CSU LogoGeologyCalifornia State University - Stanislaus

Controls on Chortis Block Landform Evolution

by Rob Rogers - prepared in 2001

 

Physical Setting of Northern Central America
Chortis Block of northwest Caribbean Plate
Click to enlarge
Cocos Plate subducts below Caribbean Plate
  • Middle American Trench
  • Volcanic Arc
  • Earthquakes
North American - Caribbean Plate margin
  • Strike-Slip (left lateral)
  • Earthquakes

Physical setting of northern 
Central America

 
 
Landform reflecting current tectonic processes
Feature Description Origin Age of Landform Image - Click to enlarge
Volcanic Arc  Middle American Trench (MAT) parallel volcanic landforms of Guatemala, El Salvador, and Nicaragua  Cocos Plate subduction beneath Caribbean Plate Pliocene (?) to Recent 
Chortis landforms reflecting present tectonic setting
Median-Nicaragua Back-Arc basin 800 km long structural basin and topographic low behind and parallel to MAT and volcanic arc from Salvador to Nicaragua  Active extension 
  • subducted Cocos slab roll-back?
  • MAT not keeping pace with eastward movement of  Caribbean Plate?
Late Neogene (?) to Recent See above image 
North-south trending ranges and valleys of western Chortis  Normal and strike-slip fault bounded valleys and ranges west of Honduras Depression and north of back-arc. Caribbean-North American Plate interaction across a diffuse margin. 

Allowed by post-10 Ma deceleration of convergence between  South America and North America.  

Late Neogene to Recent See above image

 
 
Landforms Reflecting Crustal Properties of Chortis Block
Feature Description Origin  Age of landform Image - Click to enlarge
Elevated topographic/ bathymetric portion of Chortis Block  All of Chortis block north of Median Nicaragua back-arc Unknown. 

Possibly a buoyant response.  Implies lower crust - upper mantle involvement. 

 

Post - Middle Miocene.

Likely Late Neogene

Elevated
Elevated Portion of Chortis Block
West to East topographic/ bathymetric gradient.  Higher elevations to west, north of back-arc. Includes Eocene to recent sedimentation on Nicaragua Rise Crustal buoyancy variation across Chortis block
  • Continental crust west of GFS.
  • Transitional crust between GFS and Siuna, Nicaragua
  • Oceanic Crust east of Siuna, Nicaragua
Age of Crust
 
  • Pre-Jurassic 
  • Jurassic 
  • Cretaceous

Cross-Chortis Block Elevation Gradient

 

Crustal Types of Northern Central America

 
 
 
 
Antecedent Landform Reflecting Paleotectonic Processes and Differential Weathering of Rocks and Structures 
Feature Description Origin Age of landform Image - Click to enlarge 
Patuca-Coco anticlinorium (pre-Coco-Patuca rivers) Topographic feature that separated alluvial Patuca and Coco rivers prior to entrenchment Exposure and differential weathering of Montana de Colon fold-thrust belt Paleocene (?)
Northeast Flowing Rivers of Eastern Chortis Block
Northeast flowing meandering bedrock rivers of eastern Chortis block Largest rivers on Chortis block (Patuca and Coco)  flow down topographic axis of Chortis block. River positions are pinned in place by uplift (see below).  River positions have NOT changed with  eastward movement of Chortis block. May reflect   Maya block position to north. Miocene (?) See above image
Highlands of Chortis Block  Ranges and relatively high valleys (overprinted to west by extension) north of back-arc .
Includes meandering bedrock  rivers, water and wind gaps, and dissected erosion surfaces.
Differential weathering of rocks and structures subjected to epeirogenic uplift.  Erosion accentuating lithologic differences and fault systems. Post-Middle Miocene Padre Miguel Group. 

Probably late Neogene.


Areas Displaying Evidence of Epeirogenic Uplift
Bedrock Meanders and Canyons "Boqueron" Fluvial meanders entrenched >300 meters into bedrock. Contiguous in east, disrupted in west. Epeirogenic uplift of Chortis block entrenched fluvial meanders.  Post-Middle Miocene Padre Miguel Group. 

Probably late Neogene.
 

 


Meandering Bedrock Rivers
Fault bounded valleys of the Guayape Fault System (GFS) Jamastran, Azucaulapa, Catacamas, Culmi, and Paulaya valleys.
 
Pull-apart basins associated with right slip on GFS.  Jamastran pull-apart contains valley fill of Padre Miguel clasts. (see below) Middle Miocene - Padre Miguel Group time

Probably ended prior to back-arc development.

 


Guayape Fault System
Alignment of rivers along GFS Guayambre, Guayape, Tinto, Pataste, Paulaya Rivers Erosion of sheared rock along GFS. Post-Tpm. Probably late Neogene and post epeirogenic uplift  See above image
Cross-GFS topographic gradient Average elevation is 1000 meters higher to NW of GFS Up to northwest movement associated with right slip on GFS Miocene
Cross-GFS Gradient
Distribution of rock age across Guayape Fault Younger rocks on the topographically higher NW side and older rocks on SE side.
(note: area not colored in image are pre-Cretaceous age.  Coverage is only for Honduras)
Earlier motion on GFS involved up to SE movement and erosion of pre-Cretaceous strata.  Unknown
Rock Age Distribution Across GFS
Valle de Jamastran - Southern Extent of GFS Structural basin filled with clasts of eroded Padre Miguel tuff.  Volcanic center at southern margin of basin. Danli volcanic center buries southern extent of pull-apart basin.  SW source of valley filling Padre Miguel tuff blocked by volcano.  Volcano not significantly affected by GFS. Valley - Post Middle Miocene Padre Miguel Group

Danli volcanic center - Pliocene (?) 


Guayape Fault System at Valle de Jamastran