THE SIGNIFICANCE OF COLOR BANDING IN 

 THE UPPER LAYERS OF KARA SEA SEDIMENTS 



Ralph R. Turner' 



Introduction 



Purpose 



Geological investigations of much of the 

 Kara Sea have been limited by inaccessibility 

 to all but icebreakers and by diplomatic consid- 

 erations because of its strategic position north 

 of Western Siberia. In spite of these limita- 

 tions, two reconnaissance surveys have been 

 conducted by United States icebreakers 

 (USCGC Northwind. 1965; USCGC Edisto and 

 USCGC Eashvind, 1967). In compliance with 

 the Continental Shelf Treaty of 1961 (signed 

 by the United States in 1964), bottom sam- 

 pling during these surveys was limited to 

 water depths in excess of 200 meters. The pres- 

 ent study was undertaken to evaluate the tex- 

 tural, mineralogical, and geochemical signifi- 

 cance of remarkably similar color sequences 

 displayed in the upper layers of sediment cores 

 collected. 



Location and Physical Characteristics 



The Kara Sea is located on the Arctic Eur- 

 asian Continental Shelf between Zemlya 

 Frantsa losifa and Severnaya Zemlya archipel- 

 agos and extends southward along the east 

 coast of Novaya Zemlya to the Eurasian coast 

 (fig. 1). It is the westernmost of the series of 

 Arctic epicontinental marginal seas lying 

 along the northern shores of Siberia. 



The area of the Kara Sea is 883,000 km.= of 

 which only 190,000 km.- exceeds 200 meters in 

 water depth. This deeper water is restricted to 

 two north-facing reentrants, or troughs, in the 

 northern part of the sea and to a 740-km. ar- 

 cuate trough parallel to and convex towards 

 Novaya Zemlya. The greatest depth (approxi- 

 mately 600 m.) occurs in the western reen- 

 trant, Svyataya Anna Trough, at the northern 

 extremity. The other two troughs, Voronin and 



Novaya Zemlya, have depths up to 430 m. 

 (Northivind sounding). A glacial erosion ori- 

 gin has been suggested for all three troughs on 

 the basis of their geomorphology and geo- 

 graphic location (Johnson and Milligan, 1967). 



A striking physical feature of the Kara Sea 

 is a well-developed deltaic system which ex- 

 tends some 300 km. seaward of the river 

 mouths in the southern part of the sea (John- 

 son and Milligan, 1967) Delta development in 

 this region is not surprising considering the 

 large annual discharge of suspended matter 

 (30 x 10^ tons, Kulikov, 1961) from the Ob 

 and Yenisey Rivers which debouch into the 

 Kara Sea from the south. The Central Kara 

 Plateau which extends northward between the 

 Svyataya Anna and Vorinin Troughs is not 

 part of the deltaic system but is overlapped by 

 it at 79° N. (Johnson and Milliean, 1967). The 

 two small islands, Vize and Ushakova, are on 

 this plateau. 



In spite of the summer stratification, the 

 depths of the deeper troughs remain well ven- 

 tilated. Data from Garcia (1969) showed 

 values for dissolved oxygen during the summer 

 no lower than 6.15 ml. liter for the deepest 

 water samples from the East Novaya Zemlya 

 Trough. 



Water which originates in the Atlantic 

 Ocean, called Atlantic water, (T>0° C. 

 S>34 °/„o) also enters the Kara Sea via sev- 

 eral pathways. Off the northern tip of Novaya 

 Zemlya, Atlantic Water which has transited 

 the Barents Sea continues westward into the 

 Kara Sea where it largely mixes with both the 

 continental runoff and Arctic water (T<-1.5° 

 C, S = 33.5 to 34.5''/„o; Milligan, 1969K 

 Atlantic water, considerably midified by transit 

 along the continental slope north of Spitsbergen 

 and Zemlya Frantsa losifa, also enters the 



