø-Islandsbanken viste
sig at være næsten fuldkommen frie for Dyrelevninger.
I Havet nordenfor Norge er det vanskelig at bestemme
Grændserne for det graa Lers Udbredelse, da det her
støder sammen med og lidt efter lidt gaar o.ver i det grønlige
Rhabdammina-Ler. Langs Nordkysten af Norge er der af
Expeditionen ikke foretaget nogen Dybdemaaling, men vi
1 Jeg maa oplyse om, at Hr. Prof. Sars har været af den
Godhed at bestemme disse i Leret forekommende Dyr, der isærdeleshed
har tiltrukket sig min Opmærksomhed.
be macerated by boiling in water; but how reduce the
amorphous matter to the requisite degree of fineness.
It seems reasonable to assume that the magnitude of
the mineral constituents of the clay should be mainly
determined by the distance from land. And, taken in a broad
sense, this is found to be the case, viz. with regard to
Extensive tracts of the bottom, or. when comparing samples
from widely distant localities and different depths (for
example, the coastal banks as contrasted with the true
ocean-basin); but within the limits of the grey clay formation the
rule will hardly apply. The variable and uncertain
character of shore-deposits in this respect, has previously been
shown by numerous observations, and the samples of the
bottom obtained on the Norwegian Expedition afford
additional proof.
Thus, for instance, on the most southerly route of
the Expedition — from the mouth of the Sognefjord to
Iceland — samples of a fine, homogeneous deposit,
consisting exclusively of amorphous clayey matter, came up at
Stations 8 and 9, distant respectively 4 and 5 geographical
miles from land, whereas at Stations 14 and 18, lying
about 7 and 18 geographical miles farther out, the bottom
was found to be covered with a coarsely granulated clay
that, on being thorougly washed, left a very considerablé
residue (30 or 40 per cent) of coarse mineral particles.
A similar contrast is met with on comparing together
the samples of the bottom from the northern section of the
tract explored. Thus, at Stations X 10, 114, 116, 117, 118,
and 123 (from 15 to 30 geographical miles from land). I
found finely and coarsely granulated clays occurring under
conditions which are in no wise determined, it would seem,
by the distance from the coast. This striking want of
uniformity proved generally characteristic of coastal deposit
wheresoever systematic series of soundings were taken from
the shore to the banks.
The inorganic animal remains that occur in the grey
coastal clay are referable to a great variety of species,
more or less numerously represented, but they rarely
constitute any considerable portion of the deposit. Among
the Foraminifera found in the samples of the bottom from
the Norwegian coastal banks, one of the genera of most
frequent occurrence is Uvigerina.1 This animal is
comparatively rare in the grey clay off the coast of Spitzbergen,
which indeed would appear to be less rich in animal
remains. Here, however, at a few Stations. I found the
deposit to contain great numbers of the shells of Discorbina.
The samples of grey clay from the Færoe-Iceland
bank exhibit scarce a trace of animal remains.
In the tract of ocean stretching north of Norway, it
is difficult to determine the exact limits for the distribution
of the grey clay, since it there borders on, and is gradually
merged into, the greenish-coloured Rhabdammina clay. Along
the north coast of Norway no soundings were taken, but
1 Professor G. O. Sars has had the kindness to determine such
of the animals occurring in the clay as particularly attracted my
attention.
<< prev. page << föreg. sida << >> nästa sida >> next page >>
