Structural Evolution of the Northernmost Andes, Colombia
GEOLOGICAL SURVEY PROFESSIONAL PAPER 846
Prepared in coopeTation ·with the lnstituto Nacional de Investigaciones Geologico-MineTas under the auspices of the Government of Colombia and the Agency for International Development) United States DepaTtment of State Structural Evolution of the Northernmost Andes, Colombia
By EARL M. IRVING
GEOLOGICAL SURVEY PROFESSIONAL PAPER 846
Prepared in cooperation ·with the lnstituto Nacional de Investigaciones Geologico-Min eras under the auspices of the Government of Colombia and the Agency for International Development) United States Department of State
An interpretation of the geologic history of a complex mountain system
UNITED STATES GOVERNlVIENT PRINTING OFFICE, vVASHINGTON 1975 UNITED STATES DEPARTMENT OF THE INTERIOR
ROGERS C. B. MORTON, Secretary
GEOLOGICAL SURVEY
V. E. McKelvey, Director
Library of Congress Cataloging in Publication Data Irving, Earl Montgomery, 1911- Structural evolution of the northernmost Andes, Columbia. (Geological Survey professional paper ; 846) Bibliography: p Includes index. Supt. of Docs. no.: I 19.16:846 1. Geology-Colombia. 2. Geosynclines----Colombia. I. Instituto Nacional de Investigaciones Geologico Mineras.. II. Title. III. Series: United States. Geological Survey. Professional paper ; 846. QE239.175 558.61 74-600149
For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402- Price $1.30 (paper cover) Stock Number 2401-02553 CONTENTS
Page Pasre Abstract ------1 Ma.gmatism ----___ ------22 Introduction ______--____ --____ ------1 Precambrian ------ 22 24 Principal geomorphic-~.tructural provinces of Late Ordovician ------ 24 2 Late Paleozoic ------ Colombia ------Triassic and Jurassic ------24 Precambrian rocks in relation to the Guayana 25 shield __ ·___ ------2 Cretaceous ------Tertiary ------25 Phanerozoic sedimentation and orogeny ------ 6 Age provinces of granitic intrusive rocks ------26 6 Lower Paleozoic rocks and. orogeny ------ Geologic structure ----~------ 26 Middle and upper Paleozoic rocks and orogeny __ 9 Folds in metamorphic terranes ------ 26 Devonian ------9 Folds in unmetamorphosed terranes ------ 27 Mississippian through Permi·an ------9 High-angle reverse faults ------ 27 Late Paleozoic orogeny ------11 Strike-slip faults ------ 29 Mesozoic rocks and orogeny ------12 Interior basins ------ 31 Triassic ------ 12 Coastal wedges ------ 32 Jurassic ------14 Isthmus of Panama ------32 Cretaceous ------ 15 Geologic cross sections ------ 33 Late Mesozoic orogeny ------17 Structural evolution ------ 33 Cenozoic rocks and orogeny ------18 Precambrian __ ------_ ------33 Paleocene ------ 18 Paleozoic ------ 33 Eocene ------18 Mesozoic -----~------34 Oligocene _ ------ 20 Cenozoic ___ ------36 Miocene and the Andean orogeny ------ 20 Conclusions ______---_ ------38 Pliocene and Pleistocene ------22 Selected references ______38 IIolocene ------22 Index ------43
ILLUSTRATIONS
Page PLATE 1. Tectonic and geologic map of northernmost Andes, Colombia ------In pocket 2. Geologic sections across northernmost Andes, Colombia ------In pocket FIGURE 1. Map showing principal structural provinces of Colombia ------3 2-9. Sketch map showing- 2. Major tectonic subdivisions of northern South America, distribution ·of Precambrian and Cam- brian-Ordovician rocks, and radiogenic ages ------4 3-5. Paleogeography, facies, location of outcrops, and radiogenic ages of: 3. Cambrian and Ordovician age and axis of Late Ordovician orogeny ------7 4. Middle and late Paleozoic age and axis of late Paleozoic orogeny ------10 5. Triassic and Jurassic age and axes of Upper Triassic to Lower Jurassic plutons --- 13 6. Paleogeography and facies of Cretaceous age, axis of Upper Cretaceous plutons, and radio- genic ages ------16 7. Facies, thickness, and direction of transport of Tertiary deposits before the Andean orogeny (Miocene), location of axes of Eocene and Oligocene-Miocene plutons, and radiogenic ages ------19 8. Tentative distribution of granitic intrusive rocks by age provinces ------23 9. Principal tectonic elements of northernmost Andes, Colombia ------28 10. Diagram showing progressive westward shifts of eugeosynclinal axes and resulting continental accretion, northernmost Andes, Colombia ______------35
III STRUCTURAL EVOLUTION OF THE NORTHERNMOST ANDES, COLOMBIA . . ',
By EARL M. IRVING
ABSTRACT contrary, accretion by an unknown amount is probable dur The primeval Guayana shield of northern South America ing the late Paleo~oic orogeny, and more than 100 miles was is older than the metamorphism of the eugeosynclinal added to the continental margin during the Late Cretaceous Imataca Complex of southeastern Venezuela which took place or:ogeny. In northernmos.t Colombia, east-trending Caribbean at least 3,000 m.y. ago. Metamorphism and two granitic structures intercept Andean structures· and are therefore magma cycles we~ded the shield area into a stable craton younger. Late Tertiary epe-irogenic uplift accompanied by between 2,250 and 1,850 m.y. (Guyanese). To the west and faulting produced much of the present relief. probably to the north the shield rocks are younger; in INTRODUCTION Colombia the oldest known rocks are about 1,350 m.y. old (Orinocan). This P.recambrian crust extends well into the The Cretaceous and Tertiary sedimentary basins Andean Cordillera and appears to have provided a platform of Colombia have be·en studied in detail for more for ensialic miogeosynclinal sedimentation during much of than half a century by geologists searching for Phanerozoic time. petroleum. However, the pre-Cretac-eous formations During the Paleozoic Era a pericon.tinental eugeosyncline developed along and around the western and northern mar have hardly received their deserved attention except gin of the platform. In late Paleozoic time, miogeosynclinal for the monumental work of Grosse (1926) in west sediments near the edge of the platform and sediments and ern Antioquia and reconnaiss·ance studies by Hu volcanic material in the adjoining eugeosyncline were re bach and Alvarado (1934), Hubach (1957a, b), gionally metamorphosed along an arcuate fold belt (late Paleozoic orogen) that included the areas of the present Cen Trumpy · (1943), Gansser (1954, 1955), Biirgl tral Cordillera, the central part of the Sierra Nevada de (1961), Radelli (1967), and Stibane (1967). Santa Marta, and the Guajira Peninsula; the uplift 'and In the decade of the 1960's, several intensive deformation at ·this time produced the central northeast studies of pre-Cretaceous formations were under trending arcuate crystalline spinal column of the present taken in connection with regional mapping pro Colombian Andes. During the Mesozoic Era a second eugeosyncline formed outside the late Paleozoic orogenic grams. Beginning in 1962, Princeton University arc; at the close of the Cretac·eous the eugeosynclinal students (MacDonald, 1964; Lockwood, 1965; Al deposits were strongly folded but only locally meta varez, 1967) undertook field studies for doctoral morphosed. This orogeny formed the Western Cordillera dissertations on the base·ment rocks of the Guaj ira and coeval fold belts (Late Cretaceous orogen) along the Peninsula in extre~me northeastern Colombia. Prof. northeastern Oaribbean coast of Colombia. The immense Antioquian batholith and several satellitic intrusions were Gerardo Botero Arango in 1963 published the results emplaced along the inner side of the Late Cretaceous orogenic of his ·studies of the western half of the. Antioquian arc. In the middle Eocene and again in the Oligocene-early batholith and its encasing rocks. In 1964, under a Miocene, small posttectonic granitic plutons were emplaced cooperative program financed by the Ministry of along the late Cretaceous orogenic axis. During ·the middle Tertiary Andean orogeny, the intracratonic Eastern Cor Mines and Petroleum of the Government of Colombia dillera rose along sharp marginal flexures, high-angle re and the Agency for International Development, U.S. verse faults that dip toward the cordillera, and locally along Department of State, the U.S. Geological Survey in wrench faults. collaboration with the Colombia Instituto N acional The present trident Ande!'ln Cordilleras of northernmost de Investigaciones Geol6gico-Mineras (formerly In Colombia therefore are distinctive geologically and came into being at different times. High positive Bouguer anomalies in ventario Minero Nacional) undertook systematic westernmost Colombia and abyssal to bathyal lower Ter investigations of s.eJ.ected areas in northern Colom tiary sedimentary rocks overlying mafic volcanic rocks in bia. More than 60 Colombian geologists participated easternmost Panama suggest that the Isthmus of Panama for various periods of time during the 6-year pro probably is of oceanic crus.tal origin and became connected to and associated with the Andes during the Andean orogeny. gram. Geologists of the U.S. Geological Survey who Little attrition is recognized along the western edge of were associated with the program were Charles M. the continent at the latitude of Colombia (0°-9° N.). To the Tschanz (in the Sierra Nevada de Santa Marta);
1 2 NORTHERNMOST ANDES, COLOMBIA
Richard Goldsmith, Dwight E. Ward, and Donald H. Where the southeast-trending Isthmus of Panama McLaughlin, Jr. (in the Eastern Cord.illera) ; and joins the South American Continent, its hills veer Tomas Feininger, Robert B. Hall, and Laurence V. southward to become the coastal Serrania Baudo, or Blade (in the Central Cordillera) . Pacific Coast Hills, and its central syncline continues This paper endeavors to synthesize the history and as the Atrato synclinorium (fig. 1). The Atrato syn origin of the northernmost Andes on the basis of the clinorium merges southward with the Pacific Coastal results of this work and much recent data gathered Basin of southwestern Colombia. The thick Tertiary by others in the region. The extensive use of my strata of the lengthy north-trending Atrato syncli Colombian and American colleagues' data is fully norium separate the basement rocks of the Isthmus and gratefully acknowledged, although I alone am and the Pacific Coast Hills from those of the Western responsible for the tectonic concepts herein outlined. Cordillera. Special appreciation is extended to Drs. Aurelio Of particular interest is the multiple bifurcation Lara A. (deceased), Dario Suescun G., and Andres and the general "fleur de lis" pattern of the trident Jimeno V., respective Directors of the Instituto Na Colombian Andes. cional de Investigaciones Geol6gico-Mineras (here inafter referred to as Ingeominas) and its predeces PRECAMBRIAN ROCKS IN RELATION TO sor agencies, who provided unqualified support for THE GUAYANA SHIELD the program. Richard Marvin .and his associates, U.S. The northern Andean orogen borders the Guayana Geological Survey, very kindly supplied many new shield on the west in Colombia and on the north in radiogenic age determinations, without which im Venezuela (fig. 2). The history of the shield is re portant tectonic events in the area could not have viewed briefly here to demonstrate how far the been dated satisfactorily. shield extends westward and northward into the cordilleran system and to establish the part that PRINCIPAL GEOMORPHIC-STRUCTURAL - these rocks have played in the geologic and struc PROVINCES OF COLOMBIA tural history of the Colombian Andes. The Republic of Colombia borders on th= Isthmus The oldest rocks of the Guayana shield appear to of Panama and occupies the "tum of the corner'' of ·be gneissose migmatites in the Haut Sinnamary dis the northwestern part of the South American Conti trict of French Guiana. Choubert (1964) reported nent. South of Colombia the basement rocks of the that four radiogenic age determinations on alluvial Andean Cordillera, along a belt some 5,000 miles zircon derived from these rocks range from 4,100 long, apparently constitute a single, though complex, to 3,770 m.y. These extreme ages appear to be orogen. In Colombia, the Andes mountains divide suspect. into three subcordilleras known as the East~rn, Cen At least one and possibly several narrow east tral, and Western Cordilleras (fig. 1) . The Central trending eugeosynclinal belts developed upon the Cordillera appears to be the northerly extension of primitive shield. The eugeosynclinal rock groups are the basement rocks underlying the. Cordillera Real referred to as the Ile de Cayenne in French Guiana of the Ecuadorian Andes. Approximately at the (Choubert, 1964), the Adampada-Fallawatra in equator the Eastern and Western Cordilleras branch Surinam (Holtrop, 1968), the Kanuku in Guyana off from this Central Cordillera. In northern Colom (Williams and others, 1967), and the Imataca Gneiss bia, the Western and Central Cordilleras are over Complex in Venezuela (Kalliokoski, 1965; Martin lapped and concealed by a Tertiary sedimentary Bellizzia, 1968). Metamorphism of the Imataca Com wedge that adjoins the Caribbean Basin. At lat 70° plex in eastern Venezuela is now well established at 30' N., the Eastern Cordillera bifurcates, and the more than 3,000 m.y. (Posadas and Kalliokoski, main branch of that range passes northeasterly into 1967; Hurl·ey, K·alliokoski, and others, 1968) ~ Wil Venezuela, where it is known as the Merida Andes; liams, Cannon, and McConnell and others (1967, p. a somewhat smaller prong, the Serrania de Perija, 42), regarded the younger Barama-Mazaruni assem extends northward until it terminates against the blage in Guyana, on the basis of radiogenic dating Oca fault (pl. 1). The triangular mountain block of by Snelling, to have a minimum age of 2,500 m.y. the Sierra Nevada de Santa Marta, 19,000 feet in The subjacent migmatites are rarely distinguishable altitude at its highest point, is set off to one side from from the highly metamorphosed eugeosynclinal rock the Serrania de Perij a and lies on the rim of the groups deposited upon them. The eugeosynclinal Caribbean Basin. rocks are commonly in the high amphibolite to gran- PRECAMBRIAN ROCKS IN RELATION TO THE GUAYANA SHIELD 3
75" 70"
CARIBBEAN SEA
CARIBBEAN RANGES
BARINAS BASIN
OCEAN
GUAYANA SHIELD
It It •+ ..•• BRAZIL • • It• AMAZONAS • ...... ·· • •~-- :.. .···. __ ...... • ...... • . •• PERU .•"' ...... + ......
lOOP"''_l.Jr'-~..-15f~..- ..I...... --l ...f __l00r-,_-T...&.... __3Cji0-L,~ ... -M-,L....J! Kl LOM ETRES
FIGURE !.-Principal stvuctural provinces of Colombia. ~
EXPLANATION 80° 70° 60° CARIBBEAN SEA ·C. , Cenozoic rocks ?------?-----?___..? Mz, Moorocks } 6 Cambrian-Ordovician ~ rocks W P,, Paleozoic rocks ~ n.. 100 I ,._ 1 r/r:Zj !( -7 /~~'-- .J.<~AR~p,~ z__)c.) I 7 ~· z p£d, dolerite sills ~ p£r, Rora;;;rmation~l ~
Probable and known ~ Precambrian rocks a: n.. 2250 my z Radiometric age 0 ~ 1-3 ~ tzj ~ PACIFIC I OCEAN z ~ 0 00 1-3 > z t:j tzj sn 0 0 G(J4y41\14 ::>Hit:.LD ~ t"'4 2 0 oo I t "--~_I 1: ,~ I ~ ~ ·'~~vw I:C 1-4> c. c. BRAZIL MESOZOIC-CENOZOIC PHANEROZOIC ENSIMATIC EUGEOSYNCLINAL ENSIALIC MIOGEOSYNCLI NAL Manaua FORELAND PLATFORM AND FOLD BELT AND FOLD BELT CENTRAL PRECAMBRIAN CRATON / /1!I I I '---,.j I
100 50 0 100 200 300 400 KILOMETRES I I I I I I I I I I I I 100 50 0 100 200 MILES
FIGURE 2.-Sketch map of northern South America showing major tectonic subdivisions, the distribution of Precambrian and Cambrian-Ordovician rocks, and radiogenic ages. PRECAMBRIAN ROCKS IN RELATION TO THE GUAYANA SHIELD 5 ulite facies of regional metamorphism. Their high Amazon River Valley, but descends very gently grade of metamorphism suggests steep geothermal northward beneath Cenozoic strata of the Barinas gradients and probably ·active flow of fluids from the Basin, sensu lato, of Venezuela, and westward be mantle into the crust, most especially during orogen neath similar strata of the Llanos Basin (fig. 1) in ies. The early eugeosynclinal belrts may have formed Colombia. Examination of structure-contour (Smith, as depositories upop. a relatively thin granitic crust, 1962) and geologic maps of Venezuela and Colombia in the manner suggested by Anhaeusser, Mason, Vil sugge·sts in fact that the Andean Cordilleras wrap joen, and Viljoen (1969) for the greenstone belts of around the Guayana shield on its north and west the South African shield. sides. These high-grade metamorphic rocks are overlain In northern Surinam, gneiss and biotitic granite unconformably by younger sedimentary and volcanic were emplaced in ~tJ.mandine-diopside-hornblende formations-for example, the Carichapo and Pastora metamorphic rocks, from which Holtrop ( 1968, p. Series of Venezuela-which are also metamorphosed 505) reported a whole-rock Rb/Sr age of 1,250 ± and are widely intruded by granitic batholiths and 40 m.y. In northern Guyana a disturbance locally plutons of the Akawaian episode (Snelling and Mc called the Nickerian episode produced mylonitization Connell, 1969), also kno-wn as the Guyanese or and caused resetting of K/Ar ratios in many rocks Transamazonas igneous cycle.· Radiometric ages on 1,300-1,100 m.y. ago (Williams and others, 1967). these plutons range from 2,250 to 1,850 m.y. (fig. 2). At several points along the periphery of the exposed At least two magmatic cycles can be distinguished shield in southern Venezuela, radiogenic ages of during this time span; in the Guayanas they are re about 1,300 m.y. have been measured on intrusive ferred to as "younger" and "older" granites (Chou- ! rocks that are referred to the Orinoco igneous cycle bert, 1964; Williams and others, 1967; Holtrop, (Martin-Bellizzia, 1968). 1968). Rocks of similar radiogenic ages are represented In southern Surinam and Guyana, and in south in Colombia by a suite of granitic rocks collected by eastern Venezuela, the above-mentioned metamor Manuel Carvajal from exposures along the Guaviare phic and intrusive rocks are beveled by a major un- River Oat 3°00' N., long 70°43' W.). Radiogenic 1 conformity and are overlain by the widespread, analyses of these rocks by Pinson, Hurley, Mencher, relatively flat lying Roraima Formation (fig. 2), and Fai~bairn (1962) gave ages of 1,205±60 m.y. which is composed of conglomerate, red orthoquartz (fig. 2). Banded granulitic quartz-feldspar and ite, and minor shale and jasper (Sellier de Civieux, mafic paragneiss collected by C. M. Tschanz (writ- 1956, p. 509). These sedimentary rocks are extensive ten commun., 1969) in the Sierra Nevada de Santa ly intruded by mafic sills, some of which are enor Marta gave radiometric ages of 1,300 ± 100 m.y. mous in size and in outcrop area, and are locally as MacDonald and Hurley · ( 1969) obtained Rb/Sr much as 1,200 feet thick. whole-rock ages between 1,400 and 1,300 m.y. on Snelling (1963) analyzed a hornblende-pyroxene four specimens of similar granulite collected by mixture from one of thes.e sills, the Kopinang Valley MacDonald from the northeastern Sierra Nevada dolerite, and obtained a K/Ar age of 1,665 ± 130 de Santa Marta. Very recently MacDonald (written m.y. On muscovite from a rriica hornfels taken 5 feet commun., 1972) collected specimens of granite near above the upper contact of the same dolerite sill, he Jojoncito, Guajira Peninsula, whose contained zir obtained an age of 1, 735 ± 70 m.y. These ages, con gave an age of 1,250 m.y. The granite is be averaging about 1,700 m.y., are now confirmed by lieved to be late Paleozoic in age. The great age indi many K/Ar analyses and by Rb/Sr whole-rock cated by the ·zircon suggests that the granite tra determinations. Of course the sedimentary rocks are verses, .and probably hatS assimilated, underlying older than the sills that cut them. The lack of later Precambrian rocks. orogenic and igneous activity in the region of the Roraima Formation clearly establishes that the cen Tomas Feininger (written commun., 1969) map tral part of the Guayana shield was converted into ped granulite west of the Middle Magdalena Basin a craton upon intrusion of the granites about 2,000 that is overlain by graptolite-bearing Ordovician m.y. ago and that it has been a stable cratonic mass strata, and Darfo Barrero L. reported (written com throughout subsequent geologic time. mun., 1970) similar granulites near Payande and The Guayana shield passes out to sea to the east, Rovira in the Department of Tolima (fig. 1) and in descends sharply southward beneath a Cambrian the Garzon massif in southern Colombia (fig. 2). Ordovician and younger sedimentary cover of the No radiogenic age determinations, however, have 6 NORTHERNMOST ANDES, COLOMBIA been made for these probable Precambrian rocks. presumably extend at least some additional distance These data establish that Precam.brian rocks do ex westward in the subsurface. tend well into the cordilleran region and generally To summarize, the oldest Precambrian rocks of have younger radiogenic ages than do rocks of the northern South America are in the east-central part central shield. These outer shield rocks may be older of the Guayana shield, and radiogenic ages decrease rocks whose radiogenic clocks have been reset by irregularly by large increments northward and more recent tectonic events. This interpretation in westward. Thus, the peripheral rocks of the shield, deed is indicated by retrograde metamorphism in even though of similar metamorphic rank to those many outer shield rocks. of the interior, appear to have been involved in In westernmost Sierra Nevada de Santa Marta younger tectonic events. The sequential relations (lat 10°40' N., long 74°08' W., fig. 1), hornblende might be interpreted as a growth pattern, but it is from a garnet-hornblende-pyroxene-feldspar granu more likely that the outer edges of the shield ex lite collected by C. M. Tschanz gave an apparent age perienced late Precambrian orogenies that reset the of 940 ± 32 m.y. (fig. 2). In the Eastern Cordillera, isotopic docks of older rocks. The outer edge of the hornblende from an amphibolite in the Bucaramanga shield, of course, is in the zone o.f interaction be Gneiss, collected by Richard Goldsmith west of the tween the continent and oceanic crust, where many Santa Marta-Bucaramanga fault (pl. 1; lat 8°17' adjustments can be expected to have taken place. N., long 73°25' W.), gav·e a K/Ar age of 945±36 The shield rocks, neve,rtheless, provided a com m.y. Both could be minimum ages. The approximate paratively stable platform for epicontinental and correspondence in age could be interpreted as fol miogeosynclinal sedimentation during Phanerozoic lows: (1) the Santa Marta granulite sample is an time. older deep-seated metamorphic rock whose radio genic clock has been reset and (2) the amphibolite, PHANEROZOIC SEDIMENTATION AND which is interbedded with paraschist and paragneiss OROGENY of the Bucaramanga Gneiss possibly repres·ents a LOWER PALEOZOIC ROCKS AND OROGEN\' younger Precambrian stratigraphic unit that never Fossiliferous Cambrian and Ordovician sedimen achieved the depth of burial nor as high a tempera tary rocks have been identified at several localities ture as that of the granulite facies. H. N. A. Priem in Colombia (Trumpy, 1943; Olsson, 1956; and and others (1966) reported K/Ar ages on biotite Biirgl, 1961). from the tin-bearing granites of Rondonia (north In the central part of the Serrania Macarena of west Brazil) to be 960 to 930 m.y. This clustering of south-central Colombia (figs. 1-3), trilobites, brachi the dates suggests that a regional disturbance may opods, and graptolites oollected by Otto Renz of the have involved the western edge of the continent at Shell Oil Company from a 500-foot section of thin this time. bedded· shale and minor limestone of the Giiej ar On the southeast side of the Sierra Nevada de Series, were identified by Marshall Kay (Harrington Santa Marta, Tschanz collected quartz-perthite and Kay, 1951) as ranging from Middle Cambrian gneiss samples from the Los Mangos Granulite to Early Ordovician in age. Enrique Hubach (in Series that yielded ages of 752±70 m.y. Goldsmith Hans Biirgl, unpub. data, 1967) collected fossils of collected a sample of paragneiss (lat 7°16' N., long similar age from the Giiej ar Series in the southern 72°54' W.) in the Santander massif (fig. 2) of the part of the Serrania Macarena (southeast of map Eastern Cordillera from which whole-rock Rb/Sr ped area). Trilobites and graptolites. collected by analysis gave an apparent age of 680 ± 140 m.y. Al Renz northeast of the town of Uribe in the Eastern though the negative deviation could throw the San Cordillera were identified by Kay (Harrington and tander sample into the Cambrian Period, regional Kay, 1951) as p.robably Cambrian (St. Croixian); considerations indicate a Precambrian age. these rocks appe·ar to be the westerly extension of The westernmost outcrops of Precambrian rocks the Giiej ar Series. Just west of the crest of the in Colombia are along the west side of the Sierra Eas•tern Cordillera along the trail on Cueva Creek, Nevada de Santa Marta, along the eastern side of a tributary to the Ambic:a River, soft micaceous the Central Cordillera, and in the Garzon massif of shale yielded graptolites of probable Ordovician age, the southern Eastern Cordillera. Because these west according to Kay (Harrington and Kay, 1951). ernmost Precambrian rocks are commonly bounded These rocks are overlain by about 3,200 feet of by major faults at the surface, rocks of this age barren quartzite. PHANEROZOIC SEDIMENTATION AND OROGENY 7
r------~s~o~·------~7~5~·------7~0~·------6,5"
CARIBBEAN SEA
10"
VENEZUELA
413! 30m.y,
PACIFIC 5" OCEAN
EXPLANATION BRAZIL Outcrop area of Cambrian and Ordovician rocks Epicontinental facies Miogeosynclinal facies Ensimatic oceanic facies Axis of Late Ordovician orogeny Stratigraphic test hole 450 ±aom.y. Radiometric age
5'------L------~ __l...a.'f1...,.....5..._f __ O.,_, ____l_. FIGURE 3.-Sketch map showing the paleogeography, facies, and location of outcrops of Cambrian and Ordovician age (from Biirgl, 1967), the axis of Late Ordovician orogeny, and radiogenic ages. 8 NORTHERNMOST 'ANDES, COLOMBIA Hans Biirgl (unpub. data, 1967) reported that The Silgara Schist (Ward, Goldsmith, Cruz, and cores of dark-gray shale from the N egritos No. 1 Restrepo, unpub. data, 1973) overlies the high well (fig. 3) in the eastern great plains area (Llanos amphibolite-grade Buooramanga Gneiss (Precani Basin, fig. 1) contain graptolites of probable Ordo- brian) in the Santander and Norte de Santander vician age. Similar rocks cored in the La Heliera No. Departments (fig. 1). The Silgara is composed of 1 well (160 km (100 miles) NNE; fig. 3) may also siliceous rocks of low to medium metamorphic grade be of Cambrian and Ordovician age. and appears to represent sediments deposited under At Cristalina (fig. 3) west of the Middle Magda- miogeosynclinal conditions. The Silgara Schist and lena Basin, Harrison (1930) discovered dark-gray the Bucarrunanga Gneiss are invaded by syntectonic shaly rocks containing graptolites of Early Ordo- granitic orthogneiss. All these rocks are overlain by vician age. Tomas Feininger (Feininger, Barrero, unintruded and unmetamorphosed fossiliferous De Castro, and Hall, 1973) found that the slightly meta- vonian s~trata. This evidence indicates, ·therefore, a morphosed shale overlies highly metamorphosed profound pre-Devonian orogenic disturbance in the granulitic paragneiss of probable Precambrian age. area. That graptolites are still pres·erved in the shale at A hornblende metadiorite collected by Goldsmith Cristalina appears to indicate a low temperature- from a roadcut (l.at 8°18' N., long 73°24' W.) be pressure regime for metamorphism. Feininger in- tween Rio de Oro and Puerto Nuevo yielded a K/Ar ferred that the Ordovician rocks and the underlying age on hornblende of 413 ± 30 m.y. (fig. 3; pl. 1). A Precambrian paragneiss were transported into the paragneiss of granitic composition on the road from area from the southeast by movement on the Otu BerHn to Pamplona (lat 7°15' N., long 72°48' W.) strike-slip fault (pl. 1). This interpretation proba- gave a whole-rock Rb/Sr age of 450± 80 m.y. (fig. bly explains the presence of fossils in an area. that. 3; pl. 1). Both metadiorite and paragneiss probably is otherwise characterized by m~dium- to high-rank formed during the s~ame orogenic disturbance. metamorphis.m. Metamorphic rocks that constitute Five samples of peralkalic syenitic rocks collected the bulk of the Central Cordillera are probably Paleo- in the low hills south of San Jose de Guaviare (about zoic in age (Nelson, 1957). 75 miles east of the Serrania Macarena, fig. 3) by In several areas, unfossiliferous, weakly meta- petroleum geologists yield K/Ar ages (biotite) morphosed beds are overlain unconformably by De- ranging from 485±25 m.y. to 445±22 m.y. (Pinson vonian rocks. Some of these pre-Devonian rocks may , and others, 1962). The mean age of the five samples be of Ca~brian and Ordovici,an age. The Quetame j is 460± 23 m.y. Series, nained originally by Hettner (1892), crops Stratigraphic and structural data clearly estab out prominently along the Bogota-Villavicencio lish the presence of an early Paleozoic miogeosyn road and extends as a belt along the east side of the clinal sea that extended through the general area of Eastern Cordillera at least from Gutierrez (Olsson, the present Eastern Cordillera and the Serrania de 1956) in the Department of Cundinarnarca to the Perij a (fig. 3). Although difficult to prove, an as Rio Bata gorge (fig. 3) in the Department of Bo- sociated eugeooyncline very likely existed west of yaca (BUrgi, 1960b). The Quetame Series consists the miogeosyncline because (1) ·the graptolitic .shale of highly folded green chloritic and gray sericitic at Cristalina indicates increasing depth of water as phyllite, interlayered quar.tzitic sands,tone and silt- compared with the original sand and sandy shale of stone, and some quartz conglomerate. According to the Silgara Schist; (2) the metasedimentary rocks D. H. McLaughlin, Jr. ·(McLaughlin and Arce H., of the Central Cordillera are more graphitic than the 1972), the series, although intens·ely folded, is little Silgara Schist anq (3) farther to the west, the meta metamorphosed as compared with all known Pre- morphic rocks of the Central Cordillera contain in cambrian rocks. Because of its. proximity to the creasing amounts of mafic volcanic material. Giiejar Series of the Serrania Macarena, the Que- Radiom·etric age data from metamorphic and ig tame is thought to be the equivalent of the Giiejar neous rocks establish that a ~strong orogeny took Series. place near the end of the Ordovician in the San- At the western base of the Serrania de Perija tander Department, and probably extended south near Villanueva (fig. 3), Forero S. (1967) m·apped ward. The fold axes and schistosity of this orogeny as Cambrian and Ordovician a thin ~sequence of trend north. Meager structural data indicate that little-metamorphosed clastic sedimentary rocks that fold axes within the Quetame and Macarena areas lie beneath fossiliferous Devonian beds. also trend north. The northeasterly trend of the PHANEROZOIC SEDIMENTATION AND OROGENY 9 present Quetame outcrop area (fig. 3) does not re a transgressive seaway that extended at least over flect internal structure and results from compara much of the area of the present Eastern Cordillera. tively recent Andean deformation. In Santander Department, recent geologic mapping Radelli (1967) and others referred to the Late by Ingeominas has established that the Floresta For Ordovician orogeny as Caledonian. Radiogenic age m.ation is increasingly metamorphosed northward data indicate that it corresponds closely to the Ta from the type locality. Because Permian and Triassic conic orogenic phase of the northeastern United beds in the same area are little or unmetamorphosed, States. the Devonian beds must have experienced a sharp, Absence of Silurian faunas from all of Colombia but probably local, disturbance in Late Devonian or probably indicates that much of the area was ele Carboniferous time. The north-trending foliation vated and undergoing erosion during the Silurian. and axes of folding of the Devonian metamorphic rocks generally coincide with those of the Cambrian MIDDLE AND UPPER PALEOZOIC ROCKS AND OROGENY Ordovician and Precambrian metamorphic rocks DEVONIAN beneath them. No igneous rocks associated with this Devonian rocks crop out in comparatively small Late Devonian or Carboniferous disturbance have windows along the Eastern Cordillera, from the yet been recognized. Serrania de Perij a in the north to J agua in the Gar Uplift resulting from this disturbance apparently z6n massif in the south (fig. 4). Fossiliferous red produced a regressive coarse clastic facies upon re dish-gray shale and gray sandstone are exposed treat of the seas from the region. Shoaling of the along the foothills of the Serrania de Perija east of sea floor is evinced by the conspicuous sandstone and Villanueva (Forero S., 1967). To the east in Vene orthoquartzite in upper parts of many of the De zuela, rocks probably of equivalent age are referred vonian sequences. to as the Cachiri Group (Liddle, 1946). The two lower formations of the Cachiri Group are fossilifer MISSISSIPPIAN THROUGH PERMIAN ous and are Early to Middle Devonian in age. The In Colombia, rocks of early Carboniferous (Mis Cachiri rocks consist of dark-gray to black shale sissippian) age seem to be generally absent, per containing many intercalations of gray siltstone and haps because of uplift produced by the Late Devoni quartzite. an disturbance. Hans Burgi (unpub. data; 1967) In Boyaca Dep·artment, the Floresta Formation stated that in latest Mississippian time a marine consists of a basal b~eccia overlain successively by transgression began with deposition of a basal con 1,900 feet of fine-grained black slaty fossiliferous glomerate and that the later deposits of this sea shale, and 150. feet of gray sandstone (Botero R., consisted of reddish sandstone, variegated shale and 1959). An extensive fauna collected by A. A. Olsson mudstone, and reddish marine limestone. from the lower part was studied by Castor ( 1939, In the Serrania de Perija, Forero S. (1967) and 1942), and another was studied by Royo y Gomez R.adelli (1967) reported thick sections of dark-gray (1942). The Floresta fauna appears to be similar to black phyllitic shale that contains fossils of late and is probably approximately equivalent to the Carboniferous (Pennsylvanian) age. The upper fauna of the Cachiri Group in Venezuela. limestone member of the Chandua Group (Gansser, Burgi (1960b) reported a thin sequence of De 1955) of the Sierra Nevada de Santa Marta (fig. 4) vonian beds at Rio Bata in the Quetame area. may represent a nearshore facies of these rocks. In the Garz6n area in the Department of Huila, In the Santander Department, Pennsylvanian and thin Devonian strata crop out beneath Carbonifer Permian rocks include the Diamante Formation and ous rocks (Stibane, 1966, 1968). Thick nonfos·silifer the Labateca Formation. Farther south in the ous sandstone (orthoquartzite in many places) in Floresta area of the Department of Boyaca, beds of the Quetame, Macarena, and Huila areas overlies similar age are referred to as the Cuche Formation dated Cambrian and Ordovician rocks and is thought (Botero R., 1959), and in the Quetame area of Cun (Trumpy, 1943; Burgi, 1961; Olsson, 1956) to be dinamarca Department as the Gachala Formation of Devonian age. (Stibane, 1966). In all areas the basal Devonian sediments consist The Diamante Formation in the Bucaramanga of conglomerate or other coarse clastic rocks that .region crops out in several small areas. It appears rest with strong angular discordance upon older to be separated from the underlying Floresta For rocks. Apparently these sediments were deposited in mation (Devonian) by a pronounced unconformity 10 NORTHERNMOST ANDES, COLOMBIA ~------~a~·------7~5~·------~?To~·------~65" CARIBBEAN SEA VENEZUELA 215 m.y. PACIFIC 5 OCEAN 220 m.y. EXPLANATION e!J Outcrop areas of middle and upper BRAZIL Paleozoic rocks P , Permian rocks; C, Carboniferous rocks; D , Devonian rocks B Epicontinental facies ~ Miogeosynclinal facies ~ Eugeosynclinal facies v v v Submarine volcanic rocks ? l ( Suspected metamorphosed Paleozoic rocks X XX Axis of late Paleozoic orogeny 5 .~~2=2=0=m~·~·~R=a=d=i=om==e~t~ri=c~a~g~e~------L------_J r---l-~.CfJ..,._5..._f__ +o _____lOO.L 1 _.---,,....--2 FIGURE 4.-Sketch map showing the paleogeography, facies, and location of outcrops of midldle and late Paleozoic age (from Biirgl, 1967), the axis of the late Paleozoic orogeny, and radiogenic ages. PHANEROZOIC SEDIMENTATION AND OROGENY 11 and from the overlying Tibur6n Formation by a mun., 1969) regarded these rocks as probably cor somewhat less pronounced unconformity (D. E. relative with the Macuira Formation. A sample of Ward, Richard Goldsmith, Jaime Cruz B., and H. amphibolitic and biotitic gneiss from the Sevilla Restrepo, unpub. data, 1973). The lower 450 feet Complex gave a K/Ar age of 250 m.y. (MacDonald of the Diamante consist~ of purple sandstone con and Hurley, 1969) ; m·etamorphism here thus ap taining intercalated limestone; the upper 750 feet is pears to be of Late Permian age. dark-gray argillaceous limestone. Fossils collected Rocks in the eastern part of the Central Cordil by Ward indicate a Middle Pennsylvanian to Middle lera consist of m·etamorphos·ed carbonaceous pelite, Permian age for the Diamante Formation. wacke, graywacke, and sandstone, and include a In the Bucaramanga region, the Tibur6n Forma prominent belt of marbleized limestone. Meta tion is overlain by the Bocas Formation (Triassic). morphism has destroyed all vestiges of fossils in the The Tibur6n consists largely of massive beds of con rocks. On the basis of lithology these rocks appear glomerate whose pebbles are derived mainly from to have been deposited under miogeosynclinal the Diamante Formation. conditions. The thick predominantly Carboniferous Labateca In the central and western parts of the Central Formation in Santander Department and beds of Cordillera, volcanic tuffs and lava flows, now meta the Sumapaz section in Cundinamarca Department morphosed to greenstone, greenschist, and amphi may include some strata of Permian age in their bolite, are progressively more abundant westward; uppermost parts. they clearly belong to an eugeosynclinal facies. At the latitude of Ibague ( 4 °25' N., south of the LATE PALEOZOIC OROGENY area of pl. 1) , paraschist and orthoschist of the Upper Paleozoic rocks of the Eastern Cordillera Central Cordillera were defined by Nelson (1957) are little metamorphosed and, except in the Serrania as the Cajamarca Group. At Payande 10 miles south de Perij a area, are little disturbed; most dip at low east of Ibague, these rocks are overlain by the fos to mode·rate angles, which led Stibane (1967) to siliferous Payande Formation of Late Triassic age. ascribe their deformation principally to vertical In the Medellin area (pl. 1), Botero A. (1963) refer movements. The composition of the rocks indicates red to similar metamorphic paraschist as the Ayura deposition under miogeosynclinal conditions, and Montebello Formation. North of Yarumal in the their structural attitudes indicate deformation over Department of Antioquia, R. B. Hall (Hall and a cratonic platform. In the Guaj ira Peninsula, the others, 1972) referred to similar rocks and inter- Sierra Nevada de Santa Marta, and the Central 1 bedded volcanic rocks as the Valdivia Group, and to Cordillera, however, the Paleozoic rocks are repre migmatitic rocks of higher metamorphic rank as the sented by low- to high-rank paraschist and para Puqui Metatonalite. Two samples interpreted by gneiss that were certainly metamorphosed before Hall as syntectonic orthogneiss of the Puqui Meta the Late Triassic. These metamorphic rocks are very tonalite, gave a K/Ar age on biotite of 239 ± 7 m.y. distinct from the little-metamorphosed Paleozoic and on muscovite of 214 ± 7 m.y. (fig. 4; pl. 1), indi formations of the Eastern Cordillera (fig. 4). cating a minimum Late Permian to Early Triassic In the Guajira Peninsula, the Uray Gneiss Mem age for the metamorphism. A sample from the ber and paraschist of the Macuira Formation under Amaga stock southwest of Medellin gave a K/Ar lie red beds of the La Quinta Formation of Triassic age on biotite of 215±7 m.y. (fig. 4). age and Middle Jurassic marine strata (MacDonald, Thus far no rocks from the Central Cordillera 1964; Lockwood, 1965; Alvarez, 1967) (fig. 4). The have yielded radiogenic ages older than Permian. Macuira Formation is intruded by granitic rocks. Had regional metamorphism in the Central Cordil Muscovite from an associated pegmatite gave a lera taken place in early Paleozoic time, one could K/Ar radiogenic age of 195 ± 8 m.y.; metamorphism reasonably expect to find there some fossiliferous of the Macuira and plutonic intrusion thus predate upper Paleozoic strata, equivalent in age to the un this Triassic pegmatite and of course the Triassic metamorphosed or little metamorphosed miogeosyn red beds that overlie the basement rocks. clinal strata of the Eastern Cordillera, but such In the Sierra Nevada de Santa Marta, paraschist, rocks have not been found. The existence of Ordo orthoschist, metadiorite, and amphibolite form an vician graptolites near Cristalina (Harrison, 1930) arcuate belt (Sevilla arc) northwest of the Precam may indicate that these rocks are not in their true brian platform area (pl. 1). Tschanz (written com- palinspastic position because of structural disloca- 12 NORTHERNMOST ANDES, COLOMBIA tion as suggested by Feininger (written commun., block may be oorrelative in part with the Los Indios 1969). Regional metamorphism of the rocks in the Formation, although its variable lithology is more Central Cordillera is thus considered to be of late variable than that of the Los Indios Formation. The Paleozoic age. Corual Formation OOI18ists of a basal conglomerate The apparent near simultaneity of comparable overlain by siltstone, graywacke, shale, chert, and events in the Guaj im Peninsul•a, Sierra Nevada de abundant mafic to silicic lava and volcanic tuff; some Santa Marta, and in the Central Cordillera along of the lava and tuff is keratophyric to spilitic strike, continuity in trends of structural grain and (T.schanz, written commun., 1969). The Guatapuri in geographic distribution, suggest that miogeosyn- Formation on the southeast flank of the Sierra clinal deposition extended from the sialic continental Nevada de Santa Marta overlies the Corual Forma platform westward and northward to its outer edge tion and consists of 10,000 to 14,000 fe·et of well and that eugeosynclinal sediments accumulated in a bedded crystal and lithic tuffs that are reddish and trough along the foreland of the continent during can easily be confused with other Colombian red the Paleozoic Era (fig. 4). The outer edge of the bed formations. This formation appears to have sialic platform probably is some tens of kilom.eters been deposited in a narrow northeast-trending beyond the present outermost exposures of Precam- trough (Tschanz, unpub. data, 1969), as it is poorly brian granulites. At the close of the Paleozoic Era, represented along the southeast side of the Cesar this natural mobile zone in the outer crust appears Basin (fig. 1), wher·e ~similar red beds are younger to have been subjected to the most intense orogeny and contain less volcanic rocks. In the Sierra Ne recorded in Phanerozoic rocks of Colombia. This vada de Santa Marta, volcanism increased in inten orogeny gave rise to the ancestral Colombian Andes. sity through the Triassic and extended through Intense ·regional metamorphism, local anatexis, and much of the Jurassic and locally continued into sporadic igneous intrusion converted the zone into garly Cretaceous tim·e. During the Triassic, the an area of cratonic attributes which has character- area of volcanism extended southward into the Cen ized the Central Cordillera, central Sierra Nevada tral and Western Cordilleras. de Santa Marta (Sevilla arc), and Guajira Penin- In the Santander region of the Eastern Cordillera, sula (Guajira arc) throughout much of subsequent the Bocas Formation was deposited under paralic to geologic time. nonmarine conditions, nearly conformable with the The late Paleozoic orogeny clearly resulted in underlying Surata Group of late Paleozoic age. The some continental accretion, which is repres·ented by Bocas is composed of sandstone and shale that the belt of metamorphosed eugeosynclinal sedimen- weather buff; it ap·pears to have been deposited mar tary rocks now exposed along the western side of ginal to a Triassic seaway that transgressed south the Central Cordillera in the Department of Anti- ward fro·m the Sierra Nevada de Santa Marta area oquia. This belt is covered by younger rocks west- into the Santander Dep,artment, through the De ward (fig. 9) and northward prasse.s beneath younger partment of Boyaca, and into the Payande area (fig. rocks and the Caribbean Sea. The total width of the 5) of the Department of Tolima. In the Department belt of metamorphism is unknown; for only the in- of Boyaca, a black shale sequence containing Es- ner side of the belt is now exposed. theria and small gastropods is called (Hubach, MESOZOIC ROCKS AND OROGENY 1957a) the Montebel Formation. At Payande, a TRIASSIC prominent basal conglomerate overlain according to The first incursion of seas after the Central Cor- Nelson (1957), by 500 feet of barren sandy shale dillera-Sevilla arc-Guajira arc orogeny in late Paleo- (Prepayande Formation of Renz, 1960), is in turn zoic time is represented by the Los Indios Formation overlain by 500 feet of fos.siliferous limestone and along the southwest flank of the Sierra Nevada de associated calcareous rocks (Payande Formation) of Santa Marta (fig. 5). The Los Indios Formation Late Triassic age. The Payande is overlain by 1,600 overlies Precambrian rocks and consists of a lower . feet of mafic lava flows, agglomerate. and tuff (Post- 600-foot-thick fos,siliferous black shale and a~ upper payande Formation). Hubach (1957a) tentatively 1,000-foot-thick gre.en arenaceous member contain- 1 corvelated the Payande Formation with the Los ing some conglomerate and tuff beds. Ostracodes in Indios and the Montebel Formations. The fossils in the formation are tentatively regarded as Late Per- each of the formations differ, however, and a re mian ( ?) or Early Triassic. The Corual Formation .study of them is needed to arrive at firmer of the north and southeast sides of the mountain correlations. PHANEROZOIC SEDIMENTATION AND OROGENY 13 0 r------~a~o~o------7~5~o------~7r0~--______,65° CARIBBEAN·SEA VENEZUELA 0 c 0 0 0 0 0 0 0 0 0 0 160! 30 m. . ( J ) I OCEAN EXPLANATION Outcrop areas. J , Jurassic rocks; BRAZIL R , Triassic rocks Miogeosynclinal facies Eugeosynclinal facies Continental red-bed facies of Jordan and Giron + Formations (Juras..qic), La Quinta Formation (Venezuela) VVV Volcanism x X X Axis of Late Triassic-Early Jurassic orogeny accompanied by magmatism 5 o·L-~·=16=0=±==7=m~.Y=·=(J=)~R~a~d~i~o~m~e~t~ri~c~a~g~e~of~gr~an~I~·t~ic~p~lu~to~n ______j______j 100 200 300 400 KILOMETRES 190 sp o I I I I I I 100 50 t H!)() 2b0 MILES FIGURE 5.-Sketch map showing the paleogeography, facies, and location of outcrops of Triassic and Ju-rassic age (from Biirgl, 1967), the axes of Upper Triassic to Lower Jurassic plutons, and radiogenic ages. 14 NORTHERNMOST ANDES, COLOMBIA The Triassic Period closed with the initiation of responding approximately in age with the volcanic intrusion of several large batholiths in the Sierra rocks in the Sierra Nevada de Santa Marta. Nevada de Santa Marta and in the Santander De In the Department of Boyaca, the Jurassic (Hu partments in the Eastern Cordillera. The age of the bach, 1957a) is represented by the Arcabuoo Forma earliest batholiths is older than 202 ± 13 m.y., deter tion (fig. 5), which consists of massive, light-colored mined on a diorite on the west side of the Sierra sandstone containing thin intercalations of red shale. N.evada de Santa Marta (pl. 1) . Other early ages On the lower Bata River, Biirgl (1960b) identified range from 195±8 m.y. (fig. 5) for a pegmatite as fossiliferous littoral quartzos.e sandstone of late Li sociated with a granite that cuts the Macuira For assic (Early Jurassic) age, 4,250 feet thick, sepa mation in the Guajira Peninsula, to 193 ± 6 and rated by a stratigraphic hiatus from 2,600 feet of 194±6 m.y. (pl. 1) (K/Ar, biotite) for the Santa overlying dark-gray shale of Tithonian (latest Juras Barbara and Pescad·ero batholiths southeast of sic) Age. Rus·sell Travis (written commun., 1970) Bucaramanga. Empl.acem·ent of batholithic masses reported that the shale may be as much as 8,500 began slightly befor·e the close of the Triassic. Some feet thick. were emplaced during an interval that spanned the The most distinctive sedimentary beds of Jurassic Triassi~-Jurassic time boundary; others, as indi age in Colombia are continental red beds of the cated by radiogenic ages of 170 to 160 m.y. (fig. 5; Giron Group that extend from Serrania de Perija pl. 1), were emplac-ed during the Jurassic. The in southward along the Eastern Cordillera at least as trusions are mesozonal to epizonal and discordant, far as Floresta in the Department of Boyaca, and but their form is influenced by the gross structures may extend as far south as the Department of Huila of the encasing Pr·ecambrian and Paleozoic rocks. ( figs.1, 5). The Giron Group is correlated in part with the La Quinta Formation of western Venezuela JURASSIC and possibly with the Chapiza Formation in Ecua dor. In Colombia, som·e confusion has resulted from The marine Cosinas Group (fig. 5), 5,000 feet the practice of assigning all red beds of this approxi thick and ranging fro·m Middle to Late J uras;sic age, mate position in the stratigraphic column to the was deposited in a trough on the Guajira Peninsula Giron, whereas in fact red beds in Colombia range (Rollins, 1960). The Cosinas trough in which this in age from Carboniferous (parts of the Gachala group was deposited must have been exceedingly Form·ation), through Triassic (Guatapuri Forma- narrow. tion of the Sierra Nevada de Santa Marta) and On the southeast slope of the Sierra Nevada de Jurassic, to and including the Rio Negro Forma Santa Marta, Jurassic rocks of various formational l tion of Early Cr.etaceous age in the Serrania de names are represented by a thick section of sub Perija. The Giron Group, in pa·st literature, for lack aerial volcanic breccias, flows, and welded tuffs that of satisfactory fossil evidence, therefore, has been range in composition from andesite to rhyolite. Vol assigned ages ranging from Pennsylvanian (Lang- canism (Triassic and Early Jurassic) apparently enheim, 1961) to Jurassic. preceded emplacement of most of the batholiths. At the type locality and vicinity, Cediel (1968) T:schanz (unpub. data, 1969), however, observed 1 1 was able to ·separate two red-bed sequences in the that in some areas keratophyric and spilitic Triassic ! Giron Group. He defined the older, finer, and more volcanism antedates batholithic intrusion. In other uniform grained s.equence in the canyon of the areas, dacitic to rhyolitic volcanis.m and Jurassic Sogamoso River, where it contains interstratified plutonism are ess·entially peneconte,mporaneous. In volcanic material (ignimbrites), as the Jordan For still other areas, Cretaceous rhyolitic ignimbrites mation. Overlying these beds are the normal quartz rest unconformably upon Jurassic batholiths. OS·e Giron-type beds that are relatively free of vol At Morrocoyal (fig. 5), Trumpy (1943) des·cribed canic materials. Cediel considered the Jordan For the Morrocoyal Formation as consisting of a lower mation as late Paleozoic and retained the oft-used unit of fossiliferous black shale and thin limestone "Juratriassic" age designation for the Giron Group interbedded with red beds, shale, and sandstone, and in the belief that the age of plutonism in the nearby an upper. unit of mafic. volcanic rocks. On the basis Eastern Cordillera was probably late Paleozoic ; he of rich f.aunas, the lower Morrocoyal beds are con concluded that the Giron red beds were a molassic sidered to be Liassic. The thick volcanic sequence offwash from that area after uplift. D. E. Ward (in overlying them thus may be Middle Jurassic, cor- D. E. Ward, Richard Goldsmith, Jaime Cruz B., and PHANE-ROZOIC SED'l:MENTATION AND OROGENY 15 H. Restrepo, unpub. data, 1973), however, collected P'aroxysm. Jurassic volcanic rocks seem to reflect a granite cobbles out of the base of the Jordan Fonna continuation of the volcanism that began in the Tri tion, which Richard Goldsmith identified as proba as·sic. Little metamorphism •appears to be associated bly having been derived from the nearby Los Clavos with the intrusions, and their relations to the coun Granite, radiometrically dated as Early Jurassic in try rocks suggest that most were intruded at com age. Thus, both the Jordan and Giron bed·s near their paratively low tem·pe:rtatures and shallow depths. type localities should probably be regarded as Mid The batholiths are situa;ted on the eastern or inner dle to Late Jurassic .age; the uppermost beds indeed · side of the late Paleozoic orogenic arc and do not may extend into the Early Cretaceous. seem to be associated with a tectogene in the normal Volcanic material is prominent in the belt of sense. Jurassic rocks along the east side of the Central Cordillera, overlying the Lower Juras1sic (Liassic) CRETACEOUS marine beds of the Morroooyal Form·ation of the As the detailed stratigraphy of the Cretaceous Middle Magdalena Basin. On the Anacue River has been amply described in several outstanding southwest of Barrancabermeja (pl. 1), these strata publications by N otestein, Hubman, and Bowler are intJ r------~so~·--______,75~·------7~o~·------~65" CARIBBEAN SEA VENEZUELA 70-80m. ·. PACIFIC OCEAN EXPLANATION BRAZIL Miogeosynclinal facies Eugeosynclinal facies XXX Late Cretaceous orogenic axis vvv Subaerial and submarine volcanism 70-SOm.y. Radiometric age of plutonic rocks 5"'~------L------~ .---1•9..,0,..5..a.P--+OI---1C..a...... f--,.--29.&..0___ 39L.O-r---_4....J90 Kl LO METRES 1& sb 0 1b0 2bOMILES FIGURE 6.-Sketch map showing the paleogeography and facies of Cretaceous age, the axis of Upper Cretaceous plutons, and radiogenic ages. PHANEROZOIC SEDIMENTATION AND OROGENY 17 these two predominantly negative areas. The axis indicating a metamorphic provenance for these of the Santander arch coincides approximately with flysch-type ,sedimentary rocks, doubtless from the the axes of the Late Ordovician orogeny, Late De adj aoent Central Cordillera. Some recrystallization vonian or Carboniferous disturbance, and the Late to albite, epidote, chlorite, actinolite, sericite, and a Triassic-Middle Jurassic orogeny. little pumpellyite indicates that the Cafiasgordas The western margin of the Cretaceous miogeo rocks have undergone a very low grade, probably syncline was the ancestral Central Cordillera that lithostatic, metamorphism in strong contrast, for · formed at the end of the Paleozoic. During the Cre instance, to the high-pressure metamorphism char taceous the range was emergent but low, except for acteristic of Mesozoic eugeosynclinal rocks in many a brief interval in Aptian-Albian time when its cen parts of the circum-Pacific folded mountain belts. tral part was submerged (fig. 6). The miogeosyn Cretaceous rocks constitute the bulk of the West cline extended far east of the present Eastern Cor ern Cordillera. They extend from Ecuador in the dillera, for exploratory drilling by oil companies south almost to the Gulf of Uraba (pl. 1) in the shows that Cretaceous sedim.entary ~ocks subcrop north. Judging from the presence of mafic igneous beneath the present Tertiary s·edim·entary m·antle rocks and their derivatives along the Boliv·ar fault east of that cordillera. High-level aeromagnetic sur (pl. 1) of the Carihbean Coastal Plain (Zimmerle, veys east of the Eastern Cordille~a front, in fact, 1968), the mafic composition of amphibole schist in show that the depth to crystalline basem·ent in cer the northwestern Sierra N ev·ada de Santa Marta tain areas may be as much as 30,000 feet. These (T·schanz, writtJen com.mun., 1969), and the volcanic depths are a composite thickness of Tertiary and rocks and serpentinite in parts of the J ara:ra and Cretaceous rocks and locally may include Paleozoic Etpana Form,ations of northwest Guajira Peninsula strata. (Lockwood, 1965), the eugeosyncline in which these The enormous volume of clastic sediments in the rocks were deposited extended to the northeast and miogeosyncline must have been derived in the main possibly into northern Venezuela to the east. Lock from the Guayana shield to the east and southeast. wood (1965) and Alvarez (1967) found identifiable Some material was de·rived fr·om the Central Cor Cretaceous Bryozoa in the Jarara and equivalent dillem, because Cretaceous strata along the eastern rocks, despite the .low-grade metamorphism to which flank of that cordillera contain clasts of chert and these rocks have been subjected. metamorphic rocks that differ from clasts in Cre taceous sedimentary rocks elsewhere in Colombia. LATE MESOZOIC OROGENY In the Western Cordillera a thick sequence of sub Along this arcuate western eugeosynclinal belt marine mafic volcanic rocks and beds of gray to the Cr~etJaceous Period closed with an orogeny that black shale, graywacke, and dark chert, as much as began with strong folding and emplacement of many 30,000 feet thick and perhaps much thicker, con sm·all mas,ses of ALpine-type ultramafic rocks and tinued to be deposited in the eugeosyncline that s·erp.entinite. The o~rogeny ended with emplace·ment began to form during tJhe Jurassic. According to of the large discordant Antioquian batholith and sev Hubach (1957a), Tulio Ospina first described these eral satellite stocks along the inner side of the arc. rocks in 1914. The sequence was later named the The Antioquian and Sons6n batholiths 'in the Cen "Porphyritic Formation" (Gros·se, 1926), and still tml Cordillera are well dated radiogenically at 70- later the "Diabas·e Group" (Nelson, 1957). In the 80 m.y. (Maestrichtian). Cretaceous sedimentary northern part of the Western Cordillera, sedimen and volcanic rocks are affe0ted only by low-grade, tary beds locally predominate over volcanic material, mainly contact, metamorphism, in contrast to the and these strata are referred to as the Quebrada low- to high-rank regional ·metamorphism of pre Grande Formation and the Cafiasgord-as Group. Fos Mesozoic rocks. This Late Cretaceous orogenic sils collected at various localities along the length of event is significant in the structural evolution of the the Western Cordillera indicate that these rocks northernmost Andes, beoaus·e it gave rise to the represent most of Cretaceous tim·e (Hans Biirgl, Western Cordillera alongside and oceanward from unpub. data, 1967). the Central Cordillera (pl. 1, fig. 9) and to the Petrographic study (Philipa Black1 written com ooeval fold belt along the Caribbean coast; it also mun., 1969) of samples of the Gafiasgord·as Group gave rise to the second clear case of continental ac showed abundant detrital biotite, musoovite, quartz, cretion in Colombia. Little folding is found in and feldspar, and lithic fragments of quartz-mica schist, only minor disconformities are noted between Cre- 18 NORTHERNMOST ANDES, COLOMBIA taceous and lower Tertiary rocks in the miogeosyn EOCENE clinal area to the east and southeast of the Late Sandstone and conglomerate appear in middle and Cretaceous fold belt. upper Eocene rocks over a wide area and are the result of regional diastrophism during late early to CENOZOIC ROCKS AND OROGENY middle Eocene tint·e. This diastrophism reflects a The stratigraphy of the Tertiary in Colombia is strong orogeny that took place along the outer summarized in the comparatively few but significant ( northwe,st) Sierra Nevada de Santa Marta and on works by Notestein, Hubm,an, and Bowler (1944), the northwe,st side of the Guajira Peninsula. The oro Anderson (1945), Morales and Colombia ~etroleum genic belt extends southward along the Central Industry (1958), van der Hamm·en (1958), BUrgi Cordillera. During this orogeny, Cretaceous S·edi (1961); and Van Houten and Travis (1968). Texts mentary rocks of the Guaj ira Peninsula and the accompanying geologic quadrangle sheets published Sierra Nevada de Santa Marta in the orogenic belt by the Colombian Instituto N acional de Investigaci were m·etamorphosed to greenschist. The orogeny ones Geol6gico-Mineras provide additional general culminated with the emplacement, respectively, of ized information. the Santa Marta, Parashi, El Bosque, and other plu In g·eneral, marine Cenozoic deposits are confined ton:s. Radiogenic ages indicate that metamorphism to coastal zones; almost all the deposits in the interi possibly began as early as Late Cretaceous (Tschanz, or are nonmarine. Strata ranging mainly from Pale written commun., 1970) and ended before the em ocene to Oligocene are widely distributed; Miocene, placement of the plutons between 50 and 48 m.y. Pliocene, and Pleistocene streta, except in the coast ago (late early to early middle Eocene time; fig. 7). al deposits, are more localized and appear to have H. Duque (written commun., 1970) reported a been deposited as coars·e clastic fills in intermontane notable stratigraphic hiatus throughout Colombia in basins. In the coastal plains, Cenozoic sections, from the middle Eocene. This hiatus repres.ents an oroge Paleocene to Holocene, are complete. Most Pliocene ny that m.ay correspond with deposition of the San and all Pleistocene deposits overlie older Tertiary Jacinto and Maco Conglomerates in the Lower Mag formations with notable angular discordance. dalena Basin, with the unconformity at the base of the thick and massive La Paz Sandstone that trans PALEOCENE gresses the eroded edges of the gently folded Lisama In the Eastern Cordillera, Cesar Basin, southwest Formation (Taborda, 1965), and with deposition of Maracaibo Basin, and the Magdalena Basin (fig. 1), the Gualanday Conglom·erate of the Middle Magda uppermost Cretaceous marine formations are gen lena Basin, the Mirador Sandstone of the western erally conformable with the overlying dominantly Maracaibo Basin, the Limbo (Mirador?) Shale and clastic nonmarine Tertiary formations. The Paleo sandstone along the eastern flank of the Eastern cene beds are generally molassic in nature-:---;such as Cordillera, and the Jamundi Conglomerate of the the Limbo Shale and sandstone along the eastern Cauca Basin. The coal-bearing Cerrej6n Formation foothills of the Eastern Cordillera, the Barco For and other Eocene rocks of the Cesar Basin area im mation of the western Maracaibo Basin, the Lisama mediately southeast of the orogen seem to have been Formation of the Middle Magdalena Basin, and the deposited contemporaneously with the orogeny and Guaduas Formation of the Eastern Cordillera and without interruption. the Upper Magdalena Basin. Van der Hammen 1 (1958) referred to this Eocene Paleocene strata are chiefly clay, mudstone, fine orogeny as a "pre-Andean" orogenic phase. I grained poorly sorted sandstone, and local coal de In late Eocene tim:e, quiescence was restored, and posits. Sedimentation apparently took place upon deposition of fine-griined clastic sediments resumed. extensive, slowly subsiding flood plains that M·arine tongues apparently penetrated far inland stretched outward from the Central Cordillera for brief intervals, as1 indicated by marine and brack which was rejuvenated by Late Cretaceous orogeny ish-water horizons tllat are found at widely spaced (fig. 7). Besides debris deposited along the flood looalities in the LlanQs Basin and in the Easte·rn and plains at the base of the Central Cordillera, much Western Cordilleras.! Van der Hammen (1958) re- detritus was probably brought in f.rom the south and ported marine Foraminifera' in the U sme Formation southeast by north-flowing streams that drained the of late Eocene to early Oligocene age in the Eastern central continental area beyond the borders of Cordillera. Because the Central Cordillera was a Colombia. I land area of consider:able relief after the Late Cre- PHANEROZOIC SEDI.MENTATION AND OROGENY 19 r------~~------~75~·------~7~0~·------~65" CARIBBEAN SEA 10"'~------~------ VENEZUELA PACIFIC 36m.y. OC AN •+ + ••. .· "" "" .~- "' ..,+++++++:··· _._ ~ ~ + • :•• +" . "'+ Guayana shield EXPLANATION BRAZIL ~ Continental facies ~ Paralic facies D Marine facies vvv Volcanic facies XXX Axis of middle Eocene (Santa Marta-Guajira) and Oligocene (Western Cordillera) disturbances and plutonism 48 ±4 m.y. Radiometric age -2000 Restored isopach contours (approximate) of Ter tiary sedimentary rocks (contour interval, 2,000 ~Arrow indicates direction of meters) transport of detrital material 5"~------~------~ .--l-L~..,,_5_..,P_ _.,y ___l_..90_--r_2.J.f ___ 3.J.f...,._ __4..J'fl KILOMETRES 1b0 ·~0 6 1Jo 2~ MILES FIGURE 7.-Sketch map showing facies, thickness, and direction of transport of Tertiary deposits before the Andean orogeny (Miocene), location of axes of Eocene and Oligocene-Miocene plutons,and radiogenic ages of the plutons. I 20 NORTHERNMOST ANDES, COLO¥BIA taceous orogeny, the brief marine incursions to its and some shale. Volcanism in the Central Cordillera east we.re probably from the Caribbean ; in contrast, is expressed ':by abundant volcanic material within those invading the area of the present Cauc·a Basin the Miocene '·sedimentary rocks along the flanks of to its west were from the Pacific. Brief marine trans the cordiller~. N onm.arine Miocene sections, many gressions into a dominantly nonmarine environment having an unconformity at their base, are as much have also been noted along the southern margin of as 10,000 feet thick (for example, the Real Forma the Maracaibo Basin (Miller and others, 1958). tion (Morale$ and Colombian Petroleum Industry, 1958) ) a.nd dre distributed along the intermontane OLIGOCENE Magdalena al:ld Cauca Basins, beneath the eastern Material deposited during the early and middle plains (Llano's Basin), and in the southwestern re Oligocene consisted mainly of nonmarine sandstone entrant of thJ Maraooibo Basin near Cucuta (pl. 1). and shale. Occasional fingers of the sea penetrated The predominantly nonmarine formations of the inland to form key marker units, such as the upper inte~ior interllnger and pass into marine strata Mugrosa Formation of middle Oligocene age and along the C~ribbean and Pacific Coastal Plains. the La Cira Formation of l·ate Oligocene 1 to early These lithologies, together with the cessation of deposition in ·late Oligocene time over· the Eastern Miocene age. Renz (1938, in van der Hammen, 1958) I stated that the upper San Fernando Formation of CordiHera, ·sug·gest that the Colombian Andes began the western Llanos Basin and northern Serrania to take their present form and ·that deposition be Macarena contains marine and brackish-water came localized in the present basins during Miocene Foraminifera. time, where it has continued to the present. In the upper Oligooene seotions, the beds contain The d·eeo Cenozoic intermontane basins now sep·a ing conglomeratic horizons become coarser, indicat rated by the branches of the Colombian Andes have ing that transporting agents were acquiring greater been thought to represent sedimentary accumula competence. Within the present area of the Eastern tions in elongated downwa-ri>s, in half grabens, or in Cordillera, deposition see·ms to have stopped toward g.rabens ; such reasoning implies that most sedimen the close of Oligocene time, because Miocene beds, tary str~uta in these basins were derived primarily so far as we know, are absent along its axial area. from the Andean Cordillera. A recent description of Many stress adjustments have been recorded in the history and structural development of the Upper the lower Tertiary sedimentary rocks in the Upper Magdalena Basin by VanHouten and Travis (1968) Magdalena Basin, as is well documented by Van has provided information on the origin of these Houten and Travis (1968). Van der Hammen basins. (1958) referred to these earliest movements as The deepest parts of the interior basins contain "proto-Andean." extraordinarily thick, predominantly nonmarine, Concurrent with the initiation of Andean folding, sedimentary beds of early Tertiary age that are granitic plutons were emplaced along the Western overlain by coarse clastic upper Tertiary sediment Cordillera (pl. 1). Specimens collected by Gerardo ary beds. Most present topographic surfaces of the Botero A. (written commun. to Tomas Feininger, basins are less than 2,000 feet above sea level. The 1969) from batholiths east of Quibd6, between base of the Tertiary in the deepest parts of the Buenaventura and Cali, and near Pasto were ana basins, therefore, extends to depths of thousands of lyzed radiometrically by Prof. Andrew Vistelius of meters below sea level, as may be noted from the the Institute of Mathematical Geology, Leningrad, isopachs on plate 1. However, the reconstructed U.S.S.R. They range in age from early Oligocene to upper surface of the Cretaceous in the adjoining early Miocene (36 m.y. to 24 m.y.). This period of cordHleras, particularly in the Eastern Cordillera, gr.anitic intrusion oould well have been an early ascends to as much as 15,000 feet or more above manifestation of the Andean orogeny. sea level. The structural relief of the Cretaceous MIOCENE AND THE ANDEAN OROGENY Tertiary interface therefore may be as much as 10 miles within remarkably short distances (pl. 2). Miocene strata of the interior consist mainly of Examples of such structural relief are evident in many thick conglomerate beds, pebbly sandstone, sections through the Sierra Nevada del Cocuy 1 Van der Hammen (written commun., 1969) has informed me that, as (northern Boyaca Department) to the deep Tertiary a result of subsequent regional paleontological studies of the Caribbean Basin area, the upper Oligocene as used in his correlations (1958) must Llanos Basin immediately to the east (lat 7° N.; now be revised to Aquitanian, or basal Miocene. PHANEROZOIC SEDIMENTATION AND OROGENY 21 section, pl. 2) , and through the Sierra de Farallones also terminated against high-angle reverse faults east of Bogota eastward to the Llanos Basin (lat 5° that are believed to dip toward the cordillera. Un N.; section, pl. 2). Miller and others (1958) de fortunately, geologic mapping in that area is very scribed sim'ilar structural relief for the sections deficient and does not permit reconstruction of mid through the Merida Andes of western Venezuela. dle and late Tertiary events. However, the limited The relation of. the margins of the basins to ad data suggest that a similar Tertiary megabasin joining cordilleras is particularly revealing. Along existed west of the Central Cordillera, facing the the western side of the Middle Magdalena Basin, Pacific Ocean, and that it also was broken along Tertiary beds lie upon and wedge out over pre-Cre marginal reverse faults by uplift and rejuvenation taceous metamorphic and igneous rocks, whereas of the Western Cordillera. eastward they dip and thicken toward the Eastern Nonmarine Miocene sedimentation in the interior Cordillera (Taborda, 1965). The strata of the east basins was complex. As many as four sedimenta ern margin are either sharply folded upward and tion cycles have been detected within the sedimen are now eroded away (D. E. Ward, Richard Gold tary strata of the Upper Magdalena Basin (Van smith, Jaime Cruz B., and H. Restrepo, unpub. data, Houten and Travis, 1968). On the basis of sedi 1973), or are limited by v·ertical or steep reverse mentary provenances, van doer Hammen (1958) faults that dip eastward beneath the adjoining East noted similar cycles in other Colombian basins. H. ern Cordillera (pl. 2). In the Llanos Basin east of Duque (written commun., 1970) observed that there the Eastern Cordillera, on the other hand, the Ter i.s a notable stratigraphic hiatus during the middle tiary beds thicken westward from a thin veneer Miocene over much of Colombia. This break in sedi over the Guayana shield to several thousands of mentation may represent the zenith of the Andean meters at the m·argin of the cordillera, where they paroxysm. Because of the paucity of fauna and butt against westward-dipping high-angle reverse flora in the predominantly nonmarine sedimentary faults. Cenozoic sedimentary thickening in the ba beds and the considerable distances between present sins on each side of the Eastern Cordillera, there basins, individual formations are not readily corre fore, is in a direction toward the cordillera itself. lated from basin to basin. Van Houten and Travis This relation together with the. p.resence of synclinal (196-8) pointed out that the source of sedimentary trough remnants of lower Tertiary beds within the debris varied greatly in response to local diastrophic cordillera (pls. 1, 2) strongly suggests that, prior to movements and particularly in response to volcanic principal Andean folding (Miocene), the Middle activity. Magdalena and Llanos Basins probably connected Prior to the principal Andean folding in the Mio across the area of the present Eastern Cordillera, cene, the drainage pattern of northwestern South and constituted a single large interior basin (mega America may have been different from that of the basin) that opened eastward into the Barinas Basin present. Although considerable debris was undoubt and possibly extended northward into the Mara edly derived from the Central Cordillera and de caibo Basin of Venezuela (fig. 7). posited along its eastern margin by ·eastward-flowing Even during the existence of this megabasin, how streams, a good p.art of the present upper Orinoco ever, the axial area of what is now the Eastern and Amazon drainage during Cretaceous and early Cordillera anticlinorium probably was a positive Tertiary time was to the north and northwest, bring relief feature relative to the adjoining Middle Mag ing with it large quantities of debris from the in dalena and Llanos Basin areas. This relation is indi terior of the continent; this debris was deposited in cated by van der Hamm·en (1958) in a series of broad areas of general subsidence. stratigraphic columns in which the Tertiary sections All the Miocene and older strata in present Colom bian intermontane basins are folded. Termination of in the respective basins are much thicker than those sedimentation over tectonically positive areas to within the Eastern Cordillera. ward the close of the Oligocene, and continuation of Comparable stratigraphic ·and structural relations sedimentation in negative areas during the Miocene are noted on the east and possibly on the west sides suggest that the coarse clastic Miocene deposits were of the Western Cordillera at the latitude of Cali (3° folded as they were accumulating. 26' N.), south of the mapped area on plate 1. There This Miocene Andean folding is particularly sig the lower Tertiary sedimentary rocks are strongly nificant because it undoubtedly gave rise to the re folded along the margin of the cordillera and are juvenation of the Central and Western Cordilleras 22 NORTHERNMOST ANDES, COLOMBIA and the formation of the Eastern Cordillera. The cooler climate, and poUen in the uppermost beds result was the present three-prong configuration of indicates a climate comparable to that at present the Colombian Andes. Uplift of the Eastern Cordil altitudes of 8,500 feet. lera along sharp flexures and marginal reverse faults was sporadic over a long period of time, and indeed HOLOCENE may be continuing to the present. Denudation of cordilleran areas, a consequence of the Andean orogeny, was increased by late Terti PLIOCENE AND PLEISTOCENE ary epeirogenic uplift and continued actively into the Holocene. Holocene uplift is also expressed in During and after Andean folding, large quantities the "old-land" plateau area of the Central Cordillera of material, particularly the poorly consolidated Ter north of Medellin that reaches an altitude of nearly tiary formations, were stripped off the cordilleras 10,000 f·eet. The plateau .slopes gently eastward to and transported through the drainage systems of the ward the Magdalena Basin. Similar remnant sur Cauca and Magdalena Rivers (pl. 1). Most of the faces ("paramos") in the Eastern and Western Cor Pliocene and Pleistocene deposits consist principally dilleras ~nay be correlated with it genetically, if not of uplifted unconsolidated alluvial-fan deposits that in precise altitude, because epeirogenic uplift was form terraces, mesas, and cuestas along the margins not everywhere of equal. magnitude. Uplift must of the principal drainage systems. In •som,e areas have been largely acoomp.lfshed before the later part these deposits have been tilted or gently folded and of the ice age, as evidence of Pleistocene glaciation faulted, but in general they are little disturbed. can be seen on present topography down to altitudes Pliocene. and Pleistocene volcanism along the south of 10,000 fe.et (van der Hammen and Gonzalez, ern Central Cordillera contributed much debris to 1963). adjoining valleys. During the Holocene, volcanism in the Central Uplift in valley areas was negligible; in fact, cer Cordillera diminished greatly, but the pres.ence of tain valley areas must have been considerably de volcanic ash in some pres·ent soil profiles at great pressed to permit deposition of as much as 5,000 distances from known volcanic centers indicates that feet of sediments, the thickness, for exam:ple, of the volcanism continued until comparatively recent times Mesa Group (Pliocene) in the Upper Magdalena and pe·rhaps to historic tim·e (Ramirez, 1968). Basin. Howe (1969) has shown from paleocurrent studies that the lower beds of the Mesa Group re MAGMATISM quire an east-flowing drainage system during deposi Igneous activity took place in all three cordilleras tion. This drainage direction would imply uplift of of the Colombian Andes (fig. 8) but is l·east evident the southernmost Eastern Cordillera, the area in the Eastern Cordillera, which is largely blanketed known as the Garzon massif, in late Plioeene time. by sedimentary rocks (pl. 1). Igneous rocks are vol Wellman ( 1970) concluded from ·similar paleocur umetric-ally large in the Central Cordillera, the rent studies of the Honda Group (Miocene), which Western Cordillera, and the Sierra Nevada de Santa und.erlies the Mesa Group .some distance to the north, Marta. Most plutonic .rocks and .silicic volcanic rocks that it too was deposited by eastward-flowing appear to be associated with orogenic cydes, where streams descending from the east flank of the Cen as mafic volcanic rocks are related to eugeosynclinal tral Cordillera. Both observations support the prroba sedimentation. ble existence of the postulated eastern megabasin before principal Andean folding. PRECAMBRIAN Epeirogenic uplift began in late Pliocene time as The only known igneous rocks of Precambrian van der Hammen has so clearly demonstrated in his age in Colombia are in the Guayana shield. In the excellent studies of the little-deform.ed Tilata For Serrani.a Macarena, southeast of the area shown on mation north of Bogota. The basal Tilata contains plate 1, granitic magmas pervaded mafic schists to pollen of a humid tropical flora that could not have form migmatitic augen gn1ei.ss (Trumpy, 1943). flourished at altitudes greater than 1,500 feet (van Thes.e gnei·sses are overlain by Cam·brian and Ordo der Hammen, written commun., 1969). K! Ar analy vician sedimentary rocks. On the Guaviare River, sis of biotite from ash beds in the basal Tilata gave 230 miles east of the Serrania, similar rocks were a minimum age of 3.5 m.y., or latest Pliocene. Higher dated radiogenically at 1,205 m.y. (fig. 2) by K/Ar in the section, the poUen indicates ·a progressively analyses of biotite (Pinson and others, 1962). MAGMATISM 23 /SANTA MARTA-BUCA AMANGA FAULT CARIBBEAN SEA \ VENEZUELA IC ~--~....-.~.. II[.. "• .L.---'-+t§~ :o rt hogo e iss " It •,...... ,. .. PAC FIG OC AN ECUADOR EXPLANATION GRANITE PROVINCES BRAZIL ~ Tertiary (58-24m.y.) ~ Cretaceous (130-68m.y.) bd Upper Triassic to Jurassic (200-140m.y.) § Upper Permian to Lower Triassic (250-215m.y.) ~ Middle and Upper Ordovician (480-430m.y.) 0 Precambrian (>1350m.y.) 100 50 0 100 300 400 KILOMETRES I I I I I I I ! I I 100 50 100 200 MILES FIGURE 8.-Sketch map showing tentative distribution of granitic intrusive rocks by age provinces. 24 NORTHERNMOST ANDES, COLOMBIA LATE ORDOVICIAN varez, 1967). K/Ar ·analysis of muscovite from a Syntectonic biotite-quartz-feldspar orthogneiss pegmatite associated with the granite gave an age forms sills of considerable thickness concordant with of 195 ± 8 m.y. (MacDonald, 1964). Metamorphism the foliation of the Bucaramanga Gneiss and Sil and granite intrusion certainly preceded the appar gara Schist in the Bucaramanga region (Santander ent Upper Triassic pegmatite. massif) in the Eastern Cordillera. This magmatism, which ranges in age from 450 ± 80 to 413 ± 30 m.y. TRIASSIC AND JURASSIC (fig. 3), is associated with the Late Ordovician Magmatism in Colombia was exceedingly wide orogeny. spread throughout the Mesozoic Era, producing At San Jose de Guaviare op. the Guaviare River mesozonal and epizonal p.Iutons, shallow hypabyssal in eastern Colombia, alkalic syenitic rocks range in intrusive rocks, and large volumes of submarine and age from 485 ± 25 m.y. to 445 ± 22 m.y. (fig. 3; Pin ·Subaerial volcanic rocks. Earliest volcanic activity son and others, 1962). These intrusions on the shield is expressed in the spilitic volcaniclastic sedimentary appear to be removed from the Upper Ordovician rocks, ignimbrites, and volcanic breccias of the granitic province, and their alkalic compo,sition may Corual and Guatapuri Formations of the Sierra N e be a reflection of the cr·atonic environment in which vada de Santa Marta, regarded by Tschanz (written they were emplaced. oommun., 1969) as mainly of Triassic age. If the lower Dagua Group of the Western Cordillera is as LATE PALEOZOIC old as Jurassic, as some believe (Biirgl, 1961), then Late Permian to Early Triassic magmatism is its basaltic rocks ar·e contemporaneous with and represented by intimately mixed rocks that crop strongly contrast with the heterogeneous differenti out over wide areas of northern Antioquia in the ·ated Jurassic volcanic rocks of the Sierra Nevada de Central Cordillera. East and west of the Romeral S.anta Marta and the Central Cordillera. fault at the latitude of Puerto Valdivia, gneissoid Most impressive are the many granitic plutons of metatonali te is regarded by R. B. Hall (Hall and the Sierra Nevada de Santa Marta and of the San others, 1972) as synmetamorphic, and possibly ana tander massif in the Department of Santander. Six tectic, in origin. The metatonalite is so intimately or more plutons that approach or exceed batholithic mixed with high-grade gneis·s of the Puqui Meta dimensions crop out in each of these areas. Intrusion tonalite that it is very difficult to map separately. in both areas appears to have begun about 200 m.y. K!Ar ages on muscovite and biotite, respectively, ago (latest Triassic) and continued intermittently are 214 and 239 m.y. (pl. 1). The biotite age (Late to about 143 m.y. ago (early Late Jurassic). In the Permian) is believed to date most closely the re Santander m•assif, the southern plutons are pink and gional metamorphism of the Central Cordillera. At potassic, whereas the northern plutons are gray and Amaga (southwest of Medellin), a pos.tmetamorphic calc-alkalic. In the Sierra Nevada de Santa Marta, quartz monzonite stock gave a reported age of 215 ± potassic and calc-alkalic plutons, although trending m.y. (Early to Middle Triassic) by K/Ar analysis of northeast have the sam·e spaUal relationship with biotite. one another as do those in the Santander massif. Some ultramafic intrusive rocks in the Central Within this period of magmatism, several diorite Cordillera have been metamorphosed to talc schist to quartz diorite plutons intruded Precambrian and may have been emplaced during a late stage of gneiss and Paleozoic metamorphic rocks east of the the development of the Paleozoic eugeosyncline. The Otu fault along the easte-rn flank of the Central Cor bodies are generally of small dimensions. Most ser dillera. A K!Ar determination on hornblende from pentine bodies, however, are little metamorphosed, a diorite near Virginias gave an age of 160±7 m.y. and these are most probably associated with the (fig. 5; Feininger and others, 1973). A sample col younger Mesozoic eugeosynclinal suite. lected by Dario Barrero L. south of the mapped area The Don Diego Gneiss (metadiorite ?) of the shown on plate 1 from the very large lbague quartz Sevilla arc in the Sierra Nevada de Santa Marta diorite batholith gave a K/Ar age on hornblende of gave a K/Ar age on hornblende of 250 m.y., or Late 143±9 m.y. Permian (MacDonald and Hurley, 1969). Volcanic rocks of intermediate to silicic composi Retrograded gneiss and metamorphosed granite . tion and subaerial origin are abundant in the Sierra enclosed in the Macuira Formation of the Guajira Nevada de Santa M·art.a, are less common along the Peninsula are probably of late Paleozoic a;ge (AI- east side of the Central Cordillera, and are rather MAGMATISM 25 sparse in the Eastern Cordillera. In the Sierra N e became parts of the "Porphyrite" or "Diabase" for vada de Santa Marta, postspilitic volcanic rocks have mations of the Western Cordillera; the greenschist been dated by K/Ar analysis as 177 m.y. to 129 m.y. of the Taganga Group and amphibolite-grade schist old, or ranging from penecontemporaneous with the of the Gaira Group of the Sierra Nevada de Santa Jurassic batholiths to postbatholithic in age. Marta; and the greenschist of the Jarara and equiva lent formations of the Guajira Peninsula. Also, ~mall CRETACEOUS isolated ultramafic and s-erpentinite bodies form On the west side of the Sierra Nevada de Santa several prominent north-striking belts along the west Marta, biotite from the Rio Sevilla granodiorite side of the Central Cordillera and in the Western stock was dated as 131 ± 4 m.y. (Early Cretaceous), Cordillera, and irregular ultramafic bodies are on which is considered about the same age as the Golero .the Guajira Peninsula (pl. 1). Most of the ultramafic Rhyolite farther east (Tschanz, written commun., bodies are faultbounded, and it is difficult to deter 1969). Biotite from a granite drill core from a well mine their age relative to enclosing rocks; they are in the Cicuco oil field, 125 miles to the south, was of Alpine type, serpentinized but little metamor dated (Pinson and others, 1962) as 100-115 m.y. phosed, and mainly predate the neighboring batho (late Early Cretaceous). Northwe·st of Puerto Val- liths. The mafic volcanic and ultramafic intrusive divia in northern Antioquia, the small Pescado rocks of Cretaceous age contrast strongly, and per quartz diorite stock intruding the Puqui Metatonalite haps significantly, in composition with the Cre gave a K/Ar age (fig. 6) on biotite of 95.6±3.3 m.y. taceous silicic volcanic rocks of the Central and (early Late Cretaceous). Eastern Cordilleras, and of the Sierra Nevada de In the Central Cordillera, several massive medi Santa Marta. um- to coarse-grained epizonal to mesozonal granitic batholiths and stocks were emplaced during the Late TERTIARY Cretaceous orogeny. The most outstanding among Tertiary intrusive rocks crop out at several points these are Antioquian batholith (3,000 sq miles) and on the Guajira Peninsula, the northwest Sierra Ne the smaller Sons6n batholith. to the south (pl. 1). vada de Santa Marta, and along the Western Cordil Radiogenic ages from the Antioquia and Sons6n lera. One _K/ Ar age on biotite from the fine-grained batholiths range from 68 to 80 m.y. This range of Parashi quartz diorite stock of the Guajira Penin ages suggests that empl,acement may have extended sula is 48±4 m.y. (fig. 7, pl. 1; Lockwood, 1965). over a considerable period of time. In the Sierra Nevada de Santa Marta, a ·coarse Thes-e data show that a belt of silicic intrusions grained quartz diorite pluton extends from the city passes beneath the Tertiary and alluvial fill of the of Santa Marta to the northern coast and reappears Lower Magdalena Basin and extends from the Sierra at several points along the northern flank of the Nevada de Sarita Marta to the central part of the Sierra Nevada de Santa Marta. Several K/ Ar analy Central Cordillera. The ag-e of the intrusive rocks ses on both hornblende and biotite from this pluton ranges from Early Cretaceous in the Sierra Nevada yield radiometric ages between 49 and 51 m.y. (fig. de Santa Marta to Late Cretaceous (Maestrichtian) 7, pl. 1; Tschanz, written commun., 1969). A sam in the Central Cordille·ra. The progressive southward ple collected from the El Bosque bathqlith north of decrease in age suggests a migrating magma front, Ibague (quadrangle K-9, south of the area of pl. 1) which moved along and parallel with the general gave a K/Ar age on biotite of 49.1 ± 1.7 m.y. (Mar strike and grain of the Central Cordillera. vin, written commun., 1971), indicating that the In the Eastern Cordillera, a sanidine concentrate extensive Cretaceous magmatism of the Central Cor from a rhyolite porphyry probably associated with dillera continued locally into the early Tertiary. the Ocana porphyritic microgranite gave a K/Ar Igneous intrusive rocks of the Western Cordillera age of 127±3 m.y. (Early Cretaceous; fig. 6), ap east of Quibd6, Choc6 Department (pl. 1), on the proximately correlative with the igneous activity of highway between Buenaventura and Cali in Valle the Sierra Nevada de Santa Marta. Department, and near Pasto in the Department of In the Western Cordillera, in the northeastern Narifio, have ages reported to be 24-36 m.y. (fig. 7, Sierra Nevada de Santa Marta, and in the north pl. 1; Gerardo Botero A., oral commun., 1970). western corner of the Guajira Peninsula, subm·arine Tertiary plutonism is mainly early Eocene to basaltic and diabasic rocks were extruded intermit early Miocene in age. The intrusions are predomi tently on the floor of the eugeosyncline. These rocks . nantly along the outermost fold belt of the Andean 26 NORTHERNMOST ANDES, COLOMBIA Cordillera and extend from the Guajira-Sierra Ne upper Paleozoic and Lower Triassic plutons and ana vada de Santa Marta area in the north to and along tectites closely related to and associated with highly the Western Cordillera, at least as far south as the m·etamorphosed sedimentary and volcanic rocks of Ecuadorian border. Paleozoic age crop out along the Central Cordillera Along the valley of the Cauca River, many steep and along a curving arc that passes through the sided hypabyssal porphyritic volcanic plugs intrude Sierra Nevada de Santa Marta as the Sevilla Com Tertiary strata. The plugs are regarded as late Ter plex (as denoted by Tschanz, written commun., tiary in age and possibly are related to upper Ter 1969) and through the Guaj ira Peninsula as the tiary and Holocene volcanic rocks that surmount the Guajira Complex (Alvarez, 1967). These plutons southern Central Cordillera. appear to be situated along the extreme edge of the At least 45 Tertiary to Holocene volcanic centers underlying Precambrian platform (fig. 2). Triassic- have been recognized along the summit of the Cen ! Jurassic plutons underlie a wide belt that includes tral Cordillera between Manizales (pl. 1) and the I the Eastern CordiUera, the e~astern side of the Cen Ecuadorian border. Severa] centers are more than tral Cordillera, the Sierra Nevada de Santa Marta, 15,000 feet in altitude, and the highest, El Nevada and perhaps the Guajira Peninsula; they are clearly de Ruiz, reaches 17,700 feet. The present altitude of int.racratonic. the·se volcanic centers is due in part to late Tertiary Cretaoeous plutons, on the other hand, are mainly and Holocene uplift, which in some areas may have along the axis of the Central Cordillera; hypabyssal been as much as 6,000 feet. Because volcanic detritus rocks related to these plutons crop out over small is prominent in the upp.er Tertiary beds of both the areas in the Sierra Nevada de Santa Marta. Cauca and Upper Magdalena Basins, on both sides Lower to middle Tertiary granitic intrusive rocks of the Central Cordille·~a, volcanism probably began are clearly related to the outermost, oceanward, fold in the Miocene and has continued almost to the pres belt. ent. Although no detailed petrographic studies are This preliminary attempt to distinguish magmatic available, the rocks appear to be mainly of inter provinces could be significant in distinguishing met mediate composition. allogenic provinces. The upper Tertiary and Holocene volcanic centers are in a well-defined line along the summit of the GEOLOGIC STRUCTURE Central Cordillera. Volcanism may be localized along FOLDS IN METAMORPHIC TERRANES a rift zone that extends deeply into the crust. Folding has been intense in many metamorphic terranes in the Colombian Andes. The extremely AGE PROVINCES OF GRANITIC INTRUSIVE ROCKS thick section, greater than 30,000 feet, of Precam The granitic intrusive rocks, when plotted by age brian granulites (Los Mangos Granulite Series) on groups, fall into fairly definjte linear patterns (fig. the southeast side of the Sierra Nevada de Santa 8). The oldest intrusive rocks are in the shield area, Marta probably represents tight isoclinal folding of and the Ordovician and Permian to Lower Triassic sediments at shallow depth or during metamorphism intrusive rocks are arranged sequentially from older after their depression to depths of 20 km or more to younger toward the oceanic basins. The Triassic within the crust. The amphibolite-grade Bucara Jurassic, Cretaceous, and Tertiary intrusive rocks manga Gneiss, P·robably also Precambrian, may not are also sequentially arranged from older to younger have been buried as deep as the granulities, but toward the ocean basins, but the Triassic-Jurassic kneading structures are common. intrusive belt overlaps the Ordovician belt, and the Detailed mapping also shows folding in metamor Permian to Lower Triassic intrusive belt is between phosed Paleozoic rocks such as the Silgara Schist the Cretaceous and Tertiary belts. (Cambrian and Ordovician) in the Santander massif Precambrian intrusive rocks are associated with northeast of . Buoaramanga and in the Caj amarca the Guayana shield; none have yet been identified in and equivalent Groups ( upp·er Paleozoic) of the the Andean Cordillera. Upper Ordovician granitic Central Cordillera; folding in the Quetame Series rocks crop out in the Santander massif and on the (probably Cambrian .and Ordovician) southwest of Guaviare River (figs. 1, 2, and 8) some distance Bogota is severe. The greenschist adjoining the Santa east of the Serrania de Macarena, forming a north Marta batholith and the Etpana and Jarara Forma trending belt well within the Precambrian platform tions (Cretaceous) along the northwest side of the area; they are therefore intracratonic. A belt of Guajira Peninsula are moderately to intensely GEOLOGIC STRUCTURE 27 folded. All Phanerozoic deformation was accom cate that much deformation must have been pro plished under comparatively light load, as m·eta duced under compression. morphic mineraLs are mainly of the low .... pressure type. The strongly folded and faulted thick M.esozoic HIGH-ANGLE REVERSE FAULTS s·edimentary and volcanic rocks of the Western Cor: dHlera generally show only incipient metamorphism. Reverse faults in Colombia are being recognized with increasing frequency as geologic mapping is FOLDS IN UNMETAMORPHOSED TERRANES accomplished at larger scale and as field ,techniques improve. The Salinas fault (pl. 1; fig. 9) along the In nonmetamorphic terranes, extraordinarily east ·S·ide of the Middle Magdalena Basin forms the thick pris.ms of sedimentary rocks, such as in the east boundary of the T.ertiary sedim·entary .basin ; Simi Fold Belt (fig. 1), along the central part of the the Salinas was first recognized as a reverse fault Eastern Cordillera, and in the Western Cordillera, by Taborda (1965). The fault has been traced con are notably folded. In the Sinu Fold Belt, Tertiary tinuous1y for about 100 miles, and displacements are strata are as much as 30,000 feet thick (pl. 1). In large. Middle and Up.per Cretaceous strata east of the central p·art of the Eastern Cordillera northeast the fault are in juxtaposition with upper Tertiary of Bogota, the 50,000-foot sequence consists of as strata west of the f,ault. The opposing terranes indi much as 40,000 feet of Cretaceous strata and rem cate a throw of at leasf10,000 feet. nant synclinal troughs of lower Tertiary beds that On the Guajira Peninsula, MacDonald (1964) may have been as much as 10,000 feet thick before and Lockwood ( 1965) found that displacem.ent along Andean folding (McLaughlin and Arce, 1969). two major east-trending thrust faults, the Ororio North and northeast of Bogota, harmonic concen and Iituj uru, has brought phyllite and quartzite of tric folds of great length are the rule ; where salt the deep-wate·r Etpana Formation of Cretaceous deposits are locally interstratifi-ed, the f.olds become age over the coeval shallow-water Jarara Forma sharply disharmoni·c. In this area many folds are tion. The fault surface dips 45° to 65° N. Twelve associated with high-angle thrust faults. In the miles to the south, a regional thrust fault, the Alas, Western CordiUera, as revealed in recent mapping .brings hornblende gneis1s of the Macuira Formation by lngeominas, the enormous sections of the Meso (Paleozoic?) over low-grade metasedimentary rocks, zoic volcanic ("Diabase Group") and sedimentary some of which are Lower Cretaceous. The Alas fault (for example, Cafiasgordas Group) rocks are in dips 10° to 45° N. and locally is overlain uncon tensely deformed. formably by middle Terti·ary limestone. The Urait In the intermontane T~ertiary ·sedini·enbary basins chlpa fault in the southern part of the Macuira area and in the Llanos Basin (fig. 1) east of the Eastern differs from the Ororio, Iitujuru, and Alas faults in Go:rdillera, folding is much le:Ss intense, even though that it dips moderately to the south. MacDonald considerable thicknesses of strata (as much as (1965) and Lockwood (1965) generally considered 25,000 ft) are involved. However, adjacent to the the rocks to have been overthrust fro.m the north, cordilleran front in areas of high-angle revers.e probably during the Late .Cretaceous-early Tertiary faulting (pl. 2), folds are more com.pressed and orogeny. In the Simarua area to the west, Alvarez locally may be overturned. (1967) noted overthrusting from the north on the Where oom.paratively thin sedimentary sequences Kasipoch and Santa Ana faults. The thrust faults overlie competent cratonic Dla.tform rocks. s·ome of in turn are now offset by many northwest-trending the deformation of strata resulted from differential normal faults of late Tertiary age, which produced vertical mov.ements of cratonic basement blocks much of the present relief of the area. along fault surfaces; that is, faults generated below The southweste·rn edge of the Maracaibo Basin were translated into flexures and drape folds above. (fig. 1) is delimited by thrusting of p.re-Devonian Stibane (1967) and othe,rs considered this type of metamorphic and igneous rocks over Cretaceous .and vertical movement to be the p~edominate cause of Tertiary form~ations (s.ee geologic quadrangle maps the structures in t:he r.egion. Viewed in a broad way, F-13 and G-13, Colombia lngeominas). The Mer howeve~r, certainly the moderate to intense folding cedes thrus·t fault (pl. 1; fig. 9) i:s interpreted to in the Sinu Fold Belt and Eastern and Western Cor dip westward beneath the Eastern Co,rdillera. Folds dilleras, together with the high-angle ~reverse faults in the basin to the east, however, are overturned along the margins of many of the cordilleras, indi- both to the east and west. 28 NORTHERNMOST ANDES, COLOMBIA EXPLANATION CARIBBEAN SEA Ensimatic foreland Mesozoic eugeosyncline Exposed edge of Paleozoic eugeosyncline Phanerozoic miogeosynclinal platform Area of Paleozoic metamorphism Area of Late Cretaceous-early Tertiary metamorphism --+---t•~ Andean anticlinorium axis Axis of Andean basin, plunge ~venwhereknown ~~~~~~~~~~L-~r---~----~--~~~------~ Overturned axis of u asymmetric Andean basin 50 0 50 100 150 KILOMETRES I I I I I I I I 50 0 50 100 MILES FIGURE 9.-Principal tectonic elements of northernmost Andes, Colombia. GEOLOGIC STRUCTURE 29 The most notable high-angle reverse faults appear STRIKE-SLIP FAULTS to be those ·along the ea·stern margin of the Eastern Santa Jfarta-Bucaramanga fault.-Rod (1956) Cordillera, adjoining the deeply filled Tertiary basins and Raasveldt ( 1956) simultaneously argued for the of the eastern great pl•ains ·(Llanos Basin). Mapping probability of strike-slip faulting in Venezuela and and study of aerial photographs show that Paleozoic Colombia. More; recently, Campbell (1965) adduced and· Cretaceous strata are thrust over steeply dip oodLtional :generalized evidence for wrench move ping and locally overturned Cretaceous and Tertiary m·ent along the Santa Marta-Bucaramanga fault. He strata of the basin. The fault pattern is not simple, pointed out the general similarity and attitudes of and in many places throw is distributed among sev the Cretaceous and Tertiary strata of the Middle eral parallel faults, as it is along the Santa Marfa, Magdalena and Gesar Basins (fig. 9) and suggested Yopal, and Guaicaoomo at the latitude of Bogota that the two basins were once united and were dis (pl. 1). The faults apparently dip at high angles to placed by le.ft .. lateral movement during late Tertiary the west, toward the cordillera. and Quaternary time. Displacement may have been Structure profiles of the Tertiary and Cretaceous as much as 65 miles. Polson and Henao (1960) ar across the Eastern Cordillera and into the eastern gued that there is little evidence for wrench move Llanos Basin indicate vertical displacements of ment along the fault; in fact they believed that the several miles (pl. 2). Because low.er and middle Ter Santa Marta and Bucaramanga faults are separate tiary strata are involved, it is clear that the thrust structures. Tschanz concluded (unpub. data, 1969) ing is post-middle Tertiary and probably was re that major left-lateral displacement, similar to that l·ated to the Andean orogeny. The extraordinary topo postulated by Campbell, took place after late Meso graphic relief along the cordillera front, much of it zoic-early Tertiary metamorphism, but that the carved in soft rocks, indicates that deformation may present altitude of the Sierra Nevada de Santa have continued to a comparatively recent date. This Marta block w·as achieved mainly by vertical dis interpretation is supported by the strong earthquake placement in late Tertiary time. activity in the region and by many terraces at vari The following observations bear on the location ous el·evations along rive·rs draining the Cordillera. and scale of wrench faulting along the Santa Marta McLaughlin and Arce (1972) mapped many high Bucaramanga fault: angle reverse strike faults in the high savanna north 1. The Sierra Nevada de Santa Marta crystalline of Bogota. Thes9 faults ·are predominantly parallel complex, which includes the oldest known to the axes of folds in Cretaceous and Tertiary rocks, rocks in Colombia (1,350 m.y.), forms a block and most dip toward the axial planes of the folds; that juts abnormally northward upon the the folds thus appear to have been broken by dis Caribbean coastline, intercepting much young tension of overturned limbs. er sedimentary deposits of adjoining areas High-angle reverse faults have been mapped in along the coast. Miocene beds adjoining it on the Cauca Basin in the vicinity of Cali (Schwinn, the west have extremely low sand-shale ratios, 19€·9). The Cauca Basin between the Central and indicating either that the mountain mass was Western Cordillera (fig. 1) was long considered to low during deposition of the Miocene sedi be a graben. Mapping ·by geologists of the Interna ments or that the mountain mass was trans tional Petroleum Company, however, ·shows that ported to its p.resent position rel~tive tQ the intrahasin faults are reverse faults and that the Miocene beds by many miles of left-lateral marginal faults are high-angle reverse faults, which strike-slip movement. dip beneath the adjoining Western and Central Cor 2. The Santa Marta-Bucaramanga fault, nearly 360 diHera, respectively. Recent mapping of the Romeral miles long, is remarkably straight. Although fault from A:r:anzazu southward (Dario Bar,rero L., much of its trace in the north is beneath al written commun., 1970), indicates that it dips 50° luvium, it has strong topographic expression to 70° E., so thrusting from the east is evident (pl. from the Cesar Basin southward. 2). The attitude of this western bounding fault of 3. The f·ault maintains ·a fairly constant N. 15° W. the Central Cordillera, combined wi.th the gentle strike throughout its length and in the Sierra eastward slope of the old land surface of the Central Nevada de Santa Marta intersects Precambri Cordillera toward the Middle Magdalena Basin, sug an .basement structure·s at small to large angles·; gests that the Central Cordillera block has ridden only in the southern part does· its trace coin upward toward the west. cide with Jurassic and pre-Jurassic structural 30 NORTHERNMOST ANDES, COLOMBIA grain. The structure, moreover, is little af strata southward in the Guajira Basin toward the fected by the strong northeast-striking faults fault (pl. 1), as if depres.sion took place contempo in the Sierra Nevada de Santa Marta, in the raneously with basin filling. Simila·r filling and de basement rocks of the Santander Departments, pression farther to the east led to the truncation and and in the Tertiary strata of the Middle Mag burial of the extreme north end of the Serrania de dalena Basin. Perija. Many authors have suggested right-lateral 4. Basement-rock formations are poorly known movement on the fault, but few have presented con along the west side of the Santa Marta-Bucara crete evidence to support this contention. Tschanz manga fault in its northern segm,ent, but some (written commun., 1969) believes that schist from metamorphic rocks of the Sierra Nevada de the Perico well might be correlated with the Ta- Santa Marta are similar to those of the north ganga Group on the northwest corner of the Sierra ern end of the Central Cordillera. The Nevada de Santa Marta; if so, horizontal displace Sierra Nevada de Santa Marta rocks may ment, depending upon effects of erosion on respec have been displaced en masse northward from tive sides of the Oca fault, has been as much as 40 a former southerly position. Metamorphic miles. Feo-Codecido ( 1970), on the basis of a sub rocks in the Algar:robo No. 7 well drilled by crop geologic map drawn from well data at the base the Superior Oil Company, near the San Angel of post-Eocene sedimentary rocks in westernmost No. 2 · well (Tschanz and others, 1969), con Venezuel:a, concluded that right-lateral displacement sist of huge blocks of phyllite very similar on the Oca fault may have been as much as 12 miles. petrographically to that of the Taganga Group Cuisa fault.-Approximately 50 miles north of and (Cretaceous) or San Lorenzo Schist of the nearly parallel to the Oca fault is the Cuisa fault of extr~me northwest oorner of the Sierra N e the Guajira Peninsula. Alvarez (1967), who mapped vada de Santa Marta. Furthermore, the south its western part, thought that possibly there had flanking Cretaceous limestone and Triassic• been right-lateral displacement of as much as 15 Jurassic volcanic rocks in the Sierra Nevada miles, on the basis of the offset of phyllite-gneiss de Santa Marta may have been displaced and gneiss-sedimentary rock contacts .. Because the northward from similar rocks near Morro Cuisa and Oca faults are nearly parallel to one an coyal. other, displacement similar to that of the Oca fault If such left-lateral displacement has occur may be inferred on the Cuisa. Continuation of the red, amounting to 65 miles, as suggested by Cuisa fault along its western projection below sea Campbell ( 1965), then the structural grain of level is said to be clearly recognizable in offshore the basement rocks on each side of the fault seismic records made for petroleum companies. is restored to approximate coincidence across Otu fault.-The Otu f·ault strikes N. 15° W. and the faulted area. The grain of the rocks in the has been traced for nearly 75 miles from Zaragoza western Sierra Nevada de Santa Marta, ac southward to a point near Puerto Berrio. At each cording to this interpretation, represents part extremity the fault trace is covered by Tertiary of a curving regional grain that has been sedim·entary rocks or Holocene alluvium· (pl. 1, fig. laterally offset. 9). Distinctive intrusive relations between diorite. Oca fault.-The north side of the Sierra Nevada and quartz-rich metamorphic rocks on opposite sides de Santa Marta is bounded by the east-west Oca of the fault are interpreted by Feininger (Feininger fault zone, which passes eastward into the northern and others, 1973) to indicate left-lateral disp,lace part of the Maracaibo Basin of Venezuela (p.I. 1, fig. ment of as much as 30 miles. The Otu fault has cut 9). Recent mapping by Tschanz, Jimeno V., and other faults that displace Cretaceous shale contain Cruz B. ( 1969) has shown that the western segment ing Aptian-Albian fossils; hence, the Otu is post of the fault is not a single structure, but one that Albian, and principal displacement is probably post has split into several subparallel splays, along which middle Maestrichtian. By reconstruction of move large vertical displacement associated with the up ments on the Otu and associated faults, Feininger's lift of the Sierra Nevada de Santa Marta has proba interpretation is that the Precambrian block with bly been distributed. Eastward, in the Departm·ent its overlying Ordovician shale near Cristalina was of Guajira and in Venezuela, the fault is a single transported into the area from a point 35 miles east structure. Isopachs of the Cenozoic strata north of southeast. the fault show pronounced thickening of Cenozoic Projecting the Otu fault no·rthward beneath the GEOLOGIC STRUCTURE 31 Tertiary strata, one notes that Cenozoic strata east northwest-trending fold axes in Tertiary beds east of the fault are thin, whereas Cenozoic strata west of the Gulf of Uraba swing north in the area of the of the fault attain great apparent thickness (pl. 1). presumed northerly extension of the fault, and Because the Otu fault is approximately parallel to appear to cross the direction of thickening of the the Santa Marta-Bucaram.anga fault and displace Tertiary rocks. Elsewhere in the Sinu Fold Belt and ment on both appears to be left lateral, the two struc in the Lower Magdalena Basin (pl. 1), fold axes tures are considered to be related to similar tectonic trend northeast. These relations mildly suggest that forces. the fault has been under compression and that left Palestina fault.-The Palestina fault (Feininger, lateral movement may have taken place along it. 1970) trends about N. 15° E. and can be traced for nearly 200 miles along the east side of the Central INTERIOR BASINS Cordillera (pl. 1, fig. 9). Right-lateral -strike-slip During early Tertiary time a large basin existed movement has been well documented (Feininger, east of the Central Cordillera and was probably 1970). The Otu fault has been displaced 17.2 miles originally coextensive with the Barinas Basin south by the Palestina, and earliest movement m·ay pre of the present Merida Andes of Venezuela (fig. 7). date the Upper Cretaceous Antioquian batholith. During the Andean orogeny it underwent taphro The Jetudo and Mulato faults to the south appear to genesis. Wellman (1970) in his study of the Honda be horsetail splays of the Palestina fault; Feininger Group (Miocene) of the Upper Magdalena Basin, inferred that right-lateral displacement has also oc concluded that its sediments were deposited by curred on these two faults, collaterally with Pales a:treams flowing eastward from the Central Cordil tina movement, although in amounts of only 7 and lera. Howe ( 1969) has also shown that paleocurrents 10 miles, respectively. during deposition of the overlying N eiva Formation Cimitarra fault.-The Cimitarra fault extends to (probably lower Pliocene), lowest unit of the Mesa the Pale·stina fault from the Barrancabermej a area Group, were also predominantly eastward. At some to the northeast (pl. 1). Because of its strong topo later tim.e, the eastward-flowing streams were evi graphic expression, and because it cuts Miocene and dently intercepted by uplift of the Eastern Cordil younger formations in the Middle Magdalena Basin, lera acros~s their path and were turned to their pres it is considered to be the youngest major fault in ent northward course. the area. It can be traced fo,r almost 100 miles on the No paleocurrent studies have been made of the surface and in the subsurface. Feininger ( 1970) was Middle Magdalena Basin area. The Honda Group of unable to ascertain the nature of displac·ement upon the Upper Magdalena Basin passes into and is proba it, but inferred that it is a wrench fault. bly correlative with the thick, coarse clastic Real Romeral fault.-A major north-south fault now Formation of the Middle Magdalena Basin. The called the Romeral fault has been traced for several overlying Mesa Group is common to both basins. hundred miles. No.rth of latitude 7° N., it has a The Real Formation in turn is approximately cor northe·asterly course (pl. 1). Its topographic expres relative with the Guayabo Formation of the south sion is much clearer than that of the Otu fault zone, westernmost Maracaibo Basin in the vicinity of which suggests that it is younger than the Otu. Cucnta (pl. 1). Uplift of the Eastern Cordillera simi Thus, the Romeral fault probably transects the Otu larly may have separated this part of the former fault beneath the Tertiary cover to the north. To the coextensive basin into the present smaller basins. south, the Romeral fault dips 50°-70° E. at various Van der Hammen (written commun., 1969) has points along its trace (Dario Barrero L., oral com shown that the base of the little-deformed Tilata mun., 1970), and metamorphic rocks of the Central Formation (upper Pliocene) of the Eastern Cordil Cordillera thrust over continental Tertiary strata lera contains humid tropical pollen and that upward and Cretaceous volcanic rocks. In its northeast in the section, the Tilata contains pollen of flora of trending northern segment, the fault intercepts geo progressively cooler climates. This observation sug logic formations in a manner suggesting right gests that much Andean folding took place at com lateral movement (Alvarez and others, 1970). paratively low altitudes, for the Tilata was deposited A trato fault.-A recently recognized north-trend across the eroded edges of folded older Tertiary for ing line·am,ent, the Atrato fault, appears to form the mations. It is ·Concluded, therefore, that the Upper western boundary of the Western Cordillera (pl. 1; and Middle Magdalena Basins had achieved their fig. 9). Its trace is remarkably linear. Generally depressed positions and the beds therein were folded 32 NORTHERNMOST ANDES, COLOMBIA before uplift of the Eastern Cordillera along its mar- · were deposited apparently as a littoral wedge ad ginal high-angle reverse faults. Thus, the thick jacent to the Western Cordillera. The northern part lower Tertiary section in the Magdalena Basins of the wedge underlying the Atrato River is syn seems to have resulted 'from compres·sion in associa clinal, whereas the southern part-for example, tion with reverse faulting along the basin margins, south of BuenaventurB.-slopes oceanward toward and not, as long interpreted, from infilling of a the continental platform as a simple homocline. The graben. Tertiary strata thicken oceanward as indicated by Folding of the Tertiary strata within the present offsho~e drilling. As indicated above, data on the Upper and Middle Magdalena Basins; the south structural and stratigraphic relation of these strata westernmost Maracaibo Basin, and along the west to those within the Cauca Basin are insufficient for ern margin of the Llanos Basin, is generally less drawing conclusions at this time. Possibly prior to intense than that ·Of the Tertiary strata within the the Andean orogeny (Miocene) the presenrt ·two E·aster.n Cordillera. This fact suggests that the rocks ba!Sin.s were coextensive, nonmarine landward and underlying the cordillera were less competent than marine seaward, and constituted part of what Ny those in the adjoining basins. gren (1950) referred to as the Bolivar geosyncline. Data on Tertiary structural history· of the Cauca Basin, on the other hand, is limited, and little can ISTHMUS OF PANAMA be said about the relation of Tertiary strata of that The bifurcation of the Isthmus ·of Panama· from ba.c;in to Tertiary strata of the Pacific Coastal Basin the South Am,erican continent is not well understood. to the west. Moderately thick s~ections of nonmarine The isthmus, as shown by bathymetric maps, forms beds within the Cauca .Basin are folded and thrust an elevated narrow ridge upon a much broader sub faulted iri a manner comparable with their analogs marine platform whose margins break sharply into in the Upper and Middle Magdalena Basins; both the Caribbean Basin northeastward and into the the eastern and western margins of the Cauca Basin Pacific Basin .southwestward. The exposed part of are delimited by high-angle reverse f.aults (pl. 2). the ridge is synclinal and its axis veers southward The similarity of the structural style of. both these into the Atrato :synclinorium west of the Western longitudinal intermontane basins is remarkable, but Cordillera (fig. 9). A side-looking radar map of the detailed study is required before well-based conclu area. (Raytheon Company, written commun., 1969) sions on their similarity can be reached. shows an extraordinary rift zone, here referred to as the Atrat.o fault (pl. 1; fig. 9), along the easte·rn COASTAL WEDGES margin of the Atrato River valley and at the west Tertiary strata of the Simi Fold Belt and Lower ern margin of the Western Cordillera. The fault Magdalena Basin (fig. 1) thicken northward from enends for several hund,red kilometers south from the overlap on the pre-Tertiary rocks of the Western the Gulf of U raba. and Central Cordilleras and appear to reach maxi Gravim·ertric profiles across the Pacific Coast Hills mum thicknesses along a northeast-trending axis near the Colombia-Panama border (Case and others, approximately parallel to, and slightly southeast of, 1969) show extremely high Bouguer gravity anoma the Caribbean coastline. The Tertiary reaches a lies. Because of the m·afic composition of the base thickness of 30,000 feet near the town of Monteria ment rocks and the excessively high anomalies, Case (pl. 1). Along the coast the ,strata are tightly folded, interpreted the underlying rocks of the area to be but southeastward toward the interior they are only oceanic crust. gently flexed. The sharp difference in structural style In his paleontological ·studies of faunas from rocks in the two areas may be the result of contrasting along Routes 17 (eastern Panama) and 25 (north thickness of sections, but a part may be due to differ western Colombia), for the Interoceanic Canal Com ences in the nature and competence of the basement mission, Bandy ( 1968) confirmed the mafic composi rocks, ·as suggested by Zimmerle (1968). The folded tion of the basem.ent rocks and stated that the oldest coastal sedimentary belt appears to overlie the Meso faunas found are of Late Cretaceous age. The Upper zoic eugeosynclinal rocks, whereas the little Cretaceous and lowermos,t Tertiary strata contain deformed interior sedimentary beds probably overlie -abyssal to bathyal faunas in contrast to the shallow crystalline Paleozoic and Precambrian rocks (fig. water forms in upper Tertiary strata. The data tend 9). to .suggest that the isthmus belongs to an oceanic The Tertiary strata of the Pacific Coast Basin geologic province that formed separateiy from the STRUCTURAL EVOLUTION 33 Andes and became connected to the Andes during Guayana shield, and in part are underlain by shield the Andean orogeny (Miocene). rocks. The outermost rocks of the Guayana shield are GEOLOGIC CROSS SECTIONS clearly younger than those of the central shield. The oldest radiogenic ages for rocks in Colombia Geologic cross sections across the northernmost range from 1,400 m.y. to 1,300 m.y. Younger ages Colombian Andes drawn at parallels of latitude of 950 m.y. and 700 m.y. may represent late Pre 5° and 7° N. are shown on plate 2. At the present cambrian disturbances which reset isotopic clocks stage of mapping of Colombia, these parallels of of older rocks, or indeed may also represent late latitude have the best geologic control; even so, Precambrian cycles of sedimentation, metamor control for the western parts of the cross sections phis·m, and igneous intrusion. The structural grain is poor. of these outermost shield rocks appears to be north The cross sections illustrate the tripartite geologic northeast in Colombia, but in the Sierra Nevada de subdivisions of the Colom-bian Andes. The Eastern Santa Marta the grain swings northeast. In the Cordillera is composed mainly of Mesozoic and Pale Guajira Peninsula, it is east-northeast, and from ozoic rocks overlying Precambrian basement rocks; there it swings eastward into northern Venezuela. the Cordillera i:s elevated along high-angle reverse The outermost Precambrian shield rocks in Colom faults or sharp marginal flexures. The Central Cor bia are highly metamorphosed and range from bio dillera is composed predominantly of metamor tite schist through amphibolite to rocks of the phosed Paleozoic strata that have been intruded by granulite facies, similar to those of the central small upper Paleozoic-Lower Triassic plutons and shield. by large upper Mesozoic plutons. And finally, the The long span of geologic time recorded by radio Western Cordillera consists almost exclusively of genic ages in the Precambrian terranes, as com thick sections of folded and faulted upper Meso pared with that in the Phanerozoic terranes (which zoic eugeosynclinal sedimentary and volcanic rocks are so much better known), admits the possibility intruded by middle Tertiary pi utons, forming a belt that several as-yet-unrecognized cycles of sedimen oceanward and alongside the metamorphosed rocks tation, metamorphism, and plutonic intrusion may of the Central Cordillera. have taken place in this area near the margin of the The approximate positions of orogenic belts and Precambrian continent where the sialic crust has of plutonic rocks, with radiometric ages where undoubtedly interacted with the oceanic crust. De known, are indicated on the sections (pl. 2). tailed mapping and additional radiogenic deter minations are needed to unravel the detailed his STRUCTURAL EVOLUTION tory of these outermost Precambrian terranes in PRECAMBRIAN Colombia. During Precambrian time the Guayana shield of PALEOZOIC northern South America (fig. 2) acquired cratonic During the Paleozoic Era, epic0111tinental and characteristics during the Akawaian episode (Guy miogeosyntClinal seas transgressed upon the Pre .anese or 'rransamazonas igneous cycle) about 2,000 cambrian shield platform on various occasions. m.y. ago. This event is established by the fact that During Cambrian and Ordovician time (fig. 3), the widespread overlying sedimentary Roraima For fossiliferous clastic strata were deposited over much mation, intruded by mafic sills dated at 1, 700 m.y., of the area of the present Eastern Cordillera, and is little disrupted. From its broad exposed area in according :to present information as far east as the eastern part of the continent, the shield surface longitude 72° W. in central Colombia. Graphite con descends gently northward toward the Venezuelan tent in these sedim.entary rocks increases westward, Andes and westward toward the Colombian Andes indicating that the seas deepened westward. In and passes beneath an extensive cover of younger Late Ordovician time the sedimentary r 450 m.y. old. Small peralkalic syenite bodies near . shale, graywacke, impure to pure sandstone, and San J osa de Guaviare intrude Precambrian rocks included a prominent limestone member. These and are approximately 460 m.y. old. Metamorphism rocks, which were also deposited upon Precambrian in the Cambrian and Ordovician rocks decreases basement rocks, as indicated by Precambrian out in intensity to the north and south along the oro crops in the area, are now regionally metamor genic axis, and in the extreme north and south phos.ed (fig. 4) and range from greenschist to high the sedimentary rocks are little metamorphosed. amphibolite facies. In northern Antioquia Depart As Precambrian rocks crop out extensively in the ment, the rocks may have approached temperatures Central Cordillera west of this orogenic axis, fold of fusion and are now represented by migmatites ing and igneous intrusion in this orogen were and anatectites ( ?) of the Puqui Metatonalite. clearly intracratonic. Uplift associated with the Along the west flank of the Central Cordillera, orogeny prevented reentry of seas during the Silu mafic volcanic material associated with the .sedi rian, and no rocks of Silurian age have been found mentary rocks is converted to greenstone, chlorite in Colombia, although C. Martin-Bellizzia (oral schist, biotite-hornblende schist, and amphibolite. commun., 1970) informed me that Silurian faunas Here, however, no Precambrian bas·ement rocks are present. locally in Venezuela. have been identified. Fossiliferous Devonian strata (fig. 4) are widely This distribution o.f Paleozoic and Precambrian distributed over approximately the same area as rock types suggests that conditions of deposition the Cambrian and Ordovician strata and uncon a:long the east side of the present Central Cordillera formably overlie these older rocks. East of Bu were miogeosynclinal to epicontinental upon the sia caramanga (pl. 1), rocks equivalent to the Floresta lic Precambrian continental platform, whereas con Formation (Devonian) are strongly folded and ditions along the west side of the cordillera were metamorphos·ed to low greenschist facies. Lower eug.eosynclinal upon lsimatic oceanic crust adjoining Carboniferous (Mississippian) rocks are poorly rep the Precambrian continental platform. Judging resented. Thus, it is concluded that a sharp dis from the structural grain and distribu~ion of meta turbance in Late Devonian or early Carboniferous morphic rock types, the Paleozoic rniogeosynclinal time was localized approximately over the axis of eugeosynclinal couple appears to have extended the preceding Late Ordovician orogeny and caused northward, curving northeastward through the a general retreat of seas from much of Colombia. Sevilla arc in the Sierra Nevada de Santa Marta, No Upper Devonian or Mississippian igneous rocks. and possibly continued east-northeastward through associated with this disturbance have yet been iden the Guajira arc on the Guajira Peninsula~ tified. A profound late Paleozoic orogeny converted the Unmetamorphosed fossil-hearing Pennsylvanian Paleozoic miogeosynclinal rocks and the adjoining and Permian strata-very thick sections in some eugeosynclinal sedimentary rocks to metamorphic areas-are found in scattered outcrops over much rocks o.f low to high rank. The rocks were intruded the same area as the Cambrian-Ordovician and by plutons that have app.arent ages of 250 to 240 Devonian strata and overlie all older rocks with m.y. This orogeny is regarded as most significant angular unconformity. No important stratigraphic because it gave rise to the ancestral Central Cor bre·ak or unconformity, however, is noted at the dillera. It is certainly the most severe orogeny ex top of the Permian; in the Bucaramanga area the perienced in Colombia during Phanerozoic time. Permian Tiburon beds pass upward into the paralic The total width of the orogen is unknown because Bocas Formation of Triassic age with little dis deposits of younger rocks overlie it along its west cordance. Triassic strata, however, are of limited· and north sides. In addition, it passes out to sea distribution, and it is concluded that there was a to the north and northeast beneath the present general withdrawal of seas from the platform area Caribbean Basin. The now-crystalline rocks of the at the close of the Paleozoic Era. orogen appear to have added a fringe of unknown The Paleozoic record of the area to the west is width to the Precambrian continental platform, and less clear because sedimentary rocks probably equiv it is concluded that some continental accretion took alent to those deposited upon the Precambrian plat place at this time (figs. 9, 10). form are severely metamorphosed. Along the east MESOZOIC ern flank of the pres·ent Central Cordillera the During the Mesozoic Era, sedimentation upon the original Paleozoic sedimentary rocks consisted of continental platform east of the ancestral Central STRUCTURAL EVOLUTION 35 0 r.....0 °. 0 ••• 11111111 1 I~ 0 ~ 0 ~I EJ~l~~lll~!ILI Miogeosynclinal Epicontinental Paralic facies Continental facies facies facies facies WESTERN CENTRAL EASTERN EASTERN PLAINS PRINCIPAL ERA CORDILLERA CORDILLERA CORDILLERA OR OROGENIC REGION REGION REGION LLANOS BASIN EPISODE ANDEAN OROGENY CENOZOIC SANTA MARTA GUAJIRA OROGENY WF.STERN CORDILLERA AND ANTIOQUIAN OROGENIES MESOZOIC ANTANDER-SANTA MART OROGENY t------1~~~~~:!!!;~~;;::;:;;:;::;:;;:;;;::;;:;:;;:;::;::;:;;::;:;~:;;:;:;:~~~:;:;;:;::;tr~TTJr.-:-:-:-::;;,------, CENTRAL CORDILLERA OROGENY PALEOZOIC LATE DEVONIAN OR CARBONIFEROUS DISTURBANCE 1------l~------4------.~.....:..~--~~--,,.o...,l-lo..l.l..i..... ""-'..l¥------,.....-----l ORDOVICIAN OROGENY PRECAMBRIAN OROGEN OF 950moyo (Amphibolite and lower metamorphic facies) PRECAMBRIAN PRECAMBRIAN OROGENY OF Oceanic Oceanic? Shield? Shield? Shield I 1350moyo (Amphibolite and granulite metamorphic facies) FIGURE 10.-Progressive westward shifts of eugeosynclinal axes and resulting continental accretion, northernmost Andes, Colombia. · Cordillera was again miogeosynclinal. . Marine in temporaneous in the Santander massif and the Si cursions were limited during Triassic time, but erra Nevada de Santa Marta, two widely separated expanded somewhat in Jurassic time (fig. 5). Par areas, and began 200 m.y. ago. In the Sierra Nevada ticularly noteworthy during the Triassic was the de Santa Marta, it reached a culmination at about advent and increasing tempo of volcanism in the 175 m.y. In the Central Cordillera, however, it Si,erra Nevada de Santa Marta where abundant c-ontinued to 143 m.y. ago. Uplift accompanying spilites and keratophyres of Triassic age are found. igneous intrusion in the Santander region gave rise Triassic-Jurassic volcanic and volcanogene sedimen to the widesp·read m·olassic red beds of the Giron tary rocks are widely distributed on the Guajira Group (Jurnssic). Peninsula, in the northern East.ern Cordillera, and The lower basaltic volcanic rocks of the Dagua along the east side of the Central Cordillera. Group, which is to the west of the ancestral Central Jurassic and Cretaceous volcanic rocks range Cordillera, a;re considered to represent early mani from andesite through dacite and latite to rhyolite festations of an extensive Mesozoic eugeosyncline· in lesser amounts. What triggered this widespread that dev,eloped oceanward from the anceatral Cen volcanis.m is not clear. Volcanism apparently pre tral Cordillera. West of Cali, Hubach and Alvarado ceded, accom·panied, and postdated the intrusion of (1934) and Nelson (1957) mapped mafic volcanic several batholiths in the Sierra N eva.da de Santa and sedimentary rocks of the Dagua Group beneath Marta. In the S~antander m~assif (fig. 2) similar a very thick mafic volcanic s.equence ("Diabase batholiths were intruded during the same time in Group") that is considered by most authors as terval but apparently were accompanied by consid Cretaceous. The Dagua Group rocks could repre erably less volcanism. Batholithic intrusion was con- sent Jurassic deposition in view of the extraordinary 36 NORTHERNMOST ANDES, COLOMBIA thicknes.s of the overlying mafic volcanic sequence. and its analogs a1ong the northeast coastal region In the absence .of fossils, the lower part of the of Colombia. In middle Maestrichtian time, the Dagua Group is here considered Jurassic until ra great Antioquian batholith and its satellites (age diogenic dating of the complete volcanic section de 70 to 80 .m.y.) w·ere emplaced along the inner side termines otherwise. No rocks representing the Tri of the orogenic arc (fig. 6). Contact metamorphism assic Period have been recognized west of the is obs·erved in rocks immediately adjoining the in Central Cordillera. trusive rocks, and resetting of isotopic ratios seem.s In Late Jurassic time (Tithonian), transgressing to have been widespread. Only incipient metamor marine seas in the Guaj ira Peninsula and northeast phis.m is evident in the rocks of the Western Cor of Bogota began the infilling of an extremely broad dillera, but in the northwestern Sierra Nevada de Cretaceous miogeosyncline that occupied the con Santa Marta and Guaj ira Peninsula, metamor tinental platform east of the ancestral Central Cor phism locally reached the lower amphibolite facies. dillera (fig. 6). Sedimentation was variable in re This orogeny is significant, for it gave rise to the sponse to irregular rates of subsidence and to local Western Cordillera as ·an outer parallel counterpart diastrophism. Along an axis passing north-northeast 'to the ancestral Centml Cordillera. This range through Bogota, as much as 40,000 feet of clastic formed the second prong of the present trident sedimentary rocks accumulated. For a brief inter Colombian Andes. val in Aptian-Albian time, there was a seaway con nection across the Central Cordillera (Department CENOZOIC of Antioquia) to the Pacific, shown by fossiliferous. In early Tertiary time, a large inland basin sandstone and shale overlying metamorphic rocks formed over the continental platform east of the there. The Cretaceous miogeosynclinal seaway re Central Cordillera. The basin extended toward the ceded from south to north ; nonmarine sedimentation Guayana shield and p,robably merged with the east (Guaduas Formation) began in middle Maestrich west Barinas Basin of southern Venezuela and pos tian time in the Bogota region, whereas nonmarine sibly connected with the Maracaibo Basin in the beds appear at higher stages successively north area of the present Tachira Gap in western Venezu ward, and in the extreme northern part of the ela (fig. 7). Much detrital material came from the country ( Cucuta, pl. 1) , sedimentation became non rejuvenated Central Cordillera, ·as evinced by the marine in the Paleocene. In the Sinu Fold Belt, ma composition of the basal Tertiary strata, but the rine deposition continued well into the Cenozoic. enormous volume of Tertiary sedimentary m·aterial, West of the ancestral Central Cordillera enor including that of the Barinas Basin, requires that mous thicknesses of mafic volcanic and flysch-type substantial contribution must also have been de sedim.entary rocks accumulated in a Cretaceous eu rived from the interior of the continent. For brief geosyncline that extended along the Pacific coast, intervals the rate of subsidence increased, and through the northwestern edge of the present Sierra short-lived marine emhayments invaded the other Nevada de Santa Marta, and possibly to and beyond wise nonmarine environment. A similar geologic the northwest sid.e of the Guajira Peninsula, form s·etting may have been pres.ent along the west side ing a pericontinental arcuate belt (fig. 6) that con of the Central Cordillera, but lack of information forms generally with the outline of the continent. does not permit a clear understanding of the con The sedimentary rocks are mainly dark shale, gray ditions of deposition there. wacke, and impure :ailtstone. The associated volcanic Probably beginning in the Late Cretaceous and rocks are basaltic and contain some radiolarian culminating in middl·e Eocene time, a sharp orogeny cherts. Small ultramafic and serpentinite bodies cut took p·laee along the northwest side of the Guaj ira the deposits and are commonly fault bounded. Map Peninsula, extending through the northwest corner ping to date ·seem·s to indicate a concentration of of the Si-erra N ev·ada de S.anta Marta and continu these ultramafic bodies in the vicinity of the Ro ing southward along the Central Cordillera at least meral and other major faults (pl. 1) ; this concen to near lbague. This orogeny is widely reflected in tration may be illusory, however, because of the Eocene strata by unconformities, by thick and lack of comparable detailed mapping to the west. coarse conglomerate and sandstone horizons, and The Mesozoic Era closed with an important oro by transgressive overlaps by younger formations. geny that involved the eugeosyncline throughout its Cretaceous sedimentary rocks were locally metamor length. This orogeny formed the Western Cordillera phosed to greenschi1sts, and the orogeny culminated STRUCTURAL EVOLUTION 37 with the intrusion of the Parashi quartz diorite flexures, by high-angle reverse faults, or by strike stock in the Guajira Peninsula and the Santa Marta slip faults. In all detailed mapping to date, no im batholith in the Sierra Nevada de Santa Marta. portant gravitational sliding has been noted as a Southeriy directed thrust faulting in both these · cause fo·r folding in northern Colombia, in spite of areas postdates the orogeny. This orogeny, fol- the great and sharp relief between cordilleras and lowing the nomenclature of van der Hammen adjoining basins. Compressed folds, which· locally (1958), is referred to ·as "p.re-Andean." are -strongly overturned and have associated longi- N onmarine sedimentation continued over the con- tudinal reverse faults, indicate that deformation tinental platform in the interior of the country. was ·accomplished under compression. Upper Oligocene sedimentary rocks show some in- During Late Cretaceous and early Tertiary time, crease in grain size, indicating that transporting :strike-slip displacements on major faults were left agents were acquiring greater competence. During lateral, as shown by displacements on the Otu and the Oligocene and extending into early Miocene 8-anta Marta-Bucaramanga faults. These left-lateral time, s-everal granitic plutons were emplaced along displacem·ents offset large segments of the conti the Western Cordillera. This event and evidence of nental -platform and displaced Pal-eozoic and Meso local diastrophisms that prod.uced multiple sedi- zoic eugeosynclinal rocks in a northerly direction mentary cycles, are regarded as "proto-Andean" (fig. 9). At a later date, perhaps beginning with (van der Hammen, 1958). the middle Tertiary Andean orogeny, a new stress Along the area of the present axis of the Eastern : field formed in the crust and caused right-lateral Cordillera, Paleocene to Oligocene strata are less I strike-slip faulting; a 'rell-documented example is thick than Paleocene to Oligocene strata in the I the P.alestina fault (fig. 9), which displaces the trace M·agdaJena Basin to the west or in the Llanos Basin of Otu fault by 17.2 miles, in right-lateral manner. to the east. Of great significance is the fact that The p•resent altitudes of the Western, Central, and rather complete lower Tertiary sections are pre- 1· Eastern Cordilleras appear to be the result of epeiro served in sharp, deeply infolded synclines at alti- genic uplift after principal Andean folding. This tudes of 8,000 to 12,000 feet along the crest of the interp.retation is confirm-ed by the existence of high E·astern Cordillera. This suggests that these lower level erosion surfaces along various parts of the Tertiary formations were once coextensive wide- cordilleras, often upon soft sedimentary rocks. The spread deposits. They are regarded as stratigraphic Tilata Formation (Plio-cene) in the Bogota region equivalents of lower Tertiary beds in ~he adjoining was deposited on one such erosion surface. As the present basins. lowermost beds of the Tilata were reported by van Becaus·e of the suspension of deposition along der Hammen to contain humid tropical pollens that the present summit areas of the Eastern Cordillera could not have flourished above 1,500 feet, uplift in in Miocene time and the sudden appearance of dis- this area was on the order of 6,000-7,000 feet. tinctive lithologies in Miocene strata in adjoining Epeirogenic uplift began before the advent of Pleis basins, it is concluded that the principle Andean tocene glaciation becaus.e deposits of glacial origin orogeny began during the Miocene, .when the third are observed in many high mountain areas. Van der prong of the Colombian Andes (the Eastern Cor- Hammen and Gonzales (1963) and Raasveldt (1956) dillera) began to take its present form. reported m·oraines down to altitudes of 10,000 feet. During the Andean orogeny, moderate to intense Where the Isthmus of Panama joins the South folding took place in those areas where Cretaceous American Coutinent, high positive Bouguer gravity and (or) Tertiary sedimentary beds were extra- anomalies indicate that the Panamanian platform ordinarily thick, such as along the axis of the Cre- differs markedly from that of the Andean region. taceous miogeosyncline (fig. 6) and along the Car- The northwesterly trend of the isthmus, basement ibbean coast between the Gulf of Uraba -and the rocks of m·afic composition, high positive Bouguer Sierra Nevada de Santa Marta (pl. 1). Where the anomalies (Case and others, 1969), and the fact that Cretaceous and (or) Tertiary sedimentary cover the Upper Cretaceous and lowermost Tertiary strata was thin over competent continental platform rocks, contain abyssal to bathyal faunas (Bandy, 1968) in folding was much less intense and may have re- contrast to the shallow-water forms in upper Ter sulted from differential vertical movements along tiary strata, suggest that the isthmus belongs to an faults in the subjacent bas-ement rocks. Most oceanic geologic province that formed s.eparately northern Andean Cordilleras are bounded by sharp from the Andes. Comingling of vertebrate faunas be- 38 NORTHERNMOST ANDES, COLOMBIA tween the North and South American Continents be and this deformation accounts for part of their gan in middle Tertiary time, suggesting that the present relief. pres·ent isthmus carne into being during the Andean Throughout this p~esentation observations hav~ orogeny in Colombia (Van Houten and Travis, been directed rn~ainly to the hinterland regions back 1968). of present coastlines. This .stance has been justified, it is believed, owing to the absence of detailed geo CONCLUSIONS logical mapping in the heavy rain forest region along the Pacific coast and of the region where the Isth A study of the geologic history of the northern mus of Panama links with the South Arn·erican Con most Andean area from early geologic time to the tinent. Perhaps more importantly, i.t is well known p~esent, suggests that the trident Colombian Andes that the geology of the northern, central, and south formed during a series of events that took place ern Andes varies greatly (Ganss·er, 1973) and per along the margin of the Precambrian Guayana haps fundamentally, such that conclusions drawn shield, whe·re the shield meets the Pacific oceanic from one sector are only partially valid, or invalid, crust. These events are as follows : for another. For these reasons hypothetical discus 1. During Paleozoic time, a pericontinental eugeo sions of continental drift or plate tectonics have been syncline formed around the northwestern edge ·held in abeyance until such time that a better ob of the Precambrian Guayana shield. At the servational base is developed for the entire cordillera close of the Paleozoic, a powerful orogeny in system. volved rniogeosynclinal platform deposits on the margin of the shield and the ·eugeosynclin SELECTED REFERENCES al deposits; metamorphism in the orogenic axial area included anatexis and was followed Alberding, Herbert, 1957, Application of principles of by granitic intrusion to produce the ancestral wrench-fault tectonics of Moody and Hill to northern Central Cordillera and its northeast extension South America: Geol. Soc. America Bull., v. 68, no. 6, p. 785--790. through the Si·erra Nevada de Santa Marta Alvarez, A. J., Hall, R. B., and others, 19.70, Mapa geol6gico (Sevilla arc) to the area of the Guaj ira Penin del cuadrangulo H-8 (Yarumal) y·parte del cuadrangulo sula (Guajira arc). H-7 (Ituango), Depto. de Antioquia: Bogota, Colombia 2. During the Mesozoic Era, a second periconti In st. N ac. Inv. Geologico-Mineras, scale 1:100,000. nental eugeosyncline formed outside and Alvarez, Walter, 1967, Geology of the Simarua and Carpin tero areas, Guajira Peninsula, Colombia: Princeton, N.J., oceanward from the J,ate Paleozoic orogenic Princeton Univ., unpub. Ph.D. dissert., 168 p. belt, and in Late Cretaceous time the eugeosyn Anderson, F. M., 1927, Nonmarine Tertiary deposits of cline became involved in ·an orogeny which re Colombia: Geol. Soc. America Bull., v. 38, p. 591-644. sulted in the ancestral Western Cordillera. Anderson, J. L., 1945, Petroleum geology of Columbia, South America: Am. Assoc. Petroleum Geologists Bull., v. 29, 3. Throughout Phanerozoic time, the area east of no. 8,p. 1065-1142. the Central Cordillera was underlain by the Anhaeusser, C. R., Mason, Robert, Viljoen, M. J., and Viljoen, Guayana shield and, except during the intra R. P., i969, A reappraisal of some aspects of Precam cratonic Late Ordovician and Jurassic oro brian shield geology: Geol. Soc. 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INDEX [Italic page numbers indicate major referencesl Page Page A Cauca River, .role in Pliocene, Pleistocene. and Holocene erosion 22 Central Cordillera, basin deposition. late Paleozoic inner eugeosyn- Adampada-Fallawatra in Surinam, eugeosynclinal Precambrian rocks 2 clinal (west flank) and outer miogeosynclinal deposi- Age provinces of granitic intrusivE' rocks ------26 tion (east flank) ------11,12, 24, 34 Akawaian episode, Precambrian igneous activity ------5, 33 basin deposition, Mesozoic miogeosynclinal and eugeosynclinal Alas thrust fault ------··------27 deposition ------15, 17,35 Alluvial-fan deposits ------··------22 postulated early Paleozoic eugeosyncline ------8 Amaga stock ------11, 24 probable Paleozoic age of bulk of rocks that constitute Amazon p1·c-Andcan drainage ------21 cordillera ------8, 33 Amphibolite ------1)., 17, 26, 34,36 edge of craton (westernmost Precambrian rocks along eastern Anacue River, gr'lmitic intrusion into Jurassic volcanic rocks ------15 flank and line of much later intrusive rocks) ____ 6, 24, 26, 34 Anatectites ------12, 24, 34,38 faulting, high-angle reverse marginal faults ------29 Angular discordance, Devonian with Pennsylvanian and Permian probable dislocated block of Precambrian and Ordovician rocks _ ------___ ------___ ------.-- 34 rocks in Central Cordillera ------5, 8, 30 Ordovician with Devonian rocks ------·------9 westward thrust of mountain block by Romeral fault ------29, 31 Tertiary rocks with Pliocene and Pleistocene deposits ------18 folding in metamorphic terrane, upper Paleozoic rocks ------26 Antloquia Department, Pescado stock ------····------25 igneous rocks volumetrically large ------22 Puqu( Metatonalite ------11 intrusive rocks (plutons" and batholiths), Cretaceous age, pre- Valdivia Group ------11 dominant area of intrusion ------17, 25, 26, 33, 36 Antioqulan batholith ------17, 25, 86 Cretaceous, ultramafic and serpentinite bodies (west flank)-- 25,86 Arcabuco Formation ------14 Eocene age ------18,25 Atrnto fault ------32 Late Permian to Lower Triassic age ------11, 24, 26, 83 Atrato synclinorium ------· ------82 Triassic-Jurassic age (eastern flank, not predominant area Ayura-Montebello Formation ------11 of intrusion) ------15,24,115 nontectogenic in normal sense ------15 B Late Cretaceous orogeny (central part) ------17,86 late early to middle Eocene orogeny ------18,36 Bnramn-Mnznruni assemblage in Guyana, Precambrian rocks ------2 late Paleozoic orogeny ------12, 34, 38 Barco Formation, Maracaibo Basin ------18 Permian age of oldest Paleozoic rocks ------11 Bnrinas Basin ------21, 31, 36 Pleistocene glaciation ------22 Basal I'Onglomerates, Devonian age (Fiorcsta Formation) ------·-- 9 regressive seaways, withdrawal during Maestrichtian ------15 Jurassic age (Jorddn Formation) ------15 withdrawal from Precambrian continental platform at close Late Permian or Triassic age (Tibur6n Formation, Corual of Paleozoic ------34 Formation, and Prepayande Formation) ------11, 12 uplift, epeirogenic in late Tertiary and Holocene ------22, 26, 38 latest Mississippian age ------9 mostly emergent through and after Cretaceous time except middle Eocene age ------36 for Cretaceous (Aptian-Albian) seaway through central Bocns Formation ------11, 12, 34 part ------15, 17, 20, 36 Bogota, one Oretaceous miogeosynclinal axis of subsidence ------15, 36 rejuvenation during Late Cretaceous orogeny ------18 Bogota-Villavicencio road, Quetame Series ------8 rejuvenation during Miocene Andean orogeny ------21 Bolivar fault ------17 source of sediment to Cretaceous geosynclines and Tertiary Bo!ivnr geosyncline ------32 megabasins to east and west ------17, 18, 21, 22, 31, 36 Bouguer gravity anomalies ------37 volcanic rocks, Paleozoic age ------8, 11, 26, 34 Boyne!\ Department, Arcabuco Formation ------14 upper Tertiary and Holocene age ------20, 22,26 Cuche Formation ------9 Triassic-Jurassic age ------12, 15, 24, 85 Floresta Formation _---- ___ ------______---____ ------_____ --_ _ 9 silicic (east flank) ------24 Gir6n Group ------14 Montebel Formation _ ----- ___ --- ______12 Cerrej6n Formation ------18 Cesar Basin, center of a Cretaceous miogeosynclinal axis of subsi- Quetame Series ------8 dence ----___ ---___ ------__ ------15 Bucaramanga Gneiss (Precambrian) ------6, 8 conformity of uppermost Cretaceous marine formations to Ter- Bucaramanga region, Diamante Formation ------9 tiary nonmarine formations ------18 hypothesized union with Middle Magdalena Basin before late 0 Tertiary time ------29 late early to middle Eocene deposition ------18 Cachiri Group, Venezuela ------9 volcanic rocks, Triassic red beds ------12 Cajamarca Group ---"------11 Chandua Group ------9 Cambrian rocks ------6 Chapiza Formation, Ecuador ------14 Cafinsgordas Group ------17 Choc6 Department ------25 Caribbean Coastal Pla!n, marine Miocene deposition ------20 Cimitarra strike-slip fault ------81 Carichnpo Series of Venezuela, Precambrian rocks ------5 Coal ______------___ ------15, 18 Cauca Basin, faulting, high-angle reverse marginal faults ------29, 82 Coastal sedimenbry wedges ------92 late early to middle Eocene deposition ------18 Compressive forces in folding and faulting ------27, 29, 32,37 nonmarine Miocene deposition ------20 Conclusions _ ----______------___ ------_------98 structural style, similarity to that of Upper and Middle Continental accretion, Late Cretaceous ------_------17 Magdalena Basins ------32 late Paleozoic ------12, 84 transgressive marine tongues, Eocene from Pacific ------18,20 Continental drift ______---_------38 volcanic rocks, upper Tertiary to Holocene ------26 Corual Formation 12 43 44 INDEX Page Page Cosinas Group ------14 Epizonal intrusive rocks ------24,25 Cretaceous magmatism ------!25 Etpana Formation ------17, 27 Cretaceous rocks ------15 Cristalina, Ordovician shale ------8, 11 F Cuche Formation ------9 Cueva Creek, Ordovician rocks ------6 Faults, deep seated, expression as fo!ds in overlying rock ------27, 37 Cuisa strike-slip fault ------30 high-angle reverse ------!27 Cundinamarca Department, Gachahi Formation ------9 strike-slip ------!29, 37 Quetame Series ------8 Floresta area, Cuche Formation ------9 Sumapaz section ------11 Giron Group ------14 Floresta Formation ------9 D Flysch-type sedimentary rocks ------17,36 Folding, in metamorphic terranes ------!26 Dagua Group ------""------16, 36 in unmetamorphosed terrane ------!27, 37 Devonian rocks ------8, 9 syndepositional Miocene ------21 Diabase G Page Page H M Harmonic folds 27 Maco Conglomerate ------18 Haut Sinnamary district of French Guiana, oldest Precambrian Macuira Formation ------11, 24,27 rocks in Guayana shield ------2 Magdalena River ------22 Holocene rocks ------S!l Magmatis~ __ ------!!I Homocllne ------______---___ ------______32 Mede!Un area, Ayura-Montebello Formation ------11 Honda Group ------22, 31 Mercedes thrust fault ------27 Huila Department, Carboniferous rocks ------9 Merida Andes, Venezuela ------21, 31 Devonian 'rocks ------9 Mesa Group ------.,----- 22, 31 Glr6n Group ------14 Mesozonal intrusive rocks ------24, 26 Hypabyssal rocks ------24,26 Metamorphic contacts, Eastern Cordillera, Devonian (m.) in same area as Permian and Triassic (n. m.) ------9 Eastern Cordillera, Silgarti Schist (1. to m. m.) with Devonian rocks (n. m.) ------8 Central Cordillera, Cajamarca Group (Late Permian) (m.) lbague, Cajamarca Group ------11 with Payande Formation (Late Triassic) (n. m.) ----- 11 lbngue batholith ------15,24 Central Cordillera, Cretaceous (n. m.) with Paleozoic (m.) __ 36 Ignimbrites ---___ ------__ ------_ ------14, 24 Central Cordillera, Ordovician shale (s. m.) with probably Jitujuru thrust fault ------27 lie de Cayenne in French Guiana, eugeosynclinal Precambrian rocks 2 Precambrian paragneiss (h. m.) ------8 Guajitra Peninsula, Macuira Formation (Paleozoic) (m.) with Imataca Gneiss Complex in Venezuela, eugeosynclinal Precambrian rocks ------______------______2 La Quinta Formation (Triassic) (n. m.) ------11 Metamorphism, contact, Central Cordillera, Cretaceous ------17,36 Interior basins, Tertirury to Holocene ------91 regional, Eastern Cordillera, general absence of ------11, 27 difficulty In correlating from basin to basin ------21 Eastern Cordillera, Late Devonian, low rank (greenschist Intrac1·atonic orogenies ------34, 38 facies) ______----_ ------______9, 34 Intrusive rocks, age provinces, sequential arrangement of ------26 migrating magma iiront along Central Cordillera (Cretaceous) __ 26 Eastern Cordillera, Ordovician, low to medium (sillimanite) syntectonic, synmetnmorphic ------8, 11, 24,33 rank ------8, 33, 34 Central Cordillera, Late Permian to Early Triassic, low to time relation of volcanism to plutonism ------14, 16, 36 high rank (greenschist to high amphibolite) __ 11, 12, 24, 34 Isthmus of Panama ------9!1, 37,38 Guajira Peninsula, Cretaceous, low (greenschist) to high (lower amphibolite) rank ------26, 36 J Guajira Peninsula, Late Permian to Early Triassic, low to high rank ______:______11 Jagua, Devonian rocks ------9 Guajira Peninsula, middle Eocene, low rank (greenschist) 18,36 Jamundl Conglomerate ------18 Sierra Nevada de Santa Marta, Cretaceous, low (green- Jarara Formation ------17, 26, 26,27 schist) to high (-amphibolite) rank ------17, 26,86 J etudo fault • ___ --_ -----______------81 Sierra Nevada de Santa Marta, Late Permian to Early Jordlin Formation ------14 Triassic, low to high (amphibolite) rank ------11 Jurassic magmatism ------16, !I-' Sierra Nevada de Santa Marta, middle Eocene, low rank Jurassic rocks ------1-' (greenschist) ------18, 26, 36 Precambrian, high (amphibolite to granulite) ___ 6, 6, 8, 12, 26, 83 K Western Cordillera incipient ------17, 27, 36 .retrograde in Paleozoic rocks ------24 Kanuku in Guyana, eugeosynclinal Precambrian rocks ------2 in Precambrian outer shield rocks ------6 Kasipoch thrust fault ------27 Middle Magdalena Basin, coextensive with Llanos Basin, Tertiary__ 37 Keratophyrlc volcanism ------12, 14, 36 faulting, high-angle reverse marginal fault (east) ------21, 27 Kneading structures ------26 high-angle reverse post-Miocene ------31 Kopinang Valley dolerite in Surinam-Guyana-Venezuela, Pre- folding, relation to uplift of Eastern Colrdillera ------81 cambrian rocks ------6 Tertiary strata more competent than in adjoining Eastern Cordillera ---______------___ ---______------___ ----- 32 L late early to middle Eocene deposition ------18 Lower Jurassic marine beds (Morrocoyal Formation) ------16 Labateca Formation ------9, 11 molassic Paleocene beds ------18 Ln Clra Formation ------20 nonmarine Miocene deposition ------20 wedge out of Cenozoic beds toward Central Cordillera .flnd La Paz Sandstone ------18 La Quinta Formation ------11, 14 thickening toward Eastern Cordillera ------21 Miocene rocks ------___ __ : ______------!10 Late Paleozoic magmatism ------!I-' Limbo Shale ------18 Mirador Sandstone ------18 Limestone, marbleized ------11 Mississippian rocks, general absence of ------9, 34 Lisama Formation ------18 Molassic offwash ------14,18 Littoral sandstone, Jurassic, Batli River ------14 Montebel Formation ------12 Llanos Basin, faulting, high-angle reverse, marginal fault (west)__ 21 Monterla, thickness of Tertiary beds near ------32 folding, Tertiary strata more competent than that of Eastern Morrocoyal Formation ------14 Cordillera ------______------___ ------__ 27 Mugrosa Formation ------20 nonmarine Miocene deposition ------20 Mulato fault ------31 Oligocene deposits thicker than those across Eastern Cordillera. 87 Ordovician shale ------8 N Tertiary beds thicken westward towrurd Eastern Cordillera ---- 21 transgressive seaways, Eocene and Oligocene marine tongues Nariiio Department ______------______------__ _ 26 from Caribbean ------18,20 Neiva Formation ------31 Los Clavos Granite ------16 Nickerian episode in Guyana, Precambrian igneous activity ------ 6 Los Indios Formation ------12 Norte de Santander Department, Bucaramanga Gneiss ------8 Los Mangos Granulite Series (Precambrian) ------6, 26 Silgara Schist _ ------______------8 Lower Magdalena Basin, basement Mesozoic eugeosynclinal rocks.. 32 coastal wedge ovarlapping crystalline Paleozoic and Precambrian 0 rocks of Central Cordillera ------82 folding, axes northeast ------81 Oca strike-slip fault ______----_____ ------30 late early to middle(T) Eocene deposition ------18 Ocaiia porphyritic microgranite ------26 46 INDEX Page Page Oligocene rocks ------110 Radiogenic ages-Continued Ordovician magmatism, Late ------24,26 igneous rocks near Quibd6, on highway between Buenaventura Ordovician rocks ------6 and Cali, and near Pasto ------25 Orinoco drainage before Andean fo~ding ------21 Late Ordovician orogeny ------8, 9, 24, 83 Orinoco igneous cycle in Venezuela, Precambrian intrusive rocks__ 5 Los Clavos Granite ------15 Orogenies, Late Cretaceous (Western Cordillera and Antioquian middle Eocene-Oligocene orogeny ------18 area) ______------_____ ------___ 17, 38 orthogneiss syntectonic into Silgara Schist and Buearamanga Late Devonian disturbance ------9 Gneiss ------24 Late Ordovician ------8, 9, 38 orthogneiss syntectonic of Puguf Metatonalite ------11, 24 late Paleozoic (Central Cordillera-Seville arc-Guajira arc) __ 11, 38 Parashi stock ------25 late Precambrian ------5 pegmatite in Maeuira Formation ------11, 14, 24 Late Triassic-Early Jurassic (Santander-Santa Marta area) __ 15, 17 peralkalic syenite rocks at San Jose de Guaviare ------8, 24, 84 middle Eocene (Santa Marta-Guajira) and Oligocene (Western Peseado stock ------25 Cordillera) disturbances ------18, 36 postspilitie rocks Sierra Nevada de Santa Marta ------25 Miocene (Andean) ------·-- 110,37 quartz diorite pluton near Santa Marta ------25 Oriorio th~st fault ------27 Rfo Sevilla stock ------25 Otu strika.slip fault ------24, 90, 37 Sevilla Complex gneiss ------11, 24 Sons6n batholith ------17, 25 p Triassic batholiths ------14 Real Formation ------20, 81 Pacific Coasta' Basin, littoral wedge of Tertiary strata adjacent Red beds ------11, 12, 14, 85 to Western Cordillera ------20, 32 Rift zone(?), Central Cordillera, marked by present volcanoes ----- 26 relation to Cauca Basin unknown ------32 Rfo Bata, Cambrian and Ordovician rocks ------8 Paleocene rocks ------18 Devonian rocks ------8, 9 Paleocurrent studies ------22 Lower Jurassic sandstone ------14 Palestine strika.slip fault ------31, 37 Palinspastic interpretations, movement on Santa Marta- Rfo de Oro-Puerto Nuevo road, metadiorite ------8 Bucall'amanga fault ------30 Rfo Negro Formation ------14 movement on OtU fault ------8,11, 30 Romeral strike-slip fault ------24, 29, 91, 36 Paramos, defined ------22 Roraima Formation in Surinam-Guyana-Venezuela, Precambrian Parashi pluton ------18, 25, 37 rocks 5, 88 Pastora Series of Venezue~a, Precambrian rocks ------5 Payande Formation ------11, 12 8 Pennsylvanian rocks ------9 Perieontinental geosynclines ------36, 38 Salinas high-angle reverse fault ------27 Permian rocks ------9 Salt deposits ------27 Permian to Lower Triassic intrusive rocks ------114, 26 San Fernando Formation ------20 Pescadero batholith ------14 San Jacinto Conglomerate ------18 Peseado stock ------25 Phosphorites ----______----______------______15 San Lorenzo Schist ------30 Santa Ana thrust fault ------27 P'ate tectonics ------38 Santa Barbara batholith ------14 Pleistocene glaciation ------22,37 Santa Marfa high-angle reverse fault ------29 Pleistocene rocks ------1111 Santa Marta-Buearamanga strike-slip fault ------29, 87 Pliocene rocks ------_ -----_-- ______------______22 Santa Marta pluton ------18, 87 Popavan, Dagua Group(?) ------15 1 Santander arch ------_---- _ _ _ 17 Porph:vr tie Formation ------17,25 Santander Department, Buearamanga Gneiss ------8 Post-Andean denudation or erosion of cordilleran areas ------22 Diamente Formation ------9 Postpayande Formation ------12 Floresta Formation ------9 Precambrian magmatism ___ ------_------112,26 Labateea Formation ------9, 11 Precambrian rocks ------B Silgara Schist ------8 Precambrian structural evolution ------99 Surata Group ------12 Prepayande Formation ------12 Santander massif · ------24, 26, 35 Present altitudes of Cordilleras ------37 Serpentinite ------17, 25, 86 Puquf Metatonalite ------11, 24, 25, 34 Serranfa Macarena, Devonian rocks(?) ------9 Gilejar Series ___ ------______--______----___ ----- 6 Q marine tongues during Oligocene time ------20 Precambrian· granitic intrusive rocks ------22 Quebrada Grande Formation ------ 17 Serranfa de Perija, basin deposition, early Paleozoic miogeosyneline Quetame area, Carboniferous rocks ------9 and eugeosyncline(?) ------8 Devonian rocks --_ ------9 burial of northern end ------... ------30 Quetame Series 8 Devonian rocks ------9 Early Cretaceous red beds ------14 R low degree of metamorphism in Paleozoic rocks ------8, 11 Mississippian rocks . ------9 Radar maps ------32 Sevilla are ------_ ----_ ----______----_ 11, 84 Radiogenic ages. Amaga stock ------11. 24 Sevilla Complex ------26 Antioquian batholith ------17, 25 Sierra de Farallones-Llanos Basin cross section, structural relief ___ 21 ash beds of basal Tilata Formation ------22 Sierra Nevada de Santa ·Marta, basin deposition, Cretaceous eugeo- diorite intrusion into Jurassic volcanic rocks ------15, 24 syncline ------17, 25, 36 early O'igocene to early Miocene batholiths near Quibd6 and basin deposition, late Paleozoic miogeosynelinal-eugeosynelinal Pasto ______------______------_ ------__ 20 couple ------12, 84 El Bosque batholith ------25 nearshore facies ( ?) ------9 granite core from Cieueo oil field well ------25 continental deposition, Triassic red beds (Guatapurf Formation)_ 14 Guayana shield, oldest Precambrian rocks ------2 faulting, dislocated mass as one theory of formation ------30 oldest Precambrian rocks in Colombia ------5, 22, 29, 33 thrusting that postdates middle Eocene orogeny ------87 Precambrian intrusive rocks on Guaviare ·River ------22 folding in metamorphosed Cretaceous-Tertiary rocks during Precambrian rocks throughout ------2, 5, 6 Andean orogeny in Precambrian rocks ------26, 87 Ibague batholith ------15, 24 igneous rocks volumetrically large ------22 INDEX 47 Page Page Sierra Nevada de Santa Marta-Continued Upper Magdalena Basin-Continued intrusive rocks (plutons and batholiths), Cretaceous age ------26 molassic Paleocene beds ------18 Eocene age, main area of intrusion ------18, 26, 26, 37 stress adjustments in lower Tertiary rocks ------20 Late Permian to Early Triassic ------11, 12, 24, 26 volcanic rocks, Miocene to Holocene ------26 Triassic-.Jumssic age ------14, 16, 24,36 Uraitchipa fault ------27 late early to middle Eocene orogeny ------18, 36 Uray Gneiss Member of the Macuira Formation ------11 late Paleozoic orogeny ------11, 12, 34, 38 Uribe, Cambrian rocks ------6 Precambrian rocks, edge of cmton ------6, 12, 26 Usme Formation ------18 transgressive seas, Late Permian(?) or Early Triassic ------12 uplift, vertical in late Tertiary time ------29,30 v volcanic rocks, Cretaceous age ------26, 26, 36,36 Triassic-Jurassic age ------12, 14, 16, 24, 26, 26, 36 Valdivia Group ___ - -- _-- _------11 Sierra Nevada del Cocuy-Llanos Basin, structural relief cross section 20 Valle Department ------25 Silgar(l Schist ------8, 33 Vertical forces in folding ------.. --- 11, 27, 38 Silurian 1·ocks ------9, 34 Virginias, diorite intrusion into Jurassic volcanic rocks ------15, 24 Simarua area _-- ____ -- ______--______------_------27 Sinu Fold Belt, Cenozoic deposition ------36 w coastal wedge ------32 folding, in unmetamorphosed termne, Tertiary strata ------27,32 Wells, Cicuco oil field ------26 underlying rocks ------32 La Heliera No. 1 ------8 Sogamoso River, Jord{tn Formation ------14 Negritos No. 1 ------8 Soil profiles, vo!canic ash in ------22 Perico well ------30 Sons6n batholith ------17,26 Superior Oil Co. Algarrobo 7 ------30 Spilitic volcanism ------12, 14, 24, 36 Western Cordillera, basin deposition, Cretaceous eugeosynclinal Structun·al evolution ______--_ --___ --- ___ --- ____ ------SS rocks, bulk of sediments ------17, 33, 36 Structure ------__ ------_------_ --- __ ------26 basin deposition, Jurassic(?) eugeosynclinal rocks ------16, 36 Syenite ______----____ ---___ ------8, 24 megabasin during early Tertiary time ------21 faulting, high-angle reverse marginal faults ------21, 29 T folding in unmetnmorphosed Mesozoic terrane ------27 igneous rocks volumetrically large ------22 Taganga Group ------26,30 intrusive rocks, Cretaceous ultramafic and serpentite bodies ____ 25, 36 'l'alc schist --_ ------_ -- __ ------_-- ___ --_ ------__ ------24 Oligocene-Miocene age ______:______20, 25, 26, 33 'faphrogenesis ______--- ___ --- _----- _-- _------31 Late Cretaceous orogeny ------17, 36, 38 Tertiary magmatism ------25 no rocks older than Jurassic ------36 Tibur6n Formation ------11, 34 Pleistocene glaciation ------22 'filata Formation ______• __ ----______----______- -- __ -- 22, 31, 37 transgressive seaways, Eocene marine tongues ------18 Tolima Department ------12 uplift, post-Miocene epeirogenic ------22, 37 Tt•ansamazonas igneous cycle (Precambrian) ------6, 33 rejuvenation during Andean folding ------21 Trangressive overlaps ------___ ------36 source of sediment to Tertiary megabasins same as in East- Tl'iassic magmatism ------24 ern Cordillera ( ?) ------21 Triassic rocks ______• ____ ------__ ----______---___ ---_ 11, a, 34, 36 volcanic rocks, Cretaceous age ------15, 17, 25, 33, 36 Jurassic ------15, 17, 24, 33, 35 u y Upper Magdalena Basin, cycles of nonmarine Miocene sedimentation 21 dh·ection of source of Miocene and Pliocene sediments ------ 31 Yarumal, Puqui Metatonalite 11 folding, Tertiary strata more competent than in adjoining Eastern Valdivia Group ------11 Cordillera ______------32 Yopal high-angle reverse fault ------29 'i: U.s. GOVERNMENT PRINTING OFFICE: 1974 0-585-469/12