STRAKHOV, NIKOLAI MIKHAILOVICH

(b. Bolkhov, Russia, 15 April 1900; d. Moscow, U.S.S.R., 13 July 1978)

lithology, sedimentology.

Strakhov’s father, Mikhail Vasilievich, taught at a primary school and was an accountant. His mother, Aleksandra Denisovna, a housewife, died in 1920 after a serious illness. The family then separated and settled in different cities.

Strakhov graduated with honors from the classical school in Bolkhov and in 1918 began to teach astronomy and geology at a secondary school. In 1923 he moved to Moscow and enrolled in the geological-geographical department of the Physical-Mathematical Faculty of Moscow University. He quickly distinguished himself by his talent for complex problems in geology. Soon he began to work under the guidance of Andrei Dmitrievich Arkhangelskii, studying recent Black Sea sediments. In 1928 he successfully defended his thesis on the geology and geochemistry of these sediments.

For the first seven years after graduation, Strakhov lectured on the geology of the Soviet Union and on historical geology at the Moscow Institute of Geological Survey and the Institute of Geological Survey of Oil Fields. During these years he wrote the textbook Zadachi i metody historivheskoy geologii (Problems and Methods of Historical Geology, 1932), which included, together with educational materials, theoretical conclusions on general geology. This book contained the first formulation of the main principles of Strakhov’s comparative litho-Iogical method. During the following years Strakhov developed these principles and established a number of laws of sedimentation.

In 1932 Strakhov and Arkhangelskii completed studies of the most recent Black Sea sediments. This work became the basis of their 1938 monograph in which they showed the distribution of three typical layers differing by age, lithological composition, and fossil remains. It was the first time that a scientific conclusion was reached about the direct dependence of composition and thickness of accumulated sediments on the relief of the drainage area.

In addition. Strakhov established that hydrogen sulfide contamination of relatively deep parts of the Black Sea favors preservation of organic matter on the sea floor.

The year 1937 was a turning point in Strakhov’s life as a geologist. A serious swelling of the hip that led to nerve pressure made it difficult for him to walk, thus limiting his ability to participate in field expeditions. But this misfortune did not affect the depth of his investigations; indeed, it favored his formation as a theorist.

Strakhov’s first theoretical work was an important generalization that enabled him to establish the distribution of iron ores of sedimentary origin. Strakhov found that from the Precambrian until the present there were six long and nine short epochs of intensive accumulation of sedimentary iron ores. Since he had discovered a general correlation between the peculiarities in the accumulations of iron, manganese, and aluminum, he concluded that these metals formed accumulations under similar conditions: a hot, humid climate. In addition, they were associated with the bases of transgressive deposits.

Strakhov also obtained significant results while studying the process of halogenesis. He established that the main paragenesis at the early stages of this process is later replaced by a dolomite paragenesis, and finally by a magnesite paragenesis. The significant conclusions of these investigations were presented by Strakhov in his doctoral dissertation in 1944.

In the following years Strakhov concentrated on determining general laws of sediment formation. He became convinced that the construction of lithological theory should be based on the study of recent sedimentation, on the comparative analysis of ancient sedimentary units, and on physicochemical experiments. He emphasized that only these three main areas of investigation, in combination with comparative lithology, can provide a means for the construction of a general theory of the sedimentary process.

Strakhov embarked on the complex problem of establishing laws governing lithogenesis by studying the peculiarities of recent sedimentation in continental seas and lake basins. He paid particular attention to the data obtained in studying bottom sediments of the Black Sea, the Aral Sea, and the Sea of Japan, as well as Lakes Baikal, Balkhash, and lssyk-Kul. These studies supplied hitherto unknown data and gave him the opportunity to compare the physicochemical peculiarities of recent sedimentation with sedimentary processes in the basins of the geological past. He was the first geologist to establish the decisive role of diagenesis as a mineral-forming process and to reveal the physicochemical nature of this phenomenon. He clearly proved that diagenetic transformation is a natural reaction of physicochemical imbalance and that the most important factor controlling this process under conditions of marine spillway is the burial of organic matter.

Strakhov also studied the peculiarities of carbonate accumulation. He assigned a significant role in this process in fresh water to life processes of animals, plants, and bacteria. With an increase in salinity, however, the role of living forms in carbonate accumulation sharply decreases; and in basins with high salinity purely physicochemical factors play a leading role. The pattern of the distribution of carbonates on the continents and in the oceans compiled by Strakhov showed that their distribution and mineral composition are clearly controlled by climatic and tectonic factors, with the leading role played by the former.

Strakhov’s next discovery, described in Osnovy teorii litogeneza 1960–1962; translated as Principles of Lithogenesis [1967–1970]), was quite unexpected. At that time the generally accepted opinion was that chemical reactions control the process of sedimentation. Strakhov convincingly showed, after years of research, that the behavior of chemical elements is governed by a complex physical-geographical interaction between drainage areas and sea basins. By this discovery he laid the foundation of a new science, the geochemistry of sedimentary rocks and ores.

Considering the peculiarities of sedimentation in recent basins and comparing them with the most ancient sedimentary deposits, Strakhov subdivided lithogenesis into four types: humid, arid, glacial, and volcanogenic-sedimentary. These types are typical not only for recent but also for all ancient deposits up to the uppermost parts of the Proterozoic. Maps of lithogenetic types have become a basis for locating ore deposits.

The study of rock composition within different lithofacial zones enabled Strakhov to determine their contents quantitatively and, among other things, to show that the endogenetic material in them does not exceed a quarter of all the sediments accumulated for the last 550–600 million years.

Strakhov further elaborated the principles determining the formation of sedimentary ores in different zones. By comparing the regularities in distribution of rocks as indicators of lithogenesis at different stratigraphic levels, he was able to show the peculiarities in the evolution of the earth’s external geospheres. This helped to reveal the directions of changes in the composition of the atmosphere, hydrosphere, and biosphere from the Archean up to the Quaternary. Analyzing the development of the biosphere, Strakhov also identified chronological boundaries in the evolution of organic matter. He elaborated in detail the effect of organisms on the processes of sedimentary rock formation.

Among other important theoretical principles proposed in this work is Strakhov’s teaching on the periodicity of sedimentary processes and its relationship to epochs of global marine transgressions and regressions. He showed that transgressions are accompanied by the formation of coarse clastic rocks as well as iron, manganese, phosphorites, and some others. Deposition of clays and of carbonate and siliceous rocks takes place in the epochs of stable development of the basin. On the other hand, the periods of regression are accompanied by the accumulation of halogen rocks, copper-bearing sandstones, and siderites.

In Strakhov’s theory the formation of sedimentary rock is a multistage process in which mineral accumulations in the basin area depend not only on the stage of sedimentation but also on the stage of diagenesis and catagenesis. Strakhov also emphasized that sedimentation is a complex process that involves solutions, colloids, mechanical suspensions, and biological remains. He further argued that periodicity of sedimentary rock formations is directly related to changes in the continental area, as well as to the composition of the atmosphere, hydrosphere, and biosphere.

While in Principles of Lithogenesis Strakhov dealt with the continental areas and the seas surrounding them, in the last years of his life he concentrated on studying ocean sediments. For this purpose he selected the most recent deposits accumulated on the floor of the Pacific Ocean and used the method of lithological facies profiles. He constructed one profile (more than 11,000 kilometers [6,875 miles] long) from the Sangar Strait via the Wake Island Atoll and the Hawaiian Islands to the Gulf of California. The data from forty-eight holes drilled approximately along the profile were available. Since each hole penetrated to a depth of seven to eight meters (about twenty-one to twenty-five feet), the data contained considerable new and interesting information. In particular they showed that for the last 100,000 years the effect of volcanism on sedimentation in the Pacific Ocean has been relatively inconsiderable. Strakhov’s studies also proved that the main geochemical process controlling sedimentation in oceans was a mechanical fractionation of both autochthonous and allochthonous suspensions. These conclusions became one of the main principles of the theory of oceanic lithogenesis.

At the same time Strakhov established that the four types of lithogenesis he had identified for continental areas were not found in the ocean. Oceanic sedimentation is a single type of lithogenesis encompassing separate sedimentary rocks of volcanic origin. Strakhov therefore concluded that the rocks and ores reflecting different ways of delivering material into the area of sedimentation occur on land, in swamps and lakes, in the coastal areas of continental and marginal seas, or on the continental margins of the oceans.

The greatest amount of sedimentary deposits directly indicating the climatic environment of sedimentation is concentrated either on continents or in a transitional zone between the continent and the ocean. Strakhov established that in the deep areas of continental seas (for instance, in the Caspian and Black seas), climatic control is almost absent. The nature of sedimentation in the ocean reflects a specific dependence both on the enormous mass of water and on the climate. His studies revealed that vertical movements of air masses, as well as the change in temperature along the meridian, do not practically affect the character of sedimentation. The decisive role is played by horizontal movements of the air, which create circulating currents and form areas of constant salinity in the surface layers of oceanic waters to depths of 200–250 meters (about 600-750 feet).

Strakhov concluded that the hydrodynamic regime created by climate in the world ocean controls the distribution of almost all components of sediments on the ocean floor, forming all their different lithological and geochemical types. The role of climatic zonation in the oceans is relatively slight; changes in the moisture and temperature regime are reflected only in the fact that there is a more intensive accumulation of magnesium calcite, and specific organisms-for example reef-building corals in the tropics and subtropics—participate in the formation of sediments.

The studies of sediments from different latitudes showed some differences between high-latitude and low-latitude modifications in the floral species content. Strakhov’s hydrodynamic concept of oceanic sedimentation further included a direct correlation with processes on the continents.

Strakhov published more than 200 scientific works, including fifteen monographs, some also published in English. French, and Japanese. He was a very gifted teacher, and many prominent Soviet geologists take pride in calling themselves his disciples. A large school of lithologists carrying on the development of his theoretical ideas and methods was formed. In 1946 the U.S.S.R. Academy of Sciences elected Strakhov a corresponding member, and in 1953 a full member. He retired in 1976 but continued his scientific activities until his death. His last scientific monograph was published posthumously.

BIBLIOGRAPHY

I. Original Works. Strakhov’s works are listed in Problemy litologii i geokhimii (see below), 17–26. “Poslednie stranitsi geologicheskoy istorii Chernogo moria,” in Priroda, 1930.no. 11–12, 1089–1108; “Geologischeskaia istoriia Chernogo moria,” in Biulleten’ Moskovskogo obshchestva ispytatelei prirody, otdel geofagicheskii, 10 , no. 1 (1932), 3–104, written with Andrei D. Arkhangelskii; “K voprosy o prichinakh i vremeni serovodorotsnogo zarazheniia Chernogo moria,” in Zemlevedenie, 34 , no. 1–2 (1932), 79–91; Zadachi i metody istoricheskoy geolgii (Moscow and Leningrad, 1932); Geologicheskoe stroenie i istoriia razvitiia Chernogo moria (Geological structure and history of the Black Sea; Moscow and Leningrad, 1938), written with A. D. Arkhangelskii; Zhelezorudnye fatsii i ikh analogi v istorii Zemli (Iron-bearing facies and analogues in the Earth’s history; Moscow, 1947); Osnovy istoricheskoi geologii, 3rd ed., 2 pts. (Moscow, 1948), trans, by J. Kolodny and E. Rosenthal as Principles of Historical Geology (Jerusalem, 1962); lzvestkovo-dolomi-tovye fatsii sovremennykh i drevnikh vodoemov (Limestone-dolomite fades in modern and ancient aqueous basins; Moscow, 1951); Obrazovanie osadkov v sovremennykh vodoemakh (Formation of sediments in recent water basins; Moscow, 1954): Osnovy teorii litogenez, 3 vols. (Moscow, 1960–1962), trans. by J, Paul Fitzsimmons as Principles of Lithogenesis, S. I. Tomkeieff and J. E. Hemingway, eds., 3 vols. (New York, 1967–1970); Tipy litogeneza i ikh evoliutsita v istorii Zemli (Types of lithogenesis and their evolution in the Earth’s history; Moscow, 1963); Geokhimiia osadochnogo margon-tsevorudnogo protessa (The geochemistry of sedimentation of manganese ores; Moscow, 1968); Razvitie litogeneticheskikh idei v Rossii i SSSR (The development of lithogenetic ideas in Russia and the USSR; Moscow, 1971); Problemy geokhimii sovremetwogo okeanskogo litageneza (Problems of geochemistry of recent oceanic lithogenesis; Moscow, 1976); Lzbrannye trudy: Obshchie problemy geologii, litologii i geokhimii (Selected works: General problems of geology, lithology, and geochemistry; Moscow, 1983).

Strakhov’s manuscripts are at the U.S.S.R. Academy of Science.

II. Secondary Literature. Problemy litologii i geokhimii osadochnykh parod i rud: Shornik statei k 75-letiiu akad. N. M. Strakhova (Problems of lithology and geochemistry of sedimentary rocks and ores: Collection of articles published on the occasion of the seventy-fifth birthday of Acad. N. M. Strakhov; Moscow, 1975).

See also “Akademik Nikolay Mikhailovich Strakhov (geolog. k 70-letiiu so dnia rozhdeniia,” in Litologiia i polezniye iskopaemiye, 1970, no. 1, 3–10, with portrait; V. N. Kholodov. “Vklad akademika N. M. Strakhova v razvitie geokhimii osadochnykh porod.” ibid., 1979, no. 4, 3–15: A. I. Osipova. “Strakhov, N. M. pedagog i organizator” ibid., 156–159; D. G. Sapozhnikov, “Voprosy osadochnogo rudoobrazovaniia v trudakh N. M. Strakhova,” ibid., 16–28; and V. I. Smirnov. P. P. Ti-mofeev, and V. N. Kholodov, “Nauchnaia deiatePnost akademika N. M. Strakhova,” in Problemy litologii i geokhimii osadwhnykh porod i rud (Problems of lithology and geochemistry of sedimentary rocks and ores; Moscow, 1975), 1–16.

V. V. Tikhomirov