GEOLOGICAL FRAMEWORK :
Within leaf Chepén Jequetepeque River Basin studied by J. Wilson and L Reyes is located. Land are excluded from the Lower Paleozoic affected by three phases of deformation, Mesozoic and Cenozoic to , and quaternary materials filling some basins and valleys.
Regarding the structure of the area should be noted that there are up to two recognized Structural Provinces:
TECTONICS PACASMAYO Province :
Within this province the phyllites of Training Facilities are located, in the Middle Paleozoic orogenizadas a course NE - SW and later in the Late Paleozoic , giving a direction NNE - SSW .
In the Mesozoic and Cenozoic within the Teutonic Province Pacasmayo the next phases of movement is recognized :
Folding formations in southern sector features a WNW direction - ESE, near the terminal Cretaceous Tectonics lifting Pacasmayo Province late Cretaceous , followed by erosion of the Cretaceous formations and deposition of volcanic and volcanic Calipuy Group Call , Tectonics lifting Pacasmayo Province in the Early Tertiary, followed by deposition of volcanic Porculla and minor movements.
TECTONICA CHIMU Province :
This province consists of a folded belt of Mesozoic rocks (Group Gollarisquizga , Chulec , Paraitambo , Groups Pulluciana , Quilquiñan Cajamarca Formation and Training ), with a general direction WNW - ESE.
In the lower part of the valley are filíticas tuffaceous rocks and the formation Salas possible Ordovician age ( Paleozoic ) . Later in the Neocomian - Aptian shales, sandstones and some limestones are grouped into the Chimú , Santa , and Farrat Carhuaz Formations were deposited . The Albian is represented by a limestone sequence that meets the Inca Formations, Chulec, and part of Pulluicana Pariatambo (East).
On this basis lies a package of limestones and marls , formed by Pulluicana Groups, Quilquiñan ( shales ) and Cajamarca Formation, Turonian ( Upper Cretaceous ), noting this, the culmination of the Cretaceous marine sedimentation in this area.
Removal of the terminal Cretaceous led to the formation of conglomeratic deposits accumulation of Chota Formation (outcropping only in some sectors of the basin). On this , the accumulated volcanic series - clastic (Andesite, tuff, sandstone, agglomerates, shales , tuffaceous , etc.) of Calipuy Group (Volcanic Flame : J. Wilson) ; unconformably covered by Volcanic Porculla (dacites and andesites) which infrayacen in the same relation to acid tuffs of Tertiary Training Huambos.
As a byproduct of glaciation Plio - Pleistocene accumulated by river action in the lower parts , a series of fluvial material - glacial deposits and the innumerable loopholes that have progressively desaguándose. Finally along the coastal belt of the Andean foothills and abundant alluvial and fluvial deposits ; being located in the coastal line sand irregular mantles of wind .
According to the sheet Chepén in the area is located in the Andean foothills , forming the litho- stratigraphic units comprising a range between Lower Paleozoic (Salas Training) until the recent Quaternary.
PALEOZOIC BELOW :
Training Salas ( Pi - s ) : outcrops in the coastal area of ??the quadrangles and Chepén Pacasmayo . Consisting of a sequence of metamorphic rocks ( phyllite , tuffaceous , quartzites and conglomerates) , or rolled into thin layers , forming low hills and desectados . It is common to see streaks of milky quartz . Is estimated to be about 1,000 feet thick at most.
CRETACEOUS :
Goyllarisquizga Group (K - g ) crops out in nearly all Jequetepeque River Basin distinguishing the following formations .
- Chimu (- Chin Ki ) Training
- Training St. ( Ki - Sa )
- Carhuaz (- ca Ki ) Training
- Farrat (- f Ki ) Training
- Inca Formation (K - i )
- Training Chulec ( m - ch)
- Training Pariatambo ( m - p )
- Pulluicana Group ( m - p )
- Yumagual Formation (Km -ym )
- Training Mujarrún ( Ks -mp )
- Quilquiñan Group ( Ks - q )
- Cajamarca (- ca Ks ) Training
TERTIARY :
Calipuy Group (Ti - cp ): Found throughout the central part of the basin that is east of the Quadrangle Chepén and NW Quadrangle of Cajamarca. Is a product of volcanism post - tectonic and represents the effusive magmatism that followed the final location of the coastal batholith . This Group is divided into:
Quadrangle Chepén :
- Training Call ( Ti - rg )
- Porculla (- vp Ti) Training
Quadrangle Cajamarca:
- Scrapie (- vt Ti) Training
- Chilete (- vch Ti) Training
- San Pablo Formation (Ti - vsp )
Quaternary :
- moraine deposits.
- Deposits Fulvio - glaciers.
- Alluvial and Fluvial Deposits.
- colluvial deposits.
- Deposits Proluviales.
- Deposits Wind
INTRUSIVE ROCKS :
Are mainly located in the western part of the basin in the Andean valley of Chepén Quadrangle , with ages ranging from Cretaceous to Lower Tertiary .
- granodiorite - tonalite
- Diorites.
lithologic MAP
Lithologic units existing in the vicinity of Quadrangle Chepén , should know their petrographic composition , degree of weathering , situation , fracturing , geomechanics classification, etc. . , Which affect their geotechnical behavior.
The lithological units have been subdivided into two groups: The Surface unit comprising quaternary material : Alluvial artificial fillers ( terraces) , colluvial , aeolian and Rocky Substrate materials unit comprising Paleozoic , Cretaceous , and Tertiary intrusive rocks
SURFACE UNITS :
This includes materials of recent age, belonging to the Quaternary unconsolidated , generally flat and near watercourses morphology; latter two features have caused major human settlements are located on these materials also have higher geodynamic and geotechnical problems .
In the basin have been located up to 8 subunits.
Ifg Unit: Deposits Fulvio - glaciers - These deposits are mainly located at the N -NE of the basin on the dimension 3500 and consist of chants and clayey silt - sand- gravel sub - angular matrix of heterometry grain , moderately to well-established , low to medium permeability. Stable in areas of gentle slopes.
Imo drive. Moraine deposits - are located in the Pampa de Huancarume , and Pampa Lagunas Dried Lily NE of the basin. They consist of : bowling, subangular gravel and silt - matrix edges with sandy- clayey , anisotropic , heterometric grain , low permeability , compact , stable .
Unit Ia . Alluvial Deposits - Located at its greatest extent, in the alluvial fan Jequetepeque River, are generally formed by: bowling, pebbles and gravel rounded to subrounded , variable power , moderately to well consolidated with sandy- silty matrix locally silty sandy lenses, medium to high permeability , natural slopes under 10 ° are presented . Generally stable , there may be problems in earthquakes , flooding and groundwater upwelling Napa. They are also located on the banks of rivers in forms of terraces , where they are less consolidated .
If drive. Fluvial Deposits - These deposits are located in the greater or Flood Jequetepeque River bed are lithologically composed of bowling , singing and subrounded gravels in a silty sandy matrix of variable grain size , unconsolidated , high-permeability sandy and susceptible to flooding presence lenses.
Ic Unit: colluvial deposits - is fragmented and partially decomposed by weathering , deposited in depressions and obstacles on the slopes and in the foothills deposits. Lithologically formed by: bowling , singing and angular gravel in a sandy- silty matrix heterometric little compact, medium to high permeability . Deposits in the process of formation and drag , can have different degrees of mobility, being able to present phenomena crawling on top or be unstable in the presence of water.
Unit Ip. Proluviales Deposits - This is a mixture of bowling (usually large ) , songs and angular sub- angular gravels in a sandy- silty matrix. These deposits are usually located at the mouth of the creeks and gullies.
They are heterometric grain , medium to fine compact , natural slopes under 12 ° medium to high permeability . Stable , except in areas close to landslides.
Ie drive. Deposits Wind - Located in the coastal dunes and dunes forming pampa . Sands are fine to medium grained , not consolidated , high permeability. Subject to liquefaction phenomena by dynamic effects and differential settlements of earthquakes ; in areas where the water table is shallow, sanding phenomena.
Im Unit: Marine Deposits - Located on the coast edge, small size , mythologically formed by medium-grained sand to fine subrounded gravel and pebbles, with lenses of fine sand to medium, presence of salts. Areas affected by waves and tides.
Substrates:
The Sub lithologic units that make up this unit are described.
UNIT II : VOLCANIC ROCKS
Sub -Unit IITB. Toba - are mainly dacitic tuffs and breccias, containing fragments of pumice , well stratified medium partially compact layers thick , with a maximum thickness of 400 m . These tuffs are porphyritic , porous medium to high permeability, low resistance to very low ( 1000 kg/cm2) , more or less stable natural slopes , cut slopes somewhat unstable . Exhibit high mechanical , moderately fractured little altered resistance. In sectors where they are interbedded shales , decrease their geomechanical conditions .
UNIT V : ROCKS INTRUSIVE
Is primarily located east of the basin ( mid valley ) belong to Costanero Batholith , topography have a moderate to very steep (slope 20 º - 55 º) generally rounded edges. Rocks are generally massive , moderately by little altered , fractured , its permeability are dependent on the degree to fracturing, high strength (> 1000 kg/cm2). Stable natural slopes , cut slopes unstable due to loose blocks on time caused by the intersection of fractures and sheared zones possible . These intrusive granodioritic - tonalitic are lithology ( V gd ) equigranular whitish gray. Adjacent to these, in the east , porphyritic andesite bodies ( V n) are located. SE of the basin are of dioritic - tonalitic lithology ( V di ) are light gray equigranular , medium to very altered , fractured.
UNIT VI : ROCKS METAMORPHIC
These policies and tuffaceous phyllite , or rolled into thin layers, interspersed with some outcrops deformed conglomerates with irregular veins of milky quartz , some up to 1 m . wide and 100 m . long. Are presented , forming low hills and dissected , sporadically in low , moderately altered altered, foliated and fractured , medium strength at low ( 280-500 kg/cm2) Jequetepeque River basin.
b) Local Geology
The mining concession area corresponds to erathem SAGIDE MESOZOIC , System CRETACEOUS LOWER Series Goyllarisquizga Group ( Ki- g ) , INCA Education (K -i ) this formation is sandstone and limestone interbedded with ferruginous lulitas and beds of quartzite outcrops altered with a reddish color that is characteristic of this formation thickness does not exceed 100 meters and has a steep topography and is consistent with the formation Chulet.Edad Middle Cretaceous.
The deposits consist of several lenticular veins emplaced in shales are 100 to 200 meters long and widths ranging from 2.0 to 6.0 meters , some veins appear cloaks on their compliance with schist crystalline structure trigonal , rhombohedral , is an accessory mineral numerous igneous rocks especially lavas, is also found as sublimation product in volcanic exhalation, belongs to :
Quad : Chepén
Erathem : Mesozoic
System : Cretaceous
Series: Lower
Floor: Aptian Negopmiano
Lithostratigraphic unit : Family Goyllarisquizga ( Ki- g )
The main MENA is Hematite , which reaches 70 % concentration of Fe3O , rare mineral in Intrusive rocks, but is common in extrusive because it requires an oxidizing environment. Exhibitions or outcrops belonging to the Inca ( Ki -i ) Training.
