Kathleen M. Marsaglia

Compositional trends in arc-related, deep-marine sand and sandstone: A reassessment of magmatic-arc provenance

Detrital modes for 524 deep-marine sand and sandstone samples recovered on circum-Pacific, Caribbean, and Mediterranean legs of the Deep Sea Drilling Project and the Ocean Drilling Program form the basis for an actualistic model for arc-related provenance. This model refines the Dickinson and Suczek (1979) and Dickinson and others (1983) models and can be used to interpret the provenance/tectonic history of ancient arc-related sedimentary sequences. Four provenance groups are defined using QFL, QmKP, LmLvLs, and LvfLvmiLvl ternary plots of site means: (1) intraoceanic arc and remnant arc, (2) continental arc, (3) triple junction, and (4) strike-slip-continental arc. Intraoceanic- and remnant-arc sands are poor in quartz (mean QFL%Q 75); they are predominantly composed of plagioclase feldspar and volcanic lithic fragments. Continental-arc sand can be more quartzofeldspathic than the intraoceanic- and remnant-arc sand (mean QFL%Q values as much as 10, mean QFL%F values as much as 65, and mean QmKP%Qm as much as 20) and has more variable lithic populations, with minor metamorphic and sedimentary components. The triple-junction and strike-slip-continental groups compositionally overlap; both are more quartzofeldspathic than the other groups and show highly variable lithic proportions, but the strike-slip-continental group is more quartzose. Modal compositions of the triple junction group roughly correlate with the QFL transitional-arc field of Dickinson and others (1983), whereas the strike-slip-continental group approximately correlates with their dissected-arc field.

The Paleogeography of Paleozoic and Mesozoic Storm Depositional Systems

Present-day hurricane belts are confined to 5°-45° latitude along the western edges of oceans, whereas winter storms occur ubiquitously above 25° latitude. Both hurricanes and winter storms occur between 25° and 45° latitude in some areas. Storm zones can be identified on global paleogeographic maps with the assumption that this latitudinal zonation of storm systems existed in the geological past. Evaluation of 69 previously-recognized Paleozoic and Mesozoic storm depositional systems on such maps showed that only 70% of them occur in ancient hurricane, mixed hurricane and winter storm, and winter storm belts. The remainder occur on the western sides of continents and/or at low paleolatitudes, and therefore well may be of different origin. Mesozoic storm depositional systems containing hummocky stratification tend to occur in counterpart paleo-winter storm belts, whereas hummocky stratification in suggested Paleozoic examples occur in both winter storm and hurricane belts and in paleolatitudes where we infer storm activity did not occur.

Late Cretaceous–early Cenozoic tectonic evolution of the southern California margin inferred from provenance of trench and forearc sediments

During the Late Cretaceous to early Cenozoic, southern California was impacted by two anomalous tectonic events: (1) underplating of the oceanic Pelona-Orocopia-Rand schists beneath North American arc crust and craton; and (2) removal of the western margin of the arc and inner part of the forearc basin along the Nacimiento fault. The Pelona-Orocopia-Rand schists crop out along a belt extending from the southern Sierra Nevada to southwestern Arizona. Protolith and emplacement ages decrease from >90 Ma in the northwest to <60 Ma in the southeast. Detrital zircon U-Pb ages imply that metasandstones in the older schists originated primarily from the western belt of the Sierran–Peninsular Ranges arc. Younger units were apparently derived by erosion of progressively more inboard regions, including the southwestern edge of the North American craton. The oldest Pelona-OrocopiaRand schists overlap in age and provenance with the youngest part of the Catalina Schist of the southern California inner continental borderland, suggesting that the two units are broadly correlative. The Pelona-OrocopiaRand-Catalina schists, in turn, share a common provenance with forearc sequences of southern California and the associated Salinian and Nacimiento blocks of the central Coast Ranges. This observation is most readily explained if the schists were derived from trench sediments complementary to the forearc basin. The schists and forearc units are inferred to record an evolution from normal subduction prior to the early Late Cretaceous to flsubduction extending into the early Cenozoic. The transition from outboard to inboard sediment sources appears to have coincided with removal of arc and forearc terranes along the Nacimiento fault, which most likely involved either thrusting or sinistral strike slip. The strike-slip interpretation has not been widely accepted but can be understood in terms of tectonic escape driven by subduction of an aseismic ridge, and it provides a compelling explanation for the progressively younger ages of the PelonaOrocopia-Rand schists from northwest to southeast.

Explosive deep water basalt in the sumisu backarc rift.

Eruption of 1-million-year-old tholeiitic basalt >1800 meters below sea level (>18 megapascals) in a backarc rift behind the Bonin arc produced a scoriaceous breccia similar in some respects to that formed during subaerial eruptions. Explosion of the magma is thought to have produced frothy agglutinate which welded either on the sea floor or in a submarine eruption column. The resulting 135-meter-thick pyroclastic deposit has paleomagnetic inclinations that are random at a scale of <2.5 meters. High magmatic water content, which is about 1.3 percent by weight after vesiculation, contributed to the explosivity.

Tectonic history of a Jurassic backarc-basin sequence (the Gran Canon Formation, Cedros Island, Mexico), based on compositional modes of tuffaceous deposits

The Jurassic Gran Canon Formation (Cedros Island, Baja California, Mexico) constitutes an unusually well preserved and exposed example of ancient backarc-basin fill. Petrofacies analysis conducted on tuff- aceous sandstone and tuff samples from this formation complement and reinforce prior lithofacies interpretations, but with some modification. When temporal and spatial trends in petrographic data (detrital modes) are analyzed and compared to mod- els based on data collected from Deep Sea Drilling Project and Ocean Drilling Pro- gram cores, the trends indicate a second, heretofore unrecognized, phase of backarc rifting. Basalt lavas interstratified with da- citic pyroclastic rocks of the primary vol- canic lithofacies, previously interpreted to record the eruption of differentiated mag- mas at the climax of growth of the Gran Canon island arc, are now as a result of this study considered to be the product of arc extension and rifting. Our method of modal analysis uniquely combines the quantification of textural at- tributes of pyroclastic and epiclastic debris that reflect eruption style and magma com- position, as well as the effects of reworking and mixing in marine settings. This study demonstrates that detailed petrographic analysis is useful in the interpretation of ancient volcaniclastic deposits suspected of having formed in backarc-basin settings.

The Recycled Orogenic Sand Provenance from An Uplifted Thrust Belt, Betic Cordillera, Southern Spain

The Betic Cordillera of southern Spain represents an uplifted foreland fold–thrust belt. Source rock types of the Betic Cordillera include metamorphic (mainly phyllite, schist, quartzite, and gneiss), sedimentary (siliciclastic and carbonate), volcanic (felsic to intermediate pyroclasts), and mantle-derived (peridotite, gabbro, serpentinite, and serpentine schist) rocks. The fluvial systems range that transect the Betic Cordillera are the major detrital source of sediment along the southern Spanish coast, supplying sand to beaches and offshore depositional systems in the Alboran Sea basin. Three key sand petrofacies derived from the Betic mountain belt reflect the main clastic contribution of known source rocks. All the sands are quartzolithic, ranging from quartz-rich to lithic-rich. Fluvial systems draining the Sierra de Los Filabres, the Sierra Nevada, the Sierra de Gador, and the Ma´laga Mountains, and their related beaches constitute a metamorphic–sedimenticlastic quartzolithic sand petrofacies (Qm34610 F463 Lt6269; Lm72614 Lv264 Ls26613), derived dominantly from the Nevado–Fila´bride, Alpuja´rride, and Mala´guide complexes. This quartzolithic petrofacies extends from northeast of Almeria to Torremolinos (southwest of Ma´laga), and northeast of Algeciras. Only one beach sand sample, east of Cabo de Gata, is volcanolithic. Volcanic detritus (mainly having felsitic textures) is derived from Miocene (15–7 Ma) pyroclastic sequences cropping out in the southeast of the chain. This metamorphic–sedimenticlastic quartzolithic petrofacies changes in the coastal stretch from Torremolinos to Marbella, where drainage systems cut across the Serrania de Ronda. Here source rock types include peridotite, gabbro, and serpentinite of the Ronda Peridotite Massif, and metamorphic rocks of the Ma´laguide and Alpuja´rride units. The fluvial and beach sands of this area are quartzolithic (Qm32612 F1063 Lt58611), and include abundant peridotite and serpentinite grains. The latter quartzolithic petrofacies changes abruptly from Algeciras to Ca´diz, where the sand becomes quartz-rich (Qm7765 F462 Lt1964). This sand petrofacies is derived predominantly from recycling of sedimentary sequences, mainly the quartzarenite turbidite units of the Gibraltar Arc (the Algeciras Flysch). This petrofacies is characterized by higher proportion of quartz grains and abundant sedimentary lithic fragments (Lm163 Lv161 Ls9863). The three onshore petrofacies plot in the recycled-orogen provenance compositional field and the lithic to transitional to quartzose recycled subfields of Dickinson (1985). They vary from lithic, to transitional and quartzose depending on their source lithologies in the Betic foreland fold–thrust belt. These actualistic petrofacies best describe the nature and distribution of sand petrofacies derived from a collisional fold–thrust belt where primary and recycled source rocks are interfingered. Deep-marine turbidites of the Alboran Basin have basinwide quartzolithic sands having close compositional relations with Betic Cordillera onshore sand petrofacies. Comparison of detrital modes from mainland to deep-marine environments provides a suitable basis for interpreting the Miocene to Pleistocene sand dispersal history in the Alboran Basin. These modern quartzolithic petrofacies are used to interpret analogous ancient collisional sandstone petrofacies of the Alpine orogenic belt of the western-central Mediterranean region and of other collisional orogenic systems, as a broader point of view.

Tectonic evolution of the Japanese islands as reflected in modal compositions of Cenozoic forearc and backarc sand and sandstone

Cenozoic tectonic evolution of the Japanese rifted continental arc-trench system is reflected in the detrital modes of sand and sandstone deposited in forearc and backarc basins sampled by the Deep Sea Drilling Project. At present, the Japan arc is divided into two segments along a complex plate boundary where the Izu-Bonin Ridge intersects the Japan arc, creating two triple junctions, in front of and behind the ridge. Southwest of the Izu-Bonin Ridge, quartzofeldspathic Cretaceous forearc sediments were uplifted and recycled into Tertiary forearc deposits in response to strike-slip movement associated with backarc spreading in the Shikoku basin. Quaternary forearc sections record the first major influx of volcanic detritus to southwest Japan sites. Triple-junction-related deformation in central Honshu has produced sand of mixed volcanic/sedimentary provenance, which is funneled by the Suruga Canyon into the Nankai Trough along the southwest Japan margin. North of the triple junction, Oligo-Miocene forearc sand compositions indicate Oligocene forearc uplift and volcanism, possibly related to initial backarc rifting and formation of the Japan Sea, and subsequent Miocene exposure of arc basement. In contrast, Pliocene and Quaternary forearc sand from northeast Japan is primarily volcaniclastic and documents uninterrupted arc volcanism. Within the backarc region, sand compositions vary from east to west across the Japan Sea. The Asian rifted continental margin and submerged remnants shed quartzofeldspathic sand into the western side of the basin, whereas the Japan arc sheds volcaniclastic sand into the eastern side of the basin.

Precolumbian Settlements on Carriacou, West Indies

Abstract The first systematic archaeological investigation of Precolumbian sites on the island of Carriacou in the West Indies provides a rich source of information regarding Amerindian settlement in the southern Caribbean. Herein, we report results from an island-wide survey and subsequent excavation at two large village sites—Grand Bay and Sabazan—that provide evidence for an intensive late Ceramic Age occupation dating between CAL. A.D. 400–1200. Results from four seasons of excavation at Grand Bay and two at Sabazan indicate that inhabitants colonized the island later than larger nearby islands (although an earlier settlement is possible); were engaged in inter-island and South American interactions as evidenced through analysis of pottery, stylistic artifacts, and faunal remains; exploited a variety of marine and terrestrial foods, including several animals rarely found in the Antilles that were translocated to the island from elsewhere; and buried their dead in and around shell middens and, at least once, under a habitable structure.

Depositional History of the Middle Proterozoic Castner Marble and Basal Mundy Breccia, Franklin Mountains, West Texas

ABSTRACT The ca. 1260 Ma Castner Marble is composed of six metamorphosed lithologies: stromatolitic limestone, cryptalgalaminite, massive limestone, hornfels (mudstone and tuff), rhythmite, and flat-pebble conglomerate. On the basis of the associations of these lithologies, the Castner Marble can be divided into three distinct intervals: a lower section containing stromatolitic and cryptalgalaminite units, a middle section with thick hornfels and massive limestone beds, and an upper section of rhythmites (interlaminated to thinly interbedded carbonate and hornfels) with interbedded flat-pebble conglomerate. The Castner succession was deposited during a transgressive event on a low-energy carbonate ramp. The contact between the Castner Marble and the overlying basaltic Mundy Breccia marks a catastrophic event or series of events, in which rhythmite units were disrupted and/or displaced along arcuate detachment surfaces and redeposited as lenses of rhythmite megabreccia unconformably overlying intact rhythmite sequences. These megabreccia lenses consist of large, locally deformed rhythmite blocks in a matrix of muddy flat-pebble conglomerate. One megabreccia lens contains intervals bearing irregular-shaped basalt clasts possible hyaloclastite layers, and pod-like basalt intrusions. This polymictic lens may have been produced by submarine syn-eruptive mixing of basalt and sediment. Local basalt intrusions may be part of the feeder system for this material and also the overlying basaltic Mundy Breccia. The Mundy Breccia covered the irregular topography created by the megabreccia lenses, locally loading and deforming the megabreccia into flame-like structures. The polymictic (carbonate and basalt) nature of one lens and presence of load features suggests that little time elapsed between deposition of the Castner Marble and the Mundy Breccia, and therefore that the Mundy Breccia was most likely deposited in a submarine setting.

Sandstone detrital modes support Magdalena Fan displacement from the mouth of the Gulf of California

Detrital modes of middle Miocene sandstone recovered at Deep Sea Drilling Project Site 471 on the Magdalena Fan support the hypothesis that the fan has been displaced northward from a source hundreds of kilometers to the south near the present mouth of the Gulf of California. The modes are dissimilar to those of modern sand derived from onshore outcrops of Miocene volcanic and volcaniclastic rocks, Neogene sedimentary rocks, and Mesozoic subduction complex. They most closely match sand associated with the mouth of Gulf of California. The overall stratigraphy, sand composition, and diagenesis at Site 471 are consistent with deposition of the Magdalena Fan on young oceanic crust near a spreading ridge at a triple junction.