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| Titel |
Oceanic terranes of S-Central America - 200 Million years of accretion history recorded on the W-edge of the Caribbean Plate. |
| VerfasserIn |
P. O. Baumgartner, K. Flores, A. Bandini, D. Buchs, G. Andjic, C. Baumgartner-Mora |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250059969
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| Zusammenfassung |
| The W-edge of the Caribbean Plate is characterized by two major basement domains,
separated today by a SW-NE trending diffuse fault zone located SE of the Nicoya Peninsula
(Costa Rica) and possibly connecting with the Hess Escarpment. To the NW, in the area
originally called “Chortis Block”, oceanic island/arc basements range in age from Late
Triassic to Early Cretaceous and form a complicated puzzle of geodynamic units. To the SE
of this fault line, no age older than Turonian-Santonian (90-85 Ma) is known. This
area only represents the trailing edge of the Caribbean Large Igensous Procince
(CLIP).
The Mesquito Composite Oceanic Terrane (MCOT) comprises the southern half of the
“Chortis Block”, classically considered as a continental fragment of N-America. The MCOT
is defined by isolated outcrops of ultramafic, mafic oceanic/arc rocks, and radiolarites of Late
Triassic, Jurassic and Early Cretaceous age: Rhaetian (latest Triassic) radiolarites
found in the El Castillo Mélange (S-MCOT: S-Nicaragua/N- Costa Rica). They are
associated with blocks of OIB-metabasalts. These rocks document the presence of a Late
Triassic oceanic basement that must have been the substrate of the 174 -177 Ma old
(Early/Middle Jurassic) Petit-Spot-like alkaline volcanics that intruded Early Jurassic
radiolarites. These rocks form tectonic slivers in the middle Cretaceous Santa Rosa
Accretionary Complex (relative autochthonous of the Santa Elena ultramafic unit, N-Costa
Rica).
The oldest rocks of the Nicoya Complex s. str. (NW-Nicoya Peninsula, Costa Rica) are
Bajocian (Middle Jurassic) radiolarites, that occur as blocks magmatically engulfed in
plateau-type basalts and intrusives that range in age thoughout the pre-Campanian Cretaceous
(130-83 Ma).
Middle and Late Jurassic metaradiolarites occur as blocks in the Siuna Serpentinite
Médange (NE-Nicaragua), along with High-p, arc-related mafics. We envision an oceanic arc
that collided in the latest Jurassic with the Agua Fria arc system (Chortis Block
s. str.), and became exhumed again by the earliest Cretaceous (139 Ma phengite
age).
A pre-Albian basaltic plateau-like basement is suspected but yet undated in the Matambú
Terrane (Central Nicoya Peninsula). It is overlain by the Albian Loma Chumico
Formation.
A pre-Turonian basement hosting the 90 Ma old Tortugal Picrites and alkaline baselts
characterizes the Manzanillo Terrane ( around the Nicoya Gulf, Costa Rica). The overlying
Coniacian-Santonian to early Campanian Berrugate Formation represents the first Cretaceous
evolved arc activity. It must be located on the edge of the MCOT, since the CLIP is still
forming at that time.
To the SE of the S-Nicoya fault zone, Turonian-Santonian (~90-85 Ma) oceanic plateaus
represent outcrops of the CLIP. These include parts of Herradura (Costa Rica) and the Azuero
Plateau (Coiba, Sona and Azuero, Panama).
Late Campanian to Paleocene arcs rest on the CLIP: The Golfito Complex (Costa Rica)
and the Azuero Arc (Panama), possibly also the San Blas Complex (Panama) and the Serrania
de Baudo (W-Colombia).
Late Cretaceous to Eocene plateau/seamount basalts and oceanic sediments became
accreted during the Early Tertiary: The Tulin Group (Herradura), Quepos, The Osa Igneous
Complex, Burica, the Osa Mélange (Costa Rica/Panama), and the Azuero Accretionary
Complex (Panama). |
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