Darwin's geological research in Argentina
Beatriz Aguirre-Urreta,
Miguel Griffin,
Victor A. Ramos
Invited Editors
Portrait with signature gifted by Charles Darwin to the Academia Nacional de Ciencias in 1878 acknowledging his nomination as an Honorary
Member. Photograph taken by Julia Margaret Cameron in 1868. Unpublished original copy kept in the Academia (see Depetris this volume)
On the occasion of the 200th. anniversary of Charles Darwin´s birth, the Asociación Geológica Argentina decided to prepare a special issue devoted to the geological research undertaken by Darwin in Argentina. As it is well known, during his journeys on board HMS Beagle under the command of Captain Robert FitzRoy, he had the opportunity to survey overland different areas of South America. Darwin spent nearly three years - between August 1832 and April 1835 - visiting and studying different regions of our country, as illustrated in figure 1.
Figure 1: Journeys of HMS Beagle in southern South America (base map modified from Bowly
1990). Dates of Darwin's rides overland are shown in bold while the trips on board HMS Beagle
are shown in italics, taken from Keynes (2001).
The aim of this special issue is to analyze
his important geological observations
and to emphasize the validity of many of
his ideas under a 21st Century perspective.
In order to accomplish this aim, several
key localities that Darwin examined
from a geological point of view during
his voyage were selected. Such an analysis
was carried out by several geologists
and paleontologists well acquainted with
the diverse problems that Darwin faced
along his journeys in Argentina.
HMS Beagle's main mission was to survey
the coasts of southern South America,
which it carried out during several
journeys along the coast. The time needed
to chart the coast in details gave
Darwin several opportunities to spend
considerable time on land. During the
survey he also had many occasions to
land at selected points along the Atlantic
coast.
The first of these fieldtrips was done
between August and October 1832 and
gave him the opportunity to visit Punta
Alta near the fort of Bahía Blanca (Fig.
1). The second one was between November
1832 and May 1833 to visit the
Beagle Channel, the surrounding areas of
Tierra del Fuego Island, and the Malvinas
Islands.
The third and more important fieldtrip
was, after landing in Carmen de Patagones
in August 1833 (Fig. 1), to ride
across the Pampas to Buenos Aires city and later on to Santa Fé and Bajada (today
Paraná city) on the Río Paraná.
The fourth trip began in Montevideo in
December 1833 and allowed Darwin to
examine various points along the Patagonian
coast such as Puerto Deseado
and Puerto San Julián. Afterwards HMS
Beagle sailed to Tierra del Fuego where it
spent nearly four months until March
1834. Later on it visited again different
areas of the Malvinas Islands. In April of
1834 it anchored in the mouth of Río
Santa Cruz. It was during this trip that
Darwin, FitzRoy and more than 20 crew
members sailed upstream the Río Santa
Cruz in three small whale boats, almost
reaching its headwaters near the foothills
of the Patagonian Andes.
This fourth trip continued across the
Magallanes and strait of along the Pacific
coast landing in Valparaíso in July 1834,
and spending several months surveying
the Chilean coast.
Darwin's last visit to Argentina was between
March and April 1835 (Fig. 1),
when he crossed the Andes between
Santiago and Mendoza following two different
cordilleran passes.
The different contributions of this issue
were organized based on stratigraphic
record and location (Fig. 2). The sections
of the Andes are the first to be analyzed,
then Patagonia and Tierra del Fuego, and
finally the Cenozoic of the Pampas,
ending with the origin of Puente del Inca
and Darwin's tectonic ideas on the formation
of the Andes.
Figure 2: Approximate location of the different contributions dealing with Darwin's geological
research in Argentina indicated by an asterisk (compare with Figure 1).
Pedro J. Depetris describes the documents
kept in the Academia Nacional de
Ciencias in Córdoba related to the nomination
of Darwin, first as corresponding
member and then as honorary member
of the Academy. This paper also presents
Darwin's original letter where he acknowledges
the nomination and the front
page of the book on the Origin of the
Species that Darwin dedicated to the
academy.
Stella Poma, Vanesa D. Litvak, Magdalena
Koukharsky, Beatriz Maisonnave
and Sonia Quenardelle describe the rocks
in which the Triassic forest at Agua de la
Zorra is included as being part of a pyroclastic
flow. Their petrographic studies
confirm the previous description of Darwin
on the presence of fine volcanic material.
Based on their observations, they
answer Darwin's queries about the process
that buried the forest in standing
position. It should be noted that these pyroclastic flows were unknown at the
time of Darwin's visit.
Mariana Brea, Analía E. Artabe and Luis
A. Spalletti deal with the first in situ forest
discovered in South America by
Darwin in his trip across the Andes. This
forest was described in detail by Darwin
as monotypic and assigned to the Tertiary.
Their study reveals that the paleovegetation
of Agua de La Zorra forest is
composed by conifers and corystosperms
reaching up to 20-26 meters high
forming a two-storeyed arboreal strata
and an understorey of ferns. It was reassigned
to the Triassic and reconstructions
of the forest landscape are presented.
Beatriz Aguirre-Urreta and Verónica
Vennari study a small collection of fossil
invertebrates from the Piuquenes Pass, a
locality discovered by Darwin during his
crossing of the High Andes from Santiago
to Mendoza. They compared this
collection with the fossils that allowed
Darwin to propose a Neocomian age for
the bearing strata. This assignation is
confirmed and the time span stretched to
the Tithonian based on key ammonites
of that age.
Laura Giambiagi, Maisa Tunik, Victor A.
Ramos and Estanislao Godoy compare
the observations of Darwin on the structure
of the High Andes between the
Piuquenes and Portillo passes with modern
structural knowledge. They remark
the awareness of Darwin on the episodic
uplift of the Andes with the rise of the
Principal Cordillera first and a later uplift
of the Frontal Cordillera, both in post-
Cretaceous times.
Eduardo Zappettini and José Mendía
introduce the first geological map of
Patagonia ever compiled, publishing the
first color hand-drafted copy. It was
drawn by Darwin after his trip to South
America. These authors outline the main
geological units used in the map and validate
them with the present knowledge of
the geology of the region.
Eduardo B. Olivero, Francisco A. Medina
and María I. López C. analyze the
still unsolved problem of Darwin's "Clay
Slate Formation" in the Fueguian Andes.
This term coined for the Cretaceous successions,
presently includes a series of
marine mudstones the stratigraphy of
which is based on scarce fossils, mainly
inoceramids and ammonites. The present
use of trace fossils and distinctive ichnofabrics,
together with new ammonites,
are contributing to a better understanding
of these mudstones, improving stratigraphic
correlation among different
units.
Ana Parras and Miguel Griffin present
the sedimentology and fossil contents of
a classic Miocene locality, first described
by Darwin at the southern bank of Río
Santa Cruz, along the Patagonian coast.
This is the type locality of most of the
fossils found in his "Great Patagonian
Tertiary Formation" and later described by
Sowerby (1846). The rocks of this section
are presently included in the Monte
León Formation.
The contribution by Silvio Casadio and
Miguel Griffin deals with the sedimentology
and paleontology of a classic locality
at Puerto Deseado (Port Desire).
This locality was visited by Darwin in
1833 when he collected fossil mollusks,
and remained nearly unexplored by geologists
and paleontologists ever since.
The authors assess this classic Miocene
locality and correlate it with several similar
sequences exposed along the Atlantic
cliffs.
Oscar A. Martínez, Jorge Rabassa and
Andrea Coronato discuss one of the
most intriguing lithostratigraphic units in
the Late Cenozoic of Patagonia named
by Darwin the "Patagonian Shingle Formation".
They analyze the prevailing paradigm
of that time that assigned these
rocks to the "Great Universal Dèlluge" and
give a modern perspective to the origin
of the "Rodados Patagónicos".
Jorge Strelin and Eduardo Malagnino
analyze the observations of Darwin in
his trip upstream the Río Santa Cruz in
1834. Special emphasis is paid to the
extension of the big erratic boulders and
gravels described by Darwin which are
now interpreted as indicators of a maximum
glacial expansion in Patagonia.
Those blocks together with some new
findings are ascribed by these authors to
a catastrophic event related to the outburst
of a large lake.
Martín Iriondo and Daniela Kröhling cover
the visit of Darwin to Santa Fé with
special emphasis in those localities described
by him along the Río Paraná banks. The authors stress the precise descriptions
of Darwin and discuss the Late
Cenozoic age of these sediments.
Marcelo Zárate and Alicia Folguera deal
with the geologic characteristics of the
Pampas south of Río Salado, a region
that impressed Darwin on his ride from
Bahía Blanca to Buenos Aires. They discuss
the Pampean Formation of Darwin,
its present stratigraphic divisions, its age,
and the different environments encompassed
in this unit, from a modern perspective.
Mirta E. Quattrocchio, Cecilia M. Deschamps,
Carlos A. Zavala, Silvia C. Grill
and Ana M. Borromei give an updated
vision of the scenery described by Darwin when he visited Bahía Blanca and
surrounding areas. Multidisciplinary results
were integrated by these authors in
a chronosequence chart. This diagram
shows the suggested space-time correlation
of the recognized events in the Late
Miocene-Holocene history of the southwestern
Pampas.
Juan Carlos Fernicola, Sergio F. Vizcaíno
and Gerardo De Iuliis provide a synthesis
of the present knowledge of the large
fossil mammals collected by Darwin,
mostly from the Pampean region of central
Argentina. These authors ponder on
the reasons that led Darwin to recognize
only megatheres and mastodonts for the
large fossil remains and discuss the current
taxonomic status of the taxa described
or erected by Owen between 1837
and 1845.
Sergio F. Vizcaíno, Richard A. Fariña and
Juan Carlos Fernicola, in their contribution
on the Pleistocene South American mammals, attempt to provide answers to
Darwin's questions, such as what has
exterminated so many living creatures?
Their study on the palaeobiology of
these organisms shed light on the understanding
of their evolution intermingled
with ecology and phylogeny.
Victor A. Ramos searches on the origin
of Puente del Inca, a natural bridge described
by Darwin in the High Andes,
during his cross by the Uspallata o La
Cumbre Pass. Applying uniformitarism,
the author interprets the origin of Puente
del Inca as initially formed as an ice
bridge, latter on cemented by hot spring
waters. Ramos also weighs Darwin's
thoughts on mountain uplift based on
the Mesozoic successions of the Puente
del Inca section. His old ideas on tectonics
anticipate in many decades some
concepts of the geosynclinal theory and
also on the present fold and thrust belt
mechanics.
We would wish to acknowledge the reviewers
of the present issue: S. Bargo (Universidad
Nacional de La Plata), M. Bond
(Universidad Nacional de La Plata), N.
Carmona (CADIC, Ushuaia), C. Costa
(Universidad Nacional de San Luis), R.
Charrier (Universidad de Chile), J.S.
Crampton (Institute of Geological and
Nuclear Sciences, New Zealand), A.
Crame (British Antarctic Survey, UK), D.
Croft (Case Western Reserve University,
USA), I.W.D. Dalziel (University of
Texas, USA), R. De Barrio (INREMI, La
Plata), E. Derbyshire (University of London,
UK), C. Deschamps (Universidad
Nacional de La Plata), E. Godoy (Santiago
de Chile), P. Imbellone (Universidad
Nacional de La Plata), C. Janis
(Brown University, USA), M. Kaplan
(Columbia University, USA), S.M. Kay
(Cornell University, USA), H.A. Leanza
(MACN, Buenos Aires), E. Llambías
(CIG, La Plata), T. Manera (Universidad
Nacional del Sur, Bahía Blanca), S. Martinez
(Universidad de la República, Uruguay),
G. McDonald (National Park Service,
USA), A. Mourgues (SERNAGEOMIN,
Chile), C.A. Mpodozis (Antofagasta
Minerals, Chile), D. Muhs (United
States Geological Survey, USA), S. Nielsen
(Christian-Albrechts-Universität, Germany),
O. Orfeo (Centro de Ecología
Aplicada del Litoral, Corrientes), E.G.
Ottone (Universidad de Buenos Aires), J.
Panza (SEGEMAR, Buenos Aires), R.N.
Page (SEGEMAR, Buenos Aires), G.
Pastorino (MACN, Buenos Aires), G.J.
Retallack (University of Oregon, USA),
P. Sruoga (SEGEMAR, Buenos Aires), J.
Stilwell (Monash University, Australia),
M. Suarez (SERNAGEOMIN, Chile), M.
Toledo (Muséum National d'Histoire
Naturelle, France) and G. Vucetich (Universidad
Nacional de La Plata).
WORKS CITED IN THE TEXT
1. Bowly, J. 1990. Charles Darwin, a new biography. Hutchinson Press, 511 p., London, Sydney, Auckland and Johannesburg.
2. Keynes, R.D. 2001. Charles Darwin's Beagle Diary. Cambridge Univesity Press. 464 p., Cambridge.
3. Sowerby, G.B. II 1846. Descriptions of the Tertiary fossil shells from South America. In Darwin, C. Geological observations on South America. Being the third part of the geology of the voyage of the Beagle, under the command of Capt. Fitzroy, R.N. during the years 1832 to 1836. Smith Elder and Co. Ed., Appendix: 249-264, London.